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SimTK::Force::DiscreteForces Class Reference

Arbitrary discrete body forces and mobility (generalized) forces. Useful for applying external forces or forces that are updated at discrete times due to the occurrence of events. More...

#include <Force_DiscreteForces.h>

+ Inheritance diagram for SimTK::Force::DiscreteForces:

Public Member Functions

 DiscreteForces (GeneralForceSubsystem &forces, const SimbodyMatterSubsystem &matter)
 Create a DiscreteForces force element. More...
 
 DiscreteForces ()
 Default constructor creates an empty handle. More...
 
void clearAllForces (State &state) const
 Set to zero all forces stored by this force element in the given state, including both generalized forces and body spatial forces. More...
 
void clearAllMobilityForces (State &state) const
 Set to zero all generalized forces stored by this force element in the given state. More...
 
void clearAllBodyForces (State &state) const
 Set to zero all body spatial forces (force and torques) stored by this force element in the given state. More...
 
void setOneMobilityForce (State &state, const MobilizedBody &mobod, MobilizerUIndex whichU, Real force) const
 Change the value of a generalized force to be applied in the given state. More...
 
void setOneBodyForce (State &state, const MobilizedBody &mobod, const SpatialVec &spatialForceInG) const
 Change the value of the discrete spatial force (force and torque) to be applied to a body in the given state. More...
 
void addForceToBodyPoint (State &state, const MobilizedBody &mobod, const Vec3 &pointInB, const Vec3 &forceInG) const
 Convenience method to add in a force applied at a point (station) on a particular body into the forces currently set to be applied to that body in this state. More...
 
void setAllMobilityForces (State &state, const Vector &f) const
 Set all the generalized forces at once. More...
 
void setAllBodyForces (State &state, const Vector_< SpatialVec > &bodyForcesInG) const
 Set all the body spatial forces at once. More...
 
Real getOneMobilityForce (const State &state, const MobilizedBody &mobod, MobilizerUIndex whichU) const
 Return the value for a generalized force that is stored in the given state. More...
 
SpatialVec getOneBodyForce (const State &state, const MobilizedBody &mobod) const
 Return the value for the discrete spatial force (force and torque) on a particular body that is stored in the given state. More...
 
const VectorgetAllMobilityForces (const State &state) const
 Get a reference to the internal Vector of all the generalized forces currently set to be applied by this force element. More...
 
const Vector_< SpatialVec > & getAllBodyForces (const State &state) const
 Get a reference to the internal Vector of all the body spatial forces currently set to be applied by this force element. More...
 
- Public Member Functions inherited from SimTK::Force
void disable (State &) const
 Disable this force element, effectively removing it from the System for computational purposes (it is still using its ForceIndex, however). More...
 
void enable (State &) const
 Enable this force element if it was previously disabled. More...
 
bool isDisabled (const State &) const
 Test whether this force element is currently disabled in the supplied State. More...
 
void setDisabledByDefault (bool shouldBeDisabled)
 Normally force elements are enabled when defined and can be disabled later. More...
 
bool isDisabledByDefault () const
 Test whether this force element is disabled by default in which case it must be explicitly enabled before it will take effect. More...
 
void calcForceContribution (const State &state, Vector_< SpatialVec > &bodyForces, Vector_< Vec3 > &particleForces, Vector &mobilityForces) const
 Calculate the force that would be applied by this force element if the given state were realized to Dynamics stage. More...
 
Real calcPotentialEnergyContribution (const State &state) const
 Calculate the potential energy contribution that is made by this force element at the given state. More...
 
 Force ()
 Default constructor for Force handle base class does nothing. More...
 
 operator ForceIndex () const
 Implicit conversion to ForceIndex when needed. More...
 
const GeneralForceSubsystemgetForceSubsystem () const
 Get the GeneralForceSubsystem of which this Force is an element. More...
 
ForceIndex getForceIndex () const
 Get the index of this force element within its parent force subsystem. More...
 
- Public Member Functions inherited from SimTK::PIMPLHandle< Force, ForceImpl, true >
bool isEmptyHandle () const
 Returns true if this handle is empty, that is, does not refer to any implementation object. More...
 
bool isOwnerHandle () const
 Returns true if this handle is the owner of the implementation object to which it refers. More...
 
bool isSameHandle (const Force &other) const
 Determine whether the supplied handle is the same object as "this" PIMPLHandle. More...
 
void disown (Force &newOwner)
 Give up ownership of the implementation to an empty handle. More...
 
PIMPLHandlereferenceAssign (const Force &source)
 "Copy" assignment but with shallow (pointer) semantics. More...
 
PIMPLHandlecopyAssign (const Force &source)
 This is real copy assignment, with ordinary C++ object ("value") semantics. More...
 
void clearHandle ()
 Make this an empty handle, deleting the implementation object if this handle is the owner of it. More...
 
const ForceImpl & getImpl () const
 Get a const reference to the implementation associated with this Handle. More...
 
ForceImpl & updImpl ()
 Get a writable reference to the implementation associated with this Handle. More...
 
int getImplHandleCount () const
 Return the number of handles the implementation believes are referencing it. More...
 

Additional Inherited Members

- Public Types inherited from SimTK::PIMPLHandle< Force, ForceImpl, true >
typedef PIMPLHandle< Force,
ForceImpl, PTR > 
HandleBase
 
typedef HandleBase ParentHandle
 
- Protected Member Functions inherited from SimTK::Force
 Force (ForceImpl *r)
 Use this in a derived Force handle class constructor to supply the concrete implementation object to be stored in the handle base. More...
 
- Protected Member Functions inherited from SimTK::PIMPLHandle< Force, ForceImpl, true >
 PIMPLHandle ()
 The default constructor makes this an empty handle. More...
 
 PIMPLHandle (ForceImpl *p)
 This provides consruction of a handle referencing an existing implementation object. More...
 
 PIMPLHandle (const PIMPLHandle &source)
 The copy constructor makes either a deep (value) or shallow (reference) copy of the supplied source PIMPL object, based on whether this is a "pointer semantics" (PTR=true) or "object (value) semantics" (PTR=false, default) class. More...
 
 ~PIMPLHandle ()
 Note that the destructor is non-virtual. More...
 
PIMPLHandleoperator= (const PIMPLHandle &source)
 Copy assignment makes the current handle either a deep (value) or shallow (reference) copy of the supplied source PIMPL object, based on whether this is a "pointer sematics" (PTR=true) or "object (value) semantics" (PTR=false, default) class. More...
 
void setImpl (ForceImpl *p)
 Set the implementation for this empty handle. More...
 
bool hasSameImplementation (const Force &other) const
 Determine whether the supplied handle is a reference to the same implementation object as is referenced by "this" PIMPLHandle. More...
 

Detailed Description

Arbitrary discrete body forces and mobility (generalized) forces. Useful for applying external forces or forces that are updated at discrete times due to the occurrence of events.

See Also
Force::MobilityDiscreteForce

Constructor & Destructor Documentation

Create a DiscreteForces force element.

Parameters
forcesSubsystem to which this force element should be added.
matterSubsystem containing the mobilized bodies to which these forces will be applied.

Default constructor creates an empty handle.

Member Function Documentation

void SimTK::Force::DiscreteForces::clearAllForces ( State state) const
inline

Set to zero all forces stored by this force element in the given state, including both generalized forces and body spatial forces.

void SimTK::Force::DiscreteForces::clearAllMobilityForces ( State state) const

Set to zero all generalized forces stored by this force element in the given state.

void SimTK::Force::DiscreteForces::clearAllBodyForces ( State state) const

Set to zero all body spatial forces (force and torques) stored by this force element in the given state.

void SimTK::Force::DiscreteForces::setOneMobilityForce ( State state,
const MobilizedBody mobod,
MobilizerUIndex  whichU,
Real  force 
) const

Change the value of a generalized force to be applied in the given state.

Set this to zero if you don't want it to do anything. You can call this method any time after realizeTopology() since the force just needs to be saved in the state.

Parameters
stateThe state in which the generalized force is to be saved.
mobodThe mobilizer to which the force should be applied.
whichUTo which of the mobilizer's mobilities (degrees of freedom) should this force be applied (first is 0)?
forceThe scalar value of the generalized force.
See Also
getOneMobilityForce()
void SimTK::Force::DiscreteForces::setOneBodyForce ( State state,
const MobilizedBody mobod,
const SpatialVec spatialForceInG 
) const

Change the value of the discrete spatial force (force and torque) to be applied to a body in the given state.

Set this to zero if you don't want any force applied to the body. You can call this method any time after realizeTopology() since the force just needs to be saved in the state.

Parameters
stateThe state in which the force is to be saved.
mobodThe mobilized body to which the force should be applied.
spatialForceInGThe (torque,force) pair as a SpatialVec. These are expressed in the Ground frame and the force is applied to the body origin.
See Also
getOneBodyForce(), addForceToBodyPoint()
void SimTK::Force::DiscreteForces::addForceToBodyPoint ( State state,
const MobilizedBody mobod,
const Vec3 pointInB,
const Vec3 forceInG 
) const

Convenience method to add in a force applied at a point (station) on a particular body into the forces currently set to be applied to that body in this state.

The station location is given in the body frame and the force is given in the Ground frame. Note that the state must have been realized to Stage::Position because we need to know the body orientation in order to shift the applied force to the body origin.

Be sure to call setOneBodyForce() to initialize this force to zero before you start accumulating point forces using this method.

Parameters
stateThe state in which the force is saved. Must already have been realized to at least Stage::Position.
mobodThe mobilized body to which the force will be applied.
pointInBThe body station at which the force will be applied, measured and expressed in the body frame.
forceInGThe force vector to be applied, expressed in Ground.
See Also
setOneBodyForce()
void SimTK::Force::DiscreteForces::setAllMobilityForces ( State state,
const Vector f 
) const

Set all the generalized forces at once.

These will be applied until they are changed.

Parameters
stateThe state in which the generalized forces are saved.
fThe set of n generalized forces. This Vector must be either empty (in which case it is treated as though it were all zero) or the same length as the number of generalized speeds (state.getNU()).
See Also
clearAllMobilityForces()
void SimTK::Force::DiscreteForces::setAllBodyForces ( State state,
const Vector_< SpatialVec > &  bodyForcesInG 
) const

Set all the body spatial forces at once.

These will be applied until they are changed.

Parameters
stateThe state in which the forces are saved.
bodyForcesInGThe set of nb spatial forces (torque,force) pairs, expressed in the Ground frame, with the forces applied at each body frame origin. This Vector must be either empty (in which case it is treated as though it were all zero) or the same length as the number of mobilized bodies in the system (and don't forget that Ground is mobilized body 0).
See Also
clearAllBodyForces()
Real SimTK::Force::DiscreteForces::getOneMobilityForce ( const State state,
const MobilizedBody mobod,
MobilizerUIndex  whichU 
) const

Return the value for a generalized force that is stored in the given state.

If no calls to setGeneralizedForce() have been made on this state then zero will be returned.

See Also
setOneMobilityForce()
SpatialVec SimTK::Force::DiscreteForces::getOneBodyForce ( const State state,
const MobilizedBody mobod 
) const

Return the value for the discrete spatial force (force and torque) on a particular body that is stored in the given state.

The result is a force applied at the body origin and expressed in the Ground frame.

See Also
setOneBodyForce()
const Vector& SimTK::Force::DiscreteForces::getAllMobilityForces ( const State state) const

Get a reference to the internal Vector of all the generalized forces currently set to be applied by this force element.

This will be length zero if no forces are being applied; otherwise, its length will be the number of generalized speeds u in the given state. The returned reference is a reference into the given state object.

const Vector_<SpatialVec>& SimTK::Force::DiscreteForces::getAllBodyForces ( const State state) const

Get a reference to the internal Vector of all the body spatial forces currently set to be applied by this force element.

This will be length zero if no body forces are being applied; otherwise, its length will be the number of mobilized bodies in the containing MultibodySystem. The returned reference is a reference into the given state object.


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