Failure Propagation Analysis Via Interface Model And Its Application In Train Control Systems

Chinese Train Control System(CTCS)is one of the core techniques of high speed railway.As a typical safety-critical system,train control system failure might cause casualties,properties lost or environment damage.Recently,Model-Based Safety Analysis(MBSA)has been widely used in complex computer controlled systems.Compared with traditional methods,MBSA uses an accurate semantics model as the main approach as well as the analysis target for system description,and it has high flexibility and reusability.This paper chose the interface automata to describe system components and their interactions.Generally,interface automata are much simpler than related components,and the state number of two or more compositional interface automata can be effectively reduced.Therefore,the quality and efficiency of train control systems safety analysis can be improved markedly.A model-based system interface model failure propagation analysis approach has been proposed in this paper,and the main research contents are as follows:Firstly,the interface model and the failure propagation model has been merged,and basic faults and propagation faults have been defined.Moreover,new states,actions and transitions have been introduced to depict the system behaviour while the faults persist Secondly,the state space reconstruction strategy has been addressed.The state space has been divided into safety area,triggering area and hazard core.Through bidirectional reachability analysis,the transitions which cannot lead to the target events,including basic faults and hazard events,have been removed.Then the states have been combined so the state number can be reduced notably and the state space reconstruction has been implemented.Thirdly,based on breadth first search algorithm,the heuristic path searching algorithm has been designed.By defining a bounded integer k,the branches of the searching tree have been pruned.The efficiency of the cut set searching algorithm has been improved and the minimal cut set generation has been completed on Eclipse platform.Finally,the interface model and practical failure scenarios in train control systems have been combined deeply to achieve the modelling and analysis in CTCS-3.By analyzing the RBC handover process,the states,transitions and I/O actions of each subsystem have been determined.Then,the equipment faults in the scenario have been identified and the extended failure propagation has been completed,then the system model which contains the failure mode has been built.After that,the algorithm has been applied to assist the model analysis and the minimal cut set has been computed.Furthermore,the safety analysis has been completed.Through experimental results,the state space reconstruction strategy as well as the heuristic searching technique have reduced the state space remarkably,so the efficiency of train control system safety analysis has been improved.