Robust 2-DOF H-infinity Controller for Highly Flexible Aircraft: Design Methodology and Numerical Results

摘要

The fly-by-wire control enables good-handling qualities for civil transport aircraft. However, the potential proximity of the aircraft's first flexible modes with the controller bandwidth may generate a spillover phenomenon causing aircraft instability if the flexible modes are not taken into account in the controller design. In this paper, a H_∞ robust synthesis method is used to design a two degrees-of-freedom controller for a most realistic model of the lateral dynamics of a highly flexible civil transport aircraft. The aircraft model is presented and analysed. Then, its order is reduced and modelling uncertainties are explicitly defined. Next, the control-law synthesis algorithm is explained and applied to the flexible aircraft model. Finally, numerical results are presented and discussed. They show the efficiency of the method since the closed-loop system meets a set of realistic specifications in the frequency and time domains.