Arbitrary discrete body forces and mobility (generalized) forces. Useful for applying external forces or forces that are updated at discrete times due to the occurrence of events. More...

#include <Force_DiscreteForces.h>

Inheritance diagram for SimTK::Force::DiscreteForces:

List of all members.

Public Member Functions
	DiscreteForces (GeneralForceSubsystem &forces, const SimbodyMatterSubsystem &matter)
	Create a DiscreteForces force element.
	DiscreteForces ()
	Default constructor creates an empty handle.
void	clearAllForces (State &state) const
	Set to zero all forces stored by this force element in the given state, including both generalized forces and body spatial forces.
void	clearAllMobilityForces (State &state) const
	Set to zero all generalized forces stored by this force element in the given state.
void	clearAllBodyForces (State &state) const
	Set to zero all body spatial forces (force and torques) stored by this force element in the given state.
void	setOneMobilityForce (State &state, const MobilizedBody &mobod, MobilizerUIndex whichU, Real force) const
	Change the value of a generalized force to be applied in the given state.
void	setOneBodyForce (State &state, const MobilizedBody &mobod, const SpatialVec &spatialForceInG) const
	Change the value of the discrete spatial force (force and torque) to be applied to a body in the given state.
void	addForceToBodyPoint (State &state, const MobilizedBody &mobod, const Vec3 &pointInB, const Vec3 &forceInG) const
	Convenience method to add in a force applied at a point (station) on a particular body into the forces currently set to be applied to that body in this state.
void	setAllMobilityForces (State &state, const Vector &f) const
	Set all the generalized forces at once.
void	setAllBodyForces (State &state, const Vector_< SpatialVec > &bodyForcesInG) const
	Set all the body spatial forces at once.
Real	getOneMobilityForce (const State &state, const MobilizedBody &mobod, MobilizerUIndex whichU) const
	Return the value for a generalized force that is stored in the given state.
SpatialVec	getOneBodyForce (const State &state, const MobilizedBody &mobod) const
	Return the value for the discrete spatial force (force and torque) on a particular body that is stored in the given state.
const Vector &	getAllMobilityForces (const State &state) const
	Get a reference to the internal Vector of all the generalized forces currently set to be applied by this force element.
const Vector_< SpatialVec > &	getAllBodyForces (const State &state) const
	Get a reference to the internal Vector of all the body spatial forces currently set to be applied by this force element.

Detailed Description

Arbitrary discrete body forces and mobility (generalized) forces. Useful for applying external forces or forces that are updated at discrete times due to the occurrence of events.

See also:: Force::MobilityDiscreteForce

Constructor & Destructor Documentation

SimTK::Force::DiscreteForces::DiscreteForces	(	GeneralForceSubsystem &	forces,
		const SimbodyMatterSubsystem &	matter
	)

Create a DiscreteForces force element.

Parameters:

forces	Subsystem to which this force element should be added.
matter	Subsystem containing the mobilized bodies to which these forces will be applied.

SimTK::Force::DiscreteForces::DiscreteForces ( ) [inline]

Default constructor creates an empty handle.

Member Function Documentation

void SimTK::Force::DiscreteForces::clearAllForces ( State & state ) const [inline]

Set to zero all forces stored by this force element in the given state, including both generalized forces and body spatial forces.

void SimTK::Force::DiscreteForces::clearAllMobilityForces ( State & state ) const

Set to zero all generalized forces stored by this force element in the given state.

void SimTK::Force::DiscreteForces::clearAllBodyForces ( State & state ) const

Set to zero all body spatial forces (force and torques) stored by this force element in the given state.

void SimTK::Force::DiscreteForces::setOneMobilityForce	(	State &	state,
		const MobilizedBody &	mobod,
		MobilizerUIndex	whichU,
		Real	force
	)		const

Change the value of a generalized force to be applied in the given state.

Set this to zero if you don't want it to do anything. You can call this method any time after realizeTopology() since the force just needs to be saved in the state.

Parameters:

state	The state in which the generalized force is to be saved.
mobod	The mobilizer to which the force should be applied.
whichU	To which of the mobilizer's mobilities (degrees of freedom) should this force be applied (first is 0)?
force	The scalar value of the generalized force.

See also:: getOneMobilityForce()

void SimTK::Force::DiscreteForces::setOneBodyForce	(	State &	state,
		const MobilizedBody &	mobod,
		const SpatialVec &	spatialForceInG
	)		const

Change the value of the discrete spatial force (force and torque) to be applied to a body in the given state.

Set this to zero if you don't want any force applied to the body. You can call this method any time after realizeTopology() since the force just needs to be saved in the state.

Parameters:

state	The state in which the force is to be saved.
mobod	The mobilized body to which the force should be applied.
spatialForceInG	The (torque,force) pair as a SpatialVec. These are expressed in the Ground frame and the force is applied to the body origin.

See also:: getOneBodyForce(), addForceToBodyPoint()

void SimTK::Force::DiscreteForces::addForceToBodyPoint	(	State &	state,
		const MobilizedBody &	mobod,
		const Vec3 &	pointInB,
		const Vec3 &	forceInG
	)		const

Convenience method to add in a force applied at a point (station) on a particular body into the forces currently set to be applied to that body in this state.

The station location is given in the body frame and the force is given in the Ground frame. Note that the state must have been realized to Stage::Position because we need to know the body orientation in order to shift the applied force to the body origin.

Be sure to call setOneBodyForce() to initialize this force to zero before you start accumulating point forces using this method.

Parameters:

state	The state in which the force is saved. Must already have been realized to at least Stage::Position.
mobod	The mobilized body to which the force will be applied.
pointInB	The body station at which the force will be applied, measured and expressed in the body frame.
forceInG	The force vector to be applied, expressed in Ground.

See also:: setOneBodyForce()

void SimTK::Force::DiscreteForces::setAllMobilityForces	(	State &	state,
		const Vector &	f
	)		const

Set all the generalized forces at once.

These will be applied until they are changed.

Parameters:

state	The state in which the generalized forces are saved.
f	The set of n generalized forces. This Vector must be either empty (in which case it is treated as though it were all zero) or the same length as the number of generalized speeds (state.getNU()).

See also:: clearAllMobilityForces()

void SimTK::Force::DiscreteForces::setAllBodyForces	(	State &	state,
		const Vector_< SpatialVec > &	bodyForcesInG
	)		const

Set all the body spatial forces at once.

These will be applied until they are changed.

Parameters:

state	The state in which the forces are saved.
bodyForcesInG	The set of nb spatial forces (torque,force) pairs, expressed in the Ground frame, with the forces applied at each body frame origin. This Vector must be either empty (in which case it is treated as though it were all zero) or the same length as the number of mobilized bodies in the system (and don't forget that Ground is mobilized body 0).

See also:: clearAllBodyForces()

Real SimTK::Force::DiscreteForces::getOneMobilityForce	(	const State &	state,
		const MobilizedBody &	mobod,
		MobilizerUIndex	whichU
	)		const

Return the value for a generalized force that is stored in the given state.

If no calls to setGeneralizedForce() have been made on this state then zero will be returned.

See also:: setOneMobilityForce()

SpatialVec SimTK::Force::DiscreteForces::getOneBodyForce	(	const State &	state,
		const MobilizedBody &	mobod
	)		const

Return the value for the discrete spatial force (force and torque) on a particular body that is stored in the given state.

The result is a force applied at the body origin and expressed in the Ground frame.

See also:: setOneBodyForce()

const Vector& SimTK::Force::DiscreteForces::getAllMobilityForces ( const State & state ) const

Get a reference to the internal Vector of all the generalized forces currently set to be applied by this force element.

This will be length zero if no forces are being applied; otherwise, its length will be the number of generalized speeds u in the given state. The returned reference is a reference into the given state object.

const Vector_<SpatialVec>& SimTK::Force::DiscreteForces::getAllBodyForces ( const State & state ) const

Get a reference to the internal Vector of all the body spatial forces currently set to be applied by this force element.

This will be length zero if no body forces are being applied; otherwise, its length will be the number of mobilized bodies in the containing MultibodySystem. The returned reference is a reference into the given state object.

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

Force_DiscreteForces.h

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation