LAUSR

Given an nth order, ν ‐control input, p‐measured output generalized plant, this article proposes a simple, direct approach to design an output feedback H ∞ controller with order nc satisfying ν(n−p)/p≤nc≤n−p for ν≤p , or p(n−ν)/ν≤nc≤n−ν for ν≥p . For this purpose, the output feedback H ∞ control problem is transformed into an H ∞ state feedback problem for an augmented generalized system. A class of plants for which this transformation always exists and the ensuing controller has order as above, is identified. As a result, for such plants, the reduced order H ∞ controller gains are found just by solving a simple linear matrix inequality problem used in state feedback based H ∞ control. The efficacy of the proposed approach is studied on some benchmark examples.