Robust Flight Control Design Supported by Flying Qualities Analysis

Abstract

In this work, a robust flight control law design and analysis is shown. Conventional flying qualities criteria are used to evaluate the performance of a longitudinal flight control law designed via robust control techniques. These criteria include C*, bandwidth/phase delay, Gibson frequency domain and dropback. The design in based on the C* criterion, and H1 and µ synthesis robust control techniques are applied. The conventional robust control law design structure is modified to include a feedforward path in order to attend phase requirements. For the µ synthesis design, an uncertainty model - obtained from Linear Fractional Transformations (LFTs) - is included in order to provide robustness against the variations in the aircraft response due to variations in the weight, center of gravity, inertia, airspeed and altitude. The robustness to this uncertainty is evaluated using µ analysis. The responses for some expected pilot inputs are also shown and commented.