Synchronizing decentralized control loops for overall performance enhancement : a Youla framework applied to a wafer scanner.

Evers, E., van de Wal, M. M. J., & Oomen, T. A. E.

20th World Congress of the International Federation of Automatic Control, Toulouse, France


Manufacturing equipment often consists of multiple subsystems. For instance, in lithographic IC manufacturing, both a reticle stage and a wafer stage move synchronously. Traditionally, these subsystems are divided into manageable subproblems, at the expense of a suboptimal overall solution. The aim of this paper is to develop a framework for overall system performance improvement. The method pursued in this paper builds on traditional designs, and extends these through a bi-directional controller coupling. The aim here is to optimize a criterion that specifies overall system performance. To achieve this, a new parameterization that relates to the Youla parameterization is developed that connects the bi-directional controller parameter affinely to the overall control criterion, which enables a systematic design. The performance improvement is confirmed in a case study using measured data from an industrial wafer scanner.

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