Multi-objective H/sub /spl infin// control applied to a wafer stage model

Abstract

This paper considers several practical aspects of designing multi-objective H∞ controllers. As a starting point, the LMI approach for designing multi-objective H∞ controllers, as well as for computing lower bounds on the achievable performance, is summarized. Both techniques are based on the Youla parameterization. Subsequently, two important aspects are to choose the initial observer-based controller used to construct the Youla parameterization and the poles of the Youla parameter itself. In this paper, a specific synthesis technique is suggested for designing H∞ controllers with an observer structure on which to base the Youla parameterization. Furthermore, a heuristic choice of the poles of the Youla parameter is presented. The results are illustrated in an academic example. Finally, the benefits of a multi-objective approach are demonstrated by applying the techniques to a model of a wafer stage; a mechanical positioning system used in IC manufacturing.

On the control of a single flexible arm robot via Youla-Kucera parameterization

“…In this method, the error between the complementary sensitivity functions of the nominal closed-loop system and closed-loop system using the reduced-order controller is converted to a frequency-weighted error between the Youla parameters of the full-order and reduced-order controllers and then the H ∞ norm of this error, subject to a set of linear matrix inequality constraints, is minimized. The paper 22 offers a specific synthesis technique for designing H ∞ controllers with an observer structure on which the Youla parameterization and a heuristic choice of the poles of the Youla parameter can be based. A hybrid frequency domain neurocontrol algorithm is discussed in ref.…”