• InstantCenter[bnum] returns the coordinates of the instant center of zero velocity of body bnum.
• InstantCenter accepts the Coordinates option to determine whether to return the result in Global or body Local coordinates.
• In Modeler3D, InstantCenter returns a point on the instant axis of rotation.
• The default option setting is Coordinates->Global.
• In general, a spatial body will not have an instant center of zero velocity, but it will have an instant axis of rotation. The direction vector of the instant axis of rotation is equal to the angular velocity vector of the body, Omega[bnum]. All points on this axis will have identical velocity vectors.
• See also: Omega, RelativeVelocity, Velocity.
Load the Modeler3D package and define a simple model.
Here is a point on the instant axis of rotation on the link body.
Therefore, here is the entire instant axis of rotation in global coordinates.
Here is a point on the instant axis of rotation expressed in the local coordinate system of the link.