Position control of SMA actuators with internal electrical resistance feedback

Ibis paper presents the development of a position control system for a shape memory alloy (SMA) wire actuator using the electrical resistance feedback. It is commonly known that an SMA actuator is highly nonlinear and a position sensor is often required to achieve a stable and accurate positioning. And this position sensor often contributes a large portion of the system cost. To eliminate the position sensor in an MA actuator system, a novel control theme is proposed by utilizing the actuator's electrical resistance feedback. With an SMA wire test setup, the relationship between the electrical resistance and the displacement is experimentally investigated. However, this relationship is highly nonlinear, and a neural network is employed to model this relationship and predicts the position of the actuator using only its electrical resistance information. To enable feedback control of the SMA wire actuator using only its electrical resistance, a Proportional-Integral-derivative (PID) controller is used. Feedback control experiments are performed and the results demonstrate that the proposed position control system achieves a good control performance without using a position sensor.