CompositeInertia
2D/3D• CompositeInertia[{centroid1, mass1, inertia1}, ... , {centroidn, massn, inertian}] returns the list {centroid, mass, inertia} of the inertia properties of a composite body B made up of the n specified subcomponents.
• In Modeler3D, arguments to CompositeInertia can have the form {centroidn, massn, inertian, rotationn} to specify subcomponents that are rotated relative to the composite body B. • Given a local reference frame XYZ_B affixed to the composite body B, each argument to CompositeInertia specifies the inertia properties of a subcomponent of B, in the XYZ_B reference frame.
• Each centroidi is specified by {x, y} or {x, y, z} and each massi by a scalar.
• In Modeler2D each inertiai is specified by a scalar, while in Modeler3D each inertiai is given as a list of the elements of the inertia matrix, {Ixx, Iyy, Izz, Ixy, Iyz, Izx} or a full inertia matrix.
• All given inertia properties are assumed to be centroidal.
• If the inertia properties of a 3D subcomponent are known in a non-XYZ_B reference frame xyz_B, the rotationi argument is used to specify the rotation of the xyz_B reference frame, relative to XYZ_B. The rotationi are specified by {angle, axis}, a virtual rotation vector, or a set of Euler parameters.
• If any of the subcomponents are voids, their mass and inertia properties must be negated so that the inertia of the subcomponent is subtracted from the composite body.
• See also: ParallelAxis, PrincipalAxes. Further Examples Load the Modeler3D package. Here are inertia properties transformed from a noncentroidal to centroidal reference frame.
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Here are the principal axes of the resulting inertia properties.
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This rotates the original inertia matrix into the principal frame.
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Here is the result of combining two sets of inertia properties.
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