Moving Block System Research Articles

Modeling the Duration of the Impact of Unplanned Disruptions on Passenger Trips Using Smartcard Data in Urban Rail Systems

Many urban rail systems operate near capacity given the rapid increase in passenger demand, and unplanned disruptions are unavoidable. From a passenger perspective, the duration of trip delays is a major concern, and passenger trip delays may be longer than the train delays. Several studies have focused on predicting train delays, but the research on the duration of the disruption impacts on passenger trips is limited given that the duration is not observed directly. This paper proposes a probabilistic method to estimate the disruption impact duration using smartcard data, explores statistical and machine learning models to predict the duration of impacts on passengers, and identifies influencing factors including incident characteristics, operating conditions, infrastructure, external factors, and demand. The results highlight that prediction accuracies are acceptable for multiple linear regression, accelerated failure time, and random forest models. Disruptions caused by power failures have longer impact durations than other causes, followed by platform screen doors. The fixed block signaling system leads to a larger disruption duration than the moving block system. The study provides, for the first time, a data-driven approach to understanding the duration of the impact of disruptions on passenger trips using smartcard data which can facilitate timely and informed decision-making under unplanned disruptions.

Description and control of railway traffic flow under a moving block system

A moving block system (MBS) will contribute meaningfully to the railway. The advanced system can allow trains to operate closely as a platoon and significantly reduce train headway. Any minor speed disturbance of a train may lead to a chain of changes in operating status for some following trains in a platoon. However, any minor speed disturbance of a train may lead to a domino effect of changes in operating status for subsequent trains. This highlights the need for a thorough understanding of rail traffic flow behaviors under the MBS. Unfortunately, few studies have focused on this area. This study develops a micro-simulation model to describe train movements under MBS, and study in detail two typical railway operation scenarios: steep descending grade and arrival. On this basis, congestion phenomenon and bottleneck effect were explained in combination with the macroscopic rail fundamental diagram (RFD).Moreover, the strong controllability of trains and the predictability of shockwaves make it achievable and promising to control the rail traffic flow under the MBS. This study illustrates rail variable speed limit (RVSL) control in the RFD, and it dynamically provides trains with advisory speed limits to resolve delays and maintain a higher flow at bottlenecks. Two congestion scenarios are considered to evaluate its effectiveness, including the temporary excessive demand upstream of a descending grade and the arrival delay. The results demonstrate that the proper imposition of RVSL control reduces the number of affected trains, delay time, and energy consumption in both scenarios.

High-speed train cooperative control based on fractional-order sliding mode adaptive algorithm

PurposeThis study aims to propose an adaptive fractional-order sliding mode controller to solve the problem of train speed tracking control and position interval control under disturbance environment in moving block system, so as to improve the tracking efficiency and collision avoidance performance.Design/methodology/approachThe mathematical model of information interaction between trains is established based on algebraic graph theory, so that the train can obtain the state information of adjacent trains, and then realize the distributed cooperative control of each train. In the controller design, the sliding mode control and fractional calculus are combined to avoid the discontinuous switching phenomenon, so as to suppress the chattering of sliding mode control, and a parameter adaptive law is constructed to approximate the time-varying operating resistance coefficient.FindingsThe simulation results show that compared with proportional integral derivative (PID) control and ordinary sliding mode control, the control accuracy of the proposed algorithm in terms of speed is, respectively, improved by 25% and 75%. The error frequency and fluctuation range of the proposed algorithm are reduced in the position error control, the error value tends to 0, and the operation trend tends to be consistent. Therefore, the control method can improve the control accuracy of the system and prove that it has strong immunity.Originality/valueThe algorithm can reduce the influence of external interference in the actual operating environment, realize efficient and stable tracking of trains, and ensure the safety of train control.

Maximization of Energy Efficiency by Synchronizing the Speed of Trains on a Moving Block System

The publication deals with the problem of the effect of interference with the movement of the “preceding” train on the movement of the “following” train in the case of efforts to reduce the distance between trains on a moving block interval. The paper presents results of the simulations for train of the ED250 type for a set of 135 traffic situations: for three contexts of reducing the speed of the “preceding” train, for five variants of the method of controlling the “following” train and for nine initial distances between these trains. The results confirmed the possibility of gaining time and energy benefits by implementing an appropriate method of controlling the “following” train, as well as providing insights into the area of shortening the gaps between trains, including the pursuit of synchronizing the speed of trains and possibly coupling them into a so-called virtual couples.

Cooperative control for multiple train systems: Self-adjusting zones, collision avoidance and constraints

In practical multiple train systems, the desired relative positions of adjacent trains are usually not fixed values but some certain zones which are called “self-adjusting zones” in this paper. However, most of the existing related works were concerned about the case of fixed values and few works focused on the more practical case when the desired relative positions are some certain zones. The aim of this paper is to investigate cooperative control for multiple train systems under moving block system by taking into account self-adjusting zones, collision avoidance and constraints simultaneously, where each train needs not to coordinate with other trains in its desired self-adjusting zones and can be self-adjusted freely. A distributed cooperative control algorithm is proposed to enable all trains to track the desired velocity and operate steadily in their self-adjusting zones by only utilizing the local information of neighbor trains, where a switching mechanism is introduced to ensure the trains to avoid collision. The analysis is performed mainly based on the properties of stochastic matrices and multiple model transformations. It is shown that the braking process can be equivalent to a special coordination process, and the braking process, the coordination process and the self-adjusting process can be unified as an integrated whole to be analyzed by using the properties of stochastic matrices. By addressing the state interactions of the train equivalent system under different scenarios, it is proved that all relative positions of adjacent trains converge into desired self-adjusting zones without the occurrence of collision, while all trains finally move in a desired velocity. Numerical examples are included to illustrate the obtained results.

Comparing the Efficiency and Effectiveness of Different Train-Following Control Algorithms for Fleets of Heavy-Haul Freight Trains under Moving Blocks

With the nationwide installation of positive train control (PTC) technology recently completed, freight railroads are searching for ways to leverage the technology to improve their operations beyond increasing safety. One possibility is reducing train headways through developing and installing a PTC-based moving-block system, thus increasing the capacity of railroad mainlines without adding costly track infrastructure. Though operating trains at shorter headways can theoretically increase line capacity, effectively controlling following trains becomes more difficult compared with a fixed-block system, requiring a fast-reacting train crew or control algorithm that effectively minimizes headway and fuel consumption while attenuating all fluctuations in lead-train speed. Otherwise, rapid changes in throttle and brake settings may be required, reducing following-train fuel efficiency, generating in-train forces, and diminishing the expected capacity gains from shortened headways. This research, sponsored by the Federal Railroad Administration, aims to better understand how closely following freight trains respond to different throttle- and brake-control algorithms. Using insights from connected automobile and truck platooning technology, the project team developed several train-following control algorithms, analyzed their stability, and simulated their performance with fleets of freight trains subject to different speed profiles. While moving-block systems do require additional train spacing beyond the minimum safe braking distance to account for train control actions, effective train-following control algorithms can minimize this distance. Also, the developed control laws exhibit a trade-off between minimizing train headway and fuel consumption, potentially allowing railway operators to choose an optimal balance.

Impact of signalling system on capacity – Comparing legacy ATC, ETCS level 2 and ETCS hybrid level 3 systems

Most railways use fixed block technology, which could be replaced with moving block technology with associated high cost. It is therefore interesting to gradually upgrade the signalling system exploiting hybrid technologies. This paper aims to investigate the impact on capacity of various signalling systems (including fixed block technology and hybrid technology) using a microscopic simulation tool under scheduled (static) conditions without considering probability functions. To perform comparative analysis between European Train Control System (ETCS) Hybrid Level 3, ETCS Level 2, and the Swedish ATC2 legacy system, three signalling system scenarios are designed and capacity consumption is considered as a performance indicator. The study was performed on the central section of Stockholm's commuter train network with peak hour conditions from the 2020 timetable. The results show that ETCS L2 delivers lower capacity consumption in total compared to the ATC2 legacy system. ETCS Hybrid Level 3 with existing trackside train detection and partially shortened block sections delivers lower capacity consumption compared to ETCS L2 and ATC2. The implementation of hybrid solutions such as ETCS Hybrid Level 3 in addition to allowing for gradual upgrading of signalling systems to the next generation (moving block system) can improve capacity of high-density commuter lines.

Timetable optimization for a moving block system

We present an optimization model which is capable of routing and ordering trains on a microscopic level under a moving block regime. Based on a general timetabling definition (GTTP) that allows the plug in of arbitrarily detailed methods to compute running and headway times, we describe a layered graph approach using velocity expansion, and develop a mixed integer linear programming formulation. Finally, we present promising results for a German corridor scenario with mixed traffic, indicating that applying branch-and-cut to our model can solve reasonably sized instances with up to a hundred trains to optimality.

Cooperative control for multiple high‐speed trains with constraints and acceleration zone under moving block system

ABSTRACTThis article investigates a cooperative control problem with acceleration zone and constraints for multiple high‐speed trains under moving block system. A distributed cooperative control algorithm is proposed where a switching mechanism and acceleration zone are introduced to reduce the cost of the operation adjustment and the communication between trains. Based on the properties of stochastic matrices, by selecting proper control parameters and applying the approach of model transformation and convex analysis, it is shown that the cooperative control problem can be solved if the communication topology has directed spanning trees. Finally, a numerical example is included to illustrate the obtained results.

High-Speed Train Platoon Dynamic Interval Optimization Based on Resilience Adjustment Strategy

Resilience adjustment refers to the generation of a control strategy by evaluating the interaction between related factors. Tracking intervals of the high-speed train platoon change dynamically, which directly influences the operation safety and efficiency, and constrains the train operation trajectories. In China, the tracking interval is getting shorter. To ensure safety and improve efficiency, we research a dynamic interval resilience adjustment strategy based on the moving block system. Firstly, the optimal offline operation strategy is obtained by solving the multi-objective optimization model with the improved gravitational search algorithm (I-GSA). The resilience adjustment mechanism is developed to evaluate the tracking interval and choose the appropriate driving strategy to adjust operation states based on the resilience tracking interval model. Then, we study the relation between operation strategy and departure interval, and a seeker optimization algorithm (SOA) is used to obtain the optimal departure intervals and driving strategies. Simulations are conducted based on the sections between Chibi North station and Changsha South station in Wuhan-Guangzhou high-speed railway. The results indicate that the total operation time decreased by 191s and the operation safety can be ensured at any time.

Research on Virtual Coupling Train Operations Based on Moving-Block and Vehicle-to-Vehicle Communication

This paper introduces the current research status of train operation mode especially the one based on the train moving-block system. Then it improves on the basis of the Vehicle-to-Ground(V2G) communication technology and the traditional fixed-block system constructs a virtual combination model based on the train moving-block system and Vehicle-to-Vehicle(V2V) communication technology. Through the construction of state flow-diagram of the entering and leaving the Virtual Coupling train-following model and calculation of the train capacity, discussion and analysis are carried out in different scenarios, including train tracking at the station, arriving at the station, sending out from the station, etc. Finally, the scene of two trains tracking through the station is simulated and compared with the traditional fixed-block operation mode in ideal circumstances. The results show that the new operation mode proposed in this paper can improve the railway capacity and train operation efficiency. In the future railway development, this kind of operation mode has certain efficiency.

Train delay propagation under random interference on high-speed rail network

To simulate passenger train movements on the high-speed rail network, this paper proposes a new dynamic model based on the discrete time method and provides some efficient control policies correspondingly. Besides that, an improved minimum safe headway in the moving-block system on the high-speed rail network is presented. Using the proposed method, the dynamic characteristics of railway traffic flow are analyzed under random interferences on the high-speed rail network. Then, some sensitivity analyses are implemented to investigate the propagation features of delays under different interferences. The results indicate that the proposed dynamic model and control policies for the passenger train movements on the high-speed rail network are effective and can be a fundamental research for subsequent research of delay propagation, rerouting and rescheduling problems.

A Model Predictive Control Approach for Virtual Coupling in Railways

This paper presents a novel approach in train control systems based on the concept called virtual coupling or train convoys. This approach follows the recent developments in the field of safe platooning of autonomous vehicles. We use a decentralized model predictive control (MPC) framework for each train participating in a convoy formation. Control designs for the leading and following trains are presented. An optimal control formulation for both controllers is used and its design relies on a numeric solution of a finite horizon optimal control problem. This paper compares the proposed method with alternative control strategies including the well-studied moving block train control concept. A study of a metro line has been chosen as a first analysis for this control approach. The simulation results for this kind of railway lines demonstrate better performance and the benefits of this new concept versus the moving block system. We show that the virtual coupling concept substantially reduces headway and distance between trains while guaranteeing safe separation between two consecutive trains at any instant.

Distributed cooperative control of multiple high-speed trains under a moving block system by nonlinear mapping-based feedback

Although the high-speed railways in China have been greatly advanced in the past decades with respect to expanding networks and increasing speed, a fixed block system, which separates the trains with several stationary track block sections, is utilized to guarantee the safe operation of multiple trains. A moving block system, which enables the moving authority of a high-speed train to be the real-time positioning point of its preceding one (plus some necessary safe redundant distance, of course), is under development to further make full use of the high-speed railway lines and improve the automation level by automatic train operation for high-speed trains. The aim of this paper is to design a distributed cooperative control for high-speed trains under a moving block system by giving a cooperative model with a back-fence communication topology. A nonlinear mapping-based feedback control method together with a rigorous mathematic proof for the global stability and ultimate bound of the closed-loop control systems is proposed. Comparative results are given to demonstrate the effectiveness and advantages of the proposed method.

Optimization for the Following Operation of a High-Speed Train Under the Moving Block System

Efficient and safe following operation of a high-speed train (HST) under the moving block system (MBS) has been the trend for high-speed railway (HSR) transportation. However, due to the complex operating environment and changeable operation state of HST during the following operation process, it becomes inapplicable for conventional train control approaches to satisfy HST’s multi-objective operation demand including safety, punctuality, energy efficiency, and ride comfort. To resolve this problem, in this paper, practical models for the real-world characteristics of HSR’s line parameters and HST’s following control, as well as the multi-objective optimization model with some novel metrics, are established for achieving the optimal following control of HST under MBS. Besides, the multi-objective particle swarm optimization algorithm is modified with the preference information of control sensitivity and energy efficiency, so as to efficiently obtain the optimal following control strategy based on the real-time data of HST like velocity, location, and speed restriction. Furthermore, the convergence performance of our proposed method is demonstrated by comparative tests which also help select the proper algorithm parameters. Finally, the efficiency and feasibility of the proposed framework are illustrated by showing some experimental results.

A New Calibration Method for the Real-Time Calculation of Dynamic Safety Following Distance under Railway Moving Block System

Only the actual following distance that is a little greater than the optimum safety following distance at any time can make the following train move in safety and efficiency. For this purpose, a new calibration method is studied for the real-time calculation of the dynamically optimum safety following distance. To cope with the complex situations of train following operation, the mathematic model of train deceleration operation based on the hyperbolic function with a variable acceleration control strategy is established to simulate the speed-changing behavior of high-speed train steered by the well-experienced driver. Using the evaluation of train behavior adjustment quality and the numerical analysis theory, we build the fitting function of the optimum absolute safety following distance changing with the following train’s velocity for the real-time calibration of safe following distance under absolute braking mode. And then, we discussed the real-time calculation of the optimum safety following distance under relative braking mode (i.e., the relative safety following distance). The study results will help a high-speed train to evaluate and optimize its own following behavior according to the current operation states of train following system, the actual following distance, and the absolute or relative safety following distance. The actual following distance is rationally controlled by the scientific adjustment of the following train’s behavior so that train following movement can be always safe, efficient, and smooth (comfortable).

Research on Signal Control System of Urban Rail Transit Based on Communication Technology

Moving block system is one of the applied technologies of signal system of urban rail transit, which is usually realized by train control technology based on communication. In this paper, the basic principle, system structure and realization of mobile block system are discussed systematically.

Optimization of the geometry and speed of a moving blocker system for cone-beam computed tomography scatter correction.

X-ray scatter is a significant barrier to image quality improvements in cone-beam computed tomography (CBCT). A moving blocker-based strategy was previously proposed to simultaneously estimate scatter and reconstruct the complete volume within the field of view (FOV) from a single CBCT scan. A blocker consisting of lead stripes is inserted between the X-ray source and the imaging object, and moves back and forth along the rotation axis during gantry rotation. While promising results were obtained in our previous studies, the geometric design and moving speed of the blocker were set empirically. The goal of this work is to optimize the geometry and speed of the moving block system. Performance of the blocker was examined through Monte Carlo (MC) simulation and experimental studies with various geometry designs and moving speeds. All hypothetical designs employed an anthropomorphic pelvic phantom. The scatter estimation accuracy was quantified by using lead stripes ranging from 5 to 100 pixels on the detector plane. An iterative reconstruction based on total variation minimization was used to reconstruct CBCT images from unblocked projection data after scatter correction. The reconstructed image was evaluated under various combinations of lead strip width and interspace (ranging from 10 to 60 pixels) and different moving speed (ranging from 1 to 30 pixels per projection). MC simulation showed that the scatter estimation error varied from 0.8% to 5.8%. Phantom experiment showed that CT number error in the reconstructed CBCT images varied from 13 to 35. Highest reconstruction accuracy was achieved when the strip width was 20 pixels and interspace was 60 pixels and the moving speed was 15 pixels per projection. Scatter estimation can be achieved in a large range of lead strip width and interspace combinations. The moving speed does not have a very strong effect on reconstruction result if it is above 5 pixels per projection. Geometry design of the blocker affected image reconstruction accuracy more. The optimal geometry of the blocker has a strip width of 20 pixels and an interspace three times the strip width, which means 25% detector is covered by the blocker, while the optimal moving speed is 15 pixels per projection.

Train flow chaos analysis based on an improved cellular automata model

To control the chaos in the railway traffic flow and offer valuable information for the dispatchers of the railway system, an improved cellular model is presented to detect and analyze the chaos in the traffic flow. We first introduce the working mechanism of moving block system, analyzing the train flow movement characteristics. Then we improve the cellular model on the evolution rules to adjust the train flow movement. We give the train operation steps from three cases: the trains running on a railway section, a train will arrive in a station and a train will departure from a station. We simulate 4 trains to run on a high speed section fixed with moving block system and record the distances between the neighbor trains and draw the Poincare section to analyze the chaos in the train operation. It is concluded that there is not only chaos but order in the train operation system with moving blocking system and they can interconvert to each other. The findings have the potential value in train dispatching system construction and offer supporting information for the daily dispatching work.

The Study on Urban Rail Transit Train Operation Simulation System Based on Timetable Control

This paper establishes a modular urban rail transit train operation simulation system through the application of the train dynamic model, train tracking model in moving block system and timetable in train operation simulation. Then the framework and simulation process of simulation system are designed. Train operation simulation module, data management module and graphical display module make up the simulation system. Based on the structure and working principle of the Communication Based Train Control (CBTC), the key functions of train operation control simulation are specifically design. Finally the Line 4 of Beijing Subway is taken as a simulation example.