A highly integrated shape memory alloy actuator and precision self-sensing tracking control based on position compensation

Shape memory alloy (SMA) actuators are widely used in various actuators due to their advantages of simplicity, high strength, and flexibility. The mapping relationship between the resistance change and displacement during the phase transition process of SMA enables its self-sensing control without external displacement sensors. However, the limited accuracy and high complexity of existing self-sensing models are two crucial factors restricting the wide application of self-sensing control. Due to the high nonlinearity of the SMA wire's phase transition process, it is challenging to achieve accurate position estimation using a simple self-sensing model. Thus, this paper proposes a novel approach by utilizing the simplest linear model for position estimation. The inevitable modeling errors are directly compensated in the final control results, rather than compensating for estimation errors. This significantly reduces the implementation difficulty of SMA self-sensing control and effectively improves control accuracy. Furthermore, a highly integrated prototype of SMA actuator is designed in this paper, where the additional position sensor and self-resetting loading device are integrated, greatly reducing the size of the SMA actuator. A series of self-sensing tracking experiments are conducted on this prototype, validating that the compensated self-sensing control can achieve comparable performance to the control method with external sensors.