In recent years, the Preisach hysteresis model (1935) has emerged as the model of choice for the behaviour of many smart materials, such as shape memory alloys (SMA). This research treats the identification of Preisach models for a differential SMA actuator. The traditional identification technique is applied, and several models are derived for the actuator. It is seen that the classical Preisach model is able to model its behaviour. However, the results raise questions concerning the robustness of the traditional identification technique, as well as the conservative nature of current passivity-based control results for the Preisach model.

The motivation for this research arises from interest in actuators made from "smart materials" such as shape memory alloys and piezoceramics. One common characteristic among these new materials is that they exhibit complex hysteresis nonlinearities. The input-output nature of the Preisach model of hysteresis results in a simple model for which identification strategies are known, and implementation is straightforward both in simulation and real-time control. This paper examines the passivity of the Preisach model, and the stability of velocity feedback control for hysteretic actuators.