Missile autopilot design via a modified LPV synthesis technique

Robust control via Linear Time-Invariant (LTI) H∞ or μ techniques has been extensively studied in the past few years. In this area, the theory is now quite mature. However, its limitation to linear time-invariant systems often remains a weakness which may give rise to well-founded criticisms. This has enforced the need for an extension of standard H∞ synthesis techniques to the class of Linear Parameter-Varying (LPV) plants. Many references are now available in the literature on this topic and several variants have been proposed to improve the original approach. The major improvement consists in incorporating knowledge on the rate of variation of the parameters. This constraint is of high practical interest and is naturally expected to relax significantly the conservatism of the original approach. Unfortunately, it often leads to computationnaly expensive algorithms. In this paper, we propose a very simple approach which consists in applying the original method to a modified LPV system. Thus, the attractive numerical properties of the initial algorithm are preserved. In return, the proposed method suffers from the lack of rigorous theoretical justification. This remains yet a minor drawback if we consider the practical interest of the method which is demonstrated on a realistic example, namely an autopilot design.