Robustness analysis of integrated flight and propulsion control systems for V/STOL aircraft

In this paper, we demonstrate the application of two analysis tools, the structured singular value μ and the v-gap metric, to the problem of evaluating the robustness properties of a multivariable integrated flight and propulsion control (IFPC) system for an experimental vertical/short takeoff and landing (V/STOL) aircraft configuration. Variations in aircraft parameters and dynamics over the V/STOL flight envelope are represented as linear fractional transformation (LFT) based parametric uncertainty descriptions, using a simple `black-box´ type modelling approach. Tight bounds on μ for the resulting high-order real parametric uncertainty model are computed by introducing small amounts of additional complex uncertainty, in order to analyse the stability robustness properties of the IFPC system. Analysis using the v-gap metric is also shown to provide much useful information about the robustness of the controller over the V/STOL flight envelope.