Event-triggered Fault Detection For Networked Control Systems Via Delta Operator Approach

Increasing demand in engineering,in company with the progress of wireless communication technology in China,has led to intensive research on Networked Control Systems(NCSs).Compared with the traditional control mode,NCSs have higher degrees of structural flexibility,and are easy to be diagnosed and maintained.However,the introduction of communication network into the control loop will lead to network-induced imperfections such as delays and packet dropouts,which will bring new challenges to the analysis and design of the whole system.Fault signals commonly exist in highly complex industrial systems.Serious consequences would be caused if they cannot be detected in time.Therefore,it is of paramount importance to detect the fault signal timely and effectively.The applications of NCSs are mostly based on digital platforms,using the communication network between the plant,sampler,controller and actuator.Under the condition of high-speed sampling,the delta operator approach can better unify the characteristics of continuous-time systems and discrete-time systems and has become a hot topic in recent years.In order to make full use of the limited network bandwidth and replace the traditional control strategy based on time cycle,event-triggered scheme is the focus of current research.Event-triggered fault detection for NCSs has attracted more and more attention of researchers.In this paper,the problem of fault detection filter(FDF)and observer-based controller co-design for delta-operator-based NCSs is studied.Specific research contents and innovations are described as follows:Firstly,for high-speed sampling control systems obtained via delta operator approach,the event-triggered scheme with adjustable parameters is introduced.The event-triggering parameters consider network bandwidth utilization ratio and fault occurrence probability simultaneously.Secondly,a new fault detection model of delta-operator-based NCSs with eventtriggering mechanism is constructed.A solution with asymptotical stability and H_?performance is obtained,considering time-varying delay in communication network.Efficacy of coordinated design of FDF and control strategy is verified by a numerical simulation example.Thirdly,further study considering packet losses and delays simultaneously in the communication network between sensor and fault detection filter is established.A stability criterion for delta-operator-based NCSs is obtained,which ensures that the residual system is mean-square asymptotically stable with H_?performance.Finally,a new Lyapunov-Krasovskii functional in ?-domain is constructed.Reciprocally Convex Combination lemma is used to get a less conservative stability condition in the process of stability analysis.Using YALMIP toolbox to solve filter and controller gains.