Dynamic modelling of SmartFlex® SMA wires

Abstract:
Shape Memory Alloy (SMA) actuators are increasingly finding their way into many application fields like automotive, medical devices, household appliances or smartphones. However, the behavior of SMA material is non-linear and displays a pronounced hysteresis. In order to optimize the performance of SMA actuators already during design, mathematical models capturing the complex behavior with a high degree of accuracy are needed. Such models also provide the basis for advanced model-based control schemes. This paper proposes a new hysteresis model for SMA actuators that is able to capture the rounded and asymmetric hysteresis shape found e.g. in the widely used SmartFlex(r) material. The hysteresis model is calibrated using resistance data gathered in a test setup. The experimental validation of the model investigates the prediction of actuator displacement as well as of electrical resistance.