A linear spring that acts along or around a mobility coordinate to apply a generalized force there. More...

#include <Force_MobilityLinearSpring.h>

Inheritance diagram for SimTK::Force::MobilityLinearSpring:

Public Member Functions
	MobilityLinearSpring (GeneralForceSubsystem &forces, const MobilizedBody &mobod, MobilizerQIndex whichQ, Real defaultStiffness, Real defaultQZero)
	Create a MobilityLinearSpring force element on a particular generalized coordinate.
	MobilityLinearSpring ()
	Default constructor creates an empty handle that can be assigned to refer to any MobilityLinearSpring object.
MobilityLinearSpring &	setDefaultStiffness (Real defaultStiffness)
	Provide a new value for the default stiffness k of this spring.
MobilityLinearSpring &	setDefaultQZero (Real defaultQZero)
	Provide a new value for the zero position q0 of this spring, at which position the spring force will be zero.
Real	getDefaultStiffness () const
	Return the default value for the spring's stiffness k.
Real	getDefaultQZero () const
	Return the default value for the spring's zero position q0.
const MobilityLinearSpring &	setStiffness (State &state, Real stiffness) const
	Change the value of the spring stiffness in the given state; this may differ from the default value supplied at construction.
const MobilityLinearSpring &	setQZero (State &state, Real qZero) const
	Change the value of the spring zero length in the given state; this may differ from the default value supplied at construction.
Real	getStiffness (const State &state) const
	Return the value for the spring's stiffness k that is stored in the given state.
Real	getQZero (const State &state) const
	Return the value for the spring zero position q0 that is stored in the given state.
Deprecated
Methods here are for backwards compatibility but have been replaced with better ones that you should use.
	MobilityLinearSpring (GeneralForceSubsystem &forces, const MobilizedBody &mobod, int whichQ, Real defaultStiffness, Real defaultQZero)
	Deprecated: Alternate signature for backwards compatibilty -- for safety you should prefer using the other constructor signature that takes a MobilizerQIndex rather than a plain int.

Detailed Description

A linear spring that acts along or around a mobility coordinate to apply a generalized force there.

The stiffness k is provided, along with an arbitrary "zero" coordinate value q0 at which the spring generates no force. The generated force is k*(q-q0), and potential energy is pe = 1/2 k (q-q0)^2.

Constructor & Destructor Documentation

SimTK::Force::MobilityLinearSpring::MobilityLinearSpring	(	GeneralForceSubsystem &	forces,
		const MobilizedBody &	mobod,
		MobilizerQIndex	whichQ,
		Real	defaultStiffness,
		Real	defaultQZero
	)

Create a MobilityLinearSpring force element on a particular generalized coordinate.

Parameters:

[in,out]	forces	The subsystem to which this force should be added.
[in]	mobod	Mobilizer to which the force should be applied.
[in]	whichQ	To which of the mobilizer's generalized coordinates q should this force be applied (first is 0)?
[in]	defaultStiffness	The default value for the spring constant k.
[in]	defaultQZero	The default for the value of the coordinate q0 at which the force is 0.

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

Default constructor creates an empty handle that can be assigned to refer to any MobilityLinearSpring object.

SimTK::Force::MobilityLinearSpring::MobilityLinearSpring	(	GeneralForceSubsystem &	forces,
		const MobilizedBody &	mobod,
		int	whichQ,
		Real	defaultStiffness,
		Real	defaultQZero
	)		`[inline]`

Deprecated: Alternate signature for backwards compatibilty -- for safety you should prefer using the other constructor signature that takes a MobilizerQIndex rather than a plain int.

Member Function Documentation

MobilityLinearSpring& SimTK::Force::MobilityLinearSpring::setDefaultStiffness ( Real defaultStiffness )

Provide a new value for the default stiffness k of this spring.

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 setStiffness() to set the stiffness in a State rather than in the System.

Parameters:

[in] defaultStiffness The default value for the spring constant k.

Returns:: A writable reference to this modified force element for convenience in chaining set methods.

See also:: getDefaultStiffness(), setStiffness()

MobilityLinearSpring& SimTK::Force::MobilityLinearSpring::setDefaultQZero ( Real defaultQZero )

Provide a new value for the zero position q0 of this spring, at which position the spring force will be zero.

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 setQZero() to set the zero position in a State rather than in the System.

Parameters:

[in] defaultQZero The default for the value of the coordinate at which the force is 0.

Returns:: A writable reference to this modified force element for convenience in chaining set methods.

See also:: getDefaultQZero(), setQZero()

Real SimTK::Force::MobilityLinearSpring::getDefaultStiffness ( ) const

Return the default value for the spring's stiffness k.

This is normally set at construction but can be modified with setDefaultStiffness().

See also:: setDefaultStiffness(), getStiffness()

Real SimTK::Force::MobilityLinearSpring::getDefaultQZero ( ) const

Return the default value for the spring's zero position q0.

This is normally set at construction but can be modified with setDefaultQZero().

See also:: setDefaultQZero(), getQZero()

const MobilityLinearSpring& SimTK::Force::MobilityLinearSpring::setStiffness	(	State &	state,
		Real	stiffness
	)		const

Change the value of the spring stiffness in the given state; this may differ from the default value supplied at construction.

Parameters:

[in,out]	state	The State in which the stiffness is to be changed.
[in]	stiffness	The new stiffness k (>= 0) that overrides the default.

Returns:: A const reference to this MobilityLinearSpring element for convenience in chaining set methods together.

Changing the spring stiffness invalidates Stage::Dynamics and above in the state since it can affect force generation.

See also:: setDefaultStiffness(), getStiffness()

const MobilityLinearSpring& SimTK::Force::MobilityLinearSpring::setQZero	(	State &	state,
		Real	qZero
	)		const

Change the value of the spring zero length in the given state; this may differ from the default value supplied at construction.

Parameters:

[in,out]	state	The State in which the zero length is to be changed.
[in]	qZero	The value of the controlled coordinate q at which the generated spring force should be zero. This overrides the default.

Returns:: A const reference to this MobilityLinearSpring element for convenience in chaining set methods together.

Changing the spring stiffness invalidates Stage::Dynamics and above in the state since it can affect force generation.

See also:: setDefaultStiffness(), getStiffness()

Real SimTK::Force::MobilityLinearSpring::getStiffness ( const State & state ) const

Return the value for the spring's stiffness k that is stored in the given state.

Note that this is not the same thing as the default stiffness that was supplied on construction or in setDefaultStiffness().

See also:: setStiffness(), getDefaultStiffness()

Real SimTK::Force::MobilityLinearSpring::getQZero ( const State & state ) const

Return the value for the spring zero position q0 that is stored in the given state.

Note that this is not the same thing as the default q0 that was supplied on construction or in setDefaultQZero().

See also:: setQZero(), getDefaultQZero()

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

Force_MobilityLinearSpring.h

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation