Optimal design of MIMO feed-forward controller for 6-DOF micro stage

With the aim to resolve the problem that the scanning fields of the micro stage continuously change during the exposure process of the whole scion wafer, an optimization design method for the MIMO feed-forward controller that can improve the tracking accuracy was proposed. The dynamic model of the 6-DOF micro stage was established and the scanning fields coupling of the model was decoupled. The parameters of the MIMO controller were optimized based on the Newton method, and the function of parameters automatically adjusted with the changing of scanning fields is realized. Nonlinear PID controllers were designed to improve the tracking effect at low frequencies. The simulation results show that the tracking precision increases evidently when the parameters of the MIMO feed-forward controller are optimized. During the exposure process, the maximum position error decreases by 74.97%, and the moving mean difference and the moving standard deviation of the position error decrease by 60.02% and 76.30%, respectively.