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Drake
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Drake
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This ForceElement models a linear spring attached to a PrismaticJoint and applies a force to that joint according to.
f = -k⋅(x - x₀)
where x₀ is the nominal (zero spring force) position in meters, x is the joint position in meters, f is the spring force in Newtons and k is the spring constant in N/m. Note that joint damping exists within the PrismaticJoint itself, and so is not included here.
| T | The scalar type, which must be one of the default scalars. |
#include <drake/multibody/tree/prismatic_spring.h>
Public Member Functions | |
| PrismaticSpring (const PrismaticJoint< T > &joint, double nominal_position, double stiffness) | |
| Constructor for a linear spring attached to the given prismatic joint. More... | |
| const PrismaticJoint< T > & | joint () const |
| double | nominal_position () const |
| double | stiffness () const |
| T | 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... | |
| T | 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... | |
| T | 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 | |
| PrismaticSpring (const PrismaticSpring &)=delete | |
| PrismaticSpring & | operator= (const PrismaticSpring &)=delete |
| PrismaticSpring (PrismaticSpring &&)=delete | |
| PrismaticSpring & | operator= (PrismaticSpring &&)=delete |
 Public Member Functions inherited from ForceElement< T > | |
| ForceElement (ModelInstanceIndex model_instance) | |
| Default constructor for a generic force element. More... | |
| 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 | |
| ForceElement & | operator= (const ForceElement &)=delete |
| ForceElement (ForceElement &&)=delete | |
| ForceElement & | operator= (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 | |
| MultibodyElement & | operator= (const MultibodyElement &)=delete |
| MultibodyElement (MultibodyElement &&)=delete | |
| MultibodyElement & | operator= (MultibodyElement &&)=delete |
Friends | |
| template<typename U > | |
| class | PrismaticSpring |
Additional Inherited Members | |
| 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... | |
| 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... | |
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| PrismaticSpring | ( | const PrismaticJoint< T > & | joint, |
| double | nominal_position, | ||
| double | stiffness | ||
| ) |
Constructor for a linear spring attached to the given prismatic joint.
| [in] | nominal_position | The nominal position of the spring x₀, in meters, at which the spring applies no force. This is measured the same way as the generalized position of the prismatic joint. |
| [in] | stiffness | The stiffness k of the spring in N/m. |
| std::exception | if stiffness is (strictly) negative. |
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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.
Implements ForceElement< T >.
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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.
Implements ForceElement< T >.
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overridevirtual |
(Advanced) Calculates the potential energy currently stored given the configuration provided in context.
Non-conservative force elements will return zero.
| [in] | context | The context containing the state of the MultibodyTree model. |
| [in] | pc | A position kinematics cache object already updated to be in sync with context. |
pc must have been previously updated with a call to CalcPositionKinematicsCache().this force element. For non-conservative force models, zero.Implements ForceElement< T >.
| const PrismaticJoint<T>& joint | ( | ) | const |
| double nominal_position | ( | ) | const |
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| double stiffness | ( | ) | const |
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