Adaptive Failure Compensation Control Design For Nonlinear Systems And Its Applications

Beacause of the diversity and complexity of nonlinear systems, no universal effective designmethods have been developed, especially the adaptive fault-tolerant tracking control for the nonlinearsystems with the uncertain parameters and actuator failure. Based on the fuzzy control theory andbackstepping control method, this paper addresses the problem of adaptive actuator failurecompensation control for uncertain nonlinear systems and the application for aircraft control systems.Firstly, this paper summarizes the present development and research significance of fault-tolerantcontrol for nonlinear systems, and introduces the two powerful methods to process nonlinear systemcontrol, adaptive fuzzy control theory and adaptive backstepping control technology. Furthermore, weoverview the state-of-the-art of the fault-tolerant control for actuator failure of systems.Secondly, a new indirect adaptive control solution framework is formulated for state-spacecontinous time Takagi-Sugeno(T-S) fuzzy systems in canonical form with unknown parameters anduncertain actuator failures. Matching conditions for actuator failure compensation are required forboth the nominal design with system and failure knowledge and the adaptive design without systemand failure knowledge. For the developed indirect adaptive control scheme, the stabilty of theclosed-loop system and asymptotic state tracking properties are ensured.Thirdly, a fuzzy adaptive state tracking control scheme is developed for Takagi-Sugeno (T-S)fuzzy models in non-canonical form and with unknown parameters. Matching conditions have beenderived to make the states of the T-S fuzzy model track those of a given T-S-type reference model. Anovel parameter estimator is constructed using the real states and the parameter estimates. Based onthe estimated parameters, a fuzzy adaptive controller is proposed. Besides, a direct adaptive actuatorfailure compensation strategy is proposed.Finally, for a hypersonic vehicle with redundant elevators, an adaptive backsteppingfault-tolerant control scheme is designed for its longitudinal motion model. In the backstepping design,the dynamic surface control strategy is adopted to eliminate the explosion of complexity in caculatingthe derivatives of virtual control inputs by introducing two first-order filters. An appropriate controllerstruture is proposed and the matching conditions are derived for adaptive fault compensation for thevehicle with redundant elevators subject to uncertian actuator faults. The adaptation laws are designedto update parameter estimates to implement the adaptive controller.