Design Of A Fail-safe Computer System For Urban Rail Transit

As to improve the train speed and line operational efficiency, Communication-Based Train Control system (CBTC) has been the main development tendency of urban rail transit. Vehicle controller, zone controller and the computer based interlocking controller are the most important parts of the CBTC system, and have critical influence to the safety and reliability of the entire system. The fail-safe computer is always taken as the carrier of these sub systems, its safety, reliability, availability and maintainability become the important affecting factors of the entire CBTC system safety and reliability. In this paper, a fail-safe computer system based on the two out of three voting structure is developed to meet the safety requirements of rail transit field.Firstly, this paper introduces several common structures of fail-safe computer system and their operation principle. The performance of these structures is also compared. As to meet the safety, reliability, availability and maintainability requirements of the urban rail transportation application, the two out of three voting structure has been taken as the basis of the overall structure of the fail-safe computer system.Secondly, the hardware system of the fail-safe computer system is totally designed with modular division, based on the two out of three voting structure. In this paper, a detailed description of the hardware operation principle of fault tolerance mechanism is given. Meanwhile, the functions of each module and their operating principle are also well described.Finally, the overall structure of the computer software system is described which has been divided into several levels. The platform control software module and the communication control software module are introduced in detail, and their functions are well described as well as their workflow. The communication management module, the synchronization module and the voting module are described in detail, and their functions and workflow are also introduced.The fail-safe computer system structures for urban rail transit are discussed in the paper and the advantage of two out of three voting structure has been proved. A new implementation of safe-fail computer system is given, including the hardware design and the software design, and it should be useful to the researchers and engineers.