Position Control of Shape Memory Alloy Actuator Using Hysteresis Model

The tracking control accuracy of shape memory alloy (SMA) actuator is limited due to inherent hysteresis nonlinearity. It has been said that a push-pull type mechanism and the insertion of a resistance feedback loop are useful to effects of the hysteresis. This paper presents a position control system for compensating the hysteresis without such constraints. It is composed of feedforward loop and PID feedback loop. In the feedforward loop, the desired input corresponding to the desired displacement is obtained from a model of hysteresis. The proposed control system is applied to a bias spring type SMA actuator that is more difficult to be controlled accurately than a push-pull type one. Experimental results show that tracking control performance is greatly improved.