OpenSim::CMC Class Reference

Computed Muscle Control (CMC) is an optimization-based control technique designed specifically for controlling dynamic models that are actuated by redundant sets of actuators whose force-generating properties may be nonlinear and goverend by differential equaitions (as so have delays in force production). More...

#include <CMC.h>

Inheritance diagram for OpenSim::CMC:

List of all members.

Public Member Functions
	CMC ()
	Default Constructor.
	CMC (Model aModel, CMC_TaskSet aTaskSet)
	Contructor.
	CMC (const CMC &aCmc)
	Copy constructor.
	CMC (const std::string &aFileName, bool aUpdateFromXMLNode=true)
	Constructor from an XML Document.
virtual	~CMC ()
	Destructor.
void	setNull ()
	Set NULL values for all member variables.
CMC &	operator= (const CMC &aCmc)
	Assignment operator.
void	copyData (const CMC &aCmc)
	Copy the member variables of the specified controller.
virtual Object *	copy () const
	Copy this CMC controller and return a pointer to the copy.
Array< int > *	getParameterList ()
	Get the list of parameters in the control set that the controller is using to control the simulation.
SimTK::Optimizer *	getOptimizer () const
	Get the optimizer.
OptimizationTarget *	setOptimizationTarget (OptimizationTarget aTarget, SimTK::Optimizer aOptimizer)
	Set the optimization target for this controller.
OptimizationTarget *	getOptimizationTarget () const
	Get the optimization target for this controller.
void	setDT (double aDT)
	Set the requested integrator time step size.
double	getDT () const
	Get the requested integrator time step size.
void	setTargetTime (double aTime)
	Set the target time (or final time) for the controller.
double	getTargetTime () const
	Get the target time.
void	setTargetDT (double aDT)
	Set the target time step size.
double	getTargetDT () const
	Get the target time step size.
void	setCheckTargetTime (bool aTrueFalse)
	Set whether or not to check the target time.
bool	getCheckTargetTime () const
	Get whether or not to check the target time.
void	setActuatorForcePredictor (VectorFunctionForActuators *aPredictor)
	Set the predictor for actuator forces.
VectorFunctionForActuators *	getActuatorForcePredictor ()
	Get the predictor for actuator forces.
Storage *	getPositionErrorStorage () const
	Get the storage object for position errors.
Storage *	getVelocityErrorStorage () const
	Get the storage object for velocity errors.
Storage *	getStressTermWeightStorage () const
	Get the storage object for stress term weights.
bool	getUseReflexes () const
void	setUseVerbosePrinting (bool aTrueFalse)
	Set whether or not to use verbose printing.
bool	getUseVerbosePrinting () const
void	setUseCurvatureFilter (bool aTrueFalse)
	Set whether or not a curvature filter should be applied to the controls.
bool	getUseCurvatureFilter () const
	Get whether or not a curvature filter should be applied to the controls.
const CMC_TaskSet &	getTaskSet () const
CMC_TaskSet &	updTaskSet () const
ControlSet &	updControlSet ()
void	restoreConfiguration (SimTK::State &s, const SimTK::State &initialState)
	A utility method used to restore the coordinates and speeds to initial values.
void	obtainActuatorEquilibrium (SimTK::State &s, double tiReal, double dtReal, const Array< double > &x, bool hold)
	Obtain actuator equilibrium.
virtual void	computeControls (const SimTK::State &s, SimTK::Vector &controls) const
	Controller interface.
virtual void	computeInitialStates (SimTK::State &s, double &rTI)
	Compute the initial states for a simulation.
virtual void	computeControls (SimTK::State &s, ControlSet &rX)
	CMC algroithm.
virtual void	setActuators (Set< Actuator > &actuators)
	replace the current set of actuators with the provided set
virtual void	setupProperties ()
	Connect properties to local pointers.
Static Public Member Functions
static void	FilterControls (const SimTK::State &s, const ControlSet &aControlSet, double aDT, OpenSim::Array< double > &rControls, bool aVerbosePrinting)
	Filter the controls.
Protected Member Functions
virtual void	setup (Model &model)
	Model component interface that permits the controller to be "wired" up to its actuators.
virtual void	createSystem (SimTK::MultibodySystem &system) const
	Model component interface that creates underlying computational components in the SimTK::MultibodySystem.
virtual void	initState (SimTK::State &s)
Protected Attributes
SimTK::Optimizer *	_optimizer
	Optimizer.
OptimizationTarget *	_target
	Optimization target for computing the controls.
double	_dt
	Next integration step size that is to be taken by the integrator.
double	_lastDT
	Last integration step size that was taken before a new integration step size was set in order to step exactly to the target time.
bool	_restoreDT
	Flag indicating when the last integration step size should be restored.
double	_tf
	The target time is the time in the future (in normalized units) for which the controls have been calculated.
double	_targetDT
	The step size used to generate a new target time, once the old target time has been reached.
bool	_checkTargetTime
	Whether or not to check the target time.
Storage *	_pErrStore
	Storage object for the position errors.
Storage *	_vErrStore
	Storage object for the velocity errors.
Storage *	_stressTermWeightStore
	Storage object for the stress term weight.
ControlSet	_controlSet
Array< int >	_paramList
	List of parameters in the control set that are serving as the controls in the optimization problem.
bool	_verbose
	Flag to indicate whether to use verbose printing.
bool	_useCurvatureFilter
CMC_TaskSet *	_taskSet
VectorFunctionForActuators *	_predictor
	Vector function for estimating actuator forces over a specified time interval.
Array< double >	_f
	Array of actuator forces for achieving the desired accelerations.

Detailed Description

Computed Muscle Control (CMC) is an optimization-based control technique designed specifically for controlling dynamic models that are actuated by redundant sets of actuators whose force-generating properties may be nonlinear and goverend by differential equaitions (as so have delays in force production).

The cannonical example of such a dynamic system is the musculoskeletal system (human or animal), hence the name Computed Muscle Control.

For a complete description of the CMC algorithm consult the following references:

Anderson FC (2004). Method and system for dynamically filtering the motion of articulated bodies. Realistic Dynamics, Inc., US Patent No. 6,750,866 (Issue date: June 15, 2004).

DG, Anderson FC (2006). Using computed muscle control to generate forward dynamic simulations of human walking from experimental data. J Biomech 39: 1107-15.

DG, Anderson FC, Delp SL (2003). Generating forward dynamic simulations of movement using computed muscle control. J Biomech 36: 321-8.

Author:: Frank C. Anderson

Version:: 1.0

Constructor & Destructor Documentation

CMC::CMC ( )

Default Constructor.

CMC::CMC	(	Model *	aModel,
		CMC_TaskSet *	aTaskSet
	)

Contructor.

Parameters:

	aModel	Model that is to be controlled.
	aTaskSet	Set of tracking tasks.

CMC::CMC ( const CMC & aCmc )

Copy constructor.

CMC::CMC	(	const std::string &	aFileName,
		bool	aUpdateFromXMLNode = `true`
	)

Constructor from an XML Document.

CMC::~CMC ( ) [virtual]

Destructor.

Member Function Documentation

void CMC::computeControls	(	SimTK::State &	s,
		ControlSet &	controlSet
	)			`[virtual]`

CMC algroithm.

Compute the controls for a simulation.

The caller should send in an initial guess.

Parameters:

	s	state of system model
	rDT	Integration time step in normalized time that is to be taken next. Note that the controller can change the value of rDT.
	aT	Current time in normalized time.
	rControlSet	Control set used for the simulation. This method alters the control set in order to control the simulation.

void CMC::computeControls	(	const SimTK::State &	s,
		SimTK::Vector &	controls
	)			const `[virtual]`

Controller interface.

Implements OpenSim::TrackingController.

void CMC::computeInitialStates	(	SimTK::State &	s,
		double &	rTI
	)			`[virtual]`

Compute the initial states for a simulation.

The caller should send in an initial guess. The Qs and Us are set based on the desired trajectories. The actuator states are set by sovling for a desired set of actuator forces, and then letting the states come to equilibrium for those forces.

Parameters:

	rTI	Initial time in normalized time. Note this is changed to the time corresponding to the new initial states on return.
	s	Initial states.

Object * CMC::copy ( ) const [virtual]

Copy this CMC controller and return a pointer to the copy.

The copy constructor for this class is used. This method is called when a description of this controller is read in from an XML file.

Returns:: Pointer to a copy of this CMC controller.

Reimplemented from OpenSim::Object.

void CMC::copyData ( const CMC & aController )

Copy the member variables of the specified controller.

This method is called by the copy constructor of the Controller class.

Parameters:

aController

The controller whose data is to be copied.

Reimplemented from OpenSim::TrackingController.

void CMC::createSystem ( SimTK::MultibodySystem & system ) const [protected, virtual]

Model component interface that creates underlying computational components in the SimTK::MultibodySystem.

Create a Controller in the SimTK::System.

This includes adding states, creating measures, etc... required by the controller.

Reimplemented from OpenSim::Controller.

void CMC::FilterControls	(	const SimTK::State &	s,
		const ControlSet &	aControlSet,
		double	aDT,
		OpenSim::Array< double > &	rControls,
		bool	aVerbosePrinting
	)			`[static]`

Filter the controls.

This method was introduced as a means of attempting to reduce the sizes of residuals. Unfortunately, the approach was generally unsuccessful because the desired accelerations were not achieved.

Parameters:

	aControlSet	Set of controls computed by CMC.
	aDT	Current time window.
	rControls	Array of filtered controls.

VectorFunctionForActuators * CMC::getActuatorForcePredictor ( )

Get the predictor for actuator forces.

bool CMC::getCheckTargetTime ( ) const

Get whether or not to check the target time.

Returns:: True if the target time will be checked. False if the target time will not be checked.

See also:: setTargetTime()

double CMC::getDT ( ) const

Get the requested integrator time step size.

Returns:: Step size.

OptimizationTarget * CMC::getOptimizationTarget ( ) const

Get the optimization target for this controller.

Returns:: Current optimization target.

SimTK::Optimizer * CMC::getOptimizer ( ) const

Get the optimizer.

Returns:: Optimizer.

OpenSim::Array< int > * CMC::getParameterList ( )

Get the list of parameters in the control set that the controller is using to control the simulation.

Returns:: List of parameters in the control set serving as the controls.

Storage * CMC::getPositionErrorStorage ( ) const

Get the storage object for position errors.

Returns:: Storage of position errors.

Storage * CMC::getStressTermWeightStorage ( ) const

Get the storage object for stress term weights.

Returns:: Storage of stress term weights.

double CMC::getTargetDT ( ) const

Get the target time step size.

The target time step size is the step size used to compute a new target time, once the former target time has been reached by the integrator.

Returns:: Target time step size.

See also:: setTargetTime()

double CMC::getTargetTime ( ) const

Get the target time.

The target time is the time in the future for which the controls have been calculated. If an integrator is taking time steps prior to the target time, the controls should not have to be computed again.

Returns:: Time in the furture for which the controls have been computed.

See also:: getCheckTargetTime()

const CMC_TaskSet & CMC::getTaskSet ( ) const

bool CMC::getUseCurvatureFilter ( ) const

Get whether or not a curvature filter should be applied to the controls.

Returns:: True, if will filtered based on their curvature; false, if they will not be filtered.

bool OpenSim::CMC::getUseReflexes ( ) const

bool CMC::getUseVerbosePrinting ( ) const

Storage * CMC::getVelocityErrorStorage ( ) const

Get the storage object for velocity errors.

Returns:: Storage of velocity errors.

void CMC::initState ( SimTK::State & s ) [protected, virtual]

void CMC::obtainActuatorEquilibrium	(	SimTK::State &	s,
		double	tiReal,
		double	dtReal,
		const Array< double > &	x,
		bool	hold
	)

Obtain actuator equilibrium.

A series of long (e.g., 200 msec) integrations are performed to allow time-dependent actuators forces to reach equilibrium values.

Parameters:

	tiReal	Initial time expressed in real time units.
	dtReal	Duration of the time interval.
	x	Array of control values.
	y	Array of states.
	hold	Flag indicating whether or not to hold model coordinates constant (true) or let them change according to the desired trajectories (false).

CMC & CMC::operator= ( const CMC & TrackingController )

Assignment operator.

Parameters:

aController

The controller to be copied.

Returns:: Reference to the altered object.

Reimplemented from OpenSim::TrackingController.

void CMC::restoreConfiguration	(	SimTK::State &	s,
		const SimTK::State &	initialState
	)

A utility method used to restore the coordinates and speeds to initial values.

The states associated with actuators are not changed.

Parameters:

	nqnu	Sum of the number of coordinates and speeds (nq + nu).
	s	current state.
	initialState	initial state to be restored.

void CMC::setActuatorForcePredictor ( VectorFunctionForActuators * aPredictor )

Set the predictor for actuator forces.

void CMC::setActuators ( Set< Actuator > & actuators ) [virtual]

replace the current set of actuators with the provided set

Reimplemented from OpenSim::Controller.

void CMC::setCheckTargetTime ( bool aTrueFalse )

Set whether or not to check the target time.

Parameters:

aTrueFalse

If true, the target time will be checked. If false, the target time will not be checked.

See also:: setTargetTime()

void CMC::setDT ( double aDT )

Set the requested integrator time step size.

Parameters:

aDT

Step size (0.0 <= aDT).

void CMC::setNull ( void )

Set NULL values for all member variables.

Reimplemented from OpenSim::TrackingController.

OptimizationTarget * CMC::setOptimizationTarget	(	OptimizationTarget *	aTarget,
		SimTK::Optimizer *	aOptimizer
	)

Set the optimization target for this controller.

Parameters:

aTarget

Optimization target.

Returns:: Previous optimization target.

void CMC::setTargetDT ( double aDT )

Set the target time step size.

The target time step size is the step size used to compute a new target time, once the former target time has been reached by the integrator.

Parameters:

aDT

Target time step size. Must be greater than 1.0e-8.

See also:: setTargetTime()

void CMC::setTargetTime ( double aTargetTime )

Set the target time (or final time) for the controller.

The function of the controller is to compute a set of controls that are appropriate from the current time in a simulation to the target time of the controller. If an integrator is taking time steps prior to the target time, the controls should not have to be computed again.

Parameters:

aTargetTime

Time in the furture for which the controls have been computed.