Design of a robust control strategy for the heating power of shape memory alloy actuators at full contraction based on electric resistance feedback

The application of shape memory alloys (SMA) for actuators is still limited to a couple of particular prototypes, and only a few commercial actuators are available. One of the main reasons is the lack in robustness regarding substantial fatigue and changes in boundary conditions. In order to improve the life time behavior and reduce the fatigue of SMA actuators, a self-sensing control strategy is presented. Based on resistance feedback, the heating power at full contraction is controlled in order to avoid overheating without reducing the operating voltage. This allows fast actuation without thermal overload of the SMA. The concept was proved experimentally. Life time tests show a considerable increase in life cycles and reduce of fatigue.