交通运输工程学报

Cover and Contents of Vol.25, No.1, 2025

Cover Contents

Review and prospect on management of transportation and vehicle engineering discipline under NSFC in 2024

WANG Zhi-zhong, YU Rong-jie, QIU Bin

Abstract: More> The discipline of transportation and vehicle engineering under the National Natural Science Foundation of China (NSFC) focuses on the pressing demands of the economic forefront and national security through a "demand-driven and problem-oriented" approach. The discipline layout covers fundamental, forward-looking, original, transformative, and ground-breaking research and promotes the growth of the system through organized scientific research efforts. The specific content of this article includes: the application, acceptance, and funding status of the funded projects and an overview of organized scientific research efforts in the transportation and vehicle engineering discipline for 2024, and an interpretation of the key project call for proposals for 2025. In 2025, the discipline will continue to prioritize funding for the specific domains to propel their development, including the reconfigurable design of large space transfer vehicles for on-orbit refuelling, autonomous driving evaluation and verification, configuration design of mobile carrier platform and multi-platform coordinated operation, chassis coordinated control for distributed electric vehicles, special vehicles with reconfigurable or variable structures, blended wing-body layout aircraft design, aircraft/engine matching for wide-area flight and adaptive control for combined-engine variable flow channel, multi-network integration of multi-mode three-dimensional transportation, and coordinated operation of transportation systems in flight areas of hub airports.

2025, 25(1): 1-7. doi: 10.19818/j.cnki.1671-1637.2025.01.001

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Review on large language models in transportation

XIAO Jian-li, QIU Xue, ZHANG Yang, SU Hai-sheng, LI Zhi-peng, ZHANG Chuan-ming

Abstract: More> The promotion of large language models(LLMs) in transportation was further discussed. Their great potentials were demonstrated in improving traffic management and control, enhancing traffic safety, and advancing autonomous driving. The basic concepts and development of LLMs, large vision models, and large multimodal models were systematically expounded. Some LLMs in transportation were summarized in terms of their structures and training methods. The major applications of LLMs in transportation were discussed, such as traffic management and control, traffic safety, and autonomous driving. Research results show that, when it comes to traffic management and control, issues such as traffic signal control and traffic state prediction can be significantly addressed by the application of LLMs. New possibilities are also brought for urban traffic management. Traffic congestion and environmental pollution are both reduced. As for traffic safety, compared with previous models, LLMs application significantly improve the ability to analyze and predict traffic accidents. Through deep learning of historical accident data, the models can identify those areas and time periods with a high incidence of accidents. Consequently, preventive measures can be taken to improve the traffic safety index. In the field of autonomous driving, the shift from traditional models to multimodal autonomous driving models can not only enhance the abilities of decision-making and environmental adaptation, but also provide users with a safer and more comfortable driving experience. The potential and value of LLMs in transportation are explored. Besides, practical suggestions are also offered to create a more intelligent and efficient transportation system, such as reducing the computational cost of LLMs in transportation and improving the real-time performance and reliability of models.

2025, 25(1): 8-28. doi: 10.19818/j.cnki.1671-1637.2025.01.002

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Review on frictional properties and residual life prediction of spherical plain bearing

LYU Yan-jun, ZHAO Xiao-wei, CHEN Rui-bo, YANG Xin-liang, ZHANG Yong-fang, YANG Ling-yu, FANG Jian-min

Abstract: More> The research progress of the frictional properties of the spherical plain bearing was sorted out from two aspects of the external factor and surface treatment. The research progress of the residual life prediction of the spherical plain bearing was reviewed in terms of model prediction and data-model fusion prediction. The effects of the load, environmental temperature, swing cycle, lubricating materials, surface coating, surface modification, surface texture, and surface processing on the frictional properties of the spherical plain bearing were analyzed. The influencing factors and prediction methods of the spherical plain bearing life were discussed. Research results show that external factors have a significant influence on the friction and wear of the spherical plain bearing. In most cases, multiple factors are usually coupled during operation. Therefore, it is necessary to elucidate the mechanisms of the external factors on the friction and wear of spherical plain bearing, then the structure, lubrication mode and wear-resistant material of the joint bearing can be designed. Surface treatment can reduce the wear of spherical plain bearing friction pairs, and to improve the friction and wear of spherical plain bearing friction pairs by surface treatment, it is necessary to clarify the influence rules of coating parameters, modification process, texture parameters, and processing technology on the frictional properties of spherical plain bearing, so as to develop a surface treatment method with characteristics such as low cost, high reliability, low energy consumption, and minimal environmental pollution and enhance the frictional properties of the spherical plain bearing. There are many internal and external factors that affect the residual life of the spherical plain bearing. To accurately predict the residual life of the spherical plain bearing, it is necessary to analyze the operating conditions and friction and wear of the spherical plain bearing under service conditions. As a result, a reliable life prediction model and evaluation method can be established to predict the residual life of the spherical plain bearing.

2025, 25(1): 29-47. doi: 10.19818/j.cnki.1671-1637.2025.01.003

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Research review of control architecture and driving authority decision-making of driver-automation cooperative driving

HUANG Wei, HUANG Qi-peng

Abstract: More> In view of the control architecture and driving authority decision-making, the research status and development trend of driver-automation cooperative driving were expounded. In terms of control architecture, the characteristics and application range of switching control architecture and shared control architecture were analyzed, and the concept of hybrid control architecture was proposed. In terms of driving authority decision-making, the ways of using different sources and natures of information in different driving authority decision-making methods were discussed. The methods involved in the direct and indirect shared control methods when implementing the allocation of driving authority were summarized. The research perspectives and methods of decision-making at the strategy level and the executive level were sorted out. Research results show that for the safety problems of high-level automated driving on the road, the development of hybrid control architecture for describing the system dynamics under human safety intervention scenarios is conducive to avoiding model mismatch, which provides the foundation for control performance optimization and stability design. By integrating holographic situational awareness and data intelligence to collect and integrate data from multiple information sources, the dynamic changes of many factors in the driver-automation cooperative driving system can be more comprehensively understood, and the optimal driving authority decision can be made. Compared with direct shared control, indirect shared control can avoid direct confrontation between driver and automation control flows. However, at the executive level of dynamic driving authority allocation, it is necessary to consider the conflict feedback between driver and automation and ensure a reasonable interactive experience, so as to reflect the advantages of indirect shared control. The decision-making method based on the agent at the strategy level is independent of the accuracy of the mathematical model and can adapt to the dynamic change of the environment. The decision-making method based on game theory at the executive level can enhance the controllability and explainability of the driving authority decision-making system by modeling the driver-automation interaction process. In the future, the driver-automation cooperative driving system should be designed to further optimize the interactive experience. Meanwhile, the development of equal and inclusive driver-automation relationships is necessary. The robustness of the control system and the interpretation and adaptability of driving authority decision-making should be improved as well.

2025, 25(1): 48-65. doi: 10.19818/j.cnki.1671-1637.2025.01.004

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Review on technologies of fuel cell air compressors for vehicles

OU Kai, HU Hao-wen, WU Yu-heng, GUO Xuan, YANG Xin-rong, ZHANG Qian, MA Ming-hui, WANG Ya-xiong

Abstract: More> The research progress of fuel cell air compressors for vehicles was reviewed from the aspects of performance requirements and technology status. The technologies of key components parameter optimization design, electromechanical coupling control, manufacturing and performance testing of centrifugal air compressors were summarized. The future development directions of fuel cell air compressor technologies were prospected. Research results show that fuel cell air compressors need to meet the requirements of large flow rate and fast response. At present, the flow and pressure characteristics of the two-stage centrifugal air compressor can meet the oxygen supply requirements of the 5-350 kW fuel cell system. The maximum speed of the compressor can reach 1.0×10⁵ r·min^-1, and the response time from zero speed to idle speed is seconds. The parameters of key components such as impeller, diffuser and foil gas dynamic pressure bearing can be designed by optimization algorithm to improve the aerodynamic performance of air compressor. In order to reduce the speed and torque fluctuation of drive motor, current loop decoupling control and sensorless control can be used in the electromechanical coupling control of centrifugal air compressor to improve the dynamic response ability of the compressor. In order to ensure the aerodynamic performance and system stability of centrifugal air compressor in high-speed operation, high-precision ternary impeller machining is mainly realized by milling with five-axis computer numerical control machine tool, and the coating of foil gas dynamic pressure bearing usually adopts solid lubrication and plasma injection technology. In order to comprehensively evaluate the performance of fuel cell air compressors, it also need to carry out characteristic test such as flow, pressure ratio and efficiency and durability indicator test such as start-stop and life. At present, the test standards and methods of air compressor aerodynamic performance are relatively complete, but the test and evaluation methods related to durability need to be further improved. In the future, with the growing demand for sustainable transportation solutions, fuel cell air compressor technologies for vehicles will be developed in lightweight and intelligent direction.

2025, 25(1): 66-93. doi: 10.19818/j.cnki.1671-1637.2025.01.005

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Application of BP neural network tracking differentiator in maglev train suspension control

ZHANG He-hong, ZHANG Wen-jin, CHEN Jian, LIN Ze-ru, CHEN Guang-hou, MAO Bin, LONG Zhi-qiang

Abstract: More> To improve the safety and stability of maglev train suspension operation, the train suspension control system was selected as the research object, the real-time adaptive adjustment of tracking differentiator (TD) parameters based on the BP neural network (BP-NN) was analyzed. To avoid nonlinear complex operations in the TD algorithm, a fastest control synthesis function with linear characteristics was constructed using the second-order fastest time system and the state backstepping method, and a discrete form of fastest TD (FST-TD) was proposed. Frequency domain and convergence analysis was rigorously conducted on the proposed algorithm. For the issue of delayed parameter adjustment when FST-TD encountered irregular input signals, the self-learning capability of BP-NN and the dynamic characteristics of the adaptive uncertain system were integrated to propose a FST-TD based on BP-NN (BP-FST-TD) algorithm. In this algorithm, BP-NN parameter adaptive adjustment was achieved through online updated weights by the backpropagation algorithm. FST-TD performed real-time tracking and filtering of complex, multi-condition input signals based on the adaptive parameters. To validate the algorithm's effectiveness and practicality, the real-time tracking and filtering performance of BP-FST-TD was examined using gap signals with random noise in the maglev train suspension control system. Research results show that FST-TD has decent filtering and differentiation capabilities. The convergence analysis reveals that it exhibits no oscillation or overshoot. Furthermore, this FST-TD structure, without complex nonlinear operation, is relatively straightforward in design. The FST-TD maintains ideal smoothness and phase integrity during the tracking of various input signals. Under working conditions 1 and 2, the BP-FST-TD reduces the mean absolute error (MAE) of the gap signals by 32.6% and 61.8% respectively compared to traditional TD algorithms. Besides, the integrals of time-weighted absolute error reduce by 51.8% and 70.2%, respectively. These findings substantiate the effective tracking and filtering performance of BP-FST-TD, and the algorithm effectively suppresses random noise from the gap sensors under various operational conditions of the maglev train. Thus, it can be concluded that the suspension control system based on BP-FST-TD effectively ensures the stable suspension operation of the train. The research results offer novel approaches and methods for TD control parameter optimization in other engineering domains.

2025, 25(1): 94-106. doi: 10.19818/j.cnki.1671-1637.2025.01.006

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Safety adaptability test and calculation of tail push-type operation of power car

ZHANG Zhi-chao, ZHANG Yi-zhe, CHU Gao-feng, CUN Dong-dong, ZU Hong-lin, LYU Kai-kai

Abstract: More> The safety adaptability of power concentrated EMUs under the tail push-type operation of power car was systematically explored with a combination of test and simulation calculation. A dynamics performance test was conducted for the tail push-type operation of power car to analyze its safety adaptability on conditions such as the straight line, and curve of 300 m radius. A 12-settings system dynamics model was constructed by multi-body dynamics and substructure methods, including a tail power car, two adjacent trailers, and a 3D dynamics model of tight-lock coupler. The dynamics model was fully revised and validated by the test data. The simulations for more dangerous cases were carried out to analyze the safety of such a power car tail push-type operation. The safety adaptability of this operation on different lines was discussed. Research results show that under the curve condition of 300 m radius, the simulation calculation is basically consistent with experimental results. The pushing force of coupler has a small impact on the safety of tail power car operation. Due to the longitudinal creep of the wheel rail, the safety index of tail power car operation decreases under larger pushing force, while the one of adjacent trailers is relatively significantly affected by the pushing force. During the lateral pushing of tail power roof through the No.12 and No.9 turnout, the safety indicators of power car and its adjacent trailer increase with the rise of the pushing force of coupler. When the power car plays the pushing force of 100% and passes through the No.9 turnout laterally, the wheel load reduction rate and the lateral force of the wheel axle will exceed the limit. Therefore, the coupler pushing force of the power car passing through the turnout laterally should be minimized as much as possible.

2025, 25(1): 107-120. doi: 10.19818/j.cnki.1671-1637.2025.01.007

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Bifurcation control and complex motion analysis of high-speed bogie based on active yaw damper

MAO Ran-cheng, ZENG Jing, SHI Huai-long, WEN Jing-han, WEI Lai

Abstract: More> In order to ensure the hunting stability of high-speed trains and improve critical speed, a study on control of the bifurcation characteristics of vehicle system based on active yaw dampers was carried out. A simplified dynamics model containing the lateral/yaw motion of a rigid bogie and the lateral motion of the car body was established, and a nonlinear wheel-rail relationship was given by combining the measured wheel tread data at the end-worn stage. Active yaw dampers were connected in parallel on the basis of traditional passive suspension, and the Hopf bifurcation and complex motion of the vehicle system after bifurcation were analyzed based on the yaw motion control of bogie. Research results show that the Hopf bifurcation point can be delayed, and the critical speed of vehicle system can be directly increased from 247 km·h^-1 in passive state to 328 km·h^-1 through linear stiffness and damping control. The lateral wheelset displacement after bifurcation is not affected by linear stiffness control, increasing the hunting frequency from 5 Hz to 7 Hz, while the limit cycle amplitude and hunting frequency after bifurcation are effectively reduced via linear damping control. The critical speed is not changed by nonlinear stiffness and damping control, and quadratic control gain will cause the vehicle system to produce an unstable limit cycle. The amplitude of the limit cycle after bifurcation can be reduced through cubic control gain, of which the cubic stiffness control can increase the hunting frequency, while the cubic damping control can inhibit hunting frequency. Meanwhile, after Hopf bifurcation of the vehicle under traditional passive suspension, the system will go through the limit cycle motion into period doubling bifurcation and then lead to the chaotic state, whereas the linear control can maintain the stable single-cycle motion of the limit cycle after the supercritical Hopf bifurcation occurs at the speed of 386 km·h^-1, and its maximum Lyapunov exponent is always less than 0, which can effectively avoid the generation of complex chaotic motion of vehicle system, but the effect of nonlinear control is limited.

2025, 25(1): 121-131. doi: 10.19818/j.cnki.1671-1637.2025.01.008

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Efficient and robust multi-structure GNSS receiver based on signal quality monitoring

JIA Qiong-qiong, GUO Qi-qi, LI Wei-peng, CHEN Hong-jin

Abstract: More> To ensure the navigation performance of global navigation satellite system (GNSS) in complex environment while maintaining receiver efficiency, a multi-structure GNSS receiver was designed based on signal quality monitoring. The advantages of traditional scalar tracking loop (STL), vector tracking loop (VTL), and direct position estimation (DPE) receivers were fully utilized. The receiver adapted its operating mode in real-time by monitoring satellite signal quality. In addition to the basic STL, VTL, and DPE modes, the multipath channel exclusion and the narrow correlation anti-multipath were further added to both STL and VTL modes, and the exclusion multipath technolygy mode was added to DPE mode. Research results show that for simulation signal, under good satellite signal conditions, the receiver operates in STL mode, the horizontal and vertical positioning errors are 2.20 and 4.65 m, respectively. In the presence of multipath, the receiver switches to STL anti-multipath mode, the horizontal and vertical positioning errors are 3.23 and 18.18 m, respectively, significantly less than those in previous STL mode, which errors are 28.07 and 112.24 m. Under satellite occlusion, the receiver switches to VTL mode, the horizontal and vertical positioning errors are 7.24 and 38.44 m, respectively, better than those in previous STL anti-multipath mode, which errors are 16.59 and 110.10 m. In weak signal environment, the receiver switches to DPE mode, the horizontal and vertical positioning errors are 3.24 and 17.30 m, respectively, further improved from those in the previous mode, which errors are 4.47 and 24.89 m. The simulation results confirm that the multi-structure receiver switches to the optimal operating mode according to real-time signal monitoring. Based on the measured data, the receiver operates in STL mode under good signal condition, with horizontal and vertical positioning errors of 7.74 and 13.19 m. When some satellite are occluded, the receiver switches to VTL mode, with horizontal and vertical positioning errors of 16.07 and 9.31 m. In weak signal environment, the receiver switches to DPE mode, with horizontal and vertical positioning errors of 6.72 and 48.99 m. These errors are better than those in previous VTL mode.

2025, 25(1): 132-144. doi: 10.19818/j.cnki.1671-1637.2025.01.009

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Collision risk assessment for complex navigable waters based on ship dynamic cluster

LIU Ke-zhong, YU Yue-rong, ZHUANG Su-jie, ZHOU Yang, YUAN Zhi-tao, YANG Xing, XIN Xu-ri

Abstract: More> To address the challenges of insufficient spatial-temporal granularity and limited real-time dynamics in perceiving collision risk within complex navigable waters, a collision risk assessment framework based on ship dynamic clusters was developed. After preprocessing of ship trajectory data, a ship traffic topology network model for complex navigable waters was constructed to depict the interplay of ship collision risk within the region. By taking into account the dynamic spatial-temporal characteristics of ships, the spectral clustering algorithm was introduced for traffic segmentation, defining ship dynamic clusters. Further optimization of the ship dynamic cluster partitioning strategy was performed through the Davies-Bouldin index. Based on the graph theory, measures for ship interference complexity were introduced to establish a ship dynamic cluster risk assessment method, discerning high-risk collision areas within the complex navigable waters. A study was conducted on a representative complex navigable waters, the core port area of Ningbo-Zhoushan Port, where one-month ship traffic flow data was collected to assess ship collision risk under multi-ship encounter scenarios. Research results show that the proposed adaptive method for ship dynamic cluster partitioning effectively divides ships within navigable waters into several clusters. This approach simplifies ship-to-ship collision risk relationship, while retaining the most critical collision risk across the entire spatial scope. The proposed ship collision risk assesment method preserves 84.98% of the global risk. Compared to traditional distance-based clustering algorithm and other classical clustering algorithms such as K-means, hierarchical clustering, and density-based spatial clustering of applications with noise (DBSCAN), the proposed method has a larger retained risk value and can reduce unnecessary risk relationships. It achieves optimal comprehensive performance in terms of accuracy, cluster compactness, and scale balance, effectively reducing false positive rates and discretizing the overall regional risk. By further utilizing the proposed risk assessment model, the risk states of 8 640 multi-ship encounter scenarios are computed through superimposition, identifying high-risk areas within the port area and align with actual survey results.

2025, 25(1): 145-159. doi: 10.19818/j.cnki.1671-1637.2025.01.010

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Performance simulation and optimization of ship waste heat TEG-ORC combined cycle based on R1234ze and its mixed working fluids

LIU Chang-xin, SHI Fei-xiong, WANG Feng, LI Yi-ran, QIAO Guang-chao, SUN De-ping, LI Hua-an

Abstract: More> To improve the energy efficiency of ships during navigation, the ship waste heat was taken as the research object, and the problem of working fluid selection in the ship waste heat recovery system based on the combined thermoelectric generation-organic Rankine cycle (TEG-ORC) was studied. The thermodynamic and economic models of the TEG-ORC combined cycle system were constructed. The performance parameters of the combined cycle system were studied by using R1234ze single working fluid and R245fa/R1234ze mixed working fluid respectively. The system output power, thermal efficiency, and power-production cost were taken as evaluation indicators, and the output performances of the system with different mixing ratios were compared. By taking the highest system output power and the lowest power-production cost as indicators for optimization analysis, the optimal configuration of the combined cycle system with the mixed working fluid was determined. Analysis results show that when R1234ze single working fluid is used, the maximum output power of the combined cycle system is 1 836 W, the minimum power-production cost is 0.493 yuan·(kW·h)^-1, and the maximum thermal efficiency is 17.09%. As the proportion of R245fa component in the mixed working fluid increases continuously, compared with the R1234ze single working fluid, the system output power increases by up to 12%. Compared with the R245fa single working fluid, the power-production cost of the system decreases by up to 54%, and the corresponding output power increases by 10%. The optimal mixing ratio of R245fa/R1234ze is determined to be 0.9. At this time, the maximum system output power is 2 076 W, and the minimum power-production cost is 0.231 yuan·(kW·h)^-1, the maximum thermal efficiency is 34.5%. Compared with using the R1234ze single working fluid, the system with the mixed working fluid has a 13% increase in the maximum output power, a 102% increase in the maximum thermal efficiency, and a 53% reduction in the minimum power-production cost. When the system uses the working fluid with the optimal mixing ratio, the best system output power is determined to be 2 076 W. At this time, the number of TEG modules is 33, and the working fluid flow rate is 0.06 kg·s^-1, the evaporation pressure is 1 000 kPa. It can be seen that using the mixed working fluid further improves the output performance of the combined cycle system and the matching of the cold and heat sources.

2025, 25(1): 160-171. doi: 10.19818/j.cnki.1671-1637.2025.01.011

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Ship trajectory compression method based on time ratio-speed-heading

LIU Chang, CAO Lu-fang, YANG Yu-lu, LIN Bin, ZHANG Shi-ze

Abstract: More> By considering that the ship trajectory contains information such as time, position, speed, and heading, a ship trajectory compression method considering the spatiotemporal motion characteristics was proposed. For the ground speed and ground heading in the automatic identification system (AIS) data of ships, the speed-based (SP) and the heading-based (HD) compression algorithms were proposed to extract the trajectory motion data. To retain the time information and spatial data, the time-ratio (TR) algorithm was introduced. By integrating these three types of algorithms, the time ratio-speed-heading (TSH) compression algorithm was proposed, and the parameters of the TSH algorithm were adaptively determined according to the compression rate and length loss rate. To verify the effectiveness of proposed method, the AIS data of Weihai, Laotieshan, and Yangtze River waters were used as research objects and compared with the Douglas-Peucker (DP) algorithm and the improved DP algorithm. Experimental results show that the characteristic points of the ship trajectory can be more finely extracted by the TSH algorithm, thereby retaining the spatiotemporal and motion behavior. Among them, the single trajectory compression results show that the Hausdorff distance between the trajectories compressed by the TSH algorithm and the original trajectory is 1.6 and 1.1 times lower than those of the DP algorithm and the improved DP algorithm, respectively, and the multi-attribute symmetric segmentation path distance (MSSPD) is 1.9 times lower than that of the improved DP algorithm, which better retains the original characteristics of the ship trajectory. The overall trajectory compression results show that for Weihai, Laotieshan, and Yangtze River waters, the TSH algorithm is 2.1, 2.2, and 1.7 times lower than the DP algorithm in the Hausdorff distance and 1.4, 1.5, and 1.1 times lower than the improved DP algorithm, respectively. In the MSSPD index, it is 1.3, 1.1, and 1.2 times lower than the improved DP algorithm, respectively, which further proves the effectiveness of the TSH compression algorithm in retaining the ship navigation behavior. It is verified that the proposed TSH algorithm shows better trajectory reconstruction ability at a higher compression rate.

2025, 25(1): 172-183. doi: 10.19818/j.cnki.1671-1637.2025.01.012

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Analysis of autonomous vehicle accident severity factors based on hybrid model

YAN Ying, WANG Yu-ying, ZHOU Xuan, YUAN Hua-zhi, WANG Wen-xuan

Abstract: More> To deeply investigate the impacts of interactions between various factors in autonomous vehicle accidents on the accident severity, a hybrid model of interpretable machine learning and tree-augmented naive (TAN) Bayes network was proposed considering the factor interactions. According to the summarized public dataset of autonomous vehicle accident reports in California from 2014 to 2023, 13 factors were determined to be the independent variables. The dependent variable (accident severity) was classified into three classes: no injury, minor, and moderate-to-major accidents. Four machine learning algorithms, namely, extreme gradient boosting, random forests, K-nearest neighbors, and support vector machines, were applied to establish a classification prediction model for autonomous vehicle accident severity. The classification prediction model with the optimal performance was selected as the base model. Then the base model was combined with the Shapley additive explanations (SHAP) algorithm to select the key factors and the TAN Bayes network was established to extract nine interaction factor pairs. Finally, the SHAP algorithm was employed to analyze the single factors as well as three groups of interaction factor pairs with significant interaction effects. Research results show that for no injury, minor and moderate-to-major accidents, the accident area of accident partner, vehicle driving mode, and subject vehicle pre-accident motion state have a significant impact on accident severity, respectively. After 2020, when the rear part of the autonomous vehicle is collided, the SHAP interaction values for no injury accidents are all positive, while those for moderate-to-major accidents are all negative. When the autonomous vehicle's accident area as the front and the object vehicle accident area as the rear, only 16.7% of the SHAP interaction values are positive in moderate-to-major accidents. If both the accident areas of the autonomous vehicle and object vehicle are the front, 89.1% of the SHAP interaction values are positive in minor accidents. Therefore, autonomous vehicles can timely change the running track to avoid vehicle frontal accidents and then reduce the severity of vehicle accidents.

2025, 25(1): 184-196. doi: 10.19818/j.cnki.1671-1637.2025.01.013

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Global vehicle trajectories and traffic parameters detecting method in expressway based on radar and vision sensor fusion

DAI Zhe, WU Yu-xuan, DONG Shi, WANG Jian-wei, YUAN Chang-wei, ZUO Chen

Abstract: More> To meet the demand of smart expressways for a wide-range detection of traffic parameters in complex traffic environments, a global vehicle trajectories and traffic parameters detecting method was proposed based on the data fusion of millimeter-wave radar and vision sensor. Raw data was collected by millimeter-wave radars and vision sensors deployed on different roadside poles. Through spatio-temporal synchronization, association, fusion, and multi-object tracking of multi-source detection target data, an algorithm was designed for detecting vehicle trajectories in the local scene. An algorithm for detecting global vehicle trajectories in continuous scenes was designed by reconstructing vehicle spatio-temporal information and merging vehicle trajectories in continuous traffic scenes. A method for detecting traffic parameters based on global vehicle trajectories was designed through position, speed, and other microscopic motion information extracted from global vehicle trajectories. Experimental data was collected and manually labeled in a pilot section of the smart expressways and was used to validate the proposed method. Research results show that in vehicle detection task and trajectory tracking task, the overall vehicle detection accuracy of each local scene and multiple continuous traffic scenes is greater than 90%, and the deviation between the tracking trajectory position and the actual position of the vehicle is less than 0.2 m. In the traffic parameters detection task, the weighted average of mean absolute error between the detected vehicle's speed and the actual speed in the observation area is 3.41 km·h^-1, and the weighted average of mean absolute percentage error is 5.00%. The detection accuracies of traffic parameters such as space mean speed, traffic volume and traffic density can reach lane level, and the detection results are consistent with the real traffic phenomena in the expressway exit ramp and diverging area.

2025, 25(1): 197-210. doi: 10.19818/j.cnki.1671-1637.2025.01.014

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Heat transfer numerical calculation of ventilated brake disc with internal fusion heat pipe

XIAHOU Guo-wei, WANG Rui-qi, QIAO Ni, LIU Hao, LONG Kui, GU Xiao-song, MU Kang

Abstract: More> In order to strengthen the heat dissipation of existing ventilated brake discs (VBDs), prevent thermal degradation, and improve the braking safety of vehicles, a new type of VBD incorporating an integral heat pipe in the body, i.e., heat pipe disc (HPD), was proposed. To examine the heat transfer performance of HPD and its improvement effect, detailed FLUENT-based numerical simulation calculations of heat transfer in both HPD and VBD were conducted under the same working conditions. The intrinsic relationships between the heat transfer performance of HPD and three influencing factors, namely liquid filling rate, heat flow density, and rotational speed, were investigated through numerical calculations, and the heat transfer performance of HPD was compared to that of VBD. Research results show that the optimal liquid filling rate of HPD is 35% at low heat flow densities (not exceeding 4 700 W·m^-2) and 40% at high heat flow densities (exceeding 4 700 W·m^-2). The thermal resistance of HPD decreases with increasing heat flow density and increases with increasing rotational speed. The heat transfer effect of HPD has been significantly improved compared to VBD. For example, at a liquid filling rate of 35%, rotational speed of 23.1 rad·s^-1, and heat flow density of 5 839 W·m^-2, the average and maximum temperatures of the surface of HPD reduce by 49 K and 53 K, respectively, compared to VBD. At the same time, the thermal resistance reduces by 28%. Although the deviation of the average temperature of the surface of HPD is slightly higher than that of VBD, the local over-temperature of HPD has been improved due to its superior heat dissipation ability. The pressurized blocks in the connecting space of HPD ensure its structural strength and pressure-bearing capacity. As a result, its predicted number of failure cycles is 269 times higher than that of VBD. So the proposed HPD can significantly reduce its operating temperatures by enhancing heat transfer, thus improving the lifespan and safety of VBD.

2025, 25(1): 211-220. doi: 10.19818/j.cnki.1671-1637.2025.01.015

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Crack extension and life prediction of fastening spring clip in heavy-haul railways

WANG Yu-xuan, WANG Zhi-feng, NIE Shao-feng, WANG Ya-qiong

Abstract: More> The coupled vehicle-track-foundation dynamic analysis model and the fastening system analysis model were established to study the fatigue life of the spring clip in the fastening systems of ballasted tracks in heavy-haul railways. The time curves of the rail bottom displacement at the fastenings under different axle loads were calculated. The curves were applied as displacement loads in the fastening system model under normal installation conditions to analyze the mechanical behavior of the spring clip under service conditions. Based on the strain-life curve, cumulative damage theory, and crack extension theory, the stress of the spring clip during crack extension and the influence of axle load on the fatigue life of the spring clip were analyzed. Research results show that the spring clip reaches the normal installation state under 25 kN bolt preload. The vertical displacement of the middle limb of the spring clip is 10.2 mm, the clamping force is 10.1 kN, and the maximum stress is located at the rear curved limb of the spring clip. The increase in axle load affects the fatigue crack initiation life by changing the stress ratio of the spring clip. With the increase in axle load, the influence of the material properties of the spring clip on the initiation life decreases in proportion. The fatigue crack initiation life decreases progressively as the axle load increases from 27 t to 40 t. When the axle load is 40 t, the fatigue crack initiation life is about 1.28 million times, approximately 63% and 95% less than that at axle loads of 35 t and 30 t, respectively. Meanwhile, the rate of decrease of the fatigue crack initiation life is slowing down. The direction of the crack is twisted as it expands inside the spring clip. The stress at the front of the crack decays radially in the surrounding direction, while the stress direction is tensile towards the sides. The extension rate of spring clip cracks is slow at the beginning of cracking and keeps accelerating with increasing depth. The fatigue crack extension life and cumulative total passing weight of the spring clip decrease with increasing axle load, while the crack extension life is less than the crack initiation life.

2025, 25(1): 221-233. doi: 10.19818/j.cnki.1671-1637.2025.01.016

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Analysis method of steel bridge surface relative humidity

WANG Zhuang, LIU Yong-jian, GONG Bo-xu, CHEN Sha, LIU Jiang, LIU Mao-yi, WANG Zhi-qiang

Abstract: More> To explore the temporal variation and distribution characteristics of surface relative humidity, the concept of the relative humidity boundary layer was introduced. The difference between surface relative humidity and environment relative humidity was clarified. Based on the physical relationship between air temperature and humidity, a method for calculating the surface relative humidity of steel bridges was proposed. The accuracy of the method was verified. The surface relative humidity of a steel arch bridge was calculated using this method. The difference between surface relative humidity and environmental relative humidity was quantified. The results show that the variation pattern of surface relative humidity in steel arch bridges is consistent with that of environment relative humidity. Both annual and daily variations exhibit distinct sinusoidal characteristics. The amplitude of surface relative humidity variation is larger. Surface relative humidity commonly exceeds environmental relative humidity. In high-humidity environments, this condition can persist for several days. The longitudinal distribution of surface relative humidity on the arch ribs is highly uneven. The maximum difference in surface relative humidity between the top plate at the arch crown and the arch foot is 16%. The maximum difference in surface relative humidity between the bottom plate at the arch crown and the arch foot is also 10%. The surface relative humidity in the middle of the tie beam is evenly distributed. Significant differences exist between the ends and the middle. The maximum difference exceeds 30%. During the testing period, the environmental wetting time is 1 191.5 hours. The surface wetting time is 2 016 hours, 1.71 times the environmental wetting time. The wetting time of the top plate of the arch rib is greater than that of the bottom plate. The maximum difference reaches 17.5%. The surface wetting time of the top plate of the tie beam is less than that of the bottom plate. The maximum difference reaches 25.5%. Both the difference coefficient in relative humidity and the difference coefficient in wetting time represent the differences between the surface environment of the steel bridge and the atmospheric environment. Two types of the distribution pattern of different coefficients are consistent. The difference coefficients near the arch crown are higher than that near the arch foot. The difference coefficients for the tie beams in the middle are higher than that at the ends. At the same cross-section, the difference coefficients for the top plates of the arch rib are higher than that for the bottom plates. The difference coefficients for the top plates of the tie beam are lower than that for the bottom plates.

2025, 25(1): 234-247. doi: 10.19818/j.cnki.1671-1637.2025.01.017

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Few-shot model for extracting inspection report information based on bridge inspection domain-task transfer

ZHU Yan-jie, WANG Yu-chen, XIONG Wen, CAI Chun-sheng

Abstract: More> To reduce the reliance on large-scale manually annotated samples for extracting key information of bridge inspection, a bridge inspection key information extraction model applicable to few-shot scenarios was proposed. The method comprised a bridge inspection-specific pre-trained language model, a bi-directional long short-term memory (BiLSTM) network, and a conditional random field (CRF). Through the utilization of bridge-related corpora and inspection task data for the domain pre-training and task fine-tuning, a two-stage transfer from domain knowledge to task-specific features was implemented, resulting in a pre-trained language model with high generalization for bridge-specific terminology and inspection report formats. Subsequently, the BiLSTM was employed to capture the contextual dependencies within the bridge inspection reports, while the CRF was combined to enforce structured constraints on the final extraction results. According to industry specifications and relevant research, eight key information categories commonly found in bridge inspection reports were redefined. To validate the effectiveness of the proposed approach, few-shot datasets containing only 50 and 100 sentences were utilized for training, respectively, with performance evaluated on a test set containing 1 491 sentences. Experimental results show that, when trained with 50 and 100 samples respectively, the F₁ scores of the proposed model reach 0.860 7 and 0.820 2, respectively, significantly outperforming four mainstream models. This confirms the model's superior capability in accurately extracting key information from bridge inspection reports under few-shot conditions. Moreover, ablation experiments further reveal that the two-stage transfer learning strategy effectively facilitates the rapid extraction of domain-relevant and task-discriminative features from few-shot data, thereby substantially enhancing the model's overall performance in few-shot scenarios. The proposed bridge inspection information extraction method under few-shot scenarios can be used to construct a knowledge graph for evaluating bridge structural conditions and predicting future service life.

2025, 25(1): 248-262. doi: 10.19818/j.cnki.1671-1637.2025.01.018

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Calculation mode for dynamic load allowance of negative bending moment of short and medium-span continuous girder bridge under design load

ZHOU Yong-jun, XUE Yu-xin, YANG Xiao-gang, FAN Kai-xiang, JIAO Chen-kai, ZHAO Yu, WANG Ye-lu

Abstract: More> To clarify the dynamic load allowance (DLA) of negative bending moment of short and medium-span continuous girder bridges under design load, theoretical derivation and numerical simulation were adopted to conduct the research on the DLA of negative bending moment of short and medium-span continuous girder bridges. Based on the Euler-Bernoulli girder theory, an analytical expression for the DLA of negative bending moment of a two-span continuous girder under multiple moving concentrated forces was derived. Continuous girder bridges with different standard spans were selected as research objects, and a spatial three-axis vehicle model was applied. Based on the principle of equivalent load effect in the negative bending moment section, the design load of lanes was equated to the heavy vehicle load spectrum in a quasi-design state. The vibration analysis model of coupled vehicle and bridge numerical simulation was established by ANSYS software. The significance analysis of the influence of bridge frequency, deck roughness, and vehicle speed on the DLA of negative bending moment was carried out. Plenty of numerical simulation results were counted. With the frequency of bridge structure as the independent variable and the deck roughness as the sub-standard, a calculation mode of DLA of negative bending moment and its suggested value were proposed, and they were compared with the standard values in China and abroad. Research results show that the maximum difference between the DLA of negative bending moment of short and medium-span continuous girder bridges with the same span but different span numbers is 38%. The DLA of negative bending moment gradually increases as the deck roughness class decreases. The average DLA of negative bending moment for deck roughness of Class B and Class C is 2.07 times and 4.15 times the corresponding average value for roughness of Class A, respectively. Vehicle speed has a great influence on the DLA of negative bending moment, but the relationship is not clear. When the deck roughness is Class B and Class C, the DLA of negative bending moment in the specifications of various countries are underestimated. The design value of the DLA of negative bending moment of the short and medium-span continuous girder bridge is suggested to be 0.335.

2025, 25(1): 263-273. doi: 10.19818/j.cnki.1671-1637.2025.01.019

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Global traffic state prediction method for non-sensing locations on freeways

WANG Yi-bing, HU Ran, YU Hong-xin, LI Jia-heng, ZHANG Yu-jie, XU Zhi-gang, HE Zhao-cheng, LU Qi-rong

Abstract: More> In view of the problem that existing research on traffic state prediction of freeways rarely considers non-sensing locations or road topology changes, the limitations of existing research methods were analyzed. A traffic state prediction method combining macroscopic traffic flow model, extended Kalman filtering, and data-driven long short-term memory (LSTM) was proposed, aiming to fully leverage the advantages of machine learning in temporal feature expression and trustworthy traffic flow models in spatial dynamic tracking. Based on the flow and speed data of limited sensing locations, a model of ecoulement of traffic autoroute for networks (METANET) was constructed, and the global model parameters and fundamental diagram parameters were calibrated. A traffic state estimator based on METANET and extended Kalman filtering was designed. The machine learning model was trained to predict the traffic state of all sensing points, and the traffic state estimator was driven to predict the global traffic state. Research results show that the proposed traffic state prediction method can significantly improve the prediction accuracy of flow and speed of freeways. The mean absolute percentage errors of 5-minute flow and speed predictions are 6.92% and 5.29%, which perform 29.62% and 24.28% better than baseline method, respectively, and those of 30-minute flow and speed predictions are 10.02% and 8.62%, which perform 24.84% and 15.87% better than baseline method, respectively. In addition, the proposed method fully considers the impact of on/off ramp flow on the mainline traffic state, so the performance of mainline traffic flow prediction is significantly improved.

2025, 25(1): 274-294. doi: 10.19818/j.cnki.1671-1637.2025.01.020

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Combination design method of tandem intersections with contraflow left-turn lane

SONG Lang, AN Shi, YU Shan-chuan, WANG Jian

Abstract: More> Due to fixed lane configurations, the conventional intersection (CI) performed well only in specific traffic scenarios after being transformed into contraflow left-turn lane (CLL) or tandem intersection (TI). To overcome this problem, a combination design method was proposed by integrating CLL and TI to expand the design concept. Lane-based traffic lights and reversible lane signs were used to flexibly divide the usage function of each lane during operation to form a mixed usage area (MUA), and each leg can be adjusted to CI, CLL, TI, or CLL combined with TI design. A mixed integer linear programming model was developed for collaborative optimization of design scheme selection, lane assignment, and signal timing. The operational performances were compared among intersection design schemes such as combination design, existing CI4(CI on four legs), CLL4 (CLL or CI on four legs with at least one CLL-formed leg), and TI4 (TI or CI on four legs with at least one TI-formed leg) through case and sensitivity analysis. Research results show that through the combination design method, the dynamic switching of a total of 4⁴=256 design schemes for the 4 legs at the intersection is achieved, and the number of lanes used in each traffic movement can be adjusted. Compared to CI4, CLL4, and TI4, the average delay was reduced by 42.96%, 39.43%, and 11.73% at peak hours, respectively, therefore the combination design demonstrates a bigger advantage in alleviating traffic congestion. The effectiveness of the combination design in enhancing the capacity of CI4 is positively related to the proportion of left-turn movements, and the enhancement ratio is presented as a shape of an initial increase followed by a decrease as the length of MUA increases. The length of the MUA for the combination design was recommended to be set between 50-70 m. In various traffic flow scenarios, the maximum increase in traffic capacity of the combination design compared to CI4, CLL4, and TI4 can reach 58.37%, 46.10%, and 11.94%, respectively, while the minimum value is not less than 0. This indicates that the combination design can consistently enhance intersection capacity with a more flexible lane assignment to better accommodate practical traffic operation needs.

2025, 25(1): 295-310. doi: 10.19818/j.cnki.1671-1637.2025.01.021

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