交通运输工程学报

Cover and Contents of Vol.23, No.6, 2023

Cover Contents

Construction and rethinking on public service platform for autonomous driving test

WANG Zhi-zhong, TIAN Ye, SUN Jian, HUANG Yan, YU Rong-jie

Abstract: To promote the development of autonomous driving technology in China, by conducting a comprehensive survey and adhering to the principles of instrumental design, the transportation and vehicle engineering discipline of the National Natural Science Foundation of China proposed a public service platform for autonomous driving tests (OnSite). The platform embodied the principles of socially co-constructed scenario library, agile development environment, system-under-test decoupling, lightweight test deployment, and transparent test result sharing. To ensure the independent development and smooth operation of the public service platform, the strategic committee, technical committee, user committee, and innovation foundation were set up through the self-decision-making. In 2021, research in this field was launched rapidly through the support of general programs by the transportation and vehicle engineering discipline. From 2022, research related to the autonomous driving technology testing was supported by the key and general programs. The construction of the OnSite platform was promoted, and the organized scientific research was actively carried out. A five-stage construction plan for the public service platform was devised, which follows the steps of single-item decision-making and planning testing, from single-item testing to full-stack testing, from virtual testing to virtual-real fusion testing, from single-vehicle testing to fleet testing, and from testing-orientation to development testing. The first phase of the construction goals was accomplished, and the testing capability for the single-item decision-making and planning functions was developed. Relying on the OnSite platform, the First OnSite Autonomous Driving Algorithm Competition was successfully held by the transportation and vehicle engineering discipline, which assisted researchers in pinpointing research gaps and promoted the realization of a demand-driven and problem-oriented research paradigm. It broke the barriers between the scientific research institutions and the industrial sectors and realized the accurate and rapid docking among industry, academia, and research. Furthermore, the OnSite competition was utilized the competition for testing, improved the evaluation system of the basic research programs, and contributed to addressing the issue of pursuing only four aspects.More>

2023, 23(6): 1-9. doi: 10.19818/j.cnki.1671-1637.2023.06.001

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Research progress in testing and evaluation technologies for autonomous driving

ZHAO Xiang-mo's team supported by the National Key Research and Development Program of China (2021YFB2501200)

Abstract: In view of the high cost, long cycle, low coverage, and lack of a perfect tool chain for autonomous driving vehicle tests in the actual complex traffic environment, the research status of seven major areas of testing and evaluation technologies for autonomous driving was analyzed, and the future development direction of testing and evaluation technologies for autonomous driving was predicted, including simulation and testing technology of autonomous driving vehicles, simulation and testing technology of traffic flow, hardware-in-the-loop testing technology, field testing technology, intelligence evaluation technology, testing and evaluation tool chain and its system's construction, certification and potential defect detection technology, etc. In terms of simulation and testing of autonomous driving vehicles, the research status of simulation and testing software for autonomous driving, vehicle dynamics models, background vehicle interaction behavior models for testing, simulation and testing of cloud control platform supervision, and standardization of vehicle simulation system was analyzed. The main problems currently existing in the simulation and testing of autonomous driving vehicles were summarized. In terms of simulation and testing of autonomous driving traffic flow, the research status of driving style models for test background vehicles, traffic flow modeling and simulation, traffic scenario generation methods, and acceleration testing methods was summarized, and the future development trend of simulation and testing of autonomous driving traffic flow was predicted. In terms of hardware-in-the-loop testing technology, the human-vehicle-road-loop multi-dimensional digital twin tests and construction methods of the system platform for autonomous driving vehicles were summarized. Typical sensor data from high-definition cameras, millimeter-wave radars, and ultrasonic radars, as well as simulation technology of vehicle-to-vehicle and vehicle-to-road communication signals, were reviewed. In terms of field testing technology, the development status of closed field testing, open road testing, and highway test-related testing fields, testing standards, and key technologies were summarized. In terms of intelligence evaluation technology, the research status of intelligence evaluation methods for autonomous driving was introduced from four aspects: the concept of autonomous driving intelligence, the quantification and evaluation of scene complexity, the intelligence evaluation systems of autonomous driving, and the social cooperation evaluation methods. In terms of testing and evaluation tool chain and system construction, the current situation of the testing and evaluation standard system for autonomous driving was introduced mainly from three aspects: the testing and evaluation tool chain technology, the autonomous driving testing evaluation system, and the current situation of autonomous driving testing standards. Finally, in terms of certification and potential defect detection technology, the current defect detection methods for autonomous driving were reviewed from the definition, cause, classification, and detection of autonomous driving defects. The challenges faced in the safety assurance of autonomous driving vehicles were summarized. Research results show that although the autonomous driving testing and evaluation technology has made great progress, the testing and evaluation standard system is still not perfect, and the existing testing tools and methods fail to meet the testing needs of autonomous driving vehicles at level three and above. The development and application level of virtual simulation and digital twin technology is low, and there are many deficiencies in the degree of simulation, testing efficiency, and vehicle testing ability. In the future, it is necessary to further strengthen the research and development of full-scene and high-fidelity modeling technology and real-time simulation software, establish an online accelerated twin testing system with virtual and real interaction, study the scenario generation and acceleration methods of autonomous driving full-stack hazardous testing, and integrate autonomous driving testing technologies and tools, so as to form a tool chain for autonomous driving testing and evaluation and improve standard specifications.More>

2023, 23(6): 10-77. doi: 10.19818/j.cnki.1671-1637.2023.06.002

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Review on research of low-altitude airspace capacity evaluation

ZHANG Hong-hai, YI Jia, LI Shan, LIU Hao, ZHONG Gang

Abstract: The basic definition of airspace capacity was combed. The origin and development of airspace capacity evaluation methodology research were reviewed. The main findings of four typical airspace capacity evaluation methods (evaluation method based on mathematical calculation models, radar simulator evaluation method based on controller workloads, evaluation method based on computer simulation modeling, and evaluation method based on data-driven) were summarized. Combined with the current situation and reform needs of China's airspace management, a framework for the low-altitude airspace capacity evaluation was proposed. The low-altitude airspace classification and air route planning, landing and take-off airport location layout and capacity evaluation, influencing factors analysis and evaluation methods of low-altitude airspace capacity were introduced, respectively. Future development trend was predicted. Research results show that the classification and planning of low-altitude airspace is the basic premise of capacity evaluation, and the complexity of the low-altitude airspace environment should be fully considered, combined with the performance of aircraft and scientific planning of application scenarios. Landing and take-off airports are key nodes in the low-altitude airspace environment. The site location and internal structure will directly affect the overall low-altitude airspace capacity level. The influencing factors analysis on the low-altitude airspace capacity is a key step and serves as a cross-validation with the results of low-altitude airspace capacity evaluation. At present, a mature methodological system for the low-altitude airspace capacity evaluation has not been developed. Three methods are mainly introduced, which are the threshold-based airspace capacity evaluation method, geometrical topology-based airspace capacity evaluation method, and control-variable-based airspace capacity evaluation method. In general, the low-altitude airspace capacity evaluation is an important content to realize the rational allocation of low-altitude airspace resources and ensure the safe and efficient low-altitude airspace operation, and it should be combined with the characteristics of China's airspace management to carry out locally adapted research on the low-altitude airspace capacity evaluation method and pilot validation.More>

2023, 23(6): 78-93. doi: 10.19818/j.cnki.1671-1637.2023.06.003

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Review on bridge fire science and safety guarantee technology

ZHANG Gang, ZHAO Xiao-cui, SONG Chao-jie, LI Xu-yang, TANG Chen-hao, WAN Hao, LU Ze-lei, DING Yu-hang

Abstract: The current research status of bridge fire safety theory and guarantee technology was summarized, and the frequency and probability of bridge fire accidents at home and abroad were introduced. Then, the safety operation situation of transportation vehicles such as hazardous chemical vehicles and the risk of bridge fires caused by hazardous chemical vehicles (oil tankers) were presented, and the development direction of new safety control technologies for bridge fires was pointed out. Analysis results indicate that bridge fires have the characteristics of multiple occurrences and diversity. Much attention from scholars and departments was paid to the safety control of bridge fires, and fire tests and fire protection work have been carried out on some bridge structures, but the fire resistance design specifications for bridges are still a research gap. The concrete spalling behavior has complete randomness, and the high-temperature concrete spalling is difficult in the fire resistance analysis of concrete structure bridges. The research on the shear behavior of prestressed concrete bridges in fire exposure conditions is difficult, and currently relevant studies focus on bending. There is relatively little research on the heat transfer and structure thermal response of steel girders with complex cross-sectional forms, which falls far short as per the requirements for the intelligent construction and long-term safe operation and maintenance in steel structure bridges. Relevant design details, intelligent protective measures, and systems should be urgently developed. Due to the complex structure form of cable-supported system bridges, the thermal expansion of components in fire exposure conditions is influenced by each component. Therefore, the overall behavior of the structure exhibits significant local enhancement effects, making it difficult to predict using the refined numerical models. However, current research only concentrates on the temperature field between components and connectors or the structure, and there is a lack of research on the overall response of the structure. The fire resistance performance and failure criteria of cable-supported system bridges in fire exposure conditions are research hotspots and difficult points. The bridge structure is in an open space, and the fire monitoring and early warning in the bridge structure have many interference factors and are relatively difficult. However, it is necessary to continuously study the major fire safety monitoring and early intelligent warning, intelligent protection, and performance enhancement of bridges. The intelligent protection methods for bridge structures under complex and extreme environmental fire exposure, and intelligent monitoring, early warning, and protection technologies for bridge structures under complex and sudden fire situations should urgently be systematically studied. The toughness of bridge fire resistance is a difficult point in the research on bridge fire science and safety guarantee. It involves the fire resistance during disasters and the post-disaster rehabilitation and requires in-depth research to provide a theoretical basis for the full-life construction and safe operation and maintenance of bridges.More>

2023, 23(6): 94-113. doi: 10.19818/j.cnki.1671-1637.2023.06.004

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Mechanical properties of salinized aeolian sand under freeze-thaw cycles

BAO Wei-xing, LI Wei, MAO Xue-song, CHEN Rui, QIN Chuan, LIU Ya-lun

Abstract: In order to study the mechanical properties of salinized aeolian sand at the edge of the desert in the monsoon freezing zone, triaxial unconsolidated and undrained shear tests were carried out on the aeolian sands with different salt contents under freeze-thaw cycle conditions. To study the stress-strain relationship curves and deterioration laws of shear strengths of aeolian sands with different salt contents after freeze-thaw cycles, a modified Duncan-Zhang model considering the conditions of perimeter pressure and the number of freeze-thaw cycles was proposed. The shear strength deterioration degree was introduced to describe the rate of strength decay of aeolian sand, and the formula for calculating the coupling effect of the number of freeze-thaw cycles and salt content on the shear strength of aeolian sand was proposed. Research results show that the stress-strain curves of aeolian sands with different numbers of freeze-thaw cycles, salt contents, and perimeter pressures are all the strain-softening type. The salinized aeolian sand under freeze-thaw cycles is subjected to the coupling of temperature and salinity, and the strain softening rate of aeolian sand decreases significantly with the increases in the number of freeze-thaw cycles and salt content. The modified Duncan-Zhang model can better characterize the strain softening of aeolian sand. The initial resilience moduli of aeolian sand under different numbers of freeze-thaw cycles increase with the increase in the perimeter pressure, and decrease first and then increase slowly with the number of freeze-thaw cycles. Under the freeze-thaw conditions, the deterioration rate of shear strength of unsalted aeolian sand is slow. In the case of the salinized aeolian sand, the phase changes in the salt and moisture in the soil accelerate the deterioration rate of aeolian sand shear strength, leading to a rapid decrease in the shear strength of aeolian sand. For the aeolian sand under different perimeter pressures, the patterns of strength change are similar, and the shear strengths decrease significantly after the initial freeze-thaw cycle. As the number of freeze-thaw cycles increases, the deterioration rates of strength are gradually stable. The shear strength deterioration degree of aeolian sand increases hyperbolically with the number of freeze-thaw cycles and linearly with salt content.More>

2023, 23(6): 114-124. doi: 10.19818/j.cnki.1671-1637.2023.06.005

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High-compactness paving characteristics of asphalt pavement under combined load

JIA Jie, ZHU Jian-guo, LIU Hong-hai, WAN Yi-pin

Abstract: To improve the initial compactness of the asphalt pavement and obtain the high-compactness characteristics of the paving mixture after the screed of paver operation, the effect of the combined load generated by the tamper and vibrator was considered. In view of the screed's dynamics characteristics and its compaction effect on the paving mixture, the dynamics model of the screed compaction system was established. Based on the displacement changes in the screed under different frequencies of tamper and vibrator, the relationship between the compactness of the paving mixture and the dynamic response of the screed was analyzed. The simulation design was carried out by the orthogonal test method. Taking the average displacement peak of the dynamic response of screed as the evaluation index of compactness, the compaction effect of the mixture under the combined load generated by the tamper and vibrator was analyzed. A test was carried out to observe the high-compactness paving effect of the screed on the mixture. The compactness of the pavement under the action of only the tamper and the variations in the paving compactness increment with the tamper frequency after the addition of the vibrator was verified, and the correlation between the compactness increment and the paving compactness under only the tamper load was analyzed. Research results show that when the difference between the vibrator frequency and the tamper frequency increases, the impact of the tamper load on the displacement peak of the screed is not significant. The vibration compaction can compensate for the compactness of the weak compaction position of the tamper, but there is a compaction limit. When the tamper frequency is 10-18 Hz, and the corresponding vibrator frequency is 30-40 Hz, the combined compaction of tamper and vibrator achieves the best state, which can improve the compactness of the mixture and avoid the overcompaction of the mixture by the screed during the high-compactness paving operation. When the vibrator frequency is within or exceeds the high-compactness frequency range, the compactness increment of the mixture varies by 2%-6%.More>

2023, 23(6): 125-134. doi: 10.19818/j.cnki.1671-1637.2023.06.006

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Interval prediction of track irregularity based on GM(1, 1) model and relevance vector machine

WANG Ying-jie, CHU Hang, CHEN Yun-feng, SHI Jin

Abstract: The GM(1, 1) grey model and relevance vector machine (RVM) algorithm were integrated to propose a GM(1, 1)-RVM combination model for the interval prediction of track irregularities to carry out the preventive maintenance work. Considering the oscillation characteristics of the track quality index (TQI), the GM(1, 1) model was improved by smooth optimization of the quadratic-logarithmic composite function and sequence weight optimization. The parameters to be optimized were searched and determined by the particle swarm optimization (PSO) algorithm, and then the predicted point values were calculated. The mapping mode of sample features with the predicted point value as input and the true TQI as output was constructed, and the 5-fold cross-validation was introduced to optimize and train the combined kernel function of the RVM model. The combination prediction model was integrated by the input-output alignment mechanism between the GM(1, 1) model and the RVM model, and the prediction effect of the track irregularity interval was tested by taking two sections of a ballasted railway line as examples. Research results show that compared with the existing prediction models, the mean and variance of the predicted interval can be calculated by the improved GM(1, 1)-RVM combination model to expand the prediction results from single point values to prediction intervals. Compared with the true TQIs, the mean percentage errors of the predicted point results obtained by the improved GM(1, 1)-RVM combination model on the extrapolation range at the two sections are 1.53% and 4.67%, respectively, and they are 0.58% and 0.61% lower than the support vector regression (SVR) model, respectively, and 0.15% and 1.87% lower than the GM(1, 1)-back propagation neural network (BPNN) model, respectively. Under the confidence levels of 90%, 95%, and 99%, the maximum mean prediction interval widths obtained by the improved GM(1, 1)-RVM combination model are 0.324 5, 0.387 9, and 0.510 5 mm, respectively, and the minimum prediction interval coverage rates are 91.67%, 95.83%, and 95.83%, respectively. The prediction interval can cover most of the TQI evolution data on the extrapolation interval. Thus, the random fluctuation in the track irregularity evolution can be controlled by employing the predicted mean and variance to construct the interval boundary, which provides a new idea for the track irregularity prediction. 3 tabs, 5 figs, 30 refs.More>

2023, 23(6): 135-145. doi: 10.19818/j.cnki.1671-1637.2023.06.007

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Research on dynamic amplification factor of highway simply supported girder bridge based on modal superposition method

ZHOU Yong-jun, XUE Yu-xin, GAO Xu-jun, LI Ran-ran, WANG Ye-lu, ZHAO Yu

Abstract: To explore the effect of modal orders on analyzing dynamic amplification factors (DAFs) of deflection and bending moment, simply supported T-girder bridges, box girder bridges, and hollow slab bridges with standard spans were selected as the research objects, and based on the modal superposition method, the DAF formula of simply supported girders under the action of three-axle vehicle was derived. The vehicle-bridge coupling vibration analysis program was compiled by using MATLAB software for numerical calculation, and the relationship of the DAFs of the deflection and bending moment with the order of modal truncation was studied under the influence of three factors, such as deck roughness, vehicle speed, and vehicle mass. In addition, the ratio relationship between two DAFs under different modal orders was analyzed and verified by the dynamic field test of a 30 m simply-supported box girder bridge. Research results show that the DAF of deflection is less affected by the modal order, and the contribution rate of the first-order mode to the DAF of deflection is 99%. When the modes at the first five orders are selected, the complete structural response information of the bridge can be obtained. However, the DAF of bending moment is greatly affected by the modal order, and the contribution rate of the first-order mode to the DAF of bending moment is 86%, while the contribution rate of the modes at the first five orders is 90%. Reliable results of DAF of bending moment are obtained when the modes at the first 25 orders or more are considered. The contribution rate of modal orders to the DAFs is affected by vehicle speed to some extent. The influences of deck roughness and vehicle mass on the convergence of the DAFs are not significant. The DAF of bending moment is less than that of deflection. When the first-order mode is selected, the ratio of the two is 0.86. When the modes at the first 15 orders are selected, the ratio of the two is 0.95. It is suggested to use the DAF of deflection under the same test condition. 2 tabs, 10 figs, 29 refs.More>

2023, 23(6): 146-155. doi: 10.19818/j.cnki.1671-1637.2023.06.008

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Corrosion damage of bridge pile foundations under dry-wet cycles in strong salt marsh areas

FENG Zhong-ju, CHEN Hui-yun, WANG Fu-chun, HU Hai-bo, XU Zhan-hui, YAO Xian-hua

Abstract: To investigate the damage mechanism of concrete material of bridge pile foundations under the action of dry-wet cycles and strong salt marsh corrosion, indoor simulation tests were conducted, and the mass loss rates, relative dynamic elastic moduli, and corrosion resistance coefficients of the concretes with different material mass ratios immersed in composite salt solutions with different concentrations after dry-wet cycles were studied. The corrosion resistance micro-mechanisms of the concrete in pile bodies were investigated by using a combination of scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and chemical composition analysis. Research results indicate that the increase in concrete mass after dry-wet cycles is due to the formation of expansive crystals such as calcium aluminate and Friedel's salt in the material. The presence of chloride ions can inhibit the corrosive effect of sulfate ions on pile foundation concrete. When the composite salt solution concentration is different, after 120 dry-wet cycles, for the pile foundation concrete specimens with a mass ratio of cement, aggregate, sand, water, fly ash, water reducer, silica fume, and expansion agent as 327∶1 103∶767∶170∶87∶7∶22:44 (mass ratio Ⅲ), the relative dynamic elastic modulus is 92.7%, and the minimum corrosion resistance coefficient is 0.91. In comparison, the pile foundation concrete specimens without silica fume and expansion agent or only with silica fume have a maximum relative dynamic elastic modulus of 89.7% and a minimum corrosion resistance coefficient of 0.80. The pile foundation concrete specimens with mass ratio Ⅲ exhibit better corrosion resistance performance and have no internal cracks even when they are subjected to the expansion force, indicating that the addition of silica fume and expansion agent improves the corrosion resistance of pile foundation concrete while ensuring no crack appears in the pile foundation concrete. Obviously, the factors such as the category of corrosive ions must be comprehensively considered, and further optimization of mass ratio of pile foundation concrete material must be carried out based on the mass ratio Ⅲ in practical engineering. 6 tabs, 12 figs, 30 refs.More>

2023, 23(6): 156-167. doi: 10.19818/j.cnki.1671-1637.2023.06.009

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Optimization on multi-stage suspension scheme and dynamics performance of superconducting EDS maglev train

MA Wei-hua, LI Teng-fei, HU Jun-xiong, ZHANG Sai, LUO Shi-hui

Abstract: The suspension scheme of the superconducting electrodynamic suspension (EDS) maglev train levitation bogie was studied. The working principles of the superconducting EDS maglev train and the technical characteristics of the suspension system of existing levitation bogie were analyzed, and a multi-stage suspension system optimization scheme was proposed. The dynamics differential equation of the multi-stage suspension vehicle was theoretically derived. A co-simulation framework of superconducting EDS maglev train dynamics was established based on the multi-body dynamics software SIMPACK and the mathematical tool MATLAB/Simulink, and the magnetic properties of the superconducting EDS system were analyzed. The calculated electromagnetic forces were formed into a search table, and the mechanical models of three train bodies and four levitation bogies of the three-group superconducting EDS maglev train were constructed under the existing suspension scheme and multi-stage suspension scheme by SIMPACK. The electromagnetic force search model was established though MATLAB/Simulink. The search table was coupled with the mechanical dynamics model through the SIMAT module, and the dynamics responses of the superconducting EDS maglev trains under different suspension schemes in the condition of random track irregularity were compared though the co-simulation. Research results show that compared with the existing scheme, the vibration responses of the train levitation bogie and train body significantly reduce when the multi-stage suspension scheme is adopted, and the peak vibration acceleration amplitudes of both reduce by more than 50%. The vibration accelerations of the train bodies are both less than 1 m·s^-2, and the stability indexes are basically maintained at an excellent level below 2.5. It is proved that the multi-stage suspension scheme can improve the dynamic response of the train and enhance the overall ride comfort of the vehicle. The research can provide a theoretical basis and reference for the optimization design of the levitation bogie scheme and dynamics research of the superconducting EDS maglev train. 1 tab, 11 figs, 31 refs.More>

2023, 23(6): 168-179. doi: 10.19818/j.cnki.1671-1637.2023.06.010

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Single-objective performance optimization of PM EDS system

HU Yong-pan, WANG Zhi-qiang, LONG Zhi-qiang

Abstract: In view of the optimization of the lift-to-weight ratio, lift-to-drag ratio, and suspension stiffness of the ultra-high speed permanent magnet(PM) electrodynamic suspension (EDS) system, the solution domain was divided, and boundary conditions were established. In addition, the expression of the electromagnetic force was clarified. The control variable method was adopted, five groups of independent characteristic parameters were selected, the influences of characteristic parameters on each optimization indicator were analyzed, and the optimizable variables of different optimization indicators were pointed out. The values of wavelength, thickness, and width of the permanent magnet array and the width and thickness of the induction plate were studied when the lift-to-weight ratio was the maximum under different suspension gaps. The values of wavelength of the permanent magnet array and the thickness of the induction plate were studied when the lift-to-drag ratio was the maximum under different suspension gaps. The wavelength, thickness, and width of the permanent magnet array and the thickness of the induction plate were studied when the suspension stiffness was the maximum under different suspension gaps. An experimental study of the PM EDS system was carried out, and the variation rules of electromagnetic force with the linear velocity of the permanent magnet array were obtained. Research results show that at an ultra-high speed, the lift-to-weight ratio increases significantly with the increase in the remanence of the permanent magnet array, increases monotonically with the increase in the number of permanent magnets per unit wavelength, and generally increases initially and then decreases as the wavelength and width of the permanent magnet array increase. The lift-to-weight ratio is significantly affected by the thickness of the permanent magnet array. The lift-to-drag ratio is less affected by the remanence of the permanent magnet array, the widths of the permanent magnet array and the induction plate, and the suspension gap. In addition, the lift-to-drag ratio is significantly affected by the thickness of the induction plate. Greater wavelength, thickness, and speed of the permanent magnet array are more beneficial to improve the lift-to-drag ratio. The suspension stiffness increases monotonically with the increase in the remanence, width, and thickness of the permanent magnet array, initially increases and then decreases with the increase in the wavelength of the permanent magnet array, and initially increases rapidly and then slowly decreases with the increase in the thickness of the conductor plate. The suspension stiffness changes significantly with the increase in the suspension gap and changes little with speed. By taking the lift-to-weight ratio as the optimization indicator, when the suspension gap increases from 0.012 m to 0.020 m, the optimal thickness and wavelength of the permanent magnet array and the width of the induction plate gradually increase, while the optimal width of the permanent magnet array gradually decreases. The optimal lift-to-weight ratio drops by about 50.00%. By taking the lift-to-drag ratio as the optimization indicator, when the wavelength of the permanent magnet array increases from 0.050 m to 0.500 m, the optimal thickness of the induction plate gradually increases, and the optimal lift-to-drag ratio triples approximately. By taking the suspension stiffness as the optimization indicator, when the suspension gap increases from 0.012 m to 0.020 m, the optimal wavelength of the permanent magnet array gradually increases, and the optimal width of the permanent magnet array is equal to the width of the induction plate. Furthermore, the optimal thickness of the induction plate is around 0.001 m, and the optimal suspension stiffness decreases by approximately 50.00%. Through experiments, the changing trend of electromagnetic forces at linear speeds of 0-50.00 m·s^-1 is consistent with the theoretical calculation and simulation results. The lift force first increases rapidly with the increase in speed and then gradually becomes stable. The detent force increases sharply with the increase in speed, reaches the maximum value when the linear speed is about 4.00 m·s^-1, and then decreases slowly. 3 tabs, 19 figs, 30 refs.More>

2023, 23(6): 180-192. doi: 10.19818/j.cnki.1671-1637.2023.06.011

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Design of electromagnetic vibration test bench for maglev superconducting magnets

HU Dao-yu, YAN Shao-qiang, CAI Hua, ZHANG Zhi-hua, ZHANG Yan-qing

Abstract: The research progresses of test benches of the wheel-rail train, electromagnetic suspension train, superconducting pinned suspension train, and superconducting electrodynamic suspension train were reviewed. The spatial magnetic field distribution on the superconducting coil side generated by the propulsion coils and levitation coils of the superconducting electrodynamic suspension train was analyzed. The overall solution of the electromagnetic vibration test bench for superconducting magnets was proposed, and the excitation module serving as the subsystem, and the converter system were introduced, which were core components of the electromagnetic vibration test bench. In addition, a multi-frequency composite current closed-loop control strategy for the converter system was proposed. The background spatial magnetic field, electromagnetic load, and vibration acceleration response of superconducting magnets under online operation and offline electromagnetic vibration simulation were simulated and compared. Research results indicate that the main spatial harmonic magnetic field orders of the propulsion coils and levitation coils are the second and the fifth, respectively. Correspondingly, they cause electromagnetic force fluctuations in the third and sixth harmonic frequencies of the superconducting coils. The current control strategy can achieve the control of the 24-phase excitation modules direct current, as well as third and sixth harmonic frequencies currents. The main electromagnetic loads obtained by the electromagnetic vibration test bench are consistent with the actual operating conditions. Specifically, the steady-state propulsion force error is no more than 3.4%, the steady-state levitation force error is no more than 8.0%, and the torque errors of the main third and sixth harmonic frequencies are no more than 6.5% and 8.5%, respectively. The trends and amplitudes of online operation values and offline simulation values of acceleration responses of each observation point of the superconducting magnets are basically consistent. It can be seen that the test bench can well reproduce the background magnetic field, electromagnetic load, and acceleration response of the on-board superconducting magnets in the actual operating environment, and the effectiveness of the overall solution has been verified.More>

2023, 23(6): 193-205. doi: 10.19818/j.cnki.1671-1637.2023.06.012

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Strength evaluation of levitation frame for medium and low speed maglev train based on full-scale bench test

LI Miao, MA Ya-qun, WANG Yu, LUO Shi-hui, MA Wei-hua, LEI Cheng

Abstract: In order to evaluate whether the levitation frame of a medium and low speed maglev train meets the requirements of strength, the static strength and fatigue strength tests of the levitation frame were conducted by using the self-developed full-scale medium and low speed maglev strength test bench. According to the finite element analysis and the results obtained from multi-body dynamics simulation, the stress concentration position and bearing characteristics shown by the levitation frame were determined, followed by the reasonable arrangement of measuring points in a series on the levitation frame. The signals of strain response shown by the levitation frame of the train under three types of working conditions were measured, including extraordinary load, simulated main operation load, and simulated special operation load. Based on the material properties displayed by different parts of the levitation frame, the stress level of the levitation frame was evaluated through transformation calculation. Research results show that in the static strength test, large stress points of the levitation frame are mainly distribute at the corner of the bracket, the connection point between the mounting seat of support wheels and the anti-rolling beam, and the mounting seat of the parking brake sled, while the weak point obtained from the fatigue strength test is mainly at the weld joint between the longitudinal beam and the bracket. In comparison with the conventional operating conditions of the train, the stress amplitude values of the static strength and fatigue strength of the levitation frame increase by 1.06 and 4.77 times respectively under special operation conditions such as levitation failure and overloading braking. The maximum tensile stress and compressive stress of the levitation frame under all test conditions are 67.22 and -20.30 MPa, respectively, with the minimum safety factor as 1.71, indicating that the levitation frame meets the structural strength requirements. All the test data are within the envelope of the Goodman-Smith fatigue limit diagram of the corresponding material, indicating that the levitation frame meets the fatigue strength requirements. Through penetration inspection, it is identified that no cracks are found at any position of the levitation frame, which verifies the reliability of fatigue strength evaluation results of the levitation frame.More>

2023, 23(6): 206-215. doi: 10.19818/j.cnki.1671-1637.2023.06.013

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Online anomaly detection method integrating LSTM and MGD for suspension system of maglev trains

YANG Biao, MEI Zi, LONG Zhi-qiang

Abstract: In view of online anomaly detection of suspension system of maglev trains, a detection method based on long short-time memory (LSTM) neural network and multivariate Gaussian distribution (MGD) was proposed. The LSTM time series prediction model for learning the normal operation of the suspension system was established, and the prediction errors under normal conditions were obtained. Based on the prediction errors of the gap, current, and acceleration, the MGD model reflecting the distribution characteristics of the prediction errors under normal conditions was built. The log probability density was used as the detection indicator, the online detection logic was designed, and the threshold was set using F₁ score as the evaluation criterion of the detection effect. To verify the effectiveness of the proposed method, the operation line data of the maglev train were used to simulate online data, and the proposed method was applied to detect and analyze track crossing joint, rail smashing, and acceleration signal anomalies. Research results show that the F₁ scores of the proposed method for detecting the above three anomalies are 100.00%, 97.85%, and 83.33%, respectively. The detection indicators of the proposed method are significantly different between normal and abnormal conditions, reflecting the specific time period from anomaly occurrence of the suspension system to normal adjustment, and the algorithm takes about 2 s on average. Compared with the method based on the Gaussian distribution of hyperspheres, the proposed method achieves an average improvement of 1.9% in detection rate. Specifically, it achieves a 9.4% increase in detecting short-duration track crossing joint anomaly. Therefore, the proposed method can achieve online anomaly detection of the suspension system's state data.More>

2023, 23(6): 216-231. doi: 10.19818/j.cnki.1671-1637.2023.06.014

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Analysis of electromagnet structure parameters of medium and low speed maglev train based on test data

LIU Qing-hui, MA Wei-hua, SHAN Lei, LUO Shi-hui, LIU Jing, QIN Long-quan

Abstract: To improve the carrying capacity of medium and low speed maglev trains, based on the equivalent magnetic circuit method, a full-size levitation electromagnet magnetic circuit model was established. In addition, the vertical electromagnetic force expression containing the levitation electromagnet structure parameters was deduced. According to the influence factor analysis method, the influences of structure parameters such as the number of coil turns, electromagnet width, and pole plate length on the vertical electromagnetic force of the levitation electromagnet were comparatively investigated. Through the single electromagnet test bench, the changes in the vertical electromagnetic forces and lift-to-weight ratios of levitation electromagnets with 410 and 320 coil turns were compared under different levitation gaps and coil currents. The feasibility of optimizing the coil turns to improve the levitation performance of medium and low speed maglev trains was verified. Research results show that compared with the electromagnet width and pole plate length, the coil turns is the main factor affecting the levitation performance of maglev trains, but in the small current range of 10-30 A and the large levitation gap (>10 mm), changing the coil turns has a weak effect on the enhancement of vertical electromagnetic force of the levitation electromagnet. When the levitation gap is 8 mm, and the current of the coil is 30-50 A, the levitation electromagnet with 410 coil turns is more effective than that with 320 coil turns in improving the vertical electromagnetic force of the levitation electromagnet, and the average vertical electromagnetic force increases by about 2.94 kN, with an enhancement ratio of about 27.8%. The average lift-to-weight ratio increases by about 2.83, and the enhancement ratio is about 15.33%. As the coil current further increases, and the levitation gap further reduces, the average vertical electromagnetic force increases by about 3.38 kN, and the enhancement ratio is about 25.5%. The average lift-to-weight ratio improves by about 3.06, and the enhancement ratio is about 13.22%. It shows that the levitation electromagnet with 410 coil turns has the best effect on improving the levitation performance of medium and low speed maglev trains when the levitation gap is 8 mm, and the coil current is 30-50 A. The variance and standard deviation of vertical electromagnetic force of the levitation electromagnet with 410 coil turns are greater than those with 320 coil turns, indicating that increasing the coil turns will make the vertical electromagnetic force of the levitation electromagnet more sensitive to parameter changes.More>

2023, 23(6): 232-243. doi: 10.19818/j.cnki.1671-1637.2023.06.015

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Runway capacity evaluation based on multi-agent modeling and Monte Carlo simulation

CHEN Zheng-lei, CHONG Xiao-lei, LIU Chao-jia, SHAO bin, GENG Hao, ZHANG Jia-jia, XU Ji-hui

Abstract: The dynamic characteristics of aircraft formation and the characteristics of airport organization mode, control mode, and flight mode were analyzed, and the runway capacity calculation model and runway operation model were established. With semi-hybrid and hybrid operation modes for intermediate-distance parallel dual runway as typical scenarios, the runway capacities under different operation modes were calculated by comprehensively using multi-agent modeling and Monte Carlo simulation. An orthogonal simulation test was designed to investigate the relationship between runway capacity and various factors including operation mode, takeoff and landing ratio, departure interval, aircraft type ratio, formation number, and environmental conditions. Simulation results indicate that compared with the semi-hybrid operation mode, the hybrid operation mode increases takeoff capacity by an average of 55.2%, decreases landing capacity by 6.2%, and enhances overall capacity by 28.5%. As the departure interval increases from 60 s to 180 s, the total capacity of the semi-hybrid operation mode decreases by 27.2%, and the hybrid operation mode decreases by 24.9%. As the aircraft type ratio increases from 0 to 1.0, the total capacity of the semi-hybrid operation mode decreases by 29.7%, and the hybrid operation mode decreases by 29.2%. As the average formation number rises from 1.9 to 3.2, the total capacity of the semi-hybrid operation mode increases by 9.8%, and the hybrid operation mode increases by 7.1%. Therefore, the performance of the hybrid operation mode is better than the semi-hybrid operation mode, the runway capacity is closely related to the task dispatch mode, and the runway operation mode needs to be reasonably selected according to the task dispatch mode.More>

2023, 23(6): 244-256. doi: 10.19818/j.cnki.1671-1637.2023.06.016

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Reliable path planning model and algorithm in transportation networks with heterogeneous stochastic travel time in road links

HUANG Sen, XU Xiang-dong

Abstract: In view of the concerns of travel time reliability and unreliability from travelers in path selection decisions under the heterogeneous distribution of stochastic travel time in road links in a transportation network, a new reliable path planning model was proposed with the mean-excess travel time (METT) as the optimization criterion. To characterize the heterogeneous distributions of stochastic travel times in different road links in the transportation network, the first four order moments of travel time were used as inputs to analytically estimate the METT, thus avoiding the assumption of homogenous distributions in existing studies. The exact and approximate two-stage algorithms based on the Dijkstra and K-shortest path algorithms were developed according to the theoretical properties of METT. The accuracy of the analytical estimation method of METT based on the first four order moments was verified by using the Monte Carlo simulation method as the benchmark. The accuracy and computational efficiency of the approximate two-stage algorithm were analyzed by finding the shortest mean-excess paths of all OD pairs in the test network. Research results indicate that the commonly used normal distribution assumption of stochastic travel time in road links in existing studies ignores the influences of skewness and kurtosis coefficient on the reliable path selection. The relative error between the approximated value from the analytical estimation method and the true value of the METT is not greater than 0.13%. When K is set as 10 in the K-shortest path algorithm, in the shortest mean-excess paths of OD pairs in the whole network solved by the approximate two-stage algorithm, the minimum mean-excess values of 0.11% OD pairs are different from those solved by the exact two-stage algorithm, with a maximum relative error of 3.35%. For the OD pairs composed of randomly selected five nodes and other nodes, the ratio range of average calculation time of the approximate two-stage algorithm to that of the exact two-stage algorithm is 0.87%-22.96%, indicating that the approximate two-stage algorithm can not only ensure the solution accuracy, but also can improve the calculation efficiency. The proposed model and algorithms can capture the realistic characteristics regarding the heterogeneous distributions of stochastic travel times in different road links, and the corresponding path planning results can better reflect travelers' concerns about the reliability of arriving on time and the risk of encountering delay.More>

2023, 23(6): 257-269. doi: 10.19818/j.cnki.1671-1637.2023.06.017

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Cooperative merging control of connected and automated vehicles in merging area for one-way three-lane freeway

WANG Zheng-wu, PAN Jun-liang, CHEN Tao, HUA Xiao-yue

Abstract: In order to improve the merging safety and traffic efficiency of connected and automated vehicles (CAVs) at multilane freeway on-ramps, a rule-based lane-changing strategy and a discrete-time vehicle trajectory optimization model were proposed to implement cooperative merging control. With the merging area for common one-way three-lane freeway ramps as the research object, the merging area and its upstream and downstream sections were divided into four areas, and traffic control was carried out in the key lane-changing area and cooperative merging area. In the upstream lane-changing area, based on the lane change rules of minimum safe following headway and speed benefit, the vehicles in the outer lane and the middle lane of part of the mainline could change to the adjacent inner lanes in the upstream of the merging area in advance, so as to reduce the traffic pressure on the outer lane of the merging area and improve the merging efficiency. In the downstream cooperative merging area, the appropriate cycle time was chosen. With the maximum speed of merging vehicles during the cycle time as the goal, the longitudinal trajectory of the merging vehicle was planned without a fixed merging point, and the ramp vehicles were guided to merge into the mainline at the end of the cycle, so as to realize cooperative merging. The cooperative merging control method was verified by SUMO and Python simulation, and the sensitivity analysis of critical car-following headway was conducted. Simulation results show that compared with uncontrolled natural merging, the proposed cooperative merging control method can increase the average speed of vehicles by 4.9%-21.1% and reduce the average delay of vehicles by 29.9%-56.5% under different traffic demand levels, and it ensures that no vehicle stops. Compared with first-in first-out merging control, the proposed cooperative merging control method can increase the average speed of vehicles by 3.4%-9.6% and reduce the average delay of vehicles by 22.9%-39.4% under high ramp traffic demand levels. Furthermore, the lower critical car-following headway can improve the traffic efficiency in the merging area, and it is more obvious under the high demand level of mainline traffic.More>

2023, 23(6): 270-282. doi: 10.19818/j.cnki.1671-1637.2023.06.018

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Vehicle long-term target tracker optimized by improved carnivorous plant algorithm

HUANG He, LI Wen-long, YANG Lan, WANG Hui-feng, RU Feng, GAO Tao

Abstract: The mechanism of the swarm intelligence (SI) algorithm related to target tracking was studied. The fast histogram of oriented gradients (FHOG) of the tracking region was extracted as a feature template, and a carnivorous plant algorithm (CPA) was employed to search for the target's position in the image search region. A tracking framework based on the CPA was designed using the Bhattacharyya distance as the similarity function for template matching. Considering the complexity situations in the actual tracking process, such as the occlusion and busy background, a short-term memory module was designed to predict the individual initialized by the CPA during the tracking. This module, utilizing a Gaussian distribution, predicted the motion trajectory according to the target's position in the first two frames of the video sequence. To better optimize the target tracking with the CPA, a random tracking strategy and a population division mechanism were developed in the iterative process and integrated into the tracking framework as a search strategy. To make up for the poor representation ability of the single feature of the target by the FHOG, Conv2-1 and Conv4-1 features of ResNet-50 were integrated on the basis of the FHOG. A dynamic update template of the adaptive learning rate was designed based on this fused feature. A two-dimensional scale perception factor was added to the population dimension, allowing the aspect ratio of the target window to vary, so as to better adapt to the change in the scale of the target window. Analysis results show that the introduction of the random tracking strategy and population division mechanism significantly improves the iteration speed and optimization capability of the CPA. The fused feature and adaptive template update enhance the representation of target features, addressing the issues related to learning abundant irrelevant information due to the occlusion and preventing feature template degradation. The proposed algorithm demonstrates notable performance in tracking challenging vehicle video sequences from UAV123. The precision and success rate are 0.81 and 0.58, respectively, with a speed of 11.05 frames per second. Compared with the algorithms in similar literature, the tracking accuracy and robustness of the proposed algorithm improves substantially, making it adaptable to environmental change in complex scenes and ensuring a stable long-term tracking of target vehicles.More>

2023, 23(6): 283-300. doi: 10.19818/j.cnki.1671-1637.2023.06.019

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Group airport passengers travel recommendation method based on secondary induction

CHAI Lin-guo, RUI Tao, SHANGGUAN Wei, CAI Bai-gen

Abstract: In view of the personalized travel needs of passengers and the requirements of rapid airport evacuation, a travel recommendation method for group airport passengers based on the secondary induction was proposed on the basis of the fixed allocation of each travel mode of landside transportation, so as to provide algorithmic support for customized passenger services. Based on the original passenger data, and combined with the rough set theory, the knowledge reduction of feature attributes was carried out to improve the performance of the algorithm. The improved Bayesian classification algorithm was used to quantify the travel mode recommendation degree based on the calculation of the independent feature probability of passengers, and the passenger travel recommendation sequence based on the primary induction was generated. In view of the constraint of fixed capacity allocation of each travel mode on the landside of the airport, the passenger travel recommendation sequence was input into the secondary-induced travel recommendation model of passengers based on the improved non-dominated sorting genetic algorithm (NSGA-Ⅱ) to deeply match the transport capacity and passenger flow, and the passenger travel recommendation results were optimized again. Based on the principle of universality, the small-scale (100 people) and large-scale (1 000 people) passenger samples were used for model validation. Analysis results show that good results can be obtained under the inputs of passenger flows with different scales. The correct rate of passenger travel mode recommendation in the small-scale sample is 77.41%. Under the large-scale sample, the correct rate of passenger travel mode recommendation is 79.62%. After the secondary induction, the matching degree between the recommended travel distribution of passenger flow and the transport capacity greatly improves compared with the real travel and the primary induction distribution. On the basis of high matching between the passenger flow and the transport capacity, the passenger travel preference needs are realized. The algorithm has good performance and provides a practical method to improve the passenger flow evacuation of hub airports.More>

2023, 23(6): 301-313. doi: 10.19818/j.cnki.1671-1637.2023.06.020

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Adjacent cross-coupling synchronous formation control with collision avoidance for multiple ships under unknown disturbances

TUO Yu-long, KANG Cai-xia, WANG Sha-sha, DAI Dong-chen, GAO Shuang, LI Li-li

Abstract: In view of the poor synchronization performance and obstacle collision risk during formation navigation under unknown marine disturbances, a distributed adjacent cross-coupling synchronous formation robust control method with collision avoidance was proposed for multiple ships, and an adjacent cross-coupling synchronous control strategy was proposed to achieve higher synchronous control accuracy, and the unknown marine disturbances were estimated by the neural network. In order to effectively prevent collision risks between ships and obstacles, as well as between ships, the artificial potential field method was applied to the multi-ship formation control system. The effectiveness of the proposed method was tested by simulating the parallel formation navigation scenarios of five ships facing multiple obstacles and unknown marine disturbances. Research results show that all ships can navigate in the expected formation after safely avoiding the obstacles in considering obstacles and external marine disturbances. After about 9 s, the ships can reach consistent velocities. Although the velocities of the ships fluctuate slightly when there are obstacles, the ships are able to continue navigating with consistent velocity after 30 s. Besides, there also exist small oscillations in the position and velocity tracking errors, position synchronization errors of adjacent ships, and neural network approximation errors. However, these errors can eventually converge to 0 after 30 s, ensuring the synchronization of the position and velocity information of the five ships. Therefore, the proposed method can not only solve the problem of poor synchronization performance when ships are sailing in formation under unknown marine disturbances, but also effectively reduce the collision risk between ships and obstacles, as well as between ships. To some extent, the autonomy and safety of the ships during formation navigation have been improved.More>

2023, 23(6): 314-326. doi: 10.19818/j.cnki.1671-1637.2023.06.021

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2023 Vol. 23, No. 6

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