Design of a variable stiffness actuator using shape memory alloy wire

A linear (translational) actuator using synergistically configured shape memory alloy (SMA) actuator wires is designed to work by the principle of variable stiffness actuation. Synergistic SMA actuators use aiding force to create repetitive motion and are thereby capable of producing increased displacement when compared to the antagonistically biased SMA systems. The stiffness variant in the SMA actuator wires and, the force and displacement characteristics of the actuator are obtained experimentally. The actuator (system) model is obtained using the experimental data. Stiffness feedback is employed for control; in order to measure up the performance of the actuator with stiffness feedback, a comparison is made with displacement and force feedback. Simulations are carried out for regulation and tracking control. The control results demonstrate that, stiffness feedback enhances the performance of the (variable stiffness) actuator.