Interface to define general-purpose constraints. More...

#include <Constraint.h>

Inheritance diagram for Constraint:

Public Member Functions
virtual void	bind (const Model &model)=0
	Any local memory that has a dimension of N, where N is the length of QDot, is resized in this function. More...

virtual void	calcConstraintJacobian (Model &model, const double time, const Math::VectorNd &Q, const Math::VectorNd &QDot, Math::MatrixNd &GSysOutput, ConstraintCache &cache, bool updateKinematics=false)=0
	In this function the matrix $G_{i}$ of this contraint is inserted into the system constraint Jacobian (GSysOutput). The submatrix $G_{i}$ begins at rowInSystem, has sizeOfConstraint number of rows, and fills the full number of columns in G. More...

virtual void	calcGamma (Model &model, const double time, const Math::VectorNd &Q, const Math::VectorNd &QDot, const Math::MatrixNd &GSys, Math::VectorNd &gammaSysOutput, ConstraintCache &cache, bool updateKinematics=false)=0
	In this function the vector $\gamma_{i}$ of this constraint is inserted into the right-hand-side vector $\gamma_{SYS}$ of the system. The vector $\gamma_{i}$ begins at rowInSystem, and has sizeOfConstraint rows. More...

virtual void	calcPositionError (Model &model, const double time, const Math::VectorNd &Q, Math::VectorNd &errSysOutput, ConstraintCache &cache, bool updateKinematics=false)=0
	In this function the sub vector $\phi_{p,i}(q,t)$ of this constraint is inserted into the position error vector of the system. If the constraint is velocity-level constraint or higher (noted in the boolean member variable positionConstraint) this should be set to zero. The vector $\phi_{p,i}(\dot{q},t)$ begins at rowInSystem, and has sizeOfConstraint rows. More...

virtual void	calcVelocityError (Model &model, const double time, const Math::VectorNd &Q, const Math::VectorNd &QDot, const Math::MatrixNd &GSys, Math::VectorNd &derrSysOutput, ConstraintCache &cache, bool updateKinematics=false)=0
	In this function the sub vector $\phi_{v,i}(q, \dot{q},t)$ of this constraint is inserted into the position error vector of the system. If the constraint is an acceleration-level constraint (noted in the boolean member variable velocityConstraint) this sub vector should be zero. The vector $\phi_{v,i}(q, \dot{q},t)$ begins at rowInSystem, and has sizeOfConstraint rows. More...

virtual void	calcConstraintForces (Model &model, const double time, const Math::VectorNd &Q, const Math::VectorNd &QDot, const Math::MatrixNd &GSys, const Math::VectorNd &LagrangeMultipliersSys, std::vector< unsigned int > &constraintBodiesOutput, std::vector< Math::SpatialTransform > &constraintBodyFramesOutput, std::vector< Math::SpatialVector > &constraintForcesOutput, ConstraintCache &cache, bool resolveAllInRootFrame=false, bool updateKinematics=false)=0
	This function resolves the generalized forces this constraint applies to the system into the wrenches that are applied to the bodies that are involved in the constraint. More...

virtual	~Constraint ()

	Constraint ()

	Constraint (const char *nameOfConstraint, unsigned int typeOfConstraint, unsigned int sizeOfConstraint, unsigned int userDefinedIdNumber)

void	addToConstraintSet (const unsigned int rowIndex)
	This function is called by the functions in ConstraintSet that add a Constraint to the system. DO NOT TOUCH THIS. More...

unsigned int	getUserDefinedId ()

void	setUserDefinedId (unsigned int userDefinedId)

void	getConstraintJacobian (const Math::MatrixNd &GSys, Math::MatrixNd &GConstraint)

void	getGamma (const Math::VectorNd &gammaSys, Math::VectorNd &gammaConstraint)

void	getPositionError (const Math::VectorNd &errSys, Math::VectorNd &errConstraint)

void	getVelocityError (const Math::VectorNd &derrSys, Math::VectorNd &derrConstraint)

void	getBaumgarteStabilizationParameters (Math::Vector2d &bgParamsUpd)

void	getBaumgarteStabilizationForces (const Math::VectorNd &errPos, const Math::VectorNd &errVel, Math::VectorNd &baumgarteForces)

void	addInBaumgarteStabilizationForces (const Math::VectorNd &errPosSys, const Math::VectorNd &errVelSys, Math::VectorNd &gammaSysOutput)

unsigned int	getConstraintType ()

unsigned int	getConstraintSize ()

unsigned int	getConstraintIndex ()

void	setBaumgarteTimeConstant (double tStab)
	Calculates and sets the Baumgarte stabilization coefficients as a function of tStab, the approximate time-constant of stabilization. More...

void	setEnableBaumgarteStabilization (bool flagEnableBaumgarteStabilization)

bool	isBaumgarteStabilizationEnabled ()

void	enableConstraintErrorFromPositionLevel (unsigned int constraintSubIndex)
	: Will set the vectors positionConstraint and velocityConstraint to be consistent with a constraint that is described from the position-level up. More...

void	enableConstraintErrorFromVelocityLevel (unsigned int constraintSubIndex)
	: Will set the vectors positionConstraint and velocityConstraint to be consistent with a constraint that is described from the velocity-level up: position errors will be set to zero while velocity errors will be computed. More...

void	enableConstraintErrorFromAccelerationLevel (unsigned int constraintSubIndex)
	: Will set the vectors positionConstraint and velocityConstraint to be consistent with a constraint that is described from the acceleration-level: both position and velocity errors will be set to zero. More...

void	enableConstraintErrorFromPositionLevel ()
	: Will set the all elements in positionConstraint and velocityConstraint to be consistent with a constraint that is described from the position-level up. More...

void	enableConstraintErrorFromVelocityLevel ()
	: Will set the all elements in positionConstraint and velocityConstraint to be consistent with a constraint that is described from the velocity-level up. More...

void	enableConstraintErrorFromAccelerationLevel ()
	: Will set the all elements in positionConstraint and velocityConstraint to be consistent with a constraint that is described from the acceleration-level up. More...

bool	getPositionLevelError (unsigned int constraintSubIndex)
	Returns the boolean value that determines whether or not position-level errors are computed for this sub-index into this constraint. More...

bool	getVelocityLevelError (unsigned int constraintSubIndex)
	Returns the boolean value that determines whether or not velocity-level errors are computed for this sub-index into this constraint. More...

const char *	getName ()

const std::vector< unsigned int > &	getBodyIds ()

const std::vector< Math::SpatialTransform > &	getBodyFrames ()

Protected Attributes
std::string	name
	A user defined name which is unique to this constraint set. More...

unsigned int	id
	A user defined id which is unique to this constraint set. More...

unsigned int	typeOfConstraint
	The type of this constraint. More...

unsigned int	sizeOfConstraint
	The number of rows that this constraint adds to G. More...

unsigned int	rowInSystem
	The first row in G that corresponds to this constraint. More...

std::vector< unsigned int >	bodyIds
	The index of the predecessor body in the vector of bodies in Model. More...

std::vector< Math::SpatialTransform >	bodyFrames
	Transform from the frame of the predecessor body to the constraint frame. More...

Math::Vector2d	baumgarteParameters

bool	baumgarteEnabled
	A flag which enables or disables Baumgarte stabilization. More...

std::vector< bool >	positionConstraint

std::vector< bool >	velocityConstraint

Detailed Description

Interface to define general-purpose constraints.

The Constraint interface is a general-purpose interface that is rich enough to define time-varying constraints at the position-level $\phi_p(q,t)=0$ , the velocity-level $\phi_v(\dot{q},q,t)=0$ , or the acceleration-level $\phi_a(\ddot{q},\dot{q},q,t)=0$ . These constraints all end up being applied at the acceleration-level by taking successive derivatives until we are left with $\Phi(\ddot{q},\dot{q},q,t)=0$ . A new concrete Constraint class must provide implementations for the following methods:

bind
calcConstraintJacobian
calcGamma
calcPositionError
calcVelocityError
calcConstraintForces

Please see the doxygen for each of these functions in the Constraint interface for details. In addition, please have a look at Constraint_Contact (and ContactsTests.cc) and Constraint_Loop (and LoopConstraintsTests.cc) for working examples to guide your own implementation.

Please note that constraints are challenging to derive and implement even for multibody dynamics experts. If you are unfamiliar with the concept please refer to Featherstone's Robot Dynamics Algorithms text. If you are authoring a new constraint please read the section below on how to test your constraint.

Physical correctness ( and $\gamma$ ): Workless? Ensure that the constraint is workless: perform a forward simulation of a passive system that includes the new constraint oscillating under gravity. Compute the sum of kinetic and potential energy called system energy. System energy should be constant, but will exhibit small amounts of accumulating error due to integration error. If the tolerances on the integration are tightened these errors should also drop. This kind of analysis is usually done when the first implementation of the constraint is being developed. This kind of test is usually not included as a unit test because it requires an accurate numerical integrator (which introduces an external dependency). A faster version of this test is to evaluate the forward dynamics of a given set of states and then sum up the joint powers which should sum to zero in a conservative system.
Physical correctness ( and $\gamma$ ): Agrees with equivalent joint-coordinate model? Evaluate $\ddot{q}$ by calling ForwardDynamicsConstraintsDirect on your system. If possible construct a model that uses joint coordinates that is perfectly equivalent to the model that uses constraints and evaluate its forward dynamics using the same initial state. The matching indices of $\ddot{q}$ should be identical. Examples of tests like this can be seen in ConstraintCorrectnessTest in LoopConstraintsTests.cc.
Compare against static-equilibrum calculations ( ) Set-up a simple test model for which you can easily compute the correct values for the position error, velocity error, and constraint forces. This is most easily done by solving for the $\tau$ that will put the sytem in a state of static equilibrium. Then you can easily solve by hand for the forces the constraint should develop and compare those to the values returned by calcForce. Examples of tests like this can be seen in TestExtendedConstraintFunctionsContact in ContactsTests.cc and TestExtendedConstraintFunctionsLoop in LoopConstraintsTests.cc
Compare against known errors ( $\epsilon_{P}$ and $\epsilon_{V}$ ) The values returned for the position and velocity errors of the constraint are most easily evaluated by constructing a system in which the constraint is satisfied at the position and velocity level and then calling calcPositionError and calcVelocityError to ensure that the returned errors are zero. A follow up test is then to introduce a known error to the generalized positions and velocities and sure that the error returned by cal Tests like this can be found in TestExtendedConstraintFunctionsContact in ContactsTests.cc and TestExtendedConstraintFunctionsLoop in LoopConstraintsTests.cc.

Definition at line 139 of file Constraint.h.

Constructor & Destructor Documentation

◆ ~Constraint()

virtual ~Constraint ( )

inlinevirtual

Definition at line 366 of file Constraint.h.

◆ Constraint() [1/2]

Constraint ( )

◆ Constraint() [2/2]

Constraint	(	const char *	nameOfConstraint,
		unsigned int	typeOfConstraint,
		unsigned int	sizeOfConstraint,
		unsigned int	userDefinedIdNumber
	)

inline

Parameters

name	(optional) name of the constraint. Use only as a means to find a specific constraint.
typeOfConstraint	corresponds to the enums listed in ConstraintTypes. This parameter is used by a few methods that only work with specific types of constraints such as ForwardDynamicsContactsKokkevis.
sizeOfConstraint	the number of equations that define the constraint manifold. Equivalently this is the number of rows in this constraints Jacobian.
userDefinedIdNumber	an integer that the user can set to rapidly retrieve this constraint from the set.

Definition at line 386 of file Constraint.h.

Member Function Documentation

◆ addInBaumgarteStabilizationForces()

void addInBaumgarteStabilizationForces	(	const Math::VectorNd &	errPosSys,
		const Math::VectorNd &	errVelSys,
		Math::VectorNd &	gammaSysOutput
	)

inline

Parameters

errPosSys	: the position error vector of the system
errVelSys	: the velocity error vector of the system
gammaSysOutput	the gamma vector of the system

Definition at line 507 of file Constraint.h.

◆ addToConstraintSet()

void addToConstraintSet ( const unsigned int rowIndex )

inline

This function is called by the functions in ConstraintSet that add a Constraint to the system. DO NOT TOUCH THIS.

Parameters

rowIndex the first index of this constraint in the systems constraint Jacobian.

Definition at line 416 of file Constraint.h.

◆ bind()

virtual void bind ( const Model & model )

pure virtual

Any local memory that has a dimension of N, where N is the length of QDot, is resized in this function.

Parameters

model a reference to the multibody model. Use the model's fields of qdot_size to size local memory (if any) that depends on the model.

Implemented in ContactConstraint, and LoopConstraint.

◆ calcConstraintForces()

virtual void calcConstraintForces	(	Model &	model,
		const double	time,
		const Math::VectorNd &	Q,
		const Math::VectorNd &	QDot,
		const Math::MatrixNd &	GSys,
		const Math::VectorNd &	LagrangeMultipliersSys,
		std::vector< unsigned int > &	constraintBodiesOutput,
		std::vector< Math::SpatialTransform > &	constraintBodyFramesOutput,
		std::vector< Math::SpatialVector > &	constraintForcesOutput,
		ConstraintCache &	cache,
		bool	resolveAllInRootFrame = `false`,
		bool	updateKinematics = `false`
	)

pure virtual

This function resolves the generalized forces this constraint applies to the system into the wrenches that are applied to the bodies that are involved in the constraint.

Parameters

model	a reference to the multibody model.
time	the time which is included so that rheonomic constraints might be included (in the future).
Q	the vector of generalized positions.
QDot	the vector of generalized velocities.
GSys	a reference to the constraint Jacobian for the entire system. If is needed in this function do not re-evaluate it but instead extract it from the system : this constraint's sub-matrix begins at rowInSystem, has sizeOfConstraint rows, and the full number of columns of GSys.
LagrangeMultipliersSys	the vector of Lagrange multipliers for the entire system. The Lagrange multipliers for this constraint begin at rowInSystem and has sizeOfConstraint elements.
constraintBodiesOutput	contains the indices of the bodies that contain the local frames listed in constraintBodyFramesOutput. If resolveAllInRootFrame is true, all of these indicies should be set to 0: in this case all of the wrenches are resolved in the root frame.
constraintBodyFramesOutput	contains the local transformation from the origin of each body frame listed in constraintBodiesOutput to the frame in which the constraint wrench is applied. Note the $i^{th}$ frame is located on the $i^{th}$ body. If resolveAllInRootFrame is true, all of these frames have their origins resolved in the global frame and their orientation set to match that tof the global frame.
constraintForcesOutput	contains the wrenches that the constraint applies to the local frames listed in constraintBodyFramesOutput. Note the $i^{th}$ force is resolved in the $i^{th}$ frame.If resolveAllInRootFrame is true, this wrench should be rotated into the coordinates of the root frame.
cache	a ConstraintCache object which contains ample pre-allocated memory that can be used to reduce the memory footprint of each Constraint implementation.
resolveAllInRootFrame	When this parameter is - false: the wrenches are resolved into their local frames. - true: the wrenches are resolved into coordinates of the global frame
updateKinematics	setting this flag to true will cause all calls to kinematic dependent functions to be updated using the generalized coordinates passed into this function.

Implemented in ContactConstraint, and LoopConstraint.

◆ calcConstraintJacobian()

virtual void calcConstraintJacobian	(	Model &	model,
		const double	time,
		const Math::VectorNd &	Q,
		const Math::VectorNd &	QDot,
		Math::MatrixNd &	GSysOutput,
		ConstraintCache &	cache,
		bool	updateKinematics = `false`
	)

pure virtual

In this function the matrix $G_{i}$ of this contraint is inserted into the system constraint Jacobian $G$ (GSysOutput). The submatrix $G_{i}$ begins at rowInSystem, has sizeOfConstraint number of rows, and fills the full number of columns in G.

Parameters

model	a reference to the multibody model.
time	the time which is included so that rheonomic constraints might be included (in the future).
Q	the vector of generalized positions.
QDot	the vector of generalized velocities.
GSysOutput	a reference to the constraint Jacobian for the entire system. Insert the G sub-matrix for this constraint beginning and rowInSystem, with a length sizeOfConstraint rows, and a width of the full number of columns in GSysOutput.
cache	a ConstraintCache object which contains ample pre-allocated memory that can be used to reduce the memory footprint of each Constraint implementation.
updateKinematics	setting this flag to true will cause all calls to kinematic dependent functions to be updated using the generalized coordinates passed into this function.

Implemented in ContactConstraint, and LoopConstraint.

◆ calcGamma()

virtual void calcGamma	(	Model &	model,
		const double	time,
		const Math::VectorNd &	Q,
		const Math::VectorNd &	QDot,
		const Math::MatrixNd &	GSys,
		Math::VectorNd &	gammaSysOutput,
		ConstraintCache &	cache,
		bool	updateKinematics = `false`
	)

pure virtual

In this function the vector $\gamma_{i}$ of this constraint is inserted into the right-hand-side vector $\gamma_{SYS}$ of the system. The vector $\gamma_{i}$ begins at rowInSystem, and has sizeOfConstraint rows.

Parameters

model	a reference to the multibody model.
time	the time which is included so that rheonomic constraints might be included (in the future).
Q	the vector of generalized positions.
QDot	the vector of generalized velocities.
GSys	a reference to the constraint Jacobian for the entire system. If is needed in this function do not re-evaluate it but instead extract it from the system .
gammaSysOutput	the system's gamma vector. Insert the gamma sub-vector for this constraint beginning and rowInSystem and with a length of sizeOfConstraint rows.
cache	a ConstraintCache object which contains ample pre-allocated memory that can be used to reduce the memory footprint of each Constraint implementation.
updateKinematics	setting this flag to true will cause all calls to kinematic dependent functions to be updated using the generalized coordinates passed into this function.

Implemented in ContactConstraint, and LoopConstraint.

◆ calcPositionError()

virtual void calcPositionError	(	Model &	model,
		const double	time,
		const Math::VectorNd &	Q,
		Math::VectorNd &	errSysOutput,
		ConstraintCache &	cache,
		bool	updateKinematics = `false`
	)

pure virtual

In this function the sub vector $\phi_{p,i}(q,t)$ of this constraint is inserted into the position error vector of the system. If the constraint is velocity-level constraint or higher (noted in the boolean member variable positionConstraint) this should be set to zero. The vector $\phi_{p,i}(\dot{q},t)$ begins at rowInSystem, and has sizeOfConstraint rows.

Parameters

model	a reference to the multibody model
time	the time which is included so that rheonomic constraints might be included (in the future).
Q	the vector of generalized positions.
errSysOutput	the system's constraint position error vector. Insert the position error sub-vector for this constraint beginning and rowInSystem and with a length of sizeOfConstraint rows.
cache	a ConstraintCache object which contains ample pre-allocated memory that can be used to reduce the memory footprint of each Constraint implementation.
updateKinematics	setting this flag to true will cause all calls to kinematic dependent functions to be updated using the generalized coordinates passed into this function.

Implemented in ContactConstraint, and LoopConstraint.

◆ calcVelocityError()

virtual void calcVelocityError	(	Model &	model,
		const double	time,
		const Math::VectorNd &	Q,
		const Math::VectorNd &	QDot,
		const Math::MatrixNd &	GSys,
		Math::VectorNd &	derrSysOutput,
		ConstraintCache &	cache,
		bool	updateKinematics = `false`
	)

pure virtual

In this function the sub vector $\phi_{v,i}(q, \dot{q},t)$ of this constraint is inserted into the position error vector of the system. If the constraint is an acceleration-level constraint (noted in the boolean member variable velocityConstraint) this sub vector should be zero. The vector $\phi_{v,i}(q, \dot{q},t)$ begins at rowInSystem, and has sizeOfConstraint rows.

Parameters

model	a reference to the multibody model.
time	the time which is included so that rheonomic constraints might be included (in the future).
Q	the vector of generalized positions.
QDot	the vector of generalized velocities.
GSys	a reference to the constraint Jacobian for the entire system. If is needed in this function do not re-evaluate it but instead extract it from the system : this constraint's sub-matrix begins at rowInSystem, has sizeOfConstraint rows, and the full number of columns of GSys.
derrSysOutput	the system's constraint velocity error vector. Insert the velocity error sub-vector for this constraint beginning and rowInSystem and with a length of sizeOfConstraint rows.
cache	a ConstraintCache object which contains ample pre-allocated memory that can be used to reduce the memory footprint of each Constraint implementation.
updateKinematics	setting this flag to true will cause all calls to kinematic dependent functions to be updated using the generalized coordinates passed into this function.

Implemented in ContactConstraint, and LoopConstraint.

◆ enableConstraintErrorFromAccelerationLevel() [1/2]

void enableConstraintErrorFromAccelerationLevel ( )

inline

: Will set the all elements in positionConstraint and velocityConstraint to be consistent with a constraint that is described from the acceleration-level up.

Definition at line 653 of file Constraint.h.

◆ enableConstraintErrorFromAccelerationLevel() [2/2]

void enableConstraintErrorFromAccelerationLevel ( unsigned int constraintSubIndex )

inline

: Will set the vectors positionConstraint and velocityConstraint to be consistent with a constraint that is described from the acceleration-level: both position and velocity errors will be set to zero.

Parameters

constraintSubIndex the sub index into this contraint group.

Definition at line 615 of file Constraint.h.

◆ enableConstraintErrorFromPositionLevel() [1/2]

void enableConstraintErrorFromPositionLevel ( )

inline

: Will set the all elements in positionConstraint and velocityConstraint to be consistent with a constraint that is described from the position-level up.

Definition at line 627 of file Constraint.h.

◆ enableConstraintErrorFromPositionLevel() [2/2]

void enableConstraintErrorFromPositionLevel ( unsigned int constraintSubIndex )

inline

: Will set the vectors positionConstraint and velocityConstraint to be consistent with a constraint that is described from the position-level up.

Parameters

constraintSubIndex the sub index into this contraint group.

Definition at line 584 of file Constraint.h.

◆ enableConstraintErrorFromVelocityLevel() [1/2]

void enableConstraintErrorFromVelocityLevel ( )

inline

: Will set the all elements in positionConstraint and velocityConstraint to be consistent with a constraint that is described from the velocity-level up.

Definition at line 640 of file Constraint.h.

◆ enableConstraintErrorFromVelocityLevel() [2/2]

void enableConstraintErrorFromVelocityLevel ( unsigned int constraintSubIndex )

inline

: Will set the vectors positionConstraint and velocityConstraint to be consistent with a constraint that is described from the velocity-level up: position errors will be set to zero while velocity errors will be computed.

Parameters

constraintSubIndex the sub index into this contraint group.

Definition at line 599 of file Constraint.h.

◆ getBaumgarteStabilizationForces()

void getBaumgarteStabilizationForces	(	const Math::VectorNd &	errPos,
		const Math::VectorNd &	errVel,
		Math::VectorNd &	baumgarteForces
	)

inline

Parameters

errPos	: the position error vector of this constraint
errVel	: the velocity error vector of this constraint
baumgarteForces	the Baumgarte stabilization forces

Definition at line 493 of file Constraint.h.

◆ getBaumgarteStabilizationParameters()

void getBaumgarteStabilizationParameters ( Math::Vector2d & bgParamsUpd )

inline

Parameters

bgParamsUpd (output) the Baumgarte stabilization coefficients for this constraint. Note the velocity error coefficient is in the 0 index and the position error coefficient is in the 1st index.

Definition at line 484 of file Constraint.h.

◆ getBodyFrames()

const std::vector< Math::SpatialTransform > & getBodyFrames ( )

inline

Returns: a vector of local frames (which are located on the corresponding body in the vector of body Ids returned by getBodyIds) that are involved in this constraint.

Definition at line 703 of file Constraint.h.

◆ getBodyIds()

const std::vector< unsigned int > & getBodyIds ( )

inline

Returns: a vector of the bodyIds that are involved in this constraint

Definition at line 694 of file Constraint.h.

◆ getConstraintIndex()

unsigned int getConstraintIndex ( )

inline

Returns: the index of the first row in G in which this constraint's entries appear.

Definition at line 541 of file Constraint.h.

◆ getConstraintJacobian()

void getConstraintJacobian	(	const Math::MatrixNd &	GSys,
		Math::MatrixNd &	GConstraint
	)

inline

Parameters

GSys	: a reference to the system's constraint Jacobian
GConstraint	: a reference to this constraint's entry within the system constraint Jacobian

Definition at line 441 of file Constraint.h.

References MX_Xd_dynamic::block(), and MX_Xd_dynamic::cols().

◆ getConstraintSize()

unsigned int getConstraintSize ( )

inline

Returns: the number of constraint equations in this constraint

Definition at line 533 of file Constraint.h.

◆ getConstraintType()

unsigned int getConstraintType ( )

inline

Returns: the type of this constraint as defined in the struct ConstraintType

Definition at line 526 of file Constraint.h.

◆ getGamma()

void getGamma	(	const Math::VectorNd &	gammaSys,
		Math::VectorNd &	gammaConstraint
	)

inline

Parameters

gammaSys	a reference to the system's gamma vector
gammaConstraint	a reference to this constraint's entry within the system gamma vector

Definition at line 452 of file Constraint.h.

References MX_Xd_dynamic::block().

◆ getName()

const char * getName ( )

inline

Returns: the user defined name

Definition at line 687 of file Constraint.h.

◆ getPositionError()

void getPositionError	(	const Math::VectorNd &	errSys,
		Math::VectorNd &	errConstraint
	)

inline

Parameters

errSys	a reference to the system's constraint position error
errConstraint	a reference to this constraint's entry within the system constraint position error.

Definition at line 462 of file Constraint.h.

References MX_Xd_dynamic::block().

◆ getPositionLevelError()

bool getPositionLevelError ( unsigned int constraintSubIndex )

inline

Returns the boolean value that determines whether or not position-level errors are computed for this sub-index into this constraint.

Parameters

constraintSubIndex the sub index of interest in this constraint

Definition at line 668 of file Constraint.h.

◆ getUserDefinedId()

unsigned int getUserDefinedId ( )

inline

Returns: (optional) user-defined-id

Definition at line 425 of file Constraint.h.

◆ getVelocityError()

void getVelocityError	(	const Math::VectorNd &	derrSys,
		Math::VectorNd &	derrConstraint
	)

inline

Parameters

derrSys	a reference to the system's constraint velocity error
derrConstraint	a reference to this constraint's entry within the system constraint velocity error.

Definition at line 473 of file Constraint.h.

References MX_Xd_dynamic::block().

◆ getVelocityLevelError()

bool getVelocityLevelError ( unsigned int constraintSubIndex )

inline

Returns the boolean value that determines whether or not velocity-level errors are computed for this sub-index into this constraint.

Parameters

constraintSubIndex the sub index of interest in this constraint

Definition at line 679 of file Constraint.h.

◆ isBaumgarteStabilizationEnabled()

bool isBaumgarteStabilizationEnabled ( )

inline

Returns: true if Baumgarte stabilization is enabled, false otherwise.

Definition at line 573 of file Constraint.h.

◆ setBaumgarteTimeConstant()

void setBaumgarteTimeConstant ( double tStab )

inline

Calculates and sets the Baumgarte stabilization coefficients as a function of tStab, the approximate time-constant of stabilization.

Parameters

tStab : a time-constant that is used to compute values for the position and velocity level stabilization terms. Note that a smaller time constant means stronger stabilization forces and a numerically stiffer system.

Definition at line 555 of file Constraint.h.

◆ setEnableBaumgarteStabilization()

void setEnableBaumgarteStabilization ( bool flagEnableBaumgarteStabilization )

inline

Parameters

flagEnableBaumgarteStabilization setting this to true will enable Baumgarte stabilization for this constraint.

Definition at line 566 of file Constraint.h.

◆ setUserDefinedId()

void setUserDefinedId ( unsigned int userDefinedId )

inline

Parameters

userDefinedId (optional) integer id for this constraint

Definition at line 432 of file Constraint.h.

Field Documentation

◆ baumgarteEnabled

bool baumgarteEnabled

protected

A flag which enables or disables Baumgarte stabilization.

Definition at line 733 of file Constraint.h.

◆ baumgarteParameters

Math::Vector2d baumgarteParameters

protected

The Baumgarte stabilization coefficients at the position and velocity level

Definition at line 730 of file Constraint.h.

◆ bodyFrames

std::vector< Math::SpatialTransform > bodyFrames

protected

Transform from the frame of the predecessor body to the constraint frame.

Definition at line 726 of file Constraint.h.

◆ bodyIds

std::vector< unsigned int > bodyIds

protected

The index of the predecessor body in the vector of bodies in Model.

Definition at line 723 of file Constraint.h.

◆ id

unsigned int id

protected

A user defined id which is unique to this constraint set.

Definition at line 712 of file Constraint.h.

◆ name

std::string name

protected

A user defined name which is unique to this constraint set.

Definition at line 709 of file Constraint.h.

◆ positionConstraint

std::vector< bool > positionConstraint

protected

A mask that is used to selectively enable/disable the calculation of position-level and velocity-level errors. These errors are used to functions that assemble the system at the position and velocity levels, and also by functions that stablize the constraint error at the position and velocity level.

Definition at line 740 of file Constraint.h.

◆ rowInSystem

unsigned int rowInSystem

protected

The first row in G that corresponds to this constraint.

Definition at line 720 of file Constraint.h.

◆ sizeOfConstraint

unsigned int sizeOfConstraint

protected

The number of rows that this constraint adds to G.

Definition at line 717 of file Constraint.h.

◆ typeOfConstraint

unsigned int typeOfConstraint

protected

The type of this constraint.

Definition at line 714 of file Constraint.h.

◆ velocityConstraint

std::vector< bool > velocityConstraint

protected

Definition at line 741 of file Constraint.h.

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

include/rbdl/Constraint.h

Public Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ ~Constraint()

◆ Constraint() [1/2]

◆ Constraint() [2/2]

Member Function Documentation

◆ addInBaumgarteStabilizationForces()

◆ addToConstraintSet()

◆ bind()

◆ calcConstraintForces()

◆ calcConstraintJacobian()

◆ calcGamma()

◆ calcPositionError()

◆ calcVelocityError()

◆ enableConstraintErrorFromAccelerationLevel() [1/2]

◆ enableConstraintErrorFromAccelerationLevel() [2/2]

◆ enableConstraintErrorFromPositionLevel() [1/2]

◆ enableConstraintErrorFromPositionLevel() [2/2]

◆ enableConstraintErrorFromVelocityLevel() [1/2]

◆ enableConstraintErrorFromVelocityLevel() [2/2]

◆ getBaumgarteStabilizationForces()

◆ getBaumgarteStabilizationParameters()

◆ getBodyFrames()

◆ getBodyIds()

◆ getConstraintIndex()

◆ getConstraintJacobian()

◆ getConstraintSize()

◆ getConstraintType()

◆ getGamma()

◆ getName()

◆ getPositionError()

◆ getPositionLevelError()

◆ getUserDefinedId()

◆ getVelocityError()

◆ getVelocityLevelError()

◆ isBaumgarteStabilizationEnabled()

◆ setBaumgarteTimeConstant()

◆ setEnableBaumgarteStabilization()

◆ setUserDefinedId()

Field Documentation

◆ baumgarteEnabled

◆ baumgarteParameters

◆ bodyFrames

◆ bodyIds

◆ id

◆ name

◆ positionConstraint

◆ rowInSystem

◆ sizeOfConstraint

◆ typeOfConstraint

◆ velocityConstraint