Safety Analysis Of High-speed Maglev Train Speed Curve Monitoring Function

In order to achieve non-contact drive, high-speed maglev train system drives the train by supplying power to the long stator in the track, using the principle of long stator linear synchronous motor. This operation process is controlled by its train control system. High-speed maglev train control system is a typical distributed control system with the characteristics of centralized management and hierarchical control. Its each process control unit is a coordinated software intensive autonomous subsystem. The close coupling characteristic between high-speed maglev train and track makes the control process of high-speed maglev train control system more complicated.The high-speed maglev train control system plays a key role in the safety protection of the maglev train. In order to ensure the safety of high-speed maglev system, the safety-related functions of train control system must be implemented correctly. Safety analysis of high-speed maglev train control system can find out the causal factors of functional failure, which is a necessary work to guarantee safety. However, the complex characteristics of high-speed maglev train control system increase the difficulty of safety analysis.The main purpose of this paper is safety analysis of high-speed maglev train speed curve monitoring function. The main contents are listed as follows:First of all, this paper takes Shanghai Maglev Demonstration Line as an example, introduces the composition of high-speed maglev train control system and its ways to control the speed of the train. The speed curve monitoring function and its characteristic stop spot step control process are emphasized. Among them, the maximum speed curve monitoring function has an important effect on the over speed protection of the high-speed maglev train. The particularity of the speed control process in the division switching scenario is pointed out.Secondly, the train speed control process is analyzed to illustrate system safety in STAMP (Systems-Theoretic Accident Model and Process). The safety protection process is converted into the form of hierarchical control, and the controller process models are built to describe the control process of each level. The influence of human on system safety is also emphasized. Functional safety analysis steps of high-speed maglev train control system using STAMP’s safety analysis method STPA (System Theoretic Process Analysis) are summarized. Among these steps, the safety analysis of hierarchical structure needs iteration.Then, the STPA method is used to analyze the maximum speed curve monitoring function of high-speed maglev train control system. Hierarchical control structure and process models of each controller are established. The main analysis includes the speed protection layer, the current stop spot control layer and operator stop spot set layer. Thus, the hierarchical hazard causal factors and safety constraints of subsystems are obtained.Finally, according to results of safety analysis, the advantages of the method in recognizing hazard causal factors of the whole life cycle, the internal software and social factors are summed up. So, it not only meets the functional safety analysis requirements of high-speed maglev train control system, but also can be significant for the safety analysis of other modern software intensive engineering systems.