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Quantitative safety analysis of train control system based on statistical model checking

Lin Junting, Min Xiaoqin

Archives of Transport

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2022

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Vol. 61, iss. 1

7--19

EN

With the rapid development of communication technology, the Train-centric Communication-based Train Control (TcCBTC) system adopting the train-train communication mode to reduce the transmission link of control information, will become the direction of urban rail transit field development. At present, TcCBTC system is in the stage of key technology research and prototype development. Uncertain behavior in the process of system operation may lead to operation accidents. Therefore, before the system is put into use, it must undergo strict testing and security verification to ensure the safe and efficient operation of the system. In the paper, the formal modeling and quantitative analysis of train tracking operation under moving block are carried out. Firstly, the structure of TcCBTC system and the train tracking interval control strategy under moving block conditions are analyzed. The subsystem involved in train tracking and the uncertain factors in system operation are determined. Then, based on the Stochastic Hybrid Automata (SHA), a network of SHA model of train dynamics model, communication components and on-board controller in the process of train tracking is established, which can formally describe the uncertain environment in the process of system operation. UPPAAL-SMC is used to simulate the change curve of train position and speed during tracking, it is verified that the model meets the safety requirements in static environment. Finally, taking Statistical Model Checking (SMC) as the basis of safety analysis, the probability of train collision in uncertain environment is calculated. The results show that after accurately modeling the train tracking operation control mechanism through network of SHA, the SMC method can accurately calculate the probability of train rearend collision, which proves that the method has strong feasibility and effectiveness. Formal modeling and analysis of safety-critical system is very important, which enables designers to grasp the hidden dangers of the system in the design stage and safety evaluation stage of train control system, and further provides theoretical reference for the subsequent TcCBTC system design and development, practical application and related specification improvement.

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Methodology for monitoring and diagnosing faults of hybrid dynamic systems: a case study on a desalination plant

Achbi Mohammed Said, Kechida Sihem

Diagnostyka

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2020

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Vol. 21, No. 1

27--33

EN

The imperative of quality and productivity has increased the complexity of technological processes, posing the problem of reliability. Today, fault diagnosis remains a very important task because of its essential role in improving reliability, but also in minimizing the harmful consequences that can be catastrophic for the safety of equipment and people. Indeed, an effective diagnosis not only improves reliability, but also reduces maintenance costs. Systems in which dynamic behaviour evolves as a function of the interaction between continuous dynamics and discrete dynamics, present in the system, are called hybrid systems. The goal is to develop monitoring and diagnostic procedures to the highest level of control to ensure safety, reliability and availability objectives. This article presents an approach to the diagnosis of hybrid systems using hybrid automata and neural-fuzzy system. The use of the neural-fuzzy system allows modeling the continuous behaviour of the system. On the other hand, the hybrid automata gives a perfect estimate of the discrete events and make it possible to execute a fault detection algorithm mainly consists of classifying the appeared defects. On the implementation plan, the results were applied in a water desalination plant.

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Superposition Principle in Composable Hybrid Automata

Akhundov J., Tröger P., Werner M.

Fundamenta Informaticae

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2018

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Vol. 157, nr 4

321--339

EN

Hybrid automata are a well-established modelling approach. The formalism is used in many real-time and control systems engineering projects, which makes model composition an increasingly relevant topic. A well-defined composition support allows concurrent engineering activities and the validation of larger systems. However, many existing publications seldom consider it or make unrealistic assumptions on the model design. The article discusses the common problems with hybrid automata composition and presents a new formalism, called linear time-invariant hybrid automata (LTI-HA), which targets specifically these issues. Our approach considers the superposition principle for flow functions, which makes it specifically useful for practical modelling purposes in the spacecraft and control domain. We compare the approach to well-known related ideas, such as hybrid I/O automata. Several properties of composition, such as commutativity, are proven.