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API
4.2
For MATLAB, Python, Java, and C++ users
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API
4.2
For MATLAB, Python, Java, and C++ users
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This class implements a configurable equilibrium muscle model, as described in Millard et al. (2013). More...
Inheritance diagram for OpenSim::Millard2012EquilibriumMuscle:Static Public Member Functions | |
Auto-generated functions | |
| static Millard2012EquilibriumMuscle * | safeDownCast (OpenSim::Object *obj) |
| For use in MATLAB and Python to access the concrete class. More... | |
| Static Public Member Functions inherited from OpenSim::Muscle | |
| static Muscle * | safeDownCast (OpenSim::Object *obj) |
| For use in MATLAB and Python to access the concrete class. More... | |
| static const std::string & | getClassName () |
| This returns "Muscle" More... | |
| Static Public Member Functions inherited from OpenSim::PathActuator | |
| static PathActuator * | safeDownCast (OpenSim::Object *obj) |
| For use in MATLAB and Python to access the concrete class. More... | |
| static const std::string & | getClassName () |
| This returns "PathActuator" More... | |
| Static Public Member Functions inherited from OpenSim::ScalarActuator | |
| static ScalarActuator * | safeDownCast (OpenSim::Object *obj) |
| For use in MATLAB and Python to access the concrete class. More... | |
| static const std::string & | getClassName () |
| This returns "ScalarActuator" More... | |
| Static Public Member Functions inherited from OpenSim::Actuator | |
| static Actuator * | safeDownCast (OpenSim::Object *obj) |
| For use in MATLAB and Python to access the concrete class. More... | |
| static const std::string & | getClassName () |
| This returns "Actuator" More... | |
| Static Public Member Functions inherited from OpenSim::Force | |
| static Force * | safeDownCast (OpenSim::Object *obj) |
| For use in MATLAB and Python to access the concrete class. More... | |
| static const std::string & | getClassName () |
| This returns "Force" More... | |
| Static Public Member Functions inherited from OpenSim::ModelComponent | |
| static ModelComponent * | safeDownCast (OpenSim::Object *obj) |
| For use in MATLAB and Python to access the concrete class. More... | |
| static const std::string & | getClassName () |
| This returns "ModelComponent" More... | |
| Static Public Member Functions inherited from OpenSim::Component | |
| static Component * | safeDownCast (OpenSim::Object *obj) |
| For use in MATLAB and Python to access the concrete class. More... | |
| static const std::string & | getClassName () |
| This returns "Component" 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 "Millard2012EquilibriumMuscle" More... | |
| Millard2012EquilibriumMuscle * | 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... | |
Additional Inherited Members | |
| Public Member Functions inherited from OpenSim::Muscle | |
| Public Member Functions inherited from OpenSim::PathActuator | |
| PathActuator * | 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... | |
| Public Member Functions inherited from OpenSim::ScalarActuator | |
| Public Member Functions inherited from OpenSim::Actuator | |
| Public Member Functions inherited from OpenSim::Force | |
| Public Member Functions inherited from OpenSim::ModelComponent | |
| ModelComponent () | |
| Default constructor. More... | |
| ModelComponent (const std::string &aFileName, bool aUpdateFromXMLNode=true) | |
| Construct ModelComponent from an XML file. More... | |
| ModelComponent (SimTK::Xml::Element &aNode) | |
| Construct ModelComponent from a specific node in an XML document. More... | |
| virtual | ~ModelComponent () |
| Destructor is virtual to allow concrete model component cleanup. More... | |
| void | connectToModel (Model &model) |
| Connect this ModelComponent to its aggregate- a Model. More... | |
| const Model & | getModel () const |
| Get a const reference to the Model this component is part of. More... | |
| Model & | updModel () |
| Get a modifiable reference to the Model this component is part of. More... | |
| bool | hasModel () const |
| Does this ModelComponent have a Model associated with it? More... | |
| void | preScale (const SimTK::State &s, const ScaleSet &scaleSet) |
| Perform any computations that must occur before ModelComponent::scale() is invoked on all ModelComponents in the Model. More... | |
| void | scale (const SimTK::State &s, const ScaleSet &scaleSet) |
| Scale the ModelComponent. More... | |
| void | postScale (const SimTK::State &s, const ScaleSet &scaleSet) |
| Perform any computations that must occur after ModelComponent::scale() has been invoked on all ModelComponents in the Model. More... | |
| Public Member Functions inherited from OpenSim::Component | |
| 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... | |
| 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 |
This class implements a configurable equilibrium muscle model, as described in Millard et al. (2013).
An equilibrium model assumes that the forces generated by the fiber and tendon are equal:
\[ f_{ISO}\Big(\mathbf{a}(t) \mathbf{f}_L(\hat{l}_{CE}) \mathbf{f}_V(\hat{v}_{CE}) + \mathbf{f}_{PE}(\hat{l}_{CE}) + \beta \hat{v}_{CE}\Big) \cos \phi - f_{ISO}\mathbf{f}_{SE}(\hat{l}_{T}) = 0 \]
This model can be simulated in several configurations by adjusting three flags:
Elastic Tendon, No Fiber Damping
The most typical configuration used in the literature is to simulate a muscle with an elastic tendon, full fiber dynamics, and activation dynamics. The resulting formulation suffers from three singularities: \(\mathbf{a}(t) \rightarrow 0\), \(\phi \rightarrow 90^\circ\), and \( \mathbf{f}_L(\hat{l}_{CE}) \rightarrow 0 \). These situations are all handled in this model to ensure that it does not produce singularities and does not result in intolerably long simulation times.
Numerical singularities arise from the manner in which the equilibrium equation is rearranged to yield an ordinary differential equation (ODE). The above equation is rearranged to isolate \( \mathbf{f}_V(\hat{v}_{CE}) \). We then invert to solve for \( \hat{v}_{CE} \), which is then numerically integrated during a simulation:
\[ \hat{v}_{CE} = \mathbf{f}_V ^{-1} \Big( \frac{ ( \mathbf{f}_{SE}(\hat{l}_{T}) ) / \cos \phi - \mathbf{f}_{PE}(\hat{l}_{CE}) } { \mathbf{a}(t) \mathbf{f}_L(\hat{l}_{CE})} \Big) \]
The above equation becomes numerically stiff when terms in the denominator approach zero (when \(\mathbf{a}(t) \rightarrow 0\), \(\phi \rightarrow 90^\circ\), or \( \mathbf{f}_L(\hat{l}_{CE}) \rightarrow 0 \)) or, additionally, when the slope of \(\mathbf{f}_V ^{-1}\) is steep (which occurs at fiber velocities close to the maximum concentric and maximum eccentric fiber velocities).
Singularities can be managed by ensuring that the muscle model is always activated ( \(\mathbf{a}(t) > 0\)), the fiber will stop contracting when a pennation angle of 90 degrees is approached ( \(\phi < 90^\circ\)), and the fiber will also stop contracting as its length approaches a lower bound ( \( \hat{l}_{CE} > lowerbound\)), which is typically around half the fiber's resting length (to ensure \( \mathbf{f}_L(\hat{l}_{CE}) > 0 \)). The fiber is prevented from reaching unphysiological lengths or its maximum pennation angle using a unilateral constraint. Additionally, the force-velocity curve is modified so that it is invertible.
When an elastic tendon without fiber damping is selected, the minimum active-force-length value is set to 0.1, the minimum permissible activation is set to 0.01, and the maximum permissible pennation angle is set to acos(0.1) or 84.3 degrees. This is done as a convenience for the user to prevent the model from taking an unreasonable amount of time to simulate.
(Rigid Tendon) or (Elastic Tendon with Fiber Damping)
Neither of these formulations has any singularities. The lower bound of the active-force-length curve can be zero (min( \( \mathbf{f}_L(\hat{l}_{CE})) = 0 \)), activation can be zero (i.e., the muscle can be turned off completely), and the force-velocity curve need not be invertible.
The rigid tendon formulation removes the singularities by ignoring the elasticity of the tendon. This assumption is reasonable for many muscles, but it is up to the user to determine whether this assumption is valid.
The formulation that uses an elastic tendon with fiber damping removes singularities by solving the equilibrium equation with Newton's method. This is possible because the partial derivative of the equilibrium equation with respect to fiber velocity is always positive if \( \beta > 0\) and, thus, Newton's method can find a solution to the equilibrium equation.
When either of these singularity-free formulations is selected, the minimum active-force-length value and the minimum permissible activation are set to zero. This is done as a convenience for the user, as these changes make the results of the model more realistic yet incur no performance penalty. The maximum pennation angle is left as acos(0.1) or 84.3 degrees, as allowing higher pennation angles results in an increasingly stiff fiber velocity state as pennation angle increases.
Usage
This object should be updated through the set methods provided.
Example
Please refer to the doxygen for more information on the properties that are objects themselves (MuscleFixedWidthPennationModel, ActiveForceLengthCurve, FiberForceLengthCurve, TendonForceLengthCurve, and ForceVelocityInverseCurve).
Reference
Millard, M., Uchida, T., Seth, A., Delp, S.L. (2013) Flexing computational muscle: modeling and simulation of musculotendon dynamics. ASME Journal of Biomechanical Engineering 135(2):021005. http://dx.doi.org/10.1115/1.4023390.
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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::Muscle.
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inlinestatic |
This returns "Millard2012EquilibriumMuscle"
See getConcreteClassName() if you want the class name of the underlying concrete object instead.
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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.
Implements OpenSim::Muscle.
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inlinestatic |
For use in MATLAB and Python to access the concrete class.
Example: cObj = Millard2012EquilibriumMuscle.safeDownCast(obj). This is equivalent to dynamic_cast<Millard2012EquilibriumMuscle*>(obj) in C++.
1.9.1 