Chunhai Gao

Study on model-based safety verification of Automatic Train Protection system

In railway transportation area, the demand for safety of electronic devices is very high. Automatic Train Protection (ATP) system is a key equipment of systems for train control. Safety verification is an important issue. Conventionally, safety is ensured by testing manually with a set of test cases after system being integrated. However, testing is a very cost-intensive activity and a complete set of test cases is never achieved. This paper focuses on model-based safety verification approach dedicated to ATP system. We present a formal automaton to express safety, and main safety properties for train protection are studied deeply. And the rigorous semantics of the formal method enable model-based verification mechanisms for system safety. Furthermore, the implementation based on widely used development environment SCADE suite is presented. In conclusion, the strongpoint of the method is discussed.

A novel framework for supporting the design of moving block train control system schemes

A moving block philosophy is increasingly being implemented as part of communications-based train control (CBTC) systems in mass transit operations. Due to its complexity and safety criticality, it is difficult to develop formal methods to support the design of specific schemes. An innovative framework, based on topology mathematics, for supporting CBTC moving block system development is proposed in this paper. Within the new framework, the moving block train control logic is transformed into topological spaces representing the movement authority for trains. Using this approach, the verification of logic and safety properties can be performed by automatic assessment of the topological space. Within the paper the essential characteristics of moving block systems, train behaviour and static track-side infrastructure are analysed. As a result of this analysis, topological units are formed to represent train movement trajectory and standard railway network elements. Four calculation methods: dividing, trimming, covering and integrating, are described as standard unit operations. Finally, a case study is implemented to demonstrate how the method is advantageous for CBTC scheme layout development. It is found that the approach is able to bridge the gap between traditional, highly abstracted, formal methods and the specific safety-critical railway scheme designs.

Model-based software development for automatic train protection system

Automatic train protection (ATP) system is a safety critical application for railway signaling with high logic complexity, and it is typically embedded and real-time demanded. As the computational complexity of ATP system, traditional software development method cannot accommodate effectively. In this paper, we propose a novel Model-Based Development (MBD) scheme for ATP system. We argue that high quality software development in ATP system should not only rely on function design, but also on safety verification. A model-based development life cycle and verification approach are described. Furthermore, we present a case study, which is using the tool of SCADE suite. The approach can shorten the development period, enhance system safety, and meet challenges in safety critical software development.