交通运输工程学报

Cover and Contents of Vol.24, No.2, 2024

Cover Contents

Review on ship-based carbon capture, utilization and sequestration technology

LU Ming-jian, DONG Sheng-jie, YAN Xin-ping, LI Ke, LI Xiao-dong, ZHOU Xiao

Abstract: The researches on ship-based carbon capture, utilization, and sequestration (CCUS) technology conducted in both China and abroad were tracked, and key contents and main research results were sorted out. Based on the advantages and disadvantages of different CCUS technology paths, the application feasibility of current CCUS technology on ships was analyzed. The technical route to carry out CCUS was proposed for the rapidly developing liquefied natural gas ships. The problems existing in current ship-based CCUS technology were summarized, targeted recommendations were put forward, and development direction of key ship-based CCUS technology was discussed. Research results show that the ship-based CCUS technology can significantly reduce emissions in short term and is applicable to the vast majority of carbon-fueled ships, including those in operation and the newly constructed. Foreign countries are actively deploying the ship-based CCUS technology real-ship verification research, but the research in China is mostly at the stage of conceptual design and simulation research. Due to the simple transformation, high technology maturity, and low cost, the chemical absorption method in the post-combustion capture methods is most suitable for the ship-based carbon capture at present. But to solve the problems of high energy consumption and large system sizes, it is necessary to accelerate the exploration of advanced chemical solvents with better performance and more revolutionary capture methods. Liquid storage is currently the most mature storage method, but its safety and economy need improvement. There is an urgent need to accelerate the construction of storage and transportation methods dominated by large CO₂ carriers and to promote the construction of CO₂ transfer and reception infrastructure at ports and marine platforms. CO₂ has great development prospect in oil displacement and gas-freeing in offshore oil-gas fields, seawater desalination, and energy catalytic reforming, but CO₂ utilization technology for ships needs to be scaled up and industrialized and requires synergistic development of related industrial technologies. Marine sequestration of liquid CO₂ or dry ice is the future development trend, but there is an urgent need to improve relevant standards, laws, and regulations to promote the development of sequestration equipment and technology. It is necessary to explore a set of standardized and systematic carbon emission management modes to promote the mutual matching and promotion of CCUS technology and establish a complete, green, economical, and efficient ship-based CCUS industry chain.More>

2024, 24(2): 1-19. doi: 10.19818/j.cnki.1671-1637.2024.02.001

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Review on long-life-oriented life extension design of existing expressway asphalt pavement

LYU Song-tao, ZHAO Pei, LU Wei-wei, PENG Xing-hai, WANG Jin-ping, CHEN Qi, LEI Wei, PU Chang-yu

Abstract: In the face of the demand for long-life expressway construction projects in China, the basic concepts and development histories of long-life asphalt pavements in China, the United States, and European countries were introduced. The research and development status of long-life asphalt pavement design theories and methods in China and European and American countries were summarized. The existing detection and evaluation for asphalt pavements and life extension treatment design methods in European and American countries were combed. The research and development status of life extension design methods for typical existing asphalt pavements in China were discussed. The advantages, disadvantages, and applicabilities of different long-life design methods for newly constructed roads and life extension design methods for existing asphalt pavements were compared and analyzed. Research results indicate that the unified design standard for long-life asphalt pavements is not formed at present. The research and application are still in the stage of development and improvement. Long-life asphalt pavements will still be a hot topic in the field of pavement research in the future. The coupling of traffic and environmental factors to establish a multi-index controlled long-life asphalt pavement design system should be a key research direction in the future. The long-life asphalt pavement structure design will shift towards nonlinear, multidimensional, probabilistic, and dynamic in the future. The life extension design method for long-life asphalt pavements based on the progressively increasing life of structural layers doubles the service life of asphalt pavement structures. The relevant work can provide valuable reference and insight for constructing and applying the life extension design methods and systems for existing asphalt pavements, so as to meet the development needs of long-life highway construction projects in China. The life extension design of existing asphalt pavements is an important subject for the sustainable development of road engineering. In the future, it is necessary to strengthen the research and promotion of long-life asphalt pavement technology, improve the comprehensive quality of pavements, meet the growing demand for road transportation, and make greater contributions to the construction of high-quality, efficient, green, and safe transportation infrastructure.More>

2024, 24(2): 20-49. doi: 10.19818/j.cnki.1671-1637.2024.02.002

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Review on short-term traffic flow prediction methods based on deep learning

CUI Jian-xun, YAO Jia, ZHAO Bo-yuan

Abstract: For the short-term traffic flow prediction problem based on deep learning, the essence of spatiotemporal correlation modeling was revealed, the multi-scale spatiotemporal characteristics, heterogeneity, dynamics, nonlinearity, and other characteristics involved in the modeling process were analyzed, the core challenges were clarified, and the external information integration, multi-step prediction and single-step prediction, as well as individual prediction and integrated prediction were elaborated. The latest research directions were reviewed with two organization methods of traffic flow data: grid and topology. Research results indicate that for gridded traffic flow data, current research mainly includes three prediction modeling methods: 2D image convolutional neural network, 2D image convolutional neural network combined with recurrent neural network, and 3D image convolutional neural network. For topological traffic flow data, current research mainly includes four prediction modeling methods: 1D causal image convolution combined with convolutional graph neural network, recurrent neural network combined with convolutional graph neural network, self-attention combined with convolutional graph neural network, and spatiotemporal synchronous learning of convolutional graph neural network. Overall, the short-term traffic flow prediction based on deep learning methods significantly improves the prediction accuracy compared to time series method and classical machine learning method. In the future, the combination of physics theory, knowledge graphs, and deep learning, the construction of large-scale models for multi-temporal and spatial data mining, as well as the lightweight, interpretability, and automated model structure search, will become important research directions.More>

2024, 24(2): 50-64. doi: 10.19818/j.cnki.1671-1637.2024.02.003

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Review on formation mechanism, detection and prevention of rail squat

HOU Bo-wen, QIAO Lin-chuan, GAO Liang, QIN Jia-dong, LIU Xiu-bo, MA Chao-zhi

Abstract: In view of the problem of rail squat in the operation of railways, the specific morphological characteristics of rail squat such as squat depth, crack propagation angle, and squat size were summarized. The propagation process of rail squat was discussed. The formation mechanism of rail squat was analyzed systematically. The action mechanisms of wheel-rail contact pressure, stress/strain in the contact zone, and temperature change in the contact zone during squat formation were analyzed from the perspectives of plastic deformation and thermal phase transformation. The main factors affecting the development of rail squat were defined from the aspects of locomotive and vehicle performances, line parameters, track types, and other factors. The different field detection methods of rail squat such as axle box acceleration were investigated, and the applicabilities of various methods in squat detection were compared and analyzed. According to the formation mechanism and influencing factors of the squat, the effective measures and strategies for preventing and controlling the squat were analyzed from the perspectives of vehicle traction/braking control and rail grinding. Test results show that at present, the research on the formation mechanism and development process of rail squat mainly adopts the means of field investigation, sample test simulation, and numerical simulation. The ultimate deformation and thermal phase transformation of rail base metal caused by the large creep and sliding state between wheel and rail are the main reasons for the formation of rail squat. The contact state between wheel and rail will be affected by the factors such as train operation state, horizontal and vertical section parameters of the line, and the type of foundation under the line, thus inducing the formation and development of rail squat. According to the detection modes of rail squat, at present, the axle box acceleration response method, frequency response function method, and eddy current detection method can be mainly used, but the detection accuracies of different methods are different for squat to varying degrees. As for the prevention and control of rail squat, it is more effective to control the wheel and rail adhesion overrun in the process of controlling train traction/braking before the formation of squat. The safety hazards can be reduced by grading grinding or changing rail according to the degree of formed squat.More>

2024, 24(2): 65-84. doi: 10.19818/j.cnki.1671-1637.2024.02.004

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Review on wear mechanism and influence of wheel polygon of rail transit train

WU Dan, DING Wang-cai

Abstract: The research results of wheel polygon of rail transit trains in China and abroad in recent years were summarized, the main factors and mechanisms leading to the formation of wheel polygon were analyzed, the reasons for the difference in high-order wheel polygons between electric multiple units (EMUs) and metro vehicles were investigated, the main causes of the difference were summarized. The suppression measures for wheel polygon were discussed, and the generation and development of vehicle-track coupling dynamics model were summarized. At the same time, the main results of the simulation analysis of vehicle-track coupling dynamics were presented, and a new research direction was proposed, which considered the fatigue damage of vehicle-track system components under the periodic wear of wheel-rail such as wheel polygon. Analysis results show that the initial defect of wheel, self-excitation vibration of wheel-rail friction, stick-slip vibration of wheel-rail, P2 resonance of wheel-rail system, inherent mode vibration of wheelset, wheel diameter, and resonance caused by bogie components can cause wheel polygon. The wheel polygons of metro vehicles are mainly caused by the P2 resonance of the wheel-rail system, while the multiple high-order wheel polygons of high-speed EMUs are generally not directly caused by the P2 resonance. Improving the quality of wheel turning, increasing the abrasive block, enhancing the hardness of wheel tread, strengthening the damping of fastener, and applying variable speed running can restrain the development of wheel polygon. However, according to the formation mechanism of wheel polygon, the initial defect of wheel is the origin, and controlling the initial defect of wheel can fundamentally inhibits the formation and development of wheel polygon. From the perspective of feasibility, installing the abrasive block is the most ideal measure. When the wheel has a high-order polygon, the wheel-rail excitation frequency will increase significantly, and the range distribution is wider. When the excitation frequencies are close to the inherent vibration frequencies of some parts of vehicle, the resonance is easily triggered, which will lead to a significant increase in its dynamic stress and affect its fatigue life. Therefore, when the fatigue damage of the main bearing parts of vehicle-track system is analyzed, adverse factors such as random track irregularities and periodic wear of wheel-rail should be considered. It can be seen that the existing research results basically reveal the formation mechanism of wheel polygon, and feasible suppression measures are proposed. However, since the train operation environment is uncertain, there are many related factors in the vehicle-track coupling system, and the analysis process is inevitably different from the actual situation. Therefore, further in-depth research is still needed.More>

2024, 24(2): 85-101. doi: 10.19818/j.cnki.1671-1637.2024.02.005

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Rationality analysis and optimization of guard rail interval and wing rail interval limits at turnouts

WANG Pu, ZHAO Zhen-hua, GE Jing, MA Jun-qi, WANG Shu-guo, LIU Xiao-han

Abstract: Aiming at the derailment problem of the guard rail positions of conventional speed railway turnouts which has occurred several times in recent years, the derailment process and mechanism were studied. The rationalities of current guard rail interval and wing rail interval limits and their calculation methods were analyzed. Systematic field experimental research was conducted at 19 stations and 124 turnouts nationwide, and the optimization method of guard rail interval and wing rail interval limits was discussed. Research results show that the main reason for derailment at the guard rail position of turnout is wheel's impact on the opening section of guard rail, which leads to the loosening of guard rail bolts and the tipping and wear of guard rail, finally causing wheel to climb guard rail and derails. The distributions of guard rail interval and wing rail interval are relatively discrete during the field maintenance, with a low pass rate ranging from 68.97% to 73.83%. The existing wing rail interval limit includes a substantial safety margin, which can be appropriately relaxed to facilitate field maintenance. Compared with the double slip turnout with the same number, the probability of wheel-rail impact at the opening section of guard rail of simple turnout is slightly smaller. As the number of turnouts increases, the probability of impact at the opening section of guard rail decreases. The current guard rail interval limit setting can control the probabilities of wheel impacting the open section of straight guard rail and heel end of lateral guard rail within 12%. However, it cannot effectively prevent the wheel-rail impact at the opening section of the toe end of lateral guard rail with the probability still as high as 53.85%-75.00%. To facilitate maintenance and repair, the guard rail interval limit should be 1 365 mm, which meets the requirements of most turnouts and effectively reduces and avoids the wheel-rail impact at the opening section of the toe end of guard rail.More>

2024, 24(2): 102-111. doi: 10.19818/j.cnki.1671-1637.2024.02.006

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Finite element model correction for ballastless track structure based on multi-chain competition based differential evolution algorithm

YE Ling, JIANG Hong-kang, CHEN Hua-peng, FENG Yu-xuan, WANG Li-cheng

Abstract: To obtain a more realistic track structure model, a finite element model correction method for the ballastless track structure based on a multi-chain competition based differential evolution algorithm was proposed. The objective function and likelihood function suitable for the ballastless track structure were established according to the response of frequency vibration mode. Based on the standard Markov Chain Monte Carlo algorithm, a multi-chain differential evolution algorithm was introduced to solve the problems of low efficiency and difficult convergence in high-dimensional parameter models. Then, the competitive algorithm was introduced, and the mechanism of learning from the winners by the losers determined by the competition was utilized, so as to continuously iteratively correct the track model and thus improve the correction accuracy. On this basis, the efficiency of the proposed method was verified by a numerical example of the finite element model correction of the ballastless track structure. Analysis results show that after correction using the Metropolis-Hastings algorithm and the delayed rejection adaptive Metropolis algorithm, the maximum relative errors between the corrected unit parameters and the true values are 4.75% and 1.35%, respectively. However, the maximum relative error between the corrected unit parameters and the true values is 0.28%, after correction using the multi-chain competition based differential evolution algorithm. In addition, the correlation between vibration mode vectors is close to 1, indicating that the correction accuracy of the multi-chain competition based differential evolution algorithm is better than the other two algorithms. In the noise tests with 5%, 10%, and 15% noise, respectively, the parameter errors reach about 9% after corrected by the Metropolis-Hastings algorithm and the delayed rejection adaptive Metropolis algorithm, while those corrected by the multi-chain competition based differential evolution algorithm are all within 5%. It further proves the good robustness of the multi-chain competition based differential evolution algorithm. Therefore, the multi-chain competition based differential evolution algorithm can provide a new method for correcting the finite element model of ballastless tracks with incomplete testing information caused by complex environments.More>

2024, 24(2): 112-124. doi: 10.19818/j.cnki.1671-1637.2024.02.007

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Foundation structure selection of metro stations in Xi'an by PBA method

LAI Hong-peng, MA Xiao-jie

Abstract: Based on the stratum characteristics in Xi'an, the structural bearing characteristics of different foundation types and the most unfavorable working conditions were analyzed, with the five metro stations under construction by the pile-beam-arch (PBA) method as the example. The foundation bearing capacity, horizontal shear resistance, anti-overturning capacity, anti-uplift of the foundation, and allowable horizontal displacement of the structure were selected as the basic criteria for evaluating the structural strength and stiffness safety of the foundation structure. The mechanical model of the foundation structure by PBA method was constructed, and the calculation formulas of the structural safety factors under different failure modes were deduced. Some suggestions on the safety factors values in the type selection theory system of the foundation structure by PBA method in Xi'an were put forward. The application scopes of single-row long pile foundation and strip foundation under the column in different strata and buried depths were given. Research results show that when the foundation structure by PBA method in Xi'an is calculated according to the basic criteria of foundation bearing capacity, horizontal shear resistance, anti-overturning capacity, anti-uplift of the foundation, and allowable horizontal displacement of the structure, the safety factors should be not less than 1.2, 1.3, 1.3, 1.6, and 1.4, respectively. The structure selection of the middle column foundation by PBA method is mainly affected by the vertical bearing capacity criterion of the foundation. When the same column span type is adopted, the applicability of the strip foundation under the column in the sandy soil stratum is better than that in the silty clay-sand interbedded stratum and silty clay stratum. The structural bearing capacity of the single-row long pile foundation can be improved by increasing the pile length. Theoretically, the applicability of the single-row long pile foundation under various stratum conditions is better than that of the strip foundation under the column. The composite criteria should be used to comprehensively analyze the applicability of the side pile foundation structure. The applicability of the strip foundation structure under the column is greatly affected by the stratum condition, and the anti-overturning safety of the structure is difficult to meet the requirements under the conditions of silty clay and silty clay-sand interbedded stratum. However, the single-row long pile foundation is mainly affected by its own structural strength and stiffness under various criteria, and there is no significant difference in the applicable burial depths in various strata. The single-row long pile foundation is more applicable for the metro station in Xi'an by PBA method, while the strip foundation under the column can meet the structural safety requirements by expanding the foundation width.More>

2024, 24(2): 125-136. doi: 10.19818/j.cnki.1671-1637.2024.02.008

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Discrete element virtual triaxial test of ballast penetration into subgrade soil sample

ZHANG Jie, NIE Ru-song, LI Lie-lie, HUANG Mao-tong, TAN Yong-chang

Abstract: The discrete element method (DEM) was used to study the effect of ballast penetration in ballasted tracks on the deformation characteristics of subgrade soil from both macroscopic and mesoscopic perspectives. The shape of ballast particles was reconstructed based on a three-dimensional structured light scanning system, and the refined modeling of ballast particles was realized. Triaxial computational models of a ballast penetration sample and a pure soil sample with a height of 600 mm and a diameter of 300 mm were established based on DEM software PFC 3D V6.0. The finite difference method (FDM) was coupled with DEM to realize the flexible loading of triaxial confining pressure. The simulations of triaxial tests were conducted separately for both samples. The simulation results of the ballast penetration sample and pure soil sample were compared and analyzed to clarify the influence of ballast penetration on the deformation characteristics of subgrade soil. Research results show that at a confining pressure of 30 kPa, the peak strength of the ballast penetration sample is 257 kPa, whereas that of the pure soil sample is 199 kPa. Compared with the pure soil sample, ballast penetration reduces the load bearing capacity of subgrade soil. At shear termination, the volumetric strain of the pure soil sample is -3.24%, while that of the ballast penetration sample is -14.59%, indicating a more pronounced shear dilation effect in the ballast penetration sample. The lateral deformation mechanism of the pure soil sample is different from that of the ballast penetration sample. Bulging deformation in the middle of the pure soil sample occurs because the central region is unconstrained, allowing particles to move freely. The lateral bulging of the surface soil in the ballast penetration sample occurs because ballast penetration at the ballast-soil interface exerts a squeezing action on surface soil particles on both sides. The trend of soil particle coordination number variation is consistent for both types of samples, showing an initial increase followed by a decrease with axial strain and ultimately reaching a plateau. However, the soil particle coordination number of the pure soil sample is significantly higher than that of the ballast penetration sample. The force chains in the pure soil sample develop along the axial direction and are evenly distributed, whereas noticeable contact force concentration occurs at the ballast-soil interface in the ballast penetration sample.More>

2024, 24(2): 137-151. doi: 10.19818/j.cnki.1671-1637.2024.02.009

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Bogie stability and control strategy based on motor suspension

FENG Zun-wei, HU Han-da, YANG Zhen-huan, HUANG Cai-hong, ZHENG Biao, ZENG Jing

Abstract: The motor suspension parameters were adjusted in real time to improve the hunting stability of vehicle bogie. A bogie dynamics model of motor suspension was established, including two wheelsets, one frame, and two motors. The primary suspension device was considered between wheelsets and frame, air springs and anti-yaw dampers were considered for the secondary suspension device between frame and car body, and the two motors were considered as a whole and elastically connected to the frame. Based on the minimum damping ratio of high-speed bogie system model, the optimal lateral frequency of motor was found. The influences of bogie parameters on the optimal lateral frequency of motor were analyzed, and an active motor suspension feedback control strategy was proposed for this type of bogie, so as to improve the hunting stability. Motor suspension control strategy was verified by carrying out a SIMPACK/SIMULINK joint simulation of high-dimensional vehicles with active motor suspension. Research results indicate that the optimal lateral frequency of motor increases with the increase of the equivalert conicity of wheel-rail, when the equivalent conicity of wheel-rail increases from 0.3 to 0.6, the optimal lateral frequency of motor increases from 4.5 Hz to 7.0 Hz. Under different equivalent conicities, motor masses, and primary longitudinal stiffnesses, the difference between the optimal lateral frequency of motor and the hunting frequency of the bogie is within the range of 1.0-1.5 Hz. Therefore, the optimal lateral frequency of motor can be obtained by detecting the hunting frequency of bogie and subtracting 1.0-1.5 Hz. The relative displacement and speed between motor and frame are used as feedback signals to obtain the optimal motor suspension parameters in real time, making it an ideal power absorber. High-dimensional numerical simulations show that compared with the passive motor suspension, the active motor suspension can increase the critical speed of vehicle with wheel worn from 370-380 km·h^-1 to 500-510 km·h^-1, and reduce the lateral acceleration of frame from 2 m·s^-2 to 1 m·s^-2, indicating that the proposed motor suspension control strategy can effectively improve the hunting stability of bogie.More>

2024, 24(2): 152-165. doi: 10.19818/j.cnki.1671-1637.2024.02.010

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Simulation analysis of locomotive gear wear under internal and external excitations

ZHU Hai-yan, WANG Meng-wei, ZHENG Yu-xuan, YI Yong, XIAO Qian, ZENG Jing, ZHANG Wei-hua

Abstract: Based on the Archard wear formula and Hertz contact model, the numerical simulation model of locomotive gear wear considering dynamic wear coefficient was established, and the wear distribution of tooth surface was calculated under ideal condition. The finite element model of gear wear was established by the secondary development of the UMESHMOTION subroutine in ABAQUS and ALE adaptive mesh. After simulation, the tooth surface wear information was extracted by MATLAB, and the results of finite element calculation were compared with those of numerical simulation. The effects of friction factor and center distance error on tooth surface wear were studied by changing the model parameters. Based on the multi-body dynamics software SIMPACK, the vertical vibration displacement of the driven gear under wheel-rail excitation was obtained and loaded into the finite element model for simulation and calculation of tooth surface wear. Calculation results show that the gear wear distributions obtained by the two calculation methods are consistent, or in other words, the maximum wear depths of the driving and driven gears are at the root of the tooth, and the wear depth of the pitch line is 0. The wear depths of the alternating area of single and double teeth on both sides of the pitch line are abrupt. The total wear depth increases with the increase in friction factor, and all of them are located near the root of the tooth, with the pitch line as the boundary. When the maximum friction factor is 0.25, the total wear depth is 3.104×10^-6 mm, while the opposing situation is observed at the tip of the tooth. When the center distance error is negative, the total wear depth increases with the decrease in the center distance, and the maximum value is 3.313×10^-6 mm. However, when the center distance error is positive, the total wear depth changes slightly with the increase in the center distance. Wheel-rail external excitation will aggravate wear at the root of the tooth, affecting gear life and driving safety.More>

2024, 24(2): 166-178. doi: 10.19818/j.cnki.1671-1637.2024.02.011

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Analysis of vehicle vibration transfer characteristics based on flexible vehicle system and OTPA method

GUO Bing-bin, LUO Zhi-xiang, XIAO Qian, CHENG Yu-qi, YANG Yi-hang, ZHU En-hao

Abstract: In order to accurately analyze the vibration characteristics and transfer rules of rail vehicles in the wide frequency domain, a scheme for operational transfer path analysis (OTPA) based on a dynamics simulation model of a flexible vehicle system was proposed. A dynamics model of a flexible vehicle system including flexible wheelsets, frame, and vehicle body, as well as a rigid body model with identical structural parameters was established. The vibration characteristics of the wheelset, frame, and vehicle body were studied from the perspective of time domain. The simulation results were compared with the measured data to explore the effect of flexible treatment on vehicle vibration. The attenuation law of vibration energy was obtained. Meanwhile, the vibration characteristics of the flexible vehicle system under the excitation of measured vertical irregularities of steel rails were investigated from the perspective of the frequency domain. The OTPA method was used to simulate and analyze the main transfer path of vertical vibration in the bottom-up vibration transfer process of the vehicle system from wheelset to frame and vehicle body under complex condition of vertical irregularities of steel rails combined with wheel polygon. Research results indicate that the flexible treatment method of the vehicle system has a significant impact on vehicle vibration. Compared with the rigid body model, the vibration accelerations of wheelsets, frame, and vehicle body in the flexible vehicle system model are closer to measured values in the mid-to-low frequency range. The maximum vibration amplitudes of axle box, frame, and vehicle body are 250-450, 30-40, and 3-4 m·s^-2, respectively. The vibration amplitude attenuates by an order of magnitude from the wheelsets to the frame and vehicle body. The sperling index of the flexible vehicle system model is greater than that of the rigid body model, and the trend becomes more obvious as the speed increases. The impact of a vehicle's flexible vibration on the operational performance increases with the increase in speed. Under complex working conditions, the vibration of the vehicle system is mainly transferred to the frame through a series of steel springs, and then transferred to the interior floor through air springs and traction rods.More>

2024, 24(2): 179-192. doi: 10.19818/j.cnki.1671-1637.2024.02.012

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New calculation method for anti-skid efficiency based on deceleration envelope correction

ZHAI Geng-wei, TIAN Chun, MA Tian-he, CHEN Chao, WANG Guo-zhuang

Abstract: To solve the problems of low accuracy and poor evaluation effect of existing anti-skid efficiency calculation methods, based on the in-depth analysis of change rules and characteristics of wheel-rail adhesion coefficient during the train braking anti-skid process, the peak deceleration envelope in the train braking anti-skid process was corrected to make it close to the ideal deceleration curve. Then, a new anti-skid efficiency calculation method was proposed. Combined with the actual working principles of train braking anti-skid systems, a simulation verification platform for the train braking anti-skid efficiency was built. The correctness of the deceleration envelope correction and the accuracy of the new anti-skid efficiency calculation method were verified at the simulation level. The rationalities and the anti-skid performance evaluation effects of six anti-skid efficiency calculation methods were compared and analyzed under different simulation conditions, and the practical applicability of the new method was verified based on the real vehicle anti-skid test. Research results show that the relative errors of braking time and braking distance between the simulation verification platform for train braking anti-skid efficiency and the actual vehicle anti-skid test results are less than 5% under the same condition. Therefore, the platform can be used to verify and analyze the anti-skid efficiency calculation method and the anti-skid performance evaluation effect. The relative error between the corrected peak deceleration envelope and the ideal deceleration curve does not exceed 4.5%. When the anti-skid control strategy remains unchanged, the simulation results of the new anti-skid efficiency calculation method for trains differ by less than 1.1% under different braking levels and adhesion levels. The test results differ by less than 3.5% under the above conditions. The anti-skid efficiencies are all less than 100%. The above results demonstrate good stability of the method. When different anti-skid control strategies are adopted, the simulation results have obvious differences based on the new anti-skid efficiency calculation method, and the corresponding anti-skid efficiencies of different control strategies are positively correlated with their anti-skid performance. The performance differences among different anti-skid systems can be reflected. The new anti-skid efficiency calculation method can calculate the anti-skid efficiency through real vehicle anti-skid tests, providing a new evaluation means of the anti-skid performance for real vehicles.More>

2024, 24(2): 193-206. doi: 10.19818/j.cnki.1671-1637.2024.02.013

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Self-organizing method for traffic coupling between adjacent ramps in intelligent and connected environments

MA Qing-lu, WANG Xin-yu, ZHANG Shu, DUAN Xue-feng

Abstract: A self-organizing method for traffic coupling between adjacent ramps was proposed to improve traffic safety and efficiency in on-ramp merging areas in intelligent and connected environments. By establishing an optimal matching model between the mainline traffic flow gap and on-ramp vehicle speed, the overall headway of the outermost lane of the mainline was optimized and adjusted. On the premise of ensuring the safe merging of on-ramp vehicles, the traffic efficiency of vehicles between adjacent ramps was improved. Two adjacent ramps near the Donghuan overpass on the inner ring expressway in Chongqing were selected as the research prototype. Online map combined with drone aerial photography, fixed-point photography, and other data acquisition methods were used to conduct field investigations on the testing sections. In intelligent and connected environments, cooperative adaptive cruise control (CACC) and traffic coupling self-organizing (TCS) method were applied respectively, and Python, SUMO, and TraCI were used for co-simulation of vehicle operation on the test road. Research results show that compared with CACC, the lane changing number in TCS decreases by 19.87% from 65.52 to 52.64, which effectively alleviates the traffic conflict between adjacent ramps. The average delay decreases by 70.38% from 24.53 s to 14.39 s. To be specific, the average delay decreases by 77.71% in the off-peak period and 34.50% in the peak period, respectively. Compared with the peak period, the efficiency in the off-peak period is greatly improved. The time occupancy decreases by 53.86% from 18.70% to 8.63%. The time occupancy difference between different lanes decreases to 6.00%, that is, vehicles are more evenly distributed across different lanes. The average speed increases by 3.06% from 78.31 km·h^-1 to 80.78 km·h^-1, which effectively alleviates the deceleration near the on-ramp merging and off-ramp diverging areas.More>

2024, 24(2): 207-220. doi: 10.19818/j.cnki.1671-1637.2024.02.014

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Optimization of subway freight compartment configuration and loading based on flexible time windows

SHI Jun-gang, WANG Song, GUO Jun-hua

Abstract: The utilization of subway lines for freight transportation during off-peak hours was suggested as a way to reduce the urban traffic congestion and enhance the turnover effectiveness of urban logistics systems. Based on the passenger and cargo co-load transportation mode, under the premise of meeting the travel needs of passengers, the maximum number of freight compartments that could be loaded on each train was calculated, and on this basis, the configuration and loading scheme of freight compartments was optimized. Train freight compartment configuration plan and freight loading allocation scheme were taken as decision variables. Considered the constraints of flexible time windows and capacity constraints for freight delivery, an integer linear programming model was constructed with the goal of minimizing delivery service penalties and freight compartment loading costs, and solved using CPLEX optimization software. Experimental results indicate that the scheme is configured with 42 freight compartments to meet the needs of 4 types of freight transportations with different delivery time limits, and the total operating cost is 16 970 yuan. As the penalty coefficient for delayed delivery increases, the rate of delayed delivery of freights decreases rapidly. When the penalty coefficient for delayed delivery increases from 5 yuan·h^-1 to 100 yuan·h^-1, the rate of delayed delivery decreases from 22.50% to 8.75%. As the penalty coefficient for advance delivery increases, the advance delivery rate of freights also shows a rapid decreasing trend. When the penalty coefficient for advance delivery increases from 0 to 40 yuan·h^-1, the advance delivery rate reduces from 37.50% to 3.75%. It indicates that the built model is sensitive to the time of freight delivery and can effectively meet the requirements of freight for service timeliness. When the penalty coefficient for a certain type of freight increases, the advance or delay rate of the freight delivery will decrease, showing that the overall performance of the on-time delivery of freights increases and the service level improves. This indicates that the optimization model is more sensitive to the penalty coefficients of delivery of different types of freights. As the passenger load factor increases, the on-time rate of freight delivery shows an increasing trend, the advance and delay rates of freight delivery show an overall decreasing trend, and the total operating cost of the scheme shows a decreasing trend. This indicates that increasing the passenger load factor threshold can alleviate the capacity constraints on certain trains and improve the on-time rate of freight delivery.More>

2024, 24(2): 221-231. doi: 10.19818/j.cnki.1671-1637.2024.02.015

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Evaluation of airport intelligence degree based on zero-subjective relative algorithm

ZHANG Rui, HUANG Wei, MA Tao

Abstract: To solve the issues such as various indicators, wide coverage, complex relationships among indicators, and non-uniform dimensions encountered in the evaluation process of airport intelligence degree, which make it difficult to conduct quantitative analysis, the traditional evaluation methods were optimized, and the improved technique for order preference by similarity to an ideal solution (TOPSIS) method was integrated with the analytic hierarchy process (AHP). Then, a zero-subjective relative (ZR) algorithm was proposed for the airport intelligence degree evaluation. To ensure the accuracy of the evaluation results, the weights of functional indicators in the airport intelligence evaluation system were calculated by using expert opinions and objective judgment results. At last, a case study of an airport in Jiangsu Province was given to evaluate the intelligence degree by using the ZR algorithm. Research results show that in 2018, the intelligence degree of the airport scores 65.64, and in 2022, the intelligence degree of the airport scores 77.08, indicating that various intelligent devices in the airport are constantly updated, and the intelligence degree of the airport improves constantly. The secondary security operation monitoring indicator under the airport emergency security improves by 65.7% in 2022 compared to 2018, the physical security screening indicator improves by 17.1%, and the emergency and security indicator improves by 16.2%. This can be explained by the fact that the airport vigorously developes the artificial intelligent analysis system in recent years, introduces the face recognition system at the terminal entrance and exit, and improves the station operation security monitoring platform. To a certain extent, it enhances the intelligence degree of airport security. The score of landside traffic indicator is 2.34 in 2018 and 2.54 in 2022, indicating no significant change, and the development of intelligence degree is slow. Therefore, resource investment should be strengthened in future construction.More>

2024, 24(2): 232-242. doi: 10.19818/j.cnki.1671-1637.2024.02.016

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Optimization of arterial traffic signal coordinated control with tandem pre-signal

LI Yan, SHI Xuan, NAN Si-rui, ZHU Cai-hua

Abstract: To improve the overall traffic flow efficiency, a bi-level model was established for optimizing the timing plans of arterial traffic signal coordinated control system with tandem pre-signals, and its solving algorithm was proposed. The upper-level model of the bi-level model was an optimization model of the offset between main signals, and the traversal search algorithm was employed to solve it between intersections. The lower-level model was a multi-objective optimization model, which selected the throughput vehicles and the average delay time as the optimization objectives. The flower pollination algorithm(FPA) was established to solve the proposed multi-objective optimization model. The traffic parameters in the bi-level model were connected by using the shockwave model. The optimal solutions of the parameters were obtained through the iterations between the upper-level and lower-level models. Three consecutive intersections after setting up tandem pre-signals were chosen to test. The proposed method was applied to optimize the traffic signal coordination timing plan on arterial roads under both high and low traffic demands. The effectiveness of the selected scheme was tested by software SUMO. Research results indicate that the bi-level model can optimize the arterial traffic signal coordination timing plan with tandem pre-signals. Compared with the traditional arterial signal coordinated control plan, the timing plans obtained from the proposed methods can increase the throughput vehicles through the system by 16%-35% and 8%-17%, respectively. Under high and low traffic demands, and the delays reduce by 7%-17% and 2%-16%, respectively. Compared to the particle swarm optimization (PSO) algorithm and non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ), the FPA requires 13 and 24 fewer iterations to achieve the specified accuracy requirements, respectively. The simulation results indicate that the proposed model can further improve the operational efficiency of road under high demand conditions.More>

2024, 24(2): 243-253. doi: 10.19818/j.cnki.1671-1637.2024.02.017

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Stability of vehicle platoon control system with three types of delays

ZHU Xu, SUN Zhuo, ZHANG Ze-hua, YAN Mao-de

Abstract: The internal stability and string stability of the vehicle platoon control system incorporating input delay, vehicle to vehicle communication delay, and broadcast delay of the lead vehicle were studied. In terms of internal stability, a method combining the Kronecker sum and cluster treatment of characteristic root (CTCR) method was proposed, in which the necessary and sufficient conditions for the internal stability of the system were obtained. In terms of string stability, the sufficient conditions were proposed to ensure that the disturbances propagated backward along the vehicle platoon without divergence. It was revealed that the string stability was independent of the vehicle to vehicle communication delay. On this basis, the upper bound of the delays and design range of the vehicle controller gains were provided to guarantee string stability. Simulation results show that the vehicle platoon control system can maintain both the internal stability and string stability simultaneously when the proposed stability conditions are satisfied. The delay margins obtained by the proposed internal stability method are both complete and exact, with the error between theoretically derived results and simulation experiment results being less than 0.1 s. In addition, the simulation time is two orders of magnitude shorter than the Bézout resultant elimination and three orders of magnitude shorter than the Sylvester resultant elimination. This indicates that the proposed method significantly reduces the computational burden of the traditional CTCR method. The state errors between vehicles quickly converge to 0 within 15 s. When the velocities of all vehicles are constant, a desired safe distance of 50 m between the successive vehicles is maintained. When the leader vehicle accelerates at 0.4 m·s^-2 and decelerates at 0.6 m·s^-2, the velocities and accelerations of the following vehicles change accordingly, while the spacing errors between vehicles remain less than 0.5 m, and these errors propagate backward along the vehicle platoon without divergence.More>

2024, 24(2): 254-266. doi: 10.19818/j.cnki.1671-1637.2024.02.018

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Improved model-free adaptive control for EMUs velocity tracking system

ZHOU Liang, XIA Jin-feng, LI Zhong-qi

Abstract: To improve the tracking accuracy and stable operation of the train control system, an improved multiple-input multiple-output (MIMO) model-free adaptive control (MFAC) method was proposed. Based on the dynamic linearization technology, the input-output data of each power unit of the system were equivalently transformed into a full form dynamic linearization (FFDL) data model that better fitted the actual operation characteristics of high-speed electric multiple units (EMUs). By incorporating the output error rates into the objective criterion function and weighting the fusion of output errors and output error rates, a new model-free adaptive control scheme with output error rates (MFAC-OER) was derived. The control performance of the algorithm and the equivalent description degree of the system were further improved by delayed estimation of uncertainty factors, such as external disturbances and parameter errors in the FFDL data model. The proposed method was simulated and tested on a CRH380A high-speed EMUs semi-physical test platform equipped in the laboratory to track the actual speed-displacement curve from Jinan to Xuzhou and compare it with some traditional algorithms. Simulation results show that the speed errors of each power unit of EMUs obtained by the MFAC-OER method are within [-0.151, 0.136] km·h^-1, with the control force and acceleration smoothly varying in the ranges of [-48, 42] kN and [-0.785, 0.687] m·s^-2, respectively. The proposed method outperforms the proportional-integral-derivative (PID) and traditional MFAC methods in the control performance. The overall simulation results show that the MFAC-OER method can not only quickly reach the steady state of the system but also possesses good resistance to external disturbances, meeting the tracking accuracy and safety requirements of the EMUs.More>

2024, 24(2): 267-280. doi: 10.19818/j.cnki.1671-1637.2024.02.019

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2024 Vol. 24, No. 2

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