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This thesis presents recovery control schemes that enable a quadcopter unmanned aerial vehicle (UAV) model to cope with a faulty actuation system. First, the computational aspects of the design of fixed-order H1 controllers are investigated along with the performance they provide for the quadcopter UAV. Double-loop control structures are developed to control the translational velocities of the UAV subject to two different intermittent actuation problems. Fixed-order H1 controllers are designed for the nominal and the faulty modes of operation. These closed-loop modes are modelled as a switched system for which stability is analysed using minimum dwell time theory. Average dwell times are also computed by exploiting multiple Lyapunov-like functions that account for the delays in the detection of a fault. The other key contribution of this thesis is the design of a switched recovery control scheme that does not require the explicit detection of the faults. Sufficient conditions are given in terms of linear matrix inequalities (LMIs) coupled with a scalar, and depend on modified Lyapunov-Metzler inequalities. The switched recovery scheme developed consists of jointly designed state feedback gains switched according to a min-switching strategy that preserves closed-loop stability and satisfy a prescribed H1 or H2 performance. Finally, the inherent fast switching issue of the min-switching strategy is treated at the expense of conservative reformulated LMIs conditions. Furthermore, the state-dependent switched control scheme is extended to output feedback case. Simulation results demonstrate the potential of the developed switching recovery control schemes to overcome various actuation faults. |
