Design and flight testing of H∞ lateral flight control for an unmanned air vehicle

In this paper, the design and flight testing of a H_∞ Stability Augmentation System to improve the lateral handling qualities of a remotely controlled Unmanned Air Vehicle is presented. The problem of decoupling the roll response and the sideslip response using model-matching approach is considered along with control sensitivity minimization. In contrast to the conventional two degree of freedom controller design using model-matching approach, a single degree of freedom controller is designed in this paper for ease of implementation. Gain scheduling is avoided by designing the controller at a single flight condition that robustly stabilizes the closed loop system and retains performance characteristics at all flight conditions. For the purpose of determining the design point, two approaches, namely worst-case analysis and proximity of plant models is performed at all flight conditions. Robustness of the closed loop system to both structured and unstructured uncertainties at all flight conditions is examined through mu analysis. Final flight test results are compared with offline nonlinear simulations.