Urban Train Research Articles

A cooperative evacuation strategy for mass passenger flow in urban rail transit transfer stations

In reviewing the evacuation problem of mass passenger flow in urban rail transit transfer stations, the cooperative evacuation strategy considering urban rail transit and emergency bus simultaneously is found to be an efficient way. In this work, firstly, the dynamic characteristics of mass passenger flow are analyzed based on the abstraction and simplification of major entities of urban rail transit, including passengers, stations and trains. Then, the operations of the urban rail transit system are modeled, including the boarding, landing and transferring processes of the passengers and the status updating flows of the trains and stations. To realize the cooperative evacuation, a multi-objective optimization model considering the evacuation speed, the number of passengers transferred, and the amount of emergency buses is proposed. The NSGA-II algorithm is adopted to solve the proposed model, which can balance the theoretical validity and computational convenience. Last, the proposed strategy is applied in a real-life case based on the Shanghai Metro line, and the results verify its effectiveness and efficiency.

Research on Synchronverter-Based Regenerative Braking Energy Feedback System of Urban Rail Transit

Generally running with frequent braking over short distances, the urban rail transit train generates great quantities of regenerative braking energy (RBE). The RBE feedback system can effectively recycle RBE and give it back to the AC grid. However, the lack of damp and inertia of generators makes conventional PWM RBE feedback system more sensitive to power fluctuations. To address this issue, a synchronverter-based RBE feedback system of urban rail transit is designed in this paper. First, the structure of the feedback system is presented. Then, the synchronverter-based control strategy with greater flexibility and higher stability is fully discussed. Furthermore, the parameter design of the system is analyzed in detail. Finally, simulation results and experimental results are provided to show the good dynamic performance of the system. Using this synchronverter-based approach, the system supplies traction power to the traction network when the train accelerates and gives the RBE back to the AC grid when the train brakes, in light of the variation of the DC bus voltage. Moreover, the system can be self-synchronized with the AC grid and make corresponding power management on the basis of changes in the voltage amplitude as well as the frequency of the grid. In this sense, the RBE feedback system becomes more flexible, effective and robust.

Research on the Utilization of Metro Regenerative Braking Energy Based on an Improved Differential Evolution Algorithm

Urban metro trains have the characteristics of short running distance between stations and frequent starting and braking. A large amount of regenerative braking energy is generated during the braking process. The effective utilization of the regenerative braking energy can substantially reduce the total energy consumption of train operation. In this paper, we establish two integer programming models of train operation that maximize the overlap time between train traction and braking in peak hours and nonpeak hours. On this basis, an improved differential evolution (IDE) algorithm is developed for solving the two integer programming models. The results demonstrate that the overlap time increases by 51.44% after optimization using the IDE algorithm when the headway is set to 154 s in peak hours. The overlap time is further increased by 14.87% by optimizing the headway. In nonpeak hours, the overlap time of traction and braking of the trains in opposite directions at the same station is increased by optimizing the bidirectional departure interval, thereby reducing the total energy consumption of the system.

A novel modular designing for multi-ring flywheel rotor to optimize energy consumption in light metro trains

Abstract In this paper, a multi-ring flywheel rotor is chosen as a basic module for modular designing an optimized energy storage system to reduce the energy consumption in light metro trains by finding the best capacity and the number of optimized-flywheel rotor module for each train car. After finding the adequate capacity and optimizing the geometric characteristics of rotor rings, the effect of using the modular Flywheel energy storage system (FESS) on reducing the energy consumption of light urban trains is investigated. Four different rotors with various energy storage capacities are chosen, so that results can be used for a wide range of light trains with a power demand range of 1620–3420 kW. In the optimization algorithm, the energy per unit volume is considered as the cost function. The presented general modular designing is examined for Shiraz urban train system by using real-time speed and acceleration data. A three-layer flywheel with an energy storage capacity of 500W.h serves as a practical example. Finally, the effects of the number of passengers, peak, and off-peak hours in the energy storage capacity of the system are also studied. Using 15-FESS modules results in 35.1% energy saving for this line.

Investigating Market Potentials and Operational Scenarios of Virtual Coupling Railway Signaling

The new concept of virtual coupling (VC) envisages autonomous trains running in radio-connected platoons to significantly improve railway capacity and address the forecasted increase in railway demand. Such a concept will introduce radical changes to current train services, technologies, and procedures, which calls for a deeper understanding of the possible modes of operation and the impacts on the entire railway business. This paper investigates market potentials and operational scenarios of VC for different segments of the railway market: high-speed, main-line, regional, urban, and freight trains. The research builds on the Delphi method, with an extensive survey to collect expert opinions about benefits and challenges of VC as well as stated travel preferences in futuristic VC applications. Survey outcomes show that VC train operations can be very attractive to customers of the high-speed, main-line, and regional market segments, with benefits that are especially relevant for freight railways. In particular, customers of regional and freight railways are observed to be unsatisfied with current train services and willing to pay higher fares to avail of a more frequent and flexible service enabled by VC. Operational scenarios for VC are then defined by setting market-attractive service headways and by characteristics of the rolling stock, infrastructure, and traffic management. An analysis of strengths and weaknesses of such a concept together with business opportunities and threats is carried out. The defined VC future scenario is set to induce a sustainable shift of customers from other travel modes to the railways.

Riding Comfort Evaluation Based on Longitudinal Acceleration for Urban Rail Transit—Mathematical Models and Experiments in Beijing Subway

Riding comfort is an important index to measure the quality of service for railways, especially for congested urban rail transit systems where the majority of passengers cannot find a seat. Existing studies usually employ the value of longitudinal acceleration as the key indicator to evaluate the riding comfort of vehicles, while there is no validated mathematical models to evaluate the riding comfort of urban rail trains from the perspective of passengers. This paper aims to employ the collected longitudinal acceleration data and passengers’ feedback data in Beijing subway to qualitatively measure and validate the riding comfort of transit trains. First, we develop four regular fuzzy sets based comfort measurement models, where the parameters of the fuzzy sets are determined by experiences of domain experts and the field data. Then a combinational model is given by averaging the four regular fuzzy set models to elaborate a comprehensive measurement for the riding comfort. In order to verify the developed models, we conducted a questionnaire survey in Beijing subway. The surveyed riding comfort data from passengers and the measured acceleration data are used to validate and optimize the proposed models. Two key parameters are deduced to describe all parameters in the fuzzy set models and a meta-heuristic algorithm is applied to optimize the parameters and weight coefficients of the combinational model. Comparing the collected comfort data with the comfort levels and values calculated by different models shows that the averaging model is better than any regular fuzzy set model. Furthermore, the optimized model is better than the averaging model and provides the best accuracy and robustness for riding comfort measurement. The models provided in this paper offer an optional way to measure the riding comfort for further assessment and more comprehensively tuning of train control systems.

Research on Energy-saving Operation Optimization of Urban Rail Transit Trains

In order to better realize the energy saving operation of urban rail transit trains, considering the use of regenerative braking energy has become the focus of current academic research. Train timetable optimization, energy storage system recovery, and inverter system feedback are the main technical means to achieve it. At present, train operation chart optimization is mainly divided into static timetable optimization and dynamic timetable optimization. The energy storage system recovery includes super capacitor type, battery type and flywheel type energy storage device. This paper introduces three technical methods based on the use of regenerative braking energy, and compares the advantages and disadvantages of different energy storage and recovery devices, and finally come to a conclusion.

Urban Rail Transit Energy Storage Based on Regenerative Braking Energy Utilization

In order to better realize the energy-saving operation of urban rail transit trains, considering the use of regenerative braking energy has become the focus of current academic research. Train operation chart optimization, energy storage system recovery, and inverter system feedback are the main technical means for its implementation. At present, the recovery of energy storage systems includes super capacitor type, battery type, and flywheel type energy storage devices. This paper focuses on the urban rail transit energy storage recycling method based on the utilization of regenerative braking energy, studies the basic working principle of the energy storage recovery device, and analyzes the different energy storage and recovery devices, and draws conclusions through comparison.

A Highly Reliable Propulsion System with Onboard Uninterruptible Power Supply for Train Application: Topology and Control

Providing uninterrupted electricity service aboard the urban trains is of vital importance not only for reliable signaling and accurate traffic management but also for ensuring the safety of passengers and supplying emergency equipment such as lighting and signage systems. Hence, to alleviate power shortages caused by power transmission failures while the uninterruptible power supplies installed in the railway stations are not available, this paper suggests an innovative traction drive topology which is equipped by an onboard hybrid energy storage system for railway vehicles. Besides, to limit currents magnitudes and voltages variations of the feeder during train acceleration and to recuperate braking energy during train deceleration, an energy management strategy is presented. Moreover, a new optimal model predictive method is developed to control the currents of converters and storages as well as the speeds of the two open-end-windings permanent-magnet-synchronous-machines in the intended modular drive, under their constraints. Although to improve control dynamic performance, the control laws are designed as a set of piecewise affine functions from the control signals based on an offline procedure, the controller can still withstand real-time non-measurable disturbances. The effectiveness of proposed multifunctional propulsion topology and the feasibility of the designed controller are demonstrated by simulation and experimental results.

Fuzzy control strategy for a compound energy system for an urban rail train based on the required power

Abstract In this paper, a fuzzy energy control method with multiple inputs is proposed that considers the power demand of the system. It targets the problem of the power distribution of the combined power supply of the supercapacitor and lithium battery in composite energy storage systems of urban rail trains. The composite energy control system is modeled and simulated by using the required power of the train, the state of charge for lithium battery and supercapacitor as the inputs and the power distribution coefficient of the lithium battery as the output in the fuzzy controller. Simulation results show that the fuzzy controller can distribute energy well, satisfy the power demand of real train operation, reduce the impact of large current on the lithium battery, and improve the cycle utilization times of the lithium battery, which is conducive to improving the stability and comfort of train operation.

Research on the Handoff for Urban Rail Transit Based on IGM-BP Algorithm

Aiming at the problem that the reference signal received power (RSRP) value received by the urban rail transit train during the handoff fluctuates greatly, which causes frequent occurrence of ping-pong handoff, combined with the A3 event in the TD-LTE standard, the improved grey prediction-BP neural network (IGM-BP) algorithm was proposed to improve RSRP fluctuations. The terminal access unit (TAU) will receive the first four sets of RSRP values at time t to establish a grey model GM (1,1) and get a set of predicted values. Take the average of the predicted value as the expected value, and finally the predicted values, modified by the BP neural network algorithm, are used to obtain the expected RSRP value. The simulation results show that the proposed algorithm, compared with the traditional handoff algorithm and the grey prediction algorithm, decreases the RSRP value fluctuation range, reduces the ping-pong handoff rate and meets the requirement that the TD-LTE system handoff success rate reaches 99.5%.

Characterization of particulate matter emissions in urban train braking - An investigation of braking conditions influence on a reduced-scale device.

The particulate matter emissions related to the braking of railway rolling stock are investigated using a reduced scale braking device. Samples of organic materials and cast iron discs are tested for different nominal contact pressures and disc surface temperatures, representative of real conditions. The aim of this work is to investigate the influence of braking conditions on the global amount of particles emitted, their distribution in number and size, and their morphological and chemical characteristics. To be representative, the tested conditions are designed to dissipate the same amount of energy for all the braking events by adjusting the pad application duration. The results show that for the same dissipated energy, a temperature increase above a transition value in the range of 230-280 ∘C depending on the braking conditions modifies the size and number distributions of the generated particles. The results obtained are of interest to better represent their propagation through CFD modelling according to the characteristic of the particle emission.

Fuzzy Decentralized Controller Design with Internet of Things for Urban Trains

Due to the dynamic structure and physical constraints that exist in controlling the urban train system, the physical parameters of the urban train model are constantly changing, and therefore a static controller cannot fully control all of the control objectives to be defined. In this paper, a new method of using a PID controller based on fuzzy control with considering the uncertainty of the weight of the dynamic model of the system is presented for managing the dynamical model of the urban train. The primary objective of this research work is to provide a structure that simultaneously, in addition to guaranteeing the stability of the Kharitonov polynomials, the dynamic model of the sample system also automatically adjusts and controls the proposed controller control parameters. In order to introduce model uncertainties into the controller design calculations, Kharitonov polynomials related to the open loop conversion function are first extracted. Then the feedback loop is constructed with a parallel PID controller, and by rewriting the closed-loop conversion function equations, we obtain the set of all closed-loop system transformation functions, in which the model's indices are also considered. Subsequently, by examining the stability ranges of all closed-loop functions, the values obtained for the proportional, integral, and derivative parameters of the PID controller are obtained for its robust performance. Finally, a fuzzy-based structure is proposed for intelligent operation and online adjustment of proposed PID controller coefficients. Further, this research work outlines twolevel Internet of Things (IoT) sensor network that compliments the proposed mathematical model by providing real-time model parameters using the sensory information.

Speed Calibration and Traceability for Train-Borne 24 GHz Continuous-Wave Doppler Radar Sensor

The 24 GHz continuous-wave (CW) Doppler radar sensor (DRS) is widely used for measuring the instantaneous speed of moving objects by using a non-contact approach, and has begun to be used in train-borne movable speed measurements in recent years in China because of its advanced performance. The architecture and working principle of train-borne DRSs with different structures including single-channel DRSs used for freight train speed measurements in railway freight dedicated lines and dual-channel DRSs used for speed measurements of high-speed and urban rail trains in railway passenger dedicated lines, are first introduced. Then, the disadvantages of two traditional speed calibration methods for train-borne DRS are described, and a new speed calibration method based on the Doppler shift signal simulation by imposing a signal modulation on the incident CW microwave signal is proposed. A 24 GHz CW radar target simulation system for a train-borne DRS was specifically realized to verify the proposed speed calibration method for a train-borne DRS, and traceability and performance evaluation on simulated speed were taken into account. The simulated speed range of the simulation system was up to (5~500) km/h when the simulated incident angle range was within the range of (45 ± 8)°, and the maximum permissible error (MPE) of the simulated speed was ±0.05 km/h. Finally, the calibration and uncertainty evaluation results of two typical train-borne dual-channel DRS samples validated the effectiveness and feasibility of the proposed speed calibration approach for a train-borne DRS with full range in the laboratory as well as in the field.

Automated urban train control with hybrid Event-B: ‘Tackling’ the rugby club problem

Normally, the passengers on urban rail systems remain fairly stationary, allowing for a relatively straightforward approach to controlling the dynamics of the system, based on the total rest mass of the train and passengers. However, when a mischievous rugby club board an empty train and then run and jump-stop during the braking process, they can disrupt the automatic mechanisms for aligning train and platform doors. This is the Rugby Club Problem for automated urban train control. A simple scenario of this kind is modelled in Hybrid Event-B, and sufficient conditions are derived for the prevention of the overshoot caused by the jump-stop. The challenges of making the model more realistic are discussed, and a strategy for dealing with the Rugby Club Problem, when it cannot be prevented, is contemplated. • Considers unruly behaviour by a rugby club on urban rail. • Addresses the issue via Newtonian mechanics. • Formalises the solution using Hybrid Event-B. • Considers uncertainty aspects.

Evaluation and Optimization of the Effective Parameters on the Shield TBM Performance: Torque and Thrust—Using Discrete Element Method (DEM)

Cutterhead torque and thrust are the two main designing parameters of the shield TBM, which have to be evaluated and optimized, based on the interaction between the TBM and excavated material. This study employs the discrete element method (DEM) to simulate the tunneling procedure of the line-7 of Tehran underground urban train tunnel utilizing the micro mechanical parameters calculated from back analysis on direct shear tests. The resultant torque and thrust are then compared against the actual parameters and then with those estimated from the numerical analyses. This result shows that DEM is able to estimate the TBM torque and thrust applying actual boundary conditions and material properties for the model. Furthermore, the impact of ground properties, overburden height, linear and radial velocity on cutterhead torque and thrust and its performance are evaluated and optimized.

Energy management strategy of hybrid energy storage system for urban rail trains

Energy management strategy of hybrid energy storage system for urban rail trains

Ultracapacitor Energy Storage Systems based on Dynamic Setting and Coordinated Control for Urban Trains

The supply voltage of traction systems fluctuates frequently due to acceleration and braking during urban rail train running process. In order to achieve better performance for ultracapacitor energy storage systems, a bilateral ultracapacitor energy storage system structure is adopted, and a method based on dynamic setting and coordination is proposed, in which the charge and discharge voltage thresholds of ultracapacitors are dynamically set and the energy flows are coordinated controlled between the bilateral ultracapacitor energy storage systems. The simulation results show that the proposed control strategy can achieve good energy-saving effect and stabilize the traction network voltage under the premise of balanced use of the ultracapacitor energy storage systems.

Predictive Control Algorithm for Urban Rail Train Brake Control System Based on T-S Fuzzy Model

Predictive Control Algorithm for Urban Rail Train Brake Control System Based on T-S Fuzzy Model

Electric load forecast of long-period rail transit based on fuzzy mathematics

The urban rail transit power supply system is an important part of the urban power distribution network and the power source of the rail transit system. It is responsible for providing safe and reliable electrical energy to urban rail trains and power lighting equipment. This paper processes the obtained long-period rail transit power load learning sample data matrix, according to the principle of normalization processing, effectively eliminates irregular data in the sample set and fills in possible missing data, thereby eliminating bad data or fake data for model learning. Moreover, this avoids the generation of huge errors that cause exponential growth in the model due to the increase in the learning sample size and the irregularity of the data. According to the characteristics of power load, this paper comprehensively considers the influence of temperature and date type on the maximum daily load, applies the fuzzy neural network model to the long-period load forecasting of long-period rail transit, and introduces the whole process of establishing the forecasting model in detail. Through detailed analysis of the actual data provided by the EUNITE network, the relevant factors affecting the daily maximum load were determined, and then the appropriate fuzzy input was selected to establish the corresponding fuzzy neural network prediction model, and a relatively ideal prediction result was obtained. The experimental results fully proved the great potential of fuzzy neural network in long-term power load forecasting.