This information is part of the Modelica Standard Library maintained by the Modelica Association.
The relative velocity vector between the origins of frame_a and of frame_b are determined and provided at the output signal connector v_rel. This vector is defined as:
r_rel = MultiBody.Frames.resolve2(frame_a.R, frame_b.r_0 - frame_a.r_0); v_rel = der(r_rel);
Via parameter resolveInFrame it is defined, in which frame the velocity vector is resolved:
|world||Resolve vector in world frame|
|frame_a||Resolve vector in frame_a|
|frame_b||Resolve vector in frame_b|
|frame_resolve||Resolve vector in frame_resolve|
If resolveInFrame = Types.ResolveInFrameAB.frame_resolve, the conditional connector "frame_resolve" is enabled and v_rel is resolved in the frame, to which frame_resolve is connected. Note, if this connector is enabled, it must be connected.
If resolveInFrame = Types.ResolveInFrameAB.frame_b, the output vector is computed as:
r_rel = MultiBody.Frames.resolve2(frame_a.R, frame_b.r_0 - frame_a.r_0); v_rel_a = der(r_rel); v_rel = MultiBody.Frames.resolveRelative(frame_a.R, frame_b.R, v_rel_a);
Description: Frame in which output vector v_rel shall be resolved (world, frame_a, frame_b, or frame_resolve)
Description: Coordinate system a
Description: Coordinate system b
Description: Relative velocity vector resolved in frame defined by resolveInFrame
Description: Coordinate system in which v_rel is optionally resolved