Improved Internal Model Control based Closed Loop Controller Design for Second Order Piezoelectric System with Dead Time

Precision control and positioning of devices at nanometer level have become ubiquitous in several industrial applications. Piezoelectric actuators offer flagship performance in this domain with its capability to actuate with resolution up to fraction of diameter of an atom. With important advantages like high accuracy, rapid response, high torque, compact form-factor they are being used several ultra-precise mechatronic systems. However, its performance is effected by severe nonlinearities, mostly hysteresis which needs to be tacked by proper controller design along with suitable plant model. This research first mathematically models the piezoelectric actuator as a second order plant using Dahl model for hysteresis. Parameters of the plant and nonlinear hysteretic term are experimentally identified using a commercially available piezoelectric actuator. An improved Internal Model Control approach is then explored which has a simpler structure than conventional IMC. As PID control is the most widely used control regime for practical usage, the research also presents an equivalent PID structure of the controller. The presence of system dead time has been considered and approximated using zero order `Pade' approximation. Results suggest an improvement in the controller response over a traditional control in terms of step response, impulse disturbance as well as noisy environment.