OpenSim::Force Class Reference

This abstract class represents a force applied to bodies or generalized coordinates during a simulation. More...

#include <Force.h>

Inheritance diagram for OpenSim::Force:

Public Member Functions
	Force ()
	Default constructor.
	Force (const Force &aForce)
	Copy constructor.
virtual	~Force ()
	Destructor.
	Force (DOMElement *aNode)
	deserialization from XML, necessary so that derived classes can (de)serialize
Force &	operator= (const Force &aForce)
	Assignment operator.
void	copyData (const Force &aForce)
	Copy data members from one Force to another.
virtual Object *	copy () const =0
	Construct and return a copy of this object.
virtual OpenSim::Array < std::string >	getRecordLabels () const
	Methods to query a Force for the value actually applied during simulation The names of the quantities (column labels) is returned by this first function getRecordLabels().
virtual OpenSim::Array< double >	getRecordValues (const SimTK::State &state) const
	Given SimTK::State object extract all the values necessary to report forces, application location frame, etc.
virtual bool	isDisabled (const SimTK::State &s) const
	return if the Force is disabled or not
virtual void	setDisabled (SimTK::State &s, bool disabled)
	Set the Force as disabled (true) or not (false).
virtual int	getNumStateVariables () const
	Get the number of state variables allocated by this force.
virtual bool	hasGeometryPath () const
	return a flag indicating whether the Force is applied along a Path if you override this method to return true for a specific subclass, it must also implement the getGeometryPath() mathod
	OPENSIM_DECLARE_DERIVED (Force, Object)
Protected Member Functions
virtual void	setup (Model &model)
	Subclasses should override these methods appropriately.
virtual void	initState (SimTK::State &state) const
	This is called after a SimTK System and State have been created for the Model.
virtual void	createSystem (SimTK::MultibodySystem &system) const
	Default is to create a ForceAdapter which is a SimTK::Force::Custom as the udnerlying computational component.
virtual void	setDefaultsFromState (const SimTK::State &state)
	Set all default values for this object to match those in a specified State.
virtual void	computeForce (const SimTK::State &state, SimTK::Vector_< SimTK::SpatialVec > &bodyForces, SimTK::Vector &generalizedForces) const
	Subclasses must implement this method to compute the forces that should be applied to bodies and generalized speeds.
virtual double	computePotentialEnergy (const SimTK::State &state) const
	Subclasses may optionally override this method to compute a contribution to the potential energy of the system.
void	applyForce (const SimTK::State &s, const OpenSim::Body &aBody, const SimTK::Vec3 &aForce, SimTK::Vector_< SimTK::SpatialVec > &bodyForces) const
	Apply a force to a particular body.
void	applyForceToPoint (const SimTK::State &s, const OpenSim::Body &aBody, const SimTK::Vec3 &aPoint, const SimTK::Vec3 &aForce, SimTK::Vector_< SimTK::SpatialVec > &bodyForces) const
	Apply a force to a particular body.
void	applyTorque (const SimTK::State &s, const OpenSim::Body &aBody, const SimTK::Vec3 &aTorque, SimTK::Vector_< SimTK::SpatialVec > &bodyForces) const
	Apply a torque to a particular body.
void	applyGeneralizedForce (const SimTK::State &s, const Coordinate &aCoord, double aForce, SimTK::Vector &generalizedForces) const
	Apply a generalized force.
Protected Attributes
PropertyBool	_isDisabledProp
	Flag indicating whether the force is disabled or not.
SimTK::ForceIndex	_index
	ID for the force in Simbody.
Friends
class	ForceAdapter

Detailed Description

This abstract class represents a force applied to bodies or generalized coordinates during a simulation.

Each subclass represents a different type of force. The actual force computation is done by a SimTK::Force, which is created by createSystem().

Author:: Peter Eastman; Ajay Seth

Constructor & Destructor Documentation

OpenSim::Force::Force ( )

Default constructor.

OpenSim::Force::Force ( const Force & aForce )

Copy constructor.

Parameters:

aForce

Force to be copied.

OpenSim::Force::~Force ( ) [virtual]

Destructor.

OpenSim::Force::Force ( DOMElement * aNode ) [inline]

deserialization from XML, necessary so that derived classes can (de)serialize

Member Function Documentation

void OpenSim::Force::applyForce	(	const SimTK::State &	s,
		const OpenSim::Body &	aBody,
		const SimTK::Vec3 &	aForce,
		SimTK::Vector_< SimTK::SpatialVec > &	bodyForces
	)			const `[protected]`

Apply a force to a particular body.

This method applies only a force, not a torque, which is equivalent to applying the force at the body's center of mass.

This method may only be called from inside computeForce(). Invoking it at any other time will produce an exception.

Parameters:

	aBody	the body to apply the force to
	aForce	the force to apply, specified in the inertial frame
	bodyForces	the current set of system bodyForces this force is added to

void OpenSim::Force::applyForceToPoint	(	const SimTK::State &	s,
		const OpenSim::Body &	aBody,
		const SimTK::Vec3 &	aPoint,
		const SimTK::Vec3 &	aForce,
		SimTK::Vector_< SimTK::SpatialVec > &	bodyForces
	)			const `[protected]`

Apply a force to a particular body.

Based on what point the force is applied at, this method automatically determines the torque produced by the force and applies that as well.

This method may only be called from inside computeForce(). Invoking it at any other time will produce an exception.

Parameters:

	aBody	the body to apply the force to
	aPoint	the point at which to apply the force, specifieid in the inertial frame
	aForce	the force to apply, specified in the body's frame
	bodyForces	the current set of system bodyForces this force is added to

void OpenSim::Force::applyGeneralizedForce	(	const SimTK::State &	s,
		const Coordinate &	aCoord,
		double	aForce,
		SimTK::Vector &	generalizedForces
	)			const `[protected]`

Apply a generalized force.

This method may only be called from inside computeForce(). Invoking it at any other time will produce an exception.

Parameters:

	aCoord	the generalized coordinate to apply the force to
	aForce	the force to apply
	generalizedForces	the current set of system generalizedForces this force is added to

void OpenSim::Force::applyTorque	(	const SimTK::State &	s,
		const OpenSim::Body &	aBody,
		const SimTK::Vec3 &	aTorque,
		SimTK::Vector_< SimTK::SpatialVec > &	bodyForces
	)			const `[protected]`

Apply a torque to a particular body.

This method may only be called from inside computeForce(). Invoking it at any other time will produce an exception.

Parameters:

	aBody	the body to apply the force to
	aTorque	the torque to apply, specified in the inertial frame
	bodyForces	the current set of system bodyForces this force is added to

virtual void OpenSim::Force::computeForce	(	const SimTK::State &	state,
		SimTK::Vector_< SimTK::SpatialVec > &	bodyForces,
		SimTK::Vector &	generalizedForces
	)			const `[inline, protected, virtual]`

Subclasses must implement this method to compute the forces that should be applied to bodies and generalized speeds.

This is invoked by ForceAdapter to perform the force computation.

Reimplemented in OpenSim::CoordinateActuator, OpenSim::CoordinateLimitForce, OpenSim::PointActuator, OpenSim::PointToPointActuator, OpenSim::RigidTendonMuscle, OpenSim::SpringGeneralizedForce, OpenSim::TorqueActuator, OpenSim::ActivationFiberLengthMuscle, OpenSim::ExternalForce, OpenSim::Ligament, OpenSim::LinearSpring, OpenSim::Muscle, OpenSim::PathActuator, OpenSim::PrescribedForce, and OpenSim::TorsionalSpring.

double OpenSim::Force::computePotentialEnergy ( const SimTK::State & state ) const [protected, virtual]

Subclasses may optionally override this method to compute a contribution to the potential energy of the system.

The default implementation returns 0, which is appropriate for forces that do not contribute to potential energy.

Reimplemented in OpenSim::BushingForce.

virtual Object* OpenSim::Force::copy ( ) const [pure virtual]

Construct and return a copy of this object.

The object is allocated using the new operator, so the caller is responsible for deleting the returned object.

Returns:: Copy of this object.

Reimplemented from OpenSim::Object.

Implemented in OpenSim::ContDerivMuscle, OpenSim::CoordinateActuator, OpenSim::CoordinateLimitForce, OpenSim::Delp1990Muscle, OpenSim::PointActuator, OpenSim::PointToPointActuator, OpenSim::RigidTendonMuscle, OpenSim::Schutte1993Muscle, OpenSim::SpringGeneralizedForce, OpenSim::Thelen2003Muscle, OpenSim::TorqueActuator, OpenSim::ActivationFiberLengthMuscle, OpenSim::Actuator_, OpenSim::Actuator, OpenSim::BushingForce, OpenSim::ElasticFoundationForce, OpenSim::ElasticFoundationForce, OpenSim::ElasticFoundationForce, OpenSim::ExternalForce, OpenSim::HuntCrossleyForce, OpenSim::HuntCrossleyForce, OpenSim::HuntCrossleyForce, OpenSim::Ligament, OpenSim::LinearSpring, OpenSim::Muscle, OpenSim::PathActuator, OpenSim::PointToPointSpring, OpenSim::PrescribedForce, and OpenSim::TorsionalSpring.

void OpenSim::Force::copyData ( const Force & aForce )

Copy data members from one Force to another.

Parameters:

aForce

Force to be copied.

Reimplemented in OpenSim::ContDerivMuscle, OpenSim::CoordinateActuator, OpenSim::Delp1990Muscle, OpenSim::PointActuator, OpenSim::PointToPointActuator, OpenSim::RigidTendonMuscle, OpenSim::Schutte1993Muscle, OpenSim::Thelen2003Muscle, OpenSim::TorqueActuator, OpenSim::ActivationFiberLengthMuscle, OpenSim::BushingForce, OpenSim::ElasticFoundationForce, OpenSim::HuntCrossleyForce, OpenSim::Ligament, OpenSim::Muscle, OpenSim::PathActuator, and OpenSim::PointToPointSpring.

void OpenSim::Force::createSystem ( SimTK::MultibodySystem & system ) const [protected, virtual]

Default is to create a ForceAdapter which is a SimTK::Force::Custom as the udnerlying computational component.

Create an underlying SimTK::Force to represent the OpenSim::Force in the computational system.

Subclasses override to employ other SimTK::Forces.

Create a SimTK::Force::Custom by default.

Reimplemented from OpenSim::ModelComponent.

Reimplemented in OpenSim::ContDerivMuscle, OpenSim::CoordinateActuator, OpenSim::Delp1990Muscle, OpenSim::RigidTendonMuscle, OpenSim::Schutte1993Muscle, OpenSim::SpringGeneralizedForce, OpenSim::Thelen2003Muscle, OpenSim::ActivationFiberLengthMuscle, OpenSim::Actuator_, OpenSim::Actuator, OpenSim::BushingForce, OpenSim::ElasticFoundationForce, OpenSim::HuntCrossleyForce, OpenSim::Ligament, OpenSim::Muscle, OpenSim::PathActuator, and OpenSim::PointToPointSpring.

virtual int OpenSim::Force::getNumStateVariables ( ) const [inline, virtual]

Get the number of state variables allocated by this force.

The default implementation returns 0. Subclasses that allocate state variables must override it.

Implements OpenSim::ModelComponent.

Reimplemented in OpenSim::ActivationFiberLengthMuscle.

virtual OpenSim::Array<std::string> OpenSim::Force::getRecordLabels ( ) const [inline, virtual]

Methods to query a Force for the value actually applied during simulation The names of the quantities (column labels) is returned by this first function getRecordLabels().

Reimplemented in OpenSim::CoordinateActuator, OpenSim::CoordinateLimitForce, OpenSim::PointActuator, OpenSim::PointToPointActuator, OpenSim::RigidTendonMuscle, OpenSim::SpringGeneralizedForce, OpenSim::TorqueActuator, OpenSim::ActivationFiberLengthMuscle, OpenSim::BushingForce, OpenSim::ElasticFoundationForce, OpenSim::ExternalForce, OpenSim::HuntCrossleyForce, OpenSim::Muscle, OpenSim::PathActuator, OpenSim::PointToPointSpring, and OpenSim::PrescribedForce.

virtual OpenSim::Array<double> OpenSim::Force::getRecordValues ( const SimTK::State & state ) const [inline, virtual]

Given SimTK::State object extract all the values necessary to report forces, application location frame, etc.

used in conjunction with getRecordLabels and should return same size Array

Reimplemented in OpenSim::CoordinateActuator, OpenSim::CoordinateLimitForce, OpenSim::PointActuator, OpenSim::PointToPointActuator, OpenSim::RigidTendonMuscle, OpenSim::SpringGeneralizedForce, OpenSim::TorqueActuator, OpenSim::ActivationFiberLengthMuscle, OpenSim::BushingForce, OpenSim::ElasticFoundationForce, OpenSim::ExternalForce, OpenSim::HuntCrossleyForce, OpenSim::Muscle, OpenSim::PathActuator, OpenSim::PointToPointSpring, and OpenSim::PrescribedForce.

virtual bool OpenSim::Force::hasGeometryPath ( ) const [inline, virtual]

return a flag indicating whether the Force is applied along a Path if you override this method to return true for a specific subclass, it must also implement the getGeometryPath() mathod

Reimplemented in OpenSim::Ligament, and OpenSim::PathActuator.

void OpenSim::Force::initState ( SimTK::State & state ) const [protected, virtual]

This is called after a SimTK System and State have been created for the Model.

It must be implementd to set initial values of state variables.

Parameters:

state

the State to initialize

Reimplemented from OpenSim::ModelComponent.

Reimplemented in OpenSim::RigidTendonMuscle, OpenSim::ActivationFiberLengthMuscle, OpenSim::Actuator_, OpenSim::Actuator, OpenSim::Ligament, OpenSim::LinearSpring, and OpenSim::Muscle.

bool OpenSim::Force::isDisabled ( const SimTK::State & s ) const [virtual]

return if the Force is disabled or not