Drake

MultibodyPlant is a Drake system framework representation (see systems::System) for the model of a physical system consisting of a collection of interconnected bodies. More...
#include <drake/multibody/multibody_tree/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)  
Scalarconverting copy constructor. See System Scalar Conversion. 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_positions () const 
Returns the size of the generalized position vector q for this model. More...  
int  num_velocities () const 
Returns the size of the generalized velocity vector v for this model. More...  
int  num_multibody_states () const 
Returns the size of the multibody system state vector x = [q; v] for this model. More...  
int  num_actuated_dofs () const 
Returns the total number of actuated degrees of freedom. More...  
geometry::SourceId  RegisterAsSourceForSceneGraph (geometry::SceneGraph< T > *scene_graph) 
Registers this plant to serve as a source for an instance of SceneGraph. More...  
void  RegisterVisualGeometry (const Body< T > &body, const Isometry3< double > &X_BG, const geometry::Shape &shape, geometry::SceneGraph< T > *scene_graph) 
Registers geometry in a SceneGraph with a given geometry::Shape to be used for visualization of a given body . 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 Isometry3< double > &X_BG, const geometry::Shape &shape, const CoulombFriction< double > &coulomb_friction, geometry::SceneGraph< T > *scene_graph) 
Registers geometry in a SceneGraph with a given geometry::Shape to be used for the contact modeling of a given body . 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 RigidBody< T > * > &bodies) const 
For each of the provided bodies , collects up all geometries that have been registered to that body. 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...  
bool  geometry_source_is_registered () const 
Returns true if this MultibodyPlant was registered with a SceneGraph. 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::InputPortDescriptor< T > &  get_actuation_input_port () const 
Returns a constant reference to the input port for external actuation. More...  
const systems::OutputPort< T > &  get_continuous_state_output_port () const 
Returns a constant reference to the output port for the full continuous state of the model. More...  
const RigidBody< T > &  world_body () const 
Returns a constant reference to the world body. More...  
const MultibodyTree< T > &  model () const 
Returns a constant reference to the underlying MultibodyTree model for this plant. More...  
bool  is_finalized () const 
Returns true if this MultibodyPlant was finalized with a call to Finalize(). More...  
void  Finalize (geometry::SceneGraph< T > *scene_graph=nullptr) 
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...  
bool  is_discrete () const 
Returns true if this plant is modeled as a discrete system. More...  
double  time_step () const 
The time step (or period) used to model this plant as a discrete system with periodic updates. More...  
void  SetDefaultState (const systems::Context< T > &context, systems::State< T > *state) const override 
Sets the state in context so that generalized positions and velocities are zero. More...  
Does not allow copy, move, or assignment  
MultibodyPlant (const MultibodyPlant &)=delete  
MultibodyPlant &  operator= (const MultibodyPlant &)=delete 
MultibodyPlant (MultibodyPlant &&)=delete  
MultibodyPlant &  operator= (MultibodyPlant &&)=delete 
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, const SpatialInertia< double > &M_BBo_B) 
Creates a rigid body model with the provided name and spatial inertia. More...  
template<template< typename > class JointType, typename... Args>  
const JointType< T > &  AddJoint (const std::string &name, const Body< T > &parent, const optional< Isometry3< double >> &X_PF, const Body< T > &child, const optional< Isometry3< 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 model. More...  
template<template< typename Scalar > class ForceElementType, typename... Args>  
std::enable_if< std::is_same< ForceElementType< T >, UniformGravityFieldElement< T > >::value, const ForceElementType< T > & >::type  AddForceElement (Args &&...args) 
const JointActuator< T > &  AddJointActuator (const std::string &name, const Joint< T > &joint) 
Creates and adds a JointActuator model for an actuator acting on a given joint . 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  HasJointNamed (const std::string &name) const 
bool  HasJointActuatorNamed (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. 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(). This implies that these queries can be performed while new multibody elements are being added to the model.  
const Body< T > &  GetBodyByName (const std::string &name) const 
Returns a constant reference to the rigid body that is uniquely identified by the string name in this model. More...  
const Joint< T > &  GetJointByName (const std::string &name) const 
Returns a constant reference to the joint that is uniquely identified by the string name in this model. More...  
template<template< typename > class JointType>  
const JointType< T > &  GetJointByName (const std::string &name) const 
A templated version of GetJointByName() to return a constant reference of the specified type JointType in place of the base Joint class. More...  
const JointActuator< T > &  GetJointActuatorByName (const std::string &name) const 
Returns a constant reference to the actuator that is uniquely identified by the string name in this model. 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::InputPortDescriptor< 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...  
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 nonpenetration 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 usersupplied "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 interpenetration 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 interpenetrations, 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 interpenetrations being reduced by the same factor of 0.5. In summary, users should choose the largest penetration allowance that results in interpenetration 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 nonzero 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 errorcontrolled 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.  
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 nonpenetration among bodies. More...  
double  get_contact_penalty_method_time_scale () const 
Returns a timescale 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. See tangent_force 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 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 >  DoMakeContext () const final 
Derived class implementations should allocate a suitable defaultconstructed Context, with defaultconstructed subcontexts for diagrams. More...  
void  DoValidateAllocatedContext (const ContextBase &context_base) const final 
Any derived class that imposes restrictions on the structure or content of an acceptable Context should enforce those restrictions by overriding this 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< SystemOutput< T > >  AllocateOutput (const Context< T > &) const final 
Returns a container that can hold the values of all of this System's output ports. 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=default  
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...  
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 InputPortDescriptor< T > &descriptor) const 
Given a port descriptor, allocates the vector storage. More...  
std::unique_ptr< AbstractValue >  AllocateInputAbstract (const InputPortDescriptor< T > &descriptor) const 
Given a port descriptor, allocates the abstract storage. 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 directfeedthrough 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 directfeedthrough from the given input_port to the given output_port , and false otherwise. 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 T &  EvalConservativePower (const Context< T > &context) const 
Returns a reference to the cached value of the conservative power. More...  
const T &  EvalNonConservativePower (const Context< T > &context) const 
Returns a reference to the cached value of the nonconservative power. More...  
template<template< typename > class Vec = BasicVector>  
const Vec< T > *  EvalVectorInput (const Context< T > &context, int port_index) const 
Returns the value of the vectorvalued 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 vectorvalued input port with the given port_index as an Eigen vector. More...  
int  get_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...  
void  CalcTimeDerivatives (const Context< T > &context, ContinuousState< T > *derivatives) const 
Calculates the time derivatives xcdot of the continuous state xc . 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  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  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 discrete_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 StepTo() 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 current stored in the configuration provided in context . More...  
T  CalcKineticEnergy (const Context< T > &context) const 
Calculates and returns the kinetic energy currently present in the motion provided in the given Context. More...  
T  CalcConservativePower (const Context< T > &context) const 
Calculates and returns the rate at which mechanical energy is being converted from potential energy to kinetic energy by this system in the given Context. More...  
T  CalcNonConservativePower (const Context< T > &context) const 
Calculates and returns the rate at which mechanical energy is being generated (positive) or dissipated (negative) other than by conversion between potential and kinetic energy (in 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 InputPortDescriptor< T > &  get_input_port (int port_index) const 
Returns the typed input port at index port_index . More...  
const OutputPort< T > &  get_output_port (int port_index) const 
Returns the typed output port at index port_index . More...  
int  get_num_constraints () const 
Returns the number of constraints specified for the system. More...  
const SystemConstraint< T > &  get_constraint (SystemConstraintIndex constraint_index) const 
Returns the constraint at index constraint_index . More...  
bool  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...  
std::string  GetGraphvizString () 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 dynamicsized 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 humanreadable name for this system, for use in messages and logging. More...  
std::string  GetSystemPathname () const final 
Generates and returns a humanreadable full path name of this subsystem, for use in messages and logging. More...  
std::string  GetSystemType () const final 
Returns the mostderived type of this concrete System object as a humanreadable 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  get_num_input_ports () const 
Returns the number of input ports currently allocated in this System. More...  
int  get_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  get_num_total_inputs () const 
Returns the total dimension of all of the vectorvalued input ports (as if they were muxed). More...  
int  get_num_total_outputs () const 
Returns the total dimension of all of the vectorvalued 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 
Return a 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 abstractvalued 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 leastrestrictive 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, 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...  
DependencyTicket  input_port_ticket (InputPortIndex index) 
Returns a ticket indicating dependence on the input port indicated by index . More...  
DependencyTicket  output_port_ticket (OutputPortIndex index) 
Returns a ticket indicating dependence on the output port indicated by index . More...  
DependencyTicket  cache_entry_ticket (CacheIndex index) 
Returns a ticket indicating dependence on the cache entry indicated by index . More...  
Friends  
template<typename U >  
class  MultibodyPlant 
class  MultibodyPlantTester 
Additional Inherited Members  
Static Public Member Functions inherited from System< T >  
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 dynamicsized 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  all_sources_ticket () 
Returns a ticket indicating dependence on every possible independent source value, including time, state, input ports, parameters, and the accuracy setting (but not cache entries). More...  
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 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  xcdot_ticket () 
Returns a ticket for the cache entry that holds time derivatives of the continuous variables. More...  
static DependencyTicket  xdhat_ticket () 
Returns a ticket for the cache entry that holds the discrete state update for the numerical discrete variables in the state. More...  
static DependencyTicket  configuration_ticket () 
Returns a ticket indicating dependence on all the configuration variables for this System. More...  
static DependencyTicket  velocity_ticket () 
Returns a ticket indicating dependence on all of the velocity variables for this System. More...  
static DependencyTicket  kinematics_ticket () 
Returns a ticket indicating dependence on all of the configuration and velocity state variables of this System. 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...  
Protected Member Functions inherited from LeafSystem< T >  
LeafSystem ()  
Default constructor that declares no inputs, outputs, state, parameters, events, nor scalartype conversion support (AutoDiff, etc.). More...  
LeafSystem (SystemScalarConverter converter)  
Constructor that declares no inputs, outputs, state, parameters, or events, but allows subclasses to declare scalartype conversion support (AutoDiff, etc.). 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...  
BasicVector< T > *  DoAllocateInputVector (const InputPortDescriptor< T > &descriptor) const override 
Allocates a vector that is suitable as an input value for descriptor . More...  
AbstractValue *  DoAllocateInputAbstract (const InputPortDescriptor< T > &descriptor) const override 
Allocates an AbstractValue suitable as an input value for descriptor . More...  
void  GetGraphvizFragment (std::stringstream *dot) const override 
Emits a graphviz fragment for this System. More...  
void  GetGraphvizInputPortToken (const InputPortDescriptor< T > &port, 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, 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<typename EventType >  
void  DeclarePeriodicEvent (double period_sec, double offset_sec) 
Declares that this System has a simple, fixedperiod event specified with no custom callback function, and its attribute field contains an Event<T>::PeriodicAttribute constructed from the specified period_sec and offset_sec . More...  
template<typename EventType >  
void  DeclarePeriodicEvent (double period_sec, double offset_sec, const EventType &event) 
Declares that this System has a simple, fixedperiod event specified by event . More...  
void  DeclarePeriodicDiscreteUpdate (double period_sec, double offset_sec=0) 
Declares a periodic discrete update event with period = period_sec and offset = offset_sec . More...  
void  DeclarePeriodicUnrestrictedUpdate (double period_sec, double offset_sec=0) 
Declares a periodic unrestricted update event with period = period_sec and offset = offset_sec . More...  
void  DeclarePeriodicPublish (double period_sec, double offset_sec=0) 
Declares a periodic publish event with period = period_sec and offset = offset_sec . More...  
template<typename EventType >  
void  DeclarePerStepEvent (const EventType &event) 
Declares a perstep event using event , which is deep copied (the copy is maintained by this ). More...  
template<typename EventType >  
void  DeclareInitializationEvent (const EventType &event) 
Declares an initialization event by deep copying event and storing it internally. More...  
void  DeclareContinuousState (int num_state_variables) 
Declares that this System should reserve continuous state with num_state_variables state variables, which have no secondorder 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...  
void  DeclareContinuousState (std::unique_ptr< 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 the a vector Cloned from model_vector . More...  
void  DeclareDiscreteState (int num_state_variables) 
Declares that this System should reserve discrete state with num_state_variables state variables. More...  
int  DeclareAbstractState (std::unique_ptr< AbstractValue > abstract_state) 
Declares an abstract state. More...  
template<class MySystem >  
SystemConstraintIndex  DeclareEqualityConstraint (void(MySystem::*calc)(const Context< T > &, VectorX< T > *) const, int count, const 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 (typename SystemConstraint< T >::CalcCallback calc, int count, const 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, int count, const 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  DeclareInequalityConstraint (typename SystemConstraint< T >::CalcCallback calc, int count, const 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...  
virtual void  DoPublish (const Context< T > &context, const std::vector< const PublishEvent< T > * > &events) const 
Derivedclass event handler 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 
Derivedclass event handler 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 
Derivedclass event handler for all simultaneous unrestricted update events. More...  
const InputPortDescriptor< T > &  DeclareVectorInputPort (const BasicVector< T > &model_vector, optional< RandomDistribution > random_type=nullopt) 
Declares a vectorvalued input port using the given model_vector . More...  
const InputPortDescriptor< T > &  DeclareAbstractInputPort (const AbstractValue &model_value) 
Declares an abstractvalued input port using the given model_value . More...  
template<class MySystem >  
std::unique_ptr< WitnessFunction< T > >  DeclareWitnessFunction (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 > >  DeclareWitnessFunction (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 > >  DeclareWitnessFunction (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 > >  DeclareWitnessFunction (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 > >  DeclareWitnessFunction (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 > >  DeclareWitnessFunction (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 > >  DeclareWitnessFunction (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...  
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()}) 
Declares a vectorvalued 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 (void(MySystem::*calc)(const Context< T > &, BasicVectorSubtype *) const, std::set< DependencyTicket > prerequisites_of_calc={all_sources_ticket()}) 
Declares a vectorvalued output port by specifying only a calculator function that is a class member function (method) with signature: 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()}) 
(Advanced) Declares a vectorvalued 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 (const OutputType &model_value, void(MySystem::*calc)(const Context< T > &, OutputType *) const, std::set< DependencyTicket > prerequisites_of_calc={all_sources_ticket()}) 
Declares an abstractvalued 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 (void(MySystem::*calc)(const Context< T > &, OutputType *) const, std::set< DependencyTicket > prerequisites_of_calc={all_sources_ticket()}) 
Declares an abstractvalued 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 (OutputType(MySystem::*make)() const, void(MySystem::*calc)(const Context< T > &, OutputType *) const, std::set< DependencyTicket > prerequisites_of_calc={all_sources_ticket()}) 
Declares an abstractvalued output port by specifying member functions to use both for the allocator and calculator. 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()}) 
(Advanced) Declares an abstractvalued output port using the given allocator and calculator functions provided in their most generic forms. 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 alreadycreated constraint to the list of constraints for this System. More...  
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, possibly supporting scalartype conversion support (AutoDiff, etc.) using converter . More...  
const InputPortDescriptor< T > &  DeclareInputPort (PortDataType type, int size, optional< RandomDistribution > random_type=nullopt) 
Adds a port with the specified type and size to the input topology. More...  
const InputPortDescriptor< T > &  DeclareAbstractInputPort () 
Adds an abstractvalued port to the input topology. 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 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 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 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 at which mechanical energy is being generated (positive) or dissipated (negative) other than by conversion between potential and kinetic energy (in the given Context). 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 alreadyconstructed input port to this System. More...  
void  AddOutputPort (std::unique_ptr< OutputPortBase > port) 
(Internal use only) Adds an alreadyconstructed output port to this System. More...  
const internal::SystemParentServiceInterface *  get_parent_service () const 
(Internal use only) 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 declaredvector 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 we don't like the port index. 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 std::unique_ptr< ContextBase >  MakeContext (const SystemBase &system) 
(Internal use only) Allows Diagram to use private MakeContext() to invoke the same method on its children. More...  
static void  ValidateAllocatedContext (const SystemBase &system, const ContextBase &context) 
(Internal use only) Allows Diagram to use its private ValidateAllocatedContext() to invoke the same method on its children. More...  
MultibodyPlant is a Drake system framework representation (see systems::System) for the model of a physical system consisting of a collection of interconnected bodies.
MultibodyPlant provides a userfacing API to:
The state of a multibody system x = [q; v]
is given by its generalized 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.
Clients of a MultibodyPlant can add multibody elements with the following methods:
All modeling elements must be added prefinalize.
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 prefinalize.
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:

delete 

delete 

explicit 
Default constructor creates a plant with a single "world" body.
Therefore, right after creation, num_bodies() returns one.
[in]  time_step  An optional parameter indicating whether this plant is modeled as a continuous system (time_step = 0 ) or as a discrete system with periodic updates of period time_step > 0 . Default: 0.0. 
std::exception  if time_step is negative. 

inline 
Scalarconverting copy constructor. See System Scalar Conversion.

inline 
Adds a new force element model of type ForceElementType
to this
model.
The arguments to this method args
are forwarded to ForceElementType
's constructor.
[in]  args  Zero or more parameters provided to the constructor of the new force element. It must be the case that JointType<T>(args) is a valid constructor. 
ForceElementType  The type of the ForceElement to add. This method can only be called once for elements of type UniformGravityFieldElement. That is, gravity can only be specified once. 
ForceElementType<T>
specialized on the scalar type T of this
MultibodyPlant. It will remain valid for the lifetime of this
MultibodyPlant.

inline 

inline 
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 inboardoutboard 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.
name  A string that uniquely identifies the new joint to be added to this model. A std::runtime_error is thrown if a joint named name already 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_PF is 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 pose X_PF equal to the identity pose, provide Isometry3<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_BM is 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 pose X_BM equal to the identity pose, provide Isometry3<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. 
JointType  The type of the Joint to add. 
JointType<T>
specialized on the scalar type T of this
MultibodyPlant. It will remain valid for the lifetime of this
MultibodyPlant.Example of usage:
if  this model already contains a joint with the given name . See HasJointNamed(), Joint::name(). 

inline 
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.
[in]  name  A string that uniquely identifies the new actuator to be added to this model. 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. 
this
plant. if  joint.num_dofs() > 1 since for now we only support actuators for single dof joints. 

inline 
Creates a rigid body model 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:
[in]  name  A string that uniquely identifies the new body to be added to this model. A std::runtime_error is thrown if a body named name already is part of the model. See HasBodyNamed(), Body::name(). 
[in]  M_BBo_B  The SpatialInertia of the new rigid body to be added to this model, computed about the body frame origin Bo and expressed in the body frame B. 
this
MultibodyPlant. geometry::GeometrySet CollectRegisteredGeometries  (  const std::vector< const RigidBody< 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.
std::exception  if called prefinalize. 

inline 
Returns the friction coefficients provided during geometry registration for the given geometry id
.
We call these the "default" coefficients but note that we mean usersupplied pergeometry default, not something more global.
std::exception  if id does not correspond to a geometry in this model registered for contact modeling. 
void Finalize  (  geometry::SceneGraph< T > *  scene_graph = nullptr  ) 
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 preprocessing 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 uptodate 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.
std::logic_error  if


inline 
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 postfinalize, see Finalize().
const systems::InputPortDescriptor< T > & get_actuation_input_port  (  )  const 
Returns a constant reference to the input port for external actuation.
This input port is a vector valued port, which can be set with JointActuator::set_actuation_vector().
this
plant. if  called before Finalize() or if the model does not contain any actuators. See AddJointActuator() and num_actuators(). 

inline 
Returns a timescale estimate tc
based on the requested penetration allowance δ set with set_penetration_allowance().
For the penalty method in use to enforce nonpenetration, 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
.
const systems::OutputPort< T > & get_continuous_state_output_port  (  )  const 
Returns a constant reference to the output port for the full continuous state of the model.
std::exception  if called prefinalize. 
const OutputPort< T > & get_geometry_poses_output_port  (  )  const 
Returns the output port of frames' poses to communicate with a SceneGraph.
std::exception  if this system was not registered with a SceneGraph. 
std::exception  if called prefinalize. See Finalize(). 
const systems::InputPortDescriptor< 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.
std::exception  if this system was not registered with a SceneGraph. 
std::exception  if called prefinalize. See Finalize(). 

inline 
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 postfinalize, 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. Postfinalize calls will always return the same value.

inline 
Returns a constant reference to the rigid body that is uniquely identified by the string name
in this
model.
std::logic_error  if there is no body with the requested name. 
this
model with a given specified name.

inline 
If the body with body_index
has geometry registered with it, it returns the geometry::FrameId associated with it.
Otherwise, it returns nullopt.
if  called prefinalize. 

inline 
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.
if  no geometry has been registered with the body indicated by body_index . 
if  called prefinalize. 
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.
this
plant, either pre or postfinalize, see Finalize(). Postfinalize calls will always return the same value.

inline 
Returns a constant reference to the actuator that is uniquely identified by the string name
in this
model.
std::logic_error  if there is no actuator with the requested name. 
this
model with a given specified name.

inline 
Returns a constant reference to the joint that is uniquely identified by the string name
in this
model.
std::logic_error  if there is no joint with the requested name. 
this
model with a given specified name.

inline 
A templated version of GetJointByName() to return a constant reference of the specified type JointType
in place of the base Joint class.
See GetJointByName() for details.
JointType  The specific type of the Joint to be retrieved. It must be a subclass of Joint. 
std::logic_error  if the named joint is not of type JointType or if there is no Joint with that name. 
this
model with a given specified name. 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.
this
plant, either pre or postfinalize, see Finalize(). Postfinalize calls will always return the same value.

inline 
true
if a body named name
was added to the model.

inline 
true
if an actuator named name
was added to the model.

inline 
true
if a joint named name
was added to the model.

inline 
Returns true
if this plant is modeled as a discrete system.
This property of the plant is specified at construction and therefore this query can be performed either pre or post finalize, see Finalize().

inline 
Returns true
if this MultibodyPlant was finalized with a call to Finalize().

inline 
Returns a constant reference to the underlying MultibodyTree model for this
plant.
if  called prefinalize. See Finalize(). 

inline 
Returns the total number of actuated degrees of freedom.
That is, the vector of actuation values u has this size. See AddJointActuator().

inline 
Returns the number of joint actuators in the model.

inline 
Returns the number of bodies in the model, including the "world" body, which is always part of the model.

inline 
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 postfinalize, see Finalize(). Postfinalize calls will always return the same value.

inline 
Returns the number of joints in the model.

inline 
Returns the size of the multibody system state vector x = [q; v]
for this
model.
This will equal the number of generalized positions (see num_positions()) plus the number of generalized velocities (see num_velocities()). Notice however that the state of a MultibodyPlant, stored in its Context, can actually contain other variables such as integrated power and discrete states.

inline 
Returns the size of the generalized position vector q
for this
model.

inline 
Returns the size of the generalized velocity vector v
for this
model.

inline 
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 postfinalize, see Finalize(). Postfinalize calls will always return the same value.

delete 

delete 
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.
scene_graph  A valid non nullptr to the SceneGraph instance for which this plant will sever as a source, see SceneGraph documentation for further details. 
this
plant in scene_graph
. It can also later on be retrieved with get_source_id(). if  called postfinalize. 
if  scene_graph is the nullptr. 
if  called more than once. 
geometry::GeometryId RegisterCollisionGeometry  (  const Body< T > &  body, 
const Isometry3< double > &  X_BG,  
const geometry::Shape &  shape,  
const CoulombFriction< double > &  coulomb_friction,  
geometry::SceneGraph< T > *  scene_graph  
) 
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.
[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 shape for the given body . 
[out]  scene_graph  A valid, nonnull pointer to a SceneGraph on which geometry will get registered. 
std::exception  if scene_graph is the nullptr. 
std::exception  if called postfinalize. 
std::exception  if scene_graph does not correspond to the same instance with which RegisterAsSourceForSceneGraph() was called. 
void RegisterVisualGeometry  (  const Body< T > &  body, 
const Isometry3< double > &  X_BG,  
const geometry::Shape &  shape,  
geometry::SceneGraph< T > *  scene_graph  
) 
Registers geometry in a SceneGraph with a given geometry::Shape to be used for visualization of a given body
.
[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. 
[out]  scene_graph  A valid non nullptr to a SceneGraph on which geometry will get registered. 
if  scene_graph is the nullptr. 
if  called postfinalize. 
if  scene_graph does not correspond to the same instance with which RegisterAsSourceForSceneGraph() was called. 
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 nonpenetration among bodies.
Refer to the section Contact by penalty method for further details.

inline 
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.
std::exception  if v_stiction is nonpositive. 

inlineoverride 
Sets the state in context
so that generalized positions and velocities are zero.
if  called prefinalize. See Finalize(). 

inline 
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().

inline 
Returns a constant reference to the world body.

friend 

friend 