Study On Functional Safety Analysis Of Cbtc On-board ATP System

Communication Based Train Control is the new technique in Chinese railway signaling area. It is very complex at composition, structure, and functional level. It also has a high degree of software and hardware integration. The main standards and technical specifications are mainly controlled by foreign producers. Many potential safety risks are not mastered yet. In order to improve the management and control of safety risk of CBTC, it is an urgent need to analyse deeply the safety of CBTC, to find weaknesses of CBTC. The on-board ATP system is the core equipment and safety-critical system of CBTC which controls the train safe operation distance and protects train from over speed. It plays an important role in ensuring the CBTC safety and improving transport efficiency. The main ATP functions like train location/train speed determination and over speed protection are all the core functions for CBTC system. All kinds of random failure and system failure may leads to extremely serious results. So this thesis studies the application of functional safety analysis techniques through analyzing the safety of the main functions of on-board ATP based on the theory of the safety risk identification and analysis. The main research contents and achievements are listed below.Firstly, the structure of on-board ATP is analyzed from the aspect of internal unit and communication interface. Then the function and its requirements are defined as following: the train location/train speed determination and the over speed protection based on IEEE Std1474.1-2004(IEEE Standard for Communications-Based Train Control (CBTC) Performance and Functional Requirements), the safety-related standards and specifications for railway signaling and the theory of the reliability and safety. It provides a basis for the later hazard identification.Secondly, the method of hazard identification is summarized to select the method for hazard identification of the on-board ATP. The method integrating FMEA and brain-storm is used to identify the hazard of eight sub-functions and four interfaces in order to get the failure modes of the two main functions. Refer to appendix E of IEEE Std1474.1, FMEA is used to seek the causes of the failure from hardware, software, electromagnetic interference and other aspects of the failure modes. It provides the object for risk analysis.The method of risk analysis is summarized to select the method for risk analysis of the on-board ATP. Combined with the functional safety analysis of CBTC on-board ATP, the method of risk analysis based on Risk Matrix is studied and analyzed to analysis the risk of the on-board ATP. Aiming at fuzzy uncertainty of safety risk level analysis, the thesis presented the safety risk level analysis method of the on-board ATP hazards which based on fuzzy uncertainty theory. Fuzzy group decision making is used and the optimization model of experts’s information gathering based on minimum weighted Hausdorff distance is established. On this basis, we have designed and developed the corresponding safety risk analysis software.Lastly, we completed the safety risk analysis for six kinds of hazards of main functions of CBTC on-board system, and the risk reduction measures for the hazards which has a higher risk level are proposed from the aspect of software, hardware and system functions, etc. The method of funtional safety analysis studied in our thesis is also very important for protecting the safety of CBTC on-board system.