| With the progress of wireless communication technology, the reliability and availability of wireless communication are highly improved. Communication Based Train Control (CBTC) is the trend of urban railway traffic control system in the future.In the paper, the general principle and structure of VOBC device was introduced, as well as the application software which based on the platform of vital computer. According to the safety critical system development framework, the process designing the application software of on board device was introduced, including requirement analysis, general design, detailed design, modeling, verification on function and analysis on performance, etc.In the paper, the safety requirements and function requirements of VOBC application software were amply analyzed. On this base, the function partition and the design of son modules according to the Structure Design (SD) method were introduced.The Colored Petri Nets (CPN) was brought in to build the model of the application software for VOBC device. The modeling method was introduced firstly, and then the hierarchical models of the application software were built based on the structure design. The "top to bottom" idea was adopted to build the top model and son models which were comprised of model of Basic Protection, model of Enter CBTC Zone, model of Turnback Operation, model of Mode Conversion, etc.On the basis of the models, the state space analysis and simulation analysis were brought forward to analyze and validate the application software for VOBC device. The models of Mode Conversion and Turnback Operation were seriously studied. The function verification and safety analysis on the model of Mode Conversion were carried out by the method of state space analysis. The performance analysis on the model of Turnback Operation was carried out by simulation method. With the help of the verification and analysis, the system design would be modified and consummated. |
