High-speed Railway System Research Articles

Comparing China's urban systems in high-speed railway and airline networks

Although the Chinese high-speed railway (HSR) entered the transportation market at a late stage in 2003, its networks have become the world's largest and are currently even growing faster than airline networks. Using the 2013 origin/destination (O/D) passenger flow data instead of commonly used scheduled data, we compare the spatial configurations of the Chinese national urban system in both high-speed railway and airline networks. The results show that HSR-dominant cities and links are located mainly in the middle and eastern parts of China, offering regional connections, whereas air-dominant cities and links are evenly distributed across the whole of China and predominantly offer interregional connections. This is mainly because HSR networks are more focused on connections to cities with high socio-economic performance and are more restricted by the geographical distance between linked cities than the airline networks. Furthermore, HSR networks promote agglomeration economies within cities located along the trunk lines in specific regions, whereas airline networks contribute to more balanced urban development in China. These dimensions indicate that the configuration of urban systems in HSR networks differ largely from that of air networks when measured in terms of passenger flows.

Dual-Connectivity Prevenient Handover Scheme in Control/User-Plane Split Networks

A control/user (C/U) plane-split network, where macro- and microevolved Node Bs (eNBs) are responsible for C/U-planes, respectively, is a potential 5G solution to address the problems experienced by high-speed railway communication systems such as frequent handovers (HOs), low system capacity, and low data rate. The C-plane transition occurs during an intermacro eNB HO to reduce the frequency of HOs. However, the intermacro-eNB HO in a C/U-plane-split network is prone to handover failures (HOFs) and long service interruption time similar to the traditional long-term evolution-advanced (LTE-A) HO without improvements because it is similar to an LTE-A HO between macro-eNBs from the perspective of C-plane transition. In this paper, we realize a C/U-plane-split network using the LTE-A dual-connectivity (DC) technique and propose a dc-based prevenient HO (PHO) scheme to improve the robustness of the intermacro-eNB HO. The proposed scheme specifically is an a priori method and uses the transmit diversity based on the dc technique to reduce the risk of HOFs and the long service interruption time. Further, we first develop the analytical expressions for HO performance for PHO and LTE-A HO, where HOFs are aligned with the LTE-A specifications such that they are defined as the association between the radio link monitor and HO processes. The analytical results are verified against simulation results. Through simulations, we compare PHO with LTE-A HO and the representative schemes of the previous literature in a variety of mobility performance metrics (such as the averages of the successful HO rate, the HOF rate, the radio link failure rate, the ping-pong rate, and the service interrupt time). The results confirm that the proposed scheme achieves superior performance in the key metrics of the successful HO rate and service interrupt time.

Energy storage systems to exploit regenerative braking in DC railway systems: Different approaches to improve efficiency of modern high-speed trains

The growing attention to environmental sustainability of transport systems made necessary to investigate the possibility of energy optimization even in sectors typically characterised by an already high level of sustainability, as in particular the railway system. One of the most promising opportunity is the optimization of the braking energy recovery, which has been already considered in tramway systems, while it is traditionally overlooked for high-speed railway systems. In this research work, the authors have developed two simulation models able to reproduce the behavior of high-speed trains when entering in a railway node, and to analyze the impact of regenerative braking in DC railway systems, including usage of energy storage systems. These models, developed respectively in the Matlab-Simscape environment and in the open source Modelica language, have been experimentally validated considering an Italian high-speed train. After validation, the authors have performed a feasibility analysis considering the use of stationary and on-board storage systems, also by taking into account capital costs of the investment and annual energy saving, to evaluate cost-effectiveness of the different solutions. The analysis has shown the possibility to improve the efficiency of high-speed railway systems, by improving braking energy recovery through the installation of such storage systems.

Effects of uncertain characteristic periods of ground motions on seismic vulnerabilities of a continuous track–bridge system of high-speed railway

The high-speed railway in China has to pass through the site surrounded by several known faults. Different earthquake mechanics of those faults and propagation paths cause different ground motions, including different peak ground accelerations (PGA), durations and characteristic periods, acting on the high-speed railway bridges. However, the previous seismic vulnerability analysis mainly aimed at the influence of PGA instead of characteristic periods on the seismic fragilities of bridge structure rather than track–bridge system. By taking a typical and common continuous bridge recommended in Chinese criterion as example, the effects of the uncertain characteristic periods of ground motions on the seismic responses and fragilities of track–bridge system were analyzed based on a numerical method. The results indicate that the probabilities exceeding any damage state of most components, including the bridge and track parts, increase with the characteristic period of ground motions. The uncertain characteristic periods of ground motions should be fully considered for the seismic design of track–bridge system, especially when the uncertain characteristic periods change around a small value. In the seismic vulnerability analysis, the uncertain of the designed characteristic period of ground motions should be developed by considering the different earthquake mechanics of several known faults surrounding the bridge site and the complex propagation paths of ground motion waves through different soils. Using a constant characteristic period of ground motions only considering the soil profile at the local site of bridge possibly leads to an unsafe result in the current criterion.

Failure analysis and optimization of integral droppers used in high speed railway catenary system

Abstract In this paper, the premature failure of the integral droppers in high speed railway catenary in China was investigated. Series of microscopic characterization and analysis were conducted to identify the root causes of the unexpected failure. By numerically simulating the existing crimping behavior, distribution of the contact stress in the dropper was obtained. It was found that there was stress concentration at the dropper sliced end, which became the primary reason for the permanent distortion and damage on the droppers, and consequently resulted in the untimely final fracture with bending fretting fatigue acting. Through the failure analysis and numerical simulation, a scheme of the improvements in measuring the existing crimping was brought up. Meanwhile, a plan was also put forward to change the current crimping model and reduce the depth of indentation of clamp tube. Static tensile tests and bending fretting fatigue tests were carried out to evaluate the optional plans, which would help extend the service life of integral dropper in practice.

Real time eco-driving of high speed trains by simulation-based dynamic multi-objective optimization

Eco-driving is a traffic operation measure that may lead to important energy savings in high speed railway systems. Eco-driving optimization has been applied offline in the design of commercial services. However, the benefits of the efficient driving can also be applied on-line in the regulation stage to recover train delays or in general, to adapt the driving to the changing conditions in the line. In this paper the train regulation problem is stated as a dynamic multi-objective optimization model to take advantage in real time of accurate results provided by detailed train simulation. If the simulation model is realistic, the railway operator will be confident on the fulfillment of punctuality requirements. The aim of the optimization model is to find the Pareto front of the possible speed profiles and update it during the train travel. It continuously calculates a set of optimal speed profiles and, when necessary, one of them is used to substitute the nominal driving. The new speed profile is energy efficient under the changing conditions of the problem. The dynamic multi-objective optimization algorithms DNSGA-II and DMOPSO combined with a detailed simulation model are applied to solve this problem. The performance of the dynamic algorithms has been analyzed in a case study using real data from a Spanish high speed line. The results show that dynamic algorithms are faster tracking the Pareto front changes than their static versions. In addition, the chosen algorithms have been compared with the typical delay recovery strategy of drivers showing that DMOPSO provides 7.8% of energy savings.

Mechanism and capability of ventilation openings for alleviating micro-pressure waves emitted from high-speed railway tunnels

Micro-pressure waves are a major environmental problem related to modern high-speed railway systems. The strength of this harmful noise is proportional to the amplitude of the compression wave gradient generated by a high-speed train entering a tunnel. Employing an accurate numerical method, the mechanism and effects of ventilation openings on these compression waves are parametrically investigated. The numerical results indicate that after installing an opening, the compression wave is principally developed as multiple series of wave families, and thus, the pressure gradient curve is formed by numerous peaks and troughs. The gradient peaks UP0 and UV0 are generated successively by the train nose entering the tunnel and passing over the opening, respectively, and dominate the maximum pressure gradient. The vent ratio of the opening can be optimized by balancing these two peaks. However, the vent location and train Mach number can significantly affect the optimizing and the aerodynamic behaviour of the optimized opening, which is attributed to wave superposition. Three original engineering equations are proposed for understanding the effects of the vent ratio, vent location and train Mach number on the gradient peaks, respectively, and the denoising capability of the opening is evaluated.

Effect of elastic rubber mats on the reduction of vibration and noise in high-speed elevated railway systems

In the development of a high-speed railway system, controlling the vibration and noise caused by the system plays an important issue, since the vibration and noise have an influence on the surrounding environment. This study describes the field experiment conducted in September 2015 on the Chengdu–Dujiangyan high-speed railway system where elastic rubber mats – the only countermeasure that is currently applied to reduce vibration and noise in high-speed elevated railway systems in China – were installed in September 2010. The effects of mats under the tracks on noise and vibration were evaluated and analyzed systematically compared to the tracks without mats in the following three aspects: vertical wheel–rail forces; vibration characteristics of the track system, bridge, and ground in combination with the environmental noise characteristics in several frequency domains; and the ride comfort and the interior noise of the vehicle. The results indicate that mats have a negligible effect on the vertical wheel–rail forces, ride comfort, and the interior noise of the vehicle. However, even though they significantly reduce the vibration of the base slab, bridge, and the ground below the mats, vibration of the rails and track slabs above the mats is increased, especially at low frequencies. Mats can also effectively reduce the bridge-borne noise but have little influence on the far-field noise. Furthermore, their control effect on environmental noise and vibration was evaluated in September 2010 and September 2015, showing that mats could effectively minimize the environmental vibration and bridge-borne noise after five years of practical operation, although their control effect declined as their stiffness increased.

An Analytical Study on Dynamic Response of Multiple Simply Supported Beam System Subjected to Moving Loads

Based on Euler–Bernoulli beam theory, first, partial differential equations were established for the vibration of multiple simply supported beams subjected to moving loads. Then, integral transforms were conducted on the spatial displacement coordinate and time in the partial differential equations, and the frequency‐domain response of multiple simply supported beams subjected to moving loads was obtained. Next, by conducting the corresponding inverse transforms on the displacement frequency‐domain responses of multiple simply supported beams, the spatial displacement time‐domain responses were obtained. Finally, to validate the analytical method reported in this paper, the dynamic response of a typical double simply supported rail‐bridge beam system of high‐speed railway in China subjected to a moving load was carried out. The results show that the analytical solution proposed in this paper is consistent with the results obtained from a finite element analysis, validating and rationalizing the analytical solution. Moreover, the system parameters were analyzed for the dynamic response of double simply supported rail‐bridge beam system in high‐speed railway subjected to a moving load with different speeds; the conclusions can be beneficial for engineering practice.

Multicarrier Downlink Transmission for High-speed Railway in Non-Gaussian Noise Channels

We consider a wireless wideband downlink transmission for high-speed railway. In this scenario, the wireless channel is double selective, i.e., multipath and highly time-varying, and involves non-Gaussian noise at the receiver side. Conventional receiver algorithms designed for Gaussian noise and time-invariant channels are inefficient especially for impulsive noise and time-varying multipath channels, which are the main challenges in high-speed railway. They may lead to communication outage and involve large carrier offsets, respectively. Regarding the challenges, a synthesis scheme is proposed to resolve these issues in this paper. First, in order to mitigate the impulsive noise, three impulsive noise detection algorithms are adopted to discriminate impulsive noise from the received signal. The blanking algorithm is used to suppress the discriminated noise. Then, the refined signal goes through a well-designed filtering, which transforms the received signal with varying frequency offsets into an angle domain. The advantage in the angle domain is that the frequency offset in each angle becomes nearly constant. Thus, the frequency offsets can be estimated within each angle to realize accurate estimation. In the simulation, three different impulsive noise models are considered to evaluate the communication reliability in this circumstance. The simulation results show that the proposed scheme significantly improves the reliable performance of the high-speed railway communication systems.

Dynamic analysis of high-speed railway train-bridge system after barge collision

In this paper, a framework is proposed for dynamic analysis of train-bridge systems with a damaged pier after barge collision. In simulating the barge-pier collision, the concrete pier is considered to be nonlinear-inelastic, and the barge-bow is modeled as elastic-plastic. The changes of dynamic properties and deformation of the damaged pier, and the additional unevenness of the track induced by the change of deck profile, are analyzed. The dynamic analysis model for train-bridge coupling system with a damaged pier is established. Based on the framework, an illustrative case study is carried out with a 5x32 m simply-supported PC box-girder bridge and the ICE3 high-speed train, to investigate the dynamic response of the bridge with a damaged pier after barge collision and its influence on the running safety of high-speed train. The results show that after collision by the barge, the vibration properties of the pier and the deck profile of bridge are changed, forming an additional unevenness of the track, by which the dynamic responses of the bridge and the car-body accelerations of the train are increased, and the running safety of high-speed train is affected.

Reduced rank MIMO-OFDM channel estimation for high speed railway communication using 4D GDPS sequences

Abstract This paper presents a reduced rank channel estimator for multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) high speed railway (HSR) systems. Conventional interpolation based channel estimators require high pilot load for robust estimation of the rapidly time varying frequency-selective MIMO-OFDM HSR channel. To relax the high pilot overhead requirement, we take advantage of the channel’s restriction to low dimensional subspaces due to the time, frequency and spatial correlation and propose a low complexity linear minimum mean square error (LMMSE) channel estimator. The channel estimator utilizes a four-dimensional (4D) basis expansion channel model obtained from band-limited generalized discrete prolate spheroidal (GDPS) sequences. Simulation results validate that the mean square estimation error of the proposed estimator is smaller than that of the conventional interpolation based least square (LS) estimator and the performance is robust to different delay, Doppler and angular spreads.

Calculation and Analysis of Ecological Environment Impacts along High-speed Railway

Construction and operation of high-speed railway have significant impacts on the ecological environment within certain range. It is difficult to quantify and analyze effects of different factors. This paper conducts analysis of high-speed railway’s impacts on the ecological environment along the railway comprehensively and systematically. Factors of the ecological environmental impacts are divided into natural ecology, landscape environment, social ecology. Then it proposes specific measurement and calculation method of the secondary factors. Based on the ecological environmental impacts analysis system of high-speed railway, the fuzzy analytic hierarchy process model is built and specific effects of high-speed railway on ecological environment are analyzed.Analysis shows that the main influence of high-speed railway on the ecological environment are natural ecology and social ecological impacts. Consequently, it needs to focus on strengthening the protection of the natural ecological and handling the public interest demands properly during the construction and operation stages of high-speed railway.

LTE-R Handover Point Control Scheme for High-Speed Railways

LTE-R is a new standard under development to serve future high-speed railway systems (HSRs) with reliable real-time train control and management system support as well as passenger safety, convenience, and infotainment services. The QoS of LTE communications is significantly degraded in HSRs due to rapid channel variations that exceed the variation range of LTE systems, resulting in delayed handover or handover failure due to radio link failure. Therefore, a handover decision scheme optimized for HSRs to ensure the QoS requirements for communications is necessary. In this article, a new H2 scheme for HSRs is proposed, which improves the handover performance of high-speed moving LTE systems. The H2 scheme monitors the reference signal received power variation level of the serving evolved node B and handover target evolved node B to prevent late handover and stably execute handover in rapidly changing conditions. Simulation results demonstrate that the proposed H2 scheme can significantly lower the handover failure probability for HSRs compared to the handover schemes currently used in LTE.

Structural Behaviors of Large Span Prestressed PC Bridge Stiffened by CFST Arch

High-speed railway system has been developed with unprecedented pace in recent decades. Various type of bridges (elevated structures) were built for high speed railway infrastructure due to land saving and sound operational condition provided. In this paper, the detailed modeling of the prestressed concrete girder stiffened by concrete filled steel tubular (CFST) arch was developed. Displacement, static stress, dynamic characteristics was obtained by analysis. The overall structural performance has been concluded.

Voltage-Sag-Profiles-Based Fault Location in High-Speed Railway Distribution System

Operation parameters of the high-speed railway distribution system can be obtained from remote terminal units installed in box-type substations. Therefore, the voltage sag profiles may be utilized for fault location. This paper proposes a novel strategy for fault location in a high-speed railway distribution system by measured voltage data of existing box-type substations. The proposed method makes use of the difference between the calculated voltage and measured voltage at the end of the lines to locate the fault. Assuming that the fault occurs at any possible box-type substations along the lines, the faulted line section is identified with the defined difference sequence, and then the exact fault location can be obtained with a searching procedure in the identified fault section. Considering the effect of equivalent capacitance, each line section is modeled with the π model to improve accuracy of fault location. The validity of the proposed method is tested extensively in the simulation model of a real high-speed railway distribution system. The proposed method is not affected by fault type and fault resistance. Furthermore, comparing with the offline detection method of underground cables, it does not need any additional devices and will not interrupt the system operations.

Locator slope calculation via deep representations based on monocular vision

The locator is the key component to control the track of contact wire in overhead catenary system (OCS) for high-speed railway. Once the locator slope is out of bound, it would pose a huge hazard to the safety of the high-speed trains and threat to the human life and property damage. In this work, a novel end-to-end locator slope calculation framework is presented for locator slope real-time inspection in high-speed railway system. The pipeline is composed of two stages: locator contour detection and slope calculation. In order to precisely detect the locator contours in OCS images captured from high-speed extreme environments, a novel detection mechanism including rough detection and fine fitting is proposed. For the fast slope calculation through only one camera, monocular vision model is modified by two novel assumptions to calculate the locator space coordinates. Rigorous experiments are performed across a number of standard locator slope calculation benchmarks, showing a large improvement in the precision and speed over all previous methods. Finally, the effectiveness of proposed framework is demonstrated through a real-world application of the high-speed rail OCS inspection system.

A Novel Method for Calculating the Radiated Disturbance From Pantograph Arcing in High-Speed Railway

Pantograph arcing is a key electromagnetic disturbance source to affect train control system in high-speed railway. Since the characteristics of pantograph arcing are related to train speed, it is necessary to investigate effective numerical modeling and measurement method. However, due to the uncontrollable train speed during onsite measurement, it is difficult to study the radiated disturbance from arcing in the corresponding speed and repeat the same measurement. Therefore, a method that combines numerical modeling and reverberation chamber measurements for calculating the radiated disturbance from pantograph arcing in a high-speed railway is proposed. Numerical models of train and sensitive equipment are built to calculate the coupling coefficient in CONCEPT II. And a new measurement procedure in reverberation chamber using pulse signal as the reference source is proposed based on a speed-controllable laboratory replica to measure the total radiated power of pantograph arcing. Then, the radiated disturbance from pantograph arcing to the sensitive equipment is achieved with the coupling coefficient and the total radiated power of arcing. The method is verified by laboratory experiments. This method can solve the uncontrollable train speed problem during on-site measurement and improve the repeatability of measurement.

Position-Aided Large-Scale MIMO Channel Estimation for High-Speed Railway Communication Systems

We consider channel estimation for high-speed railway communication systems, where both the transmitter and the receiver are equipped with large-scale antenna arrays. It is known that the throughput of conventional training schemes monotonically decreases with the mobility. Assuming that the moving terminal employs a large linear antenna array, this paper proposes a position-aided channel estimation scheme whereby only a portion of the transmit antennas send pilot symbols and the full channel matrix can be well estimated by using these pilots together with the antenna position information based on the joint spatial-temporal correlation. The relationship between mobility and throughput/DoF is established. Furthermore, the optimal selections of transmit power and time interval partition between the training and data phases as well as the antenna size are presented accordingly. Both analytical and simulation results show that the system throughput with the position-aided channel estimator does not deteriorate appreciably as the mobility increases, which is sharply in contrast with the conventional one.

Model of the 2 × 25 kV high speed railway supply system taking into account the soil-air interface

This paper deals with the modelling of the 2×25kV – 50Hz high speed railway supply system. The proposed approach extends the traditional multi-conductor transmission line approach typically used for high speed railway systems, which is based on the assumption of overhead conductors. More specifically, this approach models the system by considering the presence of both overhead and buried conductors. Analytical formulations to calculate self and mutual line parameters are used. A numerical simulation allows evidencing the different results when the simplified and the detailed modelling approaches are adopted. A sensitivity analysis to point out the influence of the finitely conductive ground is also proposed.