Safety Analysis Of Fully Automatic Operation System Based On Petri Net

As a new generation of Urban Rail Traffic Control System, Fully Automatic Operation System (FAO) is becoming the trend of urban rail signaling system at home and abroad, because of characteristics, such as high automation, integration, high efficiency and lower operating costs.But whether safety of FAO is better than traditional system of manual-operated mode or not, has been debated by domestic and foreign experts and scholars. Therefore, this paper will research the safety of FAO combined with the theory of safety analysis.Firstly, combined with the research status of FAO at home and abroad,this paper probes into the FAO’s concept, system architecture, functions, in order to understand FAO in-depth and comprehensively.Secondly, safety analysis methods of FAO based on Petri Net are promoted, and the three-phase method of overview process is built. Basic elements of building Petri Net models, the concept of critical states and retrospect searching algorithm are given. After searching of the model, effective measures, including interlocking and Time constraint, to eliminate risk states and critical states are put out.Finally, FAO’s safety functions such as establishing and cancelling a zone of protection and generating movement authorized are researched, and corresponding Petri net models are established. Combined with safety analysis methods and safety functional specification of FAO, two operation scenarios are selected, which are Passengers Transfer and Trains Coming to Station, and corresponding safety analysis models based on Petri net are established. Using reachability theory of Petri net, safety of two models about the operation scenarios are analyzed, which results in eliminating risk states and the critical states as much as possible based on sequence interlocking and inhibit interlocking. As a result, we could guide and perfect the design and operation measures of FAO based on these researches.