API  4.2
For C++ developers
OpenSim::InducedAccelerationsSolver Class Reference

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::SpatialVecgetInducedBodyAcceleration (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 ModelgetModel () const
 
void assign (Object &aObject) override
 This allows copy assignment in the Java GUI. More...
 
- 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...
 
Objectoperator= (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 AbstractPropertygetPropertyByIndex (int propertyIndex) const
 Get a const reference to a property by its index number, returned as an AbstractProperty. More...
 
AbstractPropertyupdPropertyByIndex (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 AbstractPropertygetPropertyByName (const std::string &name) const
 Get a const reference to a property by its name, returned as an AbstractProperty. More...
 
AbstractPropertyupdPropertyByName (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...
 
PropertySetgetPropertySet ()
 OBSOLETE: Get a reference to the PropertySet maintained by the Object. More...
 
const PropertySetgetPropertySet () const
 

Public Types

typedef InducedAccelerationsSolver Self
 This typedef might be useful within the member functions of this class. More...
 
typedef Solver Super
 Use this typedef to refer to the superclass of this class. More...
 
- Public Types inherited from OpenSim::Solver
typedef Solver Self
 This typedef might be useful within the member functions of this class. More...
 
typedef Object Super
 Use this typedef to refer to the superclass of this class. More...
 

Protected Member Functions

const SimTK::State & getSolvedState (const SimTK::State &s) const
 Helper functions. More...
 
Array< bool > applyContactConstraintAccordingToExternalForces (SimTK::State &s)
 
- Protected Member Functions inherited from OpenSim::Object
 Object ()
 The default constructor is only for use by constructors of derived types. More...
 
 Object (const std::string &fileName, bool aUpdateFromXMLNode=true)
 Constructor from a file, to be called from other constructors that take a file as input. More...
 
 Object (const Object &source)
 Copy constructor is invoked automatically by derived classes with default copy constructors; otherwise it must be invoked explicitly. More...
 
 Object (SimTK::Xml::Element &aElement)
 Construct the base class portion of an Object from a given Xml element that describes this Object. More...
 
template<class T >
PropertyIndex addProperty (const std::string &name, const std::string &comment, const T &value)
 Define a new single-value property of known type T, with the given name, associated comment, and initial value. More...
 
template<class T >
PropertyIndex addOptionalProperty (const std::string &name, const std::string &comment)
 Add an optional property, meaning it can contain either no value or a single value. More...
 
template<class T >
PropertyIndex addOptionalProperty (const std::string &name, const std::string &comment, const T &value)
 Add an optional property, meaning it can contain either no value or a single value. More...
 
template<class T >
PropertyIndex addListProperty (const std::string &name, const std::string &comment, int minSize, int maxSize)
 Define a new list-valued property of known type T, with the given name, associated comment, minimum (==0) and maximum (>0) allowable list lengths, and a zero-length initial value. More...
 
template<class T , template< class > class Container>
PropertyIndex addListProperty (const std::string &name, const std::string &comment, int minSize, int maxSize, const Container< T > &valueList)
 Define a new list-valued property as above, but assigning an initial value via some templatized container class that supports size() and indexing. More...
 
PropertyIndex getPropertyIndex (const std::string &name) const
 Look up a property by name and return its PropertyIndex if it is found. More...
 
template<class T >
PropertyIndex getPropertyIndex () const
 Look up an unnamed property by the type of object it contains, and return its PropertyIndex if it is found. More...
 
template<class T >
void checkPropertyValueIsPositive (const Property< T > &p) const
 Throw an exception if any of the property's values are not positive. More...
 
template<class T >
void checkPropertyValueIsInSet (const Property< T > &p, const std::set< T > &set) const
 Throw an exception if any of the property's values are not in the provided set. More...
 
template<class T >
void checkPropertyValueIsInRangeOrSet (const Property< T > &p, const T &lower, const T &upper, const std::set< T > &set) const
 Throw an exception if any of the property's values are neither in the provided range nor in the provided set. More...
 
void setObjectIsUpToDateWithProperties ()
 When an object is initialized using the current values of its properties, it can set a flag indicating that it is up to date. More...
 
void clearObjectIsUpToDateWithProperties ()
 For testing or debugging purposes, manually clear the "object is up to date with respect to properties" flag. More...
 
void makeObjectNamesConsistentWithProperties ()
 Make sure the name of an object is consistent with its property type. More...
 
void updateFromXMLDocument ()
 Use this method only if you're deserializing from a file and the object is at the top level; that is, primarily in constructors that take a file name as input. More...
 
void setDocument (XMLDocument *doc)
 Unconditionally set the XMLDocument associated with this object. More...
 
const XMLDocumentgetDocument () const
 Get a const pointer to the document (if any) associated with this object. More...
 
XMLDocumentupdDocument ()
 Get a writable pointer to the document (if any) associated with this object. More...
 

Auto-generated functions

static InducedAccelerationsSolversafeDownCast (OpenSim::Object *obj)
 For use in MATLAB and Python to access the concrete class. More...
 
static const std::string & getClassName ()
 This returns "InducedAccelerationsSolver". More...
 
void assign (Object &aObject) override
 This allows copy assignment in the Java GUI. More...
 
InducedAccelerationsSolverclone () 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...
 

Additional Inherited Members

- Static Public Member Functions inherited from OpenSim::Solver
static SolversafeDownCast (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 ObjectgetDefaultInstanceOfType (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 ObjectnewInstanceOfType (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 ObjectmakeObjectFromFile (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 ObjectSafeCopy (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...
 
- Static Public Attributes inherited from OpenSim::Object
static const std::string DEFAULT_NAME
 Name used for default objects when they are serialized. More...
 
- Protected Attributes inherited from OpenSim::Object
PropertySet _propertySet
 OBSOLETE: Property_Deprecated set for serializable member variables of this and derived classes. 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

Member Typedef Documentation

◆ Self

This typedef might be useful within the member functions of this class.

This is generated by the OpenSim_DECLARE_*_OBJECT macros.

◆ Super

Use this typedef to refer to the superclass of this class.

Avoid using the explicit type name of the superclass; this would introduce bugs if the superclass is changed.

This is generated by the OpenSim_DECLARE_*_OBJECT macros.

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

◆ assign()

void OpenSim::InducedAccelerationsSolver::assign ( Object aObject)
inlineoverride

This allows copy assignment in the Java GUI.

Exceptions
Exceptionif the argument is not of type InducedAccelerationsSolver.

◆ 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.

This is generated by the OpenSim_DECLARE_*_OBJECT macros.

◆ 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]statecurrent State of the model
[in]appliedMobilityForcesVector of applied mobility forces
[in]appliedBodyForcesVector 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.

Parameters
[in]statecurrent State of the model
[in]forceNamename of model Force contributor "gravity" and "velocity" are special names for gravitational forces and velocity dependent forces (Coriolis and gyroscopic). Otherwise use the name of the Force component.
[in]computeActuatorPotentialOnlyflag (bool) to determine only the potential of an Actuator (a Force) due to an actuation (scalar rep of the actuator's force magnitude) of 1. Since force scales linearly
[out]constraintReactions(optional) Vector of induced reaction forces
Returns
A const reference to the Vector of the induced generalized accelerations (udot) from the specified force.

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