OPTIMAL CONTROL OF TENDON-SHEATH TRANSMISSION SYSTEMS

In this paper, the tendon-sheath driving system for a robotic hand is discussed and its force transmission characteristic analyzed. The use of tendons permits to reduce the size and the complexity of the actuation chain in many mechanical devices but, on the other hand, introduces some side effects that must be taken into account in the design of the controller of the transmission system. A simple dynamical model, useful for both analysis and control design purposes, that describes the tendon-sheath driving system is presented and discussed. Then, its main properties are illustrated, and a comparison with both simulation results of a lumped parameters model of the tendon and with experimental results is presented. The described model is non linear because of the effects of friction between the tendon and the sheath. Finally, a suitable optimal controller is designed to reduce the effects of the friction.