Represents a kinematic chain or tree of bodies (links and joints and modules). More...

#include <kinematics.hpp>

Public Member Functions
	Kinematics ()
	Creates a kinematics object with no bodies and an identity base frame. More...

virtual	~Kinematics () noexcept
	Destructor cleans up kinematics object, including all managed bodies. More...

void	setBaseFrame (const Eigen::Matrix4f &base_frame)
	Set the transform from a world coordinate system to the input of the root kinematic body in this kinematics object. Defaults to an identity 4x4 matrix. More...

Eigen::Matrix4f	getBaseFrame () const
	Returns the transform from the world coordinate system to the root kinematic body, as set by the setBaseFrame function. More...

size_t	getFrameCount (HebiFrameType frame_type) const
	Return the number of frames in the forward kinematics. More...

size_t	getDoFCount () const
	Returns the number of settable degrees of freedom in the kinematic tree. (This is equal to the number of actuators added). More...

bool	addBody (std::shared_ptr< KinematicBody > new_body)
	Add a body to a parent body connected to a kinematic tree object. More...

void	getForwardKinematics (HebiFrameType, const Eigen::VectorXd &positions, Matrix4fVector &frames) const
	Generates the forward kinematics for the given kinematic tree. More...

void	getFK (HebiFrameType, const Eigen::VectorXd &positions, Matrix4fVector &frames) const
	Generates the forward kinematics for the given kinematic tree. More...

void	getEndEffector (HebiFrameType, const Eigen::VectorXd &positions, Eigen::Matrix4f &transform) const
	Generates the forward kinematics to the end effector (leaf node) frame(s). More...

void	solveInverseKinematics (const Eigen::Vector3f &target_xyz, const Eigen::VectorXd &positions, Eigen::VectorXd &result) const
	Solves for an inverse kinematics solution that moves the end effector to a given point. More...

void	solveIK (const Eigen::Vector3f &target_xyz, const Eigen::VectorXd &initial_positions, Eigen::VectorXd &result) const
	Solves for an inverse kinematics solution that moves the end effector to a given point. More...

void	getJacobians (HebiFrameType, const Eigen::VectorXd &positions, MatrixXfVector &jacobians) const
	Generates the Jacobian for each frame in the given kinematic tree. More...

void	getJ (HebiFrameType, const Eigen::VectorXd &positions, MatrixXfVector &jacobians) const
	Generates the Jacobian for each frame in the given kinematic tree. More...

void	getJacobianEndEffector (HebiFrameType, const Eigen::VectorXd &positions, Eigen::MatrixXf &jacobian) const
	Generates the Jacobian for the end effector (leaf node) frames(s). More...

void	getJEndEffector (HebiFrameType, const Eigen::VectorXd &positions, Eigen::MatrixXf &jacobian) const
	Generates the Jacobian for the end effector (leaf node) frames(s). More...

Detailed Description

Represents a kinematic chain or tree of bodies (links and joints and modules).

(Currently, only kinematic chains are fully supported).

Constructor & Destructor Documentation

hebi::kinematics::Kinematics::Kinematics ( )

Creates a kinematics object with no bodies and an identity base frame.

hebi::kinematics::Kinematics::~Kinematics ( )

virtualnoexcept

Destructor cleans up kinematics object, including all managed bodies.

Member Function Documentation

void hebi::kinematics::Kinematics::setBaseFrame ( const Eigen::Matrix4f & base_frame )

Set the transform from a world coordinate system to the input of the root kinematic body in this kinematics object. Defaults to an identity 4x4 matrix.

The world coordinate system is used for all position, vector, and transformation matrix parameters in the member functions.

Parameters

base_frame The 4x4 homogeneous transform from the world frame to the root kinematic body frame.

Eigen::Matrix4f hebi::kinematics::Kinematics::getBaseFrame ( ) const

Returns the transform from the world coordinate system to the root kinematic body, as set by the setBaseFrame function.

size_t hebi::kinematics::Kinematics::getFrameCount ( HebiFrameType frame_type ) const

Return the number of frames in the forward kinematics.

Note that this depends on the type of frame requested – for center of mass frames, there is one per added body; for output frames, there is one per output per body.

Parameters

frame_type Which type of frame to consider – see HebiFrameType enum.

size_t hebi::kinematics::Kinematics::getDoFCount ( ) const

Returns the number of settable degrees of freedom in the kinematic tree. (This is equal to the number of actuators added).

bool hebi::kinematics::Kinematics::addBody ( std::shared_ptr< KinematicBody > new_body )

Add a body to a parent body connected to a kinematic tree object.

After the addition, the kinematics object manages the resources of the added body.

Parameters

new_body The kinematic body which is added to the tree.

Returns: true if successful, false if unable to add the body.

void hebi::kinematics::Kinematics::getForwardKinematics	(	HebiFrameType	frame_type,
		const Eigen::VectorXd &	positions,
		Matrix4fVector &	frames
	)		const

Generates the forward kinematics for the given kinematic tree.

See getFK for details.

void hebi::kinematics::Kinematics::getFK	(	HebiFrameType	frame_type,
		const Eigen::VectorXd &	positions,
		Matrix4fVector &	frames
	)		const

Generates the forward kinematics for the given kinematic tree.

The order of the returned frames is in a depth-first tree. As an example, assume a body A has one output, to which body B is connected to. Body B has two outputs; actuator C is attached to the first output and actuator E is attached to the second output. Body D is attached to the only output of actuator C:

(BASE) A - B(1) - C - D (2) | E

For center of mass frames, the returned frames would be A-B-C-D-E.

For output frames, the returned frames would be A-B(1)-C-D-B(2)-E.

Parameters

frame_type	Which type of frame to consider – see HebiFrameType enum.
positions	A vector of joint positions/angles (in SI units of meters or radians) equal in length to the number of DoFs of the kinematic tree.
frames	An array of 4x4 transforms; this is resized as necessary in the function and filled in with the 4x4 homogeneous transform of each frame. Note that the number of frames depends on the frame type.

void hebi::kinematics::Kinematics::getEndEffector	(	HebiFrameType	frame_type,
		const Eigen::VectorXd &	positions,
		Eigen::Matrix4f &	transform
	)		const

Generates the forward kinematics to the end effector (leaf node) frame(s).

Note – for center of mass frames, this is one per leaf node; for output frames, this is one per output per leaf node, in depth first order.

This overload is for kinematic chains that only have a single leaf node frame.

(Currently, kinematic trees are not fully supported – only kinematic chains – and so there are not other overloads for this function).

Parameters

frame_type	Which type of frame to consider – see HebiFrameType enum.
positions	A vector of joint positions/angles (in SI units of meters or radians) equal in length to the number of DoFs of the kinematic tree.
transform	A 4x4 transform that is resized as necessary in the function and filled in with the homogeneous transform to the end effector frame.

void hebi::kinematics::Kinematics::solveInverseKinematics	(	const Eigen::Vector3f &	target_xyz,
		const Eigen::VectorXd &	positions,
		Eigen::VectorXd &	result
	)		const

Solves for an inverse kinematics solution that moves the end effector to a given point.

See solveIK for details.

void hebi::kinematics::Kinematics::solveIK	(	const Eigen::Vector3f &	target_xyz,
		const Eigen::VectorXd &	initial_positions,
		Eigen::VectorXd &	result
	)		const

Solves for an inverse kinematics solution that moves the end effector to a given point.

WARNING: this function interface is not yet stable; future revisions will likely change the method for adding objectives and returning failure/status information about the solution.

Parameters

target_xyz	A length 3 vector of the desired end effector location.
initial_positions	The seed positions/angles (in SI units of meters or radians) to start the IK search from; equal in length to the number of DoFs of the kinematic tree.
result	A vector equal in length to the number of DoFs of the kinematic tree; this will be filled in with the IK solution (in SI units of meters or radians), and resized as necessary.

void hebi::kinematics::Kinematics::getJacobians	(	HebiFrameType	frame_type,
		const Eigen::VectorXd &	positions,
		MatrixXfVector &	jacobians
	)		const

Generates the Jacobian for each frame in the given kinematic tree.

See getJ for details.

void hebi::kinematics::Kinematics::getJ	(	HebiFrameType	frame_type,
		const Eigen::VectorXd &	positions,
		MatrixXfVector &	jacobians
	)		const

Generates the Jacobian for each frame in the given kinematic tree.

Parameters

frame_type	Which type of frame to consider – see HebiFrameType enum.
positions	A vector of joint positions/angles (in SI units of meters or radians) equal in length to the number of DoFs of the kinematic tree.
jacobians	A vector (length equal to the number of frames) of matrices; each matrix is a (6 x number of dofs) jacobian matrix for the corresponding frame of reference on the robot. This vector is resized as necessary inside this function.

void hebi::kinematics::Kinematics::getJacobianEndEffector	(	HebiFrameType	frame_type,
		const Eigen::VectorXd &	positions,
		Eigen::MatrixXf &	jacobian
	)		const

Generates the Jacobian for the end effector (leaf node) frames(s).

See getJEndEffector for details.

void hebi::kinematics::Kinematics::getJEndEffector	(	HebiFrameType	frame_type,
		const Eigen::VectorXd &	positions,
		Eigen::MatrixXf &	jacobian
	)		const

Generates the Jacobian for the end effector (leaf node) frames(s).

Note – for center of mass frames, this is one per leaf node; for output frames, this is one per output per leaf node, in depth first order.

This overload is for kinematic chains that only have a single leaf node frame.

(Currently, kinematic trees are not fully supported – only kinematic chains – and so there are not other overloads for this function).

Parameters

frame_type	Which type of frame to consider – see HebiFrameType enum.
positions	A vector of joint positions/angles (in SI units of meters or radians) equal in length to the number of DoFs of the kinematic tree.
jacobian	A (6 x number of dofs) jacobian matrix for the corresponding end effector frame of reference on the robot. This vector is resized as necessary inside this function.

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

src/kinematics.hpp
src/kinematics.cpp

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation