Robust H Design for Lateral Flight Control of Highly Flexible Aircraft

Abstract

A lateral flight control design for a flexible aircraft is presented. It is based on a standard two-input two-output problem formalism and H2 synthesis. The proposed approach consists of two steps. The first step deals with the synthesis of a dynamic output feedback satisfying modal specifications on the rigid modes, stability requirements on the structure and performance robustness with respect to the various loading cases. The originality in the synthesis setup we propose lies in the fact that it combines eigenstructure assignment,H2 frequency domain synthesis and parametric robustness design. The second step uses a recent theoretical result to transform a given compensator into an linear quadratic gaussian (LQG) compensator involving a judiciously selected on-board model. The two degree of freedom compensator thus obtained allows time domain specifications in response to the pilot’s commands to be met satisfactorily.We provide a detailed discussion of the approach together with the aircraft models used and corresponding closed-loop analysis.