Sensorless resistive-based control of shape memory alloy actuators in locking mechanism

This article presents a sensorless resistive-based control method to control shape memory alloy wire actuators to be used in the development of a laparoscopic surgical locking system. Shape memory alloy wire electrical resistance is measured to control the martensite phase fraction of shape memory alloy wire. The martensite phase fraction is calculated based on mathematical heating model, resistance models, and the measured resistance. Experiments are conducted to evaluate the validity and performance of the method in the control of the locking system angle. The results show that the sensorless resistive-based control method accurately controls the wire without using any position sensors, resulting in the lower cost, size, and weight of the system. The results show very small steady-state errors, verifying the practicability of this method. The sensorless resistive-based control method has the potential to be used in many applications in which cost and space are limited and the use of an external sensor is impossible or costly.