Drake
Drake C++ Documentation
RevoluteSpring< T > Class Template Referencefinal

Detailed Description

template<typename T>
class drake::multibody::RevoluteSpring< T >

This ForceElement models a torsional spring attached to a RevoluteJoint and applies a torque to that joint.

  τ = -k⋅(θ - θ₀)

where θ₀ is the nominal joint position. Note that joint damping exists within the RevoluteJoint itself, and so is not included here.

Template Parameters
TThe scalar type, which must be one of the default scalars.

#include <drake/multibody/tree/revolute_spring.h>

Public Member Functions

 RevoluteSpring (const RevoluteJoint< T > &joint, double nominal_angle, double stiffness)
 Constructor for a spring attached to the given joint. More...
 
 ~RevoluteSpring () override
 
const RevoluteJoint< T > & joint () const
 
double nominal_angle () const
 
double stiffness () const
 
CalcPotentialEnergy (const systems::Context< T > &context, const internal::PositionKinematicsCache< T > &pc) const override
 (Advanced) Calculates the potential energy currently stored given the configuration provided in context. More...
 
CalcConservativePower (const systems::Context< T > &context, const internal::PositionKinematicsCache< T > &pc, const internal::VelocityKinematicsCache< T > &vc) const override
 (Advanced) Calculates and returns the power generated by conservative force elements or zero if this force element is non-conservative. More...
 
CalcNonConservativePower (const systems::Context< T > &context, const internal::PositionKinematicsCache< T > &pc, const internal::VelocityKinematicsCache< T > &vc) const override
 (Advanced) Calculates the rate at which mechanical energy is being generated (positive) or dissipated (negative) other than by conversion between potential and kinetic energy. More...
 
Does not allow copy, move, or assignment
 RevoluteSpring (const RevoluteSpring &)=delete
 
RevoluteSpringoperator= (const RevoluteSpring &)=delete
 
 RevoluteSpring (RevoluteSpring &&)=delete
 
RevoluteSpringoperator= (RevoluteSpring &&)=delete
 
- Public Member Functions inherited from ForceElement< T >
 ForceElement (ModelInstanceIndex model_instance)
 Default constructor for a generic force element. More...
 
 ~ForceElement () override
 
ForceElementIndex index () const
 Returns this element's unique index. More...
 
void CalcAndAddForceContribution (const systems::Context< T > &context, const internal::PositionKinematicsCache< T > &pc, const internal::VelocityKinematicsCache< T > &vc, MultibodyForces< T > *forces) const
 (Advanced) Computes the force contribution for this force element and adds it to the output arrays of forces. More...
 
 ForceElement (const ForceElement &)=delete
 
ForceElementoperator= (const ForceElement &)=delete
 
 ForceElement (ForceElement &&)=delete
 
ForceElementoperator= (ForceElement &&)=delete
 
- Public Member Functions inherited from MultibodyElement< T >
virtual ~MultibodyElement ()
 
ModelInstanceIndex model_instance () const
 Returns the ModelInstanceIndex of the model instance to which this element belongs. More...
 
template<typename MultibodyPlantDeferred = MultibodyPlant<T>>
const MultibodyPlantDeferred & GetParentPlant () const
 Returns the MultibodyPlant that owns this MultibodyElement. More...
 
void DeclareParameters (internal::MultibodyTreeSystem< T > *tree_system)
 Declares MultibodyTreeSystem Parameters at MultibodyTreeSystem::Finalize() time. More...
 
void SetDefaultParameters (systems::Parameters< T > *parameters) const
 Sets default values of parameters belonging to each MultibodyElement in parameters at a call to MultibodyTreeSystem::SetDefaultParameters(). More...
 
 MultibodyElement (const MultibodyElement &)=delete
 
MultibodyElementoperator= (const MultibodyElement &)=delete
 
 MultibodyElement (MultibodyElement &&)=delete
 
MultibodyElementoperator= (MultibodyElement &&)=delete
 

Protected Member Functions

void DoCalcAndAddForceContribution (const systems::Context< T > &context, const internal::PositionKinematicsCache< T > &pc, const internal::VelocityKinematicsCache< T > &vc, MultibodyForces< T > *forces) const override
 This method is called only from the public non-virtual CalcAndAddForceContributions() which will already have error-checked the parameters so you don't have to. More...
 
std::unique_ptr< ForceElement< double > > DoCloneToScalar (const internal::MultibodyTree< double > &tree_clone) const override
 Clones this ForceElement (templated on T) to a mobilizer templated on double. More...
 
std::unique_ptr< ForceElement< AutoDiffXd > > DoCloneToScalar (const internal::MultibodyTree< AutoDiffXd > &tree_clone) const override
 Clones this ForceElement (templated on T) to a mobilizer templated on AutoDiffXd. More...
 
std::unique_ptr< ForceElement< symbolic::Expression > > DoCloneToScalar (const internal::MultibodyTree< symbolic::Expression > &) const override
 
- Protected Member Functions inherited from ForceElement< T >
virtual void DoDeclareForceElementParameters (internal::MultibodyTreeSystem< T > *)
 Called by DoDeclareParameters(). More...
 
virtual void DoSetDefaultForceElementParameters (systems::Parameters< T > *) const
 Called by DoSetDefaultParameters(). More...
 
- Protected Member Functions inherited from MultibodyElement< T >
 MultibodyElement ()
 Default constructor made protected so that sub-classes can still declare their default constructors if they need to. More...
 
 MultibodyElement (ModelInstanceIndex model_instance)
 Constructor which allows specifying a model instance. More...
 
 MultibodyElement (ModelInstanceIndex model_instance, int64_t index)
 Both the model instance and element index are specified. More...
 
template<typename ElementIndexType >
ElementIndexType index_impl () const
 Returns this element's unique index. More...
 
int ordinal_impl () const
 Returns this element's unique ordinal. More...
 
const internal::MultibodyTree< T > & get_parent_tree () const
 Returns a constant reference to the parent MultibodyTree that owns this element. More...
 
const internal::MultibodyTreeSystem< T > & GetParentTreeSystem () const
 Returns a constant reference to the parent MultibodyTreeSystem that owns the parent MultibodyTree that owns this element. More...
 
void SetTopology (const internal::MultibodyTreeTopology &tree)
 Gives MultibodyElement-derived objects the opportunity to retrieve their topology after MultibodyTree::Finalize() is invoked. More...
 
systems::NumericParameterIndex DeclareNumericParameter (internal::MultibodyTreeSystem< T > *tree_system, const systems::BasicVector< T > &model_vector)
 To be used by MultibodyElement-derived objects when declaring parameters in their implementation of DoDeclareParameters(). More...
 
systems::AbstractParameterIndex DeclareAbstractParameter (internal::MultibodyTreeSystem< T > *tree_system, const AbstractValue &model_value)
 To be used by MultibodyElement-derived objects when declaring parameters in their implementation of DoDeclareParameters(). More...
 

Friends

template<typename U >
class RevoluteSpring
 

Constructor & Destructor Documentation

◆ RevoluteSpring() [1/3]

RevoluteSpring ( const RevoluteSpring< T > &  )
delete

◆ RevoluteSpring() [2/3]

RevoluteSpring ( RevoluteSpring< T > &&  )
delete

◆ RevoluteSpring() [3/3]

RevoluteSpring ( const RevoluteJoint< T > &  joint,
double  nominal_angle,
double  stiffness 
)

Constructor for a spring attached to the given joint.

Parameters
[in]nominal_angleThe nominal angle of the spring θ₀, in radians, at which the spring applies no moment.
[in]stiffnessThe stiffness k of the spring in N⋅m/rad.
Exceptions
std::exceptionif stiffness is negative.

◆ ~RevoluteSpring()

~RevoluteSpring ( )
override

Member Function Documentation

◆ CalcConservativePower()

T CalcConservativePower ( const systems::Context< T > &  context,
const internal::PositionKinematicsCache< T > &  pc,
const internal::VelocityKinematicsCache< T > &  vc 
) const
overridevirtual

(Advanced) Calculates and returns the power generated by conservative force elements or zero if this force element is non-conservative.

This quantity is defined to be positive when the potential energy is decreasing. In other words, if PE is the potential energy as defined by CalcPotentialEnergy(), then the conservative power, Pc, is Pc = -d(PE)/dt.

See also
CalcPotentialEnergy(), CalcNonConservativePower()

Implements ForceElement< T >.

◆ CalcNonConservativePower()

T CalcNonConservativePower ( const systems::Context< T > &  context,
const internal::PositionKinematicsCache< T > &  pc,
const internal::VelocityKinematicsCache< T > &  vc 
) const
overridevirtual

(Advanced) Calculates the rate at which mechanical energy is being generated (positive) or dissipated (negative) other than by conversion between potential and kinetic energy.

Integrating this quantity yields work W, and the total energy E = PE + KE - W should be conserved by any physically-correct model, to within integration accuracy of W.

See also
CalcConservativePower()

Implements ForceElement< T >.

◆ CalcPotentialEnergy()

T CalcPotentialEnergy ( const systems::Context< T > &  context,
const internal::PositionKinematicsCache< T > &  pc 
) const
overridevirtual

(Advanced) Calculates the potential energy currently stored given the configuration provided in context.

Non-conservative force elements will return zero.

Parameters
[in]contextThe context containing the state of the MultibodyTree model.
[in]pcA position kinematics cache object already updated to be in sync with context.
Precondition
The position kinematics pc must have been previously updated with a call to CalcPositionKinematicsCache().
Returns
For conservative force models, the potential energy stored by this force element. For non-conservative force models, zero.
See also
CalcConservativePower()

Implements ForceElement< T >.

◆ DoCalcAndAddForceContribution()

void DoCalcAndAddForceContribution ( const systems::Context< T > &  context,
const internal::PositionKinematicsCache< T > &  pc,
const internal::VelocityKinematicsCache< T > &  vc,
MultibodyForces< T > *  forces 
) const
overrideprotectedvirtual

This method is called only from the public non-virtual CalcAndAddForceContributions() which will already have error-checked the parameters so you don't have to.

Refer to the documentation for CalcAndAddForceContribution() for details describing the purpose and parameters of this method. It assumes forces to be a valid pointer to a MultibodyForces object compatible with the MultibodyTree model owning this force element.

Precondition
The position kinematics pc must have been previously updated with a call to CalcPositionKinematicsCache().
The velocity kinematics vc must have been previously updated with a call to CalcVelocityKinematicsCache().

Implements ForceElement< T >.

◆ DoCloneToScalar() [1/3]

std::unique_ptr<ForceElement<double> > DoCloneToScalar ( const internal::MultibodyTree< double > &  tree_clone) const
overrideprotectedvirtual

Clones this ForceElement (templated on T) to a mobilizer templated on double.

Implements ForceElement< T >.

◆ DoCloneToScalar() [2/3]

std::unique_ptr<ForceElement<AutoDiffXd> > DoCloneToScalar ( const internal::MultibodyTree< AutoDiffXd > &  tree_clone) const
overrideprotectedvirtual

Clones this ForceElement (templated on T) to a mobilizer templated on AutoDiffXd.

Implements ForceElement< T >.

◆ DoCloneToScalar() [3/3]

std::unique_ptr<ForceElement<symbolic::Expression> > DoCloneToScalar ( const internal::MultibodyTree< symbolic::Expression > &  ) const
overrideprotectedvirtual

Implements ForceElement< T >.

◆ joint()

const RevoluteJoint<T>& joint ( ) const

◆ nominal_angle()

double nominal_angle ( ) const

◆ operator=() [1/2]

RevoluteSpring& operator= ( const RevoluteSpring< T > &  )
delete

◆ operator=() [2/2]

RevoluteSpring& operator= ( RevoluteSpring< T > &&  )
delete

◆ stiffness()

double stiffness ( ) const

Friends And Related Function Documentation

◆ RevoluteSpring

friend class RevoluteSpring
friend

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