WIT Press

Automatic Train Controller Safety Simulation


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WIT Press


R. A. V. Gimenes, J. R. de Almeida Jr. & T. R. Nogueira


Nowadays, we are observing an increased demand for better and safer mass transport systems. The supervision and control of these systems is made through an architecture known as Automatic Train Controller (ATC). The use of processors in ATC provides new challenges in a safety analysis. A typical railway system has a Speed-Distance Profile Generator that determines the maximum allowed speed in each track circuit. Dangerous situations are verified through the relative positioning and speeds between trains, switching machine positioning and other restrictions from operational commands generated by the ATC. Independent Safety Auditors should consider the failure modes of hardware and software in use. The safety analysis should consider alternative techniques to complete the complex task of evaluating how safe is the use of the processor and its associated software. Therefore, the use of simulation can improve and increase safety analysis, searching for fault states that could not be found in a static analysis. The main goal of this paper is to describe the development of a tool that simulates the behaviour of trains’ movement in a subway system, with boolean expressions. The set of boolean expressions coordinates all the movements in a subway line and the simulation provides the possibility to find out lack of safety, considering different combinations in those boolean expressions. Another important goal is to simulate equipment faults in order to investigate problems not visible in a static analysis or even in a practical field test. Preliminary results have shown that the use of a simulator to execute boolean expressions offers a great variety of tests, allowing the detection of unsafe situations, complementing software tests validation in a final release. Through simulation, it is possible to observe the behaviour of simulated objects in specific internal points which improves the completeness in safety analysis. Keywords: railway system, environment, safety, simulation, automation, modelling, boolean expression, microprocessor.


railway system, environment, safety, simulation, automation, modelling, boolean expression, microprocessor.