Research On State Estimation And Detectability Of Networked Discrete Event Systems

Discrete event systems have the characteristics of modularity,flexibility,easy update,diagnosis and maintenance,and are widely used in flexible manufacturing,intelligent transportation,and smart city systems.However,with the development of shared communication network technology,both the control plant and the supervisior need to communicate through a shared(wired or wireless)communication network,which will inevitably bring delay or loss to the system.Therefore,how to deal with the analysis and control of networked discrete event systems with communication delays is a hot research topic that has attracted much attention in recent years.State estimation is the core of the analysis and control of complex networked systems,especially the detection of initial state and fault diagnosis.The initial state detectability is used to judge the ability of the system to determine the initial state after limited event observations.Fault diagnosis is used to detect whether a fault event has occurred and to diagnose the type of fault event.While detectability attempts to detect the state of the system,diagnosability tries to detect fault events in the system,and the current research results will contribute to the further study of the execution of network systems based on detectability.However,most of the existing researches are implemented under the framework of the general discrete event systems,and relatively little attention has been paid to the networked discrete event systems.Therefore,under the specific background of networked discrete event systems,the influence of delay on the detectability and fault diagnosis characteristics is discussed in this paper,the corresponding construction algorithm is proposed,and its validity is verified.The main research contents and innovative results of the paper are summarized as follows:1)Aiming at the problem of initial detectability in networked discrete event systems,a method for judging the initial detectability of network is proposed based on an algebraic framework of matrix semi-tensor product theory.The dynamics of the networked discrete event systems and the communication delay of the systems are represented by a matrix equation and a reachable matrix,respectively,the verification of the initial detectability in the network is converted into the calculation of the structural matrix,and the necessary and sufficient conditions for the initial detectability of the network are obtained.2)Aiming at the diagnosis problem of the networked discrete event systems,an eventbased fault diagnosis framework and an effective network diagnostic algorithm were proposed by taking event sets as fault information modeled by finite automata.The diagnosis of faults is transformed into the existence problem of system uncertainty loop,and the sufficient and necessary conditions of networked fault diagnosability are obtained.