Modelling and Temperature Control of Shape Memory Alloys with Fast Electrical Heating

This paper presents a comparative theoretical study of the performance of a set of controllers for improving the speed of actuators based on shape memory alloys (SMAs), especially on Nitinol (NiTi). To prevent overheating and thermal fatigue, these controllers take into account the maximum heating current at which a NiTi element can safely be heated. The thermal behaviour of NiTi is first modelled for calculating the time response and, based on the suggested model, it is shown that hysteresis due to phase transformation can be neglected for rapid heating, thus simplifying the model to a linear problem. The design and performance of a set of linear controllers is then presented. Simulation results show a substantial increase in actuation speed.