Control of robot arm with elastic joints via nonlinear dynamic feedback

It is known that control of a rigid robot arm can easily be achieved via static state-feedback compensation of the nonlinearities. However, in many practical situations, the elasticity in gear boxes is not negligible. If this is the case, the use of such a control technique is not possible anymore because neither is the system feedback equivalent to a controllable linear one, nor its input-output behavior can be decoupled via static state-feedback. The purpose of this paper is to show how dynamic state-feedback compensation may be used in order to obtain full state-space iinearity, and to present an application to the model of a three link robot arm with elastic joints.