I want to implement a manipulator link using a physic library. I can only apply some torque to the centre of mass, but the torque should be applied at the beginning of the link.

Shifting a reference frame from the centre of mass and recalculating inertia tensor in the new frame is not a problem, neither is recalculating a new torque, based on the change of distance, but I think it is not the correct solution.

In short, how can I scale a torque of a control signal applied at the beginning of the link to a torque of a physic simulation applied to the centre of mass. Thanks.