rigid_bodies
Rigid Bodies
@ref chrono::ChBody "ChBody" is the base class for all the rigid bodies in Chrono and, as such, it carries a mass and a rotational inertia and has the capability to move in the 3D space.
Its location and rotation, as well as their derivatives, always refer to the Center of Mass (COM) while visual and collision shapes, on the contrary, are attached to a secondary reference frame (Ref).
Please mind that in @ref chrono::ChBody "ChBody" base class the COM and Ref always coincide, while only in @ref chrono::ChBodyAuxRef "ChBodyAuxRef" and derived classes the Ref frame might be placed elsewhere.
Methods like @ref chrono::ChBody::GetPos() "GetPos()" / @ref chrono::ChBody::SetPos() "SetPos()", @ref chrono::ChBody::GetRot() "GetRot()" / @ref chrono::ChBody::SetRot() "SetRot()" and their derivatives always refer to COM frame.
The auxiliary frame is handled through dedicated methods of the kind [Get|Set]FrameRefTo____ | [Get|Set]Frame____ToRef wherever it makes sense.
Rigid bodies can also:
be involved in collisions, if a collision model is provided (see [collisions](@ref collisions)) and the collision is enabled on the body;
be visualized, if a visual model is provided and a proper visualization system is available (see [visualization](@ref visualization_system));
be constrained by means of ChLink objects (see [links](@ref links));
be loaded by ChLoad objects (see [loads](@ref loads));
be used in coordinate transformation, being themselves inherited from ChFrameMoving;
@ref chrono::ChBody "ChBody" and @ref chrono::ChBodyAuxRef "ChBodyAuxRef" bodies do not come with any visual or collision model, thus requiring the user to specify them as well as providing valid mass and inertia parameters.
However, in the case the rigid body could be described through a primitive shape, a set classes of the type ChBodyEasy can simplify this task, by calculating mass, inertia and by optionally creating a visual and collision shape:
@ref chrono::ChBodyEasySphere "ChBodyEasySphere"
@ref chrono::ChBodyEasyCylinder "ChBodyEasyCylinder"
@ref chrono::ChBodyEasyBox "ChBodyEasyBox"
@ref chrono::ChBodyEasyConvexHull "ChBodyEasyConvexHull"
@ref chrono::ChBodyEasyClusterOfSpheres "ChBodyEasyClusterOfSpheres"
Rigid bodies are not the only option. Chrono can simulate also flexible finite-elements bodies. Please refer to [FEA manual](@ref manual_fea) for a description of the FEA capabilities.
Usage
Creating/Setting up a ChBody object typically involves the following steps:
Create the rigid body;
auto mybody = chrono_types::make_shared<ChBody>(); mybody->SetMass(10); mybody->SetInertiaXX( ChVector3d(4,4,4) ); mybody->SetPos( ChVector3d(0.2,0.4,2) ); mybody->SetPosDt( ChVector3d(0.1,0,0) ); my_system.Add(mybody);Optional: add [visual shapes](@ref visualization_system)
auto visshape = chrono_types::make_shared<ChVisualShapeBox>(20, 1, 20); visshape->SetColor(ChColor(0.2f, 0.3f, 1.0f)); mybody->AddVisualShape(visshape, ChFramed(ChVector3d(0, -1, 0), QUNIT));Optional: add [collision shapes and material](@ref collisions)
auto collmat = chrono_types::make_shared<ChContactMaterialNSC>(); auto collshape = chrono_types::make_shared<ChCollisionShapeBox>(collmat, 0.1, 0.2, 0.3); mybody->AddCollisionShape(collshape); mybody->EnableCollision(true);
Please refer to the dedicate pages for [collision](@ref collisions) and [visualization](@ref visualization_system) to complete the configuration of the system.
For bodies of the class ChBodyEasy the constructor is richer:
auto mySphere = chrono_types::make_shared<ChBodyEasySphere>(4, // radius
8000, // density
true, // visualization enabled
true, // collision enabled
collmat // collision material
);
my_system.Add(mySphere);Demos
See:
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