Research On Adaptive Fault-tolerant Control Of Nonlinear Systems With Actuator Fault And Disturbance

Recently,the automation degree of industrial systems has developed rapidly;the control requirements have been continuously promoted.Accordingly,the system components and the non-linearity are increasing,which brings great challenges to the analysis and synthesis of the system.On the one hand,the control system may suffer from faults because of long time operation or wrong operation;on the other hand,the system components have been increased,which implies that the channels of the disturbances enter into the system have also been increased.The effects of multi-sourced and mismatched disturbances on the system become more complicated,which in return increases the control difficulty of the automation system.Faults and disturbances will degrade the system performance and even directly destroy the stability of the system.Therefore,improving the fault tolerance abilities of the nonlinear systems,compensating for the effects of faults on the system,and rejecting the external disturbances are crucial to the stabiliy of nonlinear systems.This paper focus on the fault-tolerant control(FTC)for nonlinear systems subjected to actuator faults and external disturbances,the main research contents include the following parts.1)The robust FTC approach for a class of Lipschitz nonlinear systems with actuator faults is investigated.Considering the Lipschitz nonlinear system subjected to actuator fault and disturbance,a novel robust sliding mode fault-tolerant control appoach is designed to guarantee the stability of the system.First,a composite observer is constructed to estimate the states,actuator faults and disturbances information simultaneously.Then,a robust sliding mode fault-tolerant controller is designed based on the observer.In the proposed method,the disturbances are divided into two parts,and the stability of the system is analyzed based on the Lyapunov theory.Finally,the simulation results verify the effectiveness of the proposed method.2)The composite observer-based FTC method for a class of affine nonlinear systems is considered.Take the electric vehicle(EV)system as an example,considering a class of EV systems with actuator faults and disturbances,a novel sliding mode control(SMC)method is presented to guarantee the tracking performance.First,a novel EV system with actuator faults and unmatched disturbances is established,a novel composite observer is constructed based on the observer structure designed in last chapter to obtain the states and the lumped disturbances.Then,by using the estimated values,a novel sliding mode fault-tolerant controller in designed.In the proposed method,two adaptive parameters are introduced to increase the system response.Finally,two cases are used to verify the effectiveness of the proposed method.3)The sliding mode FTC method and disturbance rejection approach for a class of non-affine nonlinear systems is addressed.Take the mechanical system as an example,considering a class of non-affine nonlinear systems,an adaptive FTC scheme is discussed.First,the system model with actuator faults and disturbances is established.Then,a composite observer is constructed to estimate the states,actuator faults and disturbances.In the observer,the disturbance upper bound is not needed.Furthermore,a novel discrete adaptive sliding mode fault-tolerant controller is designed to realize the tracking performance and the convergence performance is proved.Finally,the fault tolerance ability of the presented method is verified by the simulation results.4)The event-based FTC method for a class of n degree nonlinear systems is investigated.Considering a class of nonlinear systems with actuator faults and disturbances,an event-based adaptive FTC approach is designed to compensate for the influences of actuator faults and disturbances.First,a novel event trigger mechanism is designed.Then,a novel composite observer is designed.In this observer,on the one hand,similar to the last chapter,the upper bound information of the disturbance is not needed;on the other hand,the triggered output values are used instead of the continuous values,and then the system unknown variables are observed with less output information.Furthermore,an event trigger-based adaptive sliding mode fault-tolerant controller is constructed based on the estimated values to compensate for the influences of actuator faults and disturbances and to reduce the transmission loads.Finally,the simulation results verify the fault tolerance abilities of the proposed method.5)The fuzzy logic aided adaptive event trigger FTC method for a class of nonlinear systems is developed.Considering a class of n degree nonlinear systems with actuator faults and disturbances,a fuzzy logic aided adaptive sliding mode FTC strategy is discussed to realize the fault compensation and disturbance rejection.First,the fuzzy logic theory is utilized to approximate the nonlinear parts.Then,a novel event trigger mechanism is constructed and a novel composite fuzzy observer is designed based on the triggered output information.In the presented observer,the disturbance can be high-order derivative,which is closer to the practical system.Furthermore,based on the adaptive trigger mechanism in the control channel and the estimated information,a novel event trigger-based adaptive fuzzy sliding mode FTC algorism is designed.Finally,the fault tolerance ability of the proposed method is verified by the simulation results.