OpenSim::LinearSpring Class Reference

#include <LinearSpring.h>

Inheritance diagram for OpenSim::LinearSpring:

List of all members.

Public Member Functions
	LinearSpring (const Body &aBody, double start, double stop)
	Construct a Linear Spring.
virtual	~LinearSpring ()
	Destructor.
void	setTargetPosition (VectorFunction *aTargetVelocity)
	Set the vector function containing the (t,x,y,z) of the position that the point should be corrected towards, expressed in the global ref frame.
VectorFunction *	getTargetPosition () const
	Get the vector function containing the (t,x,y,z) of the poisiton that the point should be corrected towards, expressed in the global ref frame.
void	setPointFunction (VectorFunction *aPointFunction)
	Set the vector function containing the (t,x,y,z) of the point at which the force should be applied in the local coordinate frame.
void	setTargetVelocity (VectorFunction *aTargetVelocity)
	Set the vector function containing the (t,x,y,z) of the velocity that the point should be corrected towards, expressed in the global ref frame.
VectorFunction *	getTargetVelocity () const
	Get the vector function containing the (t,x,y,z) of the velocity that the point should be corrected towards, expressed in the global ref frame.
void	setScaleFunction (Function *_scaleFunction)
	Set the function containing the scale factor as a function of time.
Function *	getScaleFunction () const
	Get the function containing the scale factor as a function of time.
void	setScaleFactor (double aScaleFactor)
	Set the scale factor that pre-multiplies the applied torque.
double	getScaleFactor ()
	Get the scale factor that pre-multiplies the applied torque.
void	setKValue (const SimTK::Vec3 &aK)
	Set the spring constant, k.
void	getKValue (SimTK::Vec3 &aK) const
	Get the spring constant, k.
void	setBValue (const SimTK::Vec3 &aB)
	Set the damping constant, b.
void	getBValue (SimTK::Vec3 &aB) const
	Get the damping constant, b.
void	setThreshold (double aThreshold)
	Set the magnitude theshold below which no force is applied.
double	getThreshold () const
	Get the magnitude theshold below which no force is applied.
void	computePointAndTargetFunctions (SimTK::State &s, const Storage &aQStore, const Storage &aUStore, VectorFunction &aPGlobal)
	Compute the local point on a body and the point's target position and velocity in space that it should track.
void	computePointFunction (SimTK::State &s, const Storage &aQStore, const Storage &aUStore, VectorFunction &aPGlobal)
	Compute the position and velocity functions that set the position and velocity of the point at which the linear spring applies its force.
void	computeTargetFunctions (SimTK::State &s, const Storage &aQStoreForTarget, const Storage &aUStoreForTarget)
virtual void	computeForce (const SimTK::State &s) const
	Callback called right after actuation has been applied by the model.
Protected Attributes
VectorFunction *	_pointFunction
	VectorFunction containing points of force application (t,x,y,z).
VectorFunction *	_forceFunction
	VectorFunction containing force to be applied (t,x,y,z).
VectorFunction *	_targetPosition
	Vector function containing the target position of the point expressed in the global reference frame.
VectorFunction *	_targetVelocity
	Vector function containing the target velocity of the point expressed in the global reference frame.
Function *	_scaleFunction
	Function containing values for the time-dependent scaling factor.
double	_scaleFactor
	Scale factor that pre-multiplies the applied torque.
SimTK::Vec3	_k
	Stiffness.
SimTK::Vec3	_b
	Damping.
double	_threshold
	If the magnitude of the spring force is below this threshold, no spring force is applied.
const Body &	_body
bool	_on
	On, off flag.
double	_startTime
	Start time for the force.
double	_endTime
	End time for the force.

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Constructor & Destructor Documentation

LinearSpring::LinearSpring	(	const Body &	aBody,
		double	startTime,
		double	endTime
	)

Construct a Linear Spring.

Parameters:

aBody

Body upon which spring forces are to be applied.

LinearSpring::~LinearSpring

(

)

[virtual]

Destructor.

---

Member Function Documentation

void LinearSpring::computeForce

(

const SimTK::State &

s

)

const [virtual]

Callback called right after actuation has been applied by the model.

*

Parameters:

	aT	Real time.
	aX	Controls.
	aY	States.

Implements OpenSim::CustomForce.

void LinearSpring::computePointAndTargetFunctions	(	SimTK::State &	s,
		const Storage &	aQStore,
		const Storage &	aUStore,
		VectorFunction &	aPGlobal
	)

Compute the local point on a body and the point's target position and velocity in space that it should track.

A spring force is applied based on the difference between the point's position and velocity and the target position and velocity. The point is specified in the local frame; the target position and velocity are specified in the global frame.

Parameters:

	aQStore	Storage containing the time history of generalized coordinates for the model. Note that all generalized coordinates must be specified and in radians and Euler parameters.
	aUStore	Stoarge containing the time history of generalized speeds for the model. Note that all generalized speeds must be specified and in radians.
	aPStore	Storage containing the time history of the position of the point in the global frame.

void LinearSpring::computePointFunction	(	SimTK::State &	s,
		const Storage &	aQStore,
		const Storage &	aUStore,
		VectorFunction &	aPGlobal
	)

Compute the position and velocity functions that set the position and velocity of the point at which the linear spring applies its force.

This method takes the time histories of a point's position and velocity in the inertial frame and converts them to the local (body) frame.

Parameters:

	aQStore	Storage containing the time history of generalized coordinates for the model. Note that all generalized coordinates must be specified and in radians and Euler parameters.
	aUStore	Storage containing the time history of generalized speeds for the model. Note that all generalized speeds must be specified and in radians.
	aPStore	Storage containing the time history of the position at which the force is to be applied in the global frame.

void LinearSpring::computeTargetFunctions	(	SimTK::State &	s,
		const Storage &	aQStoreForTarget,
		const Storage &	aUStoreForTarget
	)

void LinearSpring::getBValue

(

SimTK::Vec3 &

aB

)

const

Get the damping constant, b.

Returns:

aB.

void LinearSpring::getKValue

(

SimTK::Vec3 &

aK

)

const

Get the spring constant, k.

Returns:

aK.

double LinearSpring::getScaleFactor

(

)

Get the scale factor that pre-multiplies the applied torque.

Returns:

aScaleFactor.

Function * LinearSpring::getScaleFunction

(

)

const

Get the function containing the scale factor as a function of time.

Returns:

aScaleFunction.

VectorFunction * LinearSpring::getTargetPosition

(

)

const

Get the vector function containing the (t,x,y,z) of the poisiton that the point should be corrected towards, expressed in the global ref frame.

Returns:

Vector function containing the target position expressed in the global reference frame.

VectorFunction * LinearSpring::getTargetVelocity

(

)

const

Get the vector function containing the (t,x,y,z) of the velocity that the point should be corrected towards, expressed in the global ref frame.

Returns:

Vector function containing the target velocity expressed in the global reference frame.

double LinearSpring::getThreshold

(

)

const

Get the magnitude theshold below which no force is applied.

Parameters:

aThreshold

Magnitude threshold. A negative value or 0 will result in the force always being applied.

void LinearSpring::setBValue

(

const SimTK::Vec3 &

aB

)

Set the damping constant, b.

Parameters:

aK

Vector of three values of b.

void LinearSpring::setKValue

(

const SimTK::Vec3 &

aK

)

Set the spring constant, k.

Parameters:

aK

Vector of three values of k.

void LinearSpring::setPointFunction

(

VectorFunction *

aPointFunction

)

Set the vector function containing the (t,x,y,z) of the point at which the force should be applied in the local coordinate frame.

Parameters:

aPointFunction

containing force application point function.

void LinearSpring::setScaleFactor

(

double

aScaleFactor

)

Set the scale factor that pre-multiplies the applied torque.

Parameters:

aScaleFactor

void LinearSpring::setScaleFunction

(

Function *

aScaleFunction

)

Set the function containing the scale factor as a function of time.

Parameters:

aScaleFunction.

void LinearSpring::setTargetPosition

(

VectorFunction *

aTargetPosition

)

Set the vector function containing the (t,x,y,z) of the position that the point should be corrected towards, expressed in the global ref frame.

Parameters:

aTargetPosition

Vector function containing the target position expressed in the global reference frame.

void LinearSpring::setTargetVelocity

(

VectorFunction *

aTargetVelocity

)

Set the vector function containing the (t,x,y,z) of the velocity that the point should be corrected towards, expressed in the global ref frame.

Parameters:

aTargetVelocity

Vector function containing the target velocity expressed in the global reference frame.

void LinearSpring::setThreshold

(

double

aThreshold

)

Set the magnitude theshold below which no force is applied.

Parameters:

aThreshold

Magnitude threshold. A negative value or 0 will result in the force always being applied.

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Member Data Documentation

SimTK::Vec3 OpenSim::LinearSpring::_b [protected]

Damping.

const Body& OpenSim::LinearSpring::_body [protected]

double OpenSim::LinearSpring::_endTime [protected]

End time for the force.

VectorFunction* OpenSim::LinearSpring::_forceFunction [protected]

VectorFunction containing force to be applied (t,x,y,z).

SimTK::Vec3 OpenSim::LinearSpring::_k [protected]

Stiffness.

bool OpenSim::LinearSpring::_on [protected]

On, off flag.

VectorFunction* OpenSim::LinearSpring::_pointFunction [protected]

VectorFunction containing points of force application (t,x,y,z).

double OpenSim::LinearSpring::_scaleFactor [protected]

Scale factor that pre-multiplies the applied torque.

Function* OpenSim::LinearSpring::_scaleFunction [protected]

Function containing values for the time-dependent scaling factor.

double OpenSim::LinearSpring::_startTime [protected]

Start time for the force.

VectorFunction* OpenSim::LinearSpring::_targetPosition [protected]

Vector function containing the target position of the point expressed in the global reference frame.

VectorFunction* OpenSim::LinearSpring::_targetVelocity [protected]

Vector function containing the target velocity of the point expressed in the global reference frame.

double OpenSim::LinearSpring::_threshold [protected]

If the magnitude of the spring force is below this threshold, no spring force is applied.

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

• OpenSim/Simulation/Model/LinearSpring.h
• OpenSim/Simulation/Model/LinearSpring.cpp