Supervisory Control For Decentralized Opacity Of Discrete Event System

Discrete event system is an artificial system composed of a series of discrete states and driven by events.Discrete event systems are widely and successfully used in computer networks and security,military defense,robotics,power systems,traffic control,and biochemistry.Since the 1990 s,lots of domestic and foreign scholars have conducted in-depth research in the field of discrete event systems.Some important properties such as diagnosability,detectability and opacity have been proposed.Opacity is an essential property of information security.It points out that there is another language with the same mapping as the system generated language.External observers or intruders cannot distinguish the system language from other languages under the mapping,thus the system secret is kept.In order to discuss the opacity supervisory control of discrete event systems in more depth,this thesis expands to the decentralized control framework based on the classic opaque supervisory control of discrete event systems,and discuss decentralized supervisory control for opacity between two cases with or without coordinator.In the discussion of the process of decentralized opacity supervisory control in discrete event systems,firstly,based on the formal definition of decentralized opacity,it leads to three decentralized opacity control problems.For strongly decentralized opacity and no decentralized opacity,construct a local supervisor according to sufficient and necessary conditions,and then form a global supervisor by fusing rules.In this research,a complete algorithm and relevant proofs are given.The problem of weakly decentralized opacity proves that such a supervisor does not exist.Compared with the previous research,this study extends the language-based opaque supervisory control to the decentralized control framework,and obtains the construction algorithm of the supervisor.In the process of constructing the global supervisor,a modular method is used,which is helpful to reduce the complexity of the algorithm.In the discussion of the discrete event system co-opacity supervisory control,first,based on the co-opacity defination and the concepts of local inference and global inference,the special case of ? = ? is discussed,which points out that there are multiple possibilities for external observers to infer the results.Because the construction of the co-opacity supervisors is closely related to the definition of the protocol,this article only discusses three kinds of co-opacity supervisory control under a given protocol,and assumes ? = ?.For strongly co-opacity supervisory control,gradually establish local supervisors and global supervisor,get the method of constructing co-opacity supervisors,and give the conditions for the existence of supervisors.The supervisory control of weakly co-opacity and no co-opacity are briefly discussed.Compared with the previous research,this study obtained the algorithm of the strongly co-opacity control problem under given conditions,and discussed the conditions for the existence of the supervisors.