API  4.2 For C++ developers
OpenSim::Blankevoort1991Ligament Class Reference

This class implements a nonlinear spring ligament model introduced by Blankevoort et al. (1991) [1] and further described in Smith et al. (2016) [2]. More...

Inheritance diagram for OpenSim::Blankevoort1991Ligament:

## OpenSim Properties, Sockets, Outputs, Inputs

Properties (unnamed)
GeometryPath GeometryPath
"The set of points defining the path of the ligament" More...

Properties (single-value)
double linear_stiffness
"The slope of the linear region of the force-strain curve. " "Units of force/strain (N)." More...

double transition_strain
"The strain at which the ligament force-strain curve transitions from " "quadratic to linear. Units of strain. Default value of 0.06 (6%)." More...

double damping_coefficient
"The coefficient that multiplies the strain rate when computing the " " damping force. Units of N*s/strain. Default value of 0.003." More...

double slack_length
"The length at which ligament begins developing tension. Units of m." More...

Outputs
double spring_force
Provides the value of getSpringForce() and is available at stage SimTK::Stage::Position . More...

double damping_force
Provides the value of getDampingForce() and is available at stage SimTK::Stage::Velocity . More...

double total_force
Provides the value of getTotalForce() and is available at stage SimTK::Stage::Velocity . More...

double strain
Provides the value of getStrain() and is available at stage SimTK::Stage::Position . More...

double strain_rate
Provides the value of getStrainRate() and is available at stage SimTK::Stage::Velocity . More...

double length
Provides the value of getLength() and is available at stage SimTK::Stage::Position . More...

double lengthening_speed
Provides the value of getLengtheningSpeed() and is available at stage SimTK::Stage::Velocity . More...

OpenSim Properties, Sockets, Outputs, Inputs inherited from OpenSim::Force
bool appliesForce
"Flag indicating whether the force is applied or not. If true the force" "is applied to the MultibodySystem otherwise the force is not applied." "NOTE: Prior to OpenSim 4.0, this behavior was controlled by the " "'isDisabled' property, where 'true' meant that force was not being " "applied. Thus, if 'isDisabled' is true, then 'appliesForce is false." More...

double potential_energy
Provides the value of computePotentialEnergy() and is available at stage SimTK::Stage::Velocity . More...

OpenSim Properties, Sockets, Outputs, Inputs inherited from OpenSim::Component
Component components
"List of components that this component owns and serializes." More...

## Public Member Functions

Blankevoort1991Ligament ()

Blankevoort1991Ligament (std::string name, const PhysicalFrame &frame1, SimTK::Vec3 point1, const PhysicalFrame &frame2, SimTK::Vec3 point2)

Blankevoort1991Ligament (std::string name, const PhysicalFrame &frame1, SimTK::Vec3 point1, const PhysicalFrame &frame2, SimTK::Vec3 point2, double linear_stiffness, double slack_length)

Blankevoort1991Ligament (std::string name, double linear_stiffness, double slack_length)

void setSlackLengthFromReferenceStrain (double strain, const SimTK::State &reference_state)
Set the slack_length property using the strain in the ligament at a known pose (reference state). More...

void setSlackLengthFromReferenceForce (double force, const SimTK::State &reference_state)
Set the slack_length property using the absolute spring force (N) in the ligament at a known pose (reference force). More...

void setLinearStiffnessForcePerLength (double linear_stiffness)
Set the linear_stiffness property using a value in units of force/length (N/m). More...

void setDampingCoefficientForceTimePerLength (double damping_coefficient)
Set the damping_coefficient property using a value in units of force*time/length (N*s/m). More...

double getStrain (const SimTK::State &state) const

double getStrainRate (const SimTK::State &state) const

double getLength (const SimTK::State &state) const

double getLengtheningSpeed (const SimTK::State &state) const

double getSpringForce (const SimTK::State &state) const

double getDampingForce (const SimTK::State &state) const

double getTotalForce (const SimTK::State &state) const

double getLinearStiffnessForcePerLength () const
Get the linear_stiffness property in units of force/length (N/m) More...

double getTransitionLength () const
Get the length (m) of the ligament where the model transitions from the toe region to the linear region. More...

double getDampingCoefficientForceTimePerLength () const
Get the damping_coefficient in units of force*time/length (N*s/m) More...

double computeMomentArm (const SimTK::State &s, Coordinate &aCoord) const

void computeForce (const SimTK::State &s, SimTK::Vector_< SimTK::SpatialVec > &bodyForces, SimTK::Vector &generalizedForces) const override
Subclasses must implement this method to compute the forces that should be applied to bodies and generalized speeds. More...

double computePotentialEnergy (const SimTK::State &state) const override
Subclasses may optionally override this method to compute a contribution to the potential energy of the system. More...

void extendPostScale (const SimTK::State &s, const ScaleSet &scaleSet) override
Perform any computations that must occur after ModelComponent::scale() has been invoked on all ModelComponents in the Model. More...

OpenSim::Array< std::string > getRecordLabels () const override
Methods to query a Force for the value actually applied during simulation. More...

OpenSim::Array< double > getRecordValues (const SimTK::State &state) const override
Given SimTK::State object extract all the values necessary to report forces, application location frame, etc. More...

Property-related functions
const GeometryPathget_GeometryPath () const
Get the value of the GeometryPath property. More...

GeometryPathupd_GeometryPath ()
Get a writable reference to the GeometryPath property. More...

void set_GeometryPath (const GeometryPath &value)
Set the value of the GeometryPath property. More...

const double & get_linear_stiffness () const
Get the value of the linear_stiffness property. More...

double & upd_linear_stiffness ()
Get a writable reference to the linear_stiffness property. More...

void set_linear_stiffness (const double &value)
Set the value of the linear_stiffness property. More...

const double & get_transition_strain () const
Get the value of the transition_strain property. More...

double & upd_transition_strain ()
Get a writable reference to the transition_strain property. More...

void set_transition_strain (const double &value)
Set the value of the transition_strain property. More...

const double & get_damping_coefficient () const
Get the value of the damping_coefficient property. More...

double & upd_damping_coefficient ()
Get a writable reference to the damping_coefficient property. More...

void set_damping_coefficient (const double &value)
Set the value of the damping_coefficient property. More...

const double & get_slack_length () const
Get the value of the slack_length property. More...

double & upd_slack_length ()
Get a writable reference to the slack_length property. More...

void set_slack_length (const double &value)
Set the value of the slack_length property. More...

Public Member Functions inherited from OpenSim::Force
virtual bool shouldBeParallelized () const
Tell SimBody to parallelize this force. More...

bool appliesForce (const SimTK::State &s) const
Return if the Force is applied (or enabled) or not. More...

void setAppliesForce (SimTK::State &s, bool applyForce) const
Set whether or not the Force is applied. More...

virtual bool hasGeometryPath () const
Return a flag indicating whether the Force is applied along a Path. More...

const bool & get_appliesForce () const
Get the value of the appliesForce property. More...

bool & upd_appliesForce ()
Get a writable reference to the appliesForce property. More...

void set_appliesForce (const bool &value)
Set the value of the appliesForce property. More...

void assign (Object &aObject) override
This allows copy assignment in the Java GUI. More...

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 ModelgetModel () const
Get a const reference to the Model this component is part of. More...

ModelupdModel ()
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...

void assign (Object &aObject) override
This allows copy assignment in the Java GUI. More...

Public Member Functions inherited from OpenSim::Component
Component ()
Default constructor. More...

Component (const std::string &aFileName, bool aUpdateFromXMLNode=true)
Construct Component from an XML file. More...

Component (SimTK::Xml::Element &aNode)
Construct Component from a specific node in an XML document. More...

Component (const Component &)=default
Use default copy constructor and assignment operator. More...

Componentoperator= (const Component &)=default

virtual ~Component ()=default
Destructor is virtual to allow concrete Component to cleanup. More...

virtual void generateDecorations (bool fixed, const ModelDisplayHints &hints, const SimTK::State &state, SimTK::Array_< SimTK::DecorativeGeometry > &appendToThis) const
Optional method for generating arbitrary display geometry that reflects this Component at the specified state. More...

const SimTK::MultibodySystem & getSystem () const
Get the underlying MultibodySystem that this component is connected to. More...

bool hasSystem () const
Check if this component has an underlying MultibodySystem. More...

bool isComponentInOwnershipTree (const Component *component) const
Does the provided component already exist anywhere in the ownership tree (not just subcomponents of this component)? More...

Add a Component (as a subcomponent) of this component. More...

template<typename T = Component>
ComponentList< const T > getComponentList () const
Get an iterator through the underlying subcomponents that this component is composed of. More...

template<typename T = Component>
ComponentList< T > updComponentList ()
Similar to getComponentList(), except the resulting list allows one to modify the components. More...

template<typename T = Component>
unsigned countNumComponents () const
Uses getComponentList<T>() to count the number of underlying subcomponents of the specified type. More...

std::string getAbsolutePathString () const
Get the complete (absolute) pathname for this Component to its ancestral Component, which is the root of the tree to which this Component belongs. More...

ComponentPath getAbsolutePath () const
Return a ComponentPath of the absolute path of this Component. More...

std::string getRelativePathString (const Component &wrt) const
Get the relative path of this Component with respect to another Component, as a string. More...

ComponentPath getRelativePath (const Component &wrt) const
Get the relative path of this Component with respect to another Component. More...

bool hasComponent (const std::string &pathname) const
Query if there is a component (of any type) at the specified path name. More...

template<class C = Component>
bool hasComponent (const std::string &pathname) const
Query if there is a component of a given type at the specified path name. More...

template<class C = Component>
const C & getComponent (const std::string &pathname) const
Get a unique subcomponent of this Component by its path name and type 'C'. More...

template<class C = Component>
const C & getComponent (const ComponentPath &pathname) const

const ComponentgetComponent (const std::string &pathname) const
Similar to the templatized getComponent(), except this returns the component as the generic Component type. More...

template<class C = Component>
C & updComponent (const std::string &name)
Get a writable reference to a subcomponent. More...

template<class C = Component>
C & updComponent (const ComponentPath &name)

ComponentupdComponent (const std::string &pathname)
Similar to the templatized updComponent(), except this returns the component as the generic Component type. More...

unsigned printComponentsMatching (const std::string &substring) const
Print a list to the console of all components whose absolute path name contains the given string. More...

int getNumStateVariables () const
Get the number of "continuous" state variables maintained by the Component and its subcomponents. More...

Array< std::string > getStateVariableNames () const
Get the names of "continuous" state variables maintained by the Component and its subcomponents. More...

template<class C = Component>
const C * findComponent (const ComponentPath &pathToFind) const
Find a Component to which this Component is an ancestor—in other words, a Component that is directly owned by this Component or is owned by one of its sub-components, sub-sub-components, etc. More...

template<class C = Component>
const C * findComponent (const std::string &pathToFind) const
Same as findComponent(const ComponentPath&), but accepting a string (a path or just a name) as input. More...

const StateVariabletraverseToStateVariable (const std::string &pathName) const
Get a StateVariable anywhere in the Component tree, given a StateVariable path. More...

void finalizeFromProperties ()
Define a Component's internal data members and structure according to its properties. More...

void finalizeConnections (Component &root)
Satisfy the Component's connections specified by its Sockets and Inputs. More...

void clearConnections ()
Disconnect/clear this Component from its aggregate component. More...

Have the Component add itself to the underlying computational System. More...

void initStateFromProperties (SimTK::State &state) const
Initialize Component's state variable values from its properties. More...

void setPropertiesFromState (const SimTK::State &state)
Set Component's properties given a state. More...

int getNumSockets () const
Get the number of Sockets in this Component. More...

std::vector< std::string > getSocketNames ()
Collect and return the names of the sockets in this component. More...

template<typename T >
const T & getConnectee (const std::string &name) const
Get the "connectee" object that the Component's Socket is bound to. More...

const ObjectgetConnectee (const std::string &name) const
Get the connectee as an Object. More...

const AbstractSocketgetSocket (const std::string &name) const
Get an AbstractSocket for the given socket name. More...

AbstractSocketupdSocket (const std::string &name)
Get a writable reference to the AbstractSocket for the given socket name. More...

template<typename T >
const Socket< T > & getSocket (const std::string &name) const
Get a const reference to the concrete Socket provided by this Component by name. More...

template<typename T >
Socket< T > & updSocket (const std::string &name)
Get a writable reference to the concrete Socket provided by this Component by name. More...

void printSubcomponentInfo () const
List all subcomponents by name and recurse into these components to list their subcomponents, and so on. More...

void printSocketInfo () const
List all the Sockets of this component and whether or not they are connected. More...

void printInputInfo () const
List all the inputs of this component and whether or not they are connected. More...

template<typename C >
void printSubcomponentInfo () const

void printOutputInfo (const bool includeDescendants=true) const
Print outputs of this component and optionally, those of all subcomponents. More...

int getNumInputs () const
Access the number of Inputs that this component has. More...

int getNumOutputs () const
Access the number of Outputs that this component has. More...

std::vector< std::string > getInputNames () const
Collect and return the names of Inputs in this component as an std::vector. More...

std::vector< std::string > getOutputNames () const
Collect and return the names of Outputs in this component as an std::vector. More...

const AbstractInputgetInput (const std::string &name) const
Get an Input provided by this Component by name. More...

AbstractInputupdInput (const std::string &name)
Get a writable reference to an Input provided by this Component by name. More...

template<typename T >
const Input< T > & getInput (const std::string &name) const
Get a concrete Input that you can directly ask for its values. More...

const AbstractOutputgetOutput (const std::string &name) const
Get the Output provided by this Component by name. More...

AbstractOutputupdOutput (const std::string &name)
Get a writable reference to an Output provided by this Component by name. More...

SimTK::IteratorRange< OutputConstIteratorgetOutputs () const
Iterate through all Outputs of this component. More...

void assign (Object &aObject) override
This allows copy assignment in the Java GUI. More...

int getModelingOption (const SimTK::State &state, const std::string &name) const
Get a ModelingOption flag for this Component by name. More...

void setModelingOption (SimTK::State &state, const std::string &name, int flag) const
Set the value of a ModelingOption flag for this Component. More...

template<typename T >
const T & getInputValue (const SimTK::State &state, const std::string &name) const
Get the Input value that this component is dependent on. More...

template<typename T >
const T & getOutputValue (const SimTK::State &state, const std::string &name) const
Get the Output value provided by this Component by name. More...

double getStateVariableValue (const SimTK::State &state, const std::string &name) const
Get the value of a state variable allocated by this Component. More...

void setStateVariableValue (SimTK::State &state, const std::string &name, double value) const
Set the value of a state variable allocated by this Component by name. More...

SimTK::Vector getStateVariableValues (const SimTK::State &state) const
Get all values of the state variables allocated by this Component. More...

void setStateVariableValues (SimTK::State &state, const SimTK::Vector &values) const
Set all values of the state variables allocated by this Component. More...

double getStateVariableDerivativeValue (const SimTK::State &state, const std::string &name) const
Get the value of a state variable derivative computed by this Component. More...

double getDiscreteVariableValue (const SimTK::State &state, const std::string &name) const
Get the value of a discrete variable allocated by this Component by name. More...

void setDiscreteVariableValue (SimTK::State &state, const std::string &name, double value) const
Set the value of a discrete variable allocated by this Component by name. More...

template<class T >
SimTK::CacheEntryIndex getCacheVariableIndex (const CacheVariable< T > &cv) const
Get the index of a Component's cache variable in the Subsystem for allocations. More...

SimTK::CacheEntryIndex getCacheVariableIndex (const std::string &name) const
Get the index of a Component's cache variable in the Subsystem for allocations. More...

template<class T >
const T & getCacheVariableValue (const SimTK::State &state, const std::string &name) const
Get the value of a cache variable allocated by this Component by name. More...

template<class T >
const T & getCacheVariableValue (const SimTK::State &state, const CacheVariable< T > &cv) const
Get the value of a cache variable allocated by this Component. More...

template<typename T >
void setCacheVariableValue (const SimTK::State &state, const std::string &k, T value) const
Set the value of a cache variable, identified by name, to a new value and mark the cache variable as valid. More...

template<typename T >
void setCacheVariableValue (const SimTK::State &state, const CacheVariable< T > &cv, T value) const
Set the value of a cache variable to a new value and mark the cache variable as valid. More...

template<typename T >
T & updCacheVariableValue (const SimTK::State &state, const std::string &name) const
Returns a mutable reference to the value of a cache variable identified by name. More...

template<typename T >
T & updCacheVariableValue (const SimTK::State &state, const CacheVariable< T > &cv) const
Returns a mutable reference to the value of a cache variable. More...

bool isCacheVariableValid (const SimTK::State &state, const std::string &name) const
Returns true if the cache variable, identified by name, is valid. More...

template<class T >
bool isCacheVariableValid (const SimTK::State &state, const CacheVariable< T > &cv) const
Returns true if the cache variable is valid. More...

void markCacheVariableValid (const SimTK::State &state, const std::string &name) const
Marks the value of a cache variable, identified by name, as valid. More...

template<typename T >
void markCacheVariableValid (const SimTK::State &state, const CacheVariable< T > &cv) const
Marks the value of a cache variable as valid. More...

void markCacheVariableInvalid (const SimTK::State &state, const std::string &name) const
Marks the value of a cache variable, identified by name, as invalid. More...

template<class T >
void markCacheVariableInvalid (const SimTK::State &state, const CacheVariable< T > &cv) const
Marks the value of a cache variable as invalid. More...

const ComponentgetOwner () const
Access the owner of this Component. More...

bool hasOwner () const
(For advanced users) Check if this Component has an owner. More...

const ComponentgetRoot () const
Obtain the root Component, which is this component if it is orphaned. 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...

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 Blankevoort1991Ligament Self
This typedef might be useful within the member functions of this class. More...

typedef Force Super
Use this typedef to refer to the superclass of this class. More...

Public Types inherited from OpenSim::Force
typedef Force Self
This typedef might be useful within the member functions of this class. More...

typedef ModelComponent Super
Use this typedef to refer to the superclass of this class. More...

Public Types inherited from OpenSim::ModelComponent
typedef ModelComponent Self
This typedef might be useful within the member functions of this class. More...

typedef Component Super
Use this typedef to refer to the superclass of this class. More...

Public Types inherited from OpenSim::Component
typedef Component 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...

typedef std::map< std::string, SimTK::ClonePtr< AbstractOutput > >::const_iterator OutputConstIterator
Define OutputConstIterator for convenience. More...

## Protected Member Functions

void extendFinalizeFromProperties () override
Perform any time-invariant calculations, data structure initializations, or other configuration based on the component's properties to form a functioning (but not yet connected) component. More...

void extendAddToSystem (SimTK::MultibodySystem &system) const override
Add appropriate Simbody elements (if needed) to the System corresponding to this component and specify needed state resources. More...

double calcSpringForce (const SimTK::State &state) const

double calcDampingForce (const SimTK::State &state) const

double calcTotalForce (const SimTK::State &state) const

double calcInverseForceStrainCurve (double force) const

Protected Member Functions inherited from OpenSim::Force
Force ()
Default constructor sets up Force-level properties; can only be called from a derived class constructor. More...

Force (SimTK::Xml::Element &node)
Deserialization from XML, necessary so that derived classes can (de)serialize. More...

void extendInitStateFromProperties (SimTK::State &state) const override
Subclass should override; be sure to invoke Super::extendInitStateFromProperties() at the beginning of the overriding method. More...

void extendAddToSystem (SimTK::MultibodySystem &system) const override
Default is to create a ForceAdapter which is a SimTK::Force::Custom as the underlying computational component. More...

void extendSetPropertiesFromState (const SimTK::State &state) override
Subclass should override; be sure to invoke Force::extendSetPropertiesFromState() at the beginning of the overriding method. More...

void applyForceToPoint (const SimTK::State &state, const PhysicalFrame &body, const SimTK::Vec3 &point, const SimTK::Vec3 &force, SimTK::Vector_< SimTK::SpatialVec > &bodyForces) const
Apply a force at a particular point (a "station") on a given body. More...

void applyTorque (const SimTK::State &state, const PhysicalFrame &body, const SimTK::Vec3 &torque, SimTK::Vector_< SimTK::SpatialVec > &bodyForces) const
Apply a torque to a particular body. More...

void applyGeneralizedForce (const SimTK::State &state, const Coordinate &coord, double force, SimTK::Vector &generalizedForces) const
Apply a generalized force. More...

void updateFromXMLNode (SimTK::Xml::Element &node, int versionNumber) override
Handle a change in XML syntax for Sockets. More...

Protected Member Functions inherited from OpenSim::ModelComponent
const SimTK::Vec3 & getScaleFactors (const ScaleSet &scaleSet, const Frame &frame) const
Get the scale factors corresponding to the base OpenSim::Body of the specified Frame. More...

virtual void extendPreScale (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...

virtual void extendScale (const SimTK::State &s, const ScaleSet &scaleSet)
Scale the ModelComponent. More...

void updateFromXMLNode (SimTK::Xml::Element &aNode, int versionNumber) override
Handle a change in XML syntax for Sockets. More...

void extendFinalizeFromProperties () override
Perform any time-invariant calculations, data structure initializations, or other configuration based on the component's properties to form a functioning (but not yet connected) component. More...

virtual void extendConnectToModel (Model &model)
Perform any necessary initializations required to connect the component into the Model, and check for error conditions. More...

Protected Member Functions inherited from OpenSim::Component
SimTK_DEFINE_UNIQUE_INDEX_TYPE (MemberSubcomponentIndex)

template<class C = Component>
MemberSubcomponentIndex constructSubcomponent (const std::string &name)
Construct a subcomponent as a data member of this Component. More...

template<class C = Component>
const C & getMemberSubcomponent (MemberSubcomponentIndex ix) const

template<class C = Component>
C & updMemberSubcomponent (MemberSubcomponentIndex ix)

Adopt a component as a subcomponent of this Component. More...

size_t getNumImmediateSubcomponents () const
Get the number of Subcomponents immediately owned by this Component. More...

size_t getNumMemberSubcomponents () const
Get the number of Subcomponents that are data members of this Component. More...

size_t getNumPropertySubcomponents () const
Get the number of Subcomponents that are properties of this Component. More...

Get the number of Subcomponents adopted by this Component. More...

std::vector< SimTK::ReferencePtr< const Component > > getImmediateSubcomponents () const
Access this Component's immediate subcomponents (not those owned by subcomponents) More...

template<class C >
const C * traversePathToComponent (ComponentPath path) const

void setNextSubcomponentInSystem (const Component &sub) const
Helper method to enable Component makers to specify the order of their subcomponents to be added to the System during addToSystem(). More...

void resetSubcomponentOrder ()
resetSubcomponentOrder clears this Component's list of ordered subcomponents (but otherwise leaves subcomponents untouched). More...

const Componentget_components (int i) const
Get the value of the i-th element of the components property. More...

Componentupd_components (int i)
Get a writable reference to the i-th element of the components property. More...

void set_components (int i, const Component &value)
Set the value of the i-th element of components property. More...

int append_components (const Component &value)
Append an element to the components property. More...

Perform any secondary operations, e.g. More...

void initComponentTreeTraversal (const Component &root) const
Build the tree of Components from this component through its descendants. More...

virtual void extendAddToSystemAfterSubcomponents (SimTK::MultibodySystem &system) const
Add appropriate Simbody elements (if needed) to the System after your component's subcomponents have had a chance to add themselves to the system. More...

virtual void computeStateVariableDerivatives (const SimTK::State &s) const
If a model component has allocated any continuous state variables using the addStateVariable() method, then computeStateVariableDerivatives() must be implemented to provide time derivatives for those states. More...

void setStateVariableDerivativeValue (const SimTK::State &state, const std::string &name, double deriv) const
Set the derivative of a state variable by name when computed inside of this Component's computeStateVariableDerivatives() method. More...

virtual void extendRealizeTopology (SimTK::State &state) const
Obtain state resources that are needed unconditionally, and perform computations that depend only on the system topology. More...

virtual void extendRealizeModel (SimTK::State &state) const
Obtain and name state resources (like state variables allocated by an underlying Simbody component) that may be needed, depending on modeling options. More...

virtual void extendRealizeInstance (const SimTK::State &state) const
Perform computations that depend only on instance variables, like lengths and masses. More...

virtual void extendRealizeTime (const SimTK::State &state) const
Perform computations that depend only on time and earlier stages. More...

virtual void extendRealizePosition (const SimTK::State &state) const
Perform computations that depend only on position-level state variables and computations performed in earlier stages (including time). More...

virtual void extendRealizeVelocity (const SimTK::State &state) const
Perform computations that depend only on velocity-level state variables and computations performed in earlier stages (including position, and time). More...

virtual void extendRealizeDynamics (const SimTK::State &state) const
Perform computations (typically forces) that may depend on dynamics-stage state variables, and on computations performed in earlier stages (including velocity, position, and time), but not on other forces, accelerations, constraint multipliers, or reaction forces. More...

virtual void extendRealizeAcceleration (const SimTK::State &state) const
Perform computations that may depend on applied forces. More...

virtual void extendRealizeReport (const SimTK::State &state) const
Perform computations that may depend on anything but are only used for reporting and cannot affect subsequent simulation behavior. More...

void addModelingOption (const std::string &optionName, int maxFlagValue) const
Add a modeling option (integer flag stored in the State) for use by this Component. More...

void addStateVariable (const std::string &stateVariableName, const SimTK::Stage &invalidatesStage=SimTK::Stage::Dynamics, bool isHidden=false) const
Add a continuous system state variable belonging to this Component, and assign a name by which to refer to it. More...

The above method provides a convenient interface to this method, which automatically creates an 'AddedStateVariable' and allocates resources in the SimTK::State for this variable. More...

void addDiscreteVariable (const std::string &discreteVariableName, SimTK::Stage invalidatesStage) const
Add a system discrete variable belonging to this Component, give it a name by which it can be referenced, and declare the lowest Stage that should be invalidated if this variable's value is changed. More...

SimTK::MultibodySystem & updSystem () const
Get writable reference to the MultibodySystem that this component is connected to. More...

int getStateIndex (const std::string &name) const
Get the index of a Component's continuous state variable in the Subsystem for allocations. More...

SimTK::SystemYIndex getStateVariableSystemIndex (const std::string &stateVariableName) const
Get the System Index of a state variable allocated by this Component. More...

const SimTK::DiscreteVariableIndex getDiscreteVariableIndex (const std::string &name) const
Get the index of a Component's discrete variable in the Subsystem for allocations. More...

template<typename T >
PropertyIndex constructSocket (const std::string &name, const std::string &propertyComment)
Construct a specialized Socket for this Component's dependence on another Component. More...

template<typename T , typename CompType = Component>
bool constructOutput (const std::string &name, T(CompType::*const memFunc)(const SimTK::State &) const, const SimTK::Stage &dependsOn=SimTK::Stage::Acceleration)
Construct an output for a member function of the same component. More...

template<typename T , typename CompType = Component>
bool constructOutput (const std::string &name, const T &(CompType::*const memFunc)(const SimTK::State &) const, const SimTK::Stage &dependsOn=SimTK::Stage::Acceleration)
This variant handles component member functions that return the output value by const reference (const T&). More...

template<typename T , typename CompType >
bool constructListOutput (const std::string &name, T(CompType::*const memFunc)(const SimTK::State &, const std::string &channel) const, const SimTK::Stage &dependsOn=SimTK::Stage::Acceleration)
Construct an output that can have multiple channels. More...

bool constructOutputForStateVariable (const std::string &name)
Construct an Output for a StateVariable. More...

template<typename T >
PropertyIndex constructInput (const std::string &name, bool isList, const std::string &propertyComment, const SimTK::Stage &requiredAtStage=SimTK::Stage::Instance)
Construct an Input (socket) for this Component's dependence on an Output signal. More...

template<class T >
CacheVariable< T > addCacheVariable (std::string name, T variablePrototype, SimTK::Stage dependsOnStage) const
Add a state cache entry belonging to this Component to hold calculated values that must be automatically invalidated when certain state values change. More...

void setOwner (const Component &owner)
Set this Component's reference to its owning Component More...

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 Blankevoort1991LigamentsafeDownCast (OpenSim::Object *obj)
For use in MATLAB and Python to access the concrete class. More...

static const std::string & getClassName ()
This returns "Blankevoort1991Ligament". More...

void assign (Object &aObject) override
This allows copy assignment in the Java GUI. More...

Blankevoort1991Ligamentclone () 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...

Static Public Member Functions inherited from OpenSim::Force
static ForcesafeDownCast (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 ModelComponentsafeDownCast (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 ComponentsafeDownCast (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 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...

Static Protected Member Functions inherited from OpenSim::Component
static void prependComponentPathToConnecteePath (Component &subcomponent)
For internal use. More...

Protected Attributes inherited from OpenSim::Force
SimTK::ResetOnCopy< SimTK::ForceIndex > _index
ID for the force in Simbody. More...

Protected Attributes inherited from OpenSim::ModelComponent
SimTK::ReferencePtr< Model_model
The model this component belongs to. More...

Protected Attributes inherited from OpenSim::Object
PropertySet _propertySet
OBSOLETE: Property_Deprecated set for serializable member variables of this and derived classes. More...

Static Protected Attributes inherited from OpenSim::ModelComponent
static const SimTK::Vec3 InvalidScaleFactors
Returned by getScaleFactors() if the ScaleSet does not contain scale factors for the base Body associated with the specified Frame. More...

## Detailed Description

This class implements a nonlinear spring ligament model introduced by Blankevoort et al. (1991) [1] and further described in Smith et al. (2016) [2].

This model is partially based on the formulation orginally proposed by Wismans et al. (1980) [3]. The ligament is represented as a passive spring with the force-strain relationship described by a quadratic "toe" region at low strains and a linear region at high strains. The toe region represents the uncrimping and alignment of collagen fibers and the linear region represents the subsequent stretching of the aligned fibers. The ligament model also includes a damping force that is only applied if the ligament is stretched beyond the slack length and if the ligament is lengthening. The length of the ligament is $$l$$.

Governing Equations

Spring Force:

$F_{\mathrm{spring}} = \begin{Bmatrix} 0 & \epsilon < 0 \\ \frac{1}{2\epsilon_t }k\epsilon^2 & 0 \leq \epsilon \leq \epsilon_t \\ k(\epsilon - \frac{\epsilon_t}{2})& \epsilon > \epsilon_t \end{Bmatrix}$

Damping Force:

$F_{\mathrm{damping}} = \begin{Bmatrix} c\cdot \dot{\epsilon} & \epsilon > 0 \: and \: \dot{\epsilon} > 0 \\ 0 & otherwise \end{Bmatrix}$

Total Force:

$F_{\mathrm{total}} = F_{\mathrm{spring}} + F_{\mathrm{damping}}$

This Force component has the following properties:

• linear stiffness (k): The force/strain (e.g. N) stiffness of the linear region of the ligament model.
• slack_length ( $$l_0$$): The resting length of the ligament (e.g. m).
• damping coefficient (c): Damping coefficient used in the damping force calculation in units of force*time/strain (e.g. N*s/strain). The default value is 0.003.
• transition_strain ( $$\epsilon_t$$): The strain value where the ligament model transitions from the quadratic toe region to the linear stiffness region. The default value is 0.06 (6%) according to Blankevoort (1991) [1]. This value is widely used in the multibody knee modeling literature [2,4,5,6] and also agrees with some experimental studies [7]. However, other literature suggests the transition strain of ligaments occurs at around 0.03 (3%) strain [8,9]. In reality, the transition strain is likely dependent on the strain rate [10,11], however this effect is not included in this implementation.

The Blankevoort1991Ligament implementation is intended to be compatible with common methods in the literature for parameterizing ligament properties. The zero-load length of the ligament is parameterized by the slack_length property, which can be set directly, in meters, using set_slack_length(), or using setSlackLengthFromReferenceStrain() and setSlackLengthFromReferenceForce(). Here, reference strain and reference force are the strain or force in the ligament at a reference pose (state). If you want to compute the strain or force of the ligament in a given pose (state), you can use the getStrain() and getForce() methods. The linear_stiffness property has units of force/strain (newton) but can be set and obtained in units of force/length (newton/meter) using setLinearStiffnessForcePerLength() and getLinearStiffnessForcePerLength().

When scaling a model (using the ScaleTool) that contains a Blankevoort1991Ligament, the slack_length property is scaled by the ratio of the entire GeometryPath length in the default model pose before and after scaling the bone geometries. This ensures that the strain in the ligament in the default pose is equivilent before and after scaling. Thus, it is important to consider the order of scaling the model and setting the slack_length property for your specific application. The linear_stiffness property is not affected by scaling the model.

[1] Blankevoort, L. and Huiskes, R., (1991). Ligament-bone interaction in a three-dimensional model of the knee. J Biomech Eng, 113(3), 263-269

[2] Smith, C.R., Lenhart, R.L., Kaiser, J., Vignos, M.F. and Thelen, D.G., (2016). Influence of ligament properties on tibiofemoral mechanics in walking. J Knee Surg, 29(02), 99-106.

[3] Wismans, J.A.C., Veldpaus, F., Janssen, J., Huson, A. and Struben, P., (1980). A three-dimensional mathematical model of the knee-joint. J Biomech, 13(8), 677-685.

[4] Marra, M. A., Vanheule, V., Fluit, R., Koopman, B. H., Rasmussen, J., Verdonschot, N., & Andersen, M. S. (2015). A subject-specific musculoskeletal modeling framework to predict in vivo mechanics of total knee arthroplasty. Journal of biomechanical engineering, 137(2), 020904.

[5] Guess, T. M., Razu, S., & Jahandar, H. (2016). Evaluation of knee ligament mechanics using computational models. The journal of knee surgery, 29(02), 126-137.

[6] Li, G., Gil, J., Kanamori, A., & Woo, S. Y. (1999). A validated three-dimensional computational model of a human knee joint. Journal of biomechanical engineering, 121(6), 657-662.

[7] Ristaniemi, A., Stenroth, L., Mikkonen, S., & Korhonen, R. K. (2018). Comparison of elastic, viscoelastic and failure tensile material properties of knee ligaments and patellar tendon. Journal of biomechanics, 79, 31-38.

[8] Weiss, J. A., & Gardiner, J. C. (2001). Computational modeling of ligament mechanics. Critical Reviews in Biomedical Engineering, 29(3).

[9] Martin, R. B., Burr, D. B., Sharkey, N. A., & Fyhrie, D. P. (2015). Mechanical properties of ligament and tendon. In Skeletal Tissue Mechanics (pp. 175-225). Springer, New York, NY.

[10] Pioletti, D. P., Rakotomanana, L. R., Benvenuti, J. F., & Leyvraz, P. F. (1998). Viscoelastic constitutive law in large deformations: application to human knee ligaments and tendons. Journal of biomechanics, 31(8), 753-757.

[11] Pioletti, D. P., Rakotomanana, L. R., & Leyvraz, P. F. (1999). Strain rate effect on the mechanical behavior of the anterior cruciate ligament-bone complex. Medical Engineering & Physics, 21(2), 95-100.

[12] Galbusera, F., Freutel, M., Durselen, L., D'Aiuto, M., Croce, D., Villa, T., Sansone, V. & Innocenti, B. (2014). Material models and properties in the finite element analysis of knee ligaments: a literature review. Frontiers in bioengineering and biotechnology, 2, 54.

## ◆ 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.

## ◆ Blankevoort1991Ligament() [1/4]

 OpenSim::Blankevoort1991Ligament::Blankevoort1991Ligament ( )

## ◆ Blankevoort1991Ligament() [2/4]

 OpenSim::Blankevoort1991Ligament::Blankevoort1991Ligament ( std::string name, const PhysicalFrame & frame1, SimTK::Vec3 point1, const PhysicalFrame & frame2, SimTK::Vec3 point2 )

## ◆ Blankevoort1991Ligament() [3/4]

 OpenSim::Blankevoort1991Ligament::Blankevoort1991Ligament ( std::string name, const PhysicalFrame & frame1, SimTK::Vec3 point1, const PhysicalFrame & frame2, SimTK::Vec3 point2, double linear_stiffness, double slack_length )

## ◆ Blankevoort1991Ligament() [4/4]

 OpenSim::Blankevoort1991Ligament::Blankevoort1991Ligament ( std::string name, double linear_stiffness, double slack_length )

## ◆ assign()

 void OpenSim::Blankevoort1991Ligament::assign ( Object & aObject )
inlineoverride

This allows copy assignment in the Java GUI.

Exceptions
 Exception if the argument is not of type Blankevoort1991Ligament.

## ◆ calcDampingForce()

 double OpenSim::Blankevoort1991Ligament::calcDampingForce ( const SimTK::State & state ) const
protected

## ◆ calcInverseForceStrainCurve()

 double OpenSim::Blankevoort1991Ligament::calcInverseForceStrainCurve ( double force ) const
protected

## ◆ calcSpringForce()

 double OpenSim::Blankevoort1991Ligament::calcSpringForce ( const SimTK::State & state ) const
protected

## ◆ calcTotalForce()

 double OpenSim::Blankevoort1991Ligament::calcTotalForce ( const SimTK::State & state ) const
protected

## ◆ clone()

 Blankevoort1991Ligament* OpenSim::Blankevoort1991Ligament::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::Force.

## ◆ computeForce()

 void OpenSim::Blankevoort1991Ligament::computeForce ( const SimTK::State & state, SimTK::Vector_< SimTK::SpatialVec > & bodyForces, SimTK::Vector & generalizedForces ) const
overridevirtual

Subclasses must implement this method to compute the forces that should be applied to bodies and generalized speeds.

This is invoked by ForceAdapter to perform the force computation.

Reimplemented from OpenSim::Force.

## ◆ computeMomentArm()

 double OpenSim::Blankevoort1991Ligament::computeMomentArm ( const SimTK::State & s, Coordinate & aCoord ) const

## ◆ computePotentialEnergy()

 double OpenSim::Blankevoort1991Ligament::computePotentialEnergy ( const SimTK::State & state ) const
overridevirtual

Subclasses may optionally override this method to compute a contribution to the potential energy of the system.

The default implementation returns 0, which is appropriate for forces that do not contribute to potential energy.

Reimplemented from OpenSim::Force.

 void OpenSim::Blankevoort1991Ligament::extendAddToSystem ( SimTK::MultibodySystem & system ) const
overrideprotectedvirtual

Add appropriate Simbody elements (if needed) to the System corresponding to this component and specify needed state resources.

extendAddToSystem() is called when the Simbody System is being created to represent a completed system (model) for computation. That is, connect() will already have been invoked on all components before any addToSystem() call is made. Helper methods for adding modeling options, state variables and their derivatives, discrete variables, and cache entries are available and can be called within extendAddToSystem() only.

Note that this method is const; you may not modify your model component or the containing model during this call. Any modifications you need should instead be performed in finalizeFromProperties() or at the latest connect(), which are non-const. The only exception is that you may need to record access information for resources you create in the system, such as an index number. For most Components, OpenSim base classes either provide convenience methods or handle indices automatically. Otherwise, you must declare indices as mutable data members so that you can set them here.

If you override this method, be sure to invoke the base class method at the beginning, using code like this:

// ... your code goes here
}

This method assumes that this Component's addToSystem will be invoked before its subcomponents. If you need your subcomponents to be added to the system, first (e.g. require of a Force to be anchored to a SimTK::MobilizedBody specified by subcomponents) then you must implement: extendAddToSystemAfterSubcomponents(). It is possible to implement both method to add system elements before and then after your subcomponents have added themselves. Caution is required that Simbody elements are not added twice especially when order is unimportant.

Parameters
 [in,out] system The MultibodySystem being added to.

Reimplemented from OpenSim::Component.

## ◆ extendFinalizeFromProperties()

 void OpenSim::Blankevoort1991Ligament::extendFinalizeFromProperties ( )
overrideprotectedvirtual

Perform any time-invariant calculations, data structure initializations, or other configuration based on the component's properties to form a functioning (but not yet connected) component.

For example, each property should be checked to ensure that its value is within an acceptable range. When this method returns, the component will be marked as being up-to-date with its properties. Do not perform any configuration that depends on the SimTK::MultibodySystem; it is not available at this point.

If you override this method, be sure to invoke the base class method first, using code like this:

void MyComponent::extendFinalizeFromProperties() {
Super::extendFinalizeFromProperties(); // invoke parent class method
// ... your code goes here
// ... catch invalid property values
// ... initialize any internal data structures
}

Reimplemented from OpenSim::Component.

## ◆ extendPostScale()

 void OpenSim::Blankevoort1991Ligament::extendPostScale ( const SimTK::State & s, const ScaleSet & scaleSet )
overridevirtual

Perform any computations that must occur after ModelComponent::scale() has been invoked on all ModelComponents in the Model.

This method is virtual and may be implemented by any subclass of ModelComponent, but all implementations must begin with a call to Super::extendPostScale() to execute the parent class methods before the child class method. The base class implementation in ModelComponent does nothing.

postScale()

Reimplemented from OpenSim::ModelComponent.

## ◆ get_damping_coefficient()

 const double& OpenSim::Blankevoort1991Ligament::get_damping_coefficient ( ) const
inline

Get the value of the damping_coefficient property.

## ◆ get_GeometryPath()

 const GeometryPath& OpenSim::Blankevoort1991Ligament::get_GeometryPath ( ) const
inline

Get the value of the GeometryPath property.

## ◆ get_linear_stiffness()

 const double& OpenSim::Blankevoort1991Ligament::get_linear_stiffness ( ) const
inline

Get the value of the linear_stiffness property.

## ◆ get_slack_length()

 const double& OpenSim::Blankevoort1991Ligament::get_slack_length ( ) const
inline

Get the value of the slack_length property.

## ◆ get_transition_strain()

 const double& OpenSim::Blankevoort1991Ligament::get_transition_strain ( ) const
inline

Get the value of the transition_strain property.

## ◆ getClassName()

 static const std::string& OpenSim::Blankevoort1991Ligament::getClassName ( )
inlinestatic

This returns "Blankevoort1991Ligament".

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::Blankevoort1991Ligament::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.

getClassName()

Implements OpenSim::Force.

## ◆ getDampingCoefficientForceTimePerLength()

 double OpenSim::Blankevoort1991Ligament::getDampingCoefficientForceTimePerLength ( ) const

Get the damping_coefficient in units of force*time/length (N*s/m)

## ◆ getDampingForce()

 double OpenSim::Blankevoort1991Ligament::getDampingForce ( const SimTK::State & state ) const

## ◆ getLength()

 double OpenSim::Blankevoort1991Ligament::getLength ( const SimTK::State & state ) const

## ◆ getLengtheningSpeed()

 double OpenSim::Blankevoort1991Ligament::getLengtheningSpeed ( const SimTK::State & state ) const

## ◆ getLinearStiffnessForcePerLength()

 double OpenSim::Blankevoort1991Ligament::getLinearStiffnessForcePerLength ( ) const

Get the linear_stiffness property in units of force/length (N/m)

## ◆ getRecordLabels()

 OpenSim::Array OpenSim::Blankevoort1991Ligament::getRecordLabels ( ) const
overridevirtual

Methods to query a Force for the value actually applied during simulation.

The names of the quantities (column labels) is returned by this first function getRecordLabels().

Reimplemented from OpenSim::Force.

## ◆ getRecordValues()

 OpenSim::Array OpenSim::Blankevoort1991Ligament::getRecordValues ( const SimTK::State & state ) const
overridevirtual

Given SimTK::State object extract all the values necessary to report forces, application location frame, etc.

used in conjunction with getRecordLabels and should return same size Array.

Reimplemented from OpenSim::Force.

## ◆ getSpringForce()

 double OpenSim::Blankevoort1991Ligament::getSpringForce ( const SimTK::State & state ) const

## ◆ getStrain()

 double OpenSim::Blankevoort1991Ligament::getStrain ( const SimTK::State & state ) const

## ◆ getStrainRate()

 double OpenSim::Blankevoort1991Ligament::getStrainRate ( const SimTK::State & state ) const

## ◆ getTotalForce()

 double OpenSim::Blankevoort1991Ligament::getTotalForce ( const SimTK::State & state ) const

## ◆ getTransitionLength()

 double OpenSim::Blankevoort1991Ligament::getTransitionLength ( ) const

Get the length (m) of the ligament where the model transitions from the toe region to the linear region.

This corresponds to the length of the ligament at the transistion_strain.

## ◆ safeDownCast()

 static Blankevoort1991Ligament* OpenSim::Blankevoort1991Ligament::safeDownCast ( OpenSim::Object * obj )
inlinestatic

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

Example: cObj = Blankevoort1991Ligament.safeDownCast(obj). This is equivalent to dynamic_cast<Blankevoort1991Ligament*>(obj)` in C++.

## ◆ set_damping_coefficient()

 void OpenSim::Blankevoort1991Ligament::set_damping_coefficient ( const double & value )
inline

Set the value of the damping_coefficient property.

## ◆ set_GeometryPath()

 void OpenSim::Blankevoort1991Ligament::set_GeometryPath ( const GeometryPath & value )
inline

Set the value of the GeometryPath property.

## ◆ set_linear_stiffness()

 void OpenSim::Blankevoort1991Ligament::set_linear_stiffness ( const double & value )
inline

Set the value of the linear_stiffness property.

## ◆ set_slack_length()

 void OpenSim::Blankevoort1991Ligament::set_slack_length ( const double & value )
inline

Set the value of the slack_length property.

## ◆ set_transition_strain()

 void OpenSim::Blankevoort1991Ligament::set_transition_strain ( const double & value )
inline

Set the value of the transition_strain property.

## ◆ setDampingCoefficientForceTimePerLength()

 void OpenSim::Blankevoort1991Ligament::setDampingCoefficientForceTimePerLength ( double damping_coefficient )

Set the damping_coefficient property using a value in units of force*time/length (N*s/m).

Note that scaling the model keeps the damping_coefficient property (in units force*time/strain) constant, thus the damping_coefficient in units of force*time/length input to this function will be altered by scaling.

## ◆ setLinearStiffnessForcePerLength()

 void OpenSim::Blankevoort1991Ligament::setLinearStiffnessForcePerLength ( double linear_stiffness )

Set the linear_stiffness property using a value in units of force/length (N/m).

Note that scaling the model keeps the linear_stiffness property (in units of force/strain) constant, thus the linear_stiffness in units of force/length input to this function will be altered by scaling.

## ◆ setSlackLengthFromReferenceForce()

 void OpenSim::Blankevoort1991Ligament::setSlackLengthFromReferenceForce ( double force, const SimTK::State & reference_state )

Set the slack_length property using the absolute spring force (N) in the ligament at a known pose (reference force).

Note that scaling the model will adjust the slack_length property, thus it is important to consider the order of scaling and using this function for your application.

## ◆ setSlackLengthFromReferenceStrain()

 void OpenSim::Blankevoort1991Ligament::setSlackLengthFromReferenceStrain ( double strain, const SimTK::State & reference_state )

Set the slack_length property using the strain in the ligament at a known pose (reference state).

Note that scaling the model will adjust the slack length property to hold the input reference strain constant if the input reference_state is equal to the default model pose (generated by initSystem()).

## ◆ upd_damping_coefficient()

 double& OpenSim::Blankevoort1991Ligament::upd_damping_coefficient ( )
inline

Get a writable reference to the damping_coefficient property.

## ◆ upd_GeometryPath()

 GeometryPath& OpenSim::Blankevoort1991Ligament::upd_GeometryPath ( )
inline

Get a writable reference to the GeometryPath property.

## ◆ upd_linear_stiffness()

 double& OpenSim::Blankevoort1991Ligament::upd_linear_stiffness ( )
inline

Get a writable reference to the linear_stiffness property.

## ◆ upd_slack_length()

 double& OpenSim::Blankevoort1991Ligament::upd_slack_length ( )
inline

Get a writable reference to the slack_length property.

## ◆ upd_transition_strain()

 double& OpenSim::Blankevoort1991Ligament::upd_transition_strain ( )
inline

Get a writable reference to the transition_strain property.

## ◆ damping_coefficient

 double OpenSim::Blankevoort1991Ligament::damping_coefficient

"The coefficient that multiplies the strain rate when computing the " " damping force. Units of N*s/strain. Default value of 0.003."

This property appears in XML files under the tag <damping_coefficient>. This property was generated with the OpenSim_DECLARE_PROPERTY macro; see Property to learn about the property system.

get_damping_coefficient(), upd_damping_coefficient(), set_damping_coefficient()

## ◆ damping_force

 double OpenSim::Blankevoort1991Ligament::damping_force

Provides the value of getDampingForce() and is available at stage SimTK::Stage::Velocity .

This output was generated with the OpenSim_DECLARE_OUTPUT macro.

## ◆ GeometryPath

 GeometryPath OpenSim::Blankevoort1991Ligament::GeometryPath

"The set of points defining the path of the ligament"

This property appears in XML files under the tag <GeometryPath>. This property was generated with the OpenSim_DECLARE_UNNAMED_PROPERTY macro; see Property to learn about the property system.

get_GeometryPath(), upd_GeometryPath(), set_GeometryPath()

## ◆ length

 double OpenSim::Blankevoort1991Ligament::length

Provides the value of getLength() and is available at stage SimTK::Stage::Position .

This output was generated with the OpenSim_DECLARE_OUTPUT macro.

## ◆ lengthening_speed

 double OpenSim::Blankevoort1991Ligament::lengthening_speed

Provides the value of getLengtheningSpeed() and is available at stage SimTK::Stage::Velocity .

This output was generated with the OpenSim_DECLARE_OUTPUT macro.

## ◆ linear_stiffness

 double OpenSim::Blankevoort1991Ligament::linear_stiffness

"The slope of the linear region of the force-strain curve. " "Units of force/strain (N)."

This property appears in XML files under the tag <linear_stiffness>. This property was generated with the OpenSim_DECLARE_PROPERTY macro; see Property to learn about the property system.

get_linear_stiffness(), upd_linear_stiffness(), set_linear_stiffness()

## ◆ slack_length

 double OpenSim::Blankevoort1991Ligament::slack_length

"The length at which ligament begins developing tension. Units of m."

This property appears in XML files under the tag <slack_length>. This property was generated with the OpenSim_DECLARE_PROPERTY macro; see Property to learn about the property system.

get_slack_length(), upd_slack_length(), set_slack_length()

## ◆ spring_force

 double OpenSim::Blankevoort1991Ligament::spring_force

Provides the value of getSpringForce() and is available at stage SimTK::Stage::Position .

This output was generated with the OpenSim_DECLARE_OUTPUT macro.

## ◆ strain

 double OpenSim::Blankevoort1991Ligament::strain

Provides the value of getStrain() and is available at stage SimTK::Stage::Position .

This output was generated with the OpenSim_DECLARE_OUTPUT macro.

## ◆ strain_rate

 double OpenSim::Blankevoort1991Ligament::strain_rate

Provides the value of getStrainRate() and is available at stage SimTK::Stage::Velocity .

This output was generated with the OpenSim_DECLARE_OUTPUT macro.

## ◆ total_force

 double OpenSim::Blankevoort1991Ligament::total_force

Provides the value of getTotalForce() and is available at stage SimTK::Stage::Velocity .

This output was generated with the OpenSim_DECLARE_OUTPUT macro.

## ◆ transition_strain

 double OpenSim::Blankevoort1991Ligament::transition_strain

"The strain at which the ligament force-strain curve transitions from " "quadratic to linear. Units of strain. Default value of 0.06 (6%)."

This property appears in XML files under the tag <transition_strain>. This property was generated with the OpenSim_DECLARE_PROPERTY macro; see Property to learn about the property system.