A CPN-based approach for studying impacts of communication delays on safety and availability of safety-critical distributed networked control systems

With the great advances in computer science and communication technology, more and more control systems are implemented as Distributed Networked Control Systems (DNCSs). Due to the nature of the time delay of communication networks, it is of importance to investigate how communication delays affect the systems from different perspectives. Most of the literature by far focus on analysing the impacts of time delays on system stability or safety control with mathematical models (i.e., differential equations), which are of interest in the early phases of system development (e.g., the conceptual phase). However, in the later phases of system development (e.g., architecture design or system implementation), qualitative as well as quantitative safety analysis based on system models that describe the concrete structures, interactions between components, and state transitions of the underlying systems is desirable.Additionally, the availability of a control system is of interest from the perspective of operation. This paper studies the impacts of communication delays on the safety and availability of DNCSs by a Coloured Petri Net based (CPN-based) approach.To exemplify the proposed approach, a simplified Communication-based Train Control (CBTC) system is presented.