Drake
PlanarJoint< T > Class Template Referencefinal

Detailed Description

template<typename T>
class drake::multibody::PlanarJoint< T >

This joint models a planar joint allowing two bodies to translate and rotate relative to one another in a plane with three degrees of freedom.

That is, given a frame F attached to the parent body P and a frame M attached to the child body B (see the Joint class's documentation), this joint allows frame M to translate within the x-y plane of frame F and to rotate about the z-axis, with M's z-axis Mz and F's z-axis Fz coincident at all times. The translations along the x- and y-axes of F, the rotation about the z-axis and their rates specify the state of the joint. Zero (x, y, θ) corresponds to frames F and M being coincident and aligned. Translation (x, y) is defined to be positive in the direction of the respective axes and the rotation θ is defined to be positive according to the right-hand-rule with the thumb aligned in the direction of frame F's z-axis.

Template Parameters
TThe scalar type, which must be one of the default scalars.

#include <drake/multibody/tree/planar_joint.h>

Public Types

template<typename Scalar >
using Context = systems::Context< Scalar >
 

Public Member Functions

 PlanarJoint (const std::string &name, const Frame< T > &frame_on_parent, const Frame< T > &frame_on_child, Vector3< double > damping)
 Constructor to create a planar joint between two bodies so that frame F attached to the parent body P and frame M attached to the child body B translate and rotate as described in the class's documentation. More...
 
const std::string & type_name () const final
 Returns a string identifying the type of this joint, such as "revolute" or "prismatic". More...
 
Vector3< double > damping () const
 Returns this joint's damping constant in N⋅s/m for the translational degrees and N⋅m⋅s for the rotational degree. More...
 
Vector2< double > get_default_translation () const
 Gets the default position for this joint. More...
 
void set_default_translation (const Vector2< double > &p_FoMo_F)
 Sets the default position of this joint. More...
 
double get_default_rotation () const
 Gets the default angle for this joint. More...
 
void set_default_rotation (double theta)
 Sets the default angle of this joint. More...
 
void set_default_pose (const Vector2< double > &p_FoMo_F, double theta)
 Sets the default position and angle of this joint. More...
 
void set_random_pose_distribution (const Vector2< symbolic::Expression > &p_FoMo_F, const symbolic::Expression &theta)
 Sets the random distribution that the position and angle of this joint will be randomly sampled from. More...
 
Does not allow copy, move, or assignment
 PlanarJoint (const PlanarJoint &)=delete
 
PlanarJointoperator= (const PlanarJoint &)=delete
 
 PlanarJoint (PlanarJoint &&)=delete
 
PlanarJointoperator= (PlanarJoint &&)=delete
 
Context-dependent value access
Vector2< T > get_translation (const Context< T > &context) const
 Gets the position of this joint from context. More...
 
const PlanarJoint< T > & set_translation (Context< T > *context, const Vector2< T > &p_FoMo_F) const
 Sets the context so that the position of this joint equals p_FoMo_F. More...
 
const T & get_rotation (const systems::Context< T > &context) const
 Gets the angle θ of this joint from context. More...
 
const PlanarJoint< T > & set_rotation (systems::Context< T > *context, const T &theta) const
 Sets the context so that the angle θ of this joint equals theta. More...
 
const PlanarJoint< T > & set_pose (systems::Context< T > *context, const Vector2< T > &p_FoMo_F, const T &theta) const
 Sets the context so that the position of this joint equals p_FoMo_F and its angle equals theta. More...
 
Vector2< T > get_translational_velocity (const systems::Context< T > &context) const
 Gets the translational velocity v_FoMo_F, in meters per second, of this joint's Mo measured and expressed in frame F from context. More...
 
const PlanarJoint< T > & set_translational_velocity (systems::Context< T > *context, const Vector2< T > &v_FoMo_F) const
 Sets the translational velocity, in meters per second, of this this joint's Mo measured and expressed in frame F to v_FoMo_F. More...
 
const T & get_angular_velocity (const systems::Context< T > &context) const
 Gets the rate of change, in radians per second, of this joint's angle θ from context. More...
 
const PlanarJoint< T > & set_angular_velocity (systems::Context< T > *context, const T &theta_dot) const
 Sets the rate of change, in radians per second, of this joint's angle θ (see class documentation) to theta_dot. More...
 
- Public Member Functions inherited from Joint< T >
 Joint (const std::string &name, const Frame< T > &frame_on_parent, const Frame< T > &frame_on_child, const VectorX< double > &pos_lower_limits, const VectorX< double > &pos_upper_limits, const VectorX< double > &vel_lower_limits, const VectorX< double > &vel_upper_limits, const VectorX< double > &acc_lower_limits, const VectorX< double > &acc_upper_limits)
 Creates a joint between two Frame objects which imposes a given kinematic relation between frame F attached on the parent body P and frame M attached on the child body B. More...
 
virtual ~Joint ()
 
const std::string & name () const
 Returns the name of this joint. More...
 
const Body< T > & parent_body () const
 Returns a const reference to the parent body P. More...
 
const Body< T > & child_body () const
 Returns a const reference to the child body B. More...
 
const Frame< T > & frame_on_parent () const
 Returns a const reference to the frame F attached on the parent body P. More...
 
const Frame< T > & frame_on_child () const
 Returns a const reference to the frame M attached on the child body B. More...
 
int velocity_start () const
 Returns the index to the first generalized velocity for this joint within the vector v of generalized velocities for the full multibody system. More...
 
int num_velocities () const
 Returns the number of generalized velocities describing this joint. More...
 
int position_start () const
 Returns the index to the first generalized position for this joint within the vector q of generalized positions for the full multibody system. More...
 
int num_positions () const
 Returns the number of generalized positions describing this joint. More...
 
const T & GetOnePosition (const systems::Context< T > &context) const
 Returns the position coordinate for joints with a single degree of freedom. More...
 
const T & GetOneVelocity (const systems::Context< T > &context) const
 Returns the velocity coordinate for joints with a single degree of freedom. More...
 
void AddInOneForce (const systems::Context< T > &context, int joint_dof, const T &joint_tau, MultibodyForces< T > *forces) const
 Adds into forces a force along the one of the joint's degrees of freedom indicated by index joint_dof. More...
 
void AddInDamping (const systems::Context< T > &context, MultibodyForces< T > *forces) const
 Adds into forces the force due to damping within this joint. More...
 
void Lock (systems::Context< T > *context) const
 Lock the joint. More...
 
void Unlock (systems::Context< T > *context) const
 Unlock the joint. More...
 
bool is_locked (const systems::Context< T > &context) const
 
 Joint (const Joint &)=delete
 
Jointoperator= (const Joint &)=delete
 
 Joint (Joint &&)=delete
 
Jointoperator= (Joint &&)=delete
 
const VectorX< double > & position_lower_limits () const
 
const VectorX< double > & position_upper_limits () const
 Returns the position upper limits. More...
 
const VectorX< double > & velocity_lower_limits () const
 Returns the velocity lower limits. More...
 
const VectorX< double > & velocity_upper_limits () const
 Returns the velocity upper limits. More...
 
const VectorX< double > & acceleration_lower_limits () const
 Returns the acceleration lower limits. More...
 
const VectorX< double > & acceleration_upper_limits () const
 Returns the acceleration upper limits. More...
 
const VectorX< double > & default_positions () const
 Returns the default positions. More...
 
void set_position_limits (const VectorX< double > &lower_limits, const VectorX< double > &upper_limits)
 Sets the position limits to lower_limits and upper_limits. More...
 
void set_velocity_limits (const VectorX< double > &lower_limits, const VectorX< double > &upper_limits)
 Sets the velocity limits to lower_limits and upper_limits. More...
 
void set_acceleration_limits (const VectorX< double > &lower_limits, const VectorX< double > &upper_limits)
 Sets the acceleration limits to lower_limits and upper_limits. More...
 
void set_default_positions (const VectorX< double > &default_positions)
 Sets the default positions to default_positions. More...
 
- Public Member Functions inherited from MultibodyElement< Joint, T, JointIndex >
virtual ~MultibodyElement ()
 
JointIndex index () const
 Returns this element's unique index. More...
 
ModelInstanceIndex model_instance () const
 Returns the ModelInstanceIndex of the model instance to which this element belongs. More...
 
const MultibodyPlantDeferred & GetParentPlant () const
 Returns the MultibodyPlant that owns this MultibodyElement. More...
 
void DeclareParameters (internal::MultibodyTreeSystem< T > *tree_system)
 Declares MultibodyTreeSystem Parameters at MultibodyTreeSystem::Finalize() time. More...
 
 MultibodyElement (const MultibodyElement &)=delete
 
 MultibodyElement (MultibodyElement &&)=delete
 
MultibodyElementoperator= (const MultibodyElement &)=delete
 
MultibodyElementoperator= (MultibodyElement &&)=delete
 

Static Public Attributes

static constexpr char kTypeName [] = "planar"
 The name for this Joint type. More...
 

Friends

template<typename >
class PlanarJoint
 

Additional Inherited Members

- Protected Member Functions inherited from Joint< T >
virtual const T & DoGetOnePosition (const systems::Context< T > &) const
 Implementation to the NVI GetOnePosition() that must only be implemented by those joint subclasses that have a single degree of freedom. More...
 
virtual const T & DoGetOneVelocity (const systems::Context< T > &) const
 Implementation to the NVI GetOneVelocity() that must only be implemented by those joint subclasses that have a single degree of freedom. More...
 
void DoSetTopology (const internal::MultibodyTreeTopology &) override
 Implementation of the NVI SetTopology(). More...
 
const JointImplementationget_implementation () const
 Returns a const reference to the internal implementation of this joint. More...
 
bool has_implementation () const
 Returns whether this joint owns a particular implementation. More...
 
void DoDeclareParameters (internal::MultibodyTreeSystem< T > *tree_system) override
 Implementation of the NVI DeclareParameters(). More...
 
- Protected Member Functions inherited from MultibodyElement< Joint, T, JointIndex >
 MultibodyElement ()
 Default constructor made protected so that sub-classes can still declare their default constructors if they need to. More...
 
 MultibodyElement (ModelInstanceIndex model_instance)
 Constructor which allows specifying a model instance. More...
 
const internal::MultibodyTree< T > & get_parent_tree () const
 Returns a constant reference to the parent MultibodyTree that owns this element. More...
 
const internal::MultibodyTreeSystem< T > & GetParentTreeSystem () const
 Returns a constant reference to the parent MultibodyTreeSystem that owns the parent MultibodyTree that owns this element. More...
 
void SetTopology (const internal::MultibodyTreeTopology &tree)
 Gives MultibodyElement-derived objects the opportunity to retrieve their topology after MultibodyTree::Finalize() is invoked. More...
 
systems::NumericParameterIndex DeclareNumericParameter (internal::MultibodyTreeSystem< T > *tree_system, const systems::BasicVector< T > &model_vector)
 To be used by MultibodyElement-derived objects when declaring parameters in their implementation of DoDeclareParameters(). More...
 
systems::AbstractParameterIndex DeclareAbstractParameter (internal::MultibodyTreeSystem< T > *tree_system, const AbstractValue &model_value)
 To be used by MultibodyElement-derived objects when declaring parameters in their implementation of DoDeclareParameters(). More...
 

Member Typedef Documentation

◆ Context

using Context = systems::Context<Scalar>

Constructor & Destructor Documentation

◆ PlanarJoint() [1/3]

PlanarJoint ( const PlanarJoint< T > &  )
delete

◆ PlanarJoint() [2/3]

PlanarJoint ( PlanarJoint< T > &&  )
delete

◆ PlanarJoint() [3/3]

PlanarJoint ( const std::string &  name,
const Frame< T > &  frame_on_parent,
const Frame< T > &  frame_on_child,
Vector3< double >  damping 
)

Constructor to create a planar joint between two bodies so that frame F attached to the parent body P and frame M attached to the child body B translate and rotate as described in the class's documentation.

This constructor signature creates a joint with no joint limits, i.e. the joint position, velocity and acceleration limits are the pair (-∞, ∞). These can be set using the Joint methods set_position_limits(), set_velocity_limits() and set_acceleration_limits(). The first three arguments to this constructor are those of the Joint class constructor. See the Joint class's documentation for details. The additional parameters are:

Parameters
[in]dampingViscous damping coefficient, in N⋅s/m for translation and N⋅m⋅s for rotation, used to model losses within the joint. See documentation of damping() for details on modelling of the damping force and torque.
Exceptions
std::exceptionif any element of damping is negative.

Member Function Documentation

◆ damping()

Vector3<double> damping ( ) const

Returns this joint's damping constant in N⋅s/m for the translational degrees and N⋅m⋅s for the rotational degree.

The damping force (in N) is modeled as fᵢ = -dampingᵢ⋅vᵢ, i = 1, 2 i.e. opposing motion, with vᵢ the translation rates along the i-th axis for this joint (see get_translational_velocity()) and fᵢ the force on child body B at Mo and expressed in F. That is, f_BMo_F = (f₁, f₂). The damping torque (in N⋅m) is modeled as τ = -damping₃⋅ω i.e. opposing motion, with ω the angular rate for this joint (see get_angular_velocity()) and τ the torque on child body B expressed in frame F as t_B_F = τ⋅Fz_F.

◆ get_angular_velocity()

const T& get_angular_velocity ( const systems::Context< T > &  context) const

Gets the rate of change, in radians per second, of this joint's angle θ from context.

See class documentation for the definition of this angle.

Parameters
[in]contextThe context of the model this joint belongs to.
Return values
theta_dotThe rate of change of this joint's angle θ as stored in the context.

◆ get_default_rotation()

double get_default_rotation ( ) const

Gets the default angle for this joint.

Return values
thetaThe default angle of this joint.

◆ get_default_translation()

Vector2<double> get_default_translation ( ) const

Gets the default position for this joint.

Return values
p_FoMo_FThe default position of this joint.

◆ get_rotation()

const T& get_rotation ( const systems::Context< T > &  context) const

Gets the angle θ of this joint from context.

Parameters
[in]contextThe context of the model this joint belongs to.
Return values
thetaThe angle of this joint stored in the context. See class documentation for details.

◆ get_translation()

Vector2<T> get_translation ( const Context< T > &  context) const

Gets the position of this joint from context.

Parameters
[in]contextThe context of the model this joint belongs to.
Return values
p_FoMo_FThe position of this joint stored in the context ordered as (x, y). See class documentation for details.

◆ get_translational_velocity()

Vector2<T> get_translational_velocity ( const systems::Context< T > &  context) const

Gets the translational velocity v_FoMo_F, in meters per second, of this joint's Mo measured and expressed in frame F from context.

Parameters
[in]contextThe context of the model this joint belongs to.
Return values
v_FoMo_FThe translational velocity of this joint as stored in the context.

◆ operator=() [1/2]

PlanarJoint& operator= ( PlanarJoint< T > &&  )
delete

◆ operator=() [2/2]

PlanarJoint& operator= ( const PlanarJoint< T > &  )
delete

◆ set_angular_velocity()

const PlanarJoint<T>& set_angular_velocity ( systems::Context< T > *  context,
const T &  theta_dot 
) const

Sets the rate of change, in radians per second, of this joint's angle θ (see class documentation) to theta_dot.

The new rate of change gets stored in context.

Parameters
[in]contextThe context of the model this joint belongs to.
[in]theta_dotThe desired rates of change of this joint's angle in radians per second.
Returns
a constant reference to this joint.

◆ set_default_pose()

void set_default_pose ( const Vector2< double > &  p_FoMo_F,
double  theta 
)

Sets the default position and angle of this joint.

Parameters
[in]p_FoMo_FThe desired default position of the joint
[in]thetaThe desired default angle of the joint

◆ set_default_rotation()

void set_default_rotation ( double  theta)

Sets the default angle of this joint.

Parameters
[in]thetaThe desired default angle of the joint

◆ set_default_translation()

void set_default_translation ( const Vector2< double > &  p_FoMo_F)

Sets the default position of this joint.

Parameters
[in]p_FoMo_FThe desired default position of the joint

◆ set_pose()

const PlanarJoint<T>& set_pose ( systems::Context< T > *  context,
const Vector2< T > &  p_FoMo_F,
const T &  theta 
) const

Sets the context so that the position of this joint equals p_FoMo_F and its angle equals theta.

Parameters
[in]contextThe context of the model this joint belongs to.
[in]p_FoMo_FThe desired position in meters to be stored in context ordered as (x, y). See class documentation for details.
[in]thetaThe desired angle in radians to be stored in context. See class documentation for details.
Returns
a constant reference to this joint.

◆ set_random_pose_distribution()

void set_random_pose_distribution ( const Vector2< symbolic::Expression > &  p_FoMo_F,
const symbolic::Expression theta 
)

Sets the random distribution that the position and angle of this joint will be randomly sampled from.

See class documentation for details on the definition of the position and angle.

◆ set_rotation()

const PlanarJoint<T>& set_rotation ( systems::Context< T > *  context,
const T &  theta 
) const

Sets the context so that the angle θ of this joint equals theta.

Parameters
[in]contextThe context of the model this joint belongs to.
[in]thetaThe desired angle in radians to be stored in context. See class documentation for details.
Returns
a constant reference to this joint.

◆ set_translation()

const PlanarJoint<T>& set_translation ( Context< T > *  context,
const Vector2< T > &  p_FoMo_F 
) const

Sets the context so that the position of this joint equals p_FoMo_F.

Parameters
[in]contextThe context of the model this joint belongs to.
[in]p_FoMo_FThe desired position in meters to be stored in context ordered as (x, y). See class documentation for details.
Returns
a constant reference to this joint.

◆ set_translational_velocity()

const PlanarJoint<T>& set_translational_velocity ( systems::Context< T > *  context,
const Vector2< T > &  v_FoMo_F 
) const

Sets the translational velocity, in meters per second, of this this joint's Mo measured and expressed in frame F to v_FoMo_F.

The new translational velocity gets stored in context.

Parameters
[in]contextThe context of the model this joint belongs to.
[in]v_FoMo_FThe desired translational velocity of this joint in meters per second.
Returns
a constant reference to this joint.

◆ type_name()

const std::string& type_name ( ) const
finalvirtual

Returns a string identifying the type of this joint, such as "revolute" or "prismatic".

Implements Joint< T >.

Friends And Related Function Documentation

◆ PlanarJoint

friend class PlanarJoint
friend

Member Data Documentation

◆ kTypeName

constexpr char kTypeName[] = "planar"
static

The name for this Joint type.


The documentation for this class was generated from the following file: