Modeling and simulation of a valve system actuated by polycrystalline shape memory alloy wires

Abstract

In this paper we present a control-oriented model for an actuator system driven by a shape memory alloy (SMA) wire. SMAs appear as suitable for the realization of compact actuator solutions, due to the inherently high energy density of the material. However, the strongly hysteretic response of SMAs significantly complicates modeling and control of devices based on such technology. The main goal of this paper is the development of a control-oriented model of a SMA wire valve actuator. The overall system model highly relies on an accurate model of the SMA material itself, which permits to describe the temperature-dependent hysteresis in a physics-based fashion. In addition, the model explicitly accounts for the polycrystalline nature of the material, and permits to reproduce the SMA hysteresis with high accuracy and in a computationally efficient way. Development of model equations is presented first. Subsequently, experimental identification and validation are performed on a 76 micron SMA wire. Model ability of predicting both stress-strain and resistance-strain curves, measured at different input powers, is shown. Finally, preliminary results on simulation of the overall actuator are presented.