Search

The train operates in special environments such as large bridges and elevated viaducts. The fluctuations of the aerodynamic loads of the high-speed train (HST) are more intense and the possibility of the train derailment and overturning will increase when the train is running on the bridge under the crosswind. Thus, it is of utmost importance to study both the aerodynamic characteristics and the running safety of the train in this situation. This study uses the IDDES method to investigate the aerodynamic characteristics of the train running on the double track bridge in both up and down train directions at different speeds. The differences in the impact of aerodynamic loads on the train's dynamic response indicators are discussed using the wind-vehicle coupling dynamic response calculation method. Based on these researches, the operational safety of the train under different operating conditions is evaluated from both flow field and dynamic perspectives. The results show that large-scale vortices fall off from the nose of the train and form a larger vortex structure on the leeward side and when the train is running under the crosswind. Its aerodynamic loads fluctuate intensely with time due to the complex wake flow of the train. The dominant frequencies of the unsteady aerodynamic loads are mostly concentrated in the range of 0–5Hz, which is close to the natural modal frequencies of the train. This will lead to the overturning of the train due to vehicle resonance. The derailment coefficient and wheel load reduction rate of the train increase with the speed. Their peak values exceed the limit of 0.8 while the peak duration of the derailment coefficient is less than 0.05s, which means the state of the leeward wheel will recover from a short derailment. However, the duration of derailment increases with speed. Therefore, appropriate measures should be taken to prevent accidents when the train is running at higher speed on the bridge to guarantee the operational safety of the HST. [ABSTRACT FROM AUTHOR]

The terrestrial television system in Indonesia has evolved from the first-generation Digital Terrestrial Video Broadcasting (DVB-T) to the second generation (DVB-T2), enhancing broadcast quality and spectral efficiency. This paper focuses on the application of DVB-T2 within High-Speed Train (HST) communication systems, where the unique challenges faced include high Doppler shifts and multipath effects due to the high train speed which exceeds 300 km/h. Multicarrier Orthogonal Frequency Division Multiplexing (OFDM) technology was employed along with 64-QAM modulation for the investigation of the performance under various conditions. The simulations were structured around varying speeds, scatterer counts, and angles, and 15 iterations were conducted for train speeds of 10 m/s, 50 m/s, and 100 m/s. The findings indicate that the error rates varied with speed and environmental complexity. At a lower speed (10 m/s), the system performance showed significant improvement, with a reduction of 322 bits in the error rate. However, as the speed increased to 100 m/s, the performance declined, demonstrating an increase of errors by 414 bits owing to exacerbated Doppler effects. Different scatterer counts also influenced the results. For instance, with four scatterers at 10 m/s speed, the error improved by 245 bits, but at 100 m/s speed and under the same scatterer conditions, the performance worsened, increasing the error by 361 bits. [ABSTRACT FROM AUTHOR]

Bilateral vertical noise barriers have been widely used along high-speed railway lines in coastal cities where typhoons are frequent. When a high-speed train (HST) enters (or exits) a noise barrier under strong crosswind conditions, its running safety will be more severely tested because of the instantaneous switching of aerodynamic environment. Installing a buffer structure at the end of the noise barrier is necessary to ensure the running safety of HSTs. In this study, two types of aerodynamic buffer structures (triangle and fence types) for the end of the noise barrier are proposed. The buffering effects of the two structures on the sudden change amplitude of the aerodynamic load of the carriage are compared by using an improved delayed detached eddy simulation method. The difference in the influence of the two buffer structures on the aerodynamic responses of the carriage is discussed by using a wind--train--bridge coupling dynamic response calculation method. The buffer mechanisms of the two structures are revealed in terms of the flow field. Results show that the buffering effect of fence type is superior triangle type, and the buffer length of 4 L is the most reasonable. [ABSTRACT FROM AUTHOR]

The acceleration of land desertification has led to an increasingly serious threat to the operation safety of tunnel entrance in the Gobi and desert regions by wind-sand flow, and it is urgent to study and enhance the running safety of train. Firstly, an ultrasonic anemometer is used to collect the characteristics of wind-sand flow at a tunnel entrance site in Xinjiang, China. Then, based on the Euler multiphase flow and the SST k-w model, the variation difference law of the train running at the tunnel entrance is revealed under the four inflow conditions of constant crosswind, constant wind-sand flow, pulsating crosswind and pulsating wind-sand flow respectively. Finally, the disturbance law of the solid wind barrier at the tunnel entrance on the wind-sand flow and the influence mechanism on the train's flow field structure and pressure are revealed. The results show that compared with other cases, the pulsating wind-sand flow has the most significant effect on the moving trains' aerodynamic loads (ALs), and the sand particles carried in the air cause the trains' ALs to fluctuate within 9.09%. The solid wind barrier has a significant disturbing effect on the wind-sand flow, and the lightweight sand particles follow the air flow over the top of the wind barrier and are not deposited on the embankment during a short period, and the wind-sand flow's impact on the HSTs is dramatically reduced. The wind barrier changes the HST's flow field, and the AL fluctuation of the train is sharply reduced. The maximum values of the head train's AL coefficients are reduced by 46.53-85.75%. [ABSTRACT FROM AUTHOR]

Bilateral vertical noise barriers have been widely used along high-speed railway lines in coastal cities where typhoons are frequent. When a high-speed train (HST) enters (or exits) a noise barrier under strong crosswind conditions, its running safety will be more severely tested because of the instantaneous switching of aerodynamic environment. Installing a buffer structure at the end of the noise barrier is necessary to ensure the running safety of HSTs. In this study, two types of aerodynamic buffer structures (triangle and fence types) for the end of the noise barrier are proposed. The buffering effects of the two structures on the sudden change amplitude of the aerodynamic load of the carriage are compared by using an improved delayed detached eddy simulation method. The difference in the influence of the two buffer structures on the aerodynamic responses of the carriage is discussed by using a wind–train–bridge coupling dynamic response calculation method. The buffer mechanisms of the two structures are revealed in terms of the flow field. Results show that the buffering effect of fence type is superior triangle type, and the buffer length of 4 L is the most reasonable.

The acceleration of land desertification has led to an increasingly serious threat to the operation safety of tunnel entrance in the Gobi and desert regions by wind-sand flow, and it is urgent to study and enhance the running safety of train. Firstly, an ultrasonic anemometer is used to collect the characteristics of wind-sand flow at a tunnel entrance site in Xinjiang, China. Then, based on the Euler multiphase flow and the SST k-w model, the variation difference law of the train running at the tunnel entrance is revealed under the four inflow conditions of constant crosswind, constant wind-sand flow, pulsating crosswind and pulsating wind-sand flow respectively. Finally, the disturbance law of the solid wind barrier at the tunnel entrance on the wind-sand flow and the influence mechanism on the train’s flow field structure and pressure are revealed. The results show that compared with other cases, the pulsating wind-sand flow has the most significant effect on the moving trains’ aerodynamic loads (ALs), and the sand particles carried in the air cause the trains’ ALs to fluctuate within 9.09%. The solid wind barrier has a significant disturbing effect on the wind-sand flow, and the lightweight sand particles follow the air flow over the top of the wind barrier and are not deposited on the embankment during a short period, and the wind-sand flow’s impact on the HSTs is dramatically reduced. The wind barrier changes the HST’s flow field, and the AL fluctuation of the train is sharply reduced. The maximum values of the head train’s AL coefficients are reduced by 46.53–85.75%.

In the proposed system setup, a communication link is established between base station (BS) and end-user (UE) via a relay node mounted on the high-speed train (HST). The information is conveyed over backhaul RF links between BS and relay and over VLC links between relay and UE inside the train. It is assumed that RF links are encountered with dual shadowing due to slow-moving vehicles and pedestrians. Moreover, the relay node is not able to estimate the channel information perfectly due to HST mobility. Firstly, the statistical characteristics, such as the probability density function (PDF) and cumulative distribution function of the BS-relay link, are derived under imperfect channel information. Then, the system performance is examined by deriving the two key metrics, outage probability, and average bit error rate. Furthermore, we investigate the secrecy performance of the proposed system when the RF eavesdropper overhears the link between BS and relay and the VLC eavesdropper captures the information via the relay-UE link. To this end, the secure outage probability is derived into a closed form. Our results reveal that the proposed system setup can be adopted as a network architecture for existing as well as for future HST networks.

In recent years, the use of massive multiple-input multiple-output (MIMO) systems and higher frequency bands for next-generation urban rail transportation systems has emerged as an intriguing research topic due to its potential to significantly increase network capacity by utilizing available narrowband and broadband spectrums. In metro and mining applications, the high-reliability wireless sensor network (WSN) plays a vital role in providing personal safety, channel optimization, and improving operational performance. Through the duration of 1921–2023, this paper provides the survey on the progress of fifth-generation (5G) and beyond-fifth-generation (B5G) wireless communication systems in underground environments such as tunnels and mines, the evolution of the earliest technologies, development in channel modeling for vehicle-to-vehicle (V2V) communications, and realization of different wireless propagation channels in high-speed train (HST) environments. In addition, the most recent advanced channel modeling methods are examined, including the development of new algorithms and their use in intelligent transportation systems (ITS); mathematical, analytical, and experimental techniques for propagation design; and the significance of the radiation characteristics, antenna placing, and physical environment effect on wireless communications. Leaky coaxial cable (LCX) and distributed antenna system (DAS) designs are introduced in the demonstrated systems for improving the channel capacity of narrowband and wideband channels as well as the spatial characteristics of various MIMO systems. The review article concludes by figuring out open research directions for future technologies. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Zhejiang University: Science A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The massive heat dissipation demands of the brake system in high-speed trains pose a significant obstacle to achieving higher operation speeds. Phase change material has attracted considerable attention in various fields due to their exceptional heat dissipation capabilities, yet their utilization in the brake system of high-speed trains remains unexplored. This study aims to investigate the feasibility of phase change material application in the brake system of high-speed train. Specifically, in Case A, the introduction of phase change material resulted in a notable 21% decrease in the average temperature and a remarkable 40% reduction in the maximum temperature difference within the brake system. The latent heat of the phase change material plays a crucial role in maintaining a substantial temperature differential between the cooling components and discs, thereby enhancing heat flux in the brake system. Phase change materials exhibit superior cooling performance compared to traditional air cooling methods in the brake system. To expedite the cooling process of phase change material and facilitate its transition from liquid to solid, an optimized brake system structure utilizing phase change material was proposed. This optimized design holds promise in enhancing the overall heat dissipation efficiency of the high-speed train brake system. [ABSTRACT FROM AUTHOR]

In this paper, the full state dependent event-triggered aperiodic intermittent control (FE-AIC) strategy based on input constraints is introduced to minimize energy consumption and enhance speed tracking accuracy in the high-speed train (HST) operation. Firstly, a dynamic model based on multi-mass-point (MMP) for HST has been established, transforming the cruise control problem into an error asymptotic convergence problem. Secondly, restricted FE-AIC (RFE-AIC) controller is designed separately in the presence and absence of external disturbances to realize tracking objects. The proposed control scheme is not only based on control input constraints, but also intermittent control with full state event dependence. The RFE-AIC scheme and the conditions for determining parameters are given, which ensures the stability of the ideal tracking speed and coupler deviation at the equilibrium point. Eventually, the availability of the proposed method in cruise control is confirmed through numerical simulations. It is proved that the RFE-AIC has better performance compared with the self-triggered and guaranteed optimal cruise control methods., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 International Society of Automation. Published by Elsevier Ltd. All rights reserved.)

The characteristics of the aerodynamic effects of high-speed trains passing in a shield tunnel were studied using the three-dimensional, compressible, unsteady Reynolds-averaged Navier-Stokes (RANS) equations for the simulation analysis. Numerical calculations were compared with dynamic model tests to verify the reliability of the numerical simulations. The results showed that the compression wave characteristics of high-speed trains in shield tunnels were consistent with those in molded concrete tunnels. When high-speed trains met in the middle of the shield tunnel, the positive and negative peak attenuation rates of shield tunnels were higher than the positive and negative peak attenuation rates of molded lining tunnels, and the maximum pressure attenuation rate could reach 57.8%. At the same time, the micro-pressure wave of the former was reduced by 10.78%, compared with those of the latter. When meeting cars at different locations, the maximum pressure at the intersection in the center of the tunnel was significantly higher than those at other intersection points in the tunnel. Different intersection positions and different tunnel lining structures had relatively little influence on the aerodynamic drag and lateral force, while train speed had a significant influence. [ABSTRACT FROM AUTHOR]

The high-speed railway (HSR) has been an essential medium for intercity connections in China. However, despite the great achievements in HSR development, conventional railway (CR) still plays an important role in China's railway passenger market. In this study, we construct urban networks based on China's high-speed train (HST) and conventional train (CT) services, and compare the characteristics of HST and CT services in spatial distribution. Moreover, policy implications are proposed for coordinating the HSR and CR systems based on the actual operating performance of the two modes. The results show that China's HST and CT services are complementary in terms of spatial distribution. Both HSR and CR achieve high passenger volumes in prosperous regions, but CR performs better in areas with lower socioeconomic performance. We suggest that there is a significant potential for the cooperation between China's HSR and CR systems, but some operating and technological challenges must be overcome. • We compare the operating modes and network structures of China's HST and CT services. • We identify the dominant space of HSR and CR based on train services and passenger flows. • China's HST and CT services are complementary in operating modes and dominant space. • Some policy implications are for proposed for coordinating the HSR and CR systems. [ABSTRACT FROM AUTHOR]

Porous wind barriers (PWBs) are gradually applied to tunnel–bridge–tunnel infrastructures (TBTIs) along high-speed railway lines. Due to the remarkable aerodynamic effect of high-speed trains (HSTs), the windproof performance of a PWB at tunnel–bridge section (TBS) is particularly critical when a HST passes through the TBTI under crosswind. And it seems to be easily ignored by researchers. This study aims to determine the influence mechanism of the PWB in the TBS. A CFD dynamic model of air–train–PWB was built based on porous media theory, and its reliability is verified by model and field tests. The main results are as follows: the corresponding variation amplitudes of the train’s aerodynamic load coefficients are reduced by 36–95% when a PWB is set in the TBS; adopting the same design parameters along the full-length PWB on the TBTI is unreasonable; the PWB height and porosity in the TBS must be increased and reduced more than 33%, respectively, to achieve equivalent windproof performance. The conclusions in this paper can provide a preliminary idea for the optimization design of the PWB on the TBTI.

The high-speed train (HST) air brake system (ABS) is crucial to guarantee a safe and reliable operation environment for passengers on board. Recently, a novel combined index has been proposed for incipient fault detection of the ABS. Following detection, fault isolation is quite desired so as to find out the root causes of the occurred fault and provide valuable information for preventive maintenance and repairs. In this work, the combined index is briefly revisited and its detectability analysis is first formally developed, which can reveal certain detection properties theoretically. Then, a fault-recovery-based optimization strategy is presented for fault isolation purpose. Through theoretical reasoning it is indicated that, with accurately assumed fault direction information, the proposed methodology is able to accomplish correct isolation. Extensive tests on a practical ABS platform demonstrate the effectiveness of the proposed fault detection and isolation approaches. [ABSTRACT FROM AUTHOR]

Porous wind barriers (PWBs) are gradually applied to tunnel–bridge–tunnel infrastructures (TBTIs) along high-speed railway lines. Due to the remarkable aerodynamic effect of high-speed trains (HSTs), the windproof performance of a PWB at tunnel–bridge section (TBS) is particularly critical when a HST passes through the TBTI under crosswind. And it seems to be easily ignored by researchers. This study aims to determine the influence mechanism of the PWB in the TBS. A CFD dynamic model of air–train–PWB was built based on porous media theory, and its reliability is verified by model and field tests. The main results are as follows: the corresponding variation amplitudes of the train's aerodynamic load coefficients are reduced by 36–95% when a PWB is set in the TBS; adopting the same design parameters along the full-length PWB on the TBTI is unreasonable; the PWB height and porosity in the TBS must be increased and reduced more than 33%, respectively, to achieve equivalent windproof performance. The conclusions in this paper can provide a preliminary idea for the optimization design of the PWB on the TBTI. [ABSTRACT FROM AUTHOR]

This paper investigates an adaptive fault-tolerant pseudo-proportional-integral-derivative sliding-mode control (pseudo-PID-SMC) scheme for a high-speed train (HST) subject to actuator faults, asymmetric nonlinear actuator saturation (ANAS), and integral quadratic constraints (IQCs). It is worth mentioning that a pseudo-PID-SMC surface is proposed in this paper and the scheme based on this surface does not require acceleration measurement. An adaptive saturation compensation system that makes no assumption, as in existing works where nonlinear functions are used to describe the unsaturated region of ANAS as known and strictly monotonous, is developed to attenuate the adverse effects of ANAS. For the saturation-free and ANAS cases, two adaptive fault-tolerant pseudo-PID-SMC schemes with no chattering, a simple structure, and inexpensive computation are developed to guarantee the exponential convergence of all signals in the closed-loop systems. Finally, simulation results based on a real train dynamic model are presented to show the proposed schemes’ effectiveness and feasibility. [ABSTRACT FROM AUTHOR]

This article proposes a new spatial iterative learning control (ILC) algorithm that can track the desired trajectory for operation control of high-speed train (HST) in the presence of time-varying adhesion dynamics between wheel and track. Although the adhesion dynamics will affect the overall performance and might lead to an unsafe scenario, not much work has been done to handle them in the field of operation control of HST. As the operation process of HST is repetitive in spatial domain, the conventional ILC algorithms, in which finite time domain is always considered, cannot be directly applied to such kind of system. In order to address spatial learning, the train’s operation dynamics, including the adhesion dynamics, are first developed. By revealing the link between the temporal gradient and the spatial gradient, the operation dynamics can be converted from the time domain into the spatial domain, making the ILC design feasible. A novel ILC algorithm is then proposed to ensure the convergence with the help of a new composite energy function (CEF). It is highlighted that in this CEF analysis, dynamic systems are not required to be globally Lipschitz, which is one of the standing assumptions needed in the convergence analysis of ILC. The effectiveness of the proposed spatial ILC algorithm is demonstrated from a simulation example. [ABSTRACT FROM AUTHOR]

With the explosion of data traffic, the use of caching technology to offload data traffic is a very effective way to alleviate network pressure, especially in high-speed train (HST) scenarios. And when users participate in the caching game, the costs of data offloading are greatly reduced. However, current research on users’ participation in data traffic offloading is not much; and there are user security and data reliability issues in the cache of device-to-device (D2D) network. Therefore, in this paper, we propose a novel scheme that user terminals (UTs) cooperatively cache wireless services to the intelligent routing relay (IRR) side in HST scenarios; and we establish a reverse auction model to motivate UTs to collaborate and cache. In this model, IRR acts as the purchaser of the wireless services and UTs are suppliers and consumers. We propose a synchronous reverse auction strategy (S-RAS) to maximize the social incomes at first. However, UTs often have to wait for a long time before the auction begins. Then, we adopt an asynchronous reverse auction strategy (A-RAS) to minimize UTs’ waiting time. Ultimately, in order to minimize UTs’ waiting time while maximizing social incomes, we propose the popularity based hybrid reverse auction strategy (PB-H-RAS) considering both the advantages of S-RAS and A-RAS. Simulation and experiment results verify the effectiveness of the proposed PB-H-RAS strategy; and they also show that the performances of PB-H-RAS strategy are better than the other two strategies in terms of final incomes and completion rate. [ABSTRACT FROM AUTHOR]

Monitoring the operating status of a High-Speed Train (HST) at any moment is necessary to ensure its security. Multi-channel vibration signals are collected by sensors installed on bogies and beneficial information are extracted to determine the running condition. Based on multi-view clustering and considering different views of complementary information, this study proposes a Multi-view Kernel Fuzzy C-Means (MvKFCM) model for condition recognition of the HST bogie. First, fast Fourier transform coefficients of HST vibration signals of all channels are extracted. Then, the fuzzy classification coefficient of every channel is calculated after clustering to select the appropriate channels. Finally, the selected channels are used to cluster by MvKFCM and the conditions of HST are determined. Experimental results show that the selection is effective to maintain rich feature information and remove redundancy. Furthermore, the condition recognition rate of MvKFCM is higher than that of single-view and four other multiple-view clustering algorithms.

Authorized content is a type of content that can be generated only by a certain Content Provider (CP). The content copies delivered to a user may bring rewards to the CP if the content is adopted by the user. The overall reward obtained by the CP depends on the user’s degree of interest in the content and the user’s role in disseminating the content copies. Thus, to maximize the reward, the content provider is motivated to disseminate the authorized content to the most interested users. In this paper, we study how to effectively disseminate the authorized content in Interest-centric Opportunistic Social Networks (IOSNs) such that the reward is maximized. We first derive Social Connection Pattern (SCP) data to handle the challenging opportunistic connections in IOSNs and statistically analyze the interest distribution of the users contacted or connected. The SCP is used to predict the interests of possible contactors and connectors. Then, we propose our SCP-based Dissemination (SCPD) algorithm to calculate the optimum number of content copies to disseminate when two users meet. Our dataset based simulation shows that our SCPD algorithm is effective and efficient to disseminate the authorized content in IOSNs.

Realizing the accurate fault diagnosis of high-speed train (HST) bogie is of great significance for ensuring the safe operation of HSTs. This article proposes a novel fault diagnosis method to identify the fault states of HST bogie and localize the positions of faulty components simultaneously by virtue of the improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN) and 1-D convolutional neural network (1-D CNN). First, the raw vibration signal is decomposed into multiple intrinsic mode functions (IMFs) via the ICEEMDAN. Then, the high-frequency components of IMFs obtained by ICEEMDAN are selected as the fault features of the HST bogie. Afterward, the 1-D CNN model is adopted to learn the deeper features from the high-frequency components to conduct fault classification and localization. The prediction accuracy of the proposed method is 99.3% and 98.7% on two bogie data sets, respectively. Meanwhile, experimental results demonstrate the effectiveness of the proposed method in identifying both the categories and the locations of faulty components, whose superiority has been verified by the comprehensive comparison analysis with traditional deep learning methods and state-of-art methods, including residual-squeeze net, convolutional recurrent neural network, and DenseNet. [ABSTRACT FROM AUTHOR]

Due to the time-varying characteristics and the interacted nature of multiple faults in the high-speed train (HST), the fault modeling, isolation, and severity estimation cannot be described accurately using a single model, which may result in poor performance of the conventional fault diagnosis methods. This article introduces the idea of multiple models and second-level adaptation techniques to diagnose multiple faults of the HST traction motor. First, a reduced model description for the multiple faults is given. Then, a multiple fault isolation framework is developed to simplify the time-varying fault parameters space segmentation. Based on the decoupled fault set, a fault estimation scheme with second-level adaptation is used to provide a reliable alarm priority for different fault scenarios. A case study is performed to verify the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

The problem of extended dissipativity performance of a high-speed train (HST) with probabilistic delays and actuator faults under resilient reliable control has been exploited in this article. An extended dissipativity index is selected to perform a unified control design procedure for the HST dynamics, which is more general than $(\mathbb {Q},\mathbb {S},\mathbb {R})$ -dissipativity index. Specifically, a sequence of random variables responding the Bernoulli distribution is exploited to govern the probabilistic time-delays. By utilizing the tighter integral inequality (TII) and reciprocally convex inequality (RCI) technique, some criteria are launched in terms of the linear matrix inequalities (LMIs). Finally, simulations show the effectiveness and applicability of the offered control law by inspecting the Japan Shinkansen HST with its experimental values, along with a comparison study also been exploited to showing the merits and generalization of the proposed control design technique. [ABSTRACT FROM AUTHOR]

Thousands of high-speed trains (HSTs) run on over 30000-km high-speed railway every day in China. These running trains not only cause vibrations but also stimulate all kinds of seismic waves. The receiver seismic signal’s spectrum has one special equal-interval, multinarrowband feature. Some commonly used time-frequency (TF) analyzing methods, such as the short-time Fourier transform, continuous wavelet transform, and the Stockwell transform, can capture a signal’s TF features and reconstruct signal without loss. However, their TF resolution is limited by the uncertainty principle. In this letter, we apply the second-order synchrosqueezing continuous wavelet transform (SSCWT), which is one improved SSCWT, to the HST induced seismic signal and capture its TF spectrum features. The synthetic data example and real data example have proved the second-order SSCWT can provide a more concentrated TF spectrum than the commonly used SSCWT. [ABSTRACT FROM AUTHOR]

The characteristics of the aerodynamic effects of high-speed trains passing in a shield tunnel were studied using the three-dimensional, compressible, unsteady Reynolds-averaged Navier-Stokes (RANS) equations for the simulation analysis. Numerical calculations were compared with dynamic model tests to verify the reliability of the numerical simulations. The results showed that the compression wave characteristics of high-speed trains in shield tunnels were consistent with those in molded concrete tunnels. When high-speed trains met in the middle of the shield tunnel, the positive and negative peak attenuation rates of shield tunnels were higher than the positive and negative peak attenuation rates of molded lining tunnels, and the maximum pressure attenuation rate could reach 57.8%. At the same time, the micro-pressure wave of the former was reduced by 10.78%, compared with those of the latter. When meeting cars at different locations, the maximum pressure at the intersection in the center of the tunnel was significantly higher than those at other intersection points in the tunnel. Different intersection positions and different tunnel lining structures had relatively little influence on the aerodynamic drag and lateral force, while train speed had a significant influence.

This article presents a review in three parts on the current traction motor topologies available in the railway market. In the first part, essential aspects of the electromagnetic design of railway traction motors, e.g., motor sizing and rotor configurations, are discussed. Different topologies are compared considering the wide range of applications. The pros and cons of each topology in specific applications are highlighted based on the corresponding performance requirements. In the second part, different cooling configurations of traction motors common in railway are reviewed, focusing on the solutions based on air cooling. The third part presents a review of the available insulation systems for traction motors. Two primary insulation systems used in traction applications with thermal classes of H and N are discussed. The focus in this article is placed on the main applications in railway including light rail vehicles, metros, electric multiple units, high-speed trains, and locomotives. Additionally, trends in traction motors development in the coming years are reported separately for electromagnetic, cooling, and insulation designs. [ABSTRACT FROM AUTHOR]

In this paper, the speed and position control of high-speed trains (HSTs) under non-strictly repeated conditions is investigated. Considering the modeling accuracy and control cost, a multi-particle dynamics model is established in a single coordinate system. Based on this model, a novel robust adaptive iterative learning control (RAILC) method is proposed. The Lyapunov function is established to prove that the system state converges in a finite time, and the composite energy function (CEF) is constructed to prove that the control error approaches zero along the iteration axis. The application value in engineering practice of the proposed RAILC is verified by two simulation tests. Existing adaptive iterative learning control (AILC) and adaptive terminal sliding mode control (ATSMC) are introduced as control groups to show the system convergence of the RAILC on the iteration axis and time axis. • Effectively utilizing but not overly relying on historical operation data under non-strictly repeated conditions. • The state of the closed-loop system converges in finite time and approaches zero along the iteration axis. • It is the first use of robust control to solve the limitations of iterative learning on high-speed train. • Numerical simulations with control groups validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In order to make full use of the complementary information of multichannel vibration signals, this paper proposes a method of channel selection based on the similarity ratio and constructs a multichannel deep belief network (MDBN) for condition analysis of a high-speed train. First, fast Fourier transform (FFT) coefficients of the signals of all channels are extracted. Then, the similarity ratio of FFT coefficients of each channel is calculated, and a number of channels with a large similarity ratio are selected. Finally, the MDBN model is constructed to learn the features of the selected multichannel data and recognize conditions, and the feature fusion of multichannel data is realized in the common layer. The experimental results show that the similarity ratio is effective to select the channels with rich feature information, the feature learning ability of MDBN is better than DBN, and the condition recognition rate of MDBN is higher than other state-of-the-art methods. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a cache-based popular services pushing solution on high-speed train (HST) by using converged wireless broadcasting and cellular networks. Pushing and caching popular services on the HST to improve the capacity of the network is a very efficient way; and it can also bring a better user experience. The most popular services are transmitted and cached on the vehicle relay station of the train ahead the departure time in the proposed model. Then, the most popular services are broadcasted and cached on the User Equipment after all the passengers are on the train; the less popular services are delivered to the passengers by P2P mode through the relayed cellular network on the train. Specifically, we firstly use the dynamic programming algorithm to maximize the network capacity in limited pushing time, which can be converted to the 0–1 Knapsack problem. Furthermore, we propose three greedy algorithms to approximate the optimal solution on account of the high time complexity of dynamic programming when the input scale gets bigger. And simulation results show that the proposed popularity-based greedy algorithm performs well. Moreover, as the passengers may get on and off the HST when arriving at an intermediate station, a services rebroadcast algorithm is employed when more intermediate stations are considered. U-shaped distribution is adopted to indicate the number of passengers getting on and off the train. Simulations also show that the proposed rebroadcast algorithm can efficiently improve the capacity of the converged networks. [ABSTRACT FROM AUTHOR]

Highlights • A 3D unsteady incompressible numerical method is adopted. • The transient characteristics of aerodynamic loads of the HST are analyzed. • The sudden change mechanisms of the aerodynamic loads are revealed from flow field. Abstract Windbreak (WB) and anti-wind open-cut tunnel (AOT) are two common windproof facilities for high-speed railways in windy areas. This study aims to determine which of them has better aerodynamic performance. For this purpose, the transient aerodynamic loads of high-speed trains are compared when passing through two windproof facilities under the same conditions of train and crosswind speeds via CFD simulation. The sudden change mechanism of aerodynamic loads and the differences in aerodynamic loads between the AOT and WB cases are revealed from the perspectives of flow field and pressure. Four main conclusions are obtained. Firstly, the fluctuation amplitudes of the five aerodynamic loads of each carriage in two periods (entry and exit) are remarkably greater than those in other periods (completely running in crosswind or windproof facilities). Secondly, the maximum fluctuation amplitudes of the five aerodynamic loads of the head carriage are generally greater than those of the rear and middle carriages during the period of entry (or exit). Thirdly, the maximum fluctuation amplitudes of side force, lift force, rolling moment, yawing moment and pitching moment of the head carriage in the WB case are 1.42, 0.84, 1.42, 1.45 and 1.44 times for the period of entry and 1.2, 1.24, 1.2, 1.58 and 2 times for the period of exit, respectively, compared with those in the AOT case. Fourthly, the maximum change rates at a time interval of 0.035 s of the side force, lift force, rolling moment, yawing moment and pitching moment of the head carriage in the WB case are 1.32, 1.26, 1.32, 1.57 and 1.52 times for the period of entry and 1.13, 1.24, 1.13, 1.42 and 1.69 times for the period of exit, respectively, compared with those in the AOT case. [ABSTRACT FROM AUTHOR]

Highlights • The differences in aerodynamic loads between the AOT and WB cases are revealed. • The running posture of each carriage is analyzed. • The response differences between the windward and leeward side wheels are revealed. • The safety of the HST in four running environments is evaluated. • The safety domain boundaries of the HST in four running scenarios are plotted. Abstract Windbreak (WB) and anti-wind open-cut tunnel (AOT) are two common windproof facilities for high-speed railways in windy areas. This study aims to conducts a comparison of the aerodynamic loads and corresponding traffic safety of both windproof facilities when the high-speed train (HST) passes through them under crosswind conditions. The aerodynamic loads are obtained via CFD simulation, and safety indexes are generated through the wind-train-track dynamic analysis system. The main common characteristics between AOT and WB cases are as follows. Firstly, the fluctuation amplitudes of the five aerodynamic loads of each carriage in two periods (i.e., entry and exit) are remarkably greater than those in other periods (i.e., running completely in crosswind or windproof facilities). Secondly, the sudden increase in the fluctuation amplitudes of the safety indexes is an important factor in the reduced safety of HST traffic, and the derailment coefficient (DC) of the head carriage is the key to control the safety of the entire HST. Thirdly, the existence of the ends of windproof facilities narrows the original safety domain scope of the HST running only in crosswind. The main differences between AOT and WB cases are as follows. Firstly, the maximum fluctuation amplitudes of the five aerodynamic loads of each carriage in the WB case are generally greater than the corresponding values in the AOT case, whether entry or exit, under the same conditions of train and crosswind speeds. Secondly, the scope of safety domain when the HST passes through the ends of the WB is considerably smaller than that of the HST passing through the AOT ends, and the AOT is more effective than WB in terms of windproof effects. Thirdly, for the high-speed railway in the windy area with AOT and WB, the safety domain boundaries V t = −6.3 V w + 343.3 and V t = −10 V w + 350 can be used respectively to provide a reference for traffic safety command. [ABSTRACT FROM AUTHOR]

Based on the analysis of the practical measurement data of H-field values at three different sites along the longitudinal direction of the railway, this paper proposes an aerial catenary nonuniform transmission line model to predict longitudinal propagation characteristic of pantograph arcing electromagnetic (EM). According to the theory of EM field, EM emission field value measured at articulated neutral section (ANS) site is converted into the initial current of the contact wire. With the initial current, the current distribution on the contact wire and the EM field distribution along the railway when pantograph slid the ANS could be obtained by the proposed model. The validity of the proposed model is verified by the consistency of the theoretical results and the practical measurement at 0.5 MHz, which is the frequency point of the nondirectional radio beacon (NDB). [ABSTRACT FROM AUTHOR]

It is well known that the train nose shape has significant influence on the aerodynamic characteristics. This study explores the influence of four kinds of nose shapes (fusiform, flat-broad, bulge-broad, ellipsoidal) on the aerodynamic performance of two opposing high-speed trains passing by each other through a tunnel at 250 km/h. The method of three dimensional, compressible, unsteady Reynolds-averaged Navier-Stokes equations and RNG k-ε double equation turbulence model was carried out to simulate the whole process of two trains passing by each other inside a tunnel. Then the pressure variations on tunnel wall and train surface are compared with previous full-scale test to validate the numerical method adopted in this paper. The assessment characteristics, such as transient pressure and aerodynamic loading, are analyzed to investigate the influence of nose shape on these assessment parameters. It is revealed that aerodynamic performance of trains which have longitudinal nose profile line B (fusiform, flat-broad shape) is relatively better when passing by each other in a tunnel. The results can be used as a guideline for high-speed train nose shape design.

This paper develops a closed-loop coupled fault estimation and a multivariable resilient control for high-speed train traction rectifier with upset conditions. By treating the multidimensional adverse states as changes of a single faults evolution factor, we build a reduced dimensional MIMO evolution model satisfying persistently exciting condition. In the presence of coupled faults, a nominal feed-forward controller guarantees the reliability of the closed-loop stability. Then, a fast proportional integral fault estimator is employed to predict the system resilience within a few microseconds. Under system uncertainties, a fault tolerant control scheme, including a unified robust adaptive controller, is designed to enhance the reliability. Applying the conditions of the globally asymptotically stability, the convergence of the resilient system is rigorously proved. A case study is performed to verify the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Differential-type (D-type) iterative learning control (ILC) is a typical control method for repetitive operating nonlinear systems and has been used for speed tracking of high-speed train (HST). However, the derived $\lambda $ -norm convergence property of the D-type ILC may lead to unsafe operation of the HST since huge overshoot phenomenon of tracking errors in the iteration axis may occur. To address this problem, this paper presents a novel dynamic modeling and norm optimal iterative learning control (Dynamic modeling based NOILC) approach. By making full use of the valuable information data generated after each repetitive operation of the HST, a modified iterative learning recursive least squares algorithm is proposed to identify the unknown and time-varying even fast time-varying aerodynamical coefficients in the nonlinear train dynamic model. Then, based on this identified nonlinear train model, a norm optimal iterative learning control with consideration of security, punctuality, and traveling comfort will be designed. Through theoretical analysis, reliable 2-norm convergence of both the model identification error and the tracking control error can be guaranteed. Simulation and experimental studies further verify that the proposed approach achieves a significant improvement in tracking control precision and meanwhile obeys safety requirement. [ABSTRACT FROM PUBLISHER]

The downlink communication channel from high-altitude platform (HAP) to high-speed train (HST) in the Ka-band is a slowly time-varying Rician distributed flat fading channel with 10-25 dB Rician K factor. In this respect, the received signal is mainly affected by the Doppler shift of the line-of-sight (LOS) link. In order to increase receiver performance, we propose to firstly compensate the Doppler shift of the received signal before least-squares (LS) adaptive filtering is pursued. Implementing the proposed method requires a priori knowledge of the time-varying phase of the LOS component. This is justified since signalling between the train and the controller exists such that the train velocity and location are predictable. Implementing the proposed method to the recursive LS (RLS) received beamforming algorithm shows reduction of mean square error (MSE) and bit error rate (BER).

It is well known that the train nose shape has significant influence on the aerodynamic characteristics. This study explores the influence of four kinds of nose shapes (fusiform, flat-broad, bulge-broad, ellipsoidal) on the aerodynamic performance of two opposing high-speed trains passing by each other through a tunnel at 250 km/h. The method of three dimensional, compressible, unsteady Reynolds-averaged Navier-Stokes equations and RNG k-ε double equation turbulence model was carried out to simulate the whole process of two trains passing by each other inside a tunnel. Then the pressure variations on tunnel wall and train surface are compared with previous full-scale test to validate the numerical method adopted in this paper. The assessment characteristics, such as transient pressure and aerodynamic loading, are analyzed to investigate the influence of nose shape on these assessment parameters. It is revealed that aerodynamic performance of trains which have longitudinal nose profile line B (fusiform, flat-broad shape) is relatively better when passing by each other in a tunnel. The results can be used as a guideline for high-speed train nose shape design. [ABSTRACT FROM AUTHOR]

The voltage fluctuation between the train body (TB) and the train’s wheel axis (TB voltage fluctuation for short), might cause electromagnetic interference (EMI) on brake control unit (BCU) speed sensor in some high-speed trains (HSTs), which may cause faulty measurement of train speed and incorrect operation of train door. Using a relevant event that occurred in China railways high-speed 380CL-type train as case study, this paper presents an evaluation scheme for the EMI influence of TB voltage fluctuation on the speed measurement of BCU speed sensor. First, the EMI channels are researched, and a model representing the relation between TB voltage and voltage signal reflecting measured speed is deduced. Second, an evaluation scheme for speed measurement influenced by EMI is designed on this basis, where TB voltage and voltage signal reflecting measured speed are taken as the input and the output of model, respectively. The evaluation aimed at EMI is realized by judging the correctness of model output. Later, a real-life experiment is performed in the Chinese Nanjing station to verify the validity and feasibility of evaluation scheme. Last, some application studies are made to evaluate the presented scheme under multiple specific conditions, such as different TB contact conditions or different train speeds. The comparison results illustrate that the scheme can not only provide an opportunity to judge the correctness of speed measurement under the premise of collecting TB voltages, but also provide references in taking timely measures to prevent faulty speed measurement such as weakening TB voltage fluctuations. [ABSTRACT FROM PUBLISHER]

This paper investigates the reliable dissipative control problem for high-speed trains (HSTs) under probabilistic time-varying sampling with a known upper bound on the sampling intervals. In particular, random variables obeying the Bernoulli distribution are considered to account for the probabilistic time-varying delays. Based on Lyapunov–Krasovskii functional approach which considers full use of the available information about actual sampling pattern, a new set of sufficient condition is established to guarantee that the HST can well track the desired speed and the relative spring displacement between the two neighbouring carriages is asymptotically stable and the corresponding error system is strictly-dissipative. The existence condition of the dissipativity-based reliable sampled-data controller is obtained in terms of a set of linear matrix inequalities which are delay-distribution-dependent, i.e. the solvability of the condition depends on not only the variation range of the delay but also the probability distribution of it. Moreover, different control processes for the HST system can be obtained from the proposed design procedure and hence it can reduce the time and cost. Finally, the effectiveness and benefits of the proposed control law is demonstrated through a numerical example by taking the experimental values of Japan Shinkansen HST. [ABSTRACT FROM PUBLISHER]

Excessive vertical and lateral motion of the train body could endanger the operation safety of a high-speed train. The situation is further complicated if actuation faults occur. This paper investigates a semiactive approach for suppressing such motions. By using the structural properties of the system model, a new control scheme is proposed to account for various factors such as input nonlinearities, actuator failures, and external disturbances in the system simultaneously. The resultant control scheme is capable of automatically generating the intermediate control parameters and literally producing the PD-like controller—the whole process does not require precise information on system model or system parameter. Furthermore, unlike traditional PD control, the proposed one has the stability-guaranteed algorithms to self-adjust its PD gains and there is no need for human tuning or trial and error process. Such user-friendly feature is deemed favorable for practical implementation. The effectiveness of the proposed controller is tested using computer simulations in the presence of parametric uncertainties and varying operation conditions. [ABSTRACT FROM AUTHOR]

The proliferation of the voltage-source converter-based high-speed trains has resulted in significant distortions in voltage and current waveforms in both traction power supply system and the utility system. The dynamic behaviors of the high-speed trains (HSTs) make the assessment of such power-quality (PQ) problems quite difficult. There is an urgent need for techniques that can quantify the collective PQ impacts of modern trains during a 24-h period. Dynamic behavior modeling of the modern trains during the operating duty period between two station stops is studied here for PQ assessment. The 24-h profiles of the train timetable and rail infrastructure are entered to compute the information, including train positions, speeds, power consumptions, etc. Moreover, six sets of the measurement-based Norton-equivalent model under different operations are implemented to represent the dynamic harmonic behaviors of the train. In addition, the systemic modeling of the utility system, traction lines, and Scott-connection transformer is also described. After comparing the results of calculations and measurements, the proposed model is ideally effective for analyzing the consequences of HST's dynamic behavior and system topology that are involved in fundamental power flow and harmonic power flow in order to evaluate the comprehensive PQ impacts in a companion paper. [ABSTRACT FROM AUTHOR]

Unilateral vertical noise barrier (UVNB), bilateral vertical noise barrier (BVNB) and fully enclosed noise barrier (FENB) are widely used along high-speed railways. The running safety of a high-speed train (HST) faces challenges when entering and exiting a noise barrier in crosswind. A series of computational fluid dynamics numerical simulations of train-noise barrier-crosswind based on the improved delayed detached eddy simulation model and 'mosaic' mesh technology are conducted. The influence of different noise barrier types on the aerodynamic load of the carriage is studied. Three buffer structures with different lengths are designed to alleviate the deterioration of aerodynamic performance of HST. Results shows that: The amplitudes of the lift force of the tail car, the lateral force and pitching moment of the head car in the BVNB are the largest, and the amplitude of the yawing moment of the head car in the FENB is the largest. Considering the engineering effects and economic benefits, a buffer structure with a length of six times head car length with a gradual ventilation rate is recommended for project, and the reduction rates of the change rates of the lift and yawing moment are 62.8% and 76.4%, respectively. • Aerodynamic characteristics of trains passing difference noise barriers are compared. • The graded air permeability end structures of three types of noise barriers are designed. • The buffer performance of end structures in noise barriers are analyzed. [ABSTRACT FROM AUTHOR]