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:

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.

Example

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);