Fault-tolerant control of a rotary shape memory alloy actuator using a terminal sliding mode controller

Abstract

This paper focuses on developing a Fault-tolerant control (FTC) method for a rotary Shape Memory Alloy (SMA) actuator against actuator faults. The SMA actuator uses a pair of SMA wires in the antagonistic configuration for rotating a pulley. A proposed Terminal Sliding Mode Controller (TSMC) is utilized to compensate for the effects of actuator faults and to guarantee acceptable tracking performance in the presence of faults. The developed closed-loop scheme is applied to both a simulated model of the actuator as well as a real actuator in an experimental setup and then, the performance is evaluated and compared with a Proportional (P) controller and a sliding mode controller. It is shown that the proposed scheme works well in both normal and faulty conditions. The experimental results indicate that TSMC has almost no steady-state error while both P and sliding mode controllers have a considerable error (about 20% relative error), in the presence of the actuator faults.