Second-order reset elements for stage control design

Abstract

In dealing with inherent limitations during stage control design, the possibilities of a second-order reset element (SORE) are studied, in particular, a second-order low-pass filter with reset. Inducing significantly less phase lag, which follows from describing function analysis, SOREs allow for a significant increase of bandwidth in comparison to linear second-order elements. Being part of a reset control design procedure, loop-shaping of the linear feedback loop with a reset element will be based on a describing function description of this element. For the reset control system, closed-loop stability will be verified by solving linear matrix inequalities. The validity and predictive value of the control design procedure (both in terms of stability and performance) will be demonstrated by means of (measurement) results obtained from an industrial wafer stage system.