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OpenSim::Muscle Class Reference

A base class for modeling a muscle-tendon actuator. More...

#include <Muscle.h>

Inheritance diagram for OpenSim::Muscle:
OpenSim::PathActuator OpenSim::Actuator OpenSim::Actuator_ OpenSim::Force OpenSim::ModelComponent OpenSim::Object OpenSim::ActivationFiberLengthMuscle OpenSim::ActivationFiberLengthMuscle_Deprecated OpenSim::Millard2012AccelerationMuscle OpenSim::Millard2012EquilibriumMuscle OpenSim::RigidTendonMuscle OpenSim::Thelen2003Muscle OpenSim::ContDerivMuscle_Deprecated OpenSim::Delp1990Muscle_Deprecated OpenSim::Schutte1993Muscle_Deprecated OpenSim::Thelen2003Muscle_Deprecated

Classes

struct  FiberVelocityInfo
 FiberVelocityInfo contains velocity quantities related to the velocity of the muscle (fiber + tendon) complex. More...
struct  MuscleDynamicsInfo
 MuscleDynamicsInfo contains quantities that are related to the forces that the muscle generates. More...
struct  MuscleLengthInfo
 The MuscleLengthInfo struct contains information about the muscle that is strictly a function of the length of the fiber and the tendon, and the orientation of the muscle fiber. More...

Public Member Functions

double computeActuation (const SimTK::State &s) const =0
 Actuator interface for a muscle computes the tension in the muscle and applied by the tendon to bones (i.e.
Property declarations

These are the serializable properties associated with the Muscle class.

Note that concrete muscles derived from this class inherit all these properties.

 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.")
Constructors and Destructor
 Muscle ()
 Default constructor.
Muscle Parameters Access Methods
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)
Muscle State Dependent Access Methods

Get quantities of interest common to all muscles

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 getFiberVelocity (const SimTK::State &s) const
 get current fiber velocity (m/s) positive is lengthening
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 activation*force_length*force_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
virtual void setActivation (SimTK::State &s, double activation) const =0
 DEPRECATED: only for backward compatibility.
Muscle initialization
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 ()
GeometryPathupdGeometryPath ()
const GeometryPathgetGeometryPath () 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 void postScale (const SimTK::State &s, const ScaleSet &aScaleSet)
virtual VisibleObjectgetDisplayer () 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.

Forceoperator= (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.
ModelComponentoperator= (const ModelComponent &aModelComponent)
 Assignment operator to copy contents of an existing component.
const ModelgetModel () const
 Get a const reference to the Model this component is part of.
ModelupdModel ()
 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.
virtual Array< std::string > getStateVariableNames () const
 Get the names of "continuous" state variables maintained by the ModelComponent and its subcomponents.
virtual SimTK::SystemYIndex getStateVariableSystemIndex (const std::string &stateVariableName) const
 Get the System Index of a state variable allocated by this ModelComponent.
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 Objectclone () 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 VisibleObjectupdDisplayer ()
 get Non const pointer to VisibleObject
bool isEqualTo (const Object &aObject) const
 Equality operator wrapper for use from languages not supporting operator overloading.
Objectoperator= (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 AbstractPropertygetPropertyByIndex (int propertyIndex) const
 
Get a const reference to a property by its index number, returned as

an AbstractProperty.

AbstractPropertyupdPropertyByIndex (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 AbstractPropertygetPropertyByName (const std::string &name) const
 
Get a const reference to a property by its name, returned as

an AbstractProperty.

AbstractPropertyupdPropertyByName (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.

PropertySetgetPropertySet ()
 
OBSOLETE: Get a reference to the PropertySet maintained by the 

Object.

const PropertySetgetPropertySet () const

Protected Member Functions

const MuscleLengthInfogetMuscleLengthInfo (const SimTK::State &s) const
 Developer Access to intermediate values calculate by the muscle model.
MuscleLengthInfoupdMuscleLengthInfo (const SimTK::State &s) const
const FiberVelocityInfogetFiberVelocityInfo (const SimTK::State &s) const
FiberVelocityInfoupdFiberVelocityInfo (const SimTK::State &s) const
const MuscleDynamicsInfogetMuscleDynamicsInfo (const SimTK::State &s) const
MuscleDynamicsInfoupdMuscleDynamicsInfo (const SimTK::State &s) const
Muscle State Dependent Calculations

Developers must override these methods to implement the desired behavior of their muscle models.

Unless you are augmenting the behavior of an existing muscle class or writing a new derived class, you do not have access to these methods.

virtual void calcMuscleLengthInfo (const SimTK::State &s, MuscleLengthInfo &mli) const
 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
 calculate muscle's fiber velocity and pennation angular velocity, etc...
virtual void calcMuscleDynamicsInfo (const SimTK::State &s, MuscleDynamicsInfo &mdi) const
 calculate muscle's active and passive force-length, force-velocity, tendon force, relationships and their related values
virtual void computeInitialFiberEquilibrium (SimTK::State &s) const =0
 compute initial fiber length (velocity) such that muscle fiber and tendon are in static equilibrium and update the state
Interfaces imposed by parent classes
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.
void connectToModel (Model &aModel) override
 Model Component creation interface.
void addToSystem (SimTK::MultibodySystem &system) const override
 
Default is to create a ForceAdapter which is a SimTK::Force::Custom

as the underlying computational component.

void setPropertiesFromState (const SimTK::State &s) override
 
Subclass should override; be sure to invoke 

Force::setPropertiesFromState() at the beginning of the overriding method.

void initStateFromProperties (SimTK::State &state) const override
 
Subclass should override; be sure to invoke Force::initStateFromProperties() at the

beginning of the overriding method.

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

Protected Attributes

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

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 ObjectgetDefaultInstanceOfType (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 ObjectnewInstanceOfType (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 ObjectmakeObjectFromFile (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 ObjectSafeCopy (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.

Detailed Description

A base class for modeling a muscle-tendon actuator.

It defines muscle parameters and methods to PathActuator, but does not implement all of the necessary methods, and remains an abstract class. The path information for a muscle is contained in PathActuator, and the force-generating behavior should be defined in the derived classes.

This class defines a subset of muscle models that include an active fiber (contractile element) in series with a tendon. This class defines common data members and handles the geometry of a unipennate fiber in connection with a tendon. No states are assumed, but concrete classes are free to add whatever states are necessary to describe the specific behavior of a muscle.

Author
Ajay Seth, Matt Millard

(Based on earlier work by Peter Loan and Frank C. Anderson.)

Constructor & Destructor Documentation

OpenSim::Muscle::Muscle ( )

Default constructor.

Member Function Documentation

void OpenSim::Muscle::addToSystem ( SimTK::MultibodySystem &  system) const
overrideprotectedvirtual

Default is to create a ForceAdapter which is a SimTK::Force::Custom

as the underlying computational component.

Subclasses override to employ other SimTK::Forces; be sure to invoke Force::addToSystem() at the beginning of the overriding method.

Reimplemented from OpenSim::Actuator.

Reimplemented in OpenSim::Millard2012AccelerationMuscle, OpenSim::Millard2012EquilibriumMuscle, OpenSim::Thelen2003Muscle, OpenSim::ContDerivMuscle_Deprecated, OpenSim::Delp1990Muscle_Deprecated, OpenSim::ActivationFiberLengthMuscle_Deprecated, and OpenSim::ActivationFiberLengthMuscle.

virtual void OpenSim::Muscle::calcFiberVelocityInfo ( const SimTK::State &  s,
FiberVelocityInfo fvi 
) const
protectedvirtual
virtual void OpenSim::Muscle::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 in OpenSim::Millard2012AccelerationMuscle, OpenSim::Millard2012EquilibriumMuscle, OpenSim::Thelen2003Muscle, OpenSim::ActivationFiberLengthMuscle_Deprecated, and OpenSim::RigidTendonMuscle.

virtual void OpenSim::Muscle::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 in OpenSim::Millard2012AccelerationMuscle, OpenSim::Millard2012EquilibriumMuscle, OpenSim::Thelen2003Muscle, OpenSim::ActivationFiberLengthMuscle_Deprecated, and OpenSim::RigidTendonMuscle.

double OpenSim::Muscle::computeActuation ( const SimTK::State &  s) const
pure virtual
virtual void OpenSim::Muscle::computeForce ( const SimTK::State &  state,
SimTK::Vector_< SimTK::SpatialVec > &  bodyForces,
SimTK::Vector &  generalizedForce 
) const
protectedvirtual

Force interface applies tension to bodies, and Muscle also checks that applied muscle tension is not negative.

Reimplemented from OpenSim::PathActuator.

Reimplemented in OpenSim::ActivationFiberLengthMuscle_Deprecated, and OpenSim::ActivationFiberLengthMuscle.

virtual void OpenSim::Muscle::computeInitialFiberEquilibrium ( SimTK::State &  s) const
protectedpure virtual

compute initial fiber length (velocity) such that muscle fiber and tendon are in static equilibrium and update the state

Implemented in OpenSim::Millard2012AccelerationMuscle, OpenSim::Millard2012EquilibriumMuscle, OpenSim::Thelen2003Muscle, OpenSim::ActivationFiberLengthMuscle_Deprecated, and OpenSim::RigidTendonMuscle.

virtual double OpenSim::Muscle::computePotentialEnergy ( const SimTK::State &  state) const
protectedvirtual

Potential energy stored by the muscle.

Reimplemented from OpenSim::Force.

void OpenSim::Muscle::connectToModel ( Model aModel)
overrideprotectedvirtual
void OpenSim::Muscle::equilibrate ( SimTK::State &  s) const
inline

Find and set the equilibrium state of the muscle (if any)

Reimplemented in OpenSim::RigidTendonMuscle, and OpenSim::ActivationFiberLengthMuscle_Deprecated.

virtual double OpenSim::Muscle::getActivation ( const SimTK::State &  s) const
virtual

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.

Reimplemented in OpenSim::ContDerivMuscle_Deprecated, and OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getActiveFiberForce ( const SimTK::State &  s) const

get the current active fiber force (N) due to activation*force_length*force_velocity relationships

Reimplemented in OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getActiveFiberForceAlongTendon ( const SimTK::State &  s) const

get the current active fiber force (N) projected onto the tendon direction

Reimplemented in OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getActiveForceLengthMultiplier ( const SimTK::State &  s) const

get the active fiber (contractile element) force multiplier due to current fiber length

double OpenSim::Muscle::getExcitation ( const SimTK::State &  s) const
double OpenSim::Muscle::getFiberActivePower ( const SimTK::State &  s) const

get the current active fiber power (W)

double OpenSim::Muscle::getFiberForce ( const SimTK::State &  s) const

get the current fiber force (N) applied to the tendon

Reimplemented in OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getFiberLength ( const SimTK::State &  s) const

get the current working fiber length (m) for the muscle

Reimplemented in OpenSim::ContDerivMuscle_Deprecated, and OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getFiberLengthAlongTendon ( const SimTK::State &  s) const

get the current fiber length (m) projected (*cos(pennationAngle)) onto the tendon direction

Reimplemented in OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getFiberPassivePower ( const SimTK::State &  s) const

get the current passive fiber power (W)

double OpenSim::Muscle::getFiberPotentialEnergy ( const SimTK::State &  s) const

the potential energy (J) stored in the fiber due to its parallel elastic element

double OpenSim::Muscle::getFiberStiffness ( const SimTK::State &  s) const

get the current fiber stiffness (N/m) defined as the partial derivative of fiber force w.r.t.

fiber length

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

get current fiber velocity (m/s) positive is lengthening

Reimplemented in OpenSim::Millard2012AccelerationMuscle, OpenSim::Millard2012EquilibriumMuscle, and OpenSim::Delp1990Muscle_Deprecated.

double OpenSim::Muscle::getFiberVelocityAlongTendon ( const SimTK::State &  s) const

get the current afiber velocity (m/s) projected onto the tendon direction

const FiberVelocityInfo& OpenSim::Muscle::getFiberVelocityInfo ( const SimTK::State &  s) const
protected
double OpenSim::Muscle::getForceVelocityMultiplier ( const SimTK::State &  s) const

get the dimensionless multiplier resulting from the fiber's force-velocity curve

bool OpenSim::Muscle::getIgnoreActivationDynamics ( const SimTK::State &  s) const

Get/set Modeling (runtime) option to ignore activation dynamics when 

computing muscle dynamics.

This does not directly modify the persistent property value.

bool OpenSim::Muscle::getIgnoreTendonCompliance ( const SimTK::State &  s) const

Get/set Modeling (runtime) option to ignore tendon compliance when 

computing muscle dynamics.

This does not directly modify the persistent property value.

double OpenSim::Muscle::getMaxContractionVelocity ( ) const

get/set the maximum contraction velocity of the fibers, in optimal fiber-lengths per second

double OpenSim::Muscle::getMaxIsometricForce ( ) const

get/set the maximum isometric force (in N) that the fibers can generate

const MuscleDynamicsInfo& OpenSim::Muscle::getMuscleDynamicsInfo ( const SimTK::State &  s) const
protected
const MuscleLengthInfo& OpenSim::Muscle::getMuscleLengthInfo ( const SimTK::State &  s) const
protected

Developer Access to intermediate values calculate by the muscle model.

double OpenSim::Muscle::getMusclePotentialEnergy ( const SimTK::State &  s) const

the total potential energy (J) stored in the muscle

double OpenSim::Muscle::getMusclePower ( const SimTK::State &  s) const

get the current muscle power (W)

double OpenSim::Muscle::getMuscleStiffness ( const SimTK::State &  s) const

get the current muscle stiffness (N/m) defined as the partial derivative of muscle force w.r.t.

muscle length

double OpenSim::Muscle::getNormalizedFiberLength ( const SimTK::State &  s) const

get the current normalized fiber length (fiber_length/optimal_fiber_length)

Reimplemented in OpenSim::ContDerivMuscle_Deprecated, and OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getNormalizedFiberVelocity ( const SimTK::State &  s) const

get normalize fiber velocity (fiber_lengths/s / max_contraction_velocity)

double OpenSim::Muscle::getOptimalFiberLength ( ) const

get/set the optimal length (in m) of the muscle fibers (lumped as a single fiber)

double OpenSim::Muscle::getPassiveFiberForce ( const SimTK::State &  s) const

get the current passive fiber force (N) passive_force_length relationship

Reimplemented in OpenSim::ContDerivMuscle_Deprecated, and OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getPassiveFiberForceAlongTendon ( const SimTK::State &  s) const

get the current passive fiber force (N) projected onto the tendon direction

Reimplemented in OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getPassiveForceMultiplier ( const SimTK::State &  s) const

get the passive fiber (parallel elastic element) force multiplier

double OpenSim::Muscle::getPennationAngle ( const SimTK::State &  s) const

get the current pennation angle (radians) between the fiber and tendon at the current fiber length

double OpenSim::Muscle::getPennationAngleAtOptimalFiberLength ( ) const

get/set the angle (in radians) between fibers at their optimal fiber length and the tendon

double OpenSim::Muscle::getPennationAngularVelocity ( const SimTK::State &  s) const

get pennation angular velocity (radians/s)

double OpenSim::Muscle::getStress ( const SimTK::State &  s) const
virtual

get the stress in the muscle (part of the Actuator interface as well)

Reimplemented from OpenSim::PathActuator.

Reimplemented in OpenSim::ContDerivMuscle_Deprecated, and OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getTendonForce ( const SimTK::State &  s) const

get the current tendon force (N) applied to bones

Reimplemented in OpenSim::ContDerivMuscle_Deprecated, and OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getTendonLength ( const SimTK::State &  s) const

get the current tendon length (m) given the current joint angles and fiber length

Reimplemented in OpenSim::ActivationFiberLengthMuscle_Deprecated.

double OpenSim::Muscle::getTendonPotentialEnergy ( const SimTK::State &  s) const

the potential energy (J) stored in the tendon

double OpenSim::Muscle::getTendonPower ( const SimTK::State &  s) const

get the current tendon power (W)

double OpenSim::Muscle::getTendonSlackLength ( ) const

get/set the resting (slack) length (in m) of the tendon that is in series with the muscle fiber

double OpenSim::Muscle::getTendonStiffness ( const SimTK::State &  s) const

get the current tendon stiffness (N/m) defined as the partial derivative of tendon force w.r.t.

tendon length

double OpenSim::Muscle::getTendonStrain ( const SimTK::State &  s) const

get the current tendon strain (delta_l/tendon_slack_length is dimensionless)

double OpenSim::Muscle::getTendonVelocity ( const SimTK::State &  s) const

get the tendon velocity (m/s) positive is lengthening

void OpenSim::Muscle::initStateFromProperties ( SimTK::State &  state) const
overrideprotectedvirtual

Subclass should override; be sure to invoke Force::initStateFromProperties() at the

beginning of the overriding method.

Reimplemented from OpenSim::Force.

Reimplemented in OpenSim::Millard2012AccelerationMuscle, OpenSim::Millard2012EquilibriumMuscle, OpenSim::ActivationFiberLengthMuscle_Deprecated, and OpenSim::ActivationFiberLengthMuscle.

OpenSim::Muscle::OpenSim_DECLARE_PROPERTY ( max_isometric_force  ,
double  ,
"Maximum isometric force that the fibers can generate"   
)
OpenSim::Muscle::OpenSim_DECLARE_PROPERTY ( optimal_fiber_length  ,
double  ,
"Optimal length of the muscle fibers"   
)
OpenSim::Muscle::OpenSim_DECLARE_PROPERTY ( tendon_slack_length  ,
double  ,
"Resting length of the tendon"   
)
OpenSim::Muscle::OpenSim_DECLARE_PROPERTY ( pennation_angle_at_optimal  ,
double  ,
"Angle between tendon and fibers at optimal fiber length expressed in radians"   
)
OpenSim::Muscle::OpenSim_DECLARE_PROPERTY ( max_contraction_velocity  ,
double  ,
"Maximum contraction velocity of the  fibers,
in optimal fiberlengths/second"   
)
OpenSim::Muscle::OpenSim_DECLARE_PROPERTY ( ignore_tendon_compliance  ,
bool  ,
"Compute muscle dynamics ignoring tendon compliance. Tendon is assumed to be rigid."   
)
OpenSim::Muscle::OpenSim_DECLARE_PROPERTY ( ignore_activation_dynamics  ,
bool  ,
"Compute muscle dynamics ignoring activation dynamics. Activation is equivalent to excitation."   
)
virtual void OpenSim::Muscle::setActivation ( SimTK::State &  s,
double  activation 
) const
pure virtual
void OpenSim::Muscle::setExcitation ( SimTK::State &  s,
double  excitation 
) const

set the excitation (control) for this muscle.

NOTE if controllers are connected to the muscle and are adding in their controls, and setExcitation is called after the model's computeControls(), then setExcitation will override the controller values. If called before computeControls, then controller value(s) are added to the excitation set here.

void OpenSim::Muscle::setIgnoreActivationDynamics ( SimTK::State &  s,
bool  ignore 
) const
void OpenSim::Muscle::setIgnoreTendonCompliance ( SimTK::State &  s,
bool  ignore 
) const
void OpenSim::Muscle::setMaxContractionVelocity ( double  maxContractionVelocity)
void OpenSim::Muscle::setMaxIsometricForce ( double  maxIsometricForce)
void OpenSim::Muscle::setOptimalFiberLength ( double  optimalFiberLength)
void OpenSim::Muscle::setPennationAngleAtOptimalFiberLength ( double  pennationAngle)
void OpenSim::Muscle::setPropertiesFromState ( const SimTK::State &  state)
overrideprotectedvirtual

Subclass should override; be sure to invoke 

Force::setPropertiesFromState() at the beginning of the overriding method.

Reimplemented from OpenSim::Force.

Reimplemented in OpenSim::Millard2012AccelerationMuscle, OpenSim::Millard2012EquilibriumMuscle, OpenSim::ActivationFiberLengthMuscle_Deprecated, and OpenSim::ActivationFiberLengthMuscle.

void OpenSim::Muscle::setTendonSlackLength ( double  tendonSlackLength)
virtual void OpenSim::Muscle::updateGeometry ( const SimTK::State &  s)
protectedvirtual
FiberVelocityInfo& OpenSim::Muscle::updFiberVelocityInfo ( const SimTK::State &  s) const
protected
MuscleDynamicsInfo& OpenSim::Muscle::updMuscleDynamicsInfo ( const SimTK::State &  s) const
protected
MuscleLengthInfo& OpenSim::Muscle::updMuscleLengthInfo ( const SimTK::State &  s) const
protected

Member Data Documentation

double OpenSim::Muscle::_maxIsometricForce
protected

to support deprecated muscles

double OpenSim::Muscle::_muscleWidth
protected

The assumed fixed muscle-width from which the fiber pennation angle is calculated.

double OpenSim::Muscle::_optimalFiberLength
protected
double OpenSim::Muscle::_pennationAngleAtOptimal
protected
double OpenSim::Muscle::_tendonSlackLength
protected

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