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Drake
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Drake
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FrameBase is an abstract representation of the concept of a frame in multibody dynamics.
A frame F is a mathematical object consisting of a set of three orthogonal unit vector axes Fx,Fy,Fz forming a right-handed orthogonal basis located at a point Fo called the frame's origin. If the frame origin Fo is a material point of a body, then F is a material frame (also called a physical frame) and can be used to apply forces and torques to its body. A material frame can serve as an attachment point for force-producing elements such as joints and constraints. Otherwise, we call the frame a free-floating or computed frame and it is still suited for observation, visualization, and measurement but cannot be used to apply forces. Because material frames are by far the most common and useful frames encountered in multibody systems, the derived class with the simple name Frame is used to represent them.
Given numerical values in a Context for the associated multibody system, every frame has a location and orientation (collectively, pose) in space that can be obtained through this base class. Most frames will also move based on the multibody system's configuration, or on general runtime computations, so may have meaningful spatial velocity and acceleration – that will always be the case for material frames during a dynamic simulation. Such kinematic quantities must always be measured with respect to some other specified frame. The only frame we can be sure exists is the World frame W, so pose and motion with respect to W are always available. Utilities are provided for calculating frame motion with respect to other frames. Derived frame objects will have additional properties. For example, material frames have an associated Body.
Summarizing, FrameBase serves as an abstraction for a general frame object; it doesn't store any values itself. As always in Drake, runtime values are obtained from a Context object. FrameBase provides an interface through which the pose of a frame may be obtained from a given Context. Classes derived from FrameBase are used to represent more specific types of frames, most importantly whether a frame is associated with a material point of a body.
| T | The scalar type, which must be one of the default scalars. |
#include <drake/multibody/tree/frame_base.h>
Public Member Functions | |
| FrameIndex | index () const |
| Returns this element's unique index. More... | |
 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 |
Protected Member Functions | |
| FrameBase (ModelInstanceIndex model_instance) | |
| 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... | |
| virtual void | DoSetTopology (const internal::MultibodyTreeTopology &tree)=0 |
| Implementation of the NVI SetTopology(). More... | |
| virtual void | DoDeclareParameters (internal::MultibodyTreeSystem< T > *) |
| Implementation of the NVI DeclareParameters(). More... | |
| virtual void | DoSetDefaultParameters (systems::Parameters< T > *) const |
| Implementation of the NVI SetDefaultParameters(). 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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explicitprotected |
| FrameIndex index | ( | ) | const |
Returns this element's unique index.