OpenSim::ActivationFiberLengthMuscle Class Reference

A base class representing a muscle-tendon actuator. More...

#include <ActivationFiberLengthMuscle.h>

Inheritance diagram for OpenSim::ActivationFiberLengthMuscle:

List of all members.

Public Member Functions
	ActivationFiberLengthMuscle ()
	Default constructor.
	ActivationFiberLengthMuscle (const ActivationFiberLengthMuscle &aMuscle)
	Copy constructor.
virtual	~ActivationFiberLengthMuscle ()
	Destructor.
virtual Object *	copy () const =0
	Copy this actuator and return a pointer to the copy.
void	setName (const std::string &aName)
ActivationFiberLengthMuscle &	operator= (const ActivationFiberLengthMuscle &aMuscle)
	Assignment operator.
void	copyData (const ActivationFiberLengthMuscle &aMuscle)
	Copy data members from one ActivationFiberLengthMuscle to another.
virtual void	updateFromXMLNode ()
	Override of the default implementation to account for versioning.
virtual void	equilibrate (SimTK::State &state) const
virtual int	getNumStateVariables () const
	Get the number of state variables allocated by this force.
virtual double	getDefaultActivation () const
virtual void	setDefaultActivation (double activation)
virtual double	getDefaultFiberLength () const
virtual void	setDefaultFiberLength (double length)
virtual double	getFiberLength (const SimTK::State &s) const
virtual void	setFiberLength (SimTK::State &s, double fiberLength) const
virtual double	getFiberLengthDeriv (const SimTK::State &s) const
virtual void	setFiberLengthDeriv (const SimTK::State &s, double fiberLengthDeriv) const
virtual double	getNormalizedFiberLength (const SimTK::State &s) const
	/** Get the normalized length of the muscle fiber(s).
virtual double	getFiberLengthAlongTendon (const SimTK::State &s) const
	Get the length of the muscle fiber(s) along the tendon.
virtual double	getTendonLength (const SimTK::State &s) const
	Get the length of the tendon.
virtual double	getFiberForce (const SimTK::State &s) const
	Compute the force generated by the muscle fibers.
virtual double	getActiveFiberForce (const SimTK::State &s) const
	Get the active force generated by the muscle fibers.
virtual double	getPassiveFiberForce (const SimTK::State &s) const
	Get the passive force generated by the muscle fibers.
virtual double	getActiveFiberForceAlongTendon (const SimTK::State &s) const
	Get the active force generated by the muscle fibers along the direction of the tendon.
virtual double	getPassiveFiberForceAlongTendon (const SimTK::State &s) const
	Get the passive force generated by the muscle fibers along the direction of the tendon.
virtual double	getPassiveForce (const SimTK::State &s) const
virtual void	setPassiveForce (const SimTK::State &s, double aForce) const
virtual double	getTendonForce (const SimTK::State &s) const
virtual void	setTendonForce (const SimTK::State &s, double aForce) const
virtual double	getActivation (const SimTK::State &s) const
virtual void	setActivation (SimTK::State &s, double activation) const
virtual double	getActivationDeriv (const SimTK::State &s) const
virtual void	setActivationDeriv (const SimTK::State &s, double activationDeriv) const
virtual double	getExcitation (const SimTK::State &s) const
virtual double	getStress (const SimTK::State &s) const
	Get the stress in this actuator.
virtual double	computeActuation (const SimTK::State &s) const =0
	Compute all quantities necessary for applying the actuator force to the model.
virtual double	computeIsometricForce (SimTK::State &s, double activation) const =0
virtual double	computeIsokineticForceAssumingInfinitelyStiffTendon (SimTK::State &s, double aActivation) const
	Find the force produced by muscle under isokinetic conditions assuming an infinitely stiff tendon.
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.
	OPENSIM_DECLARE_DERIVED (ActivationFiberLengthMuscle, Muscle)
Protected Member Functions
virtual void	postScale (const SimTK::State &s, const ScaleSet &aScaleSet)
	Perform computations that need to happen after the muscle is scaled.
virtual void	computeForce (const SimTK::State &state, SimTK::Vector_< SimTK::SpatialVec > &bodyForces, SimTK::Vector &generalizedForce) const
	Apply the muscle's force at its points of attachment to the bodies.
virtual void	setup (Model &aModel)
	Perform set up functions after model has been deserialized or copied.
virtual void	createSystem (SimTK::MultibodySystem &system) const
	allocate and initialize the SimTK state for this acuator.
virtual void	initState (SimTK::State &s) const
	This is called after a SimTK System and State have been created for the Model.
virtual void	setDefaultsFromState (const SimTK::State &state)
	Set all default values for this object to match those in a specified State.
virtual void	setNumStateVariables (int aNumStateVariables)
virtual std::string	getStateVariableName (int aIndex) const
	Get the name of a state variable, given its index.
virtual void	setStateVariableDeriv (const SimTK::State &s, int aIndex, double aValue) const
	Set the derivative of an actuator state, specified by index.
virtual double	getStateVariableDeriv (const SimTK::State &s, int aIndex) const
	Get the derivative of an actuator state, by index.
virtual SimTK::Vector	computeStateVariableDerivatives (const SimTK::State)
Protected Attributes
Array< std::string >	_stateVariableSuffixes
double	_defaultActivation
double	_defaultFiberLength
SimTK::ZIndex	_zIndex
Static Protected Attributes
static const int	STATE_ACTIVATION = 0
static const int	STATE_FIBER_LENGTH = 1

---

Detailed Description

A base class representing a muscle-tendon actuator.

It adds states to the Muscle class, but does not implement all of the necessary methods, so it is abstract too. The path information for a muscle is contained in this class, and the force-generating behavior should be defined in the derived classes.

Author:

Peter Loan

Frank C. Anderson

Ajay Seth

Version:

2.0

---

Constructor & Destructor Documentation

ActivationFiberLengthMuscle::ActivationFiberLengthMuscle

(

)

Default constructor.

ActivationFiberLengthMuscle::ActivationFiberLengthMuscle

(

const ActivationFiberLengthMuscle &

aMuscle

)

Copy constructor.

Parameters:

aMuscle

ActivationFiberLengthMuscle to be copied.

ActivationFiberLengthMuscle::~ActivationFiberLengthMuscle

(

)

[virtual]

Destructor.

---

Member Function Documentation

virtual double OpenSim::ActivationFiberLengthMuscle::computeActuation

(

const SimTK::State &

s

)

const [pure virtual]

Compute all quantities necessary for applying the actuator force to the model.

Implements OpenSim::Muscle.

Implemented in OpenSim::ContDerivMuscle, OpenSim::Delp1990Muscle, OpenSim::Schutte1993Muscle, and OpenSim::Thelen2003Muscle.

void ActivationFiberLengthMuscle::computeForce	(	const SimTK::State &	state,
		SimTK::Vector_< SimTK::SpatialVec > &	bodyForces,
		SimTK::Vector &	generalizedForce
	)			const [protected, virtual]

Apply the muscle's force at its points of attachment to the bodies.

Reimplemented from OpenSim::Muscle.

double ActivationFiberLengthMuscle::computeIsokineticForceAssumingInfinitelyStiffTendon	(	SimTK::State &	s,
		double	aActivation
	)			const [virtual]

Find the force produced by muscle under isokinetic conditions assuming an infinitely stiff tendon.

That is, all the shortening velocity of the actuator (the musculotendon unit) is assumed to be due to the shortening of the muscle fibers alone. This methods calls computeIsometricForce and so alters the internal member variables of this muscle.

Note that the current implementation approximates the effect of the force-velocity curve. It does not account for the shortening velocity when it is solving for the equilibrium length of the muscle fibers. And, a generic representation of the force-velocity curve is used (as opposed to the implicit force-velocity curve assumed by this model.

Parameters:

aActivation

Activation of the muscle.

Returns:

Isokinetic force generated by the actuator.

virtual double OpenSim::ActivationFiberLengthMuscle::computeIsometricForce	(	SimTK::State &	s,
		double	activation
	)			const [pure virtual]

Implements OpenSim::Muscle.

Implemented in OpenSim::ContDerivMuscle, OpenSim::Delp1990Muscle, OpenSim::Schutte1993Muscle, and OpenSim::Thelen2003Muscle.

virtual SimTK::Vector OpenSim::ActivationFiberLengthMuscle::computeStateVariableDerivatives

(

const SimTK::State

)

[inline, protected, virtual]

virtual Object* OpenSim::ActivationFiberLengthMuscle::copy

(

)

const [pure virtual]

Copy this actuator and return a pointer to the copy.

The copy constructor for this class is used.

Returns:

Pointer to a copy of this actuator.

Implements OpenSim::Muscle.

Implemented in OpenSim::ContDerivMuscle, OpenSim::Delp1990Muscle, OpenSim::Schutte1993Muscle, and OpenSim::Thelen2003Muscle.

void ActivationFiberLengthMuscle::copyData

(

const ActivationFiberLengthMuscle &

aMuscle

)

Copy data members from one ActivationFiberLengthMuscle to another.

Parameters:

aMuscle

ActivationFiberLengthMuscle to be copied.

Reimplemented from OpenSim::Muscle.

Reimplemented in OpenSim::ContDerivMuscle, OpenSim::Delp1990Muscle, OpenSim::Schutte1993Muscle, and OpenSim::Thelen2003Muscle.

void ActivationFiberLengthMuscle::createSystem

(

SimTK::MultibodySystem &

system

)

const [protected, virtual]

allocate and initialize the SimTK state for this acuator.

Reimplemented from OpenSim::Muscle.

Reimplemented in OpenSim::ContDerivMuscle, OpenSim::Delp1990Muscle, OpenSim::Schutte1993Muscle, and OpenSim::Thelen2003Muscle.

void ActivationFiberLengthMuscle::equilibrate

(

SimTK::State &

state

)

const [virtual]

Implements OpenSim::Muscle.

double ActivationFiberLengthMuscle::getActivation

(

const SimTK::State &

s

)

const [virtual]

Implements OpenSim::Muscle.

Reimplemented in OpenSim::ContDerivMuscle.

double ActivationFiberLengthMuscle::getActivationDeriv

(

const SimTK::State &

s

)

const [virtual]

Reimplemented in OpenSim::ContDerivMuscle.

double ActivationFiberLengthMuscle::getActiveFiberForce

(

const SimTK::State &

s

)

const [virtual]

Get the active force generated by the muscle fibers.

Returns:

Current active force of the muscle fibers.

Reimplemented from OpenSim::Muscle.

double ActivationFiberLengthMuscle::getActiveFiberForceAlongTendon

(

const SimTK::State &

s

)

const [virtual]

Get the active force generated by the muscle fibers along the direction of the tendon.

Returns:

Current active force of the muscle fibers along tendon.

Reimplemented from OpenSim::Muscle.

double ActivationFiberLengthMuscle::getDefaultActivation

(

)

const [virtual]

double ActivationFiberLengthMuscle::getDefaultFiberLength

(

)

const [virtual]

double ActivationFiberLengthMuscle::getExcitation

(

const SimTK::State &

s

)

const [virtual]

double ActivationFiberLengthMuscle::getFiberForce

(

const SimTK::State &

s

)

const [virtual]

Compute the force generated by the muscle fibers.

This accounts for pennation angle. That is, the fiber force is computed by dividing the actuator force by the cosine of the pennation angle.

Returns:

Force in the muscle fibers.

Reimplemented from OpenSim::Muscle.

double ActivationFiberLengthMuscle::getFiberLength

(

const SimTK::State &

s

)

const [virtual]

Implements OpenSim::Muscle.

Reimplemented in OpenSim::ContDerivMuscle.

double ActivationFiberLengthMuscle::getFiberLengthAlongTendon

(

const SimTK::State &

s

)

const [virtual]

Get the length of the muscle fiber(s) along the tendon.

This method accounts for the pennation angle.

Returns:

Current length of the muscle fiber(s) along the direction of the tendon.

Reimplemented from OpenSim::Muscle.

double ActivationFiberLengthMuscle::getFiberLengthDeriv

(

const SimTK::State &

s

)

const [virtual]

Reimplemented in OpenSim::ContDerivMuscle.

double ActivationFiberLengthMuscle::getNormalizedFiberLength

(

const SimTK::State &

s

)

const [virtual]

/** Get the normalized length of the muscle fiber(s).

This is the current fiber length(s) divided by the optimal fiber length.

Parameters:

Current

length of the muscle fiber(s).

Implements OpenSim::Muscle.

Reimplemented in OpenSim::ContDerivMuscle.

int ActivationFiberLengthMuscle::getNumStateVariables

(

)

const [virtual]

Get the number of state variables allocated by this force.

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

Reimplemented from OpenSim::Force.

double ActivationFiberLengthMuscle::getPassiveFiberForce

(

const SimTK::State &

s

)

const [virtual]

Get the passive force generated by the muscle fibers.

Parameters:

Current

passive force of the muscle fiber(s).

Implements OpenSim::Muscle.

Reimplemented in OpenSim::ContDerivMuscle.

double ActivationFiberLengthMuscle::getPassiveFiberForceAlongTendon

(

const SimTK::State &

s

)

const [virtual]

Get the passive force generated by the muscle fibers along the direction of the tendon.

Returns:

Current passive force of the muscle fibers along tendon.

Reimplemented from OpenSim::Muscle.

double ActivationFiberLengthMuscle::getPassiveForce

(

const SimTK::State &

s

)

const [virtual]

Reimplemented in OpenSim::ContDerivMuscle.

virtual OpenSim::Array<std::string> OpenSim::ActivationFiberLengthMuscle::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 from OpenSim::Muscle.

virtual OpenSim::Array<double> OpenSim::ActivationFiberLengthMuscle::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 from OpenSim::Muscle.

double ActivationFiberLengthMuscle::getStateVariableDeriv	(	const SimTK::State &	s,
		int	aIndex
	)			const [protected, virtual]

Get the derivative of an actuator state, by index.

Parameters:

aIndex

the index of the state to get.

Returns:

The value of the state.

string ActivationFiberLengthMuscle::getStateVariableName

(

int

aIndex

)

const [protected, virtual]

Get the name of a state variable, given its index.

Parameters:

aIndex

The index of the state variable to get.

Returns:

The name of the state variable.

Reimplemented from OpenSim::ModelComponent.

double ActivationFiberLengthMuscle::getStress

(

const SimTK::State &

s

)

const [virtual]

Get the stress in this actuator.

It is calculated as the force divided by the maximum isometric force (which is proportional to its area).

Reimplemented from OpenSim::PathActuator.

Reimplemented in OpenSim::ContDerivMuscle.

double ActivationFiberLengthMuscle::getTendonForce

(

const SimTK::State &

s

)

const [virtual]

Implements OpenSim::Muscle.

Reimplemented in OpenSim::ContDerivMuscle.

double ActivationFiberLengthMuscle::getTendonLength

(

const SimTK::State &

s

)

const [virtual]

Get the length of the tendon.

Returns:

Current length of the tendon.

Reimplemented from OpenSim::Muscle.

void ActivationFiberLengthMuscle::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::Muscle.

OpenSim::ActivationFiberLengthMuscle::OPENSIM_DECLARE_DERIVED	(	ActivationFiberLengthMuscle	,
		Muscle
	)

ActivationFiberLengthMuscle & ActivationFiberLengthMuscle::operator=

(

const ActivationFiberLengthMuscle &

aMuscle

)

Assignment operator.

Parameters:

aMuscle

The muscle from which to copy its data

Returns:

Reference to this object.

Reimplemented from OpenSim::Muscle.

Reimplemented in OpenSim::ContDerivMuscle, OpenSim::Delp1990Muscle, OpenSim::Schutte1993Muscle, and OpenSim::Thelen2003Muscle.

void ActivationFiberLengthMuscle::postScale	(	const SimTK::State &	s,
		const ScaleSet &	aScaleSet
	)			[protected, virtual]

Perform computations that need to happen after the muscle is scaled.

For this object, that entails updating the muscle path. Derived classes should probably also scale or update some of the force-generating properties.

Parameters:

aScaleSet

XYZ scale factors for the bodies.

Reimplemented from OpenSim::PathActuator.

void ActivationFiberLengthMuscle::setActivation	(	SimTK::State &	s,
		double	activation
	)			const [virtual]

Implements OpenSim::Muscle.

Reimplemented in OpenSim::ContDerivMuscle.

void ActivationFiberLengthMuscle::setActivationDeriv	(	const SimTK::State &	s,
		double	activationDeriv
	)			const [virtual]

Reimplemented in OpenSim::ContDerivMuscle.

void ActivationFiberLengthMuscle::setDefaultActivation

(

double

activation

)

[virtual]

void ActivationFiberLengthMuscle::setDefaultFiberLength

(

double

length

)

[virtual]

void ActivationFiberLengthMuscle::setDefaultsFromState

(

const SimTK::State &

state

)

[protected, virtual]

Set all default values for this object to match those in a specified State.

It must be implemented/overriden to set any default values defined by each subclass.

Parameters:

state

the State from which to take values that should become the defaults for this object

Reimplemented from OpenSim::Muscle.

void ActivationFiberLengthMuscle::setFiberLength	(	SimTK::State &	s,
		double	fiberLength
	)			const [virtual]

Reimplemented in OpenSim::ContDerivMuscle.

void ActivationFiberLengthMuscle::setFiberLengthDeriv	(	const SimTK::State &	s,
		double	fiberLengthDeriv
	)			const [virtual]

Reimplemented in OpenSim::ContDerivMuscle.

void OpenSim::ActivationFiberLengthMuscle::setName

(

const std::string &

aName

)

Reimplemented from OpenSim::Muscle.

void ActivationFiberLengthMuscle::setNumStateVariables

(

int

aNumStateVariables

)

[protected, virtual]

void ActivationFiberLengthMuscle::setPassiveForce	(	const SimTK::State &	s,
		double	aForce
	)			const [virtual]

Reimplemented in OpenSim::ContDerivMuscle.

void ActivationFiberLengthMuscle::setStateVariableDeriv	(	const SimTK::State &	s,
		int	aIndex,
		double	aValue
	)			const [protected, virtual]

Set the derivative of an actuator state, specified by index.

Parameters:

	aIndex	The index of the state to set.
	aValue	The value to set the state to.

void ActivationFiberLengthMuscle::setTendonForce	(	const SimTK::State &	s,
		double	aForce
	)			const [virtual]

Reimplemented in OpenSim::ContDerivMuscle.

void ActivationFiberLengthMuscle::setup

(

Model &

aModel

)

[protected, virtual]

Perform set up functions after model has been deserialized or copied.

Parameters:

aModel

The model containing this muscle.

Reimplemented from OpenSim::Muscle.

Reimplemented in OpenSim::ContDerivMuscle, OpenSim::Delp1990Muscle, OpenSim::Schutte1993Muscle, and OpenSim::Thelen2003Muscle.

void ActivationFiberLengthMuscle::updateFromXMLNode

(

)

[virtual]

Override of the default implementation to account for versioning.

Override default implementation by object to intercept and fix the XML node underneath the model to match current version.

Reimplemented from OpenSim::Muscle.

---

Member Data Documentation

double OpenSim::ActivationFiberLengthMuscle::_defaultActivation [protected]

double OpenSim::ActivationFiberLengthMuscle::_defaultFiberLength [protected]

Array<std::string> OpenSim::ActivationFiberLengthMuscle::_stateVariableSuffixes [protected]

SimTK::ZIndex OpenSim::ActivationFiberLengthMuscle::_zIndex [protected]

const int ActivationFiberLengthMuscle::STATE_ACTIVATION = 0 [static, protected]

Reimplemented in OpenSim::Schutte1993Muscle, and OpenSim::Thelen2003Muscle.

const int ActivationFiberLengthMuscle::STATE_FIBER_LENGTH = 1 [static, protected]

Reimplemented in OpenSim::Schutte1993Muscle, and OpenSim::Thelen2003Muscle.

---

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

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