Dynamic high-gain observer approach with sliding mode control for an arc-shaped shape memory alloy compliant actuator

In this research, we present a dynamic high gain observer (HGO) combined with a sliding mode controller (SMC) for a novel shape memory alloy (SMA) actuator. The dynamic model of the SMA actuator contains nonlinearities with hysteresis, which makes the estimation of velocity and acceleration of the actuator challenging. We first design a dynamic HGO to estimate velocity and acceleration of the SMA actuator by considering nonlinearities with hysteresis in the dynamics. We then develop a SMC for the actuator using the estimated velocity and acceleration. The proposed SMC in conjunction with the dynamic HGO is tested experimentally for the actuator. For comparison, trajectory tracking experiments are also conducted by using PID without an observer, SMC without an observer, and SMC with a non-dynamic HGO. Our results confirm that the dynamic HGO combined with SMC can enhance trajectory tracking accuracy while reducing the chattering phenomenon.