A Solver to compute the induced accelerations of an applied "force" acting on the model. More...

Inheritance diagram for OpenSim::InducedAccelerationsSolver:

Public Member Functions
	InducedAccelerationsSolver (const Model &model)
	Construct an InducedAccelerations solver applied to the given model. More...

const SimTK::Vector &	solve (const SimTK::State &state, const SimTK::Vector &appliedMobilityForces, const SimTK::Vector_< SimTK::SpatialVec > &appliedBodyForces, SimTK::Vector_< SimTK::SpatialVec > *constraintReactions=nullptr)
	Add a constraint that will replace an external or contact force in the model (identified by name). More...

const SimTK::Vector &	solve (const SimTK::State &state, const std::string &forceName, bool computeActuatorPotentialOnly=false, SimTK::Vector_< SimTK::SpatialVec > *constraintReactions=0)
	Solve for the induced (generalized) accelerations (udot) resulting from any model force identified by name. More...

double	getInducedCoordinateAcceleration (const SimTK::State &s, const std::string &coordName)
	Convenience coordinate, body, or center of mass acceleration access after solving the system at the current state. More...

const SimTK::SpatialVec &	getInducedBodyAcceleration (const SimTK::State &s, const std::string &bodyName)

SimTK::Vec3	getInducedMassCenterAcceleration (const SimTK::State &s)

Public Member Functions inherited from OpenSim::Solver
virtual	~Solver ()

	Solver (const Model &model)

const Model &	getModel () const

Public Member Functions inherited from OpenSim::Object
virtual	~Object ()
	Virtual destructor for cleanup. More...

bool	isEqualTo (const Object &aObject) const
	Equality operator wrapper for use from languages not supporting operator overloading. More...

Object &	operator= (const Object &aObject)
	Copy assignment copies he base class fields, including the properties. More...

virtual bool	operator== (const Object &aObject) const
	Determine if two objects are equal. More...

virtual bool	operator< (const Object &aObject) const
	Provide an ordering for objects so they can be put in sorted containers. More...

void	setName (const std::string &name)
	Set the name of the Object. More...

const std::string &	getName () const
	Get the name of this Object. More...

void	setDescription (const std::string &description)
	Set description, a one-liner summary. More...

const std::string &	getDescription () const
	Get description, a one-liner summary. More...

const std::string &	getAuthors () const
	Get Authors of this Object. More...

void	setAuthors (const std::string &authors)
	Set Authors of this object. More...

const std::string &	getReferences () const
	Get references or publications to cite if using this object. More...

void	setReferences (const std::string &references)
	Set references or publications to cite if using this object. More...

int	getNumProperties () const
	Determine how many properties are stored with this Object. More...

const AbstractProperty &	getPropertyByIndex (int propertyIndex) const
	Get a const reference to a property by its index number, returned as an AbstractProperty. More...

AbstractProperty &	updPropertyByIndex (int propertyIndex)
	Get a writable reference to a property by its index number, returned as an AbstractProperty. More...

bool	hasProperty (const std::string &name) const
	Return true if this Object has a property of any type with the given name, which must not be empty. More...

const AbstractProperty &	getPropertyByName (const std::string &name) const
	Get a const reference to a property by its name, returned as an AbstractProperty. More...

AbstractProperty &	updPropertyByName (const std::string &name)
	Get a writable reference to a property by its name, returned as an AbstractProperty. More...

template<class T >
bool	hasProperty () const
	Return true if this Object contains an unnamed, one-object property that contains objects of the given template type T. More...

template<class T >
const Property< T > &	getProperty (const PropertyIndex &index) const
	Get property of known type Property<T> as a const reference; the property must be present and have the right type. More...

template<class T >
Property< T > &	updProperty (const PropertyIndex &index)
	Get property of known type Property<T> as a writable reference; the property must be present and have the right type. More...

bool	isObjectUpToDateWithProperties () const
	Returns `true` if no property's value has changed since the last time setObjectIsUpToDateWithProperties() was called. More...

void	readObjectFromXMLNodeOrFile (SimTK::Xml::Element &objectElement, int versionNumber)
	We're given an XML element from which we are to populate this Object. More...

virtual void	updateFromXMLNode (SimTK::Xml::Element &objectElement, int versionNumber)
	Use this method to deserialize an object from a SimTK::Xml::Element. More...

void	updateXMLNode (SimTK::Xml::Element &parent, const AbstractProperty *prop=nullptr) const
	Serialize this object into the XML node that represents it. More...

bool	getInlined () const
	Inlined means an in-memory Object that is not associated with an XMLDocument. More...

void	setInlined (bool aInlined, const std::string &aFileName="")
	Mark this as inlined or not and optionally provide a file name to associate with the new XMLDocument for the non-inline case. More...

std::string	getDocumentFileName () const
	If there is a document associated with this object then return the file name maintained by the document. More...

int	getDocumentFileVersion () const
	If there is a document associated with this object then return its version number. More...

void	setAllPropertiesUseDefault (bool aUseDefault)

bool	print (const std::string &fileName) const
	Write this Object into an XML file of the given name; conventionally the suffix to use is ".osim". More...

std::string	dump () const
	dump the XML representation of this Object into an std::string and return it. More...

virtual bool	isA (const char *type) const
	The default implementation returns true only if the supplied string is "Object"; each Object-derived class overrides this to match its own class name. More...

const std::string &	toString () const
	Wrapper to be used on Java side to display objects in tree; this returns just the object's name. More...

PropertySet &	getPropertySet ()
	OBSOLETE: Get a reference to the PropertySet maintained by the Object. More...

const PropertySet &	getPropertySet () const

Static Public Member Functions
Auto-generated functions
static InducedAccelerationsSolver *	safeDownCast (OpenSim::Object *obj)
	For use in MATLAB and Python to access the concrete class. More...

Static Public Member Functions inherited from OpenSim::Solver
static Solver *	safeDownCast (OpenSim::Object *obj)
	For use in MATLAB and Python to access the concrete class. More...

static const std::string &	getClassName ()
	This returns "Solver" More...

Static Public Member Functions inherited from OpenSim::Object
static void	registerType (const Object &defaultObject)
	Register an instance of a class; if the class is already registered it will be replaced. More...

static void	renameType (const std::string &oldTypeName, const std::string &newTypeName)
	Support versioning by associating the current Object type with an old name. More...

static const Object *	getDefaultInstanceOfType (const std::string &concreteClassName)
	Return a pointer to the default instance of the registered (concrete) Object whose class name is given, or NULL if the type is not registered. More...

template<class T >
static bool	isObjectTypeDerivedFrom (const std::string &concreteClassName)
	Return true if the given concrete object type represents a subclass of the template object type T, and thus could be referenced with a T*. More...

static Object *	newInstanceOfType (const std::string &concreteClassName)
	Create a new instance of the concrete Object type whose class name is given as concreteClassName. More...

static void	getRegisteredTypenames (Array< std::string > &typeNames)
	Retrieve all the typenames registered so far. More...

template<class T >
static void	getRegisteredObjectsOfGivenType (ArrayPtrs< T > &rArray)
	Return an array of pointers to the default instances of all registered (concrete) Object types that derive from a given Object-derived type that does not have to be concrete. More...

static bool	PrintPropertyInfo (std::ostream &os, const std::string &classNameDotPropertyName, bool printFlagInfo=true)
	Dump formatted property information to a given output stream, useful for creating a "help" facility for registered objects. More...

static bool	PrintPropertyInfo (std::ostream &os, const std::string &className, const std::string &propertyName, bool printFlagInfo=true)
	Same as the other signature but the class name and property name are provided as two separate strings. More...

static Object *	makeObjectFromFile (const std::string &fileName)
	Create an OpenSim object whose type is based on the tag at the root node of the XML file passed in. More...

static const std::string &	getClassName ()
	Return the name of this class as a string; i.e., "Object". More...

static void	setSerializeAllDefaults (bool shouldSerializeDefaults)
	Static function to control whether all registered objects and their properties are written to the defaults section of output files rather than only those values for which the default was explicitly overwritten when read in from an input file or set programmatically. More...

static bool	getSerializeAllDefaults ()
	Report the value of the "serialize all defaults" flag. More...

static bool	isKindOf (const char *type)
	Returns true if the passed-in string is "Object"; each Object-derived class defines a method of this name for its own class name. More...

static void	setDebugLevel (int newLevel)
	Set the amount of logging output. More...

static int	getDebugLevel ()
	Get the current setting of debug level. More...

static Object *	SafeCopy (const Object *aObject)
	Use the clone() method to duplicate the given object unless the pointer is null in which case null is returned. More...

static void	RegisterType (const Object &defaultObject)
	OBSOLETE alternate name for registerType(). More...

static void	RenameType (const std::string &oldName, const std::string &newName)
	OBSOLETE alternate name for renameType(). More...

Auto-generated functions <br>
static const std::string &	getClassName ()
	This returns "InducedAccelerationsSolver" More...

InducedAccelerationsSolver *	clone () const override
	Create a new heap-allocated copy of the concrete object to which this Object refers. More...

const std::string &	getConcreteClassName () const override
	Returns the class name of the concrete Object-derived class of the actual object referenced by this Object, as a string. More...

Detailed Description

A Solver to compute the induced accelerations of an applied "force" acting on the model.

The solver can apply constraints to replace external (contact) forces in order to decompose contributions of external reaction forces and to subsequently determine the induced (generalized) accelerations (udot). The solver can compute the induced acceleration and constraint reaction force contributions for any model Force.

The solver converts the unconstrained system:

(1) [M]*udot = G(q) + V(q,u) + S(t, q,u) + F(t, q, u, z, x) where G = gravitational, V = velocity dependent, S = external or contact forces w.r.t. to ground and F are all other applied model forces like motors and muscles. q generalized coordinates, u mobilities (gen speeds, qdot = [N]*u) z other state variables (e.g. muscle fiber lengths), x controls t time, q, u, and z constitute the State of the model

to a constrained system: (2a) [M]*udot = G(q) + V(q,u) -[~C]*lambda + F(t, q, u, z, x) (2b) [C]*udot = b(t,q,u) by replacing the external forces or passive contact force S with rigid kinematic constraints imposed on the system acceleration ([C] and b obtained by differentiating position and velocity constraints) and enforced in the system dynamics by Lagrange multipliers, lambda. NOTE: The validity of the constraints can be tested by the accuracy by which [~C]*lambda can reconstitute S, when all forces are applied.

Eqn 2 is linear in both udot (accelerations) and external (or contact) forces and the contribution of applied forces to the model's accelerations (udot_i) and external forces (reaction_i) can be directly evaluated. The contribution of a force (like gravity or a muscle) to the system acceleration is called its "induced acceleration" and the contribution to the reaction (or external) force is its "induced reaction".

NOTE, the sum of induced accelerations and reactions MUST total to the complete system acceleration or external force when all model forces are applied.

The solver can apply any OpenSim::Constraint that implements setContactPointForInducedAccelerations() to replace external and/or contact forces that are applied during a forward dynamics simulation.

Author: Ajay Seth

Constructor & Destructor Documentation

◆ InducedAccelerationsSolver()

OpenSim::InducedAccelerationsSolver::InducedAccelerationsSolver ( const Model & model )

Construct an InducedAccelerations solver applied to the given model.

Member Function Documentation

◆ applyContactConstraintAccordingToExternalForces()

Array<bool> OpenSim::InducedAccelerationsSolver::applyContactConstraintAccordingToExternalForces ( SimTK::State & s )

protected

◆ clone()

InducedAccelerationsSolver* OpenSim::InducedAccelerationsSolver::clone ( ) const

inlineoverridevirtual

Create a new heap-allocated copy of the concrete object to which this Object refers.

It is up to the caller to delete the returned object when no longer needed. Every concrete object deriving from Object implements this pure virtual method automatically, via the declaration macro it invokes (e.g., OpenSim_DECLARE_CONCRETE_OBJECT()). Note that the concrete class overrides modify the return type to be a pointer to the concrete object; that still overrides the base class method because the return type is covariant with (that is, derives from) Object.

Implements OpenSim::Solver.

◆ getClassName()

static const std::string& OpenSim::InducedAccelerationsSolver::getClassName ( )

inlinestatic

This returns "InducedAccelerationsSolver"

See getConcreteClassName() if you want the class name of the underlying concrete object instead.

◆ getConcreteClassName()

const std::string& OpenSim::InducedAccelerationsSolver::getConcreteClassName ( ) const

inlineoverridevirtual

Returns the class name of the concrete Object-derived class of the actual object referenced by this Object, as a string.

This is the string that is used as the tag for this concrete object in an XML file. Every concrete class derived from Object automatically overrides this method via the declaration macro it uses. See getClassName() to get the class name of the referencing (possibly abstract) class rather than the concrete object.

See also: getClassName()

Implements OpenSim::Solver.

◆ getInducedBodyAcceleration()

const SimTK::SpatialVec& OpenSim::InducedAccelerationsSolver::getInducedBodyAcceleration	(	const SimTK::State &	s,
		const std::string &	bodyName
	)

◆ getInducedCoordinateAcceleration()

double OpenSim::InducedAccelerationsSolver::getInducedCoordinateAcceleration	(	const SimTK::State &	s,
		const std::string &	coordName
	)

Convenience coordinate, body, or center of mass acceleration access after solving the system at the current state.

NOTE, if the solver has not been called to solve for induced accelerations for a given force contributor, an exception is thrown. These methods are intended to provide low cost access to accelerations in different forms once accelerations have already been resolved.

◆ getInducedMassCenterAcceleration()

SimTK::Vec3 OpenSim::InducedAccelerationsSolver::getInducedMassCenterAcceleration ( const SimTK::State & s )

◆ getSolvedState()

const SimTK::State& OpenSim::InducedAccelerationsSolver::getSolvedState ( const SimTK::State & s ) const

protected

Helper functions.

Internal use function to get the solved state that is realized to Stage::Acceleration. If the state differs from the input state OR the state is not at the acceleration stage, an exception is thrown.

◆ safeDownCast()

static InducedAccelerationsSolver* OpenSim::InducedAccelerationsSolver::safeDownCast ( OpenSim::Object * obj )

inlinestatic

For use in MATLAB and Python to access the concrete class.

Example: cObj = InducedAccelerationsSolver.safeDownCast(obj). This is equivalent to dynamic_cast<InducedAccelerationsSolver*>(obj) in C++.

◆ solve() [1/2]

const SimTK::Vector& OpenSim::InducedAccelerationsSolver::solve	(	const SimTK::State &	state,
		const SimTK::Vector &	appliedMobilityForces,
		const SimTK::Vector_< SimTK::SpatialVec > &	appliedBodyForces,
		SimTK::Vector_< SimTK::SpatialVec > *	constraintReactions = `nullptr`
	)

Add a constraint that will replace an external or contact force in the model (identified by name).

Replacing a force that is not an ExternalForce, ElasticFoundationForce or HuntCrossleyForce (in contact with ground) will cause an Exception.

Any OpenSim::Constraint that implements the method setContactPointForInducedAccelerations(SimTK::State state, Vec3 point) (

See also: OpenSim::Constraint) can be applied as a replacement.

A threshold is used to determine when the constraint should be engaged. If the external force magnitude exceeds the threshold, it is replaced by the constraint to solve for induced accelerations.

void replaceForceWithConstraint(const std::string& forceToReplace, const Constraint& replacementConstraint, double threshold); Solve for the induced (generalized) accelerations (udot) resulting from the supplied force. An supplied force is expressed as any combination of mobility (generalized) forces and/or body forces.

Parameters

[in]	state	current State of the model
[in]	appliedMobilityForces	Vector of applied mobility forces
[in]	appliedBodyForces	Vector of spatial forces applied to the model (1 per body)
[out]	constraintReactions	(optional) Vector of induced reaction forces

Returns: A const reference to the Vector of resulting model induced generalized accelerations (udot).

◆ solve() [2/2]

const SimTK::Vector& OpenSim::InducedAccelerationsSolver::solve	(	const SimTK::State &	state,
		const std::string &	forceName,
		bool	computeActuatorPotentialOnly = `false`,
		SimTK::Vector_< SimTK::SpatialVec > *	constraintReactions = `0`
	)

Solve for the induced (generalized) accelerations (udot) resulting from any model force identified by name.