OpenSim  OpenSim 3.2
 All Classes Namespaces Functions Variables Typedefs Enumerations Enumerator Friends Pages
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

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