COMPARISON OF STANDARD AND LIFTED ILC ON A MOTION SYSTEM

摘要

Iterative Learning Control (ILC) is a technique for improving the performance of systems or processes that operate repetitively over a fixed time interval. The basic idea of ILC is that it exploits every possibility to incorporate past repetitive control information, such as tracking errors and control input signals into the construction of the present control action. Past control information is stored and then used in the control action in order to ensure that the system meets the control specifications such as convergence. The goal of the research presented in this paper is to compare two different ILC techniques applied to the wafer stage of a wafer scanner motion system. Namely, we consider briefly the concepts of standard and lifted ILC and we evaluate the ILC performance in terms of tracking errors. We experience that ILC applied to the wafer stage has liability to deal with limited performance in the face of position dependent dynamics, with the fact that ILC does not account for setpoint trajectory changes and with stochastic effects.