Robust Control for Linear Stages in Electronic Manufacturing

Abstract

This paper considers the control of an x-y linear stage commonly used in electronic manufacturing. The challenge of the control problem includes coupled and nonlinear dynamics, flexibility due to the air bearing dynamics, geometric nonlinearity due to the interferometer position measurement, and tight cross-axis positioning requirements. We evaluate two control design approaches: robust control and gain scheduling. For the robust controller, a nominal linear time invariant design model is chosen with nonlinear dynamics considered as uncertainties. The choice of uncertainty characterization and weighting functions significantly affect the performance of the controller. For the gain scheduling controller design, robust controllers based on linearized models at several operating points within the workspace are combined. From the nonlinear simulation, it is shown that with suitable tuning, good performance is obtained throughout the work volume.