Development of a PID Based Closed Loop Controller for Shape Memory Alloy Actuators

Abstract

Shape Memory Alloy (SMA) spring actuator was designed and fabricated using commercially available NiTiNOL material by shape setting with the use of a special fixture. So, before applying the actuator to an application, a force characterization was conducted and force variation respect to uncontrolled temperature was analyzed. Due to the difference between force and temperature sensor's response time, a lag can occur between force and temperature measurements. Therefore, more controlled technique was further implemented by developing a PID based closed loop controller, together with a Graphical User Interface (GUI) which supports parameter control and sensor calibration. The controller technique was further justified through a thermal simulation. Finally, a force feedback controlling method also developed using the same PID technique for a force sensitive application, where a controlled force need to be maintained by varying temperature of SMA accordingly.