Design of high D.O.F. mobile micro robot using electrical resistance control of shape memory alloy

Abstract

Shape-memory alloy(SMA) is a suitable actuator for a micro mobile robot due to its size and weight. However, length of SMA actuators is known to be nonlinear and hysteretic. We can control SMA’s shape analogously to its electrical resistance. This paper presents a platform to construct high degree of freedom robots with tendons of SMA actuators. We incorporate coil shape SMA as variable length tendons of tendon-driven robots. By controlling electrical resistance of SMA tendons, we can control posture of the robot structure in model-based method. A method to resolve electrical resistance for control from given posture of a high degree of freedom robot by using model of SMA and the robot is proposed. A small electrical system for high D.O.F. robots is also developed. As an application of our system, we show a four-legged robot with 16 D.O.F. joints and 24 SMA tendons.