长行程直线电机的迭代学习控制

Research on Iterative Learning Control to Long Stroke Linear Motor

光刻机工件台在扫描曝光过程中要求纳米级的定位精度,采用长行程直线电机粗动加洛仑兹电机高精密微动补偿的6自由度复合运动系统能满足要求。为减小微动电机的运动范围和加速度,必须提高直线电机的轨迹跟踪精度。提出了一种开闭环D型迭代学习控制律改善永磁直线同步电动机(PMLSM)的轨迹跟踪性能。控制器由三部分组成:PID控制器用来提高系统对扰动和参数变化的鲁棒性;前馈补偿器可提高系统的实时跟踪性能;迭代学习控制器则通过执行重复任务来不断向理想的控制信号逼近。实验结果表明,这种控制方法可以有效提高系统的轨迹跟踪精度。

An nm-level positioning precision is required in the process of scanning and exposing the wafer stage of lithography. A six degree of freedom（DOF） complex movement system can meet the requirement by using rough movement of long stroke linear motor and tiny movement of short stroke Lorentz motor. In order to reduce the movement scope and acceleration of Lorentz motor, the tracking precision of linear motor must be improved. An open- closed-loop D-type iterative learning controller（ILC） is proposed to improve trajectorytracking performance of permanent magnet linear synchronous motors（PMLSM）. The controller consists of three terms： a PID controller which enhances robustness to disturbances and system parameter variability, a feed-forward compensator which improves the real-time tracking ability and an ILC which generally improves the performance in the repetitive tasks by using the information from previous iterations. The experimental results show that tracking precision of PMLSM can be effectively improved by the scheme.