This class implements a 3 state (activation,fiber length and fiber velocity) acceleration musculo-tendon model that has several advantages over equilibrium musculo-tendon models: it is possible to simulate 0 activation, it requires fewer integrator steps to simulate, and physiological active force-length (with a minimum value of 0) and force velocity (with true asymptotes at the maximum shortening and lengthening velocites) curves can be employed. More...

Inheritance diagram for OpenSim::Millard2012AccelerationMuscle:

Public Member Functions
	Millard2012AccelerationMuscle ()
	Default constructor: produces a non-functional empty muscle. More...

	Millard2012AccelerationMuscle (const std::string &aName, double aMaxIsometricForce, double aOptimalFiberLength, double aTendonSlackLength, double aPennationAngle)
	Constructs a functional muscle using all of the default curves and activation model. More...

double	getFiberCompressiveForceLengthMultiplier (SimTK::State &s) const

double	getFiberCompressiveForceCosPennationMultiplier (SimTK::State &s) const

double	getTendonForceMultiplier (SimTK::State &s) const

double	getMass () const

const MuscleFirstOrderActivationDynamicModel &	getActivationModel () const

const MuscleFixedWidthPennationModel &	getPennationModel () const

const ActiveForceLengthCurve &	getActiveForceLengthCurve () const

const ForceVelocityCurve &	getForceVelocityCurve () const

const FiberForceLengthCurve &	getFiberForceLengthCurve () const

const TendonForceLengthCurve &	getTendonForceLengthCurve () const

const FiberCompressiveForceLengthCurve &	getFiberCompressiveForceLengthCurve () const

const FiberCompressiveForceCosPennationCurve &	getFiberCompressiveForceCosPennationCurve () const

double	getFiberStiffnessAlongTendon (const SimTK::State &s) const

void	setActivationModel (MuscleFirstOrderActivationDynamicModel &aActivationMdl)

void	setActiveForceLengthCurve (ActiveForceLengthCurve &aActiveForceLengthCurve)

void	setForceVelocityCurve (ForceVelocityCurve &aForceVelocityCurve)

void	setFiberForceLengthCurve (FiberForceLengthCurve &aFiberForceLengthCurve)

void	setTendonForceLengthCurve (TendonForceLengthCurve &aTendonForceLengthCurve)

void	setFiberCompressiveForceLengthCurve (FiberCompressiveForceLengthCurve &aFiberCompressiveForceLengthCurve)

void	setFiberCompressiveForceCosPennationCurve (FiberCompressiveForceCosPennationCurve &aFiberCompressiveForceCosPennationCurve)

void	setMass (double mass)

double	getDefaultActivation () const

double	getDefaultFiberLength () const

double	getDefaultFiberVelocity () const

double	getActivationRate (const SimTK::State &s) const

double	getFiberVelocity (const SimTK::State &s) const

double	getFiberAcceleration (const SimTK::State &s) const

void	setDefaultActivation (double activation)

void	setDefaultFiberLength (double fiberLength)

void	setDefaultFiberVelocity (double fiberVelocity)

void	setActivation (SimTK::State &s, double activation) const

void	setFiberLength (SimTK::State &s, double fiberLength) const

void	setFiberVelocity (SimTK::State &s, double fiberVelocity) const

Array< std::string >	getStateVariableNames () const final

SimTK::SystemYIndex	getStateVariableSystemIndex (const std::string &stateVariableName) const final

double	computeActuation (const SimTK::State &s) const final

void	computeInitialFiberEquilibrium (SimTK::State &s) const final
	This function computes the fiber length such that muscle fiber and tendon are developing the same force, and so that the velocity of the entire muscle-tendon is spread between the fiber and the tendon according to their relative compliances. More...

Property declarations
These are the serializable properties associated with this class.
	OpenSim_DECLARE_PROPERTY (default_activation, double,"assumed initial activation level if none is assigned.")

	OpenSim_DECLARE_PROPERTY (default_fiber_length, double,"assumed initial fiber length if none is assigned.")

	OpenSim_DECLARE_PROPERTY (default_fiber_velocity, double,"assumed initial fiber velocity if none is assigned.")

	OpenSim_DECLARE_UNNAMED_PROPERTY (MuscleFirstOrderActivationDynamicModel,"activation dynamics model with a lower bound")

	OpenSim_DECLARE_UNNAMED_PROPERTY (ActiveForceLengthCurve,"active force length curve")

	OpenSim_DECLARE_UNNAMED_PROPERTY (ForceVelocityCurve,"force velocity curve")

	OpenSim_DECLARE_UNNAMED_PROPERTY (FiberForceLengthCurve,"fiber force length curve")

	OpenSim_DECLARE_UNNAMED_PROPERTY (TendonForceLengthCurve,"Tendon force length curve")

	OpenSim_DECLARE_UNNAMED_PROPERTY (FiberCompressiveForceLengthCurve,"fiber compressive force length curve")

	OpenSim_DECLARE_UNNAMED_PROPERTY (FiberCompressiveForceCosPennationCurve,"fiber compressive force cos(pennationAngle) curve")

	OpenSim_DECLARE_PROPERTY (fiber_damping, double,"fiber damping coefficient")

	OpenSim_DECLARE_PROPERTY (fiber_force_length_damping, double,"fiber force length damping coefficient")

	OpenSim_DECLARE_PROPERTY (fiber_compressive_force_length_damping, double,"fiber compressive force length damping coefficient")

	OpenSim_DECLARE_PROPERTY (fiber_compressive_force_cos_pennation_damping, double,"fiber compressive force cos(pennationAngle) damping coefficient")

	OpenSim_DECLARE_PROPERTY (tendon_force_length_damping, double,"tendon force length damping coefficient")

	OpenSim_DECLARE_PROPERTY (mass, double,"lumped mass")

Public Member Functions inherited from OpenSim::Muscle
	OpenSim_DECLARE_PROPERTY (max_isometric_force, double,"Maximum isometric force that the fibers can generate")

	OpenSim_DECLARE_PROPERTY (optimal_fiber_length, double,"Optimal length of the muscle fibers")

	OpenSim_DECLARE_PROPERTY (tendon_slack_length, double,"Resting length of the tendon")

	OpenSim_DECLARE_PROPERTY (pennation_angle_at_optimal, double,"Angle between tendon and fibers at optimal fiber length expressed in radians")

	OpenSim_DECLARE_PROPERTY (max_contraction_velocity, double,"Maximum contraction velocity of the fibers, in optimal fiberlengths/second")

	OpenSim_DECLARE_PROPERTY (ignore_tendon_compliance, bool,"Compute muscle dynamics ignoring tendon compliance. Tendon is assumed to be rigid.")

	OpenSim_DECLARE_PROPERTY (ignore_activation_dynamics, bool,"Compute muscle dynamics ignoring activation dynamics. Activation is equivalent to excitation.")

	Muscle ()
	Default constructor. More...

double	getMaxIsometricForce () const
	get/set the maximum isometric force (in N) that the fibers can generate More...

void	setMaxIsometricForce (double maxIsometricForce)

double	getOptimalFiberLength () const
	get/set the optimal length (in m) of the muscle fibers (lumped as a single fiber) More...

void	setOptimalFiberLength (double optimalFiberLength)

double	getTendonSlackLength () const
	get/set the resting (slack) length (in m) of the tendon that is in series with the muscle fiber More...

void	setTendonSlackLength (double tendonSlackLength)

double	getPennationAngleAtOptimalFiberLength () const
	get/set the angle (in radians) between fibers at their optimal fiber length and the tendon More...

void	setPennationAngleAtOptimalFiberLength (double pennationAngle)

double	getMaxContractionVelocity () const
	get/set the maximum contraction velocity of the fibers, in optimal fiber-lengths per second More...

void	setMaxContractionVelocity (double maxContractionVelocity)

bool	getIgnoreTendonCompliance (const SimTK::State &s) const
	Get/set Modeling (runtime) option to ignore tendon compliance when computing muscle dynamics. More...

void	setIgnoreTendonCompliance (SimTK::State &s, bool ignore) const

bool	getIgnoreActivationDynamics (const SimTK::State &s) const
	Get/set Modeling (runtime) option to ignore activation dynamics when computing muscle dynamics. More...

void	setIgnoreActivationDynamics (SimTK::State &s, bool ignore) const

virtual double	getActivation (const SimTK::State &s) const
	get the activation level of the muscle, which modulates the active force of the muscle and has a normalized (0 to 1) value Note: method remains virtual to permit override by deprecated muscles. More...

double	getFiberLength (const SimTK::State &s) const
	get the current working fiber length (m) for the muscle More...

double	getPennationAngle (const SimTK::State &s) const
	get the current pennation angle (radians) between the fiber and tendon at the current fiber length More...

double	getCosPennationAngle (const SimTK::State &s) const
	get the cosine of the current pennation angle (radians) between the fiber and tendon at the current fiber length More...

double	getTendonLength (const SimTK::State &s) const
	get the current tendon length (m) given the current joint angles and fiber length More...

double	getNormalizedFiberLength (const SimTK::State &s) const
	get the current normalized fiber length (fiber_length/optimal_fiber_length) More...

double	getFiberLengthAlongTendon (const SimTK::State &s) const
	get the current fiber length (m) projected (*cos(pennationAngle)) onto the tendon direction More...

double	getTendonStrain (const SimTK::State &s) const
	get the current tendon strain (delta_l/tendon_slack_length is dimensionless) More...

double	getFiberPotentialEnergy (const SimTK::State &s) const
	the potential energy (J) stored in the fiber due to its parallel elastic element More...

double	getTendonPotentialEnergy (const SimTK::State &s) const
	the potential energy (J) stored in the tendon More...

double	getMusclePotentialEnergy (const SimTK::State &s) const
	the total potential energy (J) stored in the muscle More...

double	getPassiveForceMultiplier (const SimTK::State &s) const
	get the passive fiber (parallel elastic element) force multiplier More...

double	getActiveForceLengthMultiplier (const SimTK::State &s) const
	get the active fiber (contractile element) force multiplier due to current fiber length More...

double	getFiberVelocity (const SimTK::State &s) const
	get current fiber velocity (m/s) positive is lengthening More...

double	getNormalizedFiberVelocity (const SimTK::State &s) const
	get normalize fiber velocity (fiber_lengths/s / max_contraction_velocity) More...

double	getFiberVelocityAlongTendon (const SimTK::State &s) const
	get the current afiber velocity (m/s) projected onto the tendon direction More...

double	getPennationAngularVelocity (const SimTK::State &s) const
	get pennation angular velocity (radians/s) More...

double	getTendonVelocity (const SimTK::State &s) const
	get the tendon velocity (m/s) positive is lengthening More...

double	getForceVelocityMultiplier (const SimTK::State &s) const
	get the dimensionless multiplier resulting from the fiber's force-velocity curve More...

double	getFiberForce (const SimTK::State &s) const
	get the current fiber force (N) applied to the tendon More...

double	getFiberForceAlongTendon (const SimTK::State &s) const
	get the force of the fiber (N/m) along the direction of the tendon More...

double	getActiveFiberForce (const SimTK::State &s) const
	get the current active fiber force (N) due to activationforce_lengthforce_velocity relationships More...

double	getPassiveFiberForce (const SimTK::State &s) const
	get the current passive fiber force (N) passive_force_length relationship More...

double	getActiveFiberForceAlongTendon (const SimTK::State &s) const
	get the current active fiber force (N) projected onto the tendon direction More...

double	getPassiveFiberForceAlongTendon (const SimTK::State &s) const
	get the current passive fiber force (N) projected onto the tendon direction More...

double	getTendonForce (const SimTK::State &s) const
	get the current tendon force (N) applied to bones More...

double	getFiberStiffness (const SimTK::State &s) const
	get the current fiber stiffness (N/m) defined as the partial derivative of fiber force w.r.t. More...

double	getFiberStiffnessAlongTendon (const SimTK::State &s) const
	get the stiffness of the fiber (N/m) along the direction of the tendon, that is the partial derivative of the fiber force along the tendon with respect to small changes in fiber length along the tendon More...

double	getTendonStiffness (const SimTK::State &s) const
	get the current tendon stiffness (N/m) defined as the partial derivative of tendon force w.r.t. More...

double	getMuscleStiffness (const SimTK::State &s) const
	get the current muscle stiffness (N/m) defined as the partial derivative of muscle force w.r.t. More...

double	getFiberActivePower (const SimTK::State &s) const
	get the current active fiber power (W) More...

double	getFiberPassivePower (const SimTK::State &s) const
	get the current passive fiber power (W) More...

double	getTendonPower (const SimTK::State &s) const
	get the current tendon power (W) More...

double	getMusclePower (const SimTK::State &s) const
	get the current muscle power (W) More...

double	getStress (const SimTK::State &s) const
	get the stress in the muscle (part of the Actuator interface as well) More...

void	setExcitation (SimTK::State &s, double excitation) const
	set the excitation (control) for this muscle. More...

double	getExcitation (const SimTK::State &s) const

void	equilibrate (SimTK::State &s) const
	Find and set the equilibrium state of the muscle (if any) More...

Public Member Functions inherited from OpenSim::PathActuator
	PathActuator ()

GeometryPath &	updGeometryPath ()

const GeometryPath &	getGeometryPath () const

virtual bool	hasGeometryPath () const
	Return a flag indicating whether the Force is applied along a Path. More...

void	setOptimalForce (double aOptimalForce)

double	getOptimalForce () const

virtual double	getLength (const SimTK::State &s) const

virtual double	getLengtheningSpeed (const SimTK::State &s) const

virtual double	getPower (const SimTK::State &s) const

void	addNewPathPoint (const std::string &proposedName, OpenSim::Body &aBody, const SimTK::Vec3 &aPositionOnBody)
	Note that this function does not maintain the State and so should be used only before a valid State is created. More...

virtual double	computeMomentArm (const SimTK::State &s, Coordinate &aCoord) const

virtual void	preScale (const SimTK::State &s, const ScaleSet &aScaleSet)

virtual void	scale (const SimTK::State &s, const ScaleSet &aScaleSet)

virtual const VisibleObject *	getDisplayer () const
	Methods to support making the object displayable in the GUI or Visualizer Implemented only in few objects. More...

virtual void	updateDisplayer (const SimTK::State &s) const
	In case the ModelComponent has a visual representation (VisualObject), override this method to update it. More...

	OpenSim_DECLARE_UNNAMED_PROPERTY (GeometryPath,"The set of points defining the path of the muscle.")

	OpenSim_DECLARE_PROPERTY (optimal_force, double,"The maximum force this actuator can produce.")

Public Member Functions inherited from OpenSim::Actuator
	Actuator ()

virtual double	getControl (const SimTK::State &s) const
	Convenience method to set controls given scalar (double) valued control. More...

virtual int	numControls () const

virtual void	setForce (const SimTK::State &s, double aForce) const

virtual double	getForce (const SimTK::State &s) const

virtual void	setSpeed (const SimTK::State &s, double aspeed) const

virtual double	getSpeed (const SimTK::State &s) const

void	setMinControl (const double &aMinControl)

double	getMinControl () const

void	setMaxControl (const double &aMaxControl)

double	getMaxControl () const

void	overrideForce (SimTK::State &s, bool flag) const
	Enable/disable an Actuator's override force. More...

bool	isForceOverriden (const SimTK::State &s) const
	return Actuator's override status More...

void	setOverrideForce (SimTK::State &s, double value) const
	set the force value used when the override is true More...

double	getOverrideForce (const SimTK::State &s) const
	return override force More...

	OpenSim_DECLARE_PROPERTY (min_control, double,"Minimum allowed value for control signal. Used primarily when solving ""for control values.")
	Default is -Infinity (no limit). More...

	OpenSim_DECLARE_PROPERTY (max_control, double,"Maximum allowed value for control signal. Used primarily when solving ""for control values.")
	Default is Infinity (no limit). More...

Public Member Functions inherited from OpenSim::Actuator_
	Actuator_ ()

virtual const SimTK::Vector	getDefaultControls ()
	Actuator default controls are zero. More...

virtual const SimTK::VectorView_< double >	getControls (const SimTK::State &s) const

virtual void	getControls (const SimTK::Vector &modelControls, SimTK::Vector &actuatorControls) const
	Convenience methods for getting, setting and adding to actuator controls from/into the model controls. More...

virtual void	setControls (const SimTK::Vector &actuatorControls, SimTK::Vector &modelControls) const
	set actuator controls subvector into the right slot in the system-wide model controls More...

virtual void	addInControls (const SimTK::Vector &actuatorControls, SimTK::Vector &modelControls) const
	add actuator controls to the values already occupying the slot in the system-wide model controls More...

virtual void	computeEquilibrium (SimTK::State &s) const

Public Member Functions inherited from OpenSim::Force
	Force (const Force &aForce)
	Implements a copy constructor just so it can invalidate the SimTK::Force index after copying. More...

Force &	operator= (const Force &aForce)
	Implements a copy assignment operator just so it can invalidate the SimTK::Force index after the assignment. More...

bool	isDisabled (const SimTK::State &s) const
	Return if the Force is disabled or not. More...

void	setDisabled (SimTK::State &s, bool disabled) const
	Set the Force as disabled (true) or not (false). More...

	OpenSim_DECLARE_PROPERTY (isDisabled, bool,"Flag indicating whether the force is disabled or not. Disabled means"" that the force is not active in subsequent dynamics realizations.")
	A Force element is active (enabled) by default. More...

Public Member Functions inherited from OpenSim::ModelComponent
	ModelComponent ()
	Default constructor. More...

	ModelComponent (const std::string &aFileName, bool aUpdateFromXMLNode=true) SWIG_DECLARE_EXCEPTION
	Construct ModelComponent from an XML file. More...

	ModelComponent (SimTK::Xml::Element &aNode)
	Construct ModelComponent from a specific node in an XML document. More...

	ModelComponent (const ModelComponent &source)
	Construct ModelComponent with its contents copied from another ModelComponent; this is a deep copy so nothing is shared with the source after the copy. More...

virtual	~ModelComponent ()
	Destructor is virtual to allow concrete model component cleanup. More...

ModelComponent &	operator= (const ModelComponent &aModelComponent)
	Assignment operator to copy contents of an existing component. More...

const Model &	getModel () const
	Get a const reference to the Model this component is part of. More...

Model &	updModel ()
	Get a modifiable reference to the Model this component is part of. More...

virtual int	getNumStateVariables () const
	Get the number of "Continuous" state variables maintained by the ModelComponent and its specified subcomponents. More...

int	getModelingOption (const SimTK::State &state, const std::string &name) const
	Get a ModelingOption flag for this ModelComponent by name. More...

void	setModelingOption (SimTK::State &state, const std::string &name, int flag) const
	Set the value of a ModelingOption flag for this ModelComponent. More...

double	getStateVariable (const SimTK::State &state, const std::string &name) const
	Get the value of a state variable allocated by this ModelComponent. More...

void	setStateVariable (SimTK::State &state, const std::string &name, double value) const
	Set the value of a state variable allocated by this ModelComponent by name. More...

double	getDiscreteVariable (const SimTK::State &state, const std::string &name) const
	Get the value of a discrete variable allocated by this ModelComponent by name. More...

void	setDiscreteVariable (SimTK::State &state, const std::string &name, double value) const
	Set the value of a discrete variable allocated by this ModelComponent by name. More...

template<typename T >
const T &	getCacheVariable (const SimTK::State &state, const std::string &name) const
	Get the value of a cache variable allocated by this ModelComponent by name. More...

template<typename T >
const T &	getCacheVariable (const SimTK::State &state, SimTK::CacheEntryIndex ceIndex) const

template<typename T >
T &	updCacheVariable (const SimTK::State &state, const std::string &name) const
	Obtain a writable cache variable value allocated by this ModelComponent by name. More...

template<typename T >
T &	updCacheVariable (const SimTK::State &state, SimTK::CacheEntryIndex ceIndex) const

void	markCacheVariableValid (const SimTK::State &state, const std::string &name) const
	After updating a cache variable value allocated by this ModelComponent, you can mark its value as valid, which will not change until the realization stage falls below the minimum set at the time the cache variable was created. More...

void	markCacheVariableValid (const SimTK::State &state, SimTK::CacheEntryIndex ceIndex) const

void	markCacheVariableInvalid (const SimTK::State &state, const std::string &name) const
	Mark a cache variable value allocated by this ModelComponent as invalid. More...

void	markCacheVariableInvalid (const SimTK::State &state, SimTK::CacheEntryIndex ceIndex) const

bool	isCacheVariableValid (const SimTK::State &state, const std::string &name) const
	Enables the to monitor the validity of the cache variable value using the returned flag. More...

bool	isCacheVariableValid (const SimTK::State &state, SimTK::CacheEntryIndex ceIndex) const

template<typename T >
void	setCacheVariable (const SimTK::State &state, const std::string &name, const T &value) const
	Set cache variable value allocated by this ModelComponent by name. More...

template<typename T >
void	setCacheVariable (const SimTK::State &state, SimTK::CacheEntryIndex ceIndex, const T &value) const

Public Member Functions inherited from OpenSim::Object
virtual	~Object ()
	Virtual destructor for cleanup. More...

virtual Object *	clone () const =0
	Create a new heap-allocated copy of the concrete object to which this Object refers. More...

virtual const std::string &	getConcreteClassName () const =0
	Returns the class name of the concrete Object-derived class of the actual object referenced by this Object, as a string. More...

virtual VisibleObject *	updDisplayer ()
	get Non const pointer to VisibleObject More...

bool	isEqualTo (const Object &aObject) const
	Equality operator wrapper for use from languages not supporting operator overloading. More...

Object &	operator= (const Object &aObject)
	Copy assignment copies he base class fields, including the properties. More...

virtual bool	operator== (const Object &aObject) const
	Determine if two objects are equal. More...

virtual bool	operator< (const Object &aObject) const
	Provide an ordering for objects so they can be put in sorted containers. More...

void	setName (const std::string &name)
	Set the name of the Object. More...

const std::string &	getName () const
	Get the name of this Object. More...

void	setDescription (const std::string &description)
	Set description, a one-liner summary. More...

const std::string &	getDescription () const
	Get description, a one-liner summary. More...

const std::string &	getAuthors () const
	Get Authors of this Object. More...

void	setAuthors (const std::string &authors)
	Set Authors of this object, call this method in your constructor if needed. More...

const std::string &	getReferences () const
	Get references or publications to cite if using this object. More...

void	setReferences (const std::string &references)
	Set references or publications to cite if using this object. More...

int	getNumProperties () const
	Determine how many properties are stored with this Object. More...

const AbstractProperty &	getPropertyByIndex (int propertyIndex) const
	Get a const reference to a property by its index number, returned as an AbstractProperty. More...

AbstractProperty &	updPropertyByIndex (int propertyIndex)
	Get a writable reference to a property by its index number, returned as an AbstractProperty. More...

bool	hasProperty (const std::string &name) const
	Return true if this Object has a property of any type with the given name, which must not be empty. More...

const AbstractProperty &	getPropertyByName (const std::string &name) const
	Get a const reference to a property by its name, returned as an AbstractProperty. More...

AbstractProperty &	updPropertyByName (const std::string &name)
	Get a writable reference to a property by its name, returned as an AbstractProperty. More...

template<class T >
bool	hasProperty () const
	Return true if this Object contains an unnamed, one-object property that contains objects of the given template type T. More...

template<class T >
const Property< T > &	getProperty (const PropertyIndex &index) const
	Get property of known type Property<T> as a const reference; the property must be present and have the right type. More...

template<class T >
Property< T > &	updProperty (const PropertyIndex &index)
	Get property of known type Property<T> as a writable reference; the property must be present and have the right type. More...

void	setObjectIsUpToDateWithProperties ()
	When an object is initialized using the current values of its properties, it can set a flag indicating that it is up to date. More...

bool	isObjectUpToDateWithProperties () const
	Returns `true` if no property's value has changed since the last time setObjectIsUpToDateWithProperties() was called. More...

void	readObjectFromXMLNodeOrFile (SimTK::Xml::Element &objectElement, int versionNumber)
	We're given an XML element from which we are to populate this Object. More...

virtual void	updateXMLNode (SimTK::Xml::Element &parent)
	Serialize this object into the XML node that represents it. More...

bool	getInlined () const
	Inlined means an in-memory Object that is not associated with an XMLDocument. More...

void	setInlined (bool aInlined, const std::string &aFileName="")
	Mark this as inlined or not and optionally provide a file name to associate with the new XMLDocument for the non-inline case. More...

std::string	getDocumentFileName () const
	If there is a document associated with this object then return the file name maintained by the document. More...

void	setAllPropertiesUseDefault (bool aUseDefault)

bool	print (const std::string &fileName)
	Write this Object into an XML file of the given name; conventionally the suffix to use is ".osim". More...

std::string	dump (bool dumpName=false)
	dump the XML representation of this Object into an std::string and return it. More...

void	clearObjectIsUpToDateWithProperties ()
	For testing or debugging purposes, manually clear the "object is up to date with respect to properties" flag. More...

virtual bool	isA (const char *type) const
	The default implementation returns true only if the supplied string is "Object"; each Object-derived class overrides this to match its own class name. More...

const std::string &	toString () const
	Wrapper to be used on Java side to display objects in tree; this returns just the object's name. More...

PropertySet &	getPropertySet ()
	OBSOLETE: Get a reference to the PropertySet maintained by the Object. More...

const PropertySet &	getPropertySet () const

Protected Member Functions
void	postScale (const SimTK::State &s, const ScaleSet &aScaleSet)
	Related to scaling, soon to be removed. More...

double	calcActivationRate (const SimTK::State &s) const

void	calcMuscleLengthInfo (const SimTK::State &s, MuscleLengthInfo &mli) const final
	calculate muscle's position related values such fiber and tendon lengths, normalized lengths, pennation angle, etc... More...

virtual void	calcFiberVelocityInfo (const SimTK::State &s, FiberVelocityInfo &fvi) const final
	calculate muscle's velocity related values such fiber and tendon velocities,normalized velocities, pennation angular velocity, etc... More...

void	calcMuscleDynamicsInfo (const SimTK::State &s, MuscleDynamicsInfo &mdi) const final
	calculate muscle's active and passive force-length, force-velocity, tendon force, relationships and their related values More...

void	calcMusclePotentialEnergyInfo (const SimTK::State &s, MusclePotentialEnergyInfo &mpei) const final
	calculate muscle's fiber and tendon potential energy More...

void	connectToModel (Model &model) final
	Sets up the ModelComponent from the model, if necessary. More...

void	addToSystem (SimTK::MultibodySystem &system) const final
	Creates the ModelComponent so that it can be used in simulation. More...

void	initStateFromProperties (SimTK::State &s) const final
	Initializes the state of the ModelComponent. More...

void	setPropertiesFromState (const SimTK::State &s) final
	Sets the default state for ModelComponent. More...

SimTK::Vector	computeStateVariableDerivatives (const SimTK::State &s) const final
	computes state variable derivatives More...

void	setStateVariableDeriv (const SimTK::State &s, const std::string &aStateName, double aValue) const
	Set the derivative of an actuator state, specified by name. More...

double	getStateVariableDeriv (const SimTK::State &s, const std::string &aStateName) const
	Get the derivative of an actuator state, by index. More...

Protected Member Functions inherited from OpenSim::Muscle
const MuscleLengthInfo &	getMuscleLengthInfo (const SimTK::State &s) const
	Developer Access to intermediate values calculate by the muscle model. More...

MuscleLengthInfo &	updMuscleLengthInfo (const SimTK::State &s) const

const FiberVelocityInfo &	getFiberVelocityInfo (const SimTK::State &s) const

FiberVelocityInfo &	updFiberVelocityInfo (const SimTK::State &s) const

const MuscleDynamicsInfo &	getMuscleDynamicsInfo (const SimTK::State &s) const

MuscleDynamicsInfo &	updMuscleDynamicsInfo (const SimTK::State &s) const

const MusclePotentialEnergyInfo &	getMusclePotentialEnergyInfo (const SimTK::State &s) const

MusclePotentialEnergyInfo &	updMusclePotentialEnergyInfo (const SimTK::State &s) const

virtual void	computeFiberEquilibriumAtZeroVelocity (SimTK::State &s) const
	Provide a quick estimate of the fiber length assuming the musculotendon unit velocity is zero. More...

void	computeForce (const SimTK::State &state, SimTK::Vector_< SimTK::SpatialVec > &bodyForces, SimTK::Vector &generalizedForce) const override
	Force interface applies tension to bodies, and Muscle also checks that applied muscle tension is not negative. More...

double	computePotentialEnergy (const SimTK::State &state) const override
	Potential energy stored by the muscle. More...

SimTK::Vec3	computePathColor (const SimTK::State &state) const override
	Override PathActuator virtual to calculate a preferred color for the muscle path based on activation. More...

void	connectToModel (Model &aModel) override
	Model Component creation interface. More...

void	addToSystem (SimTK::MultibodySystem &system) const override
	Default is to create a ForceAdapter which is a SimTK::Force::Custom as the underlying computational component. More...

void	realizeTopology (SimTK::State &state) const override
	Obtain state resources that are needed unconditionally, and perform computations that depend only on the system topology. More...

void	setPropertiesFromState (const SimTK::State &s) override
	Subclass should override; be sure to invoke Force::setPropertiesFromState() at the beginning of the overriding method. More...

void	initStateFromProperties (SimTK::State &state) const override
	Subclass should override; be sure to invoke Force::initStateFromProperties() at the beginning of the overriding method. More...

virtual void	updateGeometry (const SimTK::State &s)

Protected Member Functions inherited from OpenSim::PathActuator
void	connectToModel (Model &aModel) override
	Extension of parent class method; derived classes may extend further. More...

void	realizeDynamics (const SimTK::State &state) const override
	Extension of parent class method; derived classes may extend further. More...

Protected Member Functions inherited from OpenSim::Actuator
double	computeOverrideForce (const SimTK::State &s) const

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() More...

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. More...

Protected Member Functions inherited from OpenSim::Actuator_
virtual void	updateGeometry ()

Protected Member Functions inherited from OpenSim::Force
	Force ()
	Default constructor sets up Force-level properties; can only be called from a derived class constructor. More...

	Force (SimTK::Xml::Element &node)
	Deserialization from XML, necessary so that derived classes can (de)serialize. More...

void	applyForceToPoint (const SimTK::State &state, const OpenSim::Body &body, const SimTK::Vec3 &point, const SimTK::Vec3 &force, SimTK::Vector_< SimTK::SpatialVec > &bodyForces) const
	Apply a force at a particular point (a "station") on a given body. More...

void	applyTorque (const SimTK::State &state, const OpenSim::Body &body, const SimTK::Vec3 &torque, SimTK::Vector_< SimTK::SpatialVec > &bodyForces) const
	Apply a torque to a particular body. More...

void	applyGeneralizedForce (const SimTK::State &state, const Coordinate &coord, double force, SimTK::Vector &generalizedForces) const
	Apply a generalized force. More...

Protected Member Functions inherited from OpenSim::ModelComponent
virtual void	generateDecorations (bool fixed, const ModelDisplayHints &hints, const SimTK::State &state, SimTK::Array_< SimTK::DecorativeGeometry > &appendToThis) const
	Optional method for generating arbitrary display geometry that reflects this ModelComponent at the specified state. More...

virtual void	realizeModel (SimTK::State &state) const
	Obtain state resources that may be needed, depending on modeling options, and perform computations that depend only on topology and selected modeling options. More...

virtual void	realizeInstance (const SimTK::State &state) const
	Perform computations that depend only on instance variables, like lengths and masses. More...

virtual void	realizeTime (const SimTK::State &state) const
	Perform computations that depend only on time and earlier stages. More...

virtual void	realizePosition (const SimTK::State &state) const
	Perform computations that depend only on position-level state variables and computations performed in earlier stages (including time). More...

virtual void	realizeVelocity (const SimTK::State &state) const
	Perform computations that depend only on velocity-level state variables and computations performed in earlier stages (including position, and time). More...

virtual void	realizeAcceleration (const SimTK::State &state) const
	Perform computations that may depend on applied forces. More...

virtual void	realizeReport (const SimTK::State &state) const
	Perform computations that may depend on anything but are only used for reporting and cannot affect subsequent simulation behavior. More...

void	includeAsSubComponent (ModelComponent *aComponent)
	Include another ModelComponent as a Subcomponent of this ModelComponent. More...

void	addModelingOption (const std::string &optionName, int maxFlagValue) const
	Add a modeling option (integer flag stored in the State) for use by this ModelComponent. More...

void	addStateVariable (const std::string &stateVariableName, SimTK::Stage invalidatesStage=SimTK::Stage::Dynamics) const
	Add a continuous system state variable belonging to this ModelComponent, and assign a name by which to refer to it. More...

void	addDiscreteVariable (const std::string &discreteVariableName, SimTK::Stage invalidatesStage) const
	Add a system discrete variable belonging to this ModelComponent, give it a name by which it can be referenced, and declare the lowest Stage that should be invalidated if this variable's value is changed. More...

template<class T >
void	addCacheVariable (const std::string &cacheVariableName, const T &variablePrototype, SimTK::Stage dependsOnStage) const
	Add a state cache entry belonging to this ModelComponent to hold calculated values that must be automatically invalidated when certain state values change. More...

const int	getStateIndex (const std::string &name) const
	Get the index of a ModelComponent's continuous state variable in the Subsystem for allocations. More...

const SimTK::DiscreteVariableIndex	getDiscreteVariableIndex (const std::string &name) const
	Get the index of a ModelComponent's discrete variable in the Subsystem for allocations. More...

const SimTK::CacheEntryIndex	getCacheVariableIndex (const std::string &name) const
	Get the index of a ModelComponent's cache variable in the Subsystem for allocations. More...

Protected Member Functions inherited from OpenSim::Object
	Object ()
	The default constructor is only for use by constructors of derived types. More...

	Object (const std::string &fileName, bool aUpdateFromXMLNode=true) SWIG_DECLARE_EXCEPTION
	Constructor from a file, to be called from other constructors that take a file as input. More...

	Object (const Object &source)
	Copy constructor is invoked automatically by derived classes with default copy constructors; otherwise it must be invoked explicitly. More...

	Object (SimTK::Xml::Element &aElement)
	Construct the base class portion of an Object from a given Xml element that describes this Object. More...

template<class T >
PropertyIndex	addProperty (const std::string &name, const std::string &comment, const T &value)
	Define a new single-value property of known type T, with the given name, associated comment, and initial value. More...

template<class T >
PropertyIndex	addOptionalProperty (const std::string &name, const std::string &comment)
	Add an optional property, meaning it can contain either no value or a single value. More...

template<class T >
PropertyIndex	addOptionalProperty (const std::string &name, const std::string &comment, const T &value)
	Add an optional property, meaning it can contain either no value or a single value. More...

template<class T >
PropertyIndex	addListProperty (const std::string &name, const std::string &comment, int minSize, int maxSize)
	Define a new list-valued property of known type T, with the given name, associated comment, minimum (==0) and maximum (>0) allowable list lengths, and a zero-length initial value. More...

template<class T , template< class > class Container>
PropertyIndex	addListProperty (const std::string &name, const std::string &comment, int minSize, int maxSize, const Container< T > &valueList)
	Define a new list-valued property as above, but assigning an initial value via some templatized container class that supports size() and indexing. More...

PropertyIndex	getPropertyIndex (const std::string &name) const
	Look up a property by name and return its PropertyIndex if it is found. More...

template<class T >
PropertyIndex	getPropertyIndex () const
	Look up an unnamed property by the type of object it contains, and return its PropertyIndex if it is found. More...

void	updateFromXMLDocument ()
	Use this method only if you're deserializing from a file and the object is at the top level; that is, primarily in constructors that take a file name as input. More...

void	setDocument (XMLDocument *doc)
	Unconditionally set the XMLDocument associated with this object. More...

const XMLDocument *	getDocument () const
	Get a const pointer to the document (if any) associated with this object. More...

XMLDocument *	updDocument ()
	Get a writable pointer to the document (if any) associated with this object. More...

Additional Inherited Members
Static Public Member Functions inherited from OpenSim::Object
static void	registerType (const Object &defaultObject)
	Register an instance of a class; if the class is already registered it will be replaced. More...

static void	renameType (const std::string &oldTypeName, const std::string &newTypeName)
	Support versioning by associating the current Object type with an old name. More...

static const Object *	getDefaultInstanceOfType (const std::string &concreteClassName)
	Return a pointer to the default instance of the registered (concrete) Object whose class name is given, or NULL if the type is not registered. More...

template<class T >
static bool	isObjectTypeDerivedFrom (const std::string &concreteClassName)
	Return true if the given concrete object type represents a subclass of the template object type T, and thus could be referenced with a T*. More...

static Object *	newInstanceOfType (const std::string &concreteClassName)
	Create a new instance of the concrete Object type whose class name is given as concreteClassName. More...

static void	getRegisteredTypenames (Array< std::string > &typeNames)
	Retrieve all the typenames registered so far. More...

template<class T >
static void	getRegisteredObjectsOfGivenType (ArrayPtrs< T > &rArray)
	Return an array of pointers to the default instances of all registered (concrete) Object types that derive from a given Object-derived type that does not have to be concrete. More...

static void	PrintPropertyInfo (std::ostream &os, const std::string &classNameDotPropertyName)
	Dump formatted property information to a given output stream, useful for creating a "help" facility for registered objects. More...

static void	PrintPropertyInfo (std::ostream &os, const std::string &className, const std::string &propertyName)
	Same as the other signature but the class name and property name are provided as two separate strings. More...

static Object *	makeObjectFromFile (const std::string &fileName)
	Create an OpenSim object whose type is based on the tag at the root node of the XML file passed in. More...

static const std::string &	getClassName ()
	Return the name of this class as a string; i.e., "Object". More...

static void	setSerializeAllDefaults (bool shouldSerializeDefaults)
	Static function to control whether all registered objects and their properties are written to the defaults section of output files rather than only those values for which the default was explicitly overwritten when read in from an input file or set programmatically. More...

static bool	getSerializeAllDefaults ()
	Report the value of the "serialize all defaults" flag. More...

static bool	isKindOf (const char *type)
	Returns true if the passed-in string is "Object"; each Object-derived class defines a method of this name for its own class name. More...

static void	setDebugLevel (int newLevel)
	Set the debug level to get verbose output. More...

static int	getDebugLevel ()
	Get current setting of debug level. More...

static Object *	SafeCopy (const Object *aObject)
	Use the clone() method to duplicate the given object unless the pointer is null in which case null is returned. More...

static void	RegisterType (const Object &defaultObject)
	OBSOLETE alternate name for registerType(). More...

static void	RenameType (const std::string &oldName, const std::string &newName)
	OBSOLETE alternate name for renameType(). More...

Static Public Attributes inherited from OpenSim::Object
static const std::string	DEFAULT_NAME
	Name used for default objects when they are serialized. More...

Protected Attributes inherited from OpenSim::Muscle
double	_muscleWidth
	The assumed fixed muscle-width from which the fiber pennation angle can be calculated. More...

double	_maxIsometricForce
	to support deprecated muscles More...

double	_optimalFiberLength

double	_pennationAngleAtOptimal

double	_tendonSlackLength

Protected Attributes inherited from OpenSim::Actuator_
int	_controlIndex

Protected Attributes inherited from OpenSim::Force
SimTK::ForceIndex	_index
	ID for the force in Simbody. More...

Protected Attributes inherited from OpenSim::ModelComponent
Model *	_model
	The model this component belongs to. More...

Protected Attributes inherited from OpenSim::Object
PropertySet	_propertySet
	OBSOLETE: Property_Deprecated set for serializable member variables of this and derived classes. More...

Related Functions inherited from OpenSim::Object
#define	OpenSim_DECLARE_CONCRETE_OBJECT(ConcreteClass, SuperClass)
	Macro to be included as the first line of the class declaration for any non-templatized, concrete class that derives from OpenSim::Object. More...

#define	OpenSim_DECLARE_ABSTRACT_OBJECT(ConcreteClass, SuperClass)
	Macro to be included as the first line of the class declaration for any still-abstract class that derives from OpenSim::Object. More...

#define	OpenSim_DECLARE_CONCRETE_OBJECT_T(ConcreteClass, TArg, SuperClass)
	Macro to be included as the first line of the class declaration for any templatized, concrete class that derives from OpenSim::Object, like Set<T>. More...

#define	OpenSim_DECLARE_ABSTRACT_OBJECT_T(ConcreteClass, TArg, SuperClass)
	Macro to be included as the first line of the class declaration for any templatized, still-abstract class that derives from OpenSim::Object. More...

Detailed Description

This class implements a 3 state (activation,fiber length and fiber velocity) acceleration musculo-tendon model that has several advantages over equilibrium musculo-tendon models: it is possible to simulate 0 activation, it requires fewer integrator steps to simulate, and physiological active force-length (with a minimum value of 0) and force velocity (with true asymptotes at the maximum shortening and lengthening velocites) curves can be employed.

The dynamic equation of the mass, constrained to move in direction $\hat{i}$ is given by the scalar equation:

$m \ddot{x} = F_{SE} - F_{CE} \cdot \hat{i}$

The kinematic expression for the acceleration of the mass, $\ddot{s}$ , expressed in terms of the fiber length, $l_{CE}$ , and pennation angle $\phi$ is

$\ddot{x} = \Big(\ddot{l}_{CE} \cos \phi - 2 \dot{l}_{CE}\dot{\phi}\sin\phi - \dot{\phi}^2 l_{CE} \cos \phi - \ddot{\phi} l_{CE} \sin \phi\Big)$

The kinematic expression for the angular acceleration of the pennation angle can be found by taking the second derivative of the pennation constraint equation

$l_{CE} \sin \phi = h$

which yields

$\ddot{\phi} = -\Big( \ddot{l}_{CE}\sin\phi + 2 \dot{l}_{CE} \dot{\phi} \cos\phi - \dot{\phi}^2 l_{CE} \sin \phi \Big) / \Big( l_{CE} \cos \phi \Big)$

An expression for $\ddot{l}_{CE}$ can be obtained by substituting in the equations $\ddot{\phi}$ into the equation for $\ddot{x}$ and simplifying:

$\ddot{l}_{CE} = \frac{1}{m} \Big( F_{SE} - F_{CE} \cdot \hat{i} \Big) \cos \phi + l_{CE} \dot{\phi}^2$

Notice that the above equation for $\ddot{l}_{CE}$ has no singularities, provided that there are no singularities in $F_{SE}$ and $F_{M}\cdot\hat{i}$ . The force the fiber applies to the tendon (in N), $F_{CE}\cdot\hat{i}$ , is given by (+'ve is tension)

$F_{CE} \cdot \hat{i} = f_{ISO}\Big(\mathbf{a} \mathbf{f}_L(\hat{l}_{CE}) \mathbf{f}_V(\frac{\hat{v}_{CE}}{v_{MAX}}) + \beta_{CE}\hat{v}_{CE} + \mathbf{f}_{PE}(\hat{l}_{CE})(1+\beta_{PE}\hat{v}_{CE}) - \mathbf{f}_K(\hat{l}_{CE})(1-\beta_{K}\hat{v}_{CE}) \Big) \cos \phi - f_{ISO} \Big( \mathbf{f}_{c\phi}(\cos \phi) (1- \beta_{c \phi} \frac{d}{dt}(\frac{l_{CE}\cos\phi}{l_{CE,OPT}\cos\phi_{OPT}})) \Big)$

The force the tendon generates (in N) is given by (+'ve is tension)

$F_{SE} = f_{ISO} \mathbf{f}_{SE}(\hat{l}_{SE})(1+\beta_{SE}\hat{v}_{SE})$

Every elastic element ( $\mathbf{f}_{PE}$ , $\mathbf{f}_{K}$ , $\mathbf{f}_{c\phi}$ , and $\mathbf{f}_{SE}$ ) is accompanied by a non-linear damping element of a form that is identical to the damping found in a Hunt-Crossley contact model. Additionally a linear damping element, $\beta_{CE}\hat{v}_{CE}$ , is located in the fiber as in J.He et al. Damping is necessary to include in this model to prevent the mass from oscillating in a non-physiologic manner. Nonlinear damping Hunt-Crossley damping (where the damping force is scaled by the elastic force) has been chosen because this form of damping doesn't increase the stiffness of the system equations (because it is gradually turned on).

As with the Hunt-Crossley contact model, the force generated by the nonlinear spring and damper saturated so that it is greater than or equal to zero. This saturation is necessary to ensure that tension elements can only generate tensile forces, and that compressive elements only generate compressive forces. Note that the sign conventions have been chosen so that damping forces are generated in the correct direction for each element.

$\begin{eqnarray*} (1+\beta_{PE}\hat{v}_{CE}) > 0 \\ (1-\beta_{K}\hat{v}_{CE}) > 0 \\ (1- \beta_{c \phi} \frac{d}{dt}(\frac{l_{CE}\cos\phi}{l_{CE,OPT}\cos\phi_{OPT}})) > 0 \\ (1+\beta_{SE}\hat{v}_{SE}) > 0 \end{eqnarray*}$

For more information on these new terms please see the doxygen for FiberCompressiveForceLengthCurve, FiberCompressiveForceCosPennationCurve, and MuscleFirstOrderActivationDynamicModel.

Units

m: meters
rad: radians
N: Newtons
kg: kilograms
s: seconds

Usage

Note that this object should be updated through the set methods provided. These set methods will take care of rebuilding the muscle correctly. If you modify the properties directly, the curve will not be rebuilt, and upon calling a function that requires a state an exception will be thrown because the muscle is out of date with its properties.

Note that this muscle does not currently implement the ignore_tendon_compliance flag, nor the ignore_activation_dynamics flag.

Nomenclature

Note that dot notation is used to denote time derivatives (units of $m/s$ and $m/s^2$ in this case), where as the hat symbol (as in $\hat{l}$ , $\hat{v}$ ) is used to denote time derivatives that have been scaled by a characteristic dimension (appear in units of $1/s$ and $1/s^2$ in this case)

: is the mass located at the junction between the fiber and the tendon. This mass should be thought of as a time constant that indicates how quickly this model will converge to the force an equilibrium muscle-tendon model would produce ( )
$\ddot{x}$ : is the acceleration of the mass, in the $\hat{i}$ direction ( )
$F_{SE}$ : is the force developed by the tendon ( )
$F_{CE}\cdot\hat{i}$ : is the force developed by the fiber along the tendon ( )

$l_{CE}$ : Length of the fiber(m)
$l_{CE,OPT}$ : Length the fiber generates maximal isometric force (m)
$\hat{l}_{CE}=l_{CE}/l_{CE,OPT}$ : Normalized length of the fiber (dimensionless)
$\hat{v}_{CE}=\dot{l}_{CE}/l_{CE,OPT}$ : Fiber velocity divided by ( )
$\hat{v}_{MAX}$ : Maximum normalized fiber velocity ( $l_{CE,OPT}/s$ ). This quantity typically ranges between 10 and 15 lengths per second (1/s)

$\phi$ : Pennation angle(rad)
$\phi_{OPT}$ : Pennation angle when the fiber is at its optimal length (rad)

$l_{SE}$ : Length of the series element (tendon) (m)
$l_{SE,R}$ : Resting length of the series element(m)
$\hat{l}_{SE} = l_{SE}/l_{SE,R}$ : Normalized length of the series element (dimensionless)
$\hat{v}_{SE} = \dot{l}_{SE}/l_{SE,R}$ : Normalized velocity of the tendon (1/s)

$f_{ISO}$ : maximum force the muscle can develop statically ( $\hat{v}_{CE}=0$ ) at its optimal length ( $l_{CE,OPT}$ ) and pennation angle ( $\phi_{OPT}$ )

$\mathbf{a}$ : activation (unitless)
$\mathbf{f}_L(\hat{l}_{CE})$ : Active force length multiplier (dimensionless)
$\mathbf{f}_V(\frac{\hat{v}_{CE}}{v_{MAX}})$ : Force velocity multiplier (dimensionless)
$\mathbf{f}_{PE}(\hat{l}_{CE})$ : Passive force length multiplier (dimensionless)
$\mathbf{f}_{K}(\hat{l}_{CE})$ : Fiber compressive force length multiplier (dimensionless)
$\mathbf{f}_{c\phi}(\cos \phi)$ : Fiber compressive cosine pennation multiplier (dimensionless)
$\mathbf{f}_{SE}(\hat{l}_{SE})$ : Series element (tendon) force-length multiplier (dimensionless)

$\beta_{CE}$ : Fiber damping (s)
$\beta_{PE}$ : Fiber parallel element damping coefficient (s)
$\beta_{K}$ : Fiber compressive force length damping coefficient (s)
$\beta_{c \phi}$ : Fiber compressive cosine pennation damping coefficient (s)
$\beta_{SE}$ : Series element (tendon) force length damping coefficient (s)

References

Hunt,K., and Crossley,F. Coefficient of restitution interpreted as damping in v ibroimpact. Transactions of the ASME Journal of Applied Mechanics, 42(E):440445, 1975.

J.He, W.S. Levine, and G.E. Leob."The Modelling of the Neuro-musculo-skeletal Control System of A Cat Hindlimb", Proceedings of the IEEE International Symposium on Intelligent Control, 1988.

Author: Matt Millard

Constructor & Destructor Documentation

OpenSim::Millard2012AccelerationMuscle::Millard2012AccelerationMuscle ( )

Default constructor: produces a non-functional empty muscle.

OpenSim::Millard2012AccelerationMuscle::Millard2012AccelerationMuscle	(	const std::string &	aName,
		double	aMaxIsometricForce,
		double	aOptimalFiberLength,
		double	aTendonSlackLength,
		double	aPennationAngle
	)

Constructs a functional muscle using all of the default curves and activation model.

Parameters

aName	The name of the muscle.
aMaxIsometricForce	The force generated by the muscle when it at its optimal resting length, has a contraction velocity of zero, and is fully activated (Newtons).
aOptimalFiberLength	The optimal length of the muscle fiber (meters).
aTendonSlackLength	The resting length of the tendon (meters).
aPennationAngle	The angle of the fiber relative to the tendon when the fiber is at its optimal resting length (radians).

Member Function Documentation

void OpenSim::Millard2012AccelerationMuscle::addToSystem ( SimTK::MultibodySystem & system ) const

finalprotectedvirtual

Creates the ModelComponent so that it can be used in simulation.

Parameters

system the multibody system

Reimplemented from OpenSim::Actuator.

double OpenSim::Millard2012AccelerationMuscle::calcActivationRate ( const SimTK::State & s ) const

protected

Parameters

s	the state of the model

Returns: the time derivative of activation

virtual void OpenSim::Millard2012AccelerationMuscle::calcFiberVelocityInfo	(	const SimTK::State &	s,
		FiberVelocityInfo &	fvi
	)		const

finalprotectedvirtual

calculate muscle's velocity related values such fiber and tendon velocities,normalized velocities, pennation angular velocity, etc...

Parameters

s	the state of the model
fvi	the fiber velocity info struct that will hold updated information about the muscle that is available at the velocity stage

Reimplemented from OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::calcMuscleDynamicsInfo	(	const SimTK::State &	s,
		MuscleDynamicsInfo &	mdi
	)		const

finalprotectedvirtual

calculate muscle's active and passive force-length, force-velocity, tendon force, relationships and their related values

Parameters

s	the state of the model
mdi	the muscle dynamics info struct that will hold updated information about the muscle that is available at the dynamics stage

Reimplemented from OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::calcMuscleLengthInfo	(	const SimTK::State &	s,
		MuscleLengthInfo &	mli
	)		const

finalprotectedvirtual

calculate muscle's position related values such fiber and tendon lengths, normalized lengths, pennation angle, etc...

Parameters

s	the state of the model
mli	the muscle length info struct that will hold updated information about the muscle that is available at the position stage

Reimplemented from OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::calcMusclePotentialEnergyInfo	(	const SimTK::State &	s,
		MusclePotentialEnergyInfo &	mpei
	)		const

finalprotectedvirtual

calculate muscle's fiber and tendon potential energy

Reimplemented from OpenSim::Muscle.

double OpenSim::Millard2012AccelerationMuscle::computeActuation ( const SimTK::State & s ) const

finalvirtual

Parameters

s	the state of the system

Returns: the tensile force the muscle is generating in N

Implements OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::computeInitialFiberEquilibrium ( SimTK::State & s ) const

finalvirtual

This function computes the fiber length such that muscle fiber and tendon are developing the same force, and so that the velocity of the entire muscle-tendon is spread between the fiber and the tendon according to their relative compliances.

Parameters

s	the state of the system

Implements OpenSim::Muscle.

SimTK::Vector OpenSim::Millard2012AccelerationMuscle::computeStateVariableDerivatives ( const SimTK::State & s ) const

finalprotectedvirtual

computes state variable derivatives

Parameters

s	the state of the model

Reimplemented from OpenSim::ModelComponent.

void OpenSim::Millard2012AccelerationMuscle::connectToModel ( Model & model )

finalprotectedvirtual

Sets up the ModelComponent from the model, if necessary.

Parameters

model the dynamic model

Reimplemented from OpenSim::ModelComponent.

const MuscleFirstOrderActivationDynamicModel& OpenSim::Millard2012AccelerationMuscle::getActivationModel ( ) const

Returns: the MuscleFirstOrderActivationDynamicModel that this muscle model uses

double OpenSim::Millard2012AccelerationMuscle::getActivationRate ( const SimTK::State & s ) const

Parameters

s	The state of the system

Returns: the time derivative of activation

const ActiveForceLengthCurve& OpenSim::Millard2012AccelerationMuscle::getActiveForceLengthCurve ( ) const

Returns: the ActiveForceLengthCurve that this muscle model uses

double OpenSim::Millard2012AccelerationMuscle::getDefaultActivation ( ) const

Returns: the default activation level that is used as an initial condition if none is provided by the user.

double OpenSim::Millard2012AccelerationMuscle::getDefaultFiberLength ( ) const

Returns: the default fiber length that is used as an initial condition if none is provided by the user.

double OpenSim::Millard2012AccelerationMuscle::getDefaultFiberVelocity ( ) const

Returns: the default fiber velocity that is used as an initial condition if none is provided by the user.

double OpenSim::Millard2012AccelerationMuscle::getFiberAcceleration ( const SimTK::State & s ) const

Parameters

s	The state of the system

Returns: the acceleration of the fiber (m/s)

const FiberCompressiveForceCosPennationCurve& OpenSim::Millard2012AccelerationMuscle::getFiberCompressiveForceCosPennationCurve ( ) const

Returns: the FiberCompressiveForceCosPennationCurve that this muscle model uses.

double OpenSim::Millard2012AccelerationMuscle::getFiberCompressiveForceCosPennationMultiplier ( SimTK::State & s ) const

Parameters

s	the state of the system

Returns: the normalized force term associated with the compressive force cosine pennation element, $\mathbf{f}_{c\phi}(\cos \phi)$ , in the equilibrium equation

const FiberCompressiveForceLengthCurve& OpenSim::Millard2012AccelerationMuscle::getFiberCompressiveForceLengthCurve ( ) const

Returns: the FiberCompressiveForceLengthCurve that this muscle model uses

double OpenSim::Millard2012AccelerationMuscle::getFiberCompressiveForceLengthMultiplier ( SimTK::State & s ) const

Parameters

s	the state of the system

Returns: the normalized force term associated with the compressive force length element, $\mathbf{f}_K(\hat{l}_{CE})$ , in the equilibrium equation

const FiberForceLengthCurve& OpenSim::Millard2012AccelerationMuscle::getFiberForceLengthCurve ( ) const

Returns: the FiberForceLengthCurve that this muscle model uses

double OpenSim::Millard2012AccelerationMuscle::getFiberStiffnessAlongTendon ( const SimTK::State & s ) const

Returns: the stiffness of the muscle fibers along the tendon (N/m)

double OpenSim::Millard2012AccelerationMuscle::getFiberVelocity ( const SimTK::State & s ) const

Parameters

s	The state of the system

Returns: the velocity of the fiber (m/s)

const ForceVelocityCurve& OpenSim::Millard2012AccelerationMuscle::getForceVelocityCurve ( ) const

Returns: the ForceVelocityInverseCurve that this muscle model uses

double OpenSim::Millard2012AccelerationMuscle::getMass ( ) const

Returns: the size of the mass between the tendon and fiber

const MuscleFixedWidthPennationModel& OpenSim::Millard2012AccelerationMuscle::getPennationModel ( ) const

Returns: the MuscleFixedWidthPennationModel that this muscle model uses

double OpenSim::Millard2012AccelerationMuscle::getStateVariableDeriv	(	const SimTK::State &	s,
		const std::string &	aStateName
	)		const

protected

Get the derivative of an actuator state, by index.

Parameters

s	the state
aStateName	the name of the state to get.

Returns: The value of the state derivative

Array<std::string> OpenSim::Millard2012AccelerationMuscle::getStateVariableNames ( ) const

finalvirtual

Returns: A string arraw of the state variable names

Reimplemented from OpenSim::ModelComponent.

SimTK::SystemYIndex OpenSim::Millard2012AccelerationMuscle::getStateVariableSystemIndex ( const std::string & stateVariableName ) const

finalvirtual

Parameters

stateVariableName the name of the state varaible in question

Returns: The system index of the state variable in question

Reimplemented from OpenSim::ModelComponent.

const TendonForceLengthCurve& OpenSim::Millard2012AccelerationMuscle::getTendonForceLengthCurve ( ) const

Returns: the TendonForceLengthCurve that this muscle model uses

double OpenSim::Millard2012AccelerationMuscle::getTendonForceMultiplier ( SimTK::State & s ) const

Parameters

s	the state of the system

Returns: the normalized force term associated with tendon element, $\mathbf{f}_{SE}(\hat{l}_{T})$ , in the equilibrium equation

void OpenSim::Millard2012AccelerationMuscle::initStateFromProperties ( SimTK::State & s ) const

finalprotectedvirtual

Initializes the state of the ModelComponent.

Parameters

s	the state of the model

Reimplemented from OpenSim::Force.

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY	(	default_activation	,
		double	,
		"assumed initial activation level if none is assigned."
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY	(	default_fiber_length	,
		double	,
		"assumed initial fiber length if none is assigned."
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY	(	default_fiber_velocity	,
		double	,
		"assumed initial fiber velocity if none is assigned."
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY	(	fiber_damping	,
		double	,
		"fiber damping coefficient"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY	(	fiber_force_length_damping	,
		double	,
		"fiber force length damping coefficient"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY	(	fiber_compressive_force_length_damping	,
		double	,
		"fiber compressive force length damping coefficient"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY	(	fiber_compressive_force_cos_pennation_damping	,
		double	,
		"fiber compressive force cos(pennationAngle) damping coefficient"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY	(	tendon_force_length_damping	,
		double	,
		"tendon force length damping coefficient"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_PROPERTY	(	mass	,
		double	,
		"lumped mass"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	MuscleFirstOrderActivationDynamicModel	,
		"activation dynamics model with a lower bound"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	ActiveForceLengthCurve	,
		"active force length curve"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	ForceVelocityCurve	,
		"force velocity curve"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	FiberForceLengthCurve	,
		"fiber force length curve"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	TendonForceLengthCurve	,
		"Tendon force length curve"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	FiberCompressiveForceLengthCurve	,
		"fiber compressive force length curve"
	)

OpenSim::Millard2012AccelerationMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	FiberCompressiveForceCosPennationCurve	,
		"fiber compressive force cos(pennationAngle) curve"
	)

void OpenSim::Millard2012AccelerationMuscle::postScale	(	const SimTK::State &	s,
		const ScaleSet &	aScaleSet
	)

protectedvirtual

Related to scaling, soon to be removed.

Parameters

s	the state of the model
aScaleSet	the scale set

Reimplemented from OpenSim::PathActuator.

void OpenSim::Millard2012AccelerationMuscle::setActivation	(	SimTK::State &	s,
		double	activation
	)		const

virtual

Parameters

s	the state of the system
activation	the desired activation level

Implements OpenSim::Muscle.

void OpenSim::Millard2012AccelerationMuscle::setActivationModel ( MuscleFirstOrderActivationDynamicModel & aActivationMdl )

Parameters

aActivationMdl the MuscleFirstOrderActivationDynamicModel that this muscle model uses to simulate activation dynamics

void OpenSim::Millard2012AccelerationMuscle::setActiveForceLengthCurve ( ActiveForceLengthCurve & aActiveForceLengthCurve )

Parameters

aActiveForceLengthCurve the ActiveForceLengthCurve that this muscle model uses to scale active fiber force as a function of length

void OpenSim::Millard2012AccelerationMuscle::setDefaultActivation ( double activation )

Parameters

activation the default activation level that is used to initialize the muscle

void OpenSim::Millard2012AccelerationMuscle::setDefaultFiberLength ( double fiberLength )

Parameters

fiberLength the default fiber length that is used to initialize the muscle

void OpenSim::Millard2012AccelerationMuscle::setDefaultFiberVelocity ( double fiberVelocity )

Parameters

fiberVelocity the default fiber velocity that is used to initialize the muscle

void OpenSim::Millard2012AccelerationMuscle::setFiberCompressiveForceCosPennationCurve ( FiberCompressiveForceCosPennationCurve & aFiberCompressiveForceCosPennationCurve )

Parameters

aFiberCompressiveForceCosPennationCurve the FiberCompressiveForceCosPennationCurve that this muscle model uses to prevent pennation angles from approaching 90 degrees, which is associated with a singularity in this model.

void OpenSim::Millard2012AccelerationMuscle::setFiberCompressiveForceLengthCurve ( FiberCompressiveForceLengthCurve & aFiberCompressiveForceLengthCurve )

Parameters

aFiberCompressiveForceLengthCurve the FiberCompressiveForceLengthCurve that this muscle model uses to ensure the length of the fiber is always greater than a physically realistic lower bound.

void OpenSim::Millard2012AccelerationMuscle::setFiberForceLengthCurve ( FiberForceLengthCurve & aFiberForceLengthCurve )

Parameters

aFiberForceLengthCurve the FiberForceLengthCurve that this muscle model uses to calculate the passive force the muscle fiber generates as the length of the fiber changes

void OpenSim::Millard2012AccelerationMuscle::setFiberLength	(	SimTK::State &	s,
		double	fiberLength
	)		const

Parameters

s	the state of the system
fiberLength	the desired fiber length (m)

void OpenSim::Millard2012AccelerationMuscle::setFiberVelocity	(	SimTK::State &	s,
		double	fiberVelocity
	)		const

Parameters

s	the state of the system
fiberVelocity	the desired fiber velocity (m/s)

void OpenSim::Millard2012AccelerationMuscle::setForceVelocityCurve ( ForceVelocityCurve & aForceVelocityCurve )

Parameters

aForceVelocityCurve the ForceVelocityCurve that this muscle model uses to calculate the derivative of fiber length.

void OpenSim::Millard2012AccelerationMuscle::setMass ( double mass )

Parameters

mass	The size of the mass parameter between the fiber and the tendon. Making this parameter small will make the muscle model more rapidly converge to the results an equilibrium model would produce.

Conditions

    mass >= 0.001

void OpenSim::Millard2012AccelerationMuscle::setPropertiesFromState ( const SimTK::State & s )

finalprotectedvirtual

Sets the default state for ModelComponent.

Parameters

s	the state of the model

Reimplemented from OpenSim::Force.

void OpenSim::Millard2012AccelerationMuscle::setStateVariableDeriv	(	const SimTK::State &	s,
		const std::string &	aStateName,
		double	aValue
	)		const

protected

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

Parameters

s	the state
aStateName	The name of the state to set.
aValue	The value to set the state to.

void OpenSim::Millard2012AccelerationMuscle::setTendonForceLengthCurve ( TendonForceLengthCurve & aTendonForceLengthCurve )

Parameters

aTendonForceLengthCurve the TendonForceLengthCurve that this muscle model uses to define the tendon force length curve

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

OpenSim/Actuators/Millard2012AccelerationMuscle.h

Public Member Functions

Protected Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

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