Description

This path constraint enforces that the distance between the origins of pairs of model frames is kept between minimum and maximum bounds.

Frame pairs and their bounds are specified via a MocoFrameDistancConstraintPair. Any model component derived from Frame is valid to be included in a frame pair, and any number of frame pairs may be append to this constraint via addFramePair().

This constraint can be used as a simple method for preventing bodies in your model from intersecting during an optimization. For example, the following prevents feet from intersecting during a walking optimization:

distance = problem.addPathConstraint<MocoFrameDistanceConstraint>();
distance.setName("minimum_distance");
SimTK::Real inf = SimTK::Infinity;
distance.addFramePair('/bodyset/calcn_l', '/bodyset/calcn_r', 0.1, inf);
distance.addFramePair('/bodyset/toes_l', '/bodyset/toes_r', 0.1, inf);
distance.addFramePair('/bodyset/calcn_l', '/bodyset/toes_r', 0.1, inf);
distance.addFramePair('/bodyset/toes_l', '/bodyset/calcn_r', 0.1, inf);

To project the frame distance onto a vector or plane before ensuring its within the provided bounds, use setProjection() and setProjectionVector().

Note: This class represents a path constraint, not a model kinematic constraint. Therefore, there are no Lagrange multipliers or constraint forces associated with this constraint. The model's force elements (including actuators) must generate the forces necessary for satisfying this constraint.

Inheritance diagram for OpenSim::MocoFrameDistanceConstraint:

#include <Moco/Moco/MocoFrameDistanceConstraint.h>

Public Member Functions
void	addFramePair (MocoFrameDistanceConstraintPair pair)

void	addFramePair (const std::string &frame1_path, const std::string &frame2_path, double minimum_distance, double maximum_distance)

void	setProjection (std::string projection)
	Set if each distance should be projected onto either a vector or plane. More...

std::string	getProjection () const

void	setProjectionVector (SimTK::Vec3 normal)
	Set the vector to use for projecting each distance. More...

void	clearProjectionVector ()
	Unset the projection vector.

SimTK::Vec3	getProjectionVector () const

Public Member Functions inherited from OpenSim::MocoPathConstraint
const MocoConstraintInfo &	getConstraintInfo () const

MocoConstraintInfo &	updConstraintInfo ()

void	setConstraintInfo (const MocoConstraintInfo &cInfo)

int	getPathConstraintIndex () const
	For use by solvers. More...

void	calcPathConstraintErrors (const SimTK::State &state, SimTK::Vector &errors) const
	Calculate errors in the path constraint equations. More...

void	initializeOnModel (const Model &model, const MocoProblemInfo &, const int &pathConstraintIndex) const
	For use by solvers. This also performs error checks on the Problem.

Protected Member Functions
void	initializeOnModelImpl (const Model &model, const MocoProblemInfo &) const override
	Perform any caching. More...

void	calcPathConstraintErrorsImpl (const SimTK::State &state, SimTK::Vector &errors) const override

Protected Member Functions inherited from OpenSim::MocoPathConstraint
	OpenSim_DECLARE_UNNAMED_PROPERTY (MocoConstraintInfo, "The bounds and " "labels for this MocoPathConstraint.")

void	setNumEquations (int numEqs) const
	Set the number of scalar equations for this MocoPathConstraint. More...

const Model &	getModel () const
	For use within virtual function implementations.

Member Function Documentation

◆ calcPathConstraintErrorsImpl()

void OpenSim::MocoFrameDistanceConstraint::calcPathConstraintErrorsImpl	(	const SimTK::State &	state,
		SimTK::Vector &	errors
	)		const

overrideprotectedvirtual

Precondition(s):: The state is realized to SimTK::Stage::Position. If you need access to the controls, you must realize to Velocity:
getModel().realizeVelocity(state);

Implements OpenSim::MocoPathConstraint.

◆ initializeOnModelImpl()

void OpenSim::MocoFrameDistanceConstraint::initializeOnModelImpl	(	const Model &	,
		const MocoProblemInfo &
	)		const

overrideprotectedvirtual

Perform any caching.

The number of scalar constraint equations this MocoPathConstraint implements must be defined here (see setNumEquations() below).

Precondition(s):: The model is initialized (initSystem()) and getModel() is available. The passed-in model is equivalent to getModel(). Use this opportunity to check for errors in user input, in addition to the checks provided in initialize().

Implements OpenSim::MocoPathConstraint.

◆ setProjection()

void OpenSim::MocoFrameDistanceConstraint::setProjection ( std::string projection )

inline

Set if each distance should be projected onto either a vector or plane.

Possible values: "none" (default), "vector", and "plane".

◆ setProjectionVector()

void OpenSim::MocoFrameDistanceConstraint::setProjectionVector ( SimTK::Vec3 normal )

inline

Set the vector to use for projecting each distance.

If the projection type is "vector", the distance is projected onto the vector provided here. If the projection type is "plane", the distance is projected onto the plane perpendicular to this vector.

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

MocoFrameDistanceConstraint.h