Ru Niu

Bio: Ru Niu is an academic researcher from Beijing Jiaotong University. The author has contributed to research in topics: Backup & Fault tree analysis. The author has an hindex of 4, co-authored 6 publications receiving 77 citations.

Model-based safety assessment: Review of the discipline and its challenges

Abstract: Since its emergence in 1990s, Model-Based Safety Assessment (MBSA) has enjoyed significant interest from both academia and industry. The last decade has seen not only the development of a number of methods, techniques and tools, but also the gradual adoption of MBSA techniques by industry and its acceptance by regulators. However, the field of MBSA encompasses a large number of fundamentally dissimilar techniques. This paper presents a simple classification schema for MBSA techniques based on two criteria — provenance of the model and engineering semantics of component dependencies captured by the model. The classification organizes the existing techniques into a number of coherent families. Applicability, limitations and challenges of most prominent families of MBSA techniques are presented, and some of the common challenges faced by MBSA discipline are discussed.

Wireless test platform of Communication Based Train Control (CBTC) system in urban mass transit

Abstract: At present, Communication Based Train Control (CBTC) system has being researched and developed, and it is going to be the direction of development of train control system. The wireless communications system has become one of the essential subsystems of CBTC. In view of urban mass transit, this paper proposes a test platform about Wireless Local Area Network (WLAN) which has been widely applied in CBTC, and emphatically introduces two key tests: one is the AP coverage test and the other one is the SA handover test, then gives corresponding test data and results analysis. The results prove that test scheme provides the important evidences to optimize AP's arrangement along the track, realizes the uninterrupted communication between train and trackside, and ensures the safety of train operation in CBTC.

Automatic safety analysis of networked control system based on failure propagation model

Abstract: Recent developments in the modern control systems show a clear trend for increasing integration of a number of safety-related electronic systems — such as railway siganlling system and x-by-wire systems — that are replacing traditional mechanical controls These applications promise improved performance and safety through continuous high-capacity realtime data exchanges and reconfiguration in abnormal situations However, safety analysis of networked systems is becoming extraordinarily difficult because of the complexity of interactions between components and the number of possible backup modes The traditional analysis techniques are subjective and do not facilitate reuse, thus, making the safety analysis process time-consuming and error-prone This paper extends the failure propagation model with a set of temporal operators, in order to demonstrate more accurate representation of practical failure behaviors of networked control systems Computation laws of temporal operators and combinatorial operators are abstracted to transform complex temporal expressions into a standard form In this way, the models can be solved automatically The preliminary design of Communication Based Train Control (CBTC) system for Yizhuang Line in Beijing is used to demonstrate the approach

Automatic safety analysis of of computer-based railway signalling system

Abstract: Ensuring safety in railway signalling system is always considered as significant as a guarantee of the safe and efficient operation of the whole railway. In fact, safety analysis of the signalling system with distributed computer technique is becoming extraordinarily difficult because of the frequent and complex interaction between components and the various backup modes. The dominant approaches are subjective, difficult to be reused, not well structured, thus leaving the safety analysis process time-consuming and error-prone. This paper develops a hierarchical methodology for safety analysis based on the failure propagation model and state-transition model. Unlike traditional safety analyses, the proposed approach demonstrates more accurate representation of practical failure behaviour in computer-based signalling system. Dynamic properties, system structure and failures in component level are separately modelled in different layers, and connected with synthesis laws. The analysis can be easily refined as the system design progresses and automatically produces safety-related information to help engineer in making design decisions. The preliminary design of Communication Based Train Control (CBTC) system for Yizhuang Line in Beijing is used to demonstrate the approach.

Formal safety verification for TTP/C network in Drive-by-wire system

Abstract: TTP/C is a member of the time-triggered protocol (TTP) family that satisfies Society of Automotive Engineers Class C requirements for hard real-time fault-tolerant communication. As a communication network designed for safety-critical system, it is essential to verify its safety depending on formal methods. We investigate the fault-tolerant and fault-avoidance strategies of TTP/C network used in Drive-by-wire system, with Markov modeling techniques, and evaluate the failure rate subject to different failure modes, taking into account both transit and permanent physical failures. Generalized Stochastic Petri Net (GSPN) is selected to model concurrency, non-determinism properties and calculate Markov model automatically. A model with 157 states and 78 transitions is built. The result of experiments shows that failure probability of TTP/C network in 7-nodes DBW system varies from 10-6 to 10-10 with different configuration. And diagnose mistakes are proved to be a critical factor for the success of membership service.

Safeware: System Safety and Computers

Abstract: Will Tracz, our esteemed editor and Used-Program salesman, has written an entertaining, non-technical book dealing with the practice (and lack of) of software reuse. Its a collection of essays, mostly rehashed (reused?) and updated from various columns and papers published over the years.. Its a short (a bit over 200 pages) easy reading and enjoyable book (I read most of it in one sitting). Some of the essays discuss what was printed in the past and a discussion of the current status of the points.

An overview of fault tree analysis and its application in model based dependability analysis

Abstract: I provide an overview of the Fault Tree Analysis method.I review different extensions of fault trees.A number of model-based dependability analysis approaches are reviewed.I outline the future outlook for model-based dependability analysis. Fault Tree Analysis (FTA) is a well-established and well-understood technique, widely used for dependability evaluation of a wide range of systems. Although many extensions of fault trees have been proposed, they suffer from a variety of shortcomings. In particular, even where software tool support exists, these analyses require a lot of manual effort. Over the past two decades, research has focused on simplifying dependability analysis by looking at how we can synthesise dependability information from system models automatically. This has led to the field of model-based dependability analysis (MBDA). Different tools and techniques have been developed as part of MBDA to automate the generation of dependability analysis artefacts such as fault trees. Firstly, this paper reviews the standard fault tree with its limitations. Secondly, different extensions of standard fault trees are reviewed. Thirdly, this paper reviews a number of prominent MBDA techniques where fault trees are used as a means for system dependability analysis and provides an insight into their working mechanism, applicability, strengths and challenges. Finally, the future outlook for MBDA is outlined, which includes the prospect of developing expert and intelligent systems for dependability analysis of complex open systems under the conditions of uncertainty.

Radio Communication for Communications-Based Train Control (CBTC): A Tutorial and Survey

Abstract: Over the last decade, railway industry has seen a huge transition from conventional railway signalling systems to modern, communication-based signalling systems. Communications-based train control (CBTC) is a modern communication-based system that uses radio communication to transfer timely and accurate train control information. CBTC is the choice of mass-transit railway operators today, with over a hundred systems currently installed worldwide. The safety-related, time-critical applications such as train control impose stringent reliability and availability requirements on the radio communication technology used. IEEE 802.11 Wi-Fi, despite being originally developed for stationary users within a limited area, has prevailed as the de-facto radio technology for CBTC. Unfortunately, very limited literature is publicly available on this topic due to the highly competitive nature of the railway industry. We believe that this paper fills the much-needed gap. It aims to present a comprehensive tutorial, as well as a survey of the state-of-the-art, of CBTC and the role of radio communication in it. The operation and fundamental components of a CBTC system are discussed. A summary of the evolution of the communication technologies used for modern railway signalling is presented. The benefits and drawbacks of using a radio communication technology, particularly Wi-Fi, and the challenges it introduces, are discussed. Best practices in the design of a CBTC radio network and the measures to optimize its availability are discussed, while using the currently in-progress Copenhagen S-train CBTC project as a reference. An overview of the CBTC standardization efforts, as well as the IEEE CBTC standard—frequently overlooked due to its limited scope—is included. This paper is concluded by providing a number of potential directions for future work.

Survey on Driverless Train Operation for Urban Rail Transit Systems

Abstract: The length of metro lines with driverless train operation (DTO) systems is increasing globally and is predicted to triple in the next 10 years. This paper gives the history and future trend of the DTO systems. The opportunities provided by the DTO systems, such as lower operation costs, increased capacity, and energy efficiency, are explained and the relevant research are reviewed. Furthermore, the challenges faced by the DTO systems are analyzed, such as safety issues, train control technology, and emergency situations.

Model-based dependability analysis: State-of-the-art, challenges, and future outlook

Abstract: Over the past two decades, the study of model-based dependability analysis (MBDA) has gathered significant research interest. Different approaches have been developed to automate and address various limitations of classical dependability techniques to contend with the increasing complexity and challenges of modern safety-critical system. Two leading paradigms have emerged, one which constructs predictive system failure models from component failure models compositionally using the topology of the system. The other utilizes design models—typically state automata—to explore system behavior through fault injection. This chapter reviews a number of prominent techniques under these two paradigms, and provides an insight into their working mechanism, applicability, strengths, and challenges, as well as recent developments within these fields. We also discuss the emerging trends on integrated approaches and advanced analysis capabilities. Lastly, we outline the future outlook for MBDA.