This class serves as a serializable ActiveForceLengthCurve, commonly used to model the active element in muscle models. More...

#include <ActiveForceLengthCurve.h>

Inheritance diagram for OpenSim::ActiveForceLengthCurve:

Public Member Functions
	ActiveForceLengthCurve ()
	The default constructor creates an active-force-length curve using the default property values and assigns a default name. More...

	ActiveForceLengthCurve (double minActiveNormFiberLength, double transitionNormFiberLength, double maxActiveNormFiberLength, double shallowAscendingSlope, double minimumValue)
	Constructs an active-force-length curve using the provided parameters and assigns a default name. More...

double	getMinActiveFiberLength () const

double	getTransitionFiberLength () const

double	getMaxActiveFiberLength () const

double	getShallowAscendingSlope () const

double	getMinValue () const

void	setActiveFiberLengths (double minActiveNormFiberLength, double transitionNormFiberLength, double maxActiveNormFiberLength, double shallowAscendingSlope)

void	setMinValue (double minimumValue)

double	calcValue (const SimTK::Vector &x) const override
	Implement the generic OpenSim::Function interface. More...

double	calcValue (double normFiberLength) const
	Evaluates the active-force-length curve at a normalized fiber length of 'normFiberLength'. More...

double	calcDerivative (double normFiberLength, int order) const
	Calculates the derivative of the active-force-length multiplier with respect to the normalized fiber length. More...

SimTK::Vec2	getCurveDomain () const
	Returns a SimTK::Vec2 containing the lower (0th element) and upper (1st element) bounds on the domain of the curve. More...

void	printMuscleCurveToCSVFile (const std::string &path)
	Generates a .csv file with a name that matches the curve name (e.g., "bicepsfemoris_ActiveForceLengthCurve.csv"). More...

void	ensureCurveUpToDate ()

Property declarations
These are the serializable properties associated with this class.
	OpenSim_DECLARE_PROPERTY (min_norm_active_fiber_length, double,"Normalized fiber length where the steep ascending limb starts")

	OpenSim_DECLARE_PROPERTY (transition_norm_fiber_length, double,"Normalized fiber length where the steep ascending limb transitions to the shallow ascending limb")

	OpenSim_DECLARE_PROPERTY (max_norm_active_fiber_length, double,"Normalized fiber length where the descending limb ends")

	OpenSim_DECLARE_PROPERTY (shallow_ascending_slope, double,"Slope of the shallow ascending limb")

	OpenSim_DECLARE_PROPERTY (minimum_value, double,"Minimum value of the active-force-length curve")

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

	Function (const Function &aFunction)

virtual	~Function ()

virtual void	init (Function *aFunction)

Function &	operator= (const Function &aFunction)

virtual double	calcDerivative (const std::vector< int > &derivComponents, const SimTK::Vector &x) const
	Calculate a partial derivative of this function at a particular point. More...

virtual int	getArgumentSize () const
	Get the number of components expected in the input vector. More...

virtual int	getMaxDerivativeOrder () const
	Get the maximum derivative order this Function object can calculate. More...

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 const VisibleObject *	getDisplayer () const
	Methods to support making the object displayable in the GUI or Visualizer Implemented only in few objects. 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	updateFromXMLNode (SimTK::Xml::Element &objectElement, int versionNumber)
	Use this method to deserialize an object from a SimTK::Xml::Element. 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

Additional Inherited Members
Static Public Member Functions inherited from OpenSim::Function
static Function *	makeFunctionOfType (Function *aFunction, const std::string &aNewTypeName)

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

Protected Member Functions inherited from OpenSim::Function
void	resetFunction ()
	This should be called whenever this object has been modified. More...

Protected Attributes inherited from OpenSim::Function
SimTK::Function *	_function

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 serves as a serializable ActiveForceLengthCurve, commonly used to model the active element in muscle models.

The active-force-length curve is dimensionless: force is normalized to maximum isometric force and length is normalized to resting fiber length. Five properties are used to construct a curve:

Parameters

minActiveNormFiberLength	The normalized fiber length where the steep ascending limb of the active-force-length curve transitions to the minimum value and has first and second derivatives of 0.
transitionNormFiberLength	The normalized fiber length where the steep ascending limb transitions to the shallow ascending limb.
maxActiveNormFiberLength	The normalized fiber length where the descending limb transitions to the minimum value and has first and second derivatives of 0.
shallowAscendingSlope	The slope of the shallow ascending limb.
minimumValue	The minimum value of the active-force-length curve. If you are using an equilibrium model, this value must be greater than 0, as a value of 0 will cause a singularity in the muscle dynamic equations.

Conditions

0 < minActiveNormFiberLength < transitionNormFiberLength < 1 < maxActiveNormFiberLength
0 <= shallowAscendingSlope < 1/(1-transitionNormFiberLength)
0 <= minimumValue

Default Parameter Values The default parameters have been chosen so that the resulting curve closely matches the active-force-length curve for human sarcomeres, as documented by Nigg and Herzog (1994). The descending limb has been adjusted to match the in-vitro human fiber data reported by Gollapudi and Lin (2009). The default shoulder value is set to 0.1. This relatively large value is used to ensure that muscle model dynamic equations with an active-force-length singularity do not take an unreasonable amount of time to simulate (simulation time grows as the value of the active-force-length curve approaches 0). Muscle model formulations that do not have this singularity (e.g., the Millard2012AccelerationMuscle model) can use a minimumValue of 0.

minActiveNormFiberLength ..... 0.4441
transitionNormFiberLength .... 0.73
maxActiveNormFiberLength ..... 1.8123
shallowAscendingSlope ........ 0.8616
minimumValue ................. 0.1

Example

ActiveForceLengthCurve falCurve1(0.44, 0.73, 1.8, 0.86, 0.1);
double falVal  = falCurve1.calcValue(1.0);
double dfalVal = falCurve1.calcDerivative(1.0, 1);

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

References

Gollapudi, S.K., Lin, D.C. (2009) Experimental determination of sarcomere force-length relationship in type-I human skeletal muscle fibers. Journal of Biomechanics 42(13), 2011–2016.
Nigg, B.M., Herzog, W. Biomechanics of the Musculo-skeletal System. Wiley, 1994.

Author: Matt Millard

Constructor & Destructor Documentation

OpenSim::ActiveForceLengthCurve::ActiveForceLengthCurve ( )

The default constructor creates an active-force-length curve using the default property values and assigns a default name.

OpenSim::ActiveForceLengthCurve::ActiveForceLengthCurve	(	double	minActiveNormFiberLength,
		double	transitionNormFiberLength,
		double	maxActiveNormFiberLength,
		double	shallowAscendingSlope,
		double	minimumValue
	)

Constructs an active-force-length curve using the provided parameters and assigns a default name.

Member Function Documentation

double OpenSim::ActiveForceLengthCurve::calcDerivative	(	double	normFiberLength,
		int	order
	)		const

Calculates the derivative of the active-force-length multiplier with respect to the normalized fiber length.

Parameters

normFiberLength	The normalized length of the muscle fiber.
order	The order of the derivative. Only values of 0, 1, and 2 are acceptable.

Returns: The derivative of the active-force-length curve with respect to the normalized fiber length.

double OpenSim::ActiveForceLengthCurve::calcValue ( const SimTK::Vector & x) const

inlineoverridevirtual

Implement the generic OpenSim::Function interface.

Reimplemented from OpenSim::Function.

double OpenSim::ActiveForceLengthCurve::calcValue ( double normFiberLength) const

Evaluates the active-force-length curve at a normalized fiber length of 'normFiberLength'.

void OpenSim::ActiveForceLengthCurve::ensureCurveUpToDate ( )

SimTK::Vec2 OpenSim::ActiveForceLengthCurve::getCurveDomain ( ) const

Returns a SimTK::Vec2 containing the lower (0th element) and upper (1st element) bounds on the domain of the curve.

Outside this domain, the curve is approximated using linear extrapolation.

Returns: The minimum and maximum value of the domain, x, of the curve y(x). Within this range, y(x) is a curve; outside this range, the function y(x) is a C2-continuous linear extrapolation.

double OpenSim::ActiveForceLengthCurve::getMaxActiveFiberLength ( ) const

Returns: The normalized fiber length where the descending limb of the active-force-length curve transitions to the minimum activation value and simultaneously achives first and second derivatives of 0.

double OpenSim::ActiveForceLengthCurve::getMinActiveFiberLength ( ) const

Returns: The normalized fiber length where the steep ascending limb of the active-force-length curve transitions to the minimum activation value and simultaneously achives a first and second derivative of 0.

double OpenSim::ActiveForceLengthCurve::getMinValue ( ) const

Returns: The minimum active-force-length value permitted in the simulation. This value must be non-zero for an equilibrium model.

double OpenSim::ActiveForceLengthCurve::getShallowAscendingSlope ( ) const

Returns: The slope of the shallow ascending limb (d active_force_length / d normalized_fiber_length).

double OpenSim::ActiveForceLengthCurve::getTransitionFiberLength ( ) const

Returns: The normalized fiber length where the steep ascending limb of the active-force-length curve transitions to the shallow ascending limb.

OpenSim::ActiveForceLengthCurve::OpenSim_DECLARE_PROPERTY	(	min_norm_active_fiber_length	,
		double	,
		"Normalized fiber length where the steep ascending limb starts"
	)

OpenSim::ActiveForceLengthCurve::OpenSim_DECLARE_PROPERTY	(	transition_norm_fiber_length	,
		double	,
		"Normalized fiber length where the steep ascending limb transitions to the shallow ascending limb"
	)

OpenSim::ActiveForceLengthCurve::OpenSim_DECLARE_PROPERTY	(	max_norm_active_fiber_length	,
		double	,
		"Normalized fiber length where the descending limb ends"
	)

OpenSim::ActiveForceLengthCurve::OpenSim_DECLARE_PROPERTY	(	shallow_ascending_slope	,
		double	,
		"Slope of the shallow ascending limb"
	)

OpenSim::ActiveForceLengthCurve::OpenSim_DECLARE_PROPERTY	(	minimum_value	,
		double	,
		"Minimum value of the active-force-length curve"
	)

void OpenSim::ActiveForceLengthCurve::printMuscleCurveToCSVFile ( const std::string & path)

Generates a .csv file with a name that matches the curve name (e.g., "bicepsfemoris_ActiveForceLengthCurve.csv").

This function is not const to permit the curve to be rebuilt if it is out-of-date with its properties.

Parameters

path	The full destination path. Note that forward slashes ('/') must be used and there should not be a slash after the last folder.

The file will contain the following data:

column: 1 | 2 |     3 |       4
  data: x | y | dy/dx | d2y/dx2

Samples will be taken from the linear extrapolation region (the region less than minActiveNormFiberLength), through the curve, out to the other linear extrapolation region (the region greater than maxActiveNormFiberLength). The width of each linear extrapolation region is 10% of the curve domain, or 0.1*(maxActiveNormFiberLength-minActiveNormFiberLength). The curve is sampled quite densely: the active-force-length .csv file will have 500+20 rows.

Example To read the .csv file into Matlab, you need to set csvread to ignore the header row. Since csvread is 0-indexed, the following example will begin reading the .csv file from the first column of the second row:

data = csvread('bicepsfemoris_ActiveForceLengthCurve.csv', 1, 0);

void OpenSim::ActiveForceLengthCurve::setActiveFiberLengths	(	double	minActiveNormFiberLength,
		double	transitionNormFiberLength,
		double	maxActiveNormFiberLength,
		double	shallowAscendingSlope
	)

Parameters

minActiveNormFiberLength	The normalized fiber length where the steep ascending limb of the active-force-length curve transitions to the minimum value and has first and second derivatives of 0.
transitionNormFiberLength	The normalized fiber length where the steep ascending limb transitions to the shallow ascending limb.
maxActiveNormFiberLength	The normalized fiber length where the descending limb transitions to the minimum value and has first and second derivatives of 0.
shallowAscendingSlope	The slope of the shallow ascending limb.

Conditions

0 < minActiveNormFiberLength < transitionNormFiberLength < 1 < maxActiveNormFiberLength
0 <= shallowAscendingSlope < 1/(1-transitionNormFiberLength)

void OpenSim::ActiveForceLengthCurve::setMinValue ( double minimumValue)

Parameters

minimumValue The minimum value of the active-force-length curve. If you are using an equilibrium model, this value must be greater than 0, as a value of 0 will cause a singularity in the muscle dynamic equations.

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

/home/fitze/repos/opensim/Branches/OpenSim32ForDoxygen/OpenSim/Actuators/ActiveForceLengthCurve.h

Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation