OpenSim Moco  0.4.0
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OpenSim::DeGrooteFregly2016Muscle Class Reference

Description

This muscle model was published in De Groote et al.

2016. The parameters of the active force-length and force-velocity curves have been slightly modified from what was published to ensure the curves go through key points:

The fiber damping helps with numerically solving for fiber velocity at low activations or with low force-length multipliers, and is likely to be more useful with explicit fiber dynamics than implicit fiber dynamics (when support for fiber dynamics is added).

This class supports tendon compliance dynamics in both explicit and implicit form. Both forms of the dynamics use normalized tendon force as the state variable (rather than the typical fiber length state). The explicit form is handled through the usual Component dynamics interface. The implicit form introduces an additional discrete and cache SimTK::State variable for the derivative of normalized tendon force and muscle-tendon equilibrium residual respectively. The implicit form is only for use with solvers that support implicit dynamics (i.e. Moco) and cannot be used to perform a time-stepping forward simulation with Manager; use explicit mode for time-stepping.

Note
Normalized tendon force is bounded in the range [0, 5] in this class. The methods getMinNormalizedTendonForce() and getMaxNormalizedTendonForce() are available to access these bounds for use in custom solvers.
This class is still under active development and should be used with caution.

Departures from the Muscle base class

The documentation for Muscle::MuscleLengthInfo states that the optimalFiberLength of a muscle is also its resting length, but this is not true for this muscle: there is a non-zero passive fiber force at the optimal fiber length.

In the Muscle class, setIgnoreTendonCompliance() and setIngoreActivationDynamics() control modeling options, meaning these settings could theoretically be changed. However, for this class, the modeling option is ignored and the values of the ignore_tendon_compliance and ignore_activation_dynamics properties are used directly.

De Groote, F., Kinney, A. L., Rao, A. V., & Fregly, B. J. (2016). Evaluation of Direct Collocation Optimal Control Problem Formulations for Solving the Muscle Redundancy Problem. Annals of Biomedical Engineering, 44(10), 1–15. http://doi.org/10.1007/s10439-016-1591-9

Inheritance diagram for OpenSim::DeGrooteFregly2016Muscle:

#include <Moco/Moco/Components/DeGrooteFregly2016Muscle.h>

Public Member Functions

 OpenSim_DECLARE_PROPERTY (activation_time_constant, double, "Smaller value means activation can change more rapidly (units: " "seconds).")
 
 OpenSim_DECLARE_PROPERTY (deactivation_time_constant, double, "Smaller value means activation can decrease more rapidly " "(units: seconds).")
 
 OpenSim_DECLARE_PROPERTY (default_activation, double, "Value of activation in the default state returned by " "initSystem().")
 
 OpenSim_DECLARE_PROPERTY (default_normalized_tendon_force, double, "Value of normalized tendon force in the default state returned by " "initSystem().")
 
 OpenSim_DECLARE_PROPERTY (active_force_width_scale, double, "Scale factor for the width of the active force-length curve. " "Larger values make the curve wider. Default: 1.0.")
 
 OpenSim_DECLARE_PROPERTY (fiber_damping, double, "The linear damping of the fiber. Default: 0.")
 
 OpenSim_DECLARE_PROPERTY (ignore_passive_fiber_force, bool, "Make the passive fiber force 0. Default: false.")
 
 OpenSim_DECLARE_PROPERTY (passive_fiber_strain_at_one_norm_force, double, "Fiber strain when the passive fiber force is 1 normalized force. " "Default: 0.6.")
 
 OpenSim_DECLARE_PROPERTY (tendon_strain_at_one_norm_force, double, "Tendon strain at a tension of 1 normalized force. " "Default: 0.049.")
 
 OpenSim_DECLARE_PROPERTY (tendon_compliance_dynamics_mode, std::string, "The dynamics method used to enforce tendon compliance dynamics. " "Options: 'explicit' or 'implicit'. Default: 'explicit'. ")
 
 OpenSim_DECLARE_OUTPUT (implicitresidual_normalized_tendon_force, double, getImplicitResidualNormalizedTendonForce, SimTK::Stage::Dynamics)
 
 OpenSim_DECLARE_OUTPUT (implicitenabled_normalized_tendon_force, bool, getImplicitEnabledNormalizedTendonForce, SimTK::Stage::Model)
 
 OpenSim_DECLARE_OUTPUT (statebounds_normalized_tendon_force, SimTK::Vec2, getBoundsNormalizedTendonForce, SimTK::Stage::Model)
 
Set methods.

If ignore_tendon_compliance is true, this sets nothing.

void setNormalizedTendonForce (SimTK::State &s, double normTendonForce) const
 

Protected Member Functions

Component interface
void extendFinalizeFromProperties () override
 
void extendAddToSystem (SimTK::MultibodySystem &system) const override
 
void extendInitStateFromProperties (SimTK::State &s) const override
 
void extendSetPropertiesFromState (const SimTK::State &s) override
 
void computeStateVariableDerivatives (const SimTK::State &s) const override
 
Actuator interface
double computeActuation (const SimTK::State &s) const override
 

Muscle interface

double getActivation (const SimTK::State &s) const override
 If ignore_activation_dynamics is true, this gets excitation instead.
 
void setActivation (SimTK::State &s, double activation) const override
 If ignore_activation_dynamics is true, this sets excitation instead.
 
void computeInitialFiberEquilibrium (SimTK::State &s) const override
 Fiber velocity is assumed to be 0.
 
double calcInextensibleTendonActiveFiberForce (SimTK::State &, double) const override
 
void calcMuscleLengthInfo (const SimTK::State &s, MuscleLengthInfo &mli) const override
 
void calcFiberVelocityInfo (const SimTK::State &s, FiberVelocityInfo &fvi) const override
 
void calcMuscleDynamicsInfo (const SimTK::State &s, MuscleDynamicsInfo &mdi) const override
 
void calcMusclePotentialEnergyInfo (const SimTK::State &s, MusclePotentialEnergyInfo &mpei) const override
 

Get methods.

bool getImplicitEnabledNormalizedTendonForce (const SimTK::State &) const
 We don't need the state, but the state parameter is a requirement of Output functions. More...
 
double getImplicitResidualNormalizedTendonForce (const SimTK::State &s) const
 Compute the muscle-tendon force equilibrium residual value when using implicit contraction dynamics with normalized tendon force as the state. More...
 
double getNormalizedTendonForce (const SimTK::State &s) const
 If ignore_tendon_compliance is true, this gets normalized fiber force along the tendon instead. More...
 
double getNormalizedTendonForceDerivative (const SimTK::State &s) const
 If integration_mode is 'implicit', this gets the discrete variable tendon force derivative value. More...
 
double getEquilibriumResidual (const SimTK::State &s) const
 The residual (i.e. More...
 
double getLinearizedEquilibriumResidualDerivative (const SimTK::State &s) const
 The residual (i.e. More...
 
SimTK::Vec2 getBoundsNormalizedTendonForce (const SimTK::State &) const
 The first element of the Vec2 is the lower bound, and the second is the upper bound. More...
 
static std::string getActivationStateName ()
 
static std::string getNormalizedTendonForceStateName ()
 
static std::string getImplicitDynamicsDerivativeName ()
 
static std::string getImplicitDynamicsResidualName ()
 
static double getMinNormalizedTendonForce ()
 
static double getMaxNormalizedTendonForce ()
 

Calculation methods.

These functions compute the values of normalized/dimensionless curves, their derivatives and integrals, and other quantities of the muscle.

These do not depend on a SimTK::State.

SimTK::Real calcActiveForceLengthMultiplier (const SimTK::Real &normFiberLength) const
 The active force-length curve is the sum of 3 Gaussian-like curves. More...
 
SimTK::Real calcActiveForceLengthMultiplierDerivative (const SimTK::Real &normFiberLength) const
 The derivative of the active force-length curve with respect to normalized fiber length. More...
 
SimTK::Real calcPassiveForceMultiplier (const SimTK::Real &normFiberLength) const
 This is the passive force-length curve. More...
 
SimTK::Real calcPassiveForceMultiplierDerivative (const SimTK::Real &normFiberLength) const
 This is the derivative of the passive force-length curve with respect to the normalized fiber length. More...
 
SimTK::Real calcPassiveForceMultiplierIntegral (const SimTK::Real &normFiberLength) const
 This is the integral of the passive force-length curve with respect to the normalized fiber length. More...
 
SimTK::Real calcTendonForceMultiplier (const SimTK::Real &normTendonLength) const
 The normalized tendon force as a function of normalized tendon length. More...
 
SimTK::Real calcTendonForceMultiplierDerivative (const SimTK::Real &normTendonLength) const
 This is the derivative of the tendon-force length curve with respect to normalized tendon length. More...
 
SimTK::Real calcTendonForceMultiplierIntegral (const SimTK::Real &normTendonLength) const
 This is the integral of the tendon-force length curve with respect to normalized tendon length. More...
 
SimTK::Real calcTendonForceLengthInverseCurve (const SimTK::Real &normTendonForce) const
 This is the inverse of the tendon force-length curve, and returns the normalized tendon length as a function of the normalized tendon force. More...
 
SimTK::Real calcTendonForceLengthInverseCurveDerivative (const SimTK::Real &derivNormTendonForce, const SimTK::Real &normTendonLength) const
 This is the derivative of the inverse tendon-force length. More...
 
void calcFiberForce (const SimTK::Real &activation, const SimTK::Real &activeForceLengthMultiplier, const SimTK::Real &forceVelocityMultiplier, const SimTK::Real &normPassiveFiberForce, const SimTK::Real &normFiberVelocity, SimTK::Real &activeFiberForce, SimTK::Real &conPassiveFiberForce, SimTK::Real &nonConPassiveFiberForce, SimTK::Real &totalFiberForce) const
 This computes both the total fiber force and the individual components of fiber force (active, conservative passive, and non-conservative passive). More...
 
SimTK::Real calcFiberStiffness (const SimTK::Real &activation, const SimTK::Real &normFiberLength, const SimTK::Real &fiberVelocityMultiplier) const
 The stiffness of the fiber in the direction of the fiber. More...
 
SimTK::Real calcTendonStiffness (const SimTK::Real &normTendonLength) const
 The stiffness of the tendon in the direction of the tendon. More...
 
SimTK::Real calcMuscleStiffness (const SimTK::Real &tendonStiffness, const SimTK::Real &fiberStiffnessAlongTendon) const
 The stiffness of the whole musculotendon unit in the direction of the tendon. More...
 
SimTK::Real calcPartialPennationAnglePartialFiberLength (const SimTK::Real &fiberLength) const
 The derivative of pennation angle with respect to fiber length. More...
 
SimTK::Real calcPartialFiberForceAlongTendonPartialFiberLength (const SimTK::Real &fiberForce, const SimTK::Real &fiberStiffness, const SimTK::Real &sinPennationAngle, const SimTK::Real &cosPennationAngle, const SimTK::Real &partialPennationAnglePartialFiberLength) const
 The derivative of the fiber force along the tendon with respect to fiber length. More...
 
SimTK::Real calcFiberStiffnessAlongTendon (const SimTK::Real &fiberLength, const SimTK::Real &partialFiberForceAlongTendonPartialFiberLength, const SimTK::Real &sinPennationAngle, const SimTK::Real &cosPennationAngle, const SimTK::Real &partialPennationAnglePartialFiberLength) const
 The derivative of the fiber force along the tendon with respect to the fiber length along the tendon. More...
 
SimTK::Real calcPartialTendonLengthPartialFiberLength (const SimTK::Real &fiberLength, const SimTK::Real &sinPennationAngle, const SimTK::Real &cosPennationAngle, const SimTK::Real &partialPennationAnglePartialFiberLength) const
 
SimTK::Real calcPartialTendonForcePartialFiberLength (const SimTK::Real &tendonStiffness, const SimTK::Real &fiberLength, const SimTK::Real &sinPennationAngle, const SimTK::Real &cosPennationAngle) const
 
SimTK::Real calcEquilibriumResidual (const SimTK::Real &tendonForce, const SimTK::Real &fiberForceAlongTendon) const
 The residual (i.e. More...
 
SimTK::Real calcLinearizedEquilibriumResidualDerivative (const SimTK::Real muscleTendonVelocity, const SimTK::Real &fiberVelocityAlongTendon, const SimTK::Real &tendonStiffness, const SimTK::Real &fiberStiffnessAlongTendon) const
 The residual (i.e. More...
 
static SimTK::Real calcForceVelocityMultiplier (const SimTK::Real &normFiberVelocity)
 The parameters of this curve are not modifiable, so this function is static. More...
 
static SimTK::Real calcForceVelocityInverseCurve (const SimTK::Real &forceVelocityMult)
 This is the inverse of the force-velocity multiplier function, and returns the normalized fiber velocity (in [-1, 1]) as a function of the force-velocity multiplier. More...
 

Utilities

DataTable exportFiberLengthCurvesToTable (const SimTK::Vector &normFiberLengths=SimTK::Vector()) const
 Export the active force-length multiplier and passive force multiplier curves to a DataTable. More...
 
DataTable exportFiberVelocityMultiplierToTable (const SimTK::Vector &normFiberVelocities=SimTK::Vector()) const
 Export the fiber force-velocity multiplier curve to a DataTable. More...
 
DataTable exportTendonForceMultiplierToTable (const SimTK::Vector &normTendonLengths=SimTK::Vector()) const
 Export the fiber tendon force multiplier curve to a DataTable. More...
 
void printCurvesToSTOFiles (const std::string &directory=".") const
 Print the muscle curves to STO files. More...
 
static void replaceMuscles (Model &model, bool allowUnsupportedMuscles=false)
 Replace muscles of other types in the model with muscles of this type. More...
 

Member Function Documentation

◆ calcActiveForceLengthMultiplier()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcActiveForceLengthMultiplier ( const SimTK::Real &  normFiberLength) const
inline

The active force-length curve is the sum of 3 Gaussian-like curves.

The width of the curve can be adjusted via the active_force_width_scale property.

◆ calcActiveForceLengthMultiplierDerivative()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcActiveForceLengthMultiplierDerivative ( const SimTK::Real &  normFiberLength) const
inline

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

This curve is based on the derivative of the Gaussian-like curve used in calcActiveForceLengthMultiplier(). The active_force_width_scale property also affects the value of the derivative curve.

◆ calcEquilibriumResidual()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcEquilibriumResidual ( const SimTK::Real &  tendonForce,
const SimTK::Real &  fiberForceAlongTendon 
) const
inline

The residual (i.e.

error) in the muscle-tendon equilibrium equation: residual = tendonForce - fiberForce * cosPennationAngle

◆ calcFiberForce()

void OpenSim::DeGrooteFregly2016Muscle::calcFiberForce ( const SimTK::Real &  activation,
const SimTK::Real &  activeForceLengthMultiplier,
const SimTK::Real &  forceVelocityMultiplier,
const SimTK::Real &  normPassiveFiberForce,
const SimTK::Real &  normFiberVelocity,
SimTK::Real &  activeFiberForce,
SimTK::Real &  conPassiveFiberForce,
SimTK::Real &  nonConPassiveFiberForce,
SimTK::Real &  totalFiberForce 
) const
inline

This computes both the total fiber force and the individual components of fiber force (active, conservative passive, and non-conservative passive).

Note
based on Millard2012EquilibriumMuscle::calcFiberForce().

◆ calcFiberStiffness()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcFiberStiffness ( const SimTK::Real &  activation,
const SimTK::Real &  normFiberLength,
const SimTK::Real &  fiberVelocityMultiplier 
) const
inline

The stiffness of the fiber in the direction of the fiber.

This includes both active and passive force contributions to stiffness from the muscle fiber.

Note
based on Millard2012EquilibriumMuscle::calcFiberStiffness().

◆ calcFiberStiffnessAlongTendon()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcFiberStiffnessAlongTendon ( const SimTK::Real &  fiberLength,
const SimTK::Real &  partialFiberForceAlongTendonPartialFiberLength,
const SimTK::Real &  sinPennationAngle,
const SimTK::Real &  cosPennationAngle,
const SimTK::Real &  partialPennationAnglePartialFiberLength 
) const
inline

The derivative of the fiber force along the tendon with respect to the fiber length along the tendon.

Note
based on Millard2012EquilibriumMuscle::calc_DFiberForceAT_DFiberLengthAT.

◆ calcForceVelocityInverseCurve()

static SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcForceVelocityInverseCurve ( const SimTK::Real &  forceVelocityMult)
inlinestatic

This is the inverse of the force-velocity multiplier function, and returns the normalized fiber velocity (in [-1, 1]) as a function of the force-velocity multiplier.

◆ calcForceVelocityMultiplier()

static SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcForceVelocityMultiplier ( const SimTK::Real &  normFiberVelocity)
inlinestatic

The parameters of this curve are not modifiable, so this function is static.

Domain: [-1, 1] Range: [0, 1.794]

◆ calcLinearizedEquilibriumResidualDerivative()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcLinearizedEquilibriumResidualDerivative ( const SimTK::Real  muscleTendonVelocity,
const SimTK::Real &  fiberVelocityAlongTendon,
const SimTK::Real &  tendonStiffness,
const SimTK::Real &  fiberStiffnessAlongTendon 
) const
inline

The residual (i.e.

error) in the time derivative of the linearized muscle-tendon equilibrium equation (Millard et al. 2013, equation A6): residual = fiberStiffnessAlongTendon * fiberVelocityAlongTendon - tendonStiffness * (muscleTendonVelocity - fiberVelocityAlongTendon)

◆ calcMuscleStiffness()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcMuscleStiffness ( const SimTK::Real &  tendonStiffness,
const SimTK::Real &  fiberStiffnessAlongTendon 
) const
inline

The stiffness of the whole musculotendon unit in the direction of the tendon.

Note
based on Millard2012EquilibriumMuscle.

◆ calcPartialFiberForceAlongTendonPartialFiberLength()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcPartialFiberForceAlongTendonPartialFiberLength ( const SimTK::Real &  fiberForce,
const SimTK::Real &  fiberStiffness,
const SimTK::Real &  sinPennationAngle,
const SimTK::Real &  cosPennationAngle,
const SimTK::Real &  partialPennationAnglePartialFiberLength 
) const
inline

The derivative of the fiber force along the tendon with respect to fiber length.

Note
based on Millard2012EquilibriumMuscle::calc_DFiberForceAT_DFiberLength().

◆ calcPartialPennationAnglePartialFiberLength()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcPartialPennationAnglePartialFiberLength ( const SimTK::Real &  fiberLength) const
inline

The derivative of pennation angle with respect to fiber length.

Note
based on MuscleFixedWidthPennationModel::calc_DPennationAngle_DFiberLength().

◆ calcPassiveForceMultiplier()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcPassiveForceMultiplier ( const SimTK::Real &  normFiberLength) const
inline

This is the passive force-length curve.

The curve becomes negative below the minNormFiberLength.

We modified this equation from that in the supplementary materials of De Groote et al., 2016, which is the same function used in Thelen2003Muscle. The version in the supplementary materials passes through y = 0 at x = 1.0 and allows for negative forces. We do not want negative forces within the allowed range of fiber lengths, so we modified the equation to pass through y = 0 at x = 0.2. (This is not an issue for Thelen2003Muscle because the curve is not smooth, and returns 0 for lengths less than optimal fiber length.)

◆ calcPassiveForceMultiplierDerivative()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcPassiveForceMultiplierDerivative ( const SimTK::Real &  normFiberLength) const
inline

This is the derivative of the passive force-length curve with respect to the normalized fiber length.

◆ calcPassiveForceMultiplierIntegral()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcPassiveForceMultiplierIntegral ( const SimTK::Real &  normFiberLength) const
inline

This is the integral of the passive force-length curve with respect to the normalized fiber length.

◆ calcTendonForceLengthInverseCurve()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcTendonForceLengthInverseCurve ( const SimTK::Real &  normTendonForce) const
inline

This is the inverse of the tendon force-length curve, and returns the normalized tendon length as a function of the normalized tendon force.

◆ calcTendonForceLengthInverseCurveDerivative()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcTendonForceLengthInverseCurveDerivative ( const SimTK::Real &  derivNormTendonForce,
const SimTK::Real &  normTendonLength 
) const
inline

This is the derivative of the inverse tendon-force length.

Given the derivative of normalized tendon force and normalized tendon length, this returns normalized tendon velocity.

◆ calcTendonForceMultiplier()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcTendonForceMultiplier ( const SimTK::Real &  normTendonLength) const
inline

The normalized tendon force as a function of normalized tendon length.

Note that this curve does not go through (1, 0); when normTendonLength=1, this function returns a slightly negative number.

◆ calcTendonForceMultiplierDerivative()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcTendonForceMultiplierDerivative ( const SimTK::Real &  normTendonLength) const
inline

This is the derivative of the tendon-force length curve with respect to normalized tendon length.

◆ calcTendonForceMultiplierIntegral()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcTendonForceMultiplierIntegral ( const SimTK::Real &  normTendonLength) const
inline

This is the integral of the tendon-force length curve with respect to normalized tendon length.

◆ calcTendonStiffness()

SimTK::Real OpenSim::DeGrooteFregly2016Muscle::calcTendonStiffness ( const SimTK::Real &  normTendonLength) const
inline

The stiffness of the tendon in the direction of the tendon.

Note
based on Millard2012EquilibriumMuscle.

◆ exportFiberLengthCurvesToTable()

DataTable OpenSim::DeGrooteFregly2016Muscle::exportFiberLengthCurvesToTable ( const SimTK::Vector &  normFiberLengths = SimTK::Vector()) const

Export the active force-length multiplier and passive force multiplier curves to a DataTable.

If the normFiberLengths argument is omitted, we use createVectorLinspace(200, minNormFiberLength, maxNormFiberLength).

◆ exportFiberVelocityMultiplierToTable()

DataTable OpenSim::DeGrooteFregly2016Muscle::exportFiberVelocityMultiplierToTable ( const SimTK::Vector &  normFiberVelocities = SimTK::Vector()) const

Export the fiber force-velocity multiplier curve to a DataTable.

If the normFiberVelocities argument is omitted, we use createVectorLinspace(200, -1.1, 1.1).

◆ exportTendonForceMultiplierToTable()

DataTable OpenSim::DeGrooteFregly2016Muscle::exportTendonForceMultiplierToTable ( const SimTK::Vector &  normTendonLengths = SimTK::Vector()) const

Export the fiber tendon force multiplier curve to a DataTable.

If the normFiberVelocities argument is omitted, we use createVectorLinspace(200, 0.95, 1 + <strain at 1 norm force>)

◆ getBoundsNormalizedTendonForce()

SimTK::Vec2 OpenSim::DeGrooteFregly2016Muscle::getBoundsNormalizedTendonForce ( const SimTK::State &  ) const
inline

The first element of the Vec2 is the lower bound, and the second is the upper bound.

We don't need the state, but the state parameter is a requirement of Output functions.

◆ getEquilibriumResidual()

double OpenSim::DeGrooteFregly2016Muscle::getEquilibriumResidual ( const SimTK::State &  s) const
inline

The residual (i.e.

error) in the muscle-tendon equilibrium equation: residual = tendonForce - fiberForce * cosPennationAngle

◆ getImplicitEnabledNormalizedTendonForce()

bool OpenSim::DeGrooteFregly2016Muscle::getImplicitEnabledNormalizedTendonForce ( const SimTK::State &  ) const
inline

We don't need the state, but the state parameter is a requirement of Output functions.

◆ getImplicitResidualNormalizedTendonForce()

double OpenSim::DeGrooteFregly2016Muscle::getImplicitResidualNormalizedTendonForce ( const SimTK::State &  s) const

Compute the muscle-tendon force equilibrium residual value when using implicit contraction dynamics with normalized tendon force as the state.

◆ getLinearizedEquilibriumResidualDerivative()

double OpenSim::DeGrooteFregly2016Muscle::getLinearizedEquilibriumResidualDerivative ( const SimTK::State &  s) const
inline

The residual (i.e.

error) in the time derivative of the linearized muscle-tendon equilibrium equation (Millard et al. 2013, equation A6): residual = fiberStiffnessAlongTendon * fiberVelocityAlongTendon - tendonStiffness * (muscleTendonVelocity - fiberVelocityAlongTendon)

◆ getNormalizedTendonForce()

double OpenSim::DeGrooteFregly2016Muscle::getNormalizedTendonForce ( const SimTK::State &  s) const
inline

If ignore_tendon_compliance is true, this gets normalized fiber force along the tendon instead.

◆ getNormalizedTendonForceDerivative()

double OpenSim::DeGrooteFregly2016Muscle::getNormalizedTendonForceDerivative ( const SimTK::State &  s) const
inline

If integration_mode is 'implicit', this gets the discrete variable tendon force derivative value.

If integration_mode is 'explicit', this gets the value returned by getStateVariableDerivativeValue() for the 'normalized_tendon_force' state. If ignore_tendon_compliance is false, this returns zero.

◆ printCurvesToSTOFiles()

void OpenSim::DeGrooteFregly2016Muscle::printCurvesToSTOFiles ( const std::string &  directory = ".") const

Print the muscle curves to STO files.

The files will be named as <muscle-name>_<curve_type>.sto.

Parameters
directoryThe directory to which the data files should be written. Do NOT include the filename. By default, the files are printed to the current working directory.

◆ replaceMuscles()

static void OpenSim::DeGrooteFregly2016Muscle::replaceMuscles ( Model &  model,
bool  allowUnsupportedMuscles = false 
)
static

Replace muscles of other types in the model with muscles of this type.

Currently, only Millard2012EquilibriumMuscles and Thelen2003Muscles are replaced. If the model has muscles of other types, an exception is thrown unless allowUnsupportedMuscles is true. Since the DeGrooteFregly2016Muscle implements tendon compliance dynamics with normalized tendon force as the state variable, this function ignores the 'default_fiber_length' property in replaced muscles.

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