Detailed Description
template<typename T>
class drake::multibody::MultibodyPlant< T >
MultibodyPlant is a Drake system framework representation (see systems::System) for the model of a physical system consisting of a collection of interconnected bodies.
See Multibody Kinematics and Dynamics for an overview of concepts/notation.
MultibodyPlant provides a user-facing API to:
- add bodies, joints, force elements, and constraints,
- register geometries to a provided SceneGraph instance,
- create and manipulate its Context,
- perform Context-dependent computational queries.
System dynamics
positions vector q, of size nq (see num_positions()), and by its generalized velocities vector v, of size nv (see num_velocities()). As a Drake System, MultibodyPlant implements the governing equations for a multibody dynamical system in the form ẋ = f(t, x, u) with t being the time and u the input vector of actuation forces. The governing equations for the dynamics of a multibody system modeled with MultibodyPlant are [Featherstone 2008, Jain 2010]:
q̇ = N(q)v
(1) M(q)v̇ + C(q, v)v = tau
where M(q) is the mass matrix of the multibody system, C(q, v)v corresponds to the bias term containing Coriolis and gyroscopic effects and N(q) is the kinematic coupling matrix describing the relationship between the rate of change of the generalized coordinates and the generalized velocities, [Seth 2010]. N(q) is an nq x nv matrix. The vector tau ∈ ℝⁿᵛ on the right hand side of Eq. (1) corresponds to generalized forces applied on the system. These can include externally applied body forces, constraint forces, and contact forces.
Loading models from SDF files
Drake has the capability of loading multibody models from SDF and URDF files. Consider the example below which loads an acrobot model:
As in the example above, for models including visual geometry, collision geometry or both, the user must specify a SceneGraph for geometry handling. You can find a full example of the LQR controlled acrobot in examples/multibody/acrobot/run_lqr.cc.
AddModelFromFile() can be invoked multiple times on the same plant in order to load multiple model instances. Other methods are available on Parser such as AddAllModelsFromFile() which allows creating model instances per each <model> tag found in the file. Please refer to each of these methods' documentation for further details.
Adding modeling elements
methods:
- Bodies: AddRigidBody().
- Joints: AddJoint().
All modeling elements must be added pre-finalize.
Registering geometry with a SceneGraph
MultibodyPlant users can register geometry with a SceneGraph for essentially two purposes; a) visualization and, b) contact modeling.Before any geometry registration takes place, a user must first make a call to RegisterAsSourceForSceneGraph() in order to register the MultibodyPlant as a client of a SceneGraph instance, point at which the plant will have assigned a valid geometry::SourceId. At Finalize(), MultibodyPlant will declare input/output ports as appropriate to communicate with the SceneGraph instance on which registrations took place. All geometry registration must be performed pre-finalize.
If MultibodyPlant registers geometry with a SceneGraph via calls to RegisterCollisionGeometry(), an input port for geometric queries will be declared at Finalize() time, see get_geometry_query_input_port(). Users must connect this input port to the output port for geometric queries of the SceneGraph used for registration, which can be obtained with SceneGraph::get_query_output_port(). In summary, if MultibodyPlant registers collision geometry, the setup process will include:
- Call to RegisterAsSourceForSceneGraph().
- Calls to RegisterCollisionGeometry(), as many as needed.
- Call to Finalize(), user is done specifying the model.
- Connect SceneGraph::get_query_output_port() to get_geometry_query_input_port().
Refer to the documentation provided in each of the methods above for further details.
Modeling contact
Please refer to Contact Modeling in Drake for details on the available approximations, setup, and considerations for a multibody simulation with frictional contact.
Finalize() stage
Once the user is done adding modeling elements and registering geometry, a call to Finalize() must be performed. This call will:
- Build the underlying MultibodyTree topology, see MultibodyTree::Finalize() for details,
- declare the plant's state,
- declare the plant's input and output ports,
- declare input and output ports for communication with a SceneGraph.
References
- [Featherstone 2008] Featherstone, R., 2008. Rigid body dynamics algorithms. Springer.
- [Jain 2010] Jain, A., 2010. Robot and multibody dynamics: analysis and algorithms. Springer Science & Business Media.
- [Seth 2010] Seth, A., Sherman, M., Eastman, P. and Delp, S., 2010. Minimal formulation of joint motion for biomechanisms. Nonlinear dynamics, 62(1), pp.291-303.
- Template Parameters
-
T Must be one of drake's default scalar types.
#include <drake/multibody/plant/multibody_plant.h>
Public Member Functions | |
| MultibodyPlant (double time_step=0) | |
| Default constructor creates a plant with a single "world" body. More... | |
| template<typename U > | |
| MultibodyPlant (const MultibodyPlant< U > &other) | |
| Scalar-converting copy constructor. See System Scalar Conversion. More... | |
| int | num_frames () const |
| Returns the number of Frame objects in this model. More... | |
| int | num_bodies () const |
| Returns the number of bodies in the model, including the "world" body, which is always part of the model. More... | |
| int | num_joints () const |
| Returns the number of joints in the model. More... | |
| int | num_actuators () const |
| Returns the number of joint actuators in the model. More... | |
| int | num_force_elements () const |
| Returns the number of ForceElement objects. More... | |
| int | num_model_instances () const |
| Returns the number of model instances in the model. More... | |
| int | num_positions () const |
Returns the size of the generalized position vector q for this model. More... | |
| int | num_positions (ModelInstanceIndex model_instance) const |
Returns the size of the generalized position vector q for a specific model instance. More... | |
| int | num_velocities () const |
Returns the size of the generalized velocity vector v for this model. More... | |
| int | num_velocities (ModelInstanceIndex model_instance) const |
Returns the size of the generalized velocity vector v for a specific model instance. More... | |
| int | num_multibody_states () const |
Returns the size of the multibody system state vector x = [q; v]. More... | |
| int | num_actuated_dofs () const |
| Returns the total number of actuated degrees of freedom. More... | |
| int | num_actuated_dofs (ModelInstanceIndex model_instance) const |
| Returns the total number of actuated degrees of freedom for a specific model instance. More... | |
| void | SetPositionsAndVelocities (systems::Context< T > *context, const VectorX< T > &q_v) const |
| Sets all generalized positions and velocities from the given vector [q; v]. More... | |
| void | SetPositionsAndVelocities (systems::Context< T > *context, ModelInstanceIndex model_instance, const VectorX< T > &q_v) const |
| Sets generalized positions and velocities from the given vector [q; v] for the specified model instance. More... | |
| Eigen::VectorBlock< const VectorX< T > > | GetPositions (const systems::Context< T > &context) const |
| Returns a const vector reference containing the vector of generalized positions. More... | |
| VectorX< T > | GetPositions (const systems::Context< T > &context, ModelInstanceIndex model_instance) const |
Returns an vector containing the generalized positions (q) for the given model instance. More... | |
| Eigen::VectorBlock< VectorX< T > > | GetMutablePositions (systems::Context< T > *context) const |
| (Advanced) Returns a mutable vector reference containing the vector of generalized positions (see warning). More... | |
| Eigen::VectorBlock< VectorX< T > > | GetMutablePositions (const systems::Context< T > &context, systems::State< T > *state) const |
| (Advanced) Returns a mutable vector reference containing the vector of generalized positions (see warning). More... | |
| void | SetPositions (systems::Context< T > *context, const VectorX< T > &q) const |
| Sets all generalized positions from the given vector. More... | |
| void | SetPositions (systems::Context< T > *context, ModelInstanceIndex model_instance, const VectorX< T > &q_instance) const |
| Sets the positions for a particular model instance from the given vector. More... | |
| void | SetPositions (const systems::Context< T > &context, systems::State< T > *state, ModelInstanceIndex model_instance, const VectorX< T > &q_instance) const |
| Sets the positions for a particular model instance from the given vector. More... | |
| Eigen::VectorBlock< const VectorX< T > > | GetVelocities (const systems::Context< T > &context) const |
| Returns a const vector reference containing the generalized velocities. More... | |
| VectorX< T > | GetVelocities (const systems::Context< T > &context, ModelInstanceIndex model_instance) const |
Returns a vector containing the generalized velocities (v) for the given model instance. More... | |
| Eigen::VectorBlock< VectorX< T > > | GetMutableVelocities (const systems::Context< T > &context, systems::State< T > *state) const |
| (Advanced) Returns a mutable vector reference containing the vector of generalized velocities (see warning). More... | |
| Eigen::VectorBlock< VectorX< T > > | GetMutableVelocities (systems::Context< T > *context) const |
| See GetMutableVelocities() method above. More... | |
| void | SetVelocities (systems::Context< T > *context, const VectorX< T > &v) const |
| Sets all generalized velocities from the given vector. More... | |
| void | SetVelocities (const systems::Context< T > &context, systems::State< T > *state, ModelInstanceIndex model_instance, const VectorX< T > &v_instance) const |
| Sets the generalized velocities for a particular model instance from the given vector. More... | |
| void | SetVelocities (systems::Context< T > *context, ModelInstanceIndex model_instance, const VectorX< T > &v_instance) const |
| Sets the generalized velocities for a particular model instance from the given vector. More... | |
| MatrixX< T > | MakeActuationMatrix () const |
This method creates an actuation matrix B mapping a vector of actuation values u into generalized forces tau_u = B * u, where B is a matrix of size nv x nu with nu equal to num_actuators() and nv equal to num_velocities(). More... | |
| geometry::SourceId | RegisterAsSourceForSceneGraph (geometry::SceneGraph< T > *scene_graph) |
Registers this plant to serve as a source for an instance of SceneGraph. More... | |
| std::vector< const Body< T > * > | GetBodiesWeldedTo (const Body< T > &body) const |
Returns all bodies that are transitively welded, or rigidly affixed, to body, per these two definitions: More... | |
| const CoulombFriction< double > & | default_coulomb_friction (geometry::GeometryId id) const |
Returns the friction coefficients provided during geometry registration for the given geometry id. More... | |
| void | set_elastic_modulus (geometry::GeometryId id, double elastic_modulus) |
Specifies the elastic_modulus for a geometry identified by its id. More... | |
| bool | geometry_source_is_registered () const |
Returns true if this MultibodyPlant was registered with a SceneGraph. More... | |
| const Body< T > * | GetBodyFromFrameId (geometry::FrameId frame_id) const |
| Given a geometry frame identifier, returns a pointer to the body associated with that id (nullptr if there is no such body). More... | |
| optional< geometry::FrameId > | GetBodyFrameIdIfExists (BodyIndex body_index) const |
If the body with body_index has geometry registered with it, it returns the geometry::FrameId associated with it. More... | |
| geometry::FrameId | GetBodyFrameIdOrThrow (BodyIndex body_index) const |
If the body with body_index has geometry registered with it, it returns the geometry::FrameId associated with it. More... | |
| const systems::OutputPort< T > & | get_generalized_contact_forces_output_port (ModelInstanceIndex model_instance) const |
| Returns a constant reference to the output port of generalized contact forces for a specific model instance. More... | |
| const systems::OutputPort< T > & | get_contact_results_output_port () const |
| Returns a constant reference to the port that outputs ContactResults. More... | |
| const RigidBody< T > & | world_body () const |
| Returns a constant reference to the world body. More... | |
| const BodyFrame< T > & | world_frame () const |
| Returns a constant reference to the world frame. More... | |
| const Body< T > & | get_body (BodyIndex body_index) const |
Returns a constant reference to the body with unique index body_index. More... | |
| const Joint< T > & | get_joint (JointIndex joint_index) const |
Returns a constant reference to the joint with unique index joint_index. More... | |
| Joint< T > & | get_mutable_joint (JointIndex joint_index) |
Returns a mutable reference to the joint with unique index joint_index. More... | |
| const JointActuator< T > & | get_joint_actuator (JointActuatorIndex actuator_index) const |
Returns a constant reference to the joint actuator with unique index actuator_index. More... | |
| const Frame< T > & | get_frame (FrameIndex frame_index) const |
Returns a constant reference to the frame with unique index frame_index. More... | |
| const UniformGravityFieldElement< T > & | gravity_field () const |
| An accessor to the current gravity field. More... | |
| UniformGravityFieldElement< T > & | mutable_gravity_field () |
| A mutable accessor to the current gravity field. More... | |
| const std::string & | GetModelInstanceName (ModelInstanceIndex model_instance) const |
Returns the name of a model_instance. More... | |
| bool | is_finalized () const |
Returns true if this MultibodyPlant was finalized with a call to Finalize(). More... | |
| bool | IsAnchored (const Body< T > &body) const |
Returns true if body is anchored (i.e. More... | |
| void | Finalize () |
| This method must be called after all elements in the model (joints, bodies, force elements, constraints, etc.) are added and before any computations are performed. More... | |
| void | Finalize (geometry::SceneGraph< T > *scene_graph) |
| (Do not use.) This is a deprecated overload that takes a scene_graph argument. More... | |
| double | time_step () const |
The time step (or period) used to model this plant as a discrete system with periodic updates. More... | |
| const std::vector< geometry::PenetrationAsPointPair< T > > & | EvalPointPairPenetrations (const systems::Context< T > &context) const |
Evaluates all point pairs of contact for a given state of the model stored in context. More... | |
| void | SetDefaultState (const systems::Context< T > &context, systems::State< T > *state) const override |
Sets the state so that generalized positions and velocities are zero. More... | |
| void | SetRandomState (const systems::Context< T > &context, systems::State< T > *state, RandomGenerator *generator) const override |
| Assigns random values to all elements of the state, by drawing samples independently for each joint/floating-base (coming soon: and then solving a mathematical program to "project" these samples onto the registered system constraints). More... | |
Does not allow copy, move, or assignment | |
| MultibodyPlant (const MultibodyPlant &)=delete | |
| MultibodyPlant & | operator= (const MultibodyPlant &)=delete |
| MultibodyPlant (MultibodyPlant &&)=delete | |
| MultibodyPlant & | operator= (MultibodyPlant &&)=delete |
Position and velocity state component accessors and mutators. | |
Various methods for accessing and mutating | |
| Eigen::VectorBlock< const VectorX< T > > | GetPositionsAndVelocities (const systems::Context< T > &context) const |
Returns a const vector reference containing the vector [q; v] with q the vector of generalized positions and v the vector of generalized velocities. More... | |
| VectorX< T > | GetPositionsAndVelocities (const systems::Context< T > &context, ModelInstanceIndex model_instance) const |
Returns the vector [q; v] of the model with q the vector of generalized positions and v the vector of generalized velocities for model instance model_instance. More... | |
| Eigen::VectorBlock< VectorX< T > > | GetMutablePositionsAndVelocities (systems::Context< T > *context) const |
(Advanced) Returns a mutable vector containing the vector [q; v] of the model with q the vector of generalized positions and v the vector of generalized velocities (see warning). More... | |
Working with free bodies | |
A MultibodyPlant user adds sets of Body and Joint objects to At Finalize(), MultibodyPlant builds a mathematical representation of such system, consisting of a tree representation. In this representation each body is assigned a Mobilizer, which grants a certain number of degrees of freedom in accordance to the physical specification. In this regard, the modeling representation can be seen as a forest of tree structures each of which contains a single body at the root of the tree. This root body, if connected to the world with a floating mobilizer (that is, a mobilizer which grants 6-dofs), is labeled as a "floating body". A user can request the set of floating bodies with a call to GetFloatingBaseBodies(). Alternatively, a user can query whether a Body is floating or not with Body::is_floating(). For many applications, a user might need to work with indexes in the multibody state vector. For such applications, Body::floating_positions_start() and Body::floating_velocities_start() offer the additional level of introspection needed. | |
| std::unordered_set< BodyIndex > | GetFloatingBaseBodies () const |
| Returns the set of body indexes corresponding to the "floating bodies" in the model, in no particular order. More... | |
| math::RigidTransform< T > | GetFreeBodyPose (const systems::Context< T > &context, const Body< T > &body) const |
Gets the pose of a given body in the world frame W. More... | |
| void | SetFreeBodyPose (systems::Context< T > *context, const Body< T > &body, const math::RigidTransform< T > &X_WB) const |
Sets context to store the pose X_WB of a given body B in the world frame W. More... | |
| void | SetFreeBodyPose (const systems::Context< T > &context, systems::State< T > *state, const Body< T > &body, const math::RigidTransform< T > &X_WB) const |
Sets state to store the pose X_WB of a given body B in the world frame W, for a given context of this model. More... | |
| void | SetFreeBodySpatialVelocity (systems::Context< T > *context, const Body< T > &body, const SpatialVelocity< T > &V_WB) const |
Sets context to store the spatial velocity V_WB of a given body B in the world frame W. More... | |
| void | SetFreeBodySpatialVelocity (const systems::Context< T > &context, systems::State< T > *state, const Body< T > &body, const SpatialVelocity< T > &V_WB) const |
Sets state to store the spatial velocity V_WB of a given body B in the world frame W, for a given context of this model. More... | |
| void | SetFreeBodyRandomPositionDistribution (const Body< T > &body, const Vector3< symbolic::Expression > &position) |
Sets the distribution used by SetRandomState() to populate the x-y-z position component of the floating-base state. More... | |
| void | SetFreeBodyRandomRotationDistribution (const Body< T > &body, const Eigen::Quaternion< symbolic::Expression > &rotation) |
| Sets the distribution used by SetRandomState() to populate the rotation component of the floating-base state. More... | |
| void | SetFreeBodyRandomRotationDistributionToUniform (const Body< T > &body) |
| Sets the distribution used by SetRandomState() to populate the rotation component of the floating-base state using uniformly random rotations. More... | |
Adding new multibody elements | |
MultibodyPlant users will add modeling elements like bodies, joints, force elements, constraints, etc, using one of these methods. Once a user is done adding all modeling elements, the Finalize() method must be called before invoking any MultibodyPlant service to perform computations. An attempt to call any of these methods after a call to Finalize() on the plant, will result on an exception being thrown. See Finalize() for details. | |
| const RigidBody< T > & | AddRigidBody (const std::string &name, ModelInstanceIndex model_instance, const SpatialInertia< double > &M_BBo_B) |
| Creates a rigid body with the provided name and spatial inertia. More... | |
| const RigidBody< T > & | AddRigidBody (const std::string &name, const SpatialInertia< double > &M_BBo_B) |
| Creates a rigid body with the provided name and spatial inertia. More... | |
| template<template< typename > class FrameType> | |
| const FrameType< T > & | AddFrame (std::unique_ptr< FrameType< T >> frame) |
This method adds a Frame of type FrameType<T>. More... | |
| template<template< typename Scalar > class JointType> | |
| const JointType< T > & | AddJoint (std::unique_ptr< JointType< T >> joint) |
This method adds a Joint of type JointType between two bodies. More... | |
| template<template< typename > class JointType, typename... Args> | |
| const JointType< T > & | AddJoint (const std::string &name, const Body< T > &parent, const optional< math::RigidTransform< double >> &X_PF, const Body< T > &child, const optional< math::RigidTransform< double >> &X_BM, Args &&... args) |
This method adds a Joint of type JointType between two bodies. More... | |
| template<template< typename Scalar > class ForceElementType, typename... Args> | |
| const ForceElementType< T > & | AddForceElement (Args &&... args) |
Adds a new force element model of type ForceElementType to this MultibodyPlant. More... | |
| const JointActuator< T > & | AddJointActuator (const std::string &name, const Joint< T > &joint, double effort_limit=std::numeric_limits< double >::infinity()) |
Creates and adds a JointActuator model for an actuator acting on a given joint. More... | |
| ModelInstanceIndex | AddModelInstance (const std::string &name) |
| Creates a new model instance. More... | |
| const WeldJoint< T > & | WeldFrames (const Frame< T > &A, const Frame< T > &B, const math::RigidTransform< double > &X_AB=math::RigidTransform< double >::Identity()) |
Welds frames A and B with relative pose X_AB. More... | |
Querying for multibody elements by name | |
These methods allow a user to query whether a given multibody element is part of this plant's model. These queries can be performed at any time during the lifetime of a MultibodyPlant model, i.e. there is no restriction on whether they must be called before or after Finalize(). That is, these queries can be performed while new multibody elements are being added to the model. | |
| bool | HasBodyNamed (const std::string &name) const |
| bool | HasBodyNamed (const std::string &name, ModelInstanceIndex model_instance) const |
| bool | HasFrameNamed (const std::string &name) const |
| bool | HasFrameNamed (const std::string &name, ModelInstanceIndex model_instance) const |
| bool | HasJointNamed (const std::string &name) const |
| bool | HasJointNamed (const std::string &name, ModelInstanceIndex model_instance) const |
| bool | HasJointActuatorNamed (const std::string &name) const |
| bool | HasJointActuatorNamed (const std::string &name, ModelInstanceIndex model_instance) const |
| bool | HasModelInstanceNamed (const std::string &name) const |
Retrieving multibody elements by name | |
These methods allow a user to retrieve a reference to a multibody element by its name. An exception is thrown if there is no element with the requested name. | |
| const Body< T > & | GetBodyByName (const std::string &name) const |
| These queries can be performed at any time during the lifetime of a MultibodyPlant, i.e. More... | |
| const Body< T > & | GetBodyByName (const std::string &name, ModelInstanceIndex model_instance) const |
Returns a constant reference to the body that is uniquely identified by the string name and model_instance in this MultibodyPlant. More... | |
| std::vector< BodyIndex > | GetBodyIndices (ModelInstanceIndex model_instance) const |
Returns a list of body indices associated with model_instance. More... | |
| std::vector< JointIndex > | GetJointIndices (ModelInstanceIndex model_instance) const |
Returns a list of joint indices associated with model_instance. More... | |
| const Frame< T > & | GetFrameByName (const std::string &name) const |
Returns a constant reference to a frame that is identified by the string name in this model. More... | |
| const Frame< T > & | GetFrameByName (const std::string &name, ModelInstanceIndex model_instance) const |
Returns a constant reference to the frame that is uniquely identified by the string name in model_instance. More... | |
| const RigidBody< T > & | GetRigidBodyByName (const std::string &name) const |
Returns a constant reference to a rigid body that is identified by the string name in this model. More... | |
| const RigidBody< T > & | GetRigidBodyByName (const std::string &name, ModelInstanceIndex model_instance) const |
Returns a constant reference to the rigid body that is uniquely identified by the string name in model_instance. More... | |
| template<template< typename > class JointType = Joint> | |
| const JointType< T > & | GetJointByName (const std::string &name, optional< ModelInstanceIndex > model_instance=nullopt) const |
Returns a constant reference to a joint that is identified by the string name in this MultibodyPlant. More... | |
| template<template< typename > class JointType = Joint> | |
| JointType< T > & | GetMutableJointByName (const std::string &name, optional< ModelInstanceIndex > model_instance=nullopt) |
| A version of GetJointByName that returns a mutable reference. More... | |
| const JointActuator< T > & | GetJointActuatorByName (const std::string &name) const |
Returns a constant reference to an actuator that is identified by the string name in this MultibodyPlant. More... | |
| const JointActuator< T > & | GetJointActuatorByName (const std::string &name, ModelInstanceIndex model_instance) const |
Returns a constant reference to the actuator that is uniquely identified by the string name and model_instance in this MultibodyPlant. More... | |
| ModelInstanceIndex | GetModelInstanceByName (const std::string &name) const |
Returns the index to the model instance that is uniquely identified by the string name in this MultibodyPlant. More... | |
Model instance accessors | |
Many of this class's methods expect vectors of tree state or joint actuator inputs which encompass the entire tree. Methods in this section are convenience accessors for the portion of those vectors which apply to a single model instance only. | |
| void | SetActuationInArray (ModelInstanceIndex model_instance, const Eigen::Ref< const VectorX< T >> &u_instance, EigenPtr< VectorX< T >> u) const |
Given the actuation values u_instance for all actuators in model_instance, this method sets the actuation vector u for the entire model to which this actuator belongs to. More... | |
| VectorX< T > | GetPositionsFromArray (ModelInstanceIndex model_instance, const Eigen::Ref< const VectorX< T >> &q) const |
Returns a vector of generalized positions for model_instance from a vector q_array of generalized positions for the entire model model. More... | |
| void | SetPositionsInArray (ModelInstanceIndex model_instance, const Eigen::Ref< const VectorX< T >> &q_instance, EigenPtr< VectorX< T >> q) const |
Sets the vector of generalized positions for model_instance in q using q_instance, leaving all other elements in the array untouched. More... | |
| VectorX< T > | GetVelocitiesFromArray (ModelInstanceIndex model_instance, const Eigen::Ref< const VectorX< T >> &v) const |
Returns a vector of generalized velocities for model_instance from a vector v of generalized velocities for the entire MultibodyPlant model. More... | |
| void | SetVelocitiesInArray (ModelInstanceIndex model_instance, const Eigen::Ref< const VectorX< T >> &v_instance, EigenPtr< VectorX< T >> v) const |
Sets the vector of generalized velocities for model_instance in v using v_instance, leaving all other elements in the array untouched. More... | |
Accessing the state | |
| void | SetFreeBodyPoseInWorldFrame (systems::Context< T > *context, const Body< T > &body, const math::RigidTransform< T > &X_WB) const |
Sets context to store the pose X_WB of a given body B in the world frame W. More... | |
| void | SetFreeBodyPoseInAnchoredFrame (systems::Context< T > *context, const Frame< T > &frame_F, const Body< T > &body, const math::RigidTransform< T > &X_FB) const |
Updates context to store the pose X_FB of a given body B in a frame F. More... | |
| math::RigidTransform< T > | CalcRelativeTransform (const systems::Context< T > &context, const Frame< T > &frame_F, const Frame< T > &frame_G) const |
Calculates the rigid transform (pose) X_FG relating frame F and frame G. More... | |
| math::RotationMatrix< T > | CalcRelativeRotationMatrix (const systems::Context< T > &context, const Frame< T > &frame_F, const Frame< T > &frame_G) const |
Calculates the rotation matrix R_FG relating frame F and frame G. More... | |
| void | CalcPointsPositions (const systems::Context< T > &context, const Frame< T > &frame_B, const Eigen::Ref< const MatrixX< T >> &p_BQi, const Frame< T > &frame_A, EigenPtr< MatrixX< T >> p_AQi) const |
Given the positions p_BQi for a set of points Qi measured and expressed in a frame B, this method computes the positions p_AQi(q) of each point Qi in the set as measured and expressed in another frame A, as a function of the generalized positions q of the model. More... | |
| Vector3< T > | CalcCenterOfMassPosition (const systems::Context< T > &context) const |
This method computes the center of mass position p_WCcm of all bodies in MultibodyPlant measured and expressed in world frame W. More... | |
| Vector3< T > | CalcCenterOfMassPosition (const systems::Context< T > &context, const std::vector< ModelInstanceIndex > &model_instances) const |
| This method computes the center of mass position p_WCcm of specified model instances measured and expressed in world frame W. More... | |
| const math::RigidTransform< T > & | EvalBodyPoseInWorld (const systems::Context< T > &context, const Body< T > &body_B) const |
Evaluate the pose X_WB of a body B in the world frame W. More... | |
| const SpatialVelocity< T > & | EvalBodySpatialVelocityInWorld (const systems::Context< T > &context, const Body< T > &body_B) const |
Evaluate the spatial velocity V_WB of a body B in the world frame W. More... | |
| void | CalcPointsGeometricJacobianExpressedInWorld (const systems::Context< T > &context, const Frame< T > &frame_F, const Eigen::Ref< const MatrixX< T >> &p_FP_list, EigenPtr< MatrixX< T >> p_WP_list, EigenPtr< MatrixX< T >> Jv_WFp) const |
Given a list of points with fixed position vectors p_FP in a frame F, (that is, their time derivative DtF(p_FP) in frame F is zero), this method computes the geometric Jacobian Jv_WFp defined by: More... | |
| VectorX< T > | CalcBiasForPointsGeometricJacobianExpressedInWorld (const systems::Context< T > &context, const Frame< T > &frame_F, const Eigen::Ref< const MatrixX< T >> &p_FP_list) const |
Computes the bias term b_WFp associated with the translational acceleration a_WFp of a point P instantaneously moving with a frame F. More... | |
| VectorX< T > | CalcBiasForJacobianTranslationalVelocity (const systems::Context< T > &context, JacobianWrtVariable with_respect_to, const Frame< T > &frame_F, const Eigen::Ref< const MatrixX< T >> &p_FP_list, const Frame< T > &frame_A, const Frame< T > &frame_E) const |
For a point Fp that is regarded as a point of (fixed/welded to) a frame F, computes bias term abias_AFp associated with a_AFp (Fp's translational acceleration in a frame A) with respect to "speeds" 𝑠, where 𝑠 is either q̇ ≜ [q̇₁ ... More... | |
| void | CalcPointsGeometricJacobianExpressedInWorld (const systems::Context< T > &context, const Frame< T > &frame_F, const Eigen::Ref< const MatrixX< T >> &p_WP_list, EigenPtr< MatrixX< T >> Jv_WFp) const |
This is a variant to compute the geometric Jacobian Jv_WFp for a list of points P moving with frame_F, given that we know the position p_WP of each point in the list measured and expressed in the world frame W. More... | |
| void | CalcPointsAnalyticalJacobianExpressedInWorld (const systems::Context< T > &context, const Frame< T > &frame_F, const Eigen::Ref< const MatrixX< T >> &p_FP_list, EigenPtr< MatrixX< T >> p_WP_list, EigenPtr< MatrixX< T >> Jq_WFp) const |
Given a list of points with fixed position vectors p_FP in a frame F, (that is, their time derivative DtF(p_FP) in frame F is zero), this method computes the analytical Jacobian Jq_WFp(q). More... | |
| void | CalcFrameGeometricJacobianExpressedInWorld (const systems::Context< T > &context, const Frame< T > &frame_F, const Eigen::Ref< const Vector3< T >> &p_FP, EigenPtr< MatrixX< T >> J_WFp) const |
Given a frame Fp defined by shifting a frame F from its origin Fo to a new origin P, this method computes the geometric Jacobian Jv_WFp for frame Fp. More... | |
| void | CalcRelativeFrameGeometricJacobian (const systems::Context< T > &context, const Frame< T > &frame_B, const Eigen::Ref< const Vector3< T >> &p_BP, const Frame< T > &frame_A, const Frame< T > &frame_E, EigenPtr< MatrixX< T >> Jv_ABp_E) const |
| Computes the geometric Jacobian for a point moving with a given frame. More... | |
| Vector6< T > | CalcBiasForFrameGeometricJacobianExpressedInWorld (const systems::Context< T > &context, const Frame< T > &frame_F, const Eigen::Ref< const Vector3< T >> &p_FP) const |
Given a frame Fp defined by shifting a frame F from its origin Fo to a new origin P, this method computes the bias term Ab_WFp associated with the spatial acceleration A_WFp a frame Fp instantaneously moving with a frame F at a fixed position p_FP. More... | |
| Vector6< T > | CalcBiasForJacobianSpatialVelocity (const systems::Context< T > &context, JacobianWrtVariable with_respect_to, const Frame< T > &frame_F, const Eigen::Ref< const Vector3< T >> &p_FoFp_F, const Frame< T > &frame_A, const Frame< T > &frame_E) const |
For a point Fp that is regarded as a point of (fixed/welded to) a frame F, computes the bias term Abias_AFp associated with A_AFp (Fp's spatial acceleration in a frame A) with respect to "speeds" 𝑠, where 𝑠 is either q̇ ≜ [q̇₁ ... More... | |
| void | CalcJacobianSpatialVelocity (const systems::Context< T > &context, JacobianWrtVariable with_respect_to, const Frame< T > &frame_B, const Eigen::Ref< const Vector3< T >> &p_BoBi_B, const Frame< T > &frame_A, const Frame< T > &frame_E, EigenPtr< MatrixX< T >> Jw_ABp_E) const |
For each point Bi of (fixed to) a frame B with spatial velocity v_ABi in a frame A, calculates Bi's spatial velocity Jacobian in A with respect to 𝑠, which is defined as. More... | |
| void | CalcJacobianAngularVelocity (const systems::Context< T > &context, const JacobianWrtVariable with_respect_to, const Frame< T > &frame_B, const Frame< T > &frame_A, const Frame< T > &frame_E, EigenPtr< Matrix3X< T >> Js_w_AB_E) const |
| Returns a frame B's angular velocity Jacobian in a frame A with respect to "speeds" 𝑠, where 𝑠 is either q̇ ≜ [q̇₁ ... More... | |
| void | CalcJacobianTranslationalVelocity (const systems::Context< T > &context, JacobianWrtVariable with_respect_to, const Frame< T > &frame_B, const Eigen::Ref< const Matrix3X< T >> &p_BoBi_B, const Frame< T > &frame_A, const Frame< T > &frame_E, EigenPtr< MatrixX< T >> Js_v_ABi_E) const |
For each point Bi of (fixed to) a frame B with translational velocity v_ABi in a frame A, calculates Bi's translational velocity Jacobian in A with respect to 𝑠, which is defined as. More... | |
| void | CalcSpatialAccelerationsFromVdot (const systems::Context< T > &context, const VectorX< T > &known_vdot, std::vector< SpatialAcceleration< T >> *A_WB_array) const |
Given the state of this model in context and a known vector of generalized accelerations known_vdot, this method computes the spatial acceleration A_WB for each body as measured and expressed in the world frame W. More... | |
| VectorX< T > | CalcInverseDynamics (const systems::Context< T > &context, const VectorX< T > &known_vdot, const MultibodyForces< T > &external_forces) const |
Given the state of this model in context and a known vector of generalized accelerations vdot, this method computes the set of generalized forces tau that would need to be applied in order to attain the specified generalized accelerations. More... | |
| void | CalcForceElementsContribution (const systems::Context< T > &context, MultibodyForces< T > *forces) const |
| Computes the combined force contribution of ForceElement objects in the model. More... | |
| T | CalcPotentialEnergy (const systems::Context< T > &context) const |
Computes and returns the total potential energy stored in this multibody model for the configuration given by context. More... | |
| T | CalcConservativePower (const systems::Context< T > &context) const |
| Computes and returns the power generated by conservative forces in the multibody model. More... | |
| void | CalcBiasTerm (const systems::Context< T > &context, EigenPtr< VectorX< T >> Cv) const |
Computes the bias term C(q, v)v containing Coriolis and gyroscopic effects of the multibody equations of motion: More... | |
| VectorX< T > | CalcGravityGeneralizedForces (const systems::Context< T > &context) const |
Computes the generalized forces tau_g(q) due to gravity as a function of the generalized positions q stored in the input context. More... | |
| void | MapVelocityToQDot (const systems::Context< T > &context, const Eigen::Ref< const VectorX< T >> &v, EigenPtr< VectorX< T >> qdot) const |
Transforms generalized velocities v to time derivatives qdot of the generalized positions vector q (stored in context). More... | |
| void | MapQDotToVelocity (const systems::Context< T > &context, const Eigen::Ref< const VectorX< T >> &qdot, EigenPtr< VectorX< T >> v) const |
Transforms the time derivative qdot of the generalized positions vector q (stored in context) to generalized velocities v. More... | |
| MatrixX< double > | MakeStateSelectorMatrix (const std::vector< JointIndex > &user_to_joint_index_map) const |
This method allows users to map the state of this model, x, into a vector of selected state xₛ with a given preferred ordering. More... | |
| MatrixX< double > | MakeActuatorSelectorMatrix (const std::vector< JointActuatorIndex > &user_to_actuator_index_map) const |
This method allows user to map a vector uₛ containing the actuation for a set of selected actuators into the vector u containing the actuation values for this full model. More... | |
| MatrixX< double > | MakeActuatorSelectorMatrix (const std::vector< JointIndex > &user_to_joint_index_map) const |
Alternative signature to build an actuation selector matrix Su such that u = Su⋅uₛ, where u is the vector of actuation values for the full model (ordered by JointActuatorIndex) and uₛ is a vector of actuation values for the actuators acting on the joints listed by user_to_joint_index_map. More... | |
| VectorX< double > | GetPositionLowerLimits () const |
Returns a vector of size num_positions() containing the lower position limits for every generalized position coordinate. More... | |
| VectorX< double > | GetPositionUpperLimits () const |
| Upper limit analog of GetPositionsLowerLimits(), where any unbounded or unspecified limits will be +infinity. More... | |
| VectorX< double > | GetVelocityLowerLimits () const |
Returns a vector of size num_velocities() containing the lower velocity limits for every generalized velocity coordinate. More... | |
| VectorX< double > | GetVelocityUpperLimits () const |
| Upper limit analog of GetVelocitysLowerLimits(), where any unbounded or unspecified limits will be +infinity. More... | |
| VectorX< double > | GetAccelerationLowerLimits () const |
Returns a vector of size num_velocities() containing the lower acceleration limits for every generalized velocity coordinate. More... | |
| VectorX< double > | GetAccelerationUpperLimits () const |
| Upper limit analog of GetAccelerationsLowerLimits(), where any unbounded or unspecified limits will be +infinity. More... | |
| void | CalcMassMatrixViaInverseDynamics (const systems::Context< T > &context, EigenPtr< MatrixX< T >> H) const |
Performs the computation of the mass matrix M(q) of the model using inverse dynamics, where the generalized positions q are stored in context. More... | |
Managing geometries for bodies | |
The following methods provide a convenient means for associating geometries with bodies. Ultimately, the geometries are owned by SceneGraph. These methods do the work of registering the requested geometries with SceneGraph and maintaining a mapping between the body and the registered data. Particularly, SceneGraph knows nothing about the concepts inherent in the MultibodyPlant. These methods account for those differences as documented below. Geometry registration with rolesGeometries can be associated with bodies via the All geometry registration methods return a geometry::GeometryId GeometryId. This is how SceneGraph refers to the geometries. The properties of an individual geometry can be accessed with its id and geometry::SceneGraphInspector and geometry::QueryObject (for its state-dependent pose in world). Body frames and SceneGraph framesThe first time a geometry registration method is called on a particular body, that body's frame B is registered with SceneGraph. As SceneGraph knows nothing about bodies, in the SceneGraph domain, the frame is simply notated as F; this is merely an alias for the body frame. Thus, the pose of the geometry G in the SceneGraph frame F is the same as the pose of the geometry in the body frame B; The model instance index of the body is passed to the SceneGraph frame as its "frame group". This can be retrieved from the geometry::SceneGraphInspector::GetFrameGroup(FrameId) method. Given a GeometryId, SceneGraph cannot report what body it is affixed to. It can only report the SceneGraph alias frame F. But the following idiom can report the body: const MultibodyPlant<T>& plant = ...; const SceneGraphInspector<T>& inspector = ...; const GeometryId g_id = id_from_some_query; const FrameId f_id = inspector.GetFrameId(g_id); const Body<T>* body = plant.GetBodyFromFrameId(f_id); See documentation of geometry::SceneGraphInspector on where to get an inspector. In MultibodyPlant, frame names only have to be unique in a single model instance. However, SceneGraph knows nothing of model instances. So, to generate unique names for the corresponding frames in SceneGraph, when MultibodyPlant registers the corresponding SceneGraph frame, it is named with a "scoped name". This is a concatenation of | |
| geometry::GeometryId | RegisterVisualGeometry (const Body< T > &body, const math::RigidTransform< double > &X_BG, const geometry::Shape &shape, const std::string &name, const geometry::IllustrationProperties &properties) |
Registers geometry in a SceneGraph with a given geometry::Shape to be used for visualization of a given body. More... | |
| geometry::GeometryId | RegisterVisualGeometry (const Body< T > &body, const math::RigidTransform< double > &X_BG, const geometry::Shape &shape, const std::string &name, const geometry::IllustrationProperties &properties, geometry::SceneGraph< T > *scene_graph) |
| (Do not use.) This is a deprecated overload that takes a scene_graph argument. More... | |
| geometry::GeometryId | RegisterVisualGeometry (const Body< T > &body, const math::RigidTransform< double > &X_BG, const geometry::Shape &shape, const std::string &name, const Vector4< double > &diffuse_color) |
Overload for visual geometry registration; it converts the diffuse_color (RGBA with values in the range [0, 1]) into a geometry::ConnectDrakeVisualizer()-compatible set of geometry::IllustrationProperties. More... | |
| geometry::GeometryId | RegisterVisualGeometry (const Body< T > &body, const math::RigidTransform< double > &X_BG, const geometry::Shape &shape, const std::string &name, const Vector4< double > &diffuse_color, geometry::SceneGraph< T > *scene_graph) |
| (Do not use.) This is a deprecated overload that takes a scene_graph argument. More... | |
| geometry::GeometryId | RegisterVisualGeometry (const Body< T > &body, const math::RigidTransform< double > &X_BG, const geometry::Shape &shape, const std::string &name) |
| Overload for visual geometry registration; it relies on the downstream geometry::IllustrationProperties consumer to provide default parameter values (see Geometry Roles for details). More... | |
| geometry::GeometryId | RegisterVisualGeometry (const Body< T > &body, const math::RigidTransform< double > &X_BG, const geometry::Shape &shape, const std::string &name, geometry::SceneGraph< T > *scene_graph) |
| (Do not use.) This is a deprecated overload that takes a scene_graph argument. More... | |
| const std::vector< geometry::GeometryId > & | GetVisualGeometriesForBody (const Body< T > &body) const |
Returns an array of GeometryId's identifying the different visual geometries for body previously registered with a SceneGraph. More... | |
| int | num_visual_geometries () const |
| Returns the number of geometries registered for visualization. More... | |
| geometry::GeometryId | RegisterCollisionGeometry (const Body< T > &body, const math::RigidTransform< double > &X_BG, const geometry::Shape &shape, const std::string &name, const CoulombFriction< double > &coulomb_friction) |
Registers geometry in a SceneGraph with a given geometry::Shape to be used for the contact modeling of a given body. More... | |
| geometry::GeometryId | RegisterCollisionGeometry (const Body< T > &body, const math::RigidTransform< double > &X_BG, const geometry::Shape &shape, const std::string &name, const CoulombFriction< double > &coulomb_friction, geometry::SceneGraph< T > *scene_graph) |
| (Do not use.) This is a deprecated overload that takes a scene_graph argument. More... | |
| const std::vector< geometry::GeometryId > & | GetCollisionGeometriesForBody (const Body< T > &body) const |
Returns an array of GeometryId's identifying the different contact geometries for body previously registered with a SceneGraph. More... | |
| int | num_collision_geometries () const |
| Returns the number of geometries registered for contact modeling. More... | |
| geometry::GeometrySet | CollectRegisteredGeometries (const std::vector< const Body< T > * > &bodies) const |
For each of the provided bodies, collects up all geometries that have been registered to that body. More... | |
Retrieving ports for communication with a SceneGraph. | |
| optional< geometry::SourceId > | get_source_id () const |
Returns the unique id identifying this plant as a source for a SceneGraph. More... | |
| const systems::InputPort< T > & | get_geometry_query_input_port () const |
| Returns a constant reference to the input port used to perform geometric queries on a SceneGraph. More... | |
| const systems::OutputPort< T > & | get_geometry_poses_output_port () const |
| Returns the output port of frames' poses to communicate with a SceneGraph. More... | |
Actuation input | |
The input vector of actuation values can be provided either as a single input port which describes the entire plant (in the case where only a single model instance has actuated dofs), or through multiple input ports which each provide the actuation values for a specific model instance. See AddJointActuator() and num_actuators(). | |
| const systems::InputPort< T > & | get_actuation_input_port () const |
| Returns a constant reference to the input port for external actuation for the case where only one model instance has actuated dofs. More... | |
| const systems::InputPort< T > & | get_actuation_input_port (ModelInstanceIndex model_instance) const |
| Returns a constant reference to the input port for external actuation for a specific model instance. More... | |
| const systems::InputPort< T > & | get_applied_generalized_force_input_port () const |
Returns a constant reference to the vector-valued input port for applied generalized forces, and the vector will be added directly into tau (see System dynamics). More... | |
| const systems::InputPort< T > & | get_applied_spatial_force_input_port () const |
| Returns a constant reference to the input port for applying spatial forces to bodies in the plant. More... | |
Continuous state output | |
Output ports are provided to access the continuous state of the whole plant and for individual model instances. | |
| const systems::OutputPort< T > & | get_state_output_port () const |
Returns a constant reference to the output port for the full state x = [q v] of the model. More... | |
| const systems::OutputPort< T > & | get_state_output_port (ModelInstanceIndex model_instance) const |
| Returns a constant reference to the output port for the state of a specific model instance. More... | |
Contact by penalty method | |
Currently MultibodyPlant uses a rigid contact model that is, bodies in the model are infinitely stiff or ideal rigid bodies. Therefore, the mathematical description of the rigid contact model needs to include non-penetration constraints among bodies in the formulation. There are several numerical methods to impose and solve these constraints. In a penalty method approach, we allow for a certain amount of interpenetration and we compute contact forces according to a simple law of the form: fₙ = k(1+dẋ)x where the normal contact force
There is no exact procedure for choosing these coefficients, and estimating them manually can be cumbersome since in general they will depend on the scale of the problem including masses, speeds and even body sizes. However, MultibodyPlant aids the estimation of these coefficients using a heuristic function based on a user-supplied "penetration allowance", see set_penetration_allowance(). The penetration allowance is a number in meters that specifies the order of magnitude of the average penetration between bodies in the system that the user is willing to accept as reasonable for the problem being solved. For instance, in the robotics manipulation of ordinary daily objects the user might set this number to 1 millimeter. However, the user might want to increase it for the simulation of heavy walking robots for which an allowance of 1 millimeter would result in a very stiff system. As for the damping coefficient in the simple law above, MultibodyPlant chooses the damping coefficient d to model inelastic collisions and therefore sets it so that the penetration distance x behaves as a critically damped oscillator. That is, at the limit of ideal rigid contact (very stiff penalty coefficient k or equivalently the penetration allowance goes to zero), this method behaves as a unilateral constraint on the penetration distance, which models a perfect inelastic collision. For most applications, such as manipulation and walking, this is the desired behavior. When set_penetration_allowance() is called, MultibodyPlant will estimate reasonable penalty method coefficients as a function of the input penetration allowance. Users will want to run their simulation a number of times and asses they are satisfied with the level of inter-penetration actually observed in the simulation; if the observed penetration is too large, the user will want to set a smaller penetration allowance. If the system is too stiff and the time integration requires very small time steps while at the same time the user can afford larger inter-penetrations, the user will want to increase the penetration allowance. Typically, the observed penetration will be proportional to the penetration allowance. Thus scaling the penetration allowance by say a factor of 0.5, would typically results in inter-penetrations being reduced by the same factor of 0.5. In summary, users should choose the largest penetration allowance that results in inter-penetration levels that are acceptable for the particular application (even when in theory this penetration should be zero for perfectly rigid bodies.) For a given penetration allowance, the contact interaction that takes two bodies with a non-zero approaching velocity to zero approaching velocity, takes place in a finite amount of time (for ideal rigid contact this time is zero.) A good estimate of this time period is given by a call to get_contact_penalty_method_time_scale(). Users might want to query this value to either set the maximum time step in error-controlled time integration or to set the time step for fixed time step integration. As a guidance, typical fixed time step integrators will become unstable for time steps larger than about a tenth of this time scale. For further details on contact modeling in Drake, please refer to the section Contact Modeling in Drake of our documentation. | |
| void | set_penetration_allowance (double penetration_allowance=0.001) |
| Sets the penetration allowance used to estimate the coefficients in the penalty method used to impose non-penetration among bodies. More... | |
| double | get_contact_penalty_method_time_scale () const |
Returns a time-scale estimate tc based on the requested penetration allowance δ set with set_penetration_allowance(). More... | |
Stribeck model of friction | |
Currently MultibodyPlant uses the Stribeck approximation to model dry friction. The Stribeck model of friction is an approximation to Coulomb's law of friction that allows using continuous time integration without the need to specify complementarity constraints. While this results in a simpler model immediately tractable with standard numerical methods for integration of ODE's, it often leads to stiff dynamics that require an explicit integrator to take very small time steps. It is therefore recommended to use error controlled integrators when using this model or the discrete time stepping (see Choice of Time Advancement Strategy). See Stribeck Approximation of Coulomb Friction for a detailed discussion of the Stribeck model. | |
| void | set_stiction_tolerance (double v_stiction=0.001) |
Sets the stiction tolerance v_stiction for the Stribeck model, where v_stiction must be specified in m/s (meters per second.) v_stiction defaults to a value of 1 millimeter per second. More... | |
 Public Member Functions inherited from MultibodyTreeSystem< T > | |
| MultibodyTreeSystem (std::unique_ptr< MultibodyTree< T >> tree, bool is_discrete=false) | |
Takes ownership of the given tree, finalizes it if it hasn't already been finalized, and then allocates the resources it needs. More... | |
| template<typename U > | |
| MultibodyTreeSystem (const MultibodyTreeSystem< U > &other) | |
| Scalar-converting copy constructor. More... | |
| ~MultibodyTreeSystem () override | |
| bool | is_discrete () const |
| const PositionKinematicsCache< T > & | EvalPositionKinematics (const systems::Context< T > &context) const |
| Returns a reference to the up to date PositionKinematicsCache in the given Context, recalculating it first if necessary. More... | |
| const VelocityKinematicsCache< T > & | EvalVelocityKinematics (const systems::Context< T > &context) const |
| Returns a reference to the up to date VelocityKinematicsCache in the given Context, recalculating it first if necessary. More... | |
| const std::vector< SpatialInertia< T > > & | EvalSpatialInertiaInWorldCache (const systems::Context< T > &context) const |
| Returns a reference to the up to date cache of per-body spatial inertias in the given Context, recalculating it first if necessary. More... | |
| const std::vector< SpatialForce< T > > & | EvalDynamicBiasCache (const systems::Context< T > &context) const |
| Returns a reference to the up to date cache of per-body bias terms in the given Context, recalculating it first if necessary. More... | |
| const std::vector< Vector6< T > > & | EvalAcrossNodeGeometricJacobianExpressedInWorld (const systems::Context< T > &context) const |
| Returns a reference to the up to date cached value for the across-mobilizer geometric Jacobian H_PB_W in the given Context, recalculating it first if necessary. More... | |
| MultibodyTreeSystem (const MultibodyTreeSystem &)=delete | |
| MultibodyTreeSystem & | operator= (const MultibodyTreeSystem &)=delete |
| MultibodyTreeSystem (MultibodyTreeSystem &&)=delete | |
| MultibodyTreeSystem & | operator= (MultibodyTreeSystem &&)=delete |
| Public Member Functions inherited from LeafSystem< T > | |
| ~LeafSystem () override | |
| std::unique_ptr< CompositeEventCollection< T > > | AllocateCompositeEventCollection () const final |
| Allocates a CompositeEventCollection object for this system. More... | |
| std::unique_ptr< LeafContext< T > > | AllocateContext () const |
| Shadows System<T>::AllocateContext to provide a more concrete return type LeafContext<T>. More... | |
| std::unique_ptr< ContextBase > | DoAllocateContext () const final |
| Derived class implementations should allocate a suitable concrete Context type, then invoke the above InitializeContextBase() method. More... | |
| void | SetDefaultState (const Context< T > &context, State< T > *state) const override |
| Default implementation: sets all continuous state to the model vector given in DeclareContinuousState (or zero if no model vector was given) and discrete states to zero. More... | |
| void | SetDefaultParameters (const Context< T > &context, Parameters< T > *parameters) const override |
| Default implementation: sets all numeric parameters to the model vector given to DeclareNumericParameter, or else if no model was provided sets the numeric parameter to one. More... | |
| std::unique_ptr< ContinuousState< T > > | AllocateTimeDerivatives () const override |
| Returns the AllocateContinuousState value, which must not be nullptr. More... | |
| std::unique_ptr< DiscreteValues< T > > | AllocateDiscreteVariables () const override |
| Returns the AllocateDiscreteState value, which must not be nullptr. More... | |
| std::multimap< int, int > | GetDirectFeedthroughs () const final |
| Reports all direct feedthroughs from input ports to output ports. More... | |
| LeafSystem (const LeafSystem &)=delete | |
| LeafSystem & | operator= (const LeafSystem &)=delete |
| LeafSystem (LeafSystem &&)=delete | |
| LeafSystem & | operator= (LeafSystem &&)=delete |
| Public Member Functions inherited from System< T > | |
| ~System () override | |
| void | GetWitnessFunctions (const Context< T > &context, std::vector< const WitnessFunction< T > * > *w) const |
| Gets the witness functions active for the given state. More... | |
| T | CalcWitnessValue (const Context< T > &context, const WitnessFunction< T > &witness_func) const |
| Evaluates a witness function at the given context. More... | |
| const CacheEntry & | DeclareCacheEntry (std::string description, CacheEntry::AllocCallback alloc_function, CacheEntry::CalcCallback calc_function, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares a new CacheEntry in this System using the least-restrictive definitions for the associated functions. More... | |
| template<class MySystem , class MyContext , typename ValueType > | |
| const CacheEntry & | DeclareCacheEntry (std::string description, ValueType(MySystem::*make)() const, void(MySystem::*calc)(const MyContext &, ValueType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares a cache entry by specifying member functions to use both for the allocator and calculator. More... | |
| template<class MySystem , class MyContext , typename ValueType > | |
| const CacheEntry & | DeclareCacheEntry (std::string description, const ValueType &model_value, void(MySystem::*calc)(const MyContext &, ValueType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
Declares a cache entry by specifying a model value of concrete type ValueType and a calculator function that is a class member function (method) with signature: More... | |
| template<class MySystem , class MyContext , typename ValueType > | |
| const CacheEntry & | DeclareCacheEntry (std::string description, const ValueType &model_value, ValueType(MySystem::*calc)(const MyContext &) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
Declares a cache entry by specifying a model value of concrete type ValueType and a calculator function that is a class member function (method) with signature: More... | |
| template<class MySystem , class MyContext , typename ValueType > | |
| const CacheEntry & | DeclareCacheEntry (std::string description, void(MySystem::*calc)(const MyContext &, ValueType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares a cache entry by specifying only a calculator function that is a class member function (method) with signature: More... | |
| template<class MySystem , class MyContext , typename ValueType > | |
| const CacheEntry & | DeclareCacheEntry (std::string description, ValueType(MySystem::*calc)(const MyContext &) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares a cache entry by specifying only a calculator function that is a class member function (method) with signature: More... | |
| DependencyTicket | discrete_state_ticket (DiscreteStateIndex index) const |
| Returns a ticket indicating dependence on a particular discrete state variable xdᵢ (may be a vector). More... | |
| DependencyTicket | abstract_state_ticket (AbstractStateIndex index) const |
| Returns a ticket indicating dependence on a particular abstract state variable xaᵢ. More... | |
| DependencyTicket | numeric_parameter_ticket (NumericParameterIndex index) const |
| Returns a ticket indicating dependence on a particular numeric parameter pnᵢ (may be a vector). More... | |
| DependencyTicket | abstract_parameter_ticket (AbstractParameterIndex index) const |
| Returns a ticket indicating dependence on a particular abstract parameter paᵢ. More... | |
| DependencyTicket | input_port_ticket (InputPortIndex index) const |
Returns a ticket indicating dependence on input port uᵢ indicated by index. More... | |
| DependencyTicket | cache_entry_ticket (CacheIndex index) const |
Returns a ticket indicating dependence on the cache entry indicated by index. More... | |
| System (const System &)=delete | |
| System & | operator= (const System &)=delete |
| System (System &&)=delete | |
| System & | operator= (System &&)=delete |
| std::unique_ptr< Context< T > > | AllocateContext () const |
| Returns a Context<T> suitable for use with this System<T>. More... | |
| std::unique_ptr< BasicVector< T > > | AllocateInputVector (const InputPort< T > &input_port) const |
| Given an input port, allocates the vector storage. More... | |
| std::unique_ptr< AbstractValue > | AllocateInputAbstract (const InputPort< T > &input_port) const |
| Given an input port, allocates the abstract storage. More... | |
| std::unique_ptr< SystemOutput< T > > | AllocateOutput () const |
| Returns a container that can hold the values of all of this System's output ports. More... | |
| std::unique_ptr< Context< T > > | CreateDefaultContext () const |
| This convenience method allocates a context using AllocateContext() and sets its default values using SetDefaultContext(). More... | |
| void | SetDefaultContext (Context< T > *context) const |
| virtual void | SetRandomState (const Context< T > &context, State< T > *state, RandomGenerator *generator) const |
| Assigns random values to all elements of the state. More... | |
| virtual void | SetRandomParameters (const Context< T > &context, Parameters< T > *parameters, RandomGenerator *generator) const |
| Assigns random values to all parameters. More... | |
| void | SetRandomContext (Context< T > *context, RandomGenerator *generator) const |
| void | AllocateFixedInputs (Context< T > *context) const |
| For each input port, allocates a fixed input of the concrete type that this System requires, and binds it to the port, disconnecting any prior input. More... | |
| bool | HasAnyDirectFeedthrough () const |
Returns true if any of the inputs to the system might be directly fed through to any of its outputs and false otherwise. More... | |
| bool | HasDirectFeedthrough (int output_port) const |
Returns true if there might be direct-feedthrough from any input port to the given output_port, and false otherwise. More... | |
| bool | HasDirectFeedthrough (int input_port, int output_port) const |
Returns true if there might be direct-feedthrough from the given input_port to the given output_port, and false otherwise. More... | |
| virtual std::multimap< int, int > | GetDirectFeedthroughs () const=0 |
| Reports all direct feedthroughs from input ports to output ports. More... | |
| void | Publish (const Context< T > &context, const EventCollection< PublishEvent< T >> &events) const |
| This method is the public entry point for dispatching all publish event handlers. More... | |
| void | Publish (const Context< T > &context) const |
Forces a publish on the system, given a context. More... | |
| const ContinuousState< T > & | EvalTimeDerivatives (const Context< T > &context) const |
| Returns a reference to the cached value of the continuous state variable time derivatives, evaluating first if necessary using CalcTimeDerivatives(). More... | |
| const CacheEntry & | get_time_derivatives_cache_entry () const |
| (Advanced) Returns the CacheEntry used to cache time derivatives for EvalTimeDerivatives(). More... | |
| const T & | EvalPotentialEnergy (const Context< T > &context) const |
| Returns a reference to the cached value of the potential energy (PE), evaluating first if necessary using CalcPotentialEnergy(). More... | |
| const T & | EvalKineticEnergy (const Context< T > &context) const |
| Returns a reference to the cached value of the kinetic energy (KE), evaluating first if necessary using CalcKineticEnergy(). More... | |
| const T & | EvalConservativePower (const Context< T > &context) const |
| Returns a reference to the cached value of the conservative power (Pc), evaluating first if necessary using CalcConservativePower(). More... | |
| const T & | EvalNonConservativePower (const Context< T > &context) const |
| Returns a reference to the cached value of the non-conservative power (Pnc), evaluating first if necessary using CalcNonConservativePower(). More... | |
| template<template< typename > class Vec = BasicVector> | |
| const Vec< T > * | EvalVectorInput (const Context< T > &context, int port_index) const |
Returns the value of the vector-valued input port with the given port_index as a BasicVector or a specific subclass Vec derived from BasicVector. More... | |
| Eigen::VectorBlock< const VectorX< T > > | EvalEigenVectorInput (const Context< T > &context, int port_index) const |
Returns the value of the vector-valued input port with the given port_index as an Eigen vector. More... | |
| int | num_constraint_equations (const Context< T > &context) const |
| Gets the number of constraint equations for this system using the given context (useful in case the number of constraints is dependent upon the current state (as might be the case with a system modeled using piecewise differential algebraic equations). More... | |
| Eigen::VectorXd | EvalConstraintEquations (const Context< T > &context) const |
| Evaluates the constraint equations for the system at the generalized coordinates and generalized velocity specified by the context. More... | |
| Eigen::VectorXd | EvalConstraintEquationsDot (const Context< T > &context) const |
| Computes the time derivative of each constraint equation, evaluated at the generalized coordinates and generalized velocity specified by the context. More... | |
| Eigen::VectorXd | CalcVelocityChangeFromConstraintImpulses (const Context< T > &context, const Eigen::MatrixXd &J, const Eigen::VectorXd &lambda) const |
| Computes the change in velocity from applying the given constraint forces to the system at the given context. More... | |
| double | CalcConstraintErrorNorm (const Context< T > &context, const Eigen::VectorXd &error) const |
| Computes the norm on constraint error (used as a metric for comparing errors between the outputs of algebraic equations applied to two different state variable instances). More... | |
| SystemConstraintIndex | AddExternalConstraint (ExternalSystemConstraint constraint) |
| Adds an "external" constraint to this System. More... | |
| void | CalcTimeDerivatives (const Context< T > &context, ContinuousState< T > *derivatives) const |
Calculates the time derivatives xcdot of the continuous state xc into a given output argument. More... | |
| void | CalcDiscreteVariableUpdates (const Context< T > &context, const EventCollection< DiscreteUpdateEvent< T >> &events, DiscreteValues< T > *discrete_state) const |
| This method is the public entry point for dispatching all discrete variable update event handlers. More... | |
| void | ApplyDiscreteVariableUpdate (const EventCollection< DiscreteUpdateEvent< T >> &events, DiscreteValues< T > *discrete_state, Context< T > *context) const |
Given the discrete_state results of a previous call to CalcDiscreteVariableUpdates() that processed the given collection of events, modifies the context to reflect the updated discrete_state. More... | |
| void | CalcDiscreteVariableUpdates (const Context< T > &context, DiscreteValues< T > *discrete_state) const |
This method forces a discrete update on the system given a context, and the updated discrete state is stored in discrete_state. More... | |
| void | CalcUnrestrictedUpdate (const Context< T > &context, const EventCollection< UnrestrictedUpdateEvent< T >> &events, State< T > *state) const |
| This method is the public entry point for dispatching all unrestricted update event handlers. More... | |
| void | ApplyUnrestrictedUpdate (const EventCollection< UnrestrictedUpdateEvent< T >> &events, State< T > *state, Context< T > *context) const |
Given the state results of a previous call to CalcUnrestrictedUpdate() that processed the given collection of events, modifies the context to reflect the updated state. More... | |
| void | CalcUnrestrictedUpdate (const Context< T > &context, State< T > *state) const |
This method forces an unrestricted update on the system given a context, and the updated state is stored in state. More... | |
| T | CalcNextUpdateTime (const Context< T > &context, CompositeEventCollection< T > *events) const |
| This method is called by a Simulator during its calculation of the size of the next continuous step to attempt. More... | |
| void | GetPerStepEvents (const Context< T > &context, CompositeEventCollection< T > *events) const |
| This method is called by Simulator::Initialize() to gather all update and publish events that are to be handled in AdvanceTo() at the point before Simulator integrates continuous state. More... | |
| void | GetInitializationEvents (const Context< T > &context, CompositeEventCollection< T > *events) const |
| This method is called by Simulator::Initialize() to gather all update and publish events that need to be handled at initialization before the simulator starts integration. More... | |
| optional< PeriodicEventData > | GetUniquePeriodicDiscreteUpdateAttribute () const |
| Gets whether there exists a unique periodic attribute that triggers one or more discrete update events (and, if so, returns that unique periodic attribute). More... | |
| std::map< PeriodicEventData, std::vector< const Event< T > * >, PeriodicEventDataComparator > | GetPeriodicEvents () const |
| Gets all periodic triggered events for a system. More... | |
| void | CalcOutput (const Context< T > &context, SystemOutput< T > *outputs) const |
| Utility method that computes for every output port i the value y(i) that should result from the current contents of the given Context. More... | |
| T | CalcPotentialEnergy (const Context< T > &context) const |
Calculates and returns the potential energy represented by the current configuration provided in context. More... | |
| T | CalcKineticEnergy (const Context< T > &context) const |
Calculates and returns the kinetic energy represented by the current configuration and velocity provided in context. More... | |
| T | CalcConservativePower (const Context< T > &context) const |
Calculates and returns the conservative power represented by the current contents of the given context. More... | |
| T | CalcNonConservativePower (const Context< T > &context) const |
Calculates and returns the non-conservative power represented by the current contents of the given context. More... | |
| void | MapVelocityToQDot (const Context< T > &context, const VectorBase< T > &generalized_velocity, VectorBase< T > *qdot) const |
Transforms a given generalized velocity v to the time derivative qdot of the generalized configuration q taken from the supplied Context. More... | |
| void | MapVelocityToQDot (const Context< T > &context, const Eigen::Ref< const VectorX< T >> &generalized_velocity, VectorBase< T > *qdot) const |
| Transforms the given generalized velocity to the time derivative of generalized configuration. More... | |
| void | MapQDotToVelocity (const Context< T > &context, const VectorBase< T > &qdot, VectorBase< T > *generalized_velocity) const |
Transforms the time derivative qdot of the generalized configuration q to generalized velocities v. More... | |
| void | MapQDotToVelocity (const Context< T > &context, const Eigen::Ref< const VectorX< T >> &qdot, VectorBase< T > *generalized_velocity) const |
Transforms the given time derivative qdot of generalized configuration q to generalized velocity v. More... | |
| std::string | GetMemoryObjectName () const |
| Returns a name for this System based on a stringification of its type name and memory address. More... | |
| const InputPort< T > & | get_input_port (int port_index) const |
Returns the typed input port at index port_index. More... | |
| const InputPort< T > * | get_input_port_selection (variant< InputPortSelection, InputPortIndex > port_index) const |
| Returns the typed input port specified by the InputPortSelection or by the InputPortIndex. More... | |
| const InputPort< T > & | GetInputPort (const std::string &port_name) const |
Returns the typed input port with the unique name port_name. More... | |
| const OutputPort< T > & | get_output_port (int port_index) const |
Returns the typed output port at index port_index. More... | |
| const OutputPort< T > * | get_output_port_selection (variant< OutputPortSelection, OutputPortIndex > port_index) const |
| Returns the typed output port specified by the OutputPortSelection or by the OutputPortIndex. More... | |
| const OutputPort< T > & | GetOutputPort (const std::string &port_name) const |
Returns the typed output port with the unique name port_name. More... | |
| int | num_constraints () const |
| Returns the number of constraints specified for the system. More... | |
| int | num_continuous_states () const |
| Returns the dimension of the continuous state vector that has been declared until now. More... | |
| const SystemConstraint< T > & | get_constraint (SystemConstraintIndex constraint_index) const |
Returns the constraint at index constraint_index. More... | |
| boolean< T > | CheckSystemConstraintsSatisfied (const Context< T > &context, double tol) const |
Returns true if context satisfies all of the registered SystemConstraints with tolerance tol. More... | |
| void | CheckValidOutput (const SystemOutput< T > *output) const |
Checks that output is consistent with the number and size of output ports declared by the system. More... | |
| template<typename T1 = T> | |
| void | CheckValidContextT (const Context< T1 > &context) const |
Checks that context is consistent for this System template. More... | |
| VectorX< T > | CopyContinuousStateVector (const Context< T > &context) const |
Returns a copy of the continuous state vector xc into an Eigen vector. More... | |
| int | num_input_ports () const |
| Returns the number of input ports currently allocated in this System. More... | |
| int | num_output_ports () const |
| Returns the number of output ports currently allocated in this System. More... | |
| std::string | GetGraphvizString (int max_depth=std::numeric_limits< int >::max()) const |
| Returns a Graphviz string describing this System. More... | |
| int64_t | GetGraphvizId () const |
| Returns an opaque integer that uniquely identifies this system in the Graphviz output. More... | |
| void | FixInputPortsFrom (const System< double > &other_system, const Context< double > &other_context, Context< T > *target_context) const |
Fixes all of the input ports in target_context to their current values in other_context, as evaluated by other_system. More... | |
| const SystemScalarConverter & | get_system_scalar_converter () const |
| (Advanced) Returns the SystemScalarConverter for this object. More... | |
| std::unique_ptr< System< AutoDiffXd > > | ToAutoDiffXd () const |
| Creates a deep copy of this System, transmogrified to use the autodiff scalar type, with a dynamic-sized vector of partial derivatives. More... | |
| std::unique_ptr< System< AutoDiffXd > > | ToAutoDiffXdMaybe () const |
| Creates a deep copy of this system exactly like ToAutoDiffXd(), but returns nullptr if this System does not support autodiff, instead of throwing an exception. More... | |
| std::unique_ptr< System< symbolic::Expression > > | ToSymbolic () const |
| Creates a deep copy of this System, transmogrified to use the symbolic scalar type. More... | |
| std::unique_ptr< System< symbolic::Expression > > | ToSymbolicMaybe () const |
| Creates a deep copy of this system exactly like ToSymbolic(), but returns nullptr if this System does not support symbolic, instead of throwing an exception. More... | |
| Public Member Functions inherited from SystemBase | |
| ~SystemBase () override | |
| void | set_name (const std::string &name) |
| Sets the name of the system. More... | |
| const std::string & | get_name () const |
| Returns the name last supplied to set_name(), if any. More... | |
| const std::string & | GetSystemName () const final |
| Returns a human-readable name for this system, for use in messages and logging. More... | |
| std::string | GetSystemPathname () const final |
| Generates and returns a human-readable full path name of this subsystem, for use in messages and logging. More... | |
| std::string | GetSystemType () const final |
| Returns the most-derived type of this concrete System object as a human-readable string suitable for use in error messages. More... | |
| void | ThrowIfContextNotCompatible (const ContextBase &context) const final |
Throws an exception with an appropriate message if the given context is not compatible with this System. More... | |
| std::unique_ptr< ContextBase > | AllocateContext () const |
| Returns a Context suitable for use with this System. More... | |
| int | num_input_ports () const |
| Returns the number of input ports currently allocated in this System. More... | |
| int | num_output_ports () const |
| Returns the number of output ports currently allocated in this System. More... | |
| const InputPortBase & | get_input_port_base (InputPortIndex port_index) const |
Returns a reference to an InputPort given its port_index. More... | |
| const OutputPortBase & | get_output_port_base (OutputPortIndex port_index) const |
Returns a reference to an OutputPort given its port_index. More... | |
| int | num_total_inputs () const |
| Returns the total dimension of all of the vector-valued input ports (as if they were muxed). More... | |
| int | num_total_outputs () const |
| Returns the total dimension of all of the vector-valued output ports (as if they were muxed). More... | |
| int | num_cache_entries () const |
| Returns the number nc of cache entries currently allocated in this System. More... | |
| const CacheEntry & | get_cache_entry (CacheIndex index) const |
Returns a reference to a CacheEntry given its index. More... | |
| CacheEntry & | get_mutable_cache_entry (CacheIndex index) |
(Advanced) Returns a mutable reference to a CacheEntry given its index. More... | |
| void | CheckValidContext (const ContextBase &context) const |
| Checks whether the given context is valid for this System and throws an exception with a helpful message if not. More... | |
| SystemBase (const SystemBase &)=delete | |
| SystemBase & | operator= (const SystemBase &)=delete |
| SystemBase (SystemBase &&)=delete | |
| SystemBase & | operator= (SystemBase &&)=delete |
| const AbstractValue * | EvalAbstractInput (const ContextBase &context, int port_index) const |
Returns the value of the input port with the given port_index as an AbstractValue, which is permitted for ports of any type. More... | |
| template<typename V > | |
| const V * | EvalInputValue (const ContextBase &context, int port_index) const |
Returns the value of an abstract-valued input port with the given port_index as a value of known type V. More... | |
| const CacheEntry & | DeclareCacheEntry (std::string description, CacheEntry::AllocCallback alloc_function, CacheEntry::CalcCallback calc_function, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares a new CacheEntry in this System using the least-restrictive definitions for the associated functions. More... | |
| template<class MySystem , class MyContext , typename ValueType > | |
| const CacheEntry & | DeclareCacheEntry (std::string description, ValueType(MySystem::*make)() const, void(MySystem::*calc)(const MyContext &, ValueType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares a cache entry by specifying member functions to use both for the allocator and calculator. More... | |
| template<class MySystem , class MyContext , typename ValueType > | |
| const CacheEntry & | DeclareCacheEntry (std::string description, const ValueType &model_value, void(MySystem::*calc)(const MyContext &, ValueType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
Declares a cache entry by specifying a model value of concrete type ValueType and a calculator function that is a class member function (method) with signature: More... | |
| template<class MySystem , class MyContext , typename ValueType > | |
| const CacheEntry & | DeclareCacheEntry (std::string description, const ValueType &model_value, ValueType(MySystem::*calc)(const MyContext &) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
Declares a cache entry by specifying a model value of concrete type ValueType and a calculator function that is a class member function (method) with signature: More... | |
| template<class MySystem , class MyContext , typename ValueType > | |
| const CacheEntry & | DeclareCacheEntry (std::string description, void(MySystem::*calc)(const MyContext &, ValueType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares a cache entry by specifying only a calculator function that is a class member function (method) with signature: More... | |
| template<class MySystem , class MyContext , typename ValueType > | |
| const CacheEntry & | DeclareCacheEntry (std::string description, ValueType(MySystem::*calc)(const MyContext &) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares a cache entry by specifying only a calculator function that is a class member function (method) with signature: More... | |
| DependencyTicket | discrete_state_ticket (DiscreteStateIndex index) const |
| Returns a ticket indicating dependence on a particular discrete state variable xdᵢ (may be a vector). More... | |
| DependencyTicket | abstract_state_ticket (AbstractStateIndex index) const |
| Returns a ticket indicating dependence on a particular abstract state variable xaᵢ. More... | |
| DependencyTicket | numeric_parameter_ticket (NumericParameterIndex index) const |
| Returns a ticket indicating dependence on a particular numeric parameter pnᵢ (may be a vector). More... | |
| DependencyTicket | abstract_parameter_ticket (AbstractParameterIndex index) const |
| Returns a ticket indicating dependence on a particular abstract parameter paᵢ. More... | |
| DependencyTicket | input_port_ticket (InputPortIndex index) const |
Returns a ticket indicating dependence on input port uᵢ indicated by index. More... | |
| DependencyTicket | cache_entry_ticket (CacheIndex index) const |
Returns a ticket indicating dependence on the cache entry indicated by index. More... | |
| DependencyTicket | output_port_ticket (OutputPortIndex index) const |
(Internal use only) Returns a ticket indicating dependence on the output port indicated by index. More... | |
| int | num_discrete_state_groups () const |
| Returns the number of declared discrete state groups (each group is a vector-valued discrete state variable). More... | |
| int | num_abstract_states () const |
| Returns the number of declared abstract state variables. More... | |
| int | num_numeric_parameter_groups () const |
| Returns the number of declared numeric parameters (each of these is a vector-valued parameter). More... | |
| int | num_abstract_parameters () const |
| Returns the number of declared abstract parameters. More... | |
Friends | |
| template<typename U > | |
| class | MultibodyPlant |
| class | MultibodyPlantTester |
Additional Inherited Members | |
| Static Public Member Functions inherited from System< T > | |
| static DependencyTicket | nothing_ticket () |
| Returns a ticket indicating that a computation does not depend on any source value; that is, it is a constant. More... | |
| static DependencyTicket | time_ticket () |
| Returns a ticket indicating dependence on time. More... | |
| static DependencyTicket | accuracy_ticket () |
| Returns a ticket indicating dependence on the accuracy setting in the Context. More... | |
| static DependencyTicket | q_ticket () |
| Returns a ticket indicating that a computation depends on configuration state variables q. More... | |
| static DependencyTicket | v_ticket () |
| Returns a ticket indicating dependence on velocity state variables v. More... | |
| static DependencyTicket | z_ticket () |
| Returns a ticket indicating dependence on any or all of the miscellaneous continuous state variables z. More... | |
| static DependencyTicket | xc_ticket () |
| Returns a ticket indicating dependence on all of the continuous state variables q, v, or z. More... | |
| static DependencyTicket | xd_ticket () |
| Returns a ticket indicating dependence on all of the numerical discrete state variables, in any discrete variable group. More... | |
| static DependencyTicket | xa_ticket () |
| Returns a ticket indicating dependence on all of the abstract state variables in the current Context. More... | |
| static DependencyTicket | all_state_ticket () |
| Returns a ticket indicating dependence on all state variables x in this system, including continuous variables xc, discrete (numeric) variables xd, and abstract state variables xa. More... | |
| static DependencyTicket | pn_ticket () |
| Returns a ticket indicating dependence on all of the numerical parameters in the current Context. More... | |
| static DependencyTicket | pa_ticket () |
| Returns a ticket indicating dependence on all of the abstract parameters pa in the current Context. More... | |
| static DependencyTicket | all_parameters_ticket () |
| Returns a ticket indicating dependence on all parameters p in this system, including numeric parameters pn, and abstract parameters pa. More... | |
| static DependencyTicket | all_input_ports_ticket () |
| Returns a ticket indicating dependence on all input ports u of this system. More... | |
| static DependencyTicket | all_sources_ticket () |
| Returns a ticket indicating dependence on every possible independent source value, including time, accuracy, state, input ports, and parameters (but not cache entries). More... | |
| static DependencyTicket | configuration_ticket () |
| Returns a ticket indicating dependence on all source values that may affect configuration-dependent computations. More... | |
| static DependencyTicket | kinematics_ticket () |
| Returns a ticket indicating dependence on all source values that may affect configuration- or velocity-dependent computations. More... | |
| static DependencyTicket | xcdot_ticket () |
| Returns a ticket for the cache entry that holds time derivatives of the continuous variables. More... | |
| static DependencyTicket | pe_ticket () |
| Returns a ticket for the cache entry that holds the potential energy calculation. More... | |
| static DependencyTicket | ke_ticket () |
| Returns a ticket for the cache entry that holds the kinetic energy calculation. More... | |
| static DependencyTicket | pc_ticket () |
| Returns a ticket for the cache entry that holds the conservative power calculation. More... | |
| static DependencyTicket | pnc_ticket () |
| Returns a ticket for the cache entry that holds the non-conservative power calculation. More... | |
| template<template< typename > class S = ::drake::systems::System> | |
| static std::unique_ptr< S< AutoDiffXd > > | ToAutoDiffXd (const S< T > &from) |
Creates a deep copy of from, transmogrified to use the autodiff scalar type, with a dynamic-sized vector of partial derivatives. More... | |
| template<template< typename > class S = ::drake::systems::System> | |
| static std::unique_ptr< S< symbolic::Expression > > | ToSymbolic (const S< T > &from) |
Creates a deep copy of from, transmogrified to use the symbolic scalar type. More... | |
| Static Public Member Functions inherited from SystemBase | |
| static DependencyTicket | nothing_ticket () |
| Returns a ticket indicating that a computation does not depend on any source value; that is, it is a constant. More... | |
| static DependencyTicket | time_ticket () |
| Returns a ticket indicating dependence on time. More... | |
| static DependencyTicket | accuracy_ticket () |
| Returns a ticket indicating dependence on the accuracy setting in the Context. More... | |
| static DependencyTicket | q_ticket () |
| Returns a ticket indicating that a computation depends on configuration state variables q. More... | |
| static DependencyTicket | v_ticket () |
| Returns a ticket indicating dependence on velocity state variables v. More... | |
| static DependencyTicket | z_ticket () |
| Returns a ticket indicating dependence on any or all of the miscellaneous continuous state variables z. More... | |
| static DependencyTicket | xc_ticket () |
| Returns a ticket indicating dependence on all of the continuous state variables q, v, or z. More... | |
| static DependencyTicket | xd_ticket () |
| Returns a ticket indicating dependence on all of the numerical discrete state variables, in any discrete variable group. More... | |
| static DependencyTicket | xa_ticket () |
| Returns a ticket indicating dependence on all of the abstract state variables in the current Context. More... | |
| static DependencyTicket | all_state_ticket () |
| Returns a ticket indicating dependence on all state variables x in this system, including continuous variables xc, discrete (numeric) variables xd, and abstract state variables xa. More... | |
| static DependencyTicket | pn_ticket () |
| Returns a ticket indicating dependence on all of the numerical parameters in the current Context. More... | |
| static DependencyTicket | pa_ticket () |
| Returns a ticket indicating dependence on all of the abstract parameters pa in the current Context. More... | |
| static DependencyTicket | all_parameters_ticket () |
| Returns a ticket indicating dependence on all parameters p in this system, including numeric parameters pn, and abstract parameters pa. More... | |
| static DependencyTicket | all_input_ports_ticket () |
| Returns a ticket indicating dependence on all input ports u of this system. More... | |
| static DependencyTicket | all_sources_ticket () |
| Returns a ticket indicating dependence on every possible independent source value, including time, accuracy, state, input ports, and parameters (but not cache entries). More... | |
| static DependencyTicket | configuration_ticket () |
| Returns a ticket indicating dependence on all source values that may affect configuration-dependent computations. More... | |
| static DependencyTicket | kinematics_ticket () |
| Returns a ticket indicating dependence on all source values that may affect configuration- or velocity-dependent computations. More... | |
| static DependencyTicket | xcdot_ticket () |
| Returns a ticket for the cache entry that holds time derivatives of the continuous variables. More... | |
| static DependencyTicket | pe_ticket () |
| Returns a ticket for the cache entry that holds the potential energy calculation. More... | |
| static DependencyTicket | ke_ticket () |
| Returns a ticket for the cache entry that holds the kinetic energy calculation. More... | |
| static DependencyTicket | pc_ticket () |
| Returns a ticket for the cache entry that holds the conservative power calculation. More... | |
| static DependencyTicket | pnc_ticket () |
| Returns a ticket for the cache entry that holds the non-conservative power calculation. More... | |
| Protected Member Functions inherited from MultibodyTreeSystem< T > | |
| void | SetDefaultState (const systems::Context< T > &context, systems::State< T > *state) const override |
| MultibodyTreeSystem (bool is_discrete=false) | |
| Default constructor allocates a MultibodyTree, with the intent that it will be filled in later, using mutable_tree() for access. More... | |
| MultibodyTreeSystem (systems::SystemScalarConverter converter, std::unique_ptr< MultibodyTree< T >> tree, bool is_discrete=false) | |
| Constructor that specifies scalar-type conversion support. More... | |
| const MultibodyTree< T > & | internal_tree () const |
| Returns a const reference to the MultibodyTree owned by this class. More... | |
| MultibodyTree< T > & | mutable_tree () const |
| Returns a mutable reference to the MultibodyTree owned by this class. More... | |
| void | Finalize () |
| Finalize the tree if that hasn't already been done, complete System construction, and declare any needed Context resources for the tree. More... | |
| Protected Member Functions inherited from LeafSystem< T > | |
| LeafSystem () | |
| Default constructor that declares no inputs, outputs, state, parameters, events, nor scalar-type conversion support (AutoDiff, etc.). More... | |
| LeafSystem (SystemScalarConverter converter) | |
| Constructor that declares no inputs, outputs, state, parameters, or events, but allows subclasses to declare scalar-type conversion support (AutoDiff, etc.). More... | |
| virtual std::unique_ptr< LeafContext< T > > | DoMakeLeafContext () const |
| Provides a new instance of the leaf context for this system. More... | |
| virtual void | DoValidateAllocatedLeafContext (const LeafContext< T > &context) const |
| Derived classes that impose restrictions on what resources are permitted should check those restrictions by implementing this. More... | |
| T | DoCalcWitnessValue (const Context< T > &context, const WitnessFunction< T > &witness_func) const final |
| Derived classes will implement this method to evaluate a witness function at the given context. More... | |
| void | AddTriggeredWitnessFunctionToCompositeEventCollection (Event< T > *event, CompositeEventCollection< T > *events) const final |
Add event to events due to a witness function triggering. More... | |
| void | DoCalcNextUpdateTime (const Context< T > &context, CompositeEventCollection< T > *events, T *time) const override |
| Computes the next update time based on the configured periodic events, for scalar types that are arithmetic, or aborts for scalar types that are not arithmetic. More... | |
| void | GetGraphvizFragment (int max_depth, std::stringstream *dot) const override |
| Emits a graphviz fragment for this System. More... | |
| void | GetGraphvizInputPortToken (const InputPort< T > &port, int max_depth, std::stringstream *dot) const final |
Appends a fragment to the dot stream identifying the graphviz node representing port. More... | |
| void | GetGraphvizOutputPortToken (const OutputPort< T > &port, int max_depth, std::stringstream *dot) const final |
Appends a fragment to the dot stream identifying the graphviz node representing port. More... | |
| virtual std::unique_ptr< ContinuousState< T > > | AllocateContinuousState () const |
| Returns a ContinuousState used to implement both CreateDefaultContext and AllocateTimeDerivatives. More... | |
| virtual std::unique_ptr< DiscreteValues< T > > | AllocateDiscreteState () const |
| Reserves the discrete state as required by CreateDefaultContext. More... | |
| virtual std::unique_ptr< AbstractValues > | AllocateAbstractState () const |
| Reserves the abstract state as required by CreateDefaultContext. More... | |
| virtual std::unique_ptr< Parameters< T > > | AllocateParameters () const |
| Reserves the parameters as required by CreateDefaultContext. More... | |
| int | DeclareNumericParameter (const BasicVector< T > &model_vector) |
Declares a numeric parameter using the given model_vector. More... | |
| template<template< typename > class U = BasicVector> | |
| const U< T > & | GetNumericParameter (const Context< T > &context, int index) const |
Extracts the numeric parameters of type U from the context at index. More... | |
| template<template< typename > class U = BasicVector> | |
| U< T > & | GetMutableNumericParameter (Context< T > *context, int index) const |
Extracts the numeric parameters of type U from the context at index. More... | |
| int | DeclareAbstractParameter (const AbstractValue &model_value) |
Declares an abstract parameter using the given model_value. More... | |
| template<class MySystem > | |
| SystemConstraintIndex | DeclareEqualityConstraint (void(MySystem::*calc)(const Context< T > &, VectorX< T > *) const, int count, std::string description) |
| Declares a system constraint of the form f(context) = 0 by specifying a member function to use to calculate the (VectorX) constraint value with a signature: More... | |
| SystemConstraintIndex | DeclareEqualityConstraint (ContextConstraintCalc< T > calc, int count, std::string description) |
| Declares a system constraint of the form f(context) = 0 by specifying a std::function to use to calculate the (Vector) constraint value with a signature: More... | |
| template<class MySystem > | |
| SystemConstraintIndex | DeclareInequalityConstraint (void(MySystem::*calc)(const Context< T > &, VectorX< T > *) const, SystemConstraintBounds bounds, std::string description) |
| Declares a system constraint of the form bounds.lower() <= calc(context) <= bounds.upper() by specifying a member function to use to calculate the (VectorX) constraint value with a signature: More... | |
| SystemConstraintIndex | DeclareInequalityConstraint (ContextConstraintCalc< T > calc, SystemConstraintBounds bounds, std::string description) |
| Declares a system constraint of the form bounds.lower() <= calc(context) <= bounds.upper() by specifying a std::function to use to calculate the (Vector) constraint value with a signature: More... | |
| virtual void | DoPublish (const Context< T > &context, const std::vector< const PublishEvent< T > * > &events) const |
Derived-class event dispatcher for all simultaneous publish events in events. More... | |
| virtual void | DoCalcDiscreteVariableUpdates (const Context< T > &context, const std::vector< const DiscreteUpdateEvent< T > * > &events, DiscreteValues< T > *discrete_state) const |
| Derived-class event dispatcher for all simultaneous discrete update events. More... | |
| virtual void | DoCalcUnrestrictedUpdate (const Context< T > &context, const std::vector< const UnrestrictedUpdateEvent< T > * > &events, State< T > *state) const |
| Derived-class event dispatcher for all simultaneous unrestricted update events. More... | |
| template<class MySystem > | |
| void | DeclarePeriodicPublishEvent (double period_sec, double offset_sec, EventStatus(MySystem::*publish)(const Context< T > &) const) |
| Declares that a Publish event should occur periodically and that it should invoke the given event handler method. More... | |
| template<class MySystem > | |
| void | DeclarePeriodicPublishEvent (double period_sec, double offset_sec, void(MySystem::*publish)(const Context< T > &) const) |
| This variant accepts a handler that is assumed to succeed rather than one that returns an EventStatus result. More... | |
| template<class MySystem > | |
| void | DeclarePeriodicDiscreteUpdateEvent (double period_sec, double offset_sec, EventStatus(MySystem::*update)(const Context< T > &, DiscreteValues< T > *) const) |
| Declares that a DiscreteUpdate event should occur periodically and that it should invoke the given event handler method. More... | |
| template<class MySystem > | |
| void | DeclarePeriodicDiscreteUpdateEvent (double period_sec, double offset_sec, void(MySystem::*update)(const Context< T > &, DiscreteValues< T > *) const) |
| This variant accepts a handler that is assumed to succeed rather than one that returns an EventStatus result. More... | |
| template<class MySystem > | |
| void | DeclarePeriodicUnrestrictedUpdateEvent (double period_sec, double offset_sec, EventStatus(MySystem::*update)(const Context< T > &, State< T > *) const) |
| Declares that an UnrestrictedUpdate event should occur periodically and that it should invoke the given event handler method. More... | |
| template<class MySystem > | |
| void | DeclarePeriodicUnrestrictedUpdateEvent (double period_sec, double offset_sec, void(MySystem::*update)(const Context< T > &, State< T > *) const) |
| This variant accepts a handler that is assumed to succeed rather than one that returns an EventStatus result. More... | |
| template<typename EventType > | |
| void | DeclarePeriodicEvent (double period_sec, double offset_sec, const EventType &event) |
| (Advanced) Declares that a particular Event object should be dispatched periodically. More... | |
| void | DeclarePeriodicPublish (double period_sec, double offset_sec=0) |
| (To be deprecated) Declares a periodic publish event that invokes the Publish() dispatcher but does not provide a handler function. More... | |
| void | DeclarePeriodicDiscreteUpdate (double period_sec, double offset_sec=0) |
| (To be deprecated) Declares a periodic discrete update event that invokes the DiscreteUpdate() dispatcher but does not provide a handler function. More... | |
| void | DeclarePeriodicUnrestrictedUpdate (double period_sec, double offset_sec=0) |
| (To be deprecated) Declares a periodic unrestricted update event that invokes the UnrestrictedUpdate() dispatcher but does not provide a handler function. More... | |
| template<class MySystem > | |
| void | DeclarePerStepPublishEvent (EventStatus(MySystem::*publish)(const Context< T > &) const) |
| Declares that a Publish event should occur at initialization and at the end of every trajectory-advancing step and that it should invoke the given event handler method. More... | |
| template<class MySystem > | |
| void | DeclarePerStepDiscreteUpdateEvent (EventStatus(MySystem::*update)(const Context< T > &, DiscreteValues< T > *) const) |
| Declares that a DiscreteUpdate event should occur at the start of every trajectory-advancing step and that it should invoke the given event handler method. More... | |
| template<class MySystem > | |
| void | DeclarePerStepUnrestrictedUpdateEvent (EventStatus(MySystem::*update)(const Context< T > &, State< T > *) const) |
| Declares that an UnrestrictedUpdate event should occur at the start of every trajectory-advancing step and that it should invoke the given event handler method. More... | |
| template<typename EventType > | |
| void | DeclarePerStepEvent (const EventType &event) |
| (Advanced) Declares that a particular Event object should be dispatched at every trajectory-advancing step. More... | |
| template<class MySystem > | |
| void | DeclareInitializationPublishEvent (EventStatus(MySystem::*publish)(const Context< T > &) const) |
| Declares that a Publish event should occur at initialization and that it should invoke the given event handler method. More... | |
| template<class MySystem > | |
| void | DeclareInitializationDiscreteUpdateEvent (EventStatus(MySystem::*update)(const Context< T > &, DiscreteValues< T > *) const) |
| Declares that a DiscreteUpdate event should occur at initialization and that it should invoke the given event handler method. More... | |
| template<class MySystem > | |
| void | DeclareInitializationUnrestrictedUpdateEvent (EventStatus(MySystem::*update)(const Context< T > &, State< T > *) const) |
| Declares that an UnrestrictedUpdate event should occur at initialization and that it should invoke the given event handler method. More... | |
| template<typename EventType > | |
| void | DeclareInitializationEvent (const EventType &event) |
| (Advanced) Declares that a particular Event object should be dispatched at initialization. More... | |
| template<class MySystem > | |
| void | DeclareForcedPublishEvent (EventStatus(MySystem::*publish)(const Context< T > &) const) |
| Declares a function that is called whenever a user directly calls Publish(const Context&). More... | |
| template<class MySystem > | |
| void | DeclareForcedDiscreteUpdateEvent (EventStatus(MySystem::*update)(const Context< T > &, DiscreteValues< T > *) const) |
| Declares a function that is called whenever a user directly calls CalcDiscreteVariableUpdates(const Context&, DiscreteValues<T>*). More... | |
| template<class MySystem > | |
| void | DeclareForcedUnrestrictedUpdateEvent (EventStatus(MySystem::*update)(const Context< T > &, State< T > *) const) |
| Declares a function that is called whenever a user directly calls CalcUnrestrictedUpdate(const Context&, State<T>*). More... | |
| void | DeclareContinuousState (int num_state_variables) |
Declares that this System should reserve continuous state with num_state_variables state variables, which have no second-order structure. More... | |
| void | DeclareContinuousState (int num_q, int num_v, int num_z) |
Declares that this System should reserve continuous state with num_q generalized positions, num_v generalized velocities, and num_z miscellaneous state variables. More... | |
| void | DeclareContinuousState (const BasicVector< T > &model_vector) |
Declares that this System should reserve continuous state with model_vector.size() miscellaneous state variables, stored in a vector cloned from model_vector. More... | |
| void | DeclareContinuousState (const BasicVector< T > &model_vector, int num_q, int num_v, int num_z) |
Declares that this System should reserve continuous state with num_q generalized positions, num_v generalized velocities, and num_z miscellaneous state variables, stored in a vector cloned from model_vector. More... | |
| DiscreteStateIndex | DeclareDiscreteState (const BasicVector< T > &model_vector) |
Declares a discrete state group with model_vector.size() state variables, stored in a vector cloned from model_vector (preserving the concrete type and value). More... | |
| DiscreteStateIndex | DeclareDiscreteState (const Eigen::Ref< const VectorX< T >> &vector) |
Declares a discrete state group with vector.size() state variables, stored in a BasicVector initialized with the contents of vector. More... | |
| DiscreteStateIndex | DeclareDiscreteState (int num_state_variables) |
Declares a discrete state group with num_state_variables state variables, stored in a BasicVector initialized to be all-zero. More... | |
| AbstractStateIndex | DeclareAbstractState (std::unique_ptr< AbstractValue > abstract_state) |
| Declares an abstract state. More... | |
| const InputPort< T > & | DeclareVectorInputPort (variant< std::string, UseDefaultName > name, const BasicVector< T > &model_vector, optional< RandomDistribution > random_type=nullopt) |
Declares a vector-valued input port using the given model_vector. More... | |
| const InputPort< T > & | DeclareAbstractInputPort (variant< std::string, UseDefaultName > name, const AbstractValue &model_value) |
Declares an abstract-valued input port using the given model_value. More... | |
| const InputPort< T > & | DeclareVectorInputPort (const BasicVector< T > &model_vector, optional< RandomDistribution > random_type=nullopt) |
| See the nearly identical signature with an additional (first) argument specifying the port name. More... | |
| const InputPort< T > & | DeclareAbstractInputPort (const AbstractValue &model_value) |
| See the nearly identical signature with an additional (first) argument specifying the port name. More... | |
| template<class MySystem , typename BasicVectorSubtype > | |
| const OutputPort< T > & | DeclareVectorOutputPort (variant< std::string, UseDefaultName > name, const BasicVectorSubtype &model_vector, void(MySystem::*calc)(const Context< T > &, BasicVectorSubtype *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares a vector-valued output port by specifying (1) a model vector of type BasicVectorSubtype derived from BasicVector and initialized to the correct size and desired initial value, and (2) a calculator function that is a class member function (method) with signature: More... | |
| template<class MySystem , typename BasicVectorSubtype > | |
| const OutputPort< T > & | DeclareVectorOutputPort (variant< std::string, UseDefaultName > name, void(MySystem::*calc)(const Context< T > &, BasicVectorSubtype *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares a vector-valued output port by specifying only a calculator function that is a class member function (method) with signature: More... | |
| const OutputPort< T > & | DeclareVectorOutputPort (variant< std::string, UseDefaultName > name, const BasicVector< T > &model_vector, typename LeafOutputPort< T >::CalcVectorCallback vector_calc_function, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
(Advanced) Declares a vector-valued output port using the given model_vector and a function for calculating the port's value at runtime. More... | |
| template<class MySystem , typename OutputType > | |
| const OutputPort< T > & | DeclareAbstractOutputPort (variant< std::string, UseDefaultName > name, const OutputType &model_value, void(MySystem::*calc)(const Context< T > &, OutputType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
Declares an abstract-valued output port by specifying a model value of concrete type OutputType and a calculator function that is a class member function (method) with signature: More... | |
| template<class MySystem , typename OutputType > | |
| const OutputPort< T > & | DeclareAbstractOutputPort (variant< std::string, UseDefaultName > name, void(MySystem::*calc)(const Context< T > &, OutputType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares an abstract-valued output port by specifying only a calculator function that is a class member function (method) with signature: More... | |
| template<class MySystem , typename OutputType > | |
| const OutputPort< T > & | DeclareAbstractOutputPort (variant< std::string, UseDefaultName > name, OutputType(MySystem::*make)() const, void(MySystem::*calc)(const Context< T > &, OutputType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| Declares an abstract-valued output port by specifying member functions to use both for the allocator and calculator. More... | |
| const OutputPort< T > & | DeclareAbstractOutputPort (variant< std::string, UseDefaultName > name, typename LeafOutputPort< T >::AllocCallback alloc_function, typename LeafOutputPort< T >::CalcCallback calc_function, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| (Advanced) Declares an abstract-valued output port using the given allocator and calculator functions provided in their most generic forms. More... | |
| template<class MySystem , typename BasicVectorSubtype > | |
| const OutputPort< T > & | DeclareVectorOutputPort (const BasicVectorSubtype &model_vector, void(MySystem::*calc)(const Context< T > &, BasicVectorSubtype *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| See the nearly identical signature with an additional (first) argument specifying the port name. More... | |
| template<class MySystem , typename BasicVectorSubtype > | |
| const OutputPort< T > & | DeclareVectorOutputPort (void(MySystem::*calc)(const Context< T > &, BasicVectorSubtype *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| See the nearly identical signature with an additional (first) argument specifying the port name. More... | |
| const OutputPort< T > & | DeclareVectorOutputPort (const BasicVector< T > &model_vector, typename LeafOutputPort< T >::CalcVectorCallback vector_calc_function, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| See the nearly identical signature with an additional (first) argument specifying the port name. More... | |
| template<class MySystem , typename OutputType > | |
| std::enable_if_t<!std::is_same< OutputType, std::string >::value, const OutputPort< T > & > | DeclareAbstractOutputPort (const OutputType &model_value, void(MySystem::*calc)(const Context< T > &, OutputType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| See the nearly identical signature with an additional (first) argument specifying the port name. More... | |
| template<class MySystem , typename OutputType > | |
| const OutputPort< T > & | DeclareAbstractOutputPort (void(MySystem::*calc)(const Context< T > &, OutputType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| See the nearly identical signature with an additional (first) argument specifying the port name. More... | |
| template<class MySystem , typename OutputType > | |
| const OutputPort< T > & | DeclareAbstractOutputPort (OutputType(MySystem::*make)() const, void(MySystem::*calc)(const Context< T > &, OutputType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| See the nearly identical signature with an additional (first) argument specifying the port name. More... | |
| const OutputPort< T > & | DeclareAbstractOutputPort (typename LeafOutputPort< T >::AllocCallback alloc_function, typename LeafOutputPort< T >::CalcCallback calc_function, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| See the nearly identical signature with an additional (first) argument specifying the port name. More... | |
| template<class MySystem > | |
| std::unique_ptr< WitnessFunction< T > > | MakeWitnessFunction (const std::string &description, const WitnessFunctionDirection &direction_type, T(MySystem::*calc)(const Context< T > &) const) const |
| Constructs the witness function with the given description (used primarily for debugging and logging), direction type, and calculator function; and with no event object. More... | |
| std::unique_ptr< WitnessFunction< T > > | MakeWitnessFunction (const std::string &description, const WitnessFunctionDirection &direction_type, std::function< T(const Context< T > &)> calc) const |
| Constructs the witness function with the given description (used primarily for debugging and logging), direction type, and calculator function; and with no event object. More... | |
| template<class MySystem > | |
| std::unique_ptr< WitnessFunction< T > > | MakeWitnessFunction (const std::string &description, const WitnessFunctionDirection &direction_type, T(MySystem::*calc)(const Context< T > &) const, void(MySystem::*publish_callback)(const Context< T > &, const PublishEvent< T > &) const) const |
| Constructs the witness function with the given description (used primarily for debugging and logging), direction type, calculator function, and publish event callback function for when this triggers. More... | |
| template<class MySystem > | |
| std::unique_ptr< WitnessFunction< T > > | MakeWitnessFunction (const std::string &description, const WitnessFunctionDirection &direction_type, T(MySystem::*calc)(const Context< T > &) const, void(MySystem::*du_callback)(const Context< T > &, const DiscreteUpdateEvent< T > &, DiscreteValues< T > *) const) const |
| Constructs the witness function with the given description (used primarily for debugging and logging), direction type, calculator function, and discrete update event callback function for when this triggers. More... | |
| template<class MySystem > | |
| std::unique_ptr< WitnessFunction< T > > | MakeWitnessFunction (const std::string &description, const WitnessFunctionDirection &direction_type, T(MySystem::*calc)(const Context< T > &) const, void(MySystem::*uu_callback)(const Context< T > &, const UnrestrictedUpdateEvent< T > &, State< T > *) const) const |
| Constructs the witness function with the given description (used primarily for debugging and logging), direction type, calculator function, and unrestricted update event callback function for when this triggers. More... | |
| template<class MySystem > | |
| std::unique_ptr< WitnessFunction< T > > | MakeWitnessFunction (const std::string &description, const WitnessFunctionDirection &direction_type, T(MySystem::*calc)(const Context< T > &) const, const Event< T > &e) const |
| Constructs the witness function with the given description (used primarily for debugging and logging), direction type, and calculator function, and with an object corresponding to the event that is to be dispatched when this witness function triggers. More... | |
| std::unique_ptr< WitnessFunction< T > > | MakeWitnessFunction (const std::string &description, const WitnessFunctionDirection &direction_type, std::function< T(const Context< T > &)> calc, const Event< T > &e) const |
| Constructs the witness function with the given description (used primarily for debugging and logging), direction type, and calculator function, and with an object corresponding to the event that is to be dispatched when this witness function triggers. More... | |
| Protected Member Functions inherited from System< T > | |
| virtual void | DoGetWitnessFunctions (const Context< T > &, std::vector< const WitnessFunction< T > * > *) const |
| Derived classes can override this method to provide witness functions active for the given state. More... | |
| SystemConstraintIndex | AddConstraint (std::unique_ptr< SystemConstraint< T >> constraint) |
| Adds an already-created constraint to the list of constraints for this System. More... | |
| bool | forced_publish_events_exist () const |
| bool | forced_discrete_update_events_exist () const |
| bool | forced_unrestricted_update_events_exist () const |
| EventCollection< PublishEvent< T > > & | get_mutable_forced_publish_events () |
| EventCollection< DiscreteUpdateEvent< T > > & | get_mutable_forced_discrete_update_events () |
| EventCollection< UnrestrictedUpdateEvent< T > > & | get_mutable_forced_unrestricted_update_events () |
| const EventCollection< PublishEvent< T > > & | get_forced_publish_events () const |
| const EventCollection< DiscreteUpdateEvent< T > > & | get_forced_discrete_update_events () const |
| const EventCollection< UnrestrictedUpdateEvent< T > > & | get_forced_unrestricted_update_events () const |
| void | set_forced_publish_events (std::unique_ptr< EventCollection< PublishEvent< T >>> forced) |
| void | set_forced_discrete_update_events (std::unique_ptr< EventCollection< DiscreteUpdateEvent< T >>> forced) |
| void | set_forced_unrestricted_update_events (std::unique_ptr< EventCollection< UnrestrictedUpdateEvent< T >>> forced) |
| System (SystemScalarConverter converter) | |
Constructs an empty System base class object and allocates base class resources, possibly supporting scalar-type conversion support (AutoDiff, etc.) using converter. More... | |
| const InputPort< T > & | DeclareInputPort (variant< std::string, UseDefaultName > name, PortDataType type, int size, optional< RandomDistribution > random_type=nullopt) |
Adds a port with the specified type and size to the input topology. More... | |
| const InputPort< T > & | DeclareInputPort (PortDataType type, int size, optional< RandomDistribution > random_type=nullopt) |
| See the nearly identical signature with an additional (first) argument specifying the port name. More... | |
| virtual void | DoCalcTimeDerivatives (const Context< T > &context, ContinuousState< T > *derivatives) const |
Override this if you have any continuous state variables xc in your concrete System to calculate their time derivatives. More... | |
| virtual T | DoCalcPotentialEnergy (const Context< T > &context) const |
| Override this method for physical systems to calculate the potential energy PE currently stored in the configuration provided in the given Context. More... | |
| virtual T | DoCalcKineticEnergy (const Context< T > &context) const |
| Override this method for physical systems to calculate the kinetic energy KE currently present in the motion provided in the given Context. More... | |
| virtual T | DoCalcConservativePower (const Context< T > &context) const |
| Override this method to return the rate Pc at which mechanical energy is being converted from potential energy to kinetic energy by this system in the given Context. More... | |
| virtual T | DoCalcNonConservativePower (const Context< T > &context) const |
| Override this method to return the rate Pnc at which work W is done on the system by non-conservative forces. More... | |
| virtual void | DoMapQDotToVelocity (const Context< T > &context, const Eigen::Ref< const VectorX< T >> &qdot, VectorBase< T > *generalized_velocity) const |
| Provides the substantive implementation of MapQDotToVelocity(). More... | |
| virtual void | DoMapVelocityToQDot (const Context< T > &context, const Eigen::Ref< const VectorX< T >> &generalized_velocity, VectorBase< T > *qdot) const |
| Provides the substantive implementation of MapVelocityToQDot(). More... | |
| virtual int | do_get_num_constraint_equations (const Context< T > &context) const |
| Gets the number of constraint equations for this system from the given context. More... | |
| virtual Eigen::VectorXd | DoEvalConstraintEquations (const Context< T > &context) const |
| Evaluates the constraint equations for the system at the generalized coordinates and generalized velocity specified by the context. More... | |
| virtual Eigen::VectorXd | DoEvalConstraintEquationsDot (const Context< T > &context) const |
| Computes the time derivative of each constraint equation, evaluated at the generalized coordinates and generalized velocity specified by the context. More... | |
| virtual Eigen::VectorXd | DoCalcVelocityChangeFromConstraintImpulses (const Context< T > &context, const Eigen::MatrixXd &J, const Eigen::VectorXd &lambda) const |
| Computes the change in velocity from applying the given constraint forces to the system at the given context. More... | |
| virtual double | DoCalcConstraintErrorNorm (const Context< T > &context, const Eigen::VectorXd &error) const |
| Computes the norm of the constraint error. More... | |
| Eigen::VectorBlock< VectorX< T > > | GetMutableOutputVector (SystemOutput< T > *output, int port_index) const |
Returns a mutable Eigen expression for a vector valued output port with index port_index in this system. More... | |
| Protected Member Functions inherited from SystemBase | |
| SystemBase ()=default | |
| (Internal use only) Default constructor. More... | |
| void | AddInputPort (std::unique_ptr< InputPortBase > port) |
| (Internal use only) Adds an already-constructed input port to this System. More... | |
| void | AddOutputPort (std::unique_ptr< OutputPortBase > port) |
| (Internal use only) Adds an already-constructed output port to this System. More... | |
| std::string | NextInputPortName (variant< std::string, UseDefaultName > given_name) const |
| (Internal use only) Returns a name for the next input port, using the given name if it isn't kUseDefaultName, otherwise making up a name like "u3" from the next available input port index. More... | |
| std::string | NextOutputPortName (variant< std::string, UseDefaultName > given_name) const |
| (Internal use only) Returns a name for the next output port, using the given name if it isn't kUseDefaultName, otherwise making up a name like "y3" from the next available output port index. More... | |
| void | AddDiscreteStateGroup (DiscreteStateIndex index) |
(Internal use only) Assigns a ticket to a new discrete variable group with the given index. More... | |
| void | AddAbstractState (AbstractStateIndex index) |
(Internal use only) Assigns a ticket to a new abstract state variable with the given index. More... | |
| void | AddNumericParameter (NumericParameterIndex index) |
(Internal use only) Assigns a ticket to a new numeric parameter with the given index. More... | |
| void | AddAbstractParameter (AbstractParameterIndex index) |
(Internal use only) Assigns a ticket to a new abstract parameter with the given index. More... | |
| const CacheEntry & | DeclareCacheEntryWithKnownTicket (DependencyTicket known_ticket, std::string description, CacheEntry::AllocCallback alloc_function, CacheEntry::CalcCallback calc_function, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()}) |
| (Internal use only) This is for cache entries associated with pre-defined tickets, for example the cache entry for time derivatives. More... | |
| const internal::SystemParentServiceInterface * | get_parent_service () const |
| Returns a pointer to the service interface of the immediately enclosing Diagram if one has been set, otherwise nullptr. More... | |
| DependencyTicket | assign_next_dependency_ticket () |
| (Internal use only) Assigns the next unused dependency ticket number, unique only within a particular system. More... | |
| const AbstractValue * | EvalAbstractInputImpl (const char *func, const ContextBase &context, InputPortIndex port_index) const |
| (Internal use only) Shared code for updating an input port and returning a pointer to its abstract value, or nullptr if the port is not connected. More... | |
| void | ThrowNegativePortIndex (const char *func, int port_index) const |
Throws std::out_of_range to report a negative port_index that was passed to API method func. More... | |
| void | ThrowInputPortIndexOutOfRange (const char *func, InputPortIndex port_index) const |
Throws std::out_of_range to report bad input port_index that was passed to API method func. More... | |
| void | ThrowOutputPortIndexOutOfRange (const char *func, OutputPortIndex port_index) const |
Throws std::out_of_range to report bad output port_index that was passed to API method func. More... | |
| void | ThrowNotAVectorInputPort (const char *func, InputPortIndex port_index) const |
Throws std::logic_error because someone misused API method func, that is only allowed for declared-vector input ports, on an abstract port whose index is given here. More... | |
| void | ThrowInputPortHasWrongType (const char *func, InputPortIndex port_index, const std::string &expected_type, const std::string &actual_type) const |
Throws std::logic_error because someone called API method func claiming the input port had some value type that was wrong. More... | |
| void | ThrowCantEvaluateInputPort (const char *func, InputPortIndex port_index) const |
Throws std::logic_error because someone called API method func, that requires this input port to be evaluatable, but the port was neither fixed nor connected. More... | |
| const InputPortBase & | GetInputPortBaseOrThrow (const char *func, int port_index) const |
(Internal use only) Returns the InputPortBase at index port_index, throwing std::out_of_range we don't like the port index. More... | |
| const OutputPortBase & | GetOutputPortBaseOrThrow (const char *func, int port_index) const |
(Internal use only) Returns the OutputPortBase at index port_index, throwing std::out_of_range if we don't like the port index. More... | |
| void | InitializeContextBase (ContextBase *context) const |
| This method must be invoked from within derived class DoAllocateContext() implementations right after the concrete Context object has been allocated. More... | |
| Static Protected Member Functions inherited from LeafSystem< T > | |
| static DependencyTicket | all_sources_ticket () |
| Returns a ticket indicating dependence on every possible independent source value, including time, accuracy, state, input ports, and parameters (but not cache entries). More... | |
| Static Protected Member Functions inherited from SystemBase | |
| static void | set_parent_service (SystemBase *child, const internal::SystemParentServiceInterface *parent_service) |
(Internal use only) Declares that parent_service is the service interface of the Diagram that owns this subsystem. More... | |
| static void | ThrowInputPortHasWrongType (const char *func, const std::string &system_pathname, InputPortIndex, const std::string &port_name, const std::string &expected_type, const std::string &actual_type) |
Throws std::logic_error because someone called API method func claiming the input port had some value type that was wrong. More... | |
Constructor & Destructor Documentation
◆ MultibodyPlant() [1/4]
|
delete |
◆ MultibodyPlant() [2/4]
|
delete |
◆ MultibodyPlant() [3/4]
|
explicit |
Default constructor creates a plant with a single "world" body.
Therefore, right after creation, num_bodies() returns one.
- Parameters
-
[in] time_step An optional parameter indicating whether thisplant is modeled as a continuous system (time_step = 0) or as a discrete system with periodic updates of periodtime_step > 0.
Default: 0.0.
- Exceptions
-
std::exception if time_stepis negative.
◆ MultibodyPlant() [4/4]
| MultibodyPlant | ( | const MultibodyPlant< U > & | other | ) |
Scalar-converting copy constructor. See System Scalar Conversion.
Member Function Documentation
◆ AddForceElement()
| const ForceElementType<T>& AddForceElement | ( | Args &&... | args | ) |
Adds a new force element model of type ForceElementType to this MultibodyPlant.
The arguments to this method args are forwarded to ForceElementType's constructor.
- Parameters
-
[in] args Zero or more parameters provided to the constructor of the new force element. It must be the case that ForceElementType<T>(args)is a valid constructor.
- Template Parameters
-
ForceElementType The type of the ForceElement to add. As there is always a UniformGravityFieldElement present (accessible through gravity_field()), an exception will be thrown if this function is called to add another UniformGravityFieldElement. As there was not always a default gravity field element, for compatibility purposes calling this function to add a UniformGravityFieldElement which has the same value as gravity_field() is not an error.
- Returns
- A constant reference to the new ForceElement just added, of type
ForceElementType<T>specialized on the scalar type T ofthisMultibodyPlant. It will remain valid for the lifetime ofthisMultibodyPlant.
- See also
- The ForceElement class's documentation for further details on how a force element is defined.
◆ AddFrame()
| const FrameType<T>& AddFrame | ( | std::unique_ptr< FrameType< T >> | frame | ) |
This method adds a Frame of type FrameType<T>.
For more information, please see the corresponding constructor of FrameType.
- Template Parameters
-
FrameType Template which will be instantiated on T.
- Parameters
-
frame Unique pointer frame instance.
- Returns
- A constant reference to the new Frame just added, which will remain valid for the lifetime of
thisMultibodyPlant.
◆ AddJoint() [1/2]
| const JointType<T>& AddJoint | ( | std::unique_ptr< JointType< T >> | joint | ) |
This method adds a Joint of type JointType between two bodies.
For more information, see the below overload of AddJoint<>, and the related MultibodyTree::AddJoint<> method.
◆ AddJoint() [2/2]
| const JointType<T>& AddJoint | ( | const std::string & | name, |
| const Body< T > & | parent, | ||
| const optional< math::RigidTransform< double >> & | X_PF, | ||
| const Body< T > & | child, | ||
| const optional< math::RigidTransform< double >> & | X_BM, | ||
| Args &&... | args | ||
| ) |
This method adds a Joint of type JointType between two bodies.
The two bodies connected by this Joint object are referred to as the parent and child bodies. Although the terms parent and child are sometimes used synonymously to describe the relationship between inboard and outboard bodies in multibody models, this usage is wholly unrelated and implies nothing about the inboard-outboard relationship between the bodies. As explained in the Joint class's documentation, in Drake we define a frame F attached to the parent body P with pose X_PF and a frame M attached to the child body B with pose X_BM. This method helps creating a joint between two bodies with fixed poses X_PF and X_BM. Refer to the Joint class's documentation for more details.
- Parameters
-
name A string that uniquely identifies the new joint to be added to thismodel. A std::runtime_error is thrown if a joint namednamealready is part of the model. See HasJointNamed(), Joint::name().[in] parent The parent body connected by the new joint. [in] X_PF The fixed pose of frame F attached to the parent body, measured in the frame P of that body. X_PFis an optional parameter; empty curly braces{}imply that frame F is the same body frame P. If instead your intention is to make a frame F with poseX_PFequal to the identity pose, provideRigidTransform<double>::Identity()as your input.[in] child The child body connected by the new joint. [in] X_BM The fixed pose of frame M attached to the child body, measured in the frame B of that body. X_BMis an optional parameter; empty curly braces{}imply that frame M is the same body frame B. If instead your intention is to make a frame M with poseX_BMequal to the identity pose, provideRigidTransform<double>::Identity()as your input.[in] args Zero or more parameters provided to the constructor of the new joint. It must be the case that JointType<T>( const std::string&, const Frame<T>&, const Frame<T>&, args)is a valid constructor.
- Template Parameters
-
JointType The type of the Joint to add.
- Returns
- A constant reference to the new joint just added, of type
JointType<T>specialized on the scalar type T ofthisMultibodyPlant. It will remain valid for the lifetime ofthisMultibodyPlant.
Example of usage:
- Exceptions
-
std::exception if thisMultibodyPlant already contains a joint with the givenname. See HasJointNamed(), Joint::name().
◆ AddJointActuator()
| const JointActuator<T>& AddJointActuator | ( | const std::string & | name, |
| const Joint< T > & | joint, | ||
| double | effort_limit = std::numeric_limits<double>::infinity() |
||
| ) |
Creates and adds a JointActuator model for an actuator acting on a given joint.
This method returns a constant reference to the actuator just added, which will remain valid for the lifetime of this plant.
- Parameters
-
[in] name A string that uniquely identifies the new actuator to be added to thismodel. A std::runtime_error is thrown if an actuator with the same name already exists in the model. See HasJointActuatorNamed().[in] joint The Joint to be actuated by the new JointActuator. [in] effort_limit The maximum effort for the actuator. It must be strictly positive, otherwise an std::exception is thrown. If +∞, the actuator has no limit, which is the default. The effort limit has physical units in accordance to the joint type it actuates. For instance, it will have units of N⋅m (torque) for revolute joints while it will have units of N (force) for prismatic joints.
- Returns
- A constant reference to the new JointActuator just added, which will remain valid for the lifetime of
thisplant.
- Exceptions
-
std::exception if joint.num_velocities() > 1since for now we only support actuators for single dof joints.
◆ AddModelInstance()
| ModelInstanceIndex AddModelInstance | ( | const std::string & | name | ) |
Creates a new model instance.
Returns the index for the model instance.
- Parameters
-
[in] name A string that uniquely identifies the new instance to be added to thismodel. An exception is thrown if an instance with the same name already exists in the model. See HasModelInstanceNamed().
◆ AddRigidBody() [1/2]
| const RigidBody<T>& AddRigidBody | ( | const std::string & | name, |
| ModelInstanceIndex | model_instance, | ||
| const SpatialInertia< double > & | M_BBo_B | ||
| ) |
Creates a rigid body with the provided name and spatial inertia.
This method returns a constant reference to the body just added, which will remain valid for the lifetime of this MultibodyPlant.
Example of usage:
- Parameters
-
[in] name A string that identifies the new body to be added to thismodel. A std::runtime_error is thrown if a body namednamealready is part ofmodel_instance. See HasBodyNamed(), Body::name().[in] model_instance A model instance index which this body is part of. [in] M_BBo_B The SpatialInertia of the new rigid body to be added to thisMultibodyPlant, computed about the body frame originBoand expressed in the body frame B.
- Returns
- A constant reference to the new RigidBody just added, which will remain valid for the lifetime of
thisMultibodyPlant.
◆ AddRigidBody() [2/2]
| const RigidBody<T>& AddRigidBody | ( | const std::string & | name, |
| const SpatialInertia< double > & | M_BBo_B | ||
| ) |
Creates a rigid body with the provided name and spatial inertia.
This method returns a constant reference to the body just added, which will remain valid for the lifetime of this MultibodyPlant. The body will use the default model instance (more on model instances).
Example of usage:
- Parameters
-
[in] name A string that identifies the new body to be added to thismodel. A std::runtime_error is thrown if a body namednamealready is part of the model in the default model instance. See HasBodyNamed(), Body::name().[in] M_BBo_B The SpatialInertia of the new rigid body to be added to thisMultibodyPlant, computed about the body frame originBoand expressed in the body frame B.
- Returns
- A constant reference to the new RigidBody just added, which will remain valid for the lifetime of
thisMultibodyPlant.
- Exceptions
-
std::logic_error if additional model instances have been created beyond the world and default instances.
◆ CalcBiasForFrameGeometricJacobianExpressedInWorld()
| Vector6<T> CalcBiasForFrameGeometricJacobianExpressedInWorld | ( | const systems::Context< T > & | context, |
| const Frame< T > & | frame_F, | ||
| const Eigen::Ref< const Vector3< T >> & | p_FP | ||
| ) | const |
Given a frame Fp defined by shifting a frame F from its origin Fo to a new origin P, this method computes the bias term Ab_WFp associated with the spatial acceleration A_WFp a frame Fp instantaneously moving with a frame F at a fixed position p_FP.
That is, the spatial acceleration of frame Fp can be computed as:
A_WFp = Jv_WFp(q)⋅v̇ + Ab_WFp(q, v)
where Ab_WFp(q, v) = J̇v_WFp(q, v)⋅v.
- See also
- CalcFrameGeometricJacobianExpressedInWorld() to compute the geometric Jacobian
Jv_WFp(q).
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q and generalized velocities v. [in] frame_F The position p_FPof frameFpis measured and expressed in this frame F.[in] p_FP The (fixed) position of the origin Pof frameFpas measured and expressed in frame F.
- Returns
- Ab_WFp The bias term, function of the generalized positions q and the generalized velocities v as stored in
context. The returned vector is of size 6, with the first three elements related to the bias in angular acceleration and the with the last three elements related to the bias in translational acceleration.
- Note
- SpatialAcceleration(Ab_WFp) defines a valid SpatialAcceleration. (Deprecated.)
- Deprecated:
- "Use CalcBiasForJacobianSpatialVelocity()."
This will be removed from Drake on or after "2019-09-01" .
◆ CalcBiasForJacobianSpatialVelocity()
| Vector6<T> CalcBiasForJacobianSpatialVelocity | ( | const systems::Context< T > & | context, |
| JacobianWrtVariable | with_respect_to, | ||
| const Frame< T > & | frame_F, | ||
| const Eigen::Ref< const Vector3< T >> & | p_FoFp_F, | ||
| const Frame< T > & | frame_A, | ||
| const Frame< T > & | frame_E | ||
| ) | const |
For a point Fp that is regarded as a point of (fixed/welded to) a frame F, computes the bias term Abias_AFp associated with A_AFp (Fp's spatial acceleration in a frame A) with respect to "speeds" 𝑠, where 𝑠 is either q̇ ≜ [q̇₁ ...
q̇ⱼ]ᵀ (time-derivatives of generalized positions) or v ≜ [v₁ ... vₖ]ᵀ (generalized velocities). That is, point Fp's spatial acceleration in frame A can be written
A_AFp = Js_V_AFp(q)⋅ṡ + Abias_AFp(q, v)
where Abias_AFp = J̇s_V_AFp(q, s)⋅s.
- See also
- CalcJacobianSpatialVelocity() to compute
Js_V_AFp, point Fp's spatial velocity Jacobian in frame A with respect to s.
- Parameters
-
[in] context The state of the multibody system, which includes the generalized positions q and generalized velocities v. [in] with_respect_to Enum equal to JacobianWrtVariable::kQDot or JacobianWrtVariable::kV, indicating whether the Jacobian Js_v_AFpis partial derivatives with respect to 𝑠 = q̇ (time-derivatives of generalized positions) or with respect to 𝑠 = v (generalized velocities).[in] frame_F The frame on which point Fp is fixed/welded. [in] p_FoFp_F position vector from Fo (frame F's origin) to point Fp, expressed in frame F. [in] frame_A The frame that measures Abias_AFp. Currently, an exception is thrown if frame_A is not the World frame.[in] frame_E The frame in which Abias_AFpis expressed on output.
- Returns
- Abias_AFp_E Fp's spatial acceleration bias in frame_A is returned in a
6 x 1matrix whose first three elements are frame_F's angular acceleration bias in frame_A (expressed in frame_E) and whose last three elements are point Fp's translational acceleration bias in frame_A (expressed in frame_E). These bias terms are functions of the generalized positions q and the generalized velocities v and depend on whetherwith_respect_tois kQDot or kV. Note: Although the return quantity is a Vector6, it is actually a SpatialAcceleration (having units of that type).
- Exceptions
-
std::exception if with_respect_tois not JacobianWrtVariable::kVstd::exception if frame_A is not the world frame.
◆ CalcBiasForJacobianTranslationalVelocity()
| VectorX<T> CalcBiasForJacobianTranslationalVelocity | ( | const systems::Context< T > & | context, |
| JacobianWrtVariable | with_respect_to, | ||
| const Frame< T > & | frame_F, | ||
| const Eigen::Ref< const MatrixX< T >> & | p_FP_list, | ||
| const Frame< T > & | frame_A, | ||
| const Frame< T > & | frame_E | ||
| ) | const |
For a point Fp that is regarded as a point of (fixed/welded to) a frame F, computes bias term abias_AFp associated with a_AFp (Fp's translational acceleration in a frame A) with respect to "speeds" 𝑠, where 𝑠 is either q̇ ≜ [q̇₁ ...
q̇ⱼ]ᵀ (time-derivatives of generalized positions) or v ≜ [v₁ ... vₖ]ᵀ (generalized velocities). That is, point Fp's translational acceleration in frame A can be written
a_AFp = Js_v_AFp(q)⋅ṡ + abias_AFp(q, v)
where abias_AFp = J̇s_v_AFp(q, s)⋅s.
This method computes abias_AFp for each point Fp in the p_FP_list. The p_FP_list is a list of position vectors from Fo (Frame F's origin) to each such point Fp, expressed in frame F.
- See also
- CalcJacobianTranslationalVelocity() to compute
Js_v_AFp, point Fp's translational velocity Jacobian in frame A with respect to s.
- Parameters
-
[in] context The state of the multibody system, which includes the generalized positions q and generalized velocities v. [in] with_respect_to Enum equal to JacobianWrtVariable::kQDot or JacobianWrtVariable::kV, indicating whether the Jacobian Js_v_AFpis partial derivatives with respect to 𝑠 = q̇ (time-derivatives of generalized positions) or with respect to 𝑠 = v (generalized velocities).[in] frame_F The frame on which point Fp is fixed/welded. [in] p_FP_list 3 x nmatrix of position vectorsp_FoFp_Ffrom Fo (frame F's origin) to each such point Fp, expressed in frame F.[in] frame_A The frame that measures abias_AFp. Currently, an exception is thrown if frame_A is not the World frame.[in] frame_E The frame in which abias_AFpis expressed on output.
- Returns
- abias_AFp_E matrix of translational acceleration bias terms in frame_A and expressed in frame_E for each of the
npoints associated with p_FP_list. These bias terms are functions of the generalized positions q and the generalized velocities v and depend on whetherwith_respect_tois kQDot or kV.
- Exceptions
-
std::exception if p_FP_listdoes not have 3 rows.std::exception if with_respect_tois not JacobianWrtVariable::kVstd::exception if frame_A is not the world frame.
◆ CalcBiasForPointsGeometricJacobianExpressedInWorld()
| VectorX<T> CalcBiasForPointsGeometricJacobianExpressedInWorld | ( | const systems::Context< T > & | context, |
| const Frame< T > & | frame_F, | ||
| const Eigen::Ref< const MatrixX< T >> & | p_FP_list | ||
| ) | const |
Computes the bias term b_WFp associated with the translational acceleration a_WFp of a point P instantaneously moving with a frame F.
That is, the translational acceleration of point P can be computed as:
a_WFp = Jv_WFp(q)⋅v̇ + b_WFp(q, v)
where b_WFp = J̇v_WFp(q, v)⋅v.
This method computes b_WFp for each point P in p_FP_list defined by its position p_FP in frame_F.
- See also
- CalcPointsGeometricJacobianExpressedInWorld() to compute the geometric Jacobian
Jv_WFp(q).
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q and generalized velocities v. [in] frame_F Points Pin the list instantaneously move with this frame.[in] p_FP_list A matrix with the fixed position of a list of points Pmeasured and expressed inframe_F. Each column of this matrix contains the position vectorp_FPfor a pointPmeasured and expressed in frame F. Therefore this input matrix lives in ℝ³ˣⁿᵖ withnpthe number of points in the list.
- Returns
- b_WFp The bias term, function of the generalized positions q and the generalized velocities v as stored in
context. The returned vector has size3⋅np, with np the number of points inp_FP_list, and concatenates the bias terms for each pointPin the list in the same order they are specified on input.
- Exceptions
-
std::exception if p_FP_listdoes not have 3 rows. (Deprecated.)
- Deprecated:
- "Use CalcBiasForJacobianTranslationalVelocity()."
This will be removed from Drake on or after "2019-09-01" .
◆ CalcBiasTerm()
| void CalcBiasTerm | ( | const systems::Context< T > & | context, |
| EigenPtr< VectorX< T >> | Cv | ||
| ) | const |
Computes the bias term C(q, v)v containing Coriolis and gyroscopic effects of the multibody equations of motion:
M(q)v̇ + C(q, v)v = tau_app + ∑ J_WBᵀ(q) Fapp_Bo_W
where M(q) is the multibody model's mass matrix and tau_app consists of a vector applied generalized forces. The last term is a summation over all bodies in the model where Fapp_Bo_W is an applied spatial force on body B at Bo which gets projected into the space of generalized forces with the geometric Jacobian J_WB(q) which maps generalized velocities into body B spatial velocity as V_WB = J_WB(q)v.
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q and the generalized velocities v. [out] Cv On output, Cvwill contain the productC(q, v)v. It must be a valid (non-null) pointer to a column vector inℛⁿwith n the number of generalized velocities (num_velocities()) of the model. This method aborts if Cv is nullptr or if it does not have the proper size.
◆ CalcCenterOfMassPosition() [1/2]
| Vector3<T> CalcCenterOfMassPosition | ( | const systems::Context< T > & | context | ) | const |
This method computes the center of mass position p_WCcm of all bodies in MultibodyPlant measured and expressed in world frame W.
The bodies are considered as a single composite body C, whose center of mass composite_mass is located at Ccm. The world_body() is ignored.
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q of the model.
- Return values
-
p_WCcm The output position of center of mass in the world frame W.
- Exceptions
-
std::runtime_error if MultibodyPlanthas no body exceptworld_body().std::runtime_error unless composite_mass > 0.
◆ CalcCenterOfMassPosition() [2/2]
| Vector3<T> CalcCenterOfMassPosition | ( | const systems::Context< T > & | context, |
| const std::vector< ModelInstanceIndex > & | model_instances | ||
| ) | const |
This method computes the center of mass position p_WCcm of specified model instances measured and expressed in world frame W.
The specified model instances are considered as a single composite body C, whose center of mass composite_mass is located at Ccm. The models are selected by a vector of model instances model_instances. This function does not distinguish between welded bodies, joint connected bodies and floating bodies in the model_instances. The world_body() is ignored.
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q of the model. [in] model_instances The vector of selected model instances.
- Return values
-
p_WCcm The output position of center of mass in the world frame W.
- Exceptions
-
std::runtime_error if MultibodyPlanthas no model_instance exceptworld_model_instance().std::runtime_error unless composite_mass > 0.
◆ CalcConservativePower()
| T CalcConservativePower | ( | const systems::Context< T > & | context | ) | const |
Computes and returns the power generated by conservative forces in the multibody model.
This quantity is defined to be positive when the potential energy is decreasing. In other words, if U(q) is the potential energy as defined by CalcPotentialEnergy(), then the conservative power, Pc, is Pc = -U̇(q).
- See also
- CalcPotentialEnergy()
◆ CalcForceElementsContribution()
| void CalcForceElementsContribution | ( | const systems::Context< T > & | context, |
| MultibodyForces< T > * | forces | ||
| ) | const |
Computes the combined force contribution of ForceElement objects in the model.
A ForceElement can apply forces as a spatial force per body or as generalized forces, depending on the ForceElement model. ForceElement contributions are a function of the state and time only. The output from this method can immediately be used as input to CalcInverseDynamics() to include the effect of applied forces by force elements.
- Parameters
-
[in] context The context containing the state of this model. [out] forces A pointer to a valid, non nullptr, multibody forces object. On output forceswill store the forces exerted by all the ForceElement objects in the model.
- Exceptions
-
std::exception if forcesis null or not compatible with this model, per MultibodyForces::CheckInvariants().
◆ CalcFrameGeometricJacobianExpressedInWorld()
| void CalcFrameGeometricJacobianExpressedInWorld | ( | const systems::Context< T > & | context, |
| const Frame< T > & | frame_F, | ||
| const Eigen::Ref< const Vector3< T >> & | p_FP, | ||
| EigenPtr< MatrixX< T >> | J_WFp | ||
| ) | const |
Given a frame Fp defined by shifting a frame F from its origin Fo to a new origin P, this method computes the geometric Jacobian Jv_WFp for frame Fp.
The new origin P is specified by the position vector p_FP in frame F. The frame geometric Jacobian Jv_WFp is defined by:
V_WFp(q, v) = Jv_WFp(q)⋅v
where V_WFp(q, v) is the spatial velocity of frame Fp measured and expressed in the world frame W and q and v are the vectors of generalized position and velocity, respectively. The geometric Jacobian Jv_WFp(q) is a function of the generalized coordinates q only.
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q. [in] frame_F The position p_FPof frameFpis measured and expressed in this frame F.[in] p_FP The (fixed) position of the origin Pof frameFpas measured and expressed in frame F.[out] Jv_WFp The geometric Jacobian Jv_WFp(q), function of the generalized positions q only. This Jacobian relates to the spatial velocityV_WFpof frameFpby:V_WFp(q, v) = Jv_WFp(q)⋅vThereforeJv_WFpis a matrix of size6 x nv, withnvthe number of generalized velocities. On input, matrixJv_WFpmust have size6 x nvor this method throws an exception. The top rows of this matrix (which can be accessed with Jv_WFp.topRows<3>()) is the JacobianHw_WFprelated to the angular velocity ofFpin W byw_WFp = Hw_WFp⋅v. The bottom rows of this matrix (which can be accessed with Jv_WFp.bottomRows<3>()) is the JacobianHv_WFprelated to the translational velocity of the originPof frameFpin W byv_WFpo = Hv_WFp⋅v. This ordering is consistent with the internal storage of the SpatialVelocity class. Therefore the following operations results in a valid spatial velocity:SpatialVelocity<double> Jv_WFp_times_v(Jv_WFp * v);
- Exceptions
-
std::exception if J_WFpis nullptr or if it is not of size6 x nv.
◆ CalcGravityGeneralizedForces()
| VectorX<T> CalcGravityGeneralizedForces | ( | const systems::Context< T > & | context | ) | const |
Computes the generalized forces tau_g(q) due to gravity as a function of the generalized positions q stored in the input context.
The vector of generalized forces due to gravity tau_g(q) is defined such that it appears on the right hand side of the equations of motion together with any other generalized forces, like so:
Mv̇ + C(q, v)v = tau_g(q) + tau_app
where tau_app includes any other generalized forces applied on the system.
- Parameters
-
[in] context The context storing the state of the model.
- Returns
- tau_g A vector containing the generalized forces due to gravity. The generalized forces are consistent with the vector of generalized velocities
vforthisso that the inner productv⋅tau_gcorresponds to the power applied by the gravity forces on the mechanical system. That is,v⋅tau_g > 0corresponds to potential energy going into the system, as either mechanical kinetic energy, some other potential energy, or heat, and therefore to a decrease of the gravitational potential energy.
◆ CalcInverseDynamics()
| VectorX<T> CalcInverseDynamics | ( | const systems::Context< T > & | context, |
| const VectorX< T > & | known_vdot, | ||
| const MultibodyForces< T > & | external_forces | ||
| ) | const |
Given the state of this model in context and a known vector of generalized accelerations vdot, this method computes the set of generalized forces tau that would need to be applied in order to attain the specified generalized accelerations.
Mathematically, this method computes:
tau = M(q)v̇ + C(q, v)v - tau_app - ∑ J_WBᵀ(q) Fapp_Bo_W
where M(q) is the model's mass matrix, C(q, v)v is the bias term containing Coriolis and gyroscopic effects and tau_app consists of a vector applied generalized forces. The last term is a summation over all bodies in the model where Fapp_Bo_W is an applied spatial force on body B at Bo which gets projected into the space of generalized forces with the geometric Jacobian J_WB(q) which maps generalized velocities into body B spatial velocity as V_WB = J_WB(q)v. This method does not compute explicit expressions for the mass matrix nor for the bias term, which would be of at least O(n²) complexity, but it implements an O(n) Newton-Euler recursive algorithm, where n is the number of bodies in the model. The explicit formation of the mass matrix M(q) would require the calculation of O(n²) entries while explicitly forming the product C(q, v) * v could require up to O(n³) operations (see [Featherstone 1987, §4]), depending on the implementation. The recursive Newton-Euler algorithm is the most efficient currently known general method for solving inverse dynamics [Featherstone 2008].
- Parameters
-
[in] context The context containing the state of the model. [in] known_vdot A vector with the known generalized accelerations vdotfor the full model. Use the provided Joint APIs in order to access entries into this array.[in] external_forces A set of forces to be applied to the system either as body spatial forces Fapp_Bo_Wor generalized forcestau_app, see MultibodyForces for details.
- Returns
- the vector of generalized forces that would need to be applied to the mechanical system in order to achieve the desired acceleration given by
known_vdot.
◆ CalcJacobianAngularVelocity()
| void CalcJacobianAngularVelocity | ( | const systems::Context< T > & | context, |
| const JacobianWrtVariable | with_respect_to, | ||
| const Frame< T > & | frame_B, | ||
| const Frame< T > & | frame_A, | ||
| const Frame< T > & | frame_E, | ||
| EigenPtr< Matrix3X< T >> | Js_w_AB_E | ||
| ) | const |
Returns a frame B's angular velocity Jacobian in a frame A with respect to "speeds" 𝑠, where 𝑠 is either q̇ ≜ [q̇₁ ...
q̇ⱼ]ᵀ (time-derivatives of generalized positions) or v ≜ [v₁ ... vₖ]ᵀ (generalized velocities). When a frame B's angular velocity w_AB in a frame A is characterized by speeds 𝑠, B's angular velocity Jacobian in A with respect to 𝑠 is
Js_w_AB = [ ∂(w_AB)/∂𝑠₁, ... ∂(w_AB)/∂𝑠ₙ ] (n is j or k)
B's angular velocity in A is linear in 𝑠₁, ... 𝑠ₙ and can be written w_AB = Js_w_AB ⋅ 𝑠 where 𝑠 is [𝑠₁ ... 𝑠ₙ]ᵀ.
- Parameters
-
[in] context The state of the multibody system. [in] with_respect_to Enum equal to JacobianWrtVariable::kQDot or JacobianWrtVariable::kV, indicating whether the Jacobian Js_w_ABis partial derivatives with respect to 𝑠 = q̇ (time-derivatives of generalized positions) or with respect to 𝑠 = v (generalized velocities).[in] frame_B The frame B in w_AB(B's angular velocity in A).[in] frame_A The frame A in w_AB(B's angular velocity in A).[in] frame_E The frame in which w_ABis expressed on input and the frame in which the JacobianJs_w_ABis expressed on output.[out] Js_w_AB_E Frame B's angular velocity Jacobian in frame A with respect to speeds 𝑠 (which is either q̇ or v), expressed in frame E. The Jacobian is a function of only generalized positions q (which are pulled from the context). The previous definition shows Js_w_AB_Eis a matrix of size3 x n, where n is the number of elements in 𝑠.
- Exceptions
-
std::exception if Js_w_AB_Eis nullptr or not of size3 x n.
◆ CalcJacobianSpatialVelocity()
| void CalcJacobianSpatialVelocity | ( | const systems::Context< T > & | context, |
| JacobianWrtVariable | with_respect_to, | ||
| const Frame< T > & | frame_B, | ||
| const Eigen::Ref< const Vector3< T >> & | p_BoBi_B, | ||
| const Frame< T > & | frame_A, | ||
| const Frame< T > & | frame_E, | ||
| EigenPtr< MatrixX< T >> | Jw_ABp_E | ||
| ) | const |
For each point Bi of (fixed to) a frame B with spatial velocity v_ABi in a frame A, calculates Bi's spatial velocity Jacobian in A with respect to 𝑠, which is defined as.
Js_V_ABi = [ ∂(V_ABi)/∂𝑠₁, ... ∂(V_ABi)/∂𝑠ₙ ] (n is j or k)
where "speeds" 𝑠 is either q̇ ≜ [q̇₁ ... q̇ⱼ]ᵀ (time-derivatives of j generalized positions) or v ≜ [v₁ ... vₖ]ᵀ (k generalized velocities). Note: Spatial velocity V_ABi is linear in 𝑠₁, ... 𝑠ₙ and can be written V_ABi = Js_V_ABi ⋅ 𝑠 where 𝑠 is [𝑠₁ ... 𝑠ₙ]ᵀ.
- Parameters
-
[in] context The state of the multibody system. [in] with_respect_to Enum equal to JacobianWrtVariable::kQDot or JacobianWrtVariable::kV, indicating whether the Jacobian Js_V_ABiis partial derivatives with respect to 𝑠 = q̇ (time-derivatives of generalized positions) or with respect to 𝑠 = v (generalized velocities).[in] frame_B The frame on which point Bi is fixed (e.g., welded). [in] p_BoBi_B A position vector or list of p position vectors from Bo (frame_B's origin) to points Bi (regarded as fixed to B), where each position vector is expressed in frame_B. [in] frame_A The frame that measures v_ABi(Bi's velocity in A).[in] frame_E The frame in which v_ABiis expressed on input and the frame in which the JacobianJs_V_ABiis expressed on output.[out] Js_V_ABi_E Point Bi's spatial velocity Jacobian in frame A with respect to speeds 𝑠 (which is either q̇ or v), expressed in frame E. Js_V_ABi_Eis a3*p x nmatrix, where p is the number of points Bi and n is the number of elements in 𝑠. The Jacobian is a function of only generalized positions q (which are pulled from the context). Note: If p = 1 (one point), a6 x nmatrix is returned with the first three rows storing frame B's angular velocity Jacobian in A and rows 4-6 storing point Bi's translational velocity Jacobian in A, i.e.,If p = 2 (two points), aJs_wAB_E = Js_V_ABi_E.topRows<3>();Js_vAB1_E = Js_V_ABi_E.bottomRows<3>();12 x nmatrix is returned. Rows 1-3 and 7-9 store exactly identical information (B's angular velocity Jacobian in A). Rows 4-6 store point B1's translational velocity Jacobian which differs from rows 10-12 which store point B2's translational velocity Jacobian. If p is large and storage efficiency is a concern, calculate frame B's angular velocity Jacobian using CalcJacobianAngularVelocity() and then use CalcJacobianTranslationalVelocity().
- Exceptions
-
std::exception if Js_V_ABi_Eis nullptr or not sized3*p x n.
◆ CalcJacobianTranslationalVelocity()
| void CalcJacobianTranslationalVelocity | ( | const systems::Context< T > & | context, |
| JacobianWrtVariable | with_respect_to, | ||
| const Frame< T > & | frame_B, | ||
| const Eigen::Ref< const Matrix3X< T >> & | p_BoBi_B, | ||
| const Frame< T > & | frame_A, | ||
| const Frame< T > & | frame_E, | ||
| EigenPtr< MatrixX< T >> | Js_v_ABi_E | ||
| ) | const |
For each point Bi of (fixed to) a frame B with translational velocity v_ABi in a frame A, calculates Bi's translational velocity Jacobian in A with respect to 𝑠, which is defined as.
Js_v_ABi = [ ∂(v_ABi)/∂𝑠₁, ... ∂(v_ABi)/∂𝑠ₙ ] (n is j or k)
where "speeds" 𝑠 is either q̇ ≜ [q̇₁ ... q̇ⱼ]ᵀ (time-derivatives of j generalized positions) or v ≜ [v₁ ... vₖ]ᵀ (k generalized velocities). Note: Point Bi's velocity in A is linear in 𝑠₁, ... 𝑠ₙ and can be written v_ABi = Js_v_ABi ⋅ 𝑠 where 𝑠 is [𝑠₁ ... 𝑠ₙ]ᵀ.
- Parameters
-
[in] context The state of the multibody system. [in] with_respect_to Enum equal to JacobianWrtVariable::kQDot or JacobianWrtVariable::kV, indicating whether the Jacobian Js_v_ABiis partial derivatives with respect to 𝑠 = q̇ (time-derivatives of generalized positions) or with respect to 𝑠 = v (generalized velocities).[in] frame_B The frame on which point Bi is fixed (e.g., welded). [in] p_BoBi_B A position vector or list of p position vectors from Bo (frame_B's origin) to points Bi (regarded as fixed to B), where each position vector is expressed in frame_B. [in] frame_A The frame that measures v_ABi(Bi's velocity in A).[in] frame_E The frame in which v_ABiis expressed on input and the frame in which the JacobianJs_v_ABiis expressed on output.[out] Js_v_ABi_E Point Bi's velocity Jacobian in frame A with respect to speeds 𝑠 (which is either q̇ or v), expressed in frame E. Js_v_ABi_Eis a3*p x nmatrix, where p is the number of points Bi and n is the number of elements in 𝑠. The Jacobian is a function of only generalized positions q (which are pulled from the context).
- Exceptions
-
std::exception if Js_v_ABi_Eis nullptr or not sized3*p x n.
◆ CalcMassMatrixViaInverseDynamics()
| void CalcMassMatrixViaInverseDynamics | ( | const systems::Context< T > & | context, |
| EigenPtr< MatrixX< T >> | H | ||
| ) | const |
Performs the computation of the mass matrix M(q) of the model using inverse dynamics, where the generalized positions q are stored in context.
- Parameters
-
[in] context The context containing the state of the model. [out] H A valid (non-null) pointer to a squared matrix in ℛⁿˣⁿwith n the number of generalized velocities (num_velocities()) of the model. This method aborts if H is nullptr or if it does not have the proper size.
The algorithm used to build M(q) consists in computing one column of M(q) at a time using inverse dynamics. The result from inverse dynamics, with no applied forces, is the vector of generalized forces:
tau = M(q)v̇ + C(q, v)v
where q and v are the generalized positions and velocities, respectively. When v = 0 the Coriolis and gyroscopic forces term C(q, v)v is zero. Therefore the i-th column of M(q) can be obtained performing inverse dynamics with an acceleration vector v̇ = eᵢ, with eᵢ the standard (or natural) basis of ℛⁿ with n the number of generalized velocities. We write this as:
H.ᵢ(q) = M(q) * e_i
where H.ᵢ(q) (notice the dot for the rows index) denotes the i-th column in M(q).
- Warning
- This is an O(n²) algorithm. Avoid the explicit computation of the mass matrix whenever possible.
◆ CalcPointsAnalyticalJacobianExpressedInWorld()
| void CalcPointsAnalyticalJacobianExpressedInWorld | ( | const systems::Context< T > & | context, |
| const Frame< T > & | frame_F, | ||
| const Eigen::Ref< const MatrixX< T >> & | p_FP_list, | ||
| EigenPtr< MatrixX< T >> | p_WP_list, | ||
| EigenPtr< MatrixX< T >> | Jq_WFp | ||
| ) | const |
Given a list of points with fixed position vectors p_FP in a frame F, (that is, their time derivative DtF(p_FP) in frame F is zero), this method computes the analytical Jacobian Jq_WFp(q).
The analytical Jacobian Jq_WFp(q) is defined by:
Jq_WFp(q) = d(p_WFp(q))/dq
where p_WFp(q) is the position of point P, which moves with frame F, in the world frame W.
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q. [in] frame_F The positions p_FPof each point in the input set are measured and expressed in this frame F and are constant (fixed) in this frame.[in] p_FP_list A matrix with the fixed position of a set of points Pmeasured and expressed inframe_F. Each column of this matrix contains the position vectorp_FPfor a pointPmeasured and expressed in frame F. Therefore this input matrix lives in ℝ³ˣⁿᵖ withnpthe number of points in the set.[out] p_WP_list The output positions of each point Pnow measured and expressed in computing the geometric JacobianJ_WPand therefore external storage must be provided. The outputp_WP_listmust have the same size as the input setp_FP_listor otherwise this method throws a std::runtime_error exception. That isp_WP_listmust be inℝ³ˣⁿᵖ.[out] Jq_WFp The analytical Jacobian Jq_WFp(q), function of the generalized positions q only. We stack the positions of each point P in the world frame W into a column vector p_WFp = [p_WFp1; p_WFp2; ...] of size 3⋅np, with np the number of points in p_FP_list. Then the analytical Jacobian is defined as:Jq_WFp(q) = ∇(p_WFp(q))with∇(⋅)the gradient operator with respect to the generalized positions q. ThereforeJq_WFpis a matrix of size3⋅np x nq, withnqthe number of generalized positions. On input, matrixJq_WFpmust have size3⋅np x nqor this method throws a std::runtime_error exception.
- Exceptions
-
std::exception if the output p_WP_listis nullptr or does not have the same size as the input arrayp_FP_list.std::exception if Jq_WFpis nullptr or if it does not have the appropriate size, see documentation forJq_WFpfor details. (Deprecated.)
- Deprecated:
- "Use CalcJacobianTranslationalVelocity()."
This will be removed from Drake on or after "2019-10-01" .
◆ CalcPointsGeometricJacobianExpressedInWorld() [1/2]
| void CalcPointsGeometricJacobianExpressedInWorld | ( | const systems::Context< T > & | context, |
| const Frame< T > & | frame_F, | ||
| const Eigen::Ref< const MatrixX< T >> & | p_FP_list, | ||
| EigenPtr< MatrixX< T >> | p_WP_list, | ||
| EigenPtr< MatrixX< T >> | Jv_WFp | ||
| ) | const |
Given a list of points with fixed position vectors p_FP in a frame F, (that is, their time derivative DtF(p_FP) in frame F is zero), this method computes the geometric Jacobian Jv_WFp defined by:
v_WP(q, v) = Jv_WFp(q)⋅v
where v_WP(q, v) is the translational velocity of point P in the world frame W and q and v are the vectors of generalized position and velocity, respectively.
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q. [in] frame_F The positions p_FPof each point in the input set are measured and expressed in this frame F and are constant (fixed) in this frame.[in] p_FP_list A matrix with the fixed position of a set of points Pmeasured and expressed inframe_F. Each column of this matrix contains the position vectorp_FPfor a pointPmeasured and expressed in frame F. Therefore this input matrix lives in ℝ³ˣⁿᵖ withnpthe number of points in the set.[out] p_WP_list The output positions of each point Pnow measured and expressed in computing the geometric JacobianJ_WPand therefore external storage must be provided. The outputp_WP_listmust have the same size as the input setp_FP_listor otherwise this method throws a std::runtime_error exception. That isp_WP_listmust be inℝ³ˣⁿᵖ.[out] Jv_WFp The geometric Jacobian Jv_WFp(q), function of the generalized positions q only. This Jacobian relates the translational velocityv_WPof each pointPin the input set by:v_WP(q, v) = Jv_WFp(q)⋅vso thatv_WPis a column vector of size3⋅npconcatenating the velocity of all pointsPin the same order they were given in the input set. ThereforeJ_WFpis a matrix of size3⋅np x nv, withnvthe number of generalized velocities. On input, matrixJ_WFpmust have size3⋅np x nvor this method throws a std::runtime_error exception.
- Exceptions
-
std::exception if the output p_WP_listis nullptr or does not have the same size as the input arrayp_FP_list.std::exception if Jv_WFpis nullptr or if it does not have the appropriate size, see documentation forJv_WFpfor details. (Deprecated.)
- Deprecated:
- "Use CalcJacobianTranslationalVelocity()."
This will be removed from Drake on or after "2019-10-01" .
◆ CalcPointsGeometricJacobianExpressedInWorld() [2/2]
| void CalcPointsGeometricJacobianExpressedInWorld | ( | const systems::Context< T > & | context, |
| const Frame< T > & | frame_F, | ||
| const Eigen::Ref< const MatrixX< T >> & | p_WP_list, | ||
| EigenPtr< MatrixX< T >> | Jv_WFp | ||
| ) | const |
This is a variant to compute the geometric Jacobian Jv_WFp for a list of points P moving with frame_F, given that we know the position p_WP of each point in the list measured and expressed in the world frame W.
The geometric Jacobian Jv_WFp is defined such that:
v_WP(q, v) = Jv_WFp(q)⋅v
where v_WP(q, v) is the translational velocity of point P in the world frame W and q and v are the vectors of generalized position and velocity, respectively. Since the spatial velocity of each point P is linear in the generalized velocities, the geometric Jacobian Jv_WFp is a function of the generalized coordinates q only.
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q. [in] frame_F Points Pin the list instantaneously move with this frame.[in] p_WP_list A matrix with the fixed position of a list of points Pmeasured and expressed in the world frame W. Each column of this matrix contains the position vectorp_WPfor a pointPmeasured and expressed in the world frame W. Therefore this input matrix lives in ℝ³ˣⁿᵖ withnpthe number of points in the list.[out] Jv_WFp The geometric Jacobian Jv_WFp(q), function of the generalized positions q only. This Jacobian relates the translational velocityv_WPof each pointPin the input list by:`v_WP(q, v) = Jv_WFp(q)⋅v`so thatv_WPis a column vector of size3⋅npconcatenating the velocity of all pointsPin the same order they were given in the input list. ThereforeJ_WPis a matrix of size3⋅np x nv, withnvthe number of generalized velocities. On input, matrixJ_WPmust have size3⋅np x nvor this method throws a std::runtime_error exception.
- Exceptions
-
std::exception if Jv_WFpis nullptr or if it does not have the appropriate size, see documentation forJv_WFpfor details. (Deprecated.)
- Deprecated:
- "Use CalcJacobianTranslationalVelocity()."
This will be removed from Drake on or after "2019-10-01" .
◆ CalcPointsPositions()
| void CalcPointsPositions | ( | const systems::Context< T > & | context, |
| const Frame< T > & | frame_B, | ||
| const Eigen::Ref< const MatrixX< T >> & | p_BQi, | ||
| const Frame< T > & | frame_A, | ||
| EigenPtr< MatrixX< T >> | p_AQi | ||
| ) | const |
Given the positions p_BQi for a set of points Qi measured and expressed in a frame B, this method computes the positions p_AQi(q) of each point Qi in the set as measured and expressed in another frame A, as a function of the generalized positions q of the model.
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q of the model. [in] frame_B The frame B in which the positions p_BQiof a set of pointsQiare given.[in] p_BQi The input positions of each point Qiin frame B.p_BQi ∈ ℝ³ˣⁿᵖwithnpthe number of points in the set. Each column ofp_BQicorresponds to a vector in ℝ³ holding the position of one of the points in the set as measured and expressed in frame B.[in] frame_A The frame A in which it is desired to compute the positions p_AQiof each pointQiin the set.[out] p_AQi The output positions of each point Qinow computed as measured and expressed in frame A. The outputp_AQimust have the same size as the inputp_BQior otherwise this method aborts. That isp_AQimust be inℝ³ˣⁿᵖ.
- Note
- Both
p_BQiandp_AQimust have three rows. Otherwise this method will throw a std::runtime_error exception. This method also throws a std::runtime_error exception ifp_BQiandp_AQidiffer in the number of columns.
◆ CalcPotentialEnergy()
| T CalcPotentialEnergy | ( | const systems::Context< T > & | context | ) | const |
Computes and returns the total potential energy stored in this multibody model for the configuration given by context.
- Parameters
-
[in] context The context containing the state of the model.
- Returns
- The total potential energy stored in
thismultibody model.
◆ CalcRelativeFrameGeometricJacobian()
| void CalcRelativeFrameGeometricJacobian | ( | const systems::Context< T > & | context, |
| const Frame< T > & | frame_B, | ||
| const Eigen::Ref< const Vector3< T >> & | p_BP, | ||
| const Frame< T > & | frame_A, | ||
| const Frame< T > & | frame_E, | ||
| EigenPtr< MatrixX< T >> | Jv_ABp_E | ||
| ) | const |
Computes the geometric Jacobian for a point moving with a given frame.
Consider a point P instantaneously moving with a frame B with position p_BP in that frame. Frame Bp is the frame defined by shifting frame B with origin at Bo to a new origin at point P. The spatial velocity V_ABp_E of frame Bp measured in a frame A and expressed in a frame E relates to the generalized velocities of the system by the geometric Jacobian Jv_ABp_E(q) by:
V_ABp_E(q, v) = Jv_ABp_E(q)⋅v
This method computes the geometric Jacobian Jv_ABp_E(q).
- Parameters
-
[in] context The context containing the state of the model. It stores the generalized positions q. [in] frame_B The position p_BPof point P is measured and expressed in this frame.[in] p_BP The (fixed) position of the origin Pof frameBpas measured and expressed in frame B.[in] frame_A The second frame in which the spatial velocity V_ABpis measured and expressed.[in] frame_E Frame in which the velocity V_ABp_E is expressed. [out] Jv_ABp_E The geometric Jacobian Jv_ABp_E(q), function of the generalized positions q only. This Jacobian relates to the spatial velocityV_ABp_Eof frameBpin A and expressed in E by:V_ABp_E(q, v) = Jv_ABp_E(q)⋅vThereforeJv_ABp_Eis a matrix of size6 x nv, withnvthe number of generalized velocities. On input, matrixJv_ABp_Emust have size6 x nvor this method throws an exception. Given a6 x nvspatial Jacobian Jv, let Jvr be the3 x nvrotational part (top 3 rows) and Jvt be the translational part (bottom 3 rows). These can be obtained as follows:Jvr_ABp = Jv_ABp.topRows<3>(); Jvt_ABp = Jv_ABp.bottomRows<3>();This ordering is consistent with the internal storage of the SpatialVelocity class. Therefore the following operations results in a valid spatial velocity:SpatialVelocity<double> V_ABp(Jv_ABp * v);
- Exceptions
-
std::exception if J_ABpis nullptr or if it is not of size6 x nv. (Deprecated.)
- Deprecated:
- "Use CalcJacobianSpatialVelocity()."
This will be removed from Drake on or after "2019-09-01" .
◆ CalcRelativeRotationMatrix()
| math::RotationMatrix<T> CalcRelativeRotationMatrix | ( | const systems::Context< T > & | context, |
| const Frame< T > & | frame_F, | ||
| const Frame< T > & | frame_G | ||
| ) | const |
Calculates the rotation matrix R_FG relating frame F and frame G.
- Parameters
-
[in] context The state of the multibody system, which includes the system's generalized positions q. Note: R_FGis a function of q.[in] frame_F The frame F designated in the rigid transform R_FG.[in] frame_G The frame G designated in the rigid transform R_FG.
- Return values
-
R_FG The RigidTransform relating frame F and frame G.
◆ CalcRelativeTransform()
| math::RigidTransform<T> CalcRelativeTransform | ( | const systems::Context< T > & | context, |
| const Frame< T > & | frame_F, | ||
| const Frame< T > & | frame_G | ||
| ) | const |
Calculates the rigid transform (pose) X_FG relating frame F and frame G.
- Parameters
-
[in] context The state of the multibody system, which includes the system's generalized positions q. Note: X_FGis a function of q.[in] frame_F The frame F designated in the rigid transform X_FG.[in] frame_G The frame G designated in the rigid transform X_FG.
- Return values
-
X_FG The RigidTransform relating frame F and frame G.
◆ CalcSpatialAccelerationsFromVdot()
| void CalcSpatialAccelerationsFromVdot | ( | const systems::Context< T > & | context, |
| const VectorX< T > & | known_vdot, | ||
| std::vector< SpatialAcceleration< T >> * | A_WB_array | ||
| ) | const |
Given the state of this model in context and a known vector of generalized accelerations known_vdot, this method computes the spatial acceleration A_WB for each body as measured and expressed in the world frame W.
- Parameters
-
[in] context The context containing the state of this model. [in] known_vdot A vector with the generalized accelerations for the full model. [out] A_WB_array A pointer to a valid, non nullptr, vector of spatial accelerations containing the spatial acceleration A_WBfor each body. It must be of size equal to the number of bodies in the model. On output, entries will be ordered by BodyIndex.
- Exceptions
-
std::exception if A_WB_array is not of size num_bodies().
◆ CollectRegisteredGeometries()
| geometry::GeometrySet CollectRegisteredGeometries | ( | const std::vector< const Body< T > * > & | bodies | ) | const |
For each of the provided bodies, collects up all geometries that have been registered to that body.
Intended to be used in conjunction with SceneGraph::ExcludeCollisionsWithin() and SceneGraph::ExcludeCollisionsBetween() to filter collisions between the geometries registered to the bodies.
For example:
- Note
- There is a very specific order of operations:
- Bodies and geometries must be added to the MultibodyPlant.
- The MultibodyPlant must be finalized (via Finalize()).
- Create GeometrySet instances from bodies (via this method).
- Invoke SceneGraph::ExcludeCollisions*() to filter collisions.
- Allocate context.
Changing the order will cause exceptions to be thrown.
- Exceptions
-
std::exception if called pre-finalize.
◆ default_coulomb_friction()
| const CoulombFriction<double>& default_coulomb_friction | ( | geometry::GeometryId | id | ) | const |
Returns the friction coefficients provided during geometry registration for the given geometry id.
We call these the "default" coefficients but note that we mean user-supplied per-geometry default, not something more global.
- Exceptions
-
std::exception if iddoes not correspond to a geometry inthismodel registered for contact modeling.
- See also
- RegisterCollisionGeometry() for details on geometry registration.
◆ EvalBodyPoseInWorld()
| const math::RigidTransform<T>& EvalBodyPoseInWorld | ( | const systems::Context< T > & | context, |
| const Body< T > & | body_B | ||
| ) | const |
Evaluate the pose X_WB of a body B in the world frame W.
- Parameters
-
[in] context The context storing the state of the model. [in] body_B The body B for which the pose is requested.
- Return values
-
X_WB The pose of body frame B in the world frame W.
- Exceptions
-
std::exception if Finalize() was not called on thismodel or ifbody_Bdoes not belong to this model.
◆ EvalBodySpatialVelocityInWorld()
| const SpatialVelocity<T>& EvalBodySpatialVelocityInWorld | ( | const systems::Context< T > & | context, |
| const Body< T > & | body_B | ||
| ) | const |
Evaluate the spatial velocity V_WB of a body B in the world frame W.
- Parameters
-
[in] context The context storing the state of the model. [in] body_B The body B for which the spatial velocity is requested.
- Returns
- V_WB The spatial velocity of body frame B in the world frame W.
- Exceptions
-
std::exception if Finalize() was not called on thismodel or ifbody_Bdoes not belong to this model.
◆ EvalPointPairPenetrations()
| const std::vector<geometry::PenetrationAsPointPair<T> >& EvalPointPairPenetrations | ( | const systems::Context< T > & | context | ) | const |
Evaluates all point pairs of contact for a given state of the model stored in context.
Each entry in the returned vector corresponds to a single point pair corresponding to two interpenetrating bodies A and B. The size of the returned vector corresponds to the total number of contact penetration pairs. If no geometry was registered, the output vector is empty.
- See also
- PenetrationAsPointPair for further details on the returned data.
- Exceptions
-
std::exception if called pre-finalize. See Finalize().
◆ Finalize() [1/2]
| void Finalize | ( | ) |
This method must be called after all elements in the model (joints, bodies, force elements, constraints, etc.) are added and before any computations are performed.
It essentially compiles all the necessary "topological information", i.e. how bodies, joints and, any other elements connect with each other, and performs all the required pre-processing to enable computations at a later stage.
If the finalize stage is successful, the topology of this MultibodyPlant is valid, meaning that the topology is up-to-date after this call. No more multibody elements can be added after a call to Finalize().
At Finalize(), state and input/output ports for this plant are declared. If this plant registered geometry with a SceneGraph, input and output ports to enable communication with that SceneGraph are declared as well.
If geometry has been registered on a SceneGraph instance, that instance must be provided to the Finalize() method so that any geometric implications of the finalization process can be appropriately handled.
- See also
- is_finalized().
- Exceptions
-
std::logic_error if the MultibodyPlant has already been finalized.
◆ Finalize() [2/2]
| void Finalize | ( | geometry::SceneGraph< T > * | scene_graph | ) |
(Do not use.) This is a deprecated overload that takes a scene_graph argument.
- Exceptions
-
std::logic_error if a different scene_graph instance is provided than the one for which this plant is a geometry source. (Deprecated.)
- Deprecated:
- "Remove the scene_graph argument at the call site; instead of passing a " "scene_graph pointer, call RegisterAsSourceForSceneGraph first, instead."
This will be removed from Drake on or after "2019-10-01" .
◆ geometry_source_is_registered()
| bool geometry_source_is_registered | ( | ) | const |
Returns true if this MultibodyPlant was registered with a SceneGraph.
This method can be called at any time during the lifetime of this plant to query if this plant has been registered with a SceneGraph, either pre- or post-finalize, see Finalize().
◆ get_actuation_input_port() [1/2]
| const systems::InputPort< T > & get_actuation_input_port | ( | ) | const |
Returns a constant reference to the input port for external actuation for the case where only one model instance has actuated dofs.
This input port is a vector valued port, which can be set with JointActuator::set_actuation_vector().
- Precondition
- Finalize() was already called on
thisplant.
- Exceptions
-
std::exception if called before Finalize(), if the model does not contain any actuators, or if multiple model instances have actuated dofs.
◆ get_actuation_input_port() [2/2]
| const systems::InputPort< T > & get_actuation_input_port | ( | ModelInstanceIndex | model_instance | ) | const |
Returns a constant reference to the input port for external actuation for a specific model instance.
This input port is a vector valued port, which can be set with JointActuator::set_actuation_vector().
- Precondition
- Finalize() was already called on
thisplant.
- Exceptions
-
std::exception if called before Finalize(). std::exception if the model instance does not exist.
◆ get_applied_generalized_force_input_port()
| const systems::InputPort< T > & get_applied_generalized_force_input_port | ( | ) | const |
Returns a constant reference to the vector-valued input port for applied generalized forces, and the vector will be added directly into tau (see System dynamics).
This vector is ordered using the same convention as the plant velocities: you can set the generalized forces that will be applied to model instance i using, e.g., SetVelocitiesInArray(i, model_forces, &force_array).
- Exceptions
-
std::exception if called before Finalize().
◆ get_applied_spatial_force_input_port()
| const systems::InputPort< T > & get_applied_spatial_force_input_port | ( | ) | const |
Returns a constant reference to the input port for applying spatial forces to bodies in the plant.
The data type for the port is an std::vector of ExternallyAppliedSpatialForce; any number of spatial forces can be applied to any number of bodies in the plant.
◆ get_body()
Returns a constant reference to the body with unique index body_index.
- Exceptions
-
std::exception if body_indexdoes not correspond to a body in this model.
◆ get_contact_penalty_method_time_scale()
| double get_contact_penalty_method_time_scale | ( | ) | const |
Returns a time-scale estimate tc based on the requested penetration allowance δ set with set_penetration_allowance().
For the penalty method in use to enforce non-penetration, this time scale relates to the time it takes the relative normal velocity between two bodies to go to zero. This time scale tc is artificially introduced by the penalty method and goes to zero in the limit to ideal rigid contact. Since numerical integration methods for continuum systems must be able to resolve a system's dynamics, the time step used by an integrator must in general be much smaller than the time scale tc. How much smaller will depend on the details of the problem and the convergence characteristics of the integrator and should be tuned appropriately. Another factor to take into account for setting up the simulation's time step is the speed of the objects in your simulation. If vn represents a reference velocity scale for the normal relative velocity between bodies, the new time scale tn = δ / vn represents the time it would take for the distance between two bodies approaching with relative normal velocity vn to decrease by the penetration_allowance δ. In this case a user should choose a time step for simulation that can resolve the smallest of the two time scales tc and tn.
◆ get_contact_results_output_port()
| const systems::OutputPort< T > & get_contact_results_output_port | ( | ) | const |
Returns a constant reference to the port that outputs ContactResults.
- Exceptions
-
std::exception if thisplant is not modeled as a discrete system with periodic updates.std::exception if called pre-finalize, see Finalize().
◆ get_frame()
| const Frame<T>& get_frame | ( | FrameIndex | frame_index | ) | const |
Returns a constant reference to the frame with unique index frame_index.
- Exceptions
-
std::exception if frame_indexdoes not correspond to a frame in this plant.
◆ get_generalized_contact_forces_output_port()
| const systems::OutputPort< T > & get_generalized_contact_forces_output_port | ( | ModelInstanceIndex | model_instance | ) | const |
Returns a constant reference to the output port of generalized contact forces for a specific model instance.
This output port is only available when modeling the plant as a discrete system with periodic updates, see is_discrete().
- Precondition
- Finalize() was already called on
thisplant.
- Exceptions
-
std::exception if thisplant is not modeled as a discrete system with periodic updates.std::exception if called before Finalize() or if the model instance does not have any generalized velocities. std::exception if the model instance does not exist.
◆ get_geometry_poses_output_port()
| const OutputPort< T > & get_geometry_poses_output_port | ( | ) | const |
Returns the output port of frames' poses to communicate with a SceneGraph.
- Exceptions
-
std::exception if this system was not registered with a SceneGraph.
◆ get_geometry_query_input_port()
| const systems::InputPort< T > & get_geometry_query_input_port | ( | ) | const |
Returns a constant reference to the input port used to perform geometric queries on a SceneGraph.
See SceneGraph::get_query_output_port(). Refer to section Registering geometry with a SceneGraph of this class's documentation for further details on collision geometry registration and connection with a SceneGraph.
- Exceptions
-
std::exception if this system was not registered with a SceneGraph.
◆ get_joint()
| const Joint<T>& get_joint | ( | JointIndex | joint_index | ) | const |
Returns a constant reference to the joint with unique index joint_index.
- Exceptions
-
std::runtime_error when joint_indexdoes not correspond to a joint in this model.
◆ get_joint_actuator()
| const JointActuator<T>& get_joint_actuator | ( | JointActuatorIndex | actuator_index | ) | const |
Returns a constant reference to the joint actuator with unique index actuator_index.
- Exceptions
-
std::exception if actuator_indexdoes not correspond to a joint actuator in this tree.
◆ get_mutable_joint()
| Joint<T>& get_mutable_joint | ( | JointIndex | joint_index | ) |
Returns a mutable reference to the joint with unique index joint_index.
- Exceptions
-
std::runtime_error when joint_indexdoes not correspond to a joint in this model.
◆ get_source_id()
| optional<geometry::SourceId> get_source_id | ( | ) | const |
Returns the unique id identifying this plant as a source for a SceneGraph.
Returns nullopt if this plant did not register any geometry. This method can be called at any time during the lifetime of this plant to query if this plant has been registered with a SceneGraph, either pre- or post-finalize, see Finalize(). However, a geometry::SourceId is only assigned once at the first call of any of this plant's geometry registration methods, and it does not change after that. Post-finalize calls will always return the same value.
◆ get_state_output_port() [1/2]
| const systems::OutputPort< T > & get_state_output_port | ( | ) | const |
Returns a constant reference to the output port for the full state x = [q v] of the model.
- Precondition
- Finalize() was already called on
thisplant.
◆ get_state_output_port() [2/2]
| const systems::OutputPort< T > & get_state_output_port | ( | ModelInstanceIndex | model_instance | ) | const |
Returns a constant reference to the output port for the state of a specific model instance.
- Precondition
- Finalize() was already called on
thisplant.
- Exceptions
-
std::exception if called before Finalize() or if the model instance does not have any state. std::exception if the model instance does not exist.
◆ GetAccelerationLowerLimits()
Returns a vector of size num_velocities() containing the lower acceleration limits for every generalized velocity coordinate.
These include joint and floating base coordinates. Any unbounded or unspecified limits will be -infinity.
- Exceptions
-
std::logic_error if called pre-finalize.
◆ GetAccelerationUpperLimits()
Upper limit analog of GetAccelerationsLowerLimits(), where any unbounded or unspecified limits will be +infinity.
- See also
- GetAccelerationLowerLimits() for more information.
◆ GetBodiesWeldedTo()
Returns all bodies that are transitively welded, or rigidly affixed, to body, per these two definitions:
- A body is always considered welded to itself.
- Two unique bodies are considered welded together exclusively by the presence of a weld joint, not by other constructs that prevent mobility (e.g. constraints).
This method can be called at any time during the lifetime of this plant, either pre- or post-finalize, see Finalize().
Meant to be used with CollectRegisteredGeometries.
The following example demonstrates filtering collisions between all bodies rigidly affixed to a door (which could be moving) and all bodies rigidly affixed to the world:
- Note
- Usages akin to this example may introduce redundant collision filtering; this will not have a functional impact, but may have a minor performance impact.
- Returns
- all bodies rigidly fixed to
body. This does not return the bodies in any prescribed order.
- Exceptions
-
std::exception if bodyis not part of this plant.
◆ GetBodyByName() [1/2]
| const Body<T>& GetBodyByName | ( | const std::string & | name | ) | const |
These queries can be performed at any time during the lifetime of a MultibodyPlant, i.e.
there is no restriction on whether they must be called before or after Finalize(). This implies that these queries can be performed while new multibody elements are being added to the model.
If the named element is present in more than one model instance and a model instance is not explicitly specified, std::logic_error is thrown.Returns a constant reference to a body that is identified by the string name in this MultibodyPlant.
- Exceptions
-
std::logic_error if there is no body with the requested name. std::logic_error if the body name occurs in multiple model instances.
- See also
- HasBodyNamed() to query if there exists a body in
thisMultibodyPlant with a given specified name.
◆ GetBodyByName() [2/2]
| const Body<T>& GetBodyByName | ( | const std::string & | name, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
Returns a constant reference to the body that is uniquely identified by the string name and model_instance in this MultibodyPlant.
- Exceptions
-
std::logic_error if there is no body with the requested name.
- See also
- HasBodyNamed() to query if there exists a body in
thisMultibodyPlant with a given specified name.
◆ GetBodyFrameIdIfExists()
| optional<geometry::FrameId> GetBodyFrameIdIfExists | ( | BodyIndex | body_index | ) | const |
If the body with body_index has geometry registered with it, it returns the geometry::FrameId associated with it.
Otherwise, it returns nullopt.
◆ GetBodyFrameIdOrThrow()
| geometry::FrameId GetBodyFrameIdOrThrow | ( | BodyIndex | body_index | ) | const |
If the body with body_index has geometry registered with it, it returns the geometry::FrameId associated with it.
Otherwise this method throws an exception.
- Exceptions
-
std::exception if no geometry has been registered with the body indicated by body_index.
◆ GetBodyFromFrameId()
| const Body<T>* GetBodyFromFrameId | ( | geometry::FrameId | frame_id | ) | const |
Given a geometry frame identifier, returns a pointer to the body associated with that id (nullptr if there is no such body).
◆ GetBodyIndices()
| std::vector<BodyIndex> GetBodyIndices | ( | ModelInstanceIndex | model_instance | ) | const |
Returns a list of body indices associated with model_instance.
◆ GetCollisionGeometriesForBody()
| const std::vector< geometry::GeometryId > & GetCollisionGeometriesForBody | ( | const Body< T > & | body | ) | const |
Returns an array of GeometryId's identifying the different contact geometries for body previously registered with a SceneGraph.
- Note
- This method can be called at any time during the lifetime of
thisplant, either pre- or post-finalize, see Finalize(). Post-finalize calls will always return the same value.
- See also
- RegisterCollisionGeometry(), Finalize()
◆ GetFloatingBaseBodies()
| std::unordered_set< BodyIndex > GetFloatingBaseBodies | ( | ) | const |
Returns the set of body indexes corresponding to the "floating bodies" in the model, in no particular order.
- Exceptions
-
std::exception if called pre-finalize, see Finalize().
◆ GetFrameByName() [1/2]
| const Frame<T>& GetFrameByName | ( | const std::string & | name | ) | const |
Returns a constant reference to a frame that is identified by the string name in this model.
- Exceptions
-
std::logic_error if there is no frame with the requested name. std::logic_error if the frame name occurs in multiple model instances.
- See also
- HasFrameNamed() to query if there exists a frame in
thismodel with a given specified name.
◆ GetFrameByName() [2/2]
| const Frame<T>& GetFrameByName | ( | const std::string & | name, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
Returns a constant reference to the frame that is uniquely identified by the string name in model_instance.
- Exceptions
-
std::logic_error if there is no frame with the requested name. std::runtime_error if model_instanceis not valid for this model.
- See also
- HasFrameNamed() to query if there exists a frame in
thismodel with a given specified name.
◆ GetFreeBodyPose()
| math::RigidTransform<T> GetFreeBodyPose | ( | const systems::Context< T > & | context, |
| const Body< T > & | body | ||
| ) | const |
Gets the pose of a given body in the world frame W.
- Note
- In general getting the pose of a body in the model would involve solving the kinematics. This method allows us to simplify this process when we know the body is free in space.
- Exceptions
-
std::exception if bodyis not a free body in the model.std::exception if called pre-finalize.
◆ GetJointActuatorByName() [1/2]
| const JointActuator<T>& GetJointActuatorByName | ( | const std::string & | name | ) | const |
Returns a constant reference to an actuator that is identified by the string name in this MultibodyPlant.
- Exceptions
-
std::logic_error if there is no actuator with the requested name. std::logic_error if the actuator name occurs in multiple model instances.
- See also
- HasJointActuatorNamed() to query if there exists an actuator in
thisMultibodyPlant with a given specified name.
◆ GetJointActuatorByName() [2/2]
| const JointActuator<T>& GetJointActuatorByName | ( | const std::string & | name, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
Returns a constant reference to the actuator that is uniquely identified by the string name and model_instance in this MultibodyPlant.
- Exceptions
-
std::logic_error if there is no actuator with the requested name. std::exception if model_instanceis not valid for this model.
- See also
- HasJointActuatorNamed() to query if there exists an actuator in
thisMultibodyPlant with a given specified name.
◆ GetJointByName()
| const JointType<T>& GetJointByName | ( | const std::string & | name, |
| optional< ModelInstanceIndex > | model_instance = nullopt |
||
| ) | const |
Returns a constant reference to a joint that is identified by the string name in this MultibodyPlant.
If the optional template argument is supplied, then the returned value is downcast to the specified JointType.
- Template Parameters
-
JointType The specific type of the Joint to be retrieved. It must be a subclass of Joint.
- Exceptions
-
std::logic_error if the named joint is not of type JointTypeor if there is no Joint with that name.std::exception if model_instanceis not valid for this model.
- See also
- HasJointNamed() to query if there exists a joint in
thisMultibodyPlant with a given specified name.
◆ GetJointIndices()
| std::vector<JointIndex> GetJointIndices | ( | ModelInstanceIndex | model_instance | ) | const |
Returns a list of joint indices associated with model_instance.
◆ GetModelInstanceByName()
| ModelInstanceIndex GetModelInstanceByName | ( | const std::string & | name | ) | const |
Returns the index to the model instance that is uniquely identified by the string name in this MultibodyPlant.
- Exceptions
-
std::logic_error if there is no instance with the requested name.
- See also
- HasModelInstanceNamed() to query if there exists an instance in
thisMultibodyPlant with a given specified name.
◆ GetModelInstanceName()
| const std::string& GetModelInstanceName | ( | ModelInstanceIndex | model_instance | ) | const |
Returns the name of a model_instance.
- Exceptions
-
std::logic_error when model_instancedoes not correspond to a model in this model.
◆ GetMutableJointByName()
| JointType<T>& GetMutableJointByName | ( | const std::string & | name, |
| optional< ModelInstanceIndex > | model_instance = nullopt |
||
| ) |
A version of GetJointByName that returns a mutable reference.
- See also
- GetJointByName.
◆ GetMutablePositions() [1/2]
| Eigen::VectorBlock<VectorX<T> > GetMutablePositions | ( | systems::Context< T > * | context | ) | const |
(Advanced) Returns a mutable vector reference containing the vector of generalized positions (see warning).
- Note
- This method returns a reference to existing data, exhibits constant i.e., O(1) time complexity, and runs very quickly.
- Warning
- You should use SetPositions() instead of this method unless you are fully aware of the possible interactions with the caching mechanism (see dangerous_get_mutable).
- Exceptions
-
std::exception if the contextis nullptr or if it does not correspond to the context for a multibody model.
◆ GetMutablePositions() [2/2]
| Eigen::VectorBlock<VectorX<T> > GetMutablePositions | ( | const systems::Context< T > & | context, |
| systems::State< T > * | state | ||
| ) | const |
(Advanced) Returns a mutable vector reference containing the vector of generalized positions (see warning).
- Note
- This method returns a reference to existing data, exhibits constant i.e., O(1) time complexity, and runs very quickly.
- Warning
- You should use SetPositions() instead of this method unless you are fully aware of the possible interactions with the caching mechanism (see dangerous_get_mutable).
- Exceptions
-
std::exception if the stateis nullptr or if the context does not correspond to the context for a multibody model.
- Precondition
statecomes from this MultibodyPlant.
◆ GetMutablePositionsAndVelocities()
| Eigen::VectorBlock<VectorX<T> > GetMutablePositionsAndVelocities | ( | systems::Context< T > * | context | ) | const |
(Advanced) Returns a mutable vector containing the vector [q; v] of the model with q the vector of generalized positions and v the vector of generalized velocities (see warning).
- Warning
- You should use SetPositionsAndVelocities() instead of this method unless you are fully aware of the interactions with the caching mechanism (see dangerous_get_mutable).
- Exceptions
-
std::exception if the contextis nullptr or if it does not correspond to the context for a multibody model.
◆ GetMutableVelocities() [1/2]
| Eigen::VectorBlock<VectorX<T> > GetMutableVelocities | ( | const systems::Context< T > & | context, |
| systems::State< T > * | state | ||
| ) | const |
(Advanced) Returns a mutable vector reference containing the vector of generalized velocities (see warning).
- Note
- This method returns a reference to existing data, exhibits constant i.e., O(1) time complexity, and runs very quickly.
- Warning
- You should use SetVelocities() instead of this method unless you are fully aware of the possible interactions with the caching mechanism (see dangerous_get_mutable).
- Exceptions
-
std::exception if the contextis nullptr or the context does not correspond to the context for a multibody model.
- Precondition
statecomes from this MultibodyPlant.
◆ GetMutableVelocities() [2/2]
| Eigen::VectorBlock<VectorX<T> > GetMutableVelocities | ( | systems::Context< T > * | context | ) | const |
See GetMutableVelocities() method above.
◆ GetPositionLowerLimits()
Returns a vector of size num_positions() containing the lower position limits for every generalized position coordinate.
These include joint and floating base coordinates. Any unbounded or unspecified limits will be -infinity.
- Exceptions
-
std::logic_error if called pre-finalize.
◆ GetPositions() [1/2]
| Eigen::VectorBlock<const VectorX<T> > GetPositions | ( | const systems::Context< T > & | context | ) | const |
Returns a const vector reference containing the vector of generalized positions.
- Note
- This method returns a reference to existing data, exhibits constant i.e., O(1) time complexity, and runs very quickly.
- Exceptions
-
std::exception if the contextdoes not correspond to the context for a multibody model.
◆ GetPositions() [2/2]
| VectorX<T> GetPositions | ( | const systems::Context< T > & | context, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
Returns an vector containing the generalized positions (q) for the given model instance.
- Exceptions
-
std::exception if the contextdoes not correspond to the context for a multibody model.
- Note
- returns a dense vector of dimension
q.size()associated withmodel_instancein O(q.size()) time.
◆ GetPositionsAndVelocities() [1/2]
| Eigen::VectorBlock<const VectorX<T> > GetPositionsAndVelocities | ( | const systems::Context< T > & | context | ) | const |
Returns a const vector reference containing the vector [q; v] with q the vector of generalized positions and v the vector of generalized velocities.
- Note
- This method returns a reference to existing data, exhibits constant i.e., O(1) time complexity, and runs very quickly.
- Exceptions
-
std::exception if the contextdoes not correspond to the context for a multibody model.
◆ GetPositionsAndVelocities() [2/2]
| VectorX<T> GetPositionsAndVelocities | ( | const systems::Context< T > & | context, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
Returns the vector [q; v] of the model with q the vector of generalized positions and v the vector of generalized velocities for model instance model_instance.
- Exceptions
-
std::exception if the contextdoes not correspond to the context for a multibody model ormodel_instanceis invalid.
- Note
- returns a dense vector of dimension
q.size() + v.size()associated withmodel_instancein O(q.size()) time.
◆ GetPositionsFromArray()
| VectorX<T> GetPositionsFromArray | ( | ModelInstanceIndex | model_instance, |
| const Eigen::Ref< const VectorX< T >> & | q | ||
| ) | const |
Returns a vector of generalized positions for model_instance from a vector q_array of generalized positions for the entire model model.
This method throws an exception if q is not of size MultibodyPlant::num_positions().
◆ GetPositionUpperLimits()
Upper limit analog of GetPositionsLowerLimits(), where any unbounded or unspecified limits will be +infinity.
- See also
- GetPositionLowerLimits() for more information.
◆ GetRigidBodyByName() [1/2]
| const RigidBody<T>& GetRigidBodyByName | ( | const std::string & | name | ) | const |
Returns a constant reference to a rigid body that is identified by the string name in this model.
- Exceptions
-
std::logic_error if there is no body with the requested name. std::logic_error if the body name occurs in multiple model instances. std::logic_error if the requested body is not a RigidBody.
- See also
- HasBodyNamed() to query if there exists a body in
thismodel with a given specified name.
◆ GetRigidBodyByName() [2/2]
| const RigidBody<T>& GetRigidBodyByName | ( | const std::string & | name, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
Returns a constant reference to the rigid body that is uniquely identified by the string name in model_instance.
- Exceptions
-
std::logic_error if there is no body with the requested name. std::logic_error if the requested body is not a RigidBody. std::runtime_error if model_instanceis not valid for this model.
- See also
- HasBodyNamed() to query if there exists a body in
thismodel with a given specified name.
◆ GetVelocities() [1/2]
| Eigen::VectorBlock<const VectorX<T> > GetVelocities | ( | const systems::Context< T > & | context | ) | const |
Returns a const vector reference containing the generalized velocities.
- Note
- This method returns a reference to existing data, exhibits constant i.e., O(1) time complexity, and runs very quickly.
◆ GetVelocities() [2/2]
| VectorX<T> GetVelocities | ( | const systems::Context< T > & | context, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
Returns a vector containing the generalized velocities (v) for the given model instance.
- Exceptions
-
std::exception if the contextdoes not correspond to the context for a multibody model.
- Note
- returns a dense vector of dimension
v.size()associated withmodel_instancein O(v.size()) time.
◆ GetVelocitiesFromArray()
| VectorX<T> GetVelocitiesFromArray | ( | ModelInstanceIndex | model_instance, |
| const Eigen::Ref< const VectorX< T >> & | v | ||
| ) | const |
Returns a vector of generalized velocities for model_instance from a vector v of generalized velocities for the entire MultibodyPlant model.
This method throws an exception if the input array is not of size MultibodyPlant::num_velocities().
◆ GetVelocityLowerLimits()
Returns a vector of size num_velocities() containing the lower velocity limits for every generalized velocity coordinate.
These include joint and floating base coordinates. Any unbounded or unspecified limits will be -infinity.
- Exceptions
-
std::logic_error if called pre-finalize.
◆ GetVelocityUpperLimits()
Upper limit analog of GetVelocitysLowerLimits(), where any unbounded or unspecified limits will be +infinity.
- See also
- GetVelocityLowerLimits() for more information.
◆ GetVisualGeometriesForBody()
| const std::vector< geometry::GeometryId > & GetVisualGeometriesForBody | ( | const Body< T > & | body | ) | const |
Returns an array of GeometryId's identifying the different visual geometries for body previously registered with a SceneGraph.
- Note
- This method can be called at any time during the lifetime of
thisplant, either pre- or post-finalize, see Finalize(). Post-finalize calls will always return the same value.
- See also
- RegisterVisualGeometry(), Finalize()
◆ gravity_field()
| const UniformGravityFieldElement<T>& gravity_field | ( | ) | const |
An accessor to the current gravity field.
◆ HasBodyNamed() [1/2]
| bool HasBodyNamed | ( | const std::string & | name | ) | const |
- Returns
trueif a body namednamewas added to the MultibodyPlant.
- See also
- AddRigidBody().
- Exceptions
-
std::logic_error if the body name occurs in multiple model instances.
◆ HasBodyNamed() [2/2]
| bool HasBodyNamed | ( | const std::string & | name, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
- Returns
trueif a body namednamewas added to the MultibodyPlant inmodel_instance.
- See also
- AddRigidBody().
- Exceptions
-
std::exception if model_instanceis not valid for this model.
◆ HasFrameNamed() [1/2]
| bool HasFrameNamed | ( | const std::string & | name | ) | const |
- Returns
trueif a frame namednamewas added to the model.
- See also
- AddFrame().
- Exceptions
-
std::logic_error if the frame name occurs in multiple model instances.
◆ HasFrameNamed() [2/2]
| bool HasFrameNamed | ( | const std::string & | name, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
- Returns
trueif a frame namednamewas added tomodel_instance.
- See also
- AddFrame().
- Exceptions
-
std::exception if model_instanceis not valid for this model.
◆ HasJointActuatorNamed() [1/2]
| bool HasJointActuatorNamed | ( | const std::string & | name | ) | const |
- Returns
trueif an actuator namednamewas added to this model.
- See also
- AddJointActuator().
- Exceptions
-
std::logic_error if the actuator name occurs in multiple model instances.
◆ HasJointActuatorNamed() [2/2]
| bool HasJointActuatorNamed | ( | const std::string & | name, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
- Returns
trueif an actuator namednamewas added tomodel_instance.
- See also
- AddJointActuator().
- Exceptions
-
std::exception if model_instanceis not valid for this model.
◆ HasJointNamed() [1/2]
| bool HasJointNamed | ( | const std::string & | name | ) | const |
- Returns
trueif a joint namednamewas added to this model.
- See also
- AddJoint().
- Exceptions
-
std::logic_error if the joint name occurs in multiple model instances.
◆ HasJointNamed() [2/2]
| bool HasJointNamed | ( | const std::string & | name, |
| ModelInstanceIndex | model_instance | ||
| ) | const |
- Returns
trueif a joint namednamewas added tomodel_instance.
- See also
- AddJoint().
- Exceptions
-
std::exception if model_instanceis not valid for this model.
◆ HasModelInstanceNamed()
| bool HasModelInstanceNamed | ( | const std::string & | name | ) | const |
- Returns
trueif a model instance namednamewas added to this model.
- See also
- AddModelInstance().
◆ is_finalized()
| bool is_finalized | ( | ) | const |
Returns true if this MultibodyPlant was finalized with a call to Finalize().
- See also
- Finalize().
◆ IsAnchored()
Returns true if body is anchored (i.e.
the kinematic path between body and the world only contains weld joints.)
- Exceptions
-
std::exception if called pre-finalize.
◆ MakeActuationMatrix()
| MatrixX< T > MakeActuationMatrix | ( | ) | const |
This method creates an actuation matrix B mapping a vector of actuation values u into generalized forces tau_u = B * u, where B is a matrix of size nv x nu with nu equal to num_actuators() and nv equal to num_velocities().
The vector u of actuation values is of size num_actuators(). For a given JointActuator, u[JointActuator::index()] stores the value for the external actuation corresponding to that actuator. tau_u on the other hand is indexed by generalized velocity indexes according to Joint::velocity_start().
- Warning
- B is a permutation matrix. While making a permutation has
O(n)complexity, making a full B matrix hasO(n²)complexity. For most applications this cost can be neglected but it could become significant for very large systems.
◆ MakeActuatorSelectorMatrix() [1/2]
| MatrixX<double> MakeActuatorSelectorMatrix | ( | const std::vector< JointActuatorIndex > & | user_to_actuator_index_map | ) | const |
This method allows user to map a vector uₛ containing the actuation for a set of selected actuators into the vector u containing the actuation values for this full model.
The mapping, or selection, is returned in the form of a selector matrix Su such that u = Su⋅uₛ. The size nₛ of uₛ is always smaller or equal than the size of the full vector of actuation values u. That is, a user might be interested in only a given subset of actuators in the model.
This selection matrix is particularly useful when adding PID control on a portion of the state, see systems::controllers::PidController.
A user specifies the preferred order in uₛ via user_to_actuator_index_map. The actuation values in uₛ are a concatenation of the values for each actuator in the order they appear in user_to_actuator_index_map. The full vector of actuation values u is ordered by JointActuatorIndex.
◆ MakeActuatorSelectorMatrix() [2/2]
| MatrixX<double> MakeActuatorSelectorMatrix | ( | const std::vector< JointIndex > & | user_to_joint_index_map | ) | const |
Alternative signature to build an actuation selector matrix Su such that u = Su⋅uₛ, where u is the vector of actuation values for the full model (ordered by JointActuatorIndex) and uₛ is a vector of actuation values for the actuators acting on the joints listed by user_to_joint_index_map.
It is assumed that all joints referenced by user_to_joint_index_map are actuated. See MakeActuatorSelectorMatrix(const std::vector<JointActuatorIndex>&) for details.
- Exceptions
-
std::logic_error if any of the joints in user_to_joint_index_mapdoes not have an actuator.
◆ MakeStateSelectorMatrix()
| MatrixX<double> MakeStateSelectorMatrix | ( | const std::vector< JointIndex > & | user_to_joint_index_map | ) | const |
This method allows users to map the state of this model, x, into a vector of selected state xₛ with a given preferred ordering.
The mapping, or selection, is returned in the form of a selector matrix Sx such that xₛ = Sx⋅x. The size nₛ of xₛ is always smaller or equal than the size of the full state x. That is, a user might be interested in only a given portion of the full state x.
This selection matrix is particularly useful when adding PID control on a portion of the state, see systems::controllers::PidController.
A user specifies the preferred order in xₛ via user_to_joint_index_map. The selected state is built such that selected positions are followed by selected velocities, as in xₛ = [qₛ, vₛ]. The positions in qₛ are a concatenation of the positions for each joint in the order they appear in user_to_joint_index_map. That is, the positions for user_to_joint_index_map[0] are first, followed by the positions for user_to_joint_index_map[1], etc. Similarly for the selected velocities vₛ.
- Exceptions
-
std::logic_error if there are repeated indexes in user_to_joint_index_map.
◆ MapQDotToVelocity()
| void MapQDotToVelocity | ( | const systems::Context< T > & | context, |
| const Eigen::Ref< const VectorX< T >> & | qdot, | ||
| EigenPtr< VectorX< T >> | v | ||
| ) | const |
Transforms the time derivative qdot of the generalized positions vector q (stored in context) to generalized velocities v.
v and q̇ are related linearly by q̇ = N(q)⋅v. Although N(q) is not necessarily square, its left pseudo-inverse N⁺(q) can be used to invert that relationship without residual error, provided that qdot is in the range space of N(q) (that is, if it could have been produced as q̇ = N(q)⋅v for some v). Using the configuration q stored in the given context this method calculates v = N⁺(q)⋅q̇.
- Parameters
-
[in] context The context containing the state of the model. [in] qdot A vector containing the time derivatives of the generalized positions. This method aborts if qdotis not of size num_positions().[out] v A valid (non-null) pointer to a vector in ℛⁿwith n the number of generalized velocities. This method aborts if v is nullptr or if it is not of size num_velocities().
- See also
- MapVelocityToQDot()
- Mobilizer::MapQDotToVelocity()
◆ MapVelocityToQDot()
| void MapVelocityToQDot | ( | const systems::Context< T > & | context, |
| const Eigen::Ref< const VectorX< T >> & | v, | ||
| EigenPtr< VectorX< T >> | qdot | ||
| ) | const |
Transforms generalized velocities v to time derivatives qdot of the generalized positions vector q (stored in context).
v and qdot are related linearly by q̇ = N(q)⋅v. Using the configuration q stored in the given context this method calculates q̇ = N(q)⋅v.
- Parameters
-
[in] context The context containing the state of the model. [in] v A vector of of generalized velocities for this model. This method aborts if v is not of size num_velocities(). [out] qdot A valid (non-null) pointer to a vector in ℝⁿwith n being the number of generalized positions in this model, given bynum_positions(). This method aborts ifqdotis nullptr or if it is not of size num_positions().
- See also
- MapQDotToVelocity()
- Mobilizer::MapVelocityToQDot()
◆ mutable_gravity_field()
| UniformGravityFieldElement<T>& mutable_gravity_field | ( | ) |
A mutable accessor to the current gravity field.
◆ num_actuated_dofs() [1/2]
| int num_actuated_dofs | ( | ) | const |
Returns the total number of actuated degrees of freedom.
That is, the vector of actuation values u has this size. See AddJointActuator().
◆ num_actuated_dofs() [2/2]
| int num_actuated_dofs | ( | ModelInstanceIndex | model_instance | ) | const |
Returns the total number of actuated degrees of freedom for a specific model instance.
That is, the vector of actuation values u has this size. See AddJointActuator().
◆ num_actuators()
| int num_actuators | ( | ) | const |
Returns the number of joint actuators in the model.
- See also
- AddJointActuator().
◆ num_bodies()
| int num_bodies | ( | ) | const |
Returns the number of bodies in the model, including the "world" body, which is always part of the model.
- See also
- AddRigidBody().
◆ num_collision_geometries()
| int num_collision_geometries | ( | ) | const |
Returns the number of geometries registered for contact modeling.
This method can be called at any time during the lifetime of this plant, either pre- or post-finalize, see Finalize(). Post-finalize calls will always return the same value.
◆ num_force_elements()
| int num_force_elements | ( | ) | const |
Returns the number of ForceElement objects.
- See also
- AddForceElement().
◆ num_frames()
| int num_frames | ( | ) | const |
Returns the number of Frame objects in this model.
Frames include body frames associated with each of the bodies, including the world body. This means the minimum number of frames is one.
◆ num_joints()
| int num_joints | ( | ) | const |
Returns the number of joints in the model.
- See also
- AddJoint().
◆ num_model_instances()
| int num_model_instances | ( | ) | const |
Returns the number of model instances in the model.
- See also
- AddModelInstance().
◆ num_multibody_states()
| int num_multibody_states | ( | ) | const |
Returns the size of the multibody system state vector x = [q; v].
This will be num_positions() plus num_velocities().
◆ num_positions() [1/2]
| int num_positions | ( | ) | const |
Returns the size of the generalized position vector q for this model.
◆ num_positions() [2/2]
| int num_positions | ( | ModelInstanceIndex | model_instance | ) | const |
Returns the size of the generalized position vector q for a specific model instance.
◆ num_velocities() [1/2]
| int num_velocities | ( | ) | const |
Returns the size of the generalized velocity vector v for this model.
◆ num_velocities() [2/2]
| int num_velocities | ( | ModelInstanceIndex | model_instance | ) | const |
Returns the size of the generalized velocity vector v for a specific model instance.
◆ num_visual_geometries()
| int num_visual_geometries | ( | ) | const |
Returns the number of geometries registered for visualization.
This method can be called at any time during the lifetime of this plant, either pre- or post-finalize, see Finalize(). Post-finalize calls will always return the same value.
◆ operator=() [1/2]
|
delete |
◆ operator=() [2/2]
|
delete |
◆ RegisterAsSourceForSceneGraph()
| geometry::SourceId RegisterAsSourceForSceneGraph | ( | geometry::SceneGraph< T > * | scene_graph | ) |
Registers this plant to serve as a source for an instance of SceneGraph.
This registration allows MultibodyPlant to register geometry with scene_graph for visualization and/or collision queries. Successive registration calls with SceneGraph must be performed on the same instance to which the pointer argument scene_graph points to. Failure to do so will result in runtime exceptions.
- Parameters
-
scene_graph A valid non nullptr to the SceneGraph instance for which thisplant will sever as a source, see SceneGraph documentation for further details.
- Returns
- the SourceId of
thisplant inscene_graph. It can also later on be retrieved with get_source_id().
- Exceptions
-
std::exception if called post-finalize. std::exception if scene_graphis the nullptr.std::exception if called more than once.
◆ RegisterCollisionGeometry() [1/2]
| geometry::GeometryId RegisterCollisionGeometry | ( | const Body< T > & | body, |
| const math::RigidTransform< double > & | X_BG, | ||
| const geometry::Shape & | shape, | ||
| const std::string & | name, | ||
| const CoulombFriction< double > & | coulomb_friction | ||
| ) |
Registers geometry in a SceneGraph with a given geometry::Shape to be used for the contact modeling of a given body.
More than one geometry can be registered with a body, in which case the body's contact geometry is the union of all geometries registered to that body.
- Parameters
-
[in] body The body for which geometry is being registered. [in] X_BG The fixed pose of the geometry frame G in the body frame B. [in] shape The geometry::Shape used for visualization. E.g.: geometry::Sphere, geometry::Cylinder, etc. [in] coulomb_friction Coulomb's law of friction coefficients to model friction on the surface of shapefor the givenbody.
- Exceptions
-
std::exception if called post-finalize.
◆ RegisterCollisionGeometry() [2/2]
| geometry::GeometryId RegisterCollisionGeometry | ( | const Body< T > & | body, |
| const math::RigidTransform< double > & | X_BG, | ||
| const geometry::Shape & | shape, | ||
| const std::string & | name, | ||
| const CoulombFriction< double > & | coulomb_friction, | ||
| geometry::SceneGraph< T > * | scene_graph | ||
| ) |
(Do not use.) This is a deprecated overload that takes a scene_graph argument.
- Exceptions
-
std::exception if scene_graphdoes not correspond to the same instance with which RegisterAsSourceForSceneGraph() was called. (Deprecated.)
- Deprecated:
- "Remove the scene_graph argument at the call site; instead of passing a " "scene_graph pointer, call RegisterAsSourceForSceneGraph first, instead."
This will be removed from Drake on or after "2019-10-01" .
◆ RegisterVisualGeometry() [1/6]
| geometry::GeometryId RegisterVisualGeometry | ( | const Body< T > & | body, |
| const math::RigidTransform< double > & | X_BG, | ||
| const geometry::Shape & | shape, | ||
| const std::string & | name, | ||
| const geometry::IllustrationProperties & | properties | ||
| ) |
Registers geometry in a SceneGraph with a given geometry::Shape to be used for visualization of a given body.
- Note
- Currently, the visual geometry will also be assigned a perception role. Its render label's value will be equal to the body's index and its perception color will be the same as its illustration color (defaulting to gray if no color is provided). This behavior will change in the near future and code that directly relies on this behavior will break.
- Parameters
-
[in] body The body for which geometry is being registered. [in] X_BG The fixed pose of the geometry frame G in the body frame B. [in] shape The geometry::Shape used for visualization. E.g.: geometry::Sphere, geometry::Cylinder, etc. [in] name The name for the geometry. It must satisfy the requirements defined in drake::geometry::GeometryInstance. [in] properties The illustration properties for this geometry.
- Exceptions
-
std::exception if called post-finalize. std::exception if scene_graphdoes not correspond to the same instance with which RegisterAsSourceForSceneGraph() was called.
- Returns
- the id for the registered geometry.
◆ RegisterVisualGeometry() [2/6]
| geometry::GeometryId RegisterVisualGeometry | ( | const Body< T > & | body, |
| const math::RigidTransform< double > & | X_BG, | ||
| const geometry::Shape & | shape, | ||
| const std::string & | name, | ||
| const geometry::IllustrationProperties & | properties, | ||
| geometry::SceneGraph< T > * | scene_graph | ||
| ) |
(Do not use.) This is a deprecated overload that takes a scene_graph argument.
(Deprecated.)
- Deprecated:
- "Remove the scene_graph argument at the call site; instead of passing a " "scene_graph pointer, call RegisterAsSourceForSceneGraph first, instead."
This will be removed from Drake on or after "2019-10-01" .
◆ RegisterVisualGeometry() [3/6]
| geometry::GeometryId RegisterVisualGeometry | ( | const Body< T > & | body, |
| const math::RigidTransform< double > & | X_BG, | ||
| const geometry::Shape & | shape, | ||
| const std::string & | name, | ||
| const Vector4< double > & | diffuse_color | ||
| ) |
Overload for visual geometry registration; it converts the diffuse_color (RGBA with values in the range [0, 1]) into a geometry::ConnectDrakeVisualizer()-compatible set of geometry::IllustrationProperties.
◆ RegisterVisualGeometry() [4/6]
| geometry::GeometryId RegisterVisualGeometry | ( | const Body< T > & | body, |
| const math::RigidTransform< double > & | X_BG, | ||
| const geometry::Shape & | shape, | ||
| const std::string & | name, | ||
| const Vector4< double > & | diffuse_color, | ||
| geometry::SceneGraph< T > * | scene_graph | ||
| ) |
(Do not use.) This is a deprecated overload that takes a scene_graph argument.
(Deprecated.)
- Deprecated:
- "Remove the scene_graph argument at the call site; instead of passing a " "scene_graph pointer, call RegisterAsSourceForSceneGraph first, instead."
This will be removed from Drake on or after "2019-10-01" .
◆ RegisterVisualGeometry() [5/6]
| geometry::GeometryId RegisterVisualGeometry | ( | const Body< T > & | body, |
| const math::RigidTransform< double > & | X_BG, | ||
| const geometry::Shape & | shape, | ||
| const std::string & | name | ||
| ) |
Overload for visual geometry registration; it relies on the downstream geometry::IllustrationProperties consumer to provide default parameter values (see Geometry Roles for details).
◆ RegisterVisualGeometry() [6/6]
| geometry::GeometryId RegisterVisualGeometry | ( | const Body< T > & | body, |
| const math::RigidTransform< double > & | X_BG, | ||
| const geometry::Shape & | shape, | ||
| const std::string & | name, | ||
| geometry::SceneGraph< T > * | scene_graph | ||
| ) |
(Do not use.) This is a deprecated overload that takes a scene_graph argument.
(Deprecated.)
- Deprecated:
- "Remove the scene_graph argument at the call site; instead of passing a " "scene_graph pointer, call RegisterAsSourceForSceneGraph first, instead."
This will be removed from Drake on or after "2019-10-01" .
◆ set_elastic_modulus()
| void set_elastic_modulus | ( | geometry::GeometryId | id, |
| double | elastic_modulus | ||
| ) |
Specifies the elastic_modulus for a geometry identified by its id.
- Exceptions
-
std::exception if iddoes not correspond to a collision geometry previously registered with this model.std::exception if called post-finalize.
◆ set_penetration_allowance()
| void set_penetration_allowance | ( | double | penetration_allowance = 0.001 | ) |
Sets the penetration allowance used to estimate the coefficients in the penalty method used to impose non-penetration among bodies.
Refer to the section Contact by penalty method for further details.
◆ set_stiction_tolerance()
| void set_stiction_tolerance | ( | double | v_stiction = 0.001 | ) |
Sets the stiction tolerance v_stiction for the Stribeck model, where v_stiction must be specified in m/s (meters per second.) v_stiction defaults to a value of 1 millimeter per second.
In selecting a value for v_stiction, you must ask yourself the question, "When two objects are ostensibly in stiction, how much slip am I willing
to allow?" There are two opposing design issues in picking a value for vₛ. On the one hand, small values of vₛ make the problem numerically stiff during stiction, potentially increasing the integration cost. On the other hand, it should be picked to be appropriate for the scale of the problem. For example, a car simulation could allow a "large" value for vₛ of 1 cm/s (1×10⁻² m/s), but reasonable stiction for grasping a 10 cm box might require limiting residual slip to 1×10⁻³ m/s or less. Ultimately, picking the largest viable value will allow your simulation to run faster and more robustly. Note that v_stiction is the slip velocity that we'd have when we are at edge of the friction cone. For cases when the friction force is well within the friction cone the slip velocity will always be smaller than this value. See also Stribeck Approximation of Coulomb Friction.
- Exceptions
-
std::exception if v_stictionis non-positive.
◆ SetActuationInArray()
| void SetActuationInArray | ( | ModelInstanceIndex | model_instance, |
| const Eigen::Ref< const VectorX< T >> & | u_instance, | ||
| EigenPtr< VectorX< T >> | u | ||
| ) | const |
Given the actuation values u_instance for all actuators in model_instance, this method sets the actuation vector u for the entire model to which this actuator belongs to.
This method throws an exception if the size of u_instance is not equal to the number of degrees of freedom of all of the actuated joints in model_instance.
- Parameters
-
[in] u_instance Actuation values for the actuators. It must be of size equal to the number of degrees of freedom of all of the actuated joints in model_instance.[out] u The vector containing the actuation values for the entire model.
◆ SetDefaultState()
|
override |
Sets the state so that generalized positions and velocities are zero.
- Exceptions
-
std::exception if called pre-finalize. See Finalize().
◆ SetFreeBodyPose() [1/2]
| void SetFreeBodyPose | ( | systems::Context< T > * | context, |
| const Body< T > & | body, | ||
| const math::RigidTransform< T > & | X_WB | ||
| ) | const |
Sets context to store the pose X_WB of a given body B in the world frame W.
- Note
- In general setting the pose and/or velocity of a body in the model would involve a complex inverse kinematics problem. This method allows us to simplify this process when we know the body is free in space.
- Exceptions
-
std::exception if bodyis not a free body in the model.std::exception if called pre-finalize.
◆ SetFreeBodyPose() [2/2]
| void SetFreeBodyPose | ( | const systems::Context< T > & | context, |
| systems::State< T > * | state, | ||
| const Body< T > & | body, | ||
| const math::RigidTransform< T > & | X_WB | ||
| ) | const |
Sets state to store the pose X_WB of a given body B in the world frame W, for a given context of this model.
- Note
- In general setting the pose and/or velocity of a body in the model would involve a complex inverse kinematics problem. This method allows us to simplify this process when we know the body is free in space.
- Exceptions
-
std::exception if bodyis not a free body in the model.std::exception if called pre-finalize.
- Precondition
statecomes from this MultibodyPlant.
◆ SetFreeBodyPoseInAnchoredFrame()
| void SetFreeBodyPoseInAnchoredFrame | ( | systems::Context< T > * | context, |
| const Frame< T > & | frame_F, | ||
| const Body< T > & | body, | ||
| const math::RigidTransform< T > & | X_FB | ||
| ) | const |
Updates context to store the pose X_FB of a given body B in a frame F.
Frame F must be anchored, meaning that it is either directly welded to the world frame W or, more generally, that there is a kinematic path between frame F and the world frame W that only includes weld joints.
- Exceptions
-
std::logic_error if called pre-finalize. std::logic_error if frame F is not anchored to the world.
◆ SetFreeBodyPoseInWorldFrame()
| void SetFreeBodyPoseInWorldFrame | ( | systems::Context< T > * | context, |
| const Body< T > & | body, | ||
| const math::RigidTransform< T > & | X_WB | ||
| ) | const |
Sets context to store the pose X_WB of a given body B in the world frame W.
- Parameters
-
[in] context The context to store the pose X_WBofbody_B.[in] body_B The body B corresponding to the pose X_WBto be stored incontext.
- Return values
-
X_WB The pose of body frame B in the world frame W.
- Note
- In general setting the pose and/or velocity of a body in the model would involve a complex inverse kinematics problem. This method allows us to simplify this process when we know the body is free in space.
- Exceptions
-
std::exception if bodyis not a free body in the model.std::logic_error if called pre-finalize.
◆ SetFreeBodyRandomPositionDistribution()
| void SetFreeBodyRandomPositionDistribution | ( | const Body< T > & | body, |
| const Vector3< symbolic::Expression > & | position | ||
| ) |
Sets the distribution used by SetRandomState() to populate the x-y-z position component of the floating-base state.
- Exceptions
-
std::exception if bodyis not a free body in the model.std::exception if called pre-finalize.
◆ SetFreeBodyRandomRotationDistribution()
| void SetFreeBodyRandomRotationDistribution | ( | const Body< T > & | body, |
| const Eigen::Quaternion< symbolic::Expression > & | rotation | ||
| ) |
Sets the distribution used by SetRandomState() to populate the rotation component of the floating-base state.
- Exceptions
-
std::exception if bodyis not a free body in the model.std::exception if called pre-finalize.
◆ SetFreeBodyRandomRotationDistributionToUniform()
| void SetFreeBodyRandomRotationDistributionToUniform | ( | const Body< T > & | body | ) |
Sets the distribution used by SetRandomState() to populate the rotation component of the floating-base state using uniformly random rotations.
- Exceptions
-
std::exception if bodyis not a free body in the model.std::exception if called pre-finalize.
◆ SetFreeBodySpatialVelocity() [1/2]
| void SetFreeBodySpatialVelocity | ( | systems::Context< T > * | context, |
| const Body< T > & | body, | ||
| const SpatialVelocity< T > & | V_WB | ||
| ) | const |
Sets context to store the spatial velocity V_WB of a given body B in the world frame W.
- Note
- In general setting the pose and/or velocity of a body in the model would involve a complex inverse kinematics problem. This method allows us to simplify this process when we know the body is free in space.
- Exceptions
-
std::exception if bodyis not a free body in the model.std::exception if called pre-finalize.
◆ SetFreeBodySpatialVelocity() [2/2]
| void SetFreeBodySpatialVelocity | ( | const systems::Context< T > & | context, |
| systems::State< T > * | state, | ||
| const Body< T > & | body, | ||
| const SpatialVelocity< T > & | V_WB | ||
| ) | const |
Sets state to store the spatial velocity V_WB of a given body B in the world frame W, for a given context of this model.
- Note
- In general setting the pose and/or velocity of a body in the model would involve a complex inverse kinematics problem. This method allows us to simplify this process when we know the body is free in space.
- Exceptions
-
std::exception if bodyis not a free body in the model.std::exception if called pre-finalize.
- Precondition
statecomes from this MultibodyPlant.
◆ SetPositions() [1/3]
| void SetPositions | ( | systems::Context< T > * | context, |
| const VectorX< T > & | q | ||
| ) | const |
Sets all generalized positions from the given vector.
- Exceptions
-
std::exception if the contextis nullptr, if the context does not correspond to the context for a multibody model, or if the length ofqis not equal tonum_positions().
◆ SetPositions() [2/3]
| void SetPositions | ( | systems::Context< T > * | context, |
| ModelInstanceIndex | model_instance, | ||
| const VectorX< T > & | q_instance | ||
| ) | const |
Sets the positions for a particular model instance from the given vector.
- Exceptions
-
std::exception if the contextis nullptr, if the context does not correspond to the context for a multibody model, if the model instance index is invalid, or if the length ofq_instanceis not equal tonum_positions(model_instance).
◆ SetPositions() [3/3]
| void SetPositions | ( | const systems::Context< T > & | context, |
| systems::State< T > * | state, | ||
| ModelInstanceIndex | model_instance, | ||
| const VectorX< T > & | q_instance | ||
| ) | const |
Sets the positions for a particular model instance from the given vector.
- Exceptions
-
std::exception if the stateis nullptr, if the context does not correspond to the context for a multibody model, if the model instance index is invalid, or if the length ofq_instanceis not equal tonum_positions(model_instance).
- Precondition
statecomes from this MultibodyPlant.
◆ SetPositionsAndVelocities() [1/2]
| void SetPositionsAndVelocities | ( | systems::Context< T > * | context, |
| const VectorX< T > & | q_v | ||
| ) | const |
Sets all generalized positions and velocities from the given vector [q; v].
- Exceptions
-
std::exception if the contextis nullptr, if the context does not correspond to the context for a multibody model, or if the length ofq_vis not equal tonum_positions() + num_velocities().
◆ SetPositionsAndVelocities() [2/2]
| void SetPositionsAndVelocities | ( | systems::Context< T > * | context, |
| ModelInstanceIndex | model_instance, | ||
| const VectorX< T > & | q_v | ||
| ) | const |
Sets generalized positions and velocities from the given vector [q; v] for the specified model instance.
- Exceptions
-
std::exception if the contextis nullptr, if the context does not correspond to the context for a multibody model, if the model instance index is invalid, or if the length ofq_vis not equal tonum_positions(model_instance) + num_velocities(model_instance).
◆ SetPositionsInArray()
| void SetPositionsInArray | ( | ModelInstanceIndex | model_instance, |
| const Eigen::Ref< const VectorX< T >> & | q_instance, | ||
| EigenPtr< VectorX< T >> | q | ||
| ) | const |
Sets the vector of generalized positions for model_instance in q using q_instance, leaving all other elements in the array untouched.
This method throws an exception if q is not of size MultibodyPlant::num_positions() or q_instance is not of size MultibodyPlant::num_positions(model_instance).
◆ SetRandomState()
|
override |
Assigns random values to all elements of the state, by drawing samples independently for each joint/floating-base (coming soon: and then solving a mathematical program to "project" these samples onto the registered system constraints).
- See also
- Stochastic Systems
◆ SetVelocities() [1/3]
| void SetVelocities | ( | systems::Context< T > * | context, |
| const VectorX< T > & | v | ||
| ) | const |
Sets all generalized velocities from the given vector.
- Exceptions
-
std::exception if the contextis nullptr, if the context does not correspond to the context for a multibody model, or if the length ofvis not equal tonum_velocities().
◆ SetVelocities() [2/3]
| void SetVelocities | ( | const systems::Context< T > & | context, |
| systems::State< T > * | state, | ||
| ModelInstanceIndex | model_instance, | ||
| const VectorX< T > & | v_instance | ||
| ) | const |
Sets the generalized velocities for a particular model instance from the given vector.
- Exceptions
-
std::exception if the contextis nullptr, if the context does not correspond to the context for a multibody model, if the model instance index is invalid, or if the length ofv_instanceis not equal tonum_velocities(model_instance).
- Precondition
statecomes from this MultibodyPlant.
◆ SetVelocities() [3/3]
| void SetVelocities | ( | systems::Context< T > * | context, |
| ModelInstanceIndex | model_instance, | ||
| const VectorX< T > & | v_instance | ||
| ) | const |
Sets the generalized velocities for a particular model instance from the given vector.
- Exceptions
-
std::exception if the contextis nullptr, if the context does not correspond to the context for a multibody model, if the model instance index is invalid, or if the length ofv_instanceis not equal tonum_velocities(model_instance).
◆ SetVelocitiesInArray()
| void SetVelocitiesInArray | ( | ModelInstanceIndex | model_instance, |
| const Eigen::Ref< const VectorX< T >> & | v_instance, | ||
| EigenPtr< VectorX< T >> | v | ||
| ) | const |
Sets the vector of generalized velocities for model_instance in v using v_instance, leaving all other elements in the array untouched.
This method throws an exception if v is not of size MultibodyPlant::num_velocities() or v_instance is not of size MultibodyPlant::num_positions(model_instance).
◆ time_step()
| double time_step | ( | ) | const |
The time step (or period) used to model this plant as a discrete system with periodic updates.
Returns 0 (zero) if the plant is modeled as a continuous system. This property of the plant is specified at construction and therefore this query can be performed either pre- or post- finalize, see Finalize().
◆ WeldFrames()
| const WeldJoint< T > & WeldFrames | ( | const Frame< T > & | A, |
| const Frame< T > & | B, | ||
| const math::RigidTransform< double > & | X_AB = math::RigidTransform<double>::Identity() |
||
| ) |
Welds frames A and B with relative pose X_AB.
That is, the pose of frame B in frame A is fixed, with value X_AB. The call to this method creates and adds a new WeldJoint to the model. The new WeldJoint is named as: A.name() + "_welds_to_" + B.name().
- Returns
- a constant reference to the WeldJoint welding frames A and B.
◆ world_body()
| const RigidBody<T>& world_body | ( | ) | const |
Returns a constant reference to the world body.
◆ world_frame()
| const BodyFrame<T>& world_frame | ( | ) | const |
Returns a constant reference to the world frame.
Friends And Related Function Documentation
◆ MultibodyPlant
|
friend |
◆ MultibodyPlantTester
|
friend |
The documentation for this class was generated from the following files:
- drake/multibody/plant/multibody_plant.h
- drake/multibody/plant/multibody_plant.cc
