Communication Based Train Control Research Articles

A CPN-Based Approach for Studying Impacts of Communication Delays on Safety and Availability of Safety-Critical Distributed Networked Control Systems

With the great advances in computer science and communication technology, more and more control systems are implemented as distributed networked control systems (DNCSs). Due to the nature of the time delay of communication networks, it is of importance to investigate how communication delays affect the systems from different perspectives. Most of the literature by far focus on analyzing the impacts of time delays on the system stability or safety control with mathematical models (i.e., differential equations), which are of interest in the early phases of the system development (e.g., the conceptual phase). However, in the later phases of the system development (e.g., architecture design or system implementation), qualitative as well as quantitative safety analysis based on system models that describe the concrete structures, interactions between components, and state transitions of the underlying systems is desirable. Additionally, the availability of a control system is of interest from the perspective of operation. This article studies the impacts of communication delays on the safety and availability of DNCSs by a colored-Petri-net-based approach. To exemplify the proposed approach, a simplified communication-based train control system is presented.

Model-Based Safety Analysis of Movement Authority Scenario in TcCBTC system

Train-centric communication based train control (TcCBTC) system contains a variety of uncertain factors in the operation process, and the generation scenario of movement authority is a real-time process. In order to judge the impact of uncertain factors on system safety, it is necessary to conduct formal modeling and analysis for this implementation process. Aiming at the modeling and analysis of the system in an uncertain environment, firstly, the implementation process of TcCBTC movement authority was analyzed, and the hazard source identification is carried out by combining the hazard and operability study (HAZOP) method. Secondly, the movement authority generation process is modeled based on the stochastic hybrid automata theory, and the statistical sample data are simulated in UPPAAL-SMC. Finally, the statistical model checking algorithm was used to analyze the model quantitatively. The results showed that the model could meet the functional attribute requirements of movement authority generation in TcCBTC system, and describe the uncertain environment in the process of system operation. SMC method could quickly verify the impact of uncertain factors on the system, and provide a certain theoretical basis for subsequent TcCBTC system development and relevant specifications.

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

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 rear end 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.

Architecture Design and Reliability Evaluation of a Novel Software-Defined Train Control System

Communication-based train control (CBTC) has been the prevailing technology of the urban transit signaling system. However, CBTC also faces a few issues to extend and maintain because of its complicated structure. This paper presents a novel urban transit signaling system architecture, software-defined train control (SDTC), which is based on cloud and high-speed wireless communication technology. The core functions of the proposed SDTC, including the onboard controller, are implemented in the cloud platform, with only sensors and input–output (IO) units remaining on the trackside and the train. Because of the scalable framework, the system function can be expanded according to the user’s demand, making signaling as a service possible. With warm standby server redundancy, SDTC has better reliability. Compared with the traditional CBTC architecture, the mean time between failures is improved by 39% by calculating typical project parameters by the Markov model based on some assumptions.

Enhancing Dependability Analysis Provisioning in CBTC Wireless Communication System With Age of Information

As a crucial part of the communication-based train control (CBTC) system, the wireless communication subsystem is responsible for transmitting safety-critical information, which directly affects the safe and efficient operation of the urban rail transit. The dependability analysis method for wireless communication in CBTC is critical and necessary to ensure the stable transmission of safety-critical information. However, most of the existing researches in CBTC lack a unified evaluation index to analyze the wireless communication dependability. In this paper, the dependability of wireless communication system in CBTC is established. To be specific, timeliness, integrity, security, and safety are used to describe the dependability of CBTC wireless communication system in our definition. The age of information (AoI) is used to quantitatively analyze the dependability in the CBTC wireless communication system. To verify the effectiveness of the proposed dependability analysis method, we quantitatively introduce the dependability of wireless communication system in CBTC with different scenarios, including packet-drop, re-transmission, handoff, and cyber-attack. Simulation results show that the designed dependability analysis method with quantized AoI can efficiently describe the dependability of CBTC wireless communication system in different scenarios.

Ultra-safe and reliable enhanced train-centric communication-based train control system

Ultra-safe and reliable enhanced train-centric communication-based train control system

Intelligent train control for cooperative train formation: A deep reinforcement learning approach

Considering the intelligent train control problem in long-term evolution for metro system, a new train-to-train communication-based train control system is proposed, where the cooperative train formation technology is introduced for realizing a more flexible train operation mode. To break the limitation of centralized train control, a pre-exploration-based two-stage deep Q-learning algorithm is adopted in the cooperative train formation, which is one of the first intelligent approaches for urban railway formation control. In addition, a comfort-considered algorithm is given, where optimization measures are taken for providing superior passenger experience. The simulation results illustrate that the optimized algorithm has a smoother jerk curve during the train control process, and the passenger comfort can be improved. Furthermore, the proposed algorithm can effectively accomplish the train control task in the multi-train tracking scenarios, and meet the control requirements of the cooperative formation system.

Robust Cooperative Control of Networked Train Platoons: A Negative-Imaginary Systems’ Perspective

By virtue of the wide implementation of communication-based train control (CBTC) systems and moving-block signaling systems, cooperative control for trains shows great potential in improving line utilization, passenger comfort, and operation flexibility. However, the operation of train platoons faces great challenges induced by model uncertainties, unpredictable resistances, and time-varying disturbances. To address these problems, consensus-based robust cooperative control schemes are presented in this article for both homogeneous and heterogeneous train platoons. Taking the physical connection between carriages into consideration, each train in the platoon is modeled as a negative-imaginary (NI) system, and the NI property is rigorously proved in this article. In the foundation of cooperative control theories of NI systems, robust strictly NI controllers considering the network topology are utilized to track a predefined motion reference. The proposed controllers are robust to both mass uncertainties and external disturbances. Moreover, the line utilization for the railway system and the ride comfort for the passengers are improved using the proposed control schemes. Numerical simulations are given to showcase the effectiveness and robustness of the proposed controllers.

A Resilience-Based Security Assessment Approach for CBTC Systems

With the rapid development of urban rail transit systems, large amounts of information technologies are applied to increase efficiency of train control systems, such as general computers, communication protocols, and operation systems. With the continuous exposure of information technology vulnerabilities, security risks are increasing, and information is easy to use by malicious attackers, which can bring huge property and economic losses. The communication-based train control (CBTC) system is the most important subsystem of urban rail transit. The CBTC system ensures safe and efficient operation of trains, so the quantitative assessment of cyber security is quite necessary. In this paper, a resilience-based assessment method is proposed to analyze the security level of CBTC systems based on indicators of both the cyber domain and the physical domain. The proposed method can demonstrate the robustness and recovery ability of CBTC systems under different security attacks. Based on the structural information entropy, the fusion of different indicators is achieved. Two typical attacking scenarios are analyzed, and the simulation results illustrate the effectiveness of the proposed assessment approach.

Design of system-level hot standby redundancy-based signal system

Focusing on the improvement of the availability for signal systems, a system-level heterogeneous hot standby redundancy-based signal system is discussed. The system includes a communication-based train control system (CBTC), a track circuit-based train control system (TBTC), and a switching unit. The CBTC and TBTC are respectively connected to the communication system via the switching unit. Under normal condition, the CBTC is connected to the communication system via the switching unit, and the function commands received by the train come from the CBTC. When the CBTC fails, the TBTC is connected to the communication system via the switching unit, and the function commands received by the train come from the TBTC. The switch between the CBTC and the TBTC is automatically executed by the system. Simulation results showed that the proposed design in this paper improved the availability of the signal system and reduced the impact of failures on operations.

Safe Operations at Roadway Junctions - Design Principles from Automated Guideway Transit

<div class="section abstract"><div class="htmlview paragraph">This paper describes a system-level view of a fully automated transit system comprising a fleet of automated vehicles (AVs) in driverless operation, each with an SAE level 4 Automated Driving System, along with its related safety infrastructure and other system equipment. This AV system-level control is compared to the automatic train control system used in automated guideway transit technology, particularly that of communications-based train control (CBTC). Drawing from the safety principles, analysis methods, and risk assessments of CBTC systems, comparable functional subsystem definitions are proposed for AV fleets in driverless operation. With the prospect of multiple AV fleets operating within a single automated mobility district, the criticality of protecting roadway junctions requires an approach like that of automated fixed-guideway transit systems, in which a guideway switch zone “interlocking” at each junction location deconflicts railway traffic, affirming safe passage. The analogous AV protection safety subsystem is defined as fail-safe equipment that monitors roadway intersections and junctions, communicates traffic signal status, perceives and communicates alerts and signals to AV connected vehicles concerning potential unsafe conditions, and performs related primary safety functions. Conclusions are drawn that the AV protection roadway intersection functions must be performed by local roadside equipment dedicated to protecting each roadway intersection and junction. Further, it is concluded that the communications technology connecting the infrastructure with the vehicle to perform this vital, fail-safe protection should meet specific functional and performance criteria.</div></div>

The Function Design for the Communication-Based Train Control (CBTC) System: How to Solve the Problems in the Underground Mine Rail Transportation?

With the continuous development of the mining industry, the world’s major mines have gradually entered the intelligent stage. In intelligent underground mines, the operation roads of the underground transportation equipment are very complicated, and the monitoring and control of the underground traffic have become the problems to be solved in the intelligent underground mines. Therefore, on the basis of solving the practical problems of underground mines, the concept paper discusses the possibility of the communication-based train control (CBTC) system being applied to underground mines through the summary and induction of the related literature. As mining engineers, we have proposed the function design for the CBTC system to solve the problems in underground mine rail transportation, but we still need to continue to work hard for the future development of the underground mines. The concept paper serves as a guide to the Tossing out a brick to get a jade gem, and it has implications for the development and the future of underground mine transportation.

Stackelberg Game-Based Radio Resource Management Algorithm in an Urban Rail Transit Communication System

Train-to-wayside (T2W) and train-to-train (T2T) communication modes may coexist in future train-centric communication-based train control (CBTC) systems. The feasibility of T2T communication in urban rail transit is analyzed first. Referring to the device-to-device (D2D) communication scenario in the general cellular network, this paper establishes a radio resource optimization model for the coexistence of train-to-train communication and train-to-wayside communication. With the aim of more efficient scheduling of radio time-frequency resources in the dedicated frequency band, we propose a Stackelberg game-based radio resource management algorithm based on the consideration of different service priorities of trains. The analysis and simulation results show that the proposed algorithm can effectively guarantee the performance of the system and improve the reliability of the CBTC system.

Engineering Project: The Method to Solve Practical Problems for the Monitoring and Control of Driver-Less Electric Transport Vehicles in the Underground Mines

With the continuous development of Artificial Intelligence technology and Internet of Things engineering, more and more driver-less vehicles have been developed and put into industrial production. The birth of driver-less vehicles undoubtedly brings new vitality to a large amount of industries, particularly in transportation. For the mining industry, transportation is undoubtedly an extremely important link in the whole production process. If the driver-less vehicles can be applied to the underground mines, it can not only improve the production and transportation capacity of the whole mine but also can reduce the occurrence of many mine safety accidents. ZigBee WSN technology can play a greater role in the narrow environment such as underground mines according to the relevant literature; this concept paper, similar to an engineering project plan, mainly tries to integrate the ZigBee WSN technology and the communication-based train control (CBTC) system to explore the possibility of the driver-less vehicles to be used in the underground mines, which aims to solve practical engineering problems for the engineering projects. As the mining engineers, we put forward the concept of this integrated system in this concept paper, but we need to continue to work hard for the future of the underground mines. This concept paper serves as a guide to Tossing out a brick to get a jade gem, and it has a few implications for the development of underground mine transportation.

An Intrusion Detection Method Based on Machine Learning and State Observer for Train-Ground Communication Systems

The communication-based train control (CBTC) system is a typical cyber physical system in urban rail transit. The train-ground communication system is a very important subsystem of the CBTC system and uses the wireless communication protocols to transmit control commands. However, it faces some potential information security risks. To ensure information security of the train-ground communication system, an intrusion detection method based on machine learning and state observer is proposed to detect and recognize various attacks in this paper. The detection system not only detects the anomalies of the wireless network data, but also detects the anomalies of the train physical states. This method includes two layers. The first layer is used to detect and identify wireless network attacks based on machine learning algorithms, such as the random forest algorithm and the gradient boosted decision tree algorithm. The second layer is used to detect the abnormal physical state of train operation based on a state observer. By combining the results of the above two layers, a comprehensive intrusion detection result is given. The simulation results show that the proposed method is effective and practical.

Advances in Computational Modeling of EMC/EMI Effects in Communication-Based Train Control (CBTC) Systems

Communication-based train control (CBTC) systems are aimed at providing control and signaling for rail transportation. These operate in environments that include tunnel and open-air sections, as well as busy stations, coexisting with Wi-Fi and cellular communication networks. Modeling electromagnetic compatibility and interference (EMC/EMI) issues in CBTC is most efficiently achieved by hybridizing several computational electromagnetic techniques rather than relying on a single one. This paper presents an overview of the applicable standards and some typical EMI scenarios for CBTC systems. Then, we discuss recent advances in hybridizing the vector parabolic equation (VPE) method, ray-tracing (RT) and the finite-difference time-domain (FDTD) technique, towards the efficient modeling of such scenarios.

A Novel Hierarchical Situation Awareness Model for CBTC Using SVD Entropy and GRU With PRD Algorithms

As a typical and special cyber-physical system, Communication-Based Train Control (CBTC) systems require a different security model from the traditional Information Technology(IT) systems. In this paper, we propose a novel hierarchical situation awareness model for CBTC systems. The two major characteristics of the model are that it can achieve rapid dimensionality reduction of multi-source heterogeneous data, and it can also deal with complex situation variations (such as hacker attacks) by learning, classifying and predicting critical data from the physical layer, network layer and application layer of CBTC systems. The Singular Value Decomposition (SVD) entropy algorithm and Gated Recurrent Unit (GRU) neural network with Progressive Residuals Detecting (PRD) algorithm are proposed to support our hierarchical model. When the singular value entropy threshold is set to 0.85, the SVD entropy algorithm can effectively compress the training and classification time by about 80% while keeping the classification accuracy stable. The mean absolute error between the observed Movement Authority (MA) value and the MA value predicted by the GRU algorithm is 23.96, which can be set as a threshold. Then the PRD algorithm is proposed to continuously calculate the progressive residuals between the two adjacent groups of observations and predictions, and only when the residuals of both two adjacent groups are greater than the threshold, the possible abnormal data can be detected. The denial of service (Dos) attack, Probing attack and data tampering attack are introduced to verify our hierarchical model and the simulation results demonstrate that our model can achieve real-time and precise system situation awareness and alerting.

Performance and Optimization of Outage Probability in CBTC Systems

The performance of two Access Points (APs) Communication-Based Train-Control (CBTC) systems subjected to an imperfect channel state information (CSI) scenario is investigated. More precisely, we first model the realistic small-scale fading distribution for which the receiver only has the outdated CSI due to the mobility of the train. We then derive the Outage Probability (OP) of the train and the ergodic capacity of the system in the closed-form expression based on the considered channel model. Additionally, we formulate an optimization problem that minimizes the maximal OP, which corresponds to the location of the train. For such, the signal-to-noise-ratio (SNR) is minimized as a function of the position of two APs. The pattern search method is utilized to solve the considered minimization problem. Numerical results confirm that by the optimal placement of the position of APs, the OP can be significantly ameliorated compared to the other placement methods. Furthermore, the numerical results also illustrate that the proposed solution completely coincides with the exhaustive search but with much less computation time. Finally, the mathematical framework is verified extensively by Monte Carlo simulations.

A Virtually Coupled Metro Train Platoon Control Approach Based on Model Predictive Control

In this paper, a virtually coupled train formation (VCTF) control method based on the model predictive control (MPC) framework is proposed. The train track spacing error, velocity error, and riding comfort are chosen as the optimization goals, and the constraints of line speed, collision avoidance of the train platoon, traction/braking performance, and string stability are considered. The virtual coupling operation control problem is converted into a quadratic programming problem with constraints. This paper also proposes a coasting control strategy to improve the output of the MPC controller. Simulation results show that compared with the proportional derivative controller, the proposed control method can simultaneously reduce the tracking error and output acceleration, reducing running energy consumption. A study of a metro line is chosen to analyze the VCTF operation performance, and the simulation results show that the VCTF operation mode can improve the peak capacity and quality of service of flat hours compared with the communication-based train control operation mode.

Tracking and collision avoidance of virtual coupling train control system

“Wash hands frequently, reduce aggregation, and wear masks” is an important measure for the prevention and control of the new crown pneumonia epidemic. Rail transit is the basic means of transportation to ensure the daily travel of citizens. Carriages and stations are both densely populated places. Reducing the density of carriages and platforms is an urgent problem for rail transit operations in the epidemic. Therefore, this paper proposes a method for dynamic marshalling of trains based on virtual coupling in a major epidemic situation, describes in detail the operation mode of virtual coupling trains, and establishes a marshalling planning model based on passenger flow to optimize the scheduling of virtual coupling trains to reduce passenger density at stations. Then, combined with the virus infection probability model and social force-based passenger movement model, the infection risk of the entire process of passenger subway travel under virtual coupling was analyzed. After that, Matlab was used to simulate the infection analysis under the virtual coupling system and compare it with the traditional communication based train control system. The risk of infection during the entire journey of a passenger on the subway is less than that of CBTC. Finally, according to the results of simulation analysis, effective measures can be given that can be used in conjunction with virtual coupling to reduce the risk of infection.