Integration of H∞ and Time Domain Specifications Using the Convex Combination Method

Abstract

Aircraft flight control systems often require the satisfaction of multiple simultaneous specifications to fulfil different robust stability and performance objectives along with good handling qualities. Many specifications such as H ∞-norm, overshoot, undershoot, etc are convex with respect to the closed loop transfer matrix. In this paper it is suggested to use the convex combination method to integrate H ∞ frequency domain specifications with additional time domain constraints. For this purpose, existing techniques are used to design an H ∞ controller which is then modified in a new structure using Qparametrization which makes the problem convex in the new design parameter Q. At this stage, if different controllers are obtained for each convex specification, they can be combined into a single controller using convex combination which could satisfy all specifications.