Actuator with non-linear elastic system and its application to 3 DOF wrist joint

This paper deals with mechanical stiffness control of multi-DOF joint. It fundamentally mimics skeleton-muscular system of human articulation, in which at least two muscles cooperatively handle one DOF under their antagonistic action. In the first part of the paper one describes a novel actuator called ANLES (actuator with non-linear elastic system) that mimics a skeletal muscle in the sense of having a non-linear elasticity. Next one introduces a basic formula for controlling stiffness of the joint as well as its angles using multiple ANLES. It follows the evaluation of the proposed formula by the simulation analysis. Three DOF joint manipulated by four tendons that are individually controlled by the ANLES is evaluated with respect to the stiffness control.