Adaptive Fault-Tolerant Control Of Several Classes Of Nonlinear Systems

In the practical control systems,the operation of the system is often encountered the effect of actuator failure,sensor failure and system failure.When the fault occurs,how to keep the control system stable and achieve acceptable performance index have become the research focuses and hot issues of the control field.Therefore,the control design and performance analysis of nonlinear system with actuator fault is a practical research topic.In this thesis,we focus on the problem of the controller design and the convergence and stability of the closed-loop system for the fault-tolerant control of several classes of nonlinear systems with actuator faults by using backstepping technology.The main work is given as follows:1.For a class of non-lower-triangular nonlinear system,the adaptive finitetime fault-tolerant control problem is studied when the system encounters actuator fault and system fault.An adaptive finite-time fault-tolerant control is proposed by using backstepping technology and neural network control.The proposed controller can ensure that all signals in the closed-loop system are semi-global,and the tracking error can converges to a small neighborhood near the origin in finite-time.The effectiveness of the strategy is verified by simulation.2.An adaptive fuzzy control method based on prescribed performance is studied for a class of strict feedback system with actuator fault and unmodeled dynamic.Different from the existing prescribed performance function,an improved performance function called finite-time performance function is proposed.It is proved that the proposed controller can guarantee that all signals in the closed-loop system are bounded and the tracking error converges to a predetermined region.The simulation results verify the proposed control scheme.3.An improved performance constrained adaptive control strategy is proposed for the output tracking control problem for a class of nonlinear high-order system with actuator fault.The actuator fault includes bias fault and gain fault models.The controller design of high-order system is dealt with by adding power integrator.An output tracking control scheme is proposed by usingthe method of combining backstepping and classical adaptive control.The scheme can ensure that all signals of the closed-loop system are bounded,and the tracking error converges to a predetermined region in a finite time.Finally,the proposed control scheme is verified by the simulation results.