Robust position regulation of a rotary servo actuated by a shape memory alloy wire

This paper presents the design and experiment results of robust control of a rotary servo actuated by an SMA wire. A rotary servo device using NiTi type of SMA wire have been designed and fabricated for this research. This rotary servo is equipped with an RVIT sensor for angular position measurements. To actively control the servo, a sliding-mode based robust control approach is used. The sliding-mode based robust control consists of three components: a standard proportional plus derivative (PD) control term, a feed forward term used as a bias current, and a robust term to increase the system's stability and control accuracy. The control strategy is implemented using a dSPACE real-time control system. Experimental results show that the rotary servo can be precisely controlled using the sliding-mode based robust control approach.