Hybrid Active-passive Robust Fault-tolerant Control Research Of Nonlinear Networked Control System Under Discrete Event-triggered Communication Scheme

In recent years,network control has been a major research topic in the control field.Networked control system(NCS)is complicated by problems,such as,network-induced delay,data packet dropout,model uncertainty,wastage of limited network resources,and various failures occurring at any time.All these problems may downgrade the system performance and even cause system instability.Given that real industrial systems have more or less nonlinear characteristics,Therefore,improving the security and reliability of nonlinear NCS(NNCS)by designing a fault-tolerant controller is significant.Fault-tolerant control of NNCS is divided mainly into two types: passive fault-tolerant control(PFTC)and active fault-tolerant control(AFTC).Both methods have distinctive advantages;however,the former is conservative and cannot effectively tolerate unknown faults,whereas the latter cannot ensure system stability during controller restructuring.Besides,most fault-tolerant controls of NNCS use periodic time-triggered communication scheme(PPTCS);in such a scheme,the data are communicated periodically,thereby resulting in serious wastage of network resources and aggravated occurrence of network-induced delay and data packet dropout.On this basis,an uncertain NNCS with time-varying delay and external finite-energy disturbances is investigated in this study.Adopting a more resource efficiency scheme named discrete event-triggered communication scheme(DETCS),under the circumstance of any actuator fault with failure,the hybrid active-passive robust fault-tolerant control research on NNCS is conducted in terms of system modeling,design and analysis of observer and controller.The synergy design of DETCS and the controller with major study aspects is as follows:1)Modeling of close-loop fault NNCS under DETCSAn event-triggered communication scheme related to system state is introduced.Considering the existence of network-induced delay and external finite-energy disturbances,the close-loop fault NNCS models of nominal,uncertainty anddisturbance are established using the T-S fuzzy model.2)Synergy design between hybrid active-passive robust fault-tolerant control of NNCS and DETCSUsing the parallel distributed compensation(PDC)method and the properly constructed Lyapunov-Krasovskii function based on the models established above,the delay/event-dependent sufficient conditions for NNCS with integrity,robustness,and robust H_?performance under DETCS are derived.The solution method to the synergy design between hybrid active-passive fault-tolerant controller and DETCS is provided in the form of linear matrix inequality(LMI).Moreover,a fault detection observer(FDO)is designed on the basis of H_?control theory to realize real-time detection of faults.Subsequently,PFTC and AFTC are designed to maintain system stability during the occurrence of known faults.The speed of system performance deterioration can be mitigated in the initial occurrence of unknown faults by the function of PFTC.After obtaining accurate fault information,AFTC will restructure the controller immediately to compensate the influences of such unknown fault on the system and maintain the system stability.3)Bumpless switching research on uncertain hybrid active-passive robust H_?fault-tolerant controller of NNCS under DETCSThe mismatch of control signals during different controllers switching may easily influence the controller performance and thus the system security;thus,the smooth switching problem of the restructured controller must be considered when designing hybrid active-passive robust H_?fault-tolerant controller of NNCS.In this study,a properly designed smooth switching function is introduced to achieve controller signal match during switching,decrease the occurrence of signal jitter and signal jump during switching,and ensure the system security when any actuator fault occurs.4)Design and realization of the simulation program for hybrid active-passive fault-tolerant control of NNCS under DETCSThe simulation results have demonstrated that the designed FDO can detect fault information accurately.Comparing the effects of AFTC,PFTC,and hybrid active-passive fault-tolerant controllers shows that the proposed hybrid controller is better than the two other controllers because it can tolerate known and unknown faults effectively.Moreover,the “bumpless” switching between controllers has been realized by the appropriately selected smooth switch function.Furthermore,the introduction of event-triggered conditions has greatly saved limited network resources and enhanced the network resource utilization rate.