A discrete mobility (generalized) force f applied to a particular mobility that is specified at construction. Useful for applying external forces or forces that are updated at discrete times due to the occurrence of events. More...

#include <Force_MobilityDiscreteForce.h>

Inheritance diagram for SimTK::Force::MobilityDiscreteForce:

List of all members.

Public Member Functions
	MobilityDiscreteForce (GeneralForceSubsystem &forces, const MobilizedBody &mobod, MobilizerUIndex whichU, Real defaultForce=0)
	Create a MobilityDiscreteForce.
	MobilityDiscreteForce (GeneralForceSubsystem &forces, const MobilizedBody &mobod, Real defaultForce=0)
	Alternate constructor signature for when the mobilizer has only a single generalized speed, in which case we'll use MobilizerUIndex(0).
	MobilityDiscreteForce ()
	Default constructor creates an empty handle.
MobilityDiscreteForce &	setDefaultMobilityForce (Real defaultForce)
	Provide a new value for the defaultForce, overriding the one provided in the constructor.
Real	getDefaultMobilityForce () const
	Return the value that this generalized force will have by default.
void	setMobilityForce (State &state, Real f) const
	Change the value of the generalized force to be applied in the given state.
Real	getMobilityForce (const State &state) const
	Return the value for this generalized force that is stored in the given state.

Detailed Description

A discrete mobility (generalized) force f applied to a particular mobility that is specified at construction. Useful for applying external forces or forces that are updated at discrete times due to the occurrence of events.

Note that a mobility is a generalized speed (u), not a generalized coordinate (q). The meaning of a generalized force depends on the definition of the generalized speed. If that speed is a translation then this is a force; if a rotation then this is a torque; if something else then f has a comparable definition (the defining condition is that f*u should always have physically meaningful units of power). This force does not contribute to the potential energy, so adding it to a system will cause potential+kinetic energy not to be conserved.

If you want to be able to apply discrete forces to any body or mobilizer specifying which one in advance, see Force::DiscreteForces.

See also:: Force::DiscreteForces

Constructor & Destructor Documentation

SimTK::Force::MobilityDiscreteForce::MobilityDiscreteForce	(	GeneralForceSubsystem &	forces,
		const MobilizedBody &	mobod,
		MobilizerUIndex	whichU,
		Real	defaultForce = `0`
	)

Create a MobilityDiscreteForce.

Parameters:

forces	subsystem to which this force element should be added
mobod	mobilizer to which the force should be applied
whichU	to which of the mobilizer's mobilities (degrees of freedom) should this force be applied (first is 0)?
defaultForce	initial value for the generalized force to be applied (default 0)

Note that if you have an integer value for the generalized speed (u) index, you have to cast it to a MobilizerUIndex here. The generalized speeds are numbered starting with 0 for each mobilizer. Here is an example:

        GeneralForceSubsystem forces;
        MobilizedBody::Pin    pinJoint(...);
        MobilityDiscreteForce myForce(forces, pinJoint, MobilizerUIndex(0));

SimTK::Force::MobilityDiscreteForce::MobilityDiscreteForce	(	GeneralForceSubsystem &	forces,
		const MobilizedBody &	mobod,
		Real	defaultForce = `0`
	)		`[inline]`

Alternate constructor signature for when the mobilizer has only a single generalized speed, in which case we'll use MobilizerUIndex(0).

See the other signature for documentation.

SimTK::Force::MobilityDiscreteForce::MobilityDiscreteForce ( ) [inline]

Default constructor creates an empty handle.

Member Function Documentation

MobilityDiscreteForce& SimTK::Force::MobilityDiscreteForce::setDefaultMobilityForce ( Real defaultForce )

Provide a new value for the defaultForce, overriding the one provided in the constructor.

This is a topological change because it affects the value that the containing System's default state will have when realizeTopology() is called. This is for use during construction, not for during a simulation where you should be using setGeneralizedForce().

Parameters:

defaultForce the value this generalized force should have by default

Returns:: a writable reference to this modified force element

See also:: setMobilityForce(), getDefaultMobilityForce()

Real SimTK::Force::MobilityDiscreteForce::getDefaultMobilityForce ( ) const

Return the value that this generalized force will have by default.

This is normally set in the constructor, or left to its default value of 0. It can also be set in setDefaultMobilityForce(). Note that this is not the same as the value that may be set in any particular State.

See also:: getMobilityForce(), setDefaultMobilityForce()

void SimTK::Force::MobilityDiscreteForce::setMobilityForce	(	State &	state,
		Real	f
	)		const

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

Set this to zero if you don't want it to do anything.

See also:: getMobilityForce()

Real SimTK::Force::MobilityDiscreteForce::getMobilityForce ( const State & state ) const

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

If no calls to setMobilityForce() have been made on this state then it will have the defaultForce value that was supplied on construction or via setDefaultMobilityForce().

See also:: setMobilityForce()

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

Force_MobilityDiscreteForce.h

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation