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rdMuscleZajac Class Reference

A class that represents a lumped parameter muscle in series with a linear tendon. More...

#include <rdMuscleZajac.h>

Inheritance diagram for rdMuscleZajac:

List of all members.

Public Member Functions
	rdMuscleZajac (int aQID=-1, int aNX=1, int aNY=2, int aNYP=0)
	Default constructor.
	rdMuscleZajac (IDOM_Element *aElement, int aNX=1, int aNY=2, int aNYP=0)
	Construct the actuator from an XML Element.
	rdMuscleZajac (const rdMuscleZajac &aActuator)
	Copy constructor.
virtual	~rdMuscleZajac ()
	Destructor.
virtual rdActuator *	copy () const
	Copy this actuator and return a pointer to the copy.
virtual rdActuator *	copy (IDOM_Element *aElement) const
	Copy this actuator and modify the copy so that it is consistent with a specified XML element node.
rdMuscleZajac &	operator= (const rdMuscleZajac &aActuator)
	Assignment operator.
virtual void	setControls (const double aX[])
	Set the controls.
virtual void	getControls (double rX[]) const
	Get the controls.
virtual void	setStates (const double aY[])
	Set the states.
virtual void	getStates (double rY[]) const
	Get the states.
void	setRiseTime (double aTime)
	Set the activation rise time.
double	getRiseTime () const
	Get the activation rise time.
void	setFallTime (double aTime)
	Set the activation fall time.
double	getFallTime () const
	Get the activation fall time.
void	setOptimalForce (double aForce)
	Set the optimal force of the muscle.
double	getOptimalForce () const
	Get the optimal force of the muscle.
void	setOptimalFiberLength (double aLength)
	Set the optimal muscle fiber length.
double	getOptimalFiberLength () const
	Get the optimal muscle fiber length.
void	setOptimalPennationAngle (double aAngle)
	Set the optimal muscle fiber pennation angle.
double	getOptimalPennationAngle () const
	Get the optimal muscle fiber pennation angle.
void	setTendonSlackLength (double aLength)
	Set the slack length of the tendon.
double	getTendonSlackLength () const
	Get the slack length of the tendon.
void	setMaxShorteningVelocity (double aVelocity)
	Set the maximum shortening velocity of the muscle.
double	getMaxShorteningVelocity () const
	Get the maximum shortening velocity of the muscle.
virtual void	promoteControlsToStates (const double aX[], double aDT)
	Set the activation level of this actuator equal to the neural excitation.
virtual void	computeActuation ()
	Compute all quantities necessary for applying the actuator force to the model.
virtual void	computeStateDerivatives (double rDYDT[])
	Compute the time derivatives of the states for this actuator.
virtual double	computeDFDT ()
	Compute the time derivative of actuator force.
virtual void	updateObject (bool aDeep=true)
	Update this object based on its XML node.
virtual void	updateNode (bool aDeep=true)
	Update the XML node representing this object.
virtual void	generateNode (IDOM_Element *aParent)
	Generate an XML node representing this object.
void	updateData ()
	Update the member data of this object based on its XML node.
Static Public Member Functions
double	ComputeForceLengthCurve (double aLmNorm)
	Compute the normalized isometric muscle force based on the force-length curve.
double	ComputeShorteningVelocity (double aFmNormIso, double aFmNorm)
	Compute the normalized shortening velocity of the contractile element.
Static Public Attributes
const char	PROP_RISE_TIME [] = "activation_rise_time"
const char	PROP_FALL_TIME [] = "activation_fall_time"
const char	PROP_OPTIMAL_FORCE [] = "optimal_force"
const char	PROP_OPTIMAL_FIBER_LENGTH [] = "optimal_fiber_length"
const char	PROP_OPTIMAL_PENNATION_ANGLE []
const char	PROP_TENDON_SLACK_LENGTH []
const char	PROP_MAX_SHORTENING_VELOCITY []
const double	C1 = 18.0
const double	C2 = 0.020833
const double	PE1 = 0.1
const double	SIG0 = 0.01
const double	LMNORMMAX = 1.6
const double	flcoef [][6]
const double	fvcoef [][6]
Protected Attributes
double	_x
	Excitation (control 0).
double	_a
	Activation level (state 0).
double	_tRise
	Rise time of muscle activation in seconds.
double	_tFall
	Fall time of muscle activation in seconds.
double	_fmOpt
	Optimal muscle force in Newtons.
double	_lmOpt
	Optimal muscle fiber length in meters.
double	_alphaOpt
	Optimal muscle pennation angle in degrees.
double	_vmMax
	Maximum muscle fiber shortening velocity in optimal fiber lengths per second.
double	_ltSlack
	Tendon slack length in meters.
double	_lmOptRecip
	Reciprocal of muscle length.
double	_width
	Muscle width in meters.
double	_widthSquared
	Muscle width squared.
double	_ktRecip
	Reciprocal of normalized tendon stiffness.
double	_ktLmOptRecip
	Reciprocal of normalized tendon stiffness times optimal fiber length.
double	_lmt
	Actuator length.
Private Member Functions
void	setNull ()
	Set the data members of this actuator to their null values.
void	copyData (const rdMuscleZajac &aActuator)
	Copy the member data of the specified actuator.

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Detailed Description

A class that represents a lumped parameter muscle in series with a linear tendon.

The muscle is comprised of three elements: the contractile element models the force-length-velocity properties of muscle; the series elastic element is in series with the contractile element an models the short-range elastic response of muscle; the parallel elastic element is in parallel with both the series elastic element and the contractile element and models the passive elastic properties of muscle.

For details concerning this model consult Zajac, F.E. (1989). ??. Reviews in Sports Science ??.

Controls (1): 0) excitation

States (2): 0) activation level 1) musculotendon force

Author:

Frank C. Anderson

Version:

1.0

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Constructor & Destructor Documentation

rdMuscleZajac::rdMuscleZajac (  IDOM_Element *  aElement, int  aNX = 1, int  aNY = 2, int  aNYP = 0 )

Construct the actuator from an XML Element. Parameters: aElement  XML element. aNX  Number of controls. aNY  Number of states. aNYP  Number of pseudo-states.

rdMuscleZajac::rdMuscleZajac (  const rdMuscleZajac &  aActuator  )

Copy constructor. Parameters: aActuator  Actuator to be copied.

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Member Function Documentation

double rdMuscleZajac::computeDFDT (   )  [virtual]

Compute the time derivative of actuator force. Returns: Time derivative of normalized muscle force.

double rdMuscleZajac::ComputeForceLengthCurve (  double  aLmNorm  )  [static]

Compute the normalized isometric muscle force based on the force-length curve. Parameters: aLmNorm  Normalized muscle force. Returns: Muscle (or sarcomere) force.

double rdMuscleZajac::ComputeShorteningVelocity (  double  aFmNormIso, double  aFmNorm )  [static]

Compute the normalized shortening velocity of the contractile element. To get the actual shortening velocity the returned quantity must be multiplied by the maximum shortening velocity. Parameters: aFmNormIsometric  Normalized force that would be generated by the muscle under isometric conditions. This value can be computed by calling computeForceLengthCurve(). aFmNorm  Normalized force currently being generated by the muscle. Returns: Contractile shortening velocity in optimal fibers per second. Positive values indicate shortening.

void rdMuscleZajac::computeStateDerivatives (  double  rDYDT[]  )  [virtual]

Compute the time derivatives of the states for this actuator. Parameters: rDYDT  Time derivatives of the states-- should have a length of at least the value returned by getNY(). See also: getNY() Reimplemented from rdActuator.

rdActuator * rdMuscleZajac::copy (  IDOM_Element *  aElement  )  const [virtual]

Copy this actuator and modify the copy so that it is consistent with a specified XML element node. The copy is constructed by first using the contructor for the IDOM_Element in order to establish the relationship of the rdForce object with the XML node. Then, the assignment operator is used to set all data members of the copy to the values of this object. Finally, the data members of the copy are updated from the IDOM_Elment using updateObject(). Parameters: aElement  XML element. Returns: Pointer to a copy of this actuator. Reimplemented from rdForce.

rdActuator * rdMuscleZajac::copy (   )  const [virtual]

Copy this actuator and return a pointer to the copy. The copy constructor for this class is used. Returns: Pointer to a copy of this actuator. Reimplemented from rdForce.

void rdMuscleZajac::generateNode (  IDOM_Element *  aParent  )  [virtual]

Generate an XML node representing this object. Parameters: aParent  Intended parent of the node to be generated. If aParent is NULL, the intent is for this object to serve as the root element of a new document. See also: rdObject::generateNode() Reimplemented from rdForce.

void rdMuscleZajac::getControls (  double  rX[]  )  const [virtual]

Get the controls. This actuator has 1 control: excitation. Parameters: rX  Control array- should have a length of at least 1. Reimplemented from rdForce.

double rdMuscleZajac::getFallTime (   )  const

Get the activation fall time. Returns: Fall time of activation dynamics.

double rdMuscleZajac::getMaxShorteningVelocity (   )  const

Get the maximum shortening velocity of the muscle. Returns: Maximum shortening velocity in optimal muscle fiber lengths per second- should be positive.

double rdMuscleZajac::getOptimalFiberLength (   )  const

Get the optimal muscle fiber length. Returns: Optimal muscle fiber length.

double rdMuscleZajac::getOptimalForce (   )  const

Get the optimal force of the muscle. Returns: Optimal muscle force.

double rdMuscleZajac::getOptimalPennationAngle (   )  const

Get the optimal muscle fiber pennation angle. Returns: Optimal muscle fiber pennation angle in degrees.

double rdMuscleZajac::getRiseTime (   )  const

Get the activation rise time. Returns: Rise time of activation dynamics.

void rdMuscleZajac::getStates (  double  rY[]  )  const [virtual]

Get the states. This actuator has 2 states: activation and actuator force. Parameters: rY  States array- should have a length of at least 2. Reimplemented from rdActuator.

double rdMuscleZajac::getTendonSlackLength (   )  const

Get the slack length of the tendon. Returns: Tendon slack length in meters.

rdMuscleZajac & rdMuscleZajac::operator= (  const rdMuscleZajac &  aActuator  )

Assignment operator. Returns: Reference to the altered object.

void rdMuscleZajac::setControls (  const double  aX[]  )  [virtual]

Set the controls. This actuator has 1 control: excitation. Parameters: aX  Control array- should have a length of at least 1. Reimplemented from rdForce.

void rdMuscleZajac::setFallTime (  double  aTime  )

Set the activation fall time. Parameters: aTime  Fall time of activation dynamics.

void rdMuscleZajac::setMaxShorteningVelocity (  double  aVelocity  )

Set the maximum shortening velocity of the muscle. Parameters: aVelocity  Maximum shortening velocity in optimal muscle fiber lengths per second- should be positive.

void rdMuscleZajac::setOptimalFiberLength (  double  aLength  )

Set the optimal muscle fiber length. Parameters: aLength  Optimal muscle fiber length in meters- should be positive.

void rdMuscleZajac::setOptimalForce (  double  aForce  )

Set the optimal force of the muscle. Parameters: aForce  Optimal muscle force.

void rdMuscleZajac::setOptimalPennationAngle (  double  aAngle  )

Set the optimal muscle fiber pennation angle. Note that during a simulation, the pennation angle of the muscle fibers changes. The optimal pennation angle is the pennation angle when the muscle is at its optimal muscle fiber length. The width of the muscle is assumed to be constant. The width is computed from the optimal pennation angle and the optimal muscle fiber length (width = lmOpt * sin(pennation)) every time this method is called. Parameters: aAngleDeg  Optimal pennation angle in degrees- should be positive.

void rdMuscleZajac::setRiseTime (  double  aTime  )

Set the activation rise time. Parameters: aTime  Rise time of activation dynamics.

void rdMuscleZajac::setStates (  const double  aY[]  )  [virtual]

Set the states. This actuator has 2 states: activation and actuator force. Parameters: aY  States array- should have a length of at least 2. Reimplemented from rdActuator.

void rdMuscleZajac::setTendonSlackLength (  double  aLength  )

Set the slack length of the tendon. Parameters: aLength  Tendon slack length in meters.

void rdMuscleZajac::updateData (   )

Update the member data of this object based on its XML node. Member objects (children) are not updated. Reimplemented from rdForce.

void rdMuscleZajac::updateNode (  bool  aDeep = true  )  [virtual]

Update the XML node representing this object. Parameters: aDeep  If true, update the XML node of this object AND the XML nodes of all class members that are rdObjects (child nodes); if false, update only the XML node of this object without updating the XML nodes of its children. Reimplemented from rdForce.

void rdMuscleZajac::updateObject (  bool  aDeep = true  )  [virtual]

Update this object based on its XML node. Parameters: aDeep  If true, update this object and all its child objects (that is, member variables that are rdObject's); if false, update only the member variables that are not rdObject's. Reimplemented from rdForce.

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Member Data Documentation

const char rdMuscleZajac::PROP_MAX_SHORTENING_VELOCITY [static]

Initial value: "max_shortening_velocity"

const char rdMuscleZajac::PROP_OPTIMAL_PENNATION_ANGLE [static]

Initial value: "optimal_pennation_angle"

const char rdMuscleZajac::PROP_TENDON_SLACK_LENGTH [static]

Initial value: "tendon_slack_length"

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

• rdMuscleZajac.h
• rdMuscleZajac.cpp

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