Research On Safety Risk Analysis Of Train Positioning System Based On GNSS

The Global Navigation Satellite System(GNSS)-based train combination positioning system can provide accurate and real-time train position and speed information for train control systems.It has played a key role in achieving train safety protection,controlling train safety intervals,reducing operating costs,and raising the automation level of trains.If the potential safety risks of the positioning system are not discovered,the lighter consequence is a train will be delayed,more seriously,a crash,which will cause great safety risks to the train operation,therefore,its safety is critical.The train satellite positioning system is a railway safety-related system,and the safety risk analysis must be carried out at all stages of the design and development life cycle.Based on the fault analysis,risk analysis theory and international relevant safety standards,this article adopts the Markov model,fault tree analysis,and interval-level analysis methods.According to the requirements of railway safety applications,this article analyze security risk of the hardware structure of independently developed GNSS-based train positioning system,which plays an important role in discovering weaknesses in the system and subsequently optimizing the system structure and ensuring the security of the system.The specific research work includes:First of all,comparing the advantages and disadvantages of traditional positioning methods,the advanced nature of the positioning system studied is illustrated.The analysis is based on the security requirements,functional requirements,features,and main architecture of the GNSS combined positioning system,which helps to grasp the overall overview of the system.Research and analyze its security redundancy structure,system logic framework and layout of each board card for subsequent research on security risk analysis.Second,in order to evaluate the system safety risk analysis,an important indicator of safety integrity risk,a Markov safety analysis model was established by analyzing the fault conditions of the positioning system and the system failure mode,and the integrity risk of the positioning system was analyzed and verified.The Tolerable Hazard Rate(THR)is used to quantitatively describe the integrity risk.The THR of the hazard side is estimated to determine the random hardware failure integrity level of the positioning system and ensure that the system safety function is safe and complete to reduce the risk to an acceptable level.Finally,for a one-sided problem in the risk analysis using a certain method alone,a new security risk analysis method based on Fault Tree(FTA)and Interval Analytic Hierarchy Process(IAHP)was proposed to comprehensively secure the hardware environment of the self-developed positioning system risk assessment.By constructing a hierarchical security risk security model,two judgment matrixes are constructed based on the structural importance of FTA basic events and expert evaluation based on IAHP model,and the difference between the two judgment matrixes is adjusted by weighting factor.The method combines the weights of the two judgment matrices to determine the priorities of the risks that lead to the system failure,identify key components that have a greater impact on the system safety,and provide basis for the subsequent improvement of weak links in the structural design of the positioning system.It can also reflect the security risk status of the entire system and provide more scientific and objective guidance for reducing risks and ensuring the security of the system.