Modeling and Hysteresis Compensation in a Thin SMA Wire Using ANFIS Methods

Having a responsive behavior to applied voltage/current, shape memory alloy (SMA) wires are widely used as miniature, low mass, compact actuators for many applications. Due to the non-linear hysteretic behavior, SMA wires require advanced control techniques for precision control when used as actuators. In this article, an adaptive neuro-fuzzy inference system (ANFIS) is developed to compensate for the hysteretic non-linearity in a thin SMA wire. An experimental setup is designed to test the SMA wire, which can achieve an operating bandwidth of 1 Hz without an external cooling system. By using the data obtained from the experimental system, an ANFIS model is developed to model the major and minor hysteresis loops (voltage vs. displacement characteristics) and the hysteresis non-linearity at various driving frequencies. Results of numerical simulations based on the ANFIS model closely match the experimental data. Having demonstrated the ability of the ANFIS to account for the hysteretic behavior, an inverse ANFIS controller is devised to compensate for the hysteretic behavior. Finally a PI control action is included in the feedback loop to fine-tune the system response in real time.