Research On Common Cause Failure Of The Train Control Safety Computer Based On COTS

With the application of computer technology in the field of railway signaling systems,the train control system is gradually developing towards the direction of intelligence and modernization.As the core equipment of the train control system,the train control safety computer is responsible for most of the safety functions,which is the key to ensure the safe operation of the train,and has higher safety requirements.Therefore,it is a research topic with great value to study the factors affecting the safety of train control safety computer by using qualitative and quantitative safety analysis methods.The common cause failure caused by the application of Commercial Off-The-Shelf(COTS)hardware and software,and a large number of redundant structures may bring certain security risks to the train control safety computer.The influences of common cause failure on system safety is analyzed based on the application of COTS components.The existing train control safety computer platform is improved and designed to further improve the performance of the system based on the prevention of common cause failure.Firstly,combining the characteristics of the existing train control safety computer platform in the laboratory and COTS components,the influences of COTS components on the safety of the train control safety computer platform is described.A hazard source analysis method based on Hazard and Operational Analysis(HAZOP)is proposed and typical failures in the system are analyzed,then a list of hazard source analysis is established.Furthermore,the common cause of failure risk of the train control safety computer is analyzed,and the common cause failure component group is identified,which lays a foundation for the quantitative analysis of the common cause failure.Secondly,the Bayesian network model with common cause failure under normal conditions and the one without common cause failure under ideal conditions are established.Aiming at the low efficiency of traditional Bayesian network inference calculation method,the bucket elimination method is proposed to calculate the failure probability of nodes in the model.The safety indicators in two cases are compared,which indicates that the common cause failure will reduce the safety of the train control safety computer.At the same time,under the influence of different common cause failures,the impact on system safety is analyzed.It is confirmed that the greater the influence factor of the common cause failure,the greater the impact on safety.Then the Bayesian network inference model is used to analyze the weak links of the system under the assumption of system failure,which can provide help for the future operation and maintenance.Finally,the existing train control safety computer platform is optimized,and a new type of train control safety computer is designed.Differential structure design principle and isolation principle are applied to prevent common cause failures.The processing unit,the fault tolerance and safety management unit,and the communication control unit all adopt the differential design.In terms of the implementation of isolation,the isolated power system and isolated communication method have been redesigned.The communication test and function test are carried out on the improved train control safety computer platform,which demonstrate the availability and implementability of the design.The design can effectively improve the communication capability and processing performance of the safety computer system.Besides,the design preventing the common cause failure happening effectively reduces the common cause failure.There are 63 figures,29 tables and 56 references.