High-speed Electric Multiple Unit Research Articles

Experimental study of bogie instability monitoring and suppression measures for high-speed EMUs

As the key part of the rail vehicle, the bogie’s dynamic performance directly affects the vehicle’s operating performance. A large number of bogie instability phenomena occur during the operation of high-speed Electric Multiple Units (EMUs), which has an important impact on the safety and passenger comfort of the high-speed EMUs. In this paper, through a combination of line tests and simulations to study bogie hunting, line tests are first conducted to test the vibration data and wheel wear evolution of the high-speed EMUs. The data was analyzed to find out the evolution of the bogie instability law of the high-speed EMUs. Then the vehicle dynamic model is established to find out the mechanism of the bogie instability, and finally bogie instability suppression measures are proposed. The results of the test data showed that the wheel wear, the frequency and the amplitude of bogie instability of motor car is greater than that of the trailer car, and the ride index is poorer. The ride indexes at the early and late stages after wheel re-profiling do not exceed 2.5. The equivalent conicity increase is the main cause of bogie instability, and the bogie instability can be effectively suppressed by wheel re-profiling, replacing the yaw damper, and the rail grinding.

Terahertz-Based Insulation Delamination Defect Inspection of Vehicle Cable Terminals

Cable terminals of the high-speed electric multiple units (EMUs) are prone to undertake insulation delamination defects due to their special operating conditions. Such a defect is difficult to identify and it may pose a great threat to the safety of the EMUs. To achieve accurate detection of insulation delamination defects, this article proposes a terahertz (THz)-based approach that combines the spectrum of the THz wave and THz imaging techniques. Specifically, a synthetic multilayer composite insulation structure with an air gap is firstly built to simulate the internal delamination defect of the cable terminal. Then THz tests in both time and frequency domains are performed on the synthetic structure. Experimental results show that the delamination defect of the multilayer insulation structure can be quickly detected by observing the absorption spectrum in the THz frequency domain. The location and geometry of the defect can be preliminarily determined by the THz imaging and then further refined through image segmentation. In addition, the thickness of the delamination defect can be quickly calculated by the THz time-domain spectrum (TDS). By combining the THz spectrum and the THz imaging information, the delamination defects are quantitatively detected for the multilayer composite structure or even for the EMU’s cable terminals.

Numerical Simulation and Analysis of Turbulent Characteristics near Wake Area of Vacuum Tube EMU.

Due to aerodynamic resistance, aerodynamic noise, and other problems, the further development of traditional high-speed electric multiple units (EMUs) on the open line has been seriously restricted, and the construction of a vacuum pipeline high-speed train system has become a new solution. In this paper, the Improved Detached Eddy Simulation (IDDES) is used to analyze the turbulent characteristics of the near wake region of EMU in vacuum pipes, so as to establish the important relationship between the turbulent boundary layer, wake, and aerodynamic drag energy consumption. The results show that there is a strong vortex in the wake near the tail, which is concentrated at the lower end of the nose near the ground and falls off from the tail. In the process of downstream propagation, it shows symmetrical distribution and develops laterally on both sides. The vortex structure far from the tail car is increasing gradually, but the strength of the vortex is decreasing gradually from the speed characterization. This study can provide guidance for the aerodynamic shape optimization design of the rear of the vacuum EMU train in the future and provide certain reference significance for improving the comfort of passengers and saving the energy consumption caused by the speed increase and length of the train.

Study on Aerodynamic Drag Reduction at Tail of 400 km/h EMU with Air Suction-Blowing Combination

In order to further reduce the aerodynamic drag of High-speed Electric Multiple Units (EMU), an active flow control drag reduction method combining air suction and blowing is proposed at the rear of the EMU train. A numerical calculation method based on realizable k-ε is used to investigate the aerodynamic drag characteristics of a three-car EMU with a speed of 400 km/h. The influence of different suction-blowing mass flow rates, the position and number of suction and blowing ports on the aerodynamic drag and surface pressure of the EMU tail are analyzed. The results demonstrate that suction and blowing at the tail reduce the pressure drag of EMU. And with the growth of air suction-blowing mass flow rate, the aerodynamic drag reduction rate of the tail car gradually increases, but the increment of drag reduction rate gradually decreases. Under the same mass flow rate of the suction and blowing, the closer the ports are to the upper and lower edges of the windscreen, the lower the pressure drag of the tail car is. At the same flow flux of air suction and blowing, the more the number of ports, the better the pressure drag reduction effect of the tail car. This study provides a reference for the next generation of EMU aerodynamic drag reduction and is of great significance for breaking through the limitations of traditional aerodynamic drag reduction.

Modeling and Experimental Analysis of Overvoltage and Inrush Current Characteristics of the Electric Rail Traction Power Supply System

High-speed EMUs (electric multiple-units) frequently pass through the phase-separation zone during operation. Overvoltage generated during the operation of the vehicle-mounted circuit breaker has a long duration and high waveform steepness, which accelerates the service life of the vehicle-mounted equipment and is likely to cause insulation failures. For the above-mentioned problems, the operating overvoltage characteristics of high-speed EMU were obtained by traction substation-catenary-EMUs system (SCES) analysis and experiments, thus deriving the influences of the closed phase angle and the residual magnetism of the vehicle-mounted transformer on operating overvoltage. The results showed that the voltage phase of the catenary significantly affected the operating overvoltage, and the closed switching overvoltage was small at 0–40°, 140–210° and 320–350°. The voltage on the primary side of the vehicle-mounted transformer was 60.78 kV, with the transient impact of high-frequency oscillation overvoltage of 22.71 kV, and an initial period of oscillation of 0.01 ms. Then, the period became longer, and it took 0.5 ms for the high-frequency oscillation from attenuation to disappearance. Finally, a scheme of series reactance suppression devices was proposed to protect vehicle-mounted voltage transformers. This work is to provide data support for the insulation design and system protection of a traction power supply system.

Investigations on lubrication characteristics of high-speed electric multiple unit gearbox by oil volume adjusting device

Investigations on lubrication characteristics of high-speed electric multiple unit gearbox by oil volume adjusting device

Investigations on lubrication characteristics of high-speed electric multiple unit gearbox by oil volume adjusting device

Investigations on lubrication characteristics of high-speed electric multiple unit gearbox by oil volume adjusting device

Analysis and Control of Abnormal Vibration of End Wall on High-Speed Electric Multiple Units

In view of the abnormal vibration of the body end wall during the high-speed operation of electric multiple units (referred hereafter as EMU), the vibration and noise characteristics of the body end wall area are analyzed through the line test. Combined with the end wall modal simulation results, the generation mechanism of the abnormal vibration of the body end wall is analyzed. The results show that when the train is running at a high speed, the aerodynamic excitation of the windshield cavity outside the body end wall acts on the end wall, arousing the first-order bending natural frequency of the body end wall, resulting in resonance of the body end wall, and then causing abnormal vibration and noise in the body end wall area. In order to solve this problem, installing a deflector (guiding plate) above the windshield in the vehicle body end wall area can effectively suppress the aerodynamic excitation acting on the vehicle body end wall. After optimization, the abnormal vibration and noise in the vehicle body end wall area are significantly reduced. The corresponding peak value at 40 Hz of the vehicle body end wall vibration spectrum is reduced by 85%, and the peak noise is reduced by 12%, The correctness of the mechanism analysis of abnormal vibration in the headwall area is verified, which provides a reference basis for guiding the structural optimization and operation and maintenance of rail vehicles.

High-speed electric multiple unit trains and tourism in China: service quality impact on passenger satisfaction and loyalty

ABSTRACT This study aimed to measure the service quality of China’s high-speed electric multiple unit (EMU) trains and examine empirically the correlations among service quality, passenger satisfaction, and loyalty. Using a service quality scale developed based on passenger ticket, inbound, waiting, boarding, and outbound data, a survey was conducted in southeast China with 615 respondents. Using exploratory factor analysis, mean value, and correlation analysis, the authors constructed a multiple regression analysis model of high-speed EMU train service quality, passenger satisfaction, and loyalty. The results indicate that passengers were most satisfied with inbound service, followed by outbound and boarding services. They registered lower satisfaction with ticket and waiting services. The average mean values showed that passengers were most satisfied with the ID card swiping service and least satisfied with the free Wi-Fi service in waiting rooms. In addition, ticket, inbound, boarding, and outbound services exerted a valid positive impact on passenger satisfaction and loyalty. These discoveries demonstrate that passenger satisfaction partially mediates the influence of the service quality of high-speed EMU trains on loyalty. Recommendations are made to improve the service quality of China’s high-speed EMU trains to enhance tourism in China, particularly in the four surveyed cities.

Impacts of Attention Level on Manual Take-Over Performance in Automatic Driving on High-Speed Railways

At the present early stage of application, automatic train driving systems still require constant supervision by the driver, and the continuous attention level of the driver is very important. This study investigated the changes in drivers’ concentration’ levels during the automatic driving of a high-speed EMU (electric multiple units) train, as well as the influence of their attention on take-over performance when necessary. It was found that the degree of concentration decreased over time, with the inattention degree ranging from 20% to 57%. Attention was weakly correlated to the take-over time and strongly correlated to the stable running time. When drivers inattention degree was controlled between 20% and 33%, their response speed to a take-over request might be improved, but inattention would affect their judgment of braking power after a take-over. When the inattention degree was over 33%, all take-over performances became worse.

Reliability of high-speed electric multiple units in terms of the expanded multi-state flow network

This paper proposes a new reliability assessment method for a high-speed electric multiple unit (HSEMU) system based on the expanded multi-state flow network. An HSEMU system is abstracted as a multi-layer multi-source multi-commodity multi-state flow network (M-LSCSFN), where minimum maintenance units (MMUs) and three types of connections form nodes and edges in different layers, and functional characteristics are regarded as network parameters. In the M-LSCSFN, multi layers describe different types of connections and their relationships; multi-source and multi-commodity reflect system features; whereas multi-state flow indicates the dynamic realization of system functions. Considering that an HSEMU system can be divided into multiple independent holistic functions, each holistic function has a corresponding sub-M-LSCSFN, and each layer of this sub-M-LSCSFN is a multi-source multi-commodity multi-state flow network (M-SCSFN). In order to assess system reliability, layer reliability (i.e., the M-SCSFN reliability) is first defined as the probability that the amounts of each commodity transmitted successfully from source nodes to sink nodes will not be less than the required demands. A corresponding algorithm is proposed to calculate layer reliability in terms of minimal paths (MPs) using the quick inclusion-exclusion technique (QIE). The sub-M-LSCSFN reliability is subsequently calculated based on the layer reliability and the conditional relationships among different layers. Based on these, the HSEMU system reliability is defined as the ability of a system to complete specified multiple functions under stated conditions for a specified period of time, and can be evaluated using the reliability of sub-M-LSCSFNs via the proposed operator. Finally, a case study of the “Fuxing” HSEMU system is analyzed to demonstrate the applicability of the proposed method and algorithm the effectiveness of the proposed method is demonstrated in an HSEMU system reliability assessment case study.

Energy Consumption Analysis of High-Speed Trains under Real Vehicle Test Conditions

The study collected statistics on the actual operation of national railway electric multiple units (EMUs) and compared the energy consumption of different EMU models at different speed levels. An important method for studying the relationship between speed and energy consumption of EMUs has been constructed based on group method of data handling to reflect how the energy consumption of different EMU models changes with speed. The energy consumption of CRH2 and CRH380A EMUs on flat and sloping lines was compared. Moreover, the start-up energy consumption of CRH2 and CRH380A EMUs was compared. The effect of the number of stops of CRH2 and CRH3 EMUs on energy consumption was analyzed. Furthermore, an idea for improving the general expression and calculation methods of traction energy consumption of EMUs was proposed. Finally, suggestions on the construction of a traction energy consumption information system were provided, and the selection of different high-speed EMU models and the reasonable determination of the operating speed were discussed.

Research on Target Defect Detection Based on Machine Vision

Abstract The daily detection of highspeed electric multiple units (EMU) body is very important for China railway maintenance system. This paper proposes a new method based on machine vision to detect bolts and switches on EMU side skirt, which aims to replace manpower. Yolov3 network is used to identify and locate bolts and switches. After positioning, the status of bolts is detected through Alexnet network. Experiments show that the processing method can achieve the detection work efficiently and accurately. It is suitable for many cases such as insufficient illumination and non-vertical shooting of image samples, which has high robustness.

Modeling Method for Thermal Field of Turbulent Cooling Dry-Type On-Board Traction Transformer in EMUs

Adopting dry-type on-board traction transformer (OBTT) is one of the main ways to reduce the weight of electric traction systems, and its thermal characteristics are crucial for the safe operation of high-speed electric multiple units (EMUs). However, the existing thermal modeling methods either cannot realize the fast calculation of thermal characteristics of dry-type OBTT, or cannot accurately obtain the turbulence heat-transfer intensity when using the high-speed train-induced wind cooling. This article proposes an efficient method for dry-type OBTT thermal characteristics calculation. First, the thermal network of the winding area is proposed considering the thermal developing region of the air duct and the heat flow in the insulation paper between conductors. Then, the effects of key parameters on convective heat-transfer intensity are obtained by computational fluid dynamics (CFD) parametric sweeps, and then a novel local Nusselt number correlation for accurately calculating the turbulent convective thermal resistance is proposed. Finally, validation is performed with an experimental setup. The experimental results show that the computationally efficient thermal network model proposed in this article can quickly obtain the winding temperature distribution and the location of the hot-spot temperature. Moreover, the thermal analysis of a 6.3 MVA dry-type OBTT was conducted using the proposed modeling method.

Active Vibration Control of Railway Vehicle Car Body by Secondary Suspension Actuators and Piezoelectric Actuators

Active vibration suppression of high-speed electric multiple unit (EMU) car bodies was studied by the combined use of secondary suspension actuators and piezoelectric actuators. A vertical dynamics model was established considering secondary suspension actuators and piezoelectric actuators. The positions of the piezoelectric actuators and sensors were optimized using <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> norms. The feedback controller was designed using a robust optimal control method. The effects of the vibration devices and active control methods on the vehicle dynamic performance were simulated using MATLAB. The dynamic performance differences among the passive suspension vehicle, secondary vertical actuator installation vehicle, and active vibration control vehicle were compared and analyzed. The results show that the piezoelectric actuators and piezoelectric sensors were arranged at distances of 7.15, 12.25, and 17.35 meters from the left end of the car body, and the normalized <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> norms of the first and second order elastic modes of the car body were the largest, which can be used as piezoelectric actuators and sensor placement positions. Secondary suspension actuators can reduce rigid car body vibrations, and piezoelectric actuators can reduce elastic vibration. The higher the speed, the better is the acceleration suspension effect. When the vehicle speeds were 200 km∙h <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and 350 km∙h <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , the vehicle vibration acceleration decreased by 10% and 18%, respectively. Compared with the passive suspension system, the active vibration suspension system with a robust controller can reduce the rigid and elastic vibrations of the vehicle and improve ride comfort.

A testing method with steep impact voltage inspecting the internal defects in EMU roof cable termination

A high-voltage cable terminal on the roof of a high-speed electric multiple unit operates in an intermittent impact load environment. The internal defects of the cable terminal are accelerated and are likely to cause insulation failure. Therefore, in this study, a steep impact voltage method is proposed to identify defective cable termination and establish a thermal and electric field model of the cable termination to analyse the defect development process. The results demonstrated that the interface performance of the cable terminal decreased after operation, and the internal insulation broke down under a steep-wave impulse voltage. Under the operating voltage, there was an electric field concentration at the interface between the stress layer and the insulation layer of the cable terminal that can cause partial discharge within the defect located in this part. The thermal field distortion at the cable terminal joint was obvious, and the resulting air gap reduced the interface performance. Field distortion aggravates the insulation damage under frequent thermal shock and causes insulation accidents. This study provides an experimental reference and theoretical basis for the design and operation of cable terminations.

Optimal design of noise reduction and shape modification for traction gears of EMU based on improved BP neural network

Under high-speed operating conditions, the noise caused by the vibration of the traction gear transmission system of the Electric Multiple Units (EMU) will distinctly reduce the comfort of passengers. Therefore, analyzing the dynamic characteristics of traction gears and reducing noise from the root cause through comprehensive modification of gear pairs have become a hot research topic. Taking the G301 traction gear transmission system of the CRH380A high-speed EMU as the research object and then using Romax software to establish a parametric modification model of the gear transmission system, through dynamics, modal and Noise Vibration Harshness (NVH) simulation analysis, the law of howling noise of gear pair changes with modification parameters is studied. In the small sample training environment, the noise prediction model is constructed based on the priority weighted Back Propagation (BP) neural network of small noise samples. Taking the minimum noise of high-speed EMU traction gear transmission as the optimization goal, the simulated annealing (SA) algorithm is introduced to solve the model, and the optimal combination of modification parameters and noise data is obtained. The results show that the prediction accuracy of the prediction model is as high as 98.9%, and it can realize noise prediction under any combination of modification parameters. The optimal modification parameter combination obtained by solving the model through the SA algorithm is imported into the traction gear transmission system model. The vibration acceleration level obtained by the simulation is 89.647 dB, and the amplitude of the vibration acceleration level is reduced by 25%. It is verified that this modification optimization design can effectively reduce the gear transmission.

A method for assessing resilience of high-speed EMUs considering a network-based system topology and performance data

The high complexity of the system topology and the uncertainty of threats necessitate the consideration of the resilience of high-speed electric multiple units (EMUs). This paper first gives a definition of high-speed EMU resilience. Then, the structure of a high-speed EMU is described in the form of a network to enable the application of network science for resilience evaluation based on corresponding mathematical expressions. Afterward, a measure of system performance (MSP) is constructed that considers the influence of the high-speed EMU topology and performance data. According to the definition of resilience of a high-speed EMU, a system resilience measurement (SRM) is proposed that comprehensively considers the degree and time of the change in system performance. The validity of our method is then illustrated by applying it to the system topology and performance data associated with the Chinese standard electric multiple units (CEMUs) that serve on high-speed railways in China. Experiments are reported to illustrate the concept of resilience and the procedure for its measurement and to present comparisons with an existing resilience index. Our results indicate that the SRM proposed here can capture the sensitivity of the response of high-speed EMUs to the disturbances, thereby supporting the optimal design and risk management.

Test technology research and fatigue damage prediction of a car body based on dynamic simulation load spectrum

The dynamic model of a high-speed electric multiple unit (EMU) is established based on the theory of rigid-flexible coupling multi-body system dynamics. Depending on the actual operating conditions of the vehicle, there are a variety of conditions of car body load-time history. We assess ineffective amplitude omission, load spectrum extrapolation, and extreme determination through the car body load-time history, and then obtain the car body fatigue load block spectrum. Finally, we perform a fatigue strength test on the whole car body on a car body fatigue test bench. It is shown that the accelerations of the three directions of the vehicle car body increase with increasing speed. When the train passes a curve, the lateral acceleration average becomes greater. There is also an increase in the car body accelerations in three directions when the train goes through a turnout or twisted line. Under the condition of a failed spring, the vertical acceleration of the car body is obviously increased. Anti-yaw damper failure will cause a significant increase in vehicle lateral acceleration. The failure of lateral and vertical dampers on the second suspension causes an insignificant acceleration increase in three directions. The car body acceleration increases the wear-type profile relative to the original profile in various working and speed level conditions a little. The influence on the damage of vehicle car body under various working conditions is predicted according to the obtained load spectrum.

Operational failure analysis of high-speed electric multiple units: A Bayesian network-K2 algorithm-expectation maximization approach

In this paper, a Bayesian Network-K2 Algorithm-Expectation Maximization (BN-K2-EM) approach is proposed to quantify the intensity of coupling influence among the operational failures and find out the specific failure propagation chains in accidents of high-speed electric multiple units, quantitatively. K2 is applied to learn the BN structure because it can effectively learn the structure based on small scale data sets, EM is applied to learn the parameter in BN because it can accurately reflect the probability value among nodes with fast convergence speed. BN-K2-EM belongs to a data-driven method which overcomes the limitation of the logic-based BN approach. BN-K2-EM has 6 steps: establish the failures data matrix; determine the priority of nodes priority based on expanded average causal effect; learn the structure of BN based on K2 algorithm; learn the parameter of BN based on EM algorithm; causal reasoning and predication; reverse reasoning and diagnosis. Finally, a case study is conducted by using the historical high-speed EMU accidents happened in China from 2008 to 2019 as background. The influence strength and sensitivity of each failure mode in the case study are analyzed, and the sensitivity analysis of nodes in each system or sub-system is also conducted.