OpenSim::Muscle::MuscleLengthInfo Struct Reference

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...

#include <Muscle.h>

Public Member Functions
	MuscleLengthInfo ()

Public Attributes
double	fiberLength
double	fiberLengthAlongTendon
double	normFiberLength
double	tendonLength
double	normTendonLength
double	tendonStrain
double	pennationAngle
double	cosPennationAngle
double	sinPennationAngle
double	fiberPassiveForceLengthMultiplier
double	fiberActiveForceLengthMultiplier
SimTK::Vector	userDefinedLengthExtras

Friends
std::ostream &	operator<< (std::ostream &o, const MuscleLengthInfo &mli)

Detailed Description

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.

w.r.t. a fixed orientation of the tendon.

The function that populates this struct, calcMuscleLengthInfo, is called at a point when only the position and orientation of the system are known. This function is the first one that is called of the functions calcMuscleLengthInfo, calcFiberVelocityInfo and calcMuscleDynamicInfo. The velocity and acceleration of the muscle's path will not be known when this function is called.

NAME DIMENSION UNITS fiberLength length m fiberLengthAlongTendon length m [1] normFiberLength length/length m/m [2]

tendonLength length m normTendonLength length/length m/m [3] tendonStrain length/length m/m [4]

pennationAngle angle rad [5] cosPennationAngle NA NA sinPennationAngle NA NA

fiberPassiveForceLengthMultiplier force/force N/N [6] fiberActiveForceLengthMultiplier force/force N/N [7]

userDefinedLengthExtras NA NA [8]

[1] fiberLengthAlongTendon is the length of the muscle fiber as projected on the tendon.

[2] normFiberLength is the fiberLength normalized with respect to the optimalFiberLength,

normFiberLength = fiberLength / optimalFiberLength

N.B. It is assumed that the optimalFiberLength of a muscle is also its resting length.

[3] normTendonLength is the tendonLength normalized with respect to the tendonSlackLength

normTendonLength = tendonLength / tendonSlackLength

[4] Tendon strain is defined using the elongation of the material divided by its resting length. This is identical to the engineering definition of strain. Thus a tendonStrain of 0.01 means that the tendon is currently 1% longer than its resting length.

tendonStrain = (tendonLength-tendonSlackLength)/tendonSlackLength

[5] The orientation of the muscle fiber is defined w.r.t. a fixed orientation of the tendon. A pennation angle of 0 means that the fiber is collinear to the tendon. It is normal for the pennation angle to range between 0 and Pi/2 radians.

Fiber Tendon |===================||—————–| Pennation = 0

||——————-| Pennation = SimTK::Pi/3 (60 degrees)

[6] The fiberPassiveForceLengthMultiplier represents the elastic force the fiber generates normalized w.r.t. the maximum isometric force of the fiber. Is typically specified by a passiveForceLengthCurve.

[7] The fiberActiveForceLengthMultiplier is the scaling of the maximum force a fiber can generate as a function of its length. This term usually follows a curve that is zero at a normalized fiber length of 0.5, is 1 at a normalized fiber length of 1, and then zero again at a normalized fiber length of 1.5. This curve is generally an interpolation of experimental data.

[8] This vector is left for the muscle modeler to populate with any computationally expensive quantities that are computed in calcMuscleLengthInfo, and required for use in the user defined functions calcFiberVelocityInfo and calcMuscleDynamicsInfo. None of the parent classes make any assumptions about what is or isn't in this field

• use as necessary.

Constructor & Destructor Documentation

OpenSim::Muscle::MuscleLengthInfo::MuscleLengthInfo ( )

inline

Friends And Related Function Documentation

std::ostream& operator<< ( std::ostream &  o, const MuscleLengthInfo &  mli  )

friend

Member Data Documentation

double OpenSim::Muscle::MuscleLengthInfo::cosPennationAngle

double OpenSim::Muscle::MuscleLengthInfo::fiberActiveForceLengthMultiplier

double OpenSim::Muscle::MuscleLengthInfo::fiberLength

double OpenSim::Muscle::MuscleLengthInfo::fiberLengthAlongTendon

double OpenSim::Muscle::MuscleLengthInfo::fiberPassiveForceLengthMultiplier

double OpenSim::Muscle::MuscleLengthInfo::normFiberLength

double OpenSim::Muscle::MuscleLengthInfo::normTendonLength

double OpenSim::Muscle::MuscleLengthInfo::pennationAngle

double OpenSim::Muscle::MuscleLengthInfo::sinPennationAngle

double OpenSim::Muscle::MuscleLengthInfo::tendonLength

double OpenSim::Muscle::MuscleLengthInfo::tendonStrain

SimTK::Vector OpenSim::Muscle::MuscleLengthInfo::userDefinedLengthExtras

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

• /home/fitze/repos/opensim/Branches/OpenSim32ForDoxygen/OpenSim/Simulation/Model/Muscle.h