Drake
PositionKinematicsCache< T > Class Template Reference

This class is one of the cache entries in MultibodyTreeContext. More...

#include <drake/multibody/multibody_tree/position_kinematics_cache.h>

## Public Member Functions

PositionKinematicsCache (const MultibodyTreeTopology &topology)
Constructs a position kinematics cache entry for the given MultibodyTreeTopology. More...

const Isometry3< T > & get_X_WB (BodyNodeIndex body_node_index) const
Returns a constant reference to the pose X_WB of the body B (associated with node body_node_index) as measured and expressed in the world frame W. More...

Isometry3< T > & get_mutable_X_WB (BodyNodeIndex body_node_index)
See documentation on the const version get_X_WB() for details. More...

const Isometry3< T > & get_X_PB (BodyNodeIndex body_node_id) const
Returns a const reference to the pose X_PB of the body frame B as measured and expressed in its parent body frame P. More...

Isometry3< T > & get_mutable_X_PB (BodyNodeIndex body_node_id)
See documentation on the const version get_X_PB() for details. More...

const Isometry3< T > & get_X_FM (BodyNodeIndex body_node_index) const
For the mobilizer associated with the body node indexed by body_node_index, this method returns a const reference to the pose X_FM of the outboard frame M as measured and expressed in the inboard frame F. More...

Isometry3< T > & get_mutable_X_FM (BodyNodeIndex body_node_index)
See documentation on the const version get_X_FM() for details. More...

Implements CopyConstructible, CopyAssignable, MoveConstructible, MoveAssignable
PositionKinematicsCache (const PositionKinematicsCache &)=default

PositionKinematicsCacheoperator= (const PositionKinematicsCache &)=default

PositionKinematicsCache (PositionKinematicsCache &&)=default

PositionKinematicsCacheoperator= (PositionKinematicsCache &&)=default

## Detailed Description

### template<typename T> class drake::multibody::PositionKinematicsCache< T >

This class is one of the cache entries in MultibodyTreeContext.

It holds the kinematics results of computations that only depend on the generalized positions of the system. Kinematics results include:

• Body frame B poses X_WB measured and expressed in the world frame W.
• Pose X_FM of a mobilizer's outboard frame M measured and expressed in the inboard frame F.
• Mobilizer's matrices H_FM (with F and M defined above) that map the mobilizer's generalized velocities v to cross-joint spatial velocities V_FM = H_FM * v.
Template Parameters
 T The mathematical type of the context, which must be a valid Eigen scalar.

Instantiated templates for the following kinds of T's are provided:

• double
• AutoDiffXd

## Constructor & Destructor Documentation

 PositionKinematicsCache ( const PositionKinematicsCache< T > & )
default
 PositionKinematicsCache ( PositionKinematicsCache< T > && )
default
 PositionKinematicsCache ( const MultibodyTreeTopology & topology )
inlineexplicit

Constructs a position kinematics cache entry for the given MultibodyTreeTopology.

## Member Function Documentation

 Isometry3& get_mutable_X_FM ( BodyNodeIndex body_node_index )
inline

See documentation on the const version get_X_FM() for details.

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 Isometry3& get_mutable_X_PB ( BodyNodeIndex body_node_id )
inline

See documentation on the const version get_X_PB() for details.

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 Isometry3& get_mutable_X_WB ( BodyNodeIndex body_node_index )
inline

See documentation on the const version get_X_WB() for details.

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 const Isometry3& get_X_FM ( BodyNodeIndex body_node_index ) const
inline

For the mobilizer associated with the body node indexed by body_node_index, this method returns a const reference to the pose X_FM of the outboard frame M as measured and expressed in the inboard frame F.

Parameters
 [in] body_node_index The unique index for the computational BodyNode object associated with the mobilizer of interest.
Returns
A const reference to the pose X_FM of the outboard frame M as measured and expressed in the inboard frame F.

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 const Isometry3& get_X_PB ( BodyNodeIndex body_node_id ) const
inline

Returns a const reference to the pose X_PB of the body frame B as measured and expressed in its parent body frame P.

Parameters
 [in] body_node_id The unique identifier for the computational BodyNode object associated with body B.
Returns
X_PB a const reference to the pose of the the body frame B measured and expressed in the parent body frame P.

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 const Isometry3& get_X_WB ( BodyNodeIndex body_node_index ) const
inline

Returns a constant reference to the pose X_WB of the body B (associated with node body_node_index) as measured and expressed in the world frame W.

Parameters
 [in] body_node_index The unique index for the computational BodyNode object associated with body B.
Returns
X_WB the pose of the the body frame B measured and expressed in the world frame W.

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 PositionKinematicsCache& operator= ( const PositionKinematicsCache< T > & )
default
 PositionKinematicsCache& operator= ( PositionKinematicsCache< T > && )
default

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