This class implements a 2 state (activation and fiber length) equilibrium muscle model that uses a unilateral constraint to ensure that the singularity conditions typical of equilibrium models (when $\mathbf{a}(t) \rightarrow 0$ , $\phi \rightarrow 90^\circ$ , and $\mathbf{f}_L(\hat{l}_{CE}) \rightarrow 0$ ) are prevented. More...

#include <Millard2012EquilibriumMuscle.h>

Inheritance diagram for OpenSim::Millard2012EquilibriumMuscle:

Public Member Functions
	Millard2012EquilibriumMuscle ()
	Default constructor: produces a non-functional empty muscle.
	Millard2012EquilibriumMuscle (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.
double	getTendonForceMultiplier (SimTK::State &s) const
const MuscleFirstOrderActivationDynamicModel &	getActivationModel () const
const MuscleFixedWidthPennationModel &	getPennationModel () const
const ActiveForceLengthCurve &	getActiveForceLengthCurve () const
const ForceVelocityInverseCurve &	getForceVelocityInverseCurve () const
const FiberForceLengthCurve &	getFiberForceLengthCurve () const
const TendonForceLengthCurve &	getTendonForceLengthCurve () const
double	getFiberStiffnessAlongTendon (const SimTK::State &s) const
double	getMinimumFiberLength () const
double	getMinimumFiberLengthAlongTendon () const
double	getMinimumActivation () const
double	getMaximumPennationAngle () const
void	setActivationModel (MuscleFirstOrderActivationDynamicModel &aActivationMdl)
bool	setMinimumActivation (double minActivation)
void	setActiveForceLengthCurve (ActiveForceLengthCurve &aActiveForceLengthCurve)
void	setForceVelocityInverseCurve (ForceVelocityInverseCurve &aForceVelocityInverseCurve)
void	setFiberForceLengthCurve (FiberForceLengthCurve &aFiberForceLengthCurve)
void	setTendonForceLengthCurve (TendonForceLengthCurve &aTendonForceLengthCurve)
bool	setMaximumPennationAngle (double maxPennationAngle)
double	getDefaultActivation () const
double	getDefaultFiberLength () const
double	getActivationRate (const SimTK::State &s) const
double	getFiberVelocity (const SimTK::State &s) const
void	setDefaultActivation (double activation)
void	setDefaultFiberLength (double fiberLength)
void	setActivation (SimTK::State &s, double activation) const
void	setFiberLength (SimTK::State &s, double fiberLength) 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 override
	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.
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_UNNAMED_PROPERTY (MuscleFirstOrderActivationDynamicModel,"activation dynamics model with a lower bound")
	OpenSim_DECLARE_UNNAMED_PROPERTY (ActiveForceLengthCurve,"active force length curve")
	OpenSim_DECLARE_UNNAMED_PROPERTY (ForceVelocityInverseCurve,"force velocity inverse curve")
	OpenSim_DECLARE_UNNAMED_PROPERTY (FiberForceLengthCurve,"fiber force length curve")
	OpenSim_DECLARE_UNNAMED_PROPERTY (TendonForceLengthCurve,"Tendon force length curve")
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.
double	getMaxIsometricForce () const
	get/set the maximum isometric force (in N) that the fibers can generate
void	setMaxIsometricForce (double maxIsometricForce)
double	getOptimalFiberLength () const
	get/set the optimal length (in m) of the muscle fibers (lumped as a single fiber)
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
void	setTendonSlackLength (double tendonSlackLength)
double	getPennationAngleAtOptimalFiberLength () const
	get/set the angle (in radians) between fibers at their optimal fiber length and the tendon
void	setPennationAngleAtOptimalFiberLength (double pennationAngle)
double	getMaxContractionVelocity () const
	get/set the maximum contraction velocity of the fibers, in optimal fiber-lengths per second
void	setMaxContractionVelocity (double maxContractionVelocity)
bool	getIgnoreTendonCompliance (const SimTK::State &s) const
	Get/set Modeling (runtime) option to ignore tendon compliance when computing muscle dynamics.
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.
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 TODO: virtual to allow override by deprecated muscles.
double	getFiberLength (const SimTK::State &s) const
	get the current working fiber length (m) for the muscle
double	getPennationAngle (const SimTK::State &s) const
	get the current pennation angle (radians) between the fiber and tendon at the current fiber length
double	getTendonLength (const SimTK::State &s) const
	get the current tendon length (m) given the current joint angles and fiber length
double	getNormalizedFiberLength (const SimTK::State &s) const
	get the current normalized fiber length (fiber_length/optimal_fiber_length)
double	getFiberLengthAlongTendon (const SimTK::State &s) const
	get the current fiber length (m) projected (*cos(pennationAngle)) onto the tendon direction
double	getTendonStrain (const SimTK::State &s) const
	get the current tendon strain (delta_l/tendon_slack_length is dimensionless)
double	getFiberPotentialEnergy (const SimTK::State &s) const
	the potential energy (J) stored in the fiber due to its parallel elastic element
double	getTendonPotentialEnergy (const SimTK::State &s) const
	the potential energy (J) stored in the tendon
double	getMusclePotentialEnergy (const SimTK::State &s) const
	the total potential energy (J) stored in the muscle
double	getPassiveForceMultiplier (const SimTK::State &s) const
	get the passive fiber (parallel elastic element) force multiplier
double	getActiveForceLengthMultiplier (const SimTK::State &s) const
	get the active fiber (contractile element) force multiplier due to current fiber length
double	getNormalizedFiberVelocity (const SimTK::State &s) const
	get normalize fiber velocity (fiber_lengths/s / max_contraction_velocity)
double	getFiberVelocityAlongTendon (const SimTK::State &s) const
	get the current afiber velocity (m/s) projected onto the tendon direction
double	getPennationAngularVelocity (const SimTK::State &s) const
	get pennation angular velocity (radians/s)
double	getTendonVelocity (const SimTK::State &s) const
	get the tendon velocity (m/s) positive is lengthening
double	getForceVelocityMultiplier (const SimTK::State &s) const
	get the dimensionless multiplier resulting from the fiber's force-velocity curve
double	getFiberForce (const SimTK::State &s) const
	get the current fiber force (N) applied to the tendon
double	getActiveFiberForce (const SimTK::State &s) const
	get the current active fiber force (N) due to activationforce_lengthforce_velocity relationships
double	getPassiveFiberForce (const SimTK::State &s) const
	get the current passive fiber force (N) passive_force_length relationship
double	getActiveFiberForceAlongTendon (const SimTK::State &s) const
	get the current active fiber force (N) projected onto the tendon direction
double	getPassiveFiberForceAlongTendon (const SimTK::State &s) const
	get the current passive fiber force (N) projected onto the tendon direction
double	getTendonForce (const SimTK::State &s) const
	get the current tendon force (N) applied to bones
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.
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.
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.
double	getFiberActivePower (const SimTK::State &s) const
	get the current active fiber power (W)
double	getFiberPassivePower (const SimTK::State &s) const
	get the current passive fiber power (W)
double	getTendonPower (const SimTK::State &s) const
	get the current tendon power (W)
double	getMusclePower (const SimTK::State &s) const
	get the current muscle power (W)
double	getStress (const SimTK::State &s) const
	get the stress in the muscle (part of the Actuator interface as well)
void	setExcitation (SimTK::State &s, double excitation) const
	set the excitation (control) for this muscle.
double	getExcitation (const SimTK::State &s) const
void	equilibrate (SimTK::State &s) const
	Find and set the equilibrium state of the muscle (if any)
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.
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.
virtual double	computeMomentArm (SimTK::State &s, Coordinate &aCoord) const
virtual void	updateFromXMLNode (SimTK::Xml::Element &aNode, int versionNumber=-1)
	Use this method to deserialize an object from a SimTK::Xml::Element.
virtual void	preScale (const SimTK::State &s, const ScaleSet &aScaleSet)
virtual void	scale (const SimTK::State &s, const ScaleSet &aScaleSet)
virtual VisibleObject *	getDisplayer () const
	Methods to support making the object displayable in the GUI or Visualizer Implemented only in few objects.
virtual void	updateDisplayer (const SimTK::State &s)
	In case the ModelComponent has a visual representation (VisualObject), override this method to update it.
	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.
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
	Overriding forces The force normally produced by an Actuator can be overriden and When the Actuator's force is overriden, the Actuator will by defualt produce a constant force which can be set with setOverrideForce().
bool	isForceOverriden (const SimTK::State &s) const
	return Actuator's override status
void	setOverrideForce (SimTK::State &s, double value) const
	set the force value used when the override is true
double	getOverrideForce (const SimTK::State &s) const
	return override force
	OpenSim_DECLARE_PROPERTY (min_control, double,"Minimum allowed value for control signal. Used primarily when solving ""for control values.")
	Default is -Infinity (no limit).
	OpenSim_DECLARE_PROPERTY (max_control, double,"Maximum allowed value for control signal. Used primarily when solving ""for control values.")
	Default is Infinity (no limit).
Public Member Functions inherited from OpenSim::Actuator_
	Actuator_ ()
virtual const SimTK::Vector	getDefaultControls ()
	Actuator default controls are zero.
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.
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
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
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.
Force &	operator= (const Force &aForce)
	Implements a copy assignment operator just so it can invalidate the SimTK::Force index after the assignment.
bool	isDisabled (const SimTK::State &s) const
	Return if the Force is disabled or not.
void	setDisabled (SimTK::State &s, bool disabled)
	Set the Force as disabled (true) or not (false).
	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.
Public Member Functions inherited from OpenSim::ModelComponent
	ModelComponent ()
	Default constructor.
	ModelComponent (const std::string &aFileName, bool aUpdateFromXMLNode=true) SWIG_DECLARE_EXCEPTION
	Construct ModelComponent from an XML file.
	ModelComponent (SimTK::Xml::Element &aNode)
	Construct ModelComponent from a specific node in an XML document.
	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.
virtual	~ModelComponent ()
	Destructor is virtual to allow concrete model component cleanup.
ModelComponent &	operator= (const ModelComponent &aModelComponent)
	Assignment operator to copy contents of an existing component.
const Model &	getModel () const
	Get a const reference to the Model this component is part of.
Model &	updModel ()
	Get a modifiable reference to the Model this component is part of.
virtual int	getNumStateVariables () const
	Get the number of "Continuous" state variables maintained by the ModelComponent and its specified subcomponents.
int	getModelingOption (const SimTK::State &state, const std::string &name) const
	Get a ModelingOption flag for this ModelComponent by name.
void	setModelingOption (SimTK::State &state, const std::string &name, int flag) const
	Set the value of a ModelingOption flag for this ModelComponent.
double	getStateVariable (const SimTK::State &state, const std::string &name) const
	Get the value of a state variable allocated by this ModelComponent.
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.
double	getDiscreteVariable (const SimTK::State &state, const std::string &name) const
	Get the value of a discrete variable allocated by this ModelComponent by name.
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.
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.
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.
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.
void	markCacheVariableInvalid (const SimTK::State &state, const std::string &name) const
	Mark a cache variable value allocated by this ModelComponent as invalid.
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.
template<typename T >
void	setCacheVariable (const SimTK::State &state, const std::string &name, T &value) const
	Set cache variable value allocated by this ModelComponent by name.
Public Member Functions inherited from OpenSim::Object
virtual	~Object ()
	Virtual destructor for cleanup.
virtual Object *	clone () const =0
	Create a new heap-allocated copy of the concrete object to which this Object refers.
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.
virtual VisibleObject *	updDisplayer ()
	get Non const pointer to VisibleObject
bool	isEqualTo (const Object &aObject) const
	Equality operator wrapper for use from languages not supporting operator overloading.
Object &	operator= (const Object &aObject)
	Copy assignment copies he base class fields, including the properties.
virtual bool	operator== (const Object &aObject) const
	Determine if two objects are equal.
virtual bool	operator< (const Object &aObject) const
	Provide an ordering for objects so they can be put in sorted containers.
void	setName (const std::string &name)
	Set the name of the Object.
const std::string &	getName () const
	Get the name of this Object.
void	setDescription (const std::string &description)
	Set description, a one-liner summary.
const std::string &	getDescription () const
	Get description, a one-liner summary.
const std::string &	getAuthors () const
	Get Authors of this Object.
void	setAuthors (const std::string &authors)
	Set Authors of this object, call this method in your constructor if needed.
const std::string &	getReferences () const
	Get references or publications to cite if using this object.
void	setReferences (const std::string &references)
	Set references or publications to cite if using this object.
int	getNumProperties () const
	Determine how many properties are stored with this Object.
const AbstractProperty &	getPropertyByIndex (int propertyIndex) const
	Get a const reference to a property by its index number, returned as an AbstractProperty.
AbstractProperty &	updPropertyByIndex (int propertyIndex)
	Get a writable reference to a property by its index number, returned as an AbstractProperty.
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.
const AbstractProperty &	getPropertyByName (const std::string &name) const
	Get a const reference to a property by its name, returned as an AbstractProperty.
AbstractProperty &	updPropertyByName (const std::string &name)
	Get a writable reference to a property by its name, returned as an AbstractProperty.
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.
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.
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.
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.
bool	isObjectUpToDateWithProperties () const
	Returns \c true if any property's value has changed since the last time setObjectIsUpToDateWithProperties() was called.
void	readObjectFromXMLNodeOrFile (SimTK::Xml::Element &objectElement, int versionNumber)
	We're given an XML element from which we are to populate this Object.
virtual void	updateXMLNode (SimTK::Xml::Element &parent)
	Serialize this object into the XML node that represents it.
bool	getInlined () const
	Inlined means an in-memory Object that is not associated with an XMLDocument.
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.
std::string	getDocumentFileName () const
	If there is a document associated with this object then return the file name maintained by the document.
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".
std::string	dump (bool dumpName=false)
	dump the XML representation of this Object into an std::string and return it.
void	clearObjectIsUpToDateWithProperties ()
	For testing or debugging purposes, manually clear the "object is up to date with respect to properties" flag.
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.
const std::string &	toString () const
	Wrapper to be used on Java side to display objects in tree; this returns just the object's name.
PropertySet &	getPropertySet ()
	OBSOLETE: Get a reference to the PropertySet maintained by the Object.
const PropertySet &	getPropertySet () const

Protected Member Functions
void	postScale (const SimTK::State &s, const ScaleSet &aScaleSet)
	Courtesy of Ajay.
double	calcActivationRate (const SimTK::State &s) const
	Calculate activation rate.
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...
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...
virtual 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
void	connectToModel (Model &model) override
	Sets up the ModelComponent from the model, if necessary.
void	addToSystem (SimTK::MultibodySystem &system) const override
	Creates the ModelComponent so that it can be used in simulation.
void	initStateFromProperties (SimTK::State &s) const override
	Initializes the state of the ModelComponent.
void	setPropertiesFromState (const SimTK::State &s) override
	Sets the default state for ModelComponent.
SimTK::Vector	computeStateVariableDerivatives (const SimTK::State &s) const override
	computes state variable derivatives
void	setStateVariableDeriv (const SimTK::State &s, const std::string &aStateName, double aValue) const
	Set the derivative of an actuator state, specified by name.
double	getStateVariableDeriv (const SimTK::State &s, const std::string &aStateName) const
	Get the derivative of an actuator state, by index.
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.
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
virtual void	computeForce (const SimTK::State &state, SimTK::Vector_< SimTK::SpatialVec > &bodyForces, SimTK::Vector &generalizedForce) const
	Force interface applies tension to bodies, and Muscle also checks that applied muscle tension is not negative.
virtual double	computePotentialEnergy (const SimTK::State &state) const
	Potential energy stored by the muscle.
virtual void	updateGeometry (const SimTK::State &s)

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.
static void	renameType (const std::string &oldTypeName, const std::string &newTypeName)
	Support versioning by associating the current %Object type with an old name.
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.
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*.
static Object *	newInstanceOfType (const std::string &concreteClassName)
	Create a new instance of the concrete %Object type whose class name is given as concreteClassName.
static void	getRegisteredTypenames (Array< std::string > &typeNames)
	Retrieve all the typenames registered so far.
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.
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.
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.
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.
static const std::string &	getClassName ()
	Return the name of this class as a string; i.e., "Object".
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.
static bool	getSerializeAllDefaults ()
	Report the value of the "serialize all defaults" flag.
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.
static void	setDebugLevel (int newLevel)
	Set the debug level to get verbose output.
static int	getDebugLevel ()
	Get current setting of debug level.
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.
static void	RegisterType (const Object &defaultObject)
	OBSOLETE alternate name for registerType().
static void	RenameType (const std::string &oldName, const std::string &newName)
	OBSOLETE alternate name for renameType().
Static Public Attributes inherited from OpenSim::Object
static const std::string	DEFAULT_NAME
	Name used for default objects when they are serialized.
Protected Attributes inherited from OpenSim::Muscle
double	_muscleWidth
	The assumed fixed muscle-width from which the fiber pennation angle is calculated.
double	_maxIsometricForce
	to support deprecated muscles
double	_optimalFiberLength
double	_pennationAngleAtOptimal
double	_tendonSlackLength
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.
#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.
#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>.
#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.

Detailed Description

This class implements a 2 state (activation and fiber length) equilibrium muscle model that uses a unilateral constraint to ensure that the singularity conditions typical of equilibrium models (when $\mathbf{a}(t) \rightarrow 0$ , $\phi \rightarrow 90^\circ$ , and $\mathbf{f}_L(\hat{l}_{CE}) \rightarrow 0$ ) are prevented.

Physically these modifications mean that this muscle model is always activated ( $\mathbf{a}(t) > 0$ ), the fiber will stop contracting when a pennation angle of 90 degrees is approached ( $\phi < 90^\circ$ ), and the fiber will also stop contracting as its length approaches a lower bound ( $\hat{l}_{CE} > lowerbound$ ), typically around half the fiber's resting length ( to ensure $\mathbf{f}_L(\hat{l}_{CE}) > 0$ ). The fiber length is prevented from achieving either an unphysiological length, or its maximum pennation angle, through the use of a unilateral constraint.

As is typical of an equilibrium model, the force generated by the tendon and the force generated by the fiber are assumed to be equal and opposite:

$f_{ISO}\Big(\mathbf{a}(t) \mathbf{f}_L(\hat{l}_{CE}) \mathbf{f}_V(\hat{v}_{CE}) + \mathbf{f}_{PE}(\hat{l}_{CE}) )\Big) \cos \phi - f_{ISO}\mathbf{f}_{SE}(\hat{l}_{T}) = 0$

As with any other equilibrium model, the above equation is rearranged to isolate for $\mathbf{f}_V(\hat{v}_{CE})$ , which is inverted to solve for $\hat{v}_{CE}$ , and then is numerically integrated during simulation:

$\hat{v}_{CE} = \mathbf{f}_V ^{-1} ( \frac{ ( \mathbf{f}_{SE}(\hat{l}_{T}) ) / \cos \phi - \mathbf{f}_{PE}(\hat{l}_{CE}) } { \mathbf{a}(t) \mathbf{f}_L(\hat{l}_{CE})} )$

As with any equilibrium muscle model, the numerical stiffness of the above equation increases when terms in the denominator approach zero (when $\mathbf{a}(t) \rightarrow 0$ , $\phi \rightarrow 90^\circ$ , or $\mathbf{f}_L(\hat{l}_{CE}) \rightarrow 0$ ) or additionally when the slope of $\mathbf{f}_V ^{-1}$ is steep (which occurs at fiber velocities close to the maximum concentric and maximum eccentric fiber velocities).

For more information please see the doxygen for the properties that are objects themselves ( such as MuscleFirstOrderActivationDynamicModel, MuscleFixedWidthPennationModel).

Author: Matt Millard

Constructor & Destructor Documentation

OpenSim::Millard2012EquilibriumMuscle::Millard2012EquilibriumMuscle ( )

Default constructor: produces a non-functional empty muscle.

OpenSim::Millard2012EquilibriumMuscle::Millard2012EquilibriumMuscle	(	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::Millard2012EquilibriumMuscle::addToSystem ( SimTK::MultibodySystem & system ) const

overrideprotectedvirtual

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

Reimplemented from OpenSim::Muscle.

double OpenSim::Millard2012EquilibriumMuscle::calcActivationRate ( const SimTK::State & s ) const

protected

Calculate activation rate.

virtual void OpenSim::Millard2012EquilibriumMuscle::calcFiberVelocityInfo	(	const SimTK::State &	s,
		FiberVelocityInfo &	fvi
	)		const

protectedvirtual

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

Reimplemented from OpenSim::Muscle.

virtual void OpenSim::Millard2012EquilibriumMuscle::calcMuscleDynamicsInfo	(	const SimTK::State &	s,
		MuscleDynamicsInfo &	mdi
	)		const

protectedvirtual

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

Reimplemented from OpenSim::Muscle.

void OpenSim::Millard2012EquilibriumMuscle::calcMuscleLengthInfo	(	const SimTK::State &	s,
		MuscleLengthInfo &	mli
	)		const

protectedvirtual

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

Reimplemented from OpenSim::Muscle.

double OpenSim::Millard2012EquilibriumMuscle::computeActuation ( const SimTK::State & s ) const

virtual

Parameters

s	the state of the system

Returns: the tensile force the muscle is generating in N

Implements OpenSim::Muscle.

void OpenSim::Millard2012EquilibriumMuscle::computeInitialFiberEquilibrium ( SimTK::State & s ) const

overridevirtual

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::Millard2012EquilibriumMuscle::computeStateVariableDerivatives ( const SimTK::State & s ) const

overrideprotectedvirtual

computes state variable derivatives

Reimplemented from OpenSim::ModelComponent.

void OpenSim::Millard2012EquilibriumMuscle::connectToModel ( Model & model )

overrideprotectedvirtual

Sets up the ModelComponent from the model, if necessary.

Reimplemented from OpenSim::Muscle.

const MuscleFirstOrderActivationDynamicModel& OpenSim::Millard2012EquilibriumMuscle::getActivationModel ( ) const

Returns: the MuscleFirstOrderActivationDynamicModel that this muscle model uses

double OpenSim::Millard2012EquilibriumMuscle::getActivationRate ( const SimTK::State & s ) const

Parameters

s	The state of the system

Returns: the time derivative of activation

const ActiveForceLengthCurve& OpenSim::Millard2012EquilibriumMuscle::getActiveForceLengthCurve ( ) const

Returns: the ActiveForceLengthCurve that this muscle model uses

double OpenSim::Millard2012EquilibriumMuscle::getDefaultActivation ( ) const

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

double OpenSim::Millard2012EquilibriumMuscle::getDefaultFiberLength ( ) const

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

const FiberForceLengthCurve& OpenSim::Millard2012EquilibriumMuscle::getFiberForceLengthCurve ( ) const

Returns: the FiberForceLengthCurve that this muscle model uses

double OpenSim::Millard2012EquilibriumMuscle::getFiberStiffnessAlongTendon ( const SimTK::State & s ) const

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

double OpenSim::Millard2012EquilibriumMuscle::getFiberVelocity ( const SimTK::State & s ) const

Parameters

s	The state of the system

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

Reimplemented from OpenSim::Muscle.

const ForceVelocityInverseCurve& OpenSim::Millard2012EquilibriumMuscle::getForceVelocityInverseCurve ( ) const

Returns: the ForceVelocityInverseCurve that this muscle model uses

double OpenSim::Millard2012EquilibriumMuscle::getMaximumPennationAngle ( ) const

Returns: the maximum pennation angle allowed by this muscle model. Note that this equilibrium model, like all equilibrium models has a singularity when pennation hits Pi/2.0. This requires that the maximum pennation angle must be less than Pi/2.0.

double OpenSim::Millard2012EquilibriumMuscle::getMinimumActivation ( ) const

Returns: the minimum activation level allowed by the muscle model. Note that this equilibrium model, like all equilibrium models has a singularity when activation goes to 0.0, which means that a non-zero lower bound is required.

double OpenSim::Millard2012EquilibriumMuscle::getMinimumFiberLength ( ) const

Returns: the minimum fiber length, which is the maximum of two values: the smallest fiber length allowed by the pennation model, and the minimum fiber length in the active force length curve. When the fiber length reaches this value, it is constrained to this value until the fiber velocity goes positive.

double OpenSim::Millard2012EquilibriumMuscle::getMinimumFiberLengthAlongTendon ( ) const

Returns: the minimum fiber length along the tendon, which is the maximum of two values: the smallest fiber length along the teond allowed by the pennation model, and the minimum fiber length along the tendon in the active force length curve. When the fiber length reaches this value, it is constrained to this length along the tendon until the fiber velocity goes positive.

const MuscleFixedWidthPennationModel& OpenSim::Millard2012EquilibriumMuscle::getPennationModel ( ) const

Returns: the MuscleFixedWidthPennationModel that this muscle model uses

double OpenSim::Millard2012EquilibriumMuscle::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::Millard2012EquilibriumMuscle::getStateVariableNames ( ) const

virtual

Returns: A string arraw of the state variable names

Reimplemented from OpenSim::ModelComponent.

SimTK::SystemYIndex OpenSim::Millard2012EquilibriumMuscle::getStateVariableSystemIndex ( const std::string & stateVariableName ) const

virtual

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::Millard2012EquilibriumMuscle::getTendonForceLengthCurve ( ) const

Returns: the TendonForceLengthCurve that this muscle model uses

double OpenSim::Millard2012EquilibriumMuscle::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::Millard2012EquilibriumMuscle::initStateFromProperties ( SimTK::State & s ) const

overrideprotectedvirtual

Initializes the state of the ModelComponent.

Reimplemented from OpenSim::Muscle.

OpenSim::Millard2012EquilibriumMuscle::OpenSim_DECLARE_PROPERTY	(	default_activation	,
		double	,
		"assumed initial activation level if none is assigned."
	)

OpenSim::Millard2012EquilibriumMuscle::OpenSim_DECLARE_PROPERTY	(	default_fiber_length	,
		double	,
		"assumed initial fiber length if none is assigned."
	)

OpenSim::Millard2012EquilibriumMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	MuscleFirstOrderActivationDynamicModel	,
		"activation dynamics model with a lower bound"
	)

OpenSim::Millard2012EquilibriumMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	ActiveForceLengthCurve	,
		"active force length curve"
	)

OpenSim::Millard2012EquilibriumMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	ForceVelocityInverseCurve	,
		"force velocity inverse curve"
	)

OpenSim::Millard2012EquilibriumMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	FiberForceLengthCurve	,
		"fiber force length curve"
	)

OpenSim::Millard2012EquilibriumMuscle::OpenSim_DECLARE_UNNAMED_PROPERTY	(	TendonForceLengthCurve	,
		"Tendon force length curve"
	)

void OpenSim::Millard2012EquilibriumMuscle::postScale	(	const SimTK::State &	s,
		const ScaleSet &	aScaleSet
	)

protectedvirtual

Courtesy of Ajay.

Reimplemented from OpenSim::PathActuator.

void OpenSim::Millard2012EquilibriumMuscle::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::Millard2012EquilibriumMuscle::setActivationModel ( MuscleFirstOrderActivationDynamicModel & aActivationMdl )

Parameters

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

void OpenSim::Millard2012EquilibriumMuscle::setActiveForceLengthCurve ( ActiveForceLengthCurve & aActiveForceLengthCurve )

Parameters

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

void OpenSim::Millard2012EquilibriumMuscle::setDefaultActivation ( double activation )

Parameters

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

void OpenSim::Millard2012EquilibriumMuscle::setDefaultFiberLength ( double fiberLength )

Parameters

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

void OpenSim::Millard2012EquilibriumMuscle::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::Millard2012EquilibriumMuscle::setFiberLength	(	SimTK::State &	s,
		double	fiberLength
	)		const

Parameters

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

void OpenSim::Millard2012EquilibriumMuscle::setForceVelocityInverseCurve ( ForceVelocityInverseCurve & aForceVelocityInverseCurve )

Parameters

aForceVelocityInverseCurve the ForceVelocityInverseCurve that this muscle model uses to calculate the derivative of fiber length.

bool OpenSim::Millard2012EquilibriumMuscle::setMaximumPennationAngle ( double maxPennationAngle )

Parameters

maxPennationAngle is the maximum pennation (radians). This method will set the maximum pennation angle property of the pennation model, and is provided to ensure that the desired maximum pennation angle will not cause a numerical singularity in this model.

Returns: true if the value was acceptable and the property was set

bool OpenSim::Millard2012EquilibriumMuscle::setMinimumActivation ( double minActivation )

Parameters

minActivation will set the minimum activation property in the Activation model. This function is provided to ensure that the desired minimum activation will not cause a numerical singularity in this model.

Returns: true if the value was acceptable and the property was set

void OpenSim::Millard2012EquilibriumMuscle::setPropertiesFromState ( const SimTK::State & s )

overrideprotectedvirtual

Sets the default state for ModelComponent.

Reimplemented from OpenSim::Muscle.

void OpenSim::Millard2012EquilibriumMuscle::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::Millard2012EquilibriumMuscle::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:

E:/Projects/OpenSim30Br/OpenSim30/OpenSim/Actuators/Millard2012EquilibriumMuscle.h

Public Member Functions

Overriding forces

Protected Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation