Description

A MocoParameter allows you to optimize property values in an OpenSim Model.

To describe this parameter, you must provide the name of the property you want to optimize and the path to the component in the model where the property exists. If the property is not a scalar, then you must also provide the element index of the property you want to optimize. To optimize multiple elements of a non-scalar property, use multiple MocoParameters. By specifying multiple component paths, you can optimize the same property in multiple components (each property will have the same value, as determined by this parameter). The following property types are currently supported:

double
Vec3
Vec6

List properties are not currently supported.

The name you give to a MocoParameter does not need to match the name of its model property.

Create a MocoParameter from a property in the model:

MocoParameter p0;
p0.setName("torso_mass");
p0.appendComponentPath("torso");
p0.setParameterName("mass");
MocoBounds massBounds(60, 80);
p0.setBounds(massBounds);

Using the convenience constructor:

MocoParameter p0("torso_mass", "torso", "mass", MocoBounds(60, 80));

Here is a Matlab example of optimizing the optimal fiber length of a muscle:

study = MocoStudy();
problem = study.updProblem();
param = MocoParameter('my_param_name', /forceset/soleus_r', 'optimal_fiber_length', ...
MocoBounds(0.04, 0.06));
problem.addParameter(param);

The generic constructor can be used for more complex MocoParameter assignments. Here, we create a MocoParameter for the y-position of the mass center of three different rigid bodies in the model:

int propertyElt = 1; // y-position is the second element of the mass_center
std::vector<std::string> componentPaths = {"pelvis", "thigh", "shank"};
MocoParameter y_com("y_com", componentPaths, "mass_center", 
        MocoBounds(-0.05, 0.05), propertyElt);

For developers: Every time the problem is solved, a copy of this parameter is used. An individual instance of a parameter is only ever used in a single problem. Therefore, there is no need to clear cache variables that you create in initializeImpl(). Also, information stored in this parameter does not persist across multiple solves. Lastly, a MocoParameter may be applied to multiple models at once, as long as the value described in the MocoParameter exists and initializeOnModel() is called on all models of interest.

Inheritance diagram for OpenSim::MocoParameter:

#include <Moco/Moco/MocoParameter.h>

Public Member Functions
	MocoParameter (const std::string &name, const std::vector< std::string > &componentPaths, const std::string &propertyName, const MocoBounds &, const int &propertyElt)
	This is a generic constructor that supports applying this parameter to multiple components and to non-scalar properties. More...

	MocoParameter (const std::string &name, const std::string &componentPath, const std::string &propertyName, const MocoBounds &)

	MocoParameter (const std::string &name, const std::string &componentPath, const std::string &propertyName, const MocoBounds &, const int &propertyElt)

	MocoParameter (const std::string &name, const std::vector< std::string > &componentPaths, const std::string &propertyName, const MocoBounds &)

MocoBounds	getBounds () const

std::string	getPropertyName () const

std::vector< std::string >	getComponentPaths () const

void	setBounds (const MocoBounds &bounds)

void	setPropertyName (const std::string &propertyName)

void	appendComponentPath (const std::string &componentPath)

void	initializeOnModel (Model &model) const
	For use by solvers. More...

void	applyParameterToModelProperties (const double &value) const
	Set the value of the stored model properties, which may include properties from multiple models. More...

void	printDescription (std::ostream &stream=std::cout) const
	Print the name, property name, component paths, property element (if it exists), and bounds for this parameter. More...

Constructor & Destructor Documentation

◆ MocoParameter()

OpenSim::MocoParameter::MocoParameter	(	const std::string &	name,
		const std::vector< std::string > &	componentPaths,
		const std::string &	propertyName,
		const MocoBounds &	,
		const int &	propertyElt
	)

This is a generic constructor that supports applying this parameter to multiple components and to non-scalar properties.

Specifying propertyElt as -1 is treated as not specifying a property element.

Member Function Documentation

◆ applyParameterToModelProperties()

void OpenSim::MocoParameter::applyParameterToModelProperties ( const double & value ) const

Set the value of the stored model properties, which may include properties from multiple models.

◆ getBounds()

MocoBounds OpenSim::MocoParameter::getBounds ( ) const

inline

Note: the return value is constructed fresh on every call from the internal property. Avoid repeated calls to this function.

◆ initializeOnModel()

void OpenSim::MocoParameter::initializeOnModel ( Model & model ) const

For use by solvers.

This performs error checks and caches information about the model that is useful during the optimization. This method takes a non-const reference to the model because parameters need to be able to alter the model. If it is desired to apply this MocoParameter to multiple models, this should be called on all models of interest. The property references from each model will be append to this MocoParameter's internal property reference list.

◆ printDescription()

void OpenSim::MocoParameter::printDescription ( std::ostream & stream = std::cout ) const

Print the name, property name, component paths, property element (if it exists), and bounds for this parameter.

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

MocoParameter.h