Robust Stabilization for a Class of Nonlinear Fault Tolerant Systems

A. Swierniak, K. Simek, and A. Czornik (Poland)


fault tolerant control systems, boundednonlinearities, systems with jumps, measurement errors, two-level structure


In the paper we propose robust two-level control algorithm for a class of nonlinear systems ensuring satisfactory performance in the presence of measurement uncertainty and abrupt changes in parameters due to faults and changes of structure. The system is characterized by hybrid state space: to the usual plant state in Rn a discrete variable called mode, taking values in B = f1; 2; :::sg, is appended. The system is assumed to be linear except of bounded matched nonlinearities and the mode dynamics is described via random jumps modelled by a discrete-state Markov chain. Two level control structure is proposed to guarantee the robust ness in the sense of robust stability and guaranteed cost control. Proposed control strategy combines a lin ear local control law resulting from a solution of the JLQ problem for the linear decentralized part of the system and a nonlinear one which takes into account bounds imposed on the nonlinearities in the overall system and possibly nonlinear interconnections between subsystems. Both control laws depend on knowledge of modes and perfectly measurable state variables. The e¤ect of state measurement error on the system performance is investigated.

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