Journal of Chongqing Jiaotong University(Natural Science)

Intelligent Evaluation Method of Marine Engine Simulator Based on TOPSIS-Vague Set

CAO Hui1, LIANG Shiyuan1, ZHAO Hui2, SHEN Henglong1, JIA Zhiwei1

2022, 41(11): 1-6. DOI: 10.3969/j.issn.1674-0696.2022.11.01

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Aiming at the problem that the existing evaluation methods of marine engine simulator can’t objectively and accurately reflect the actual operation level of the personnel to be assessed, an intelligent evaluation method based on operation data was proposed. Based on the C-OWA operator weighting method, experts were invited to determine the subjective weight of the indicators. At the same time, the objective weight was calculated by the coefficient of variation method according to the operation data. The minimum discriminant information principle was selected to calculate the combined weight. The evaluation items of a typical marine engine simulator were ranked according to TOPSIS-Vague set scheme. The calculation results show that the TOPSIS-Vague set method based on the combined weight can be well used for intelligent evaluation of marine engine simulator.

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Review on Green Job Scheduling Optimization of Container Terminals

DONG Mingwang, HUANG Linfu, GU Yong

2022, 41(11): 7-14. DOI: 10.3969/j.issn.1674-0696.2022.11.02

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Container terminal was the key to promote the construction of green ports, and it was particularly important to carry out research on green job scheduling. The research literature on green operation scheduling optimization of traditional container terminals and automated container terminals was reviewed. The green operation scheduling problems of traditional container terminals and automated container terminals were analyzed and compared from a single operation link and multiple operation links. Suggestions for future research directions were also proposed, involving research objects, research goals, solving algorithms and so on. With the development and application of new energy driven technology for pord equipment, the job scheduling problem of energy management and operation management integration should be studied on the basis of considering the supply and use of new energy.

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Numerical Study on the Influence of Water Surface Gradient on Ship Sailing Resistance

JI Nan, YANG Guang, SHU Linzhao, QIAN Zhipeng, YANG Chun

2022, 41(11): 15-24. DOI: 10.3969/j.issn.1674-0696.2022.11.03

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The water surface gradient is one of the important factors that affect the hydrodynamic performance of ships. In order to reveal the hydrodynamic characteristics of the ship when it encountered the water surface with slopes, the computational fluid dynamics (CFD) method was used to analyze the influence of water surface gradient on the ship sailing resistance and floating state. Based on RANS equation, VOF method was used to capture the free surface and release the two degrees of freedom of heave and trim. Firstly, the resistance of the ship at different trim angles was calculated and compared with the test, to verify the accuracy of the simulation method to calculate the relationship between ship floating state and resistance. Then, by changing the longitudinal contraction angle and inlet velocity of the river section, the variation rules of ship resistance, floating state, wake and other parameters caused by the change of water surface gradient were obtained. The results show that: the computational fluid dynamics (CFD) method can be used to simulate the change of resistance and navigation characteristics when the ship encounters the water surface gradient, and to evaluate the navigation ability of the ship. The total resistance of the ship increases with the increase of the gradient. The gradient has little effect on the friction resistance. At high flow velocity, the friction resistance decreases to a certain extent with the increase of gradient. The main cause of the increase of the total resistance is that the proportion of the pressure resistance in the total resistance increases with the increase of the water surface gradient, which will increase the difficulty of ship navigation. The relevant research results can provide some reference for the safety decision-making of ships sailing on the surface with gradient.

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Variable Speed Limit Control Method for Accident Bottleneck Region on Freeway

XU Jianmin, LIAO Dongmei, MA Yingying

2022, 41(11): 25-33. DOI: 10.3969/j.issn.1674-0696.2022.11.04

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In view of the deterioration of traffic situation caused by sudden traffic accidents on expressways, three scenarios were set according to the distance between the accident location and the upstream entrance ramp. Firstly, the traffic capacity of bottleneck in different scenarios were analyzed. Then, based on the feedback control model, the vehicle was subject to hierarchical speed limit control and the setting position of variable speed limit control in low-speed section in different scenarios was discussed. Variable speed limit (VSL) control methods under three scenarios were constructed respectively. According to the principle of cell transmission model (CTM), the secondary development simulation of VISSIM was carried out to verify the control performance of each scenario under different traffic conditions. The results show that the proposed variable speed limit control method can effectively improve the outflow flow of bottleneck section during the accident, homogenize the density between road sections, delay the occurrence time of congestion and reduce the duration of congestion, and effectively reduce vehicle delays and parking times. In scenario 2, the vehicle delays and stops are reduced by 46% and 14% respectively, when the input flow is 6 000 veh/h.

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Travel Mode Choice Model Based on TTB Considering the Indifference Threshold

ZHANG Xinjie1, GUAN Hongzhi2, SUN Kechao3

2022, 41(11): 34-40. DOI: 10.3969/j.issn.1674-0696.2022.11.05

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Indifference threshold is one of the important influencing factors in traffic demand forecasting. In view of the uncertainty of traveler’s path travel time and vehicle parking time, the travel mode selection model based on indifference threshold under uncertainty conditions was established, which took the travel time budget (TTB) as the selection standard of travel time for travelers. Moreover, the scenario of multiple users was also considered, and the influence of uncertainty on traveler’s choice behavior was analyzed. The research results show that when the indifference threshold is fixed, as the expected punctual arrival probability increases, more travelers will choose the way with high travel time reliability. When the indifference threshold is considered, the expected punctual arrival probability has less influence on the behavior of mode selection, and the greater the indifference threshold is, the smaller the influence is. In the case of multiple users, travelers who expect a higher probability of punctual arrival will have a larger travel time budget and are more likely to choose a more reliable way to travel.

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Establishment and Measurement of Demand Responsive Transit Operation Service Level Index System

ZHANG Ruhua, ZHAO Bing

2022, 41(11): 41-51. DOI: 10.3969/j.issn.1674-0696.2022.11.06

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Demand responsive transit emerges as a new type of public bus that is promoted by an increasing number of cities to cater to some travelers’ pursuit of convenient and comfortable transport experience. In order to scientifically and reasonably assess the demand responsive transit service level and reveal the advantageous and disadvantageous links of demand responsive transit during the operation process, the factors influencing the operation service level were extracted from three dimensions, including the service level of road segments, service level of stations, and service level on the bus. Then, an operation service level index system made up of nine measurement indexes was established. Two evaluation models, that is the demand responsive transit actual operation service level model based on the set pair analysis and the passenger satisfaction model based on the SEM, were proposed; and the conclusions obtained from the two methods were compared and analyzed. The results suggest that the actual operation service level is assessed to be “relatively high”, while the operation service level based on the passenger satisfaction is assessed to be “ordinary”.

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Bus Passenger Flow Collection Technology Based on Terminal Positioning Information

QUAN Wei, WANG Hua, MAN Yongxing,ZHUANG Xuyi

2022, 41(11): 52-57. DOI: 10.3969/j.issn.1674-0696.2022.11.07

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In order to accurately obtain the micro boarding and alighting data of bus passengers, to mine the residents’ bus travel characteristics, and to optimize the bus planning and operation decision-making, the bus passenger flow information collection technology was researched, which was based on the bus GNSS positioning information and the MAC address of the Wi-Fi module of the passenger mobile terminal. Focusing on the problem of redundant interference of a large number of MAC addresses during vehicle operation, an online passenger identification algorithm was proposed. Through analyzing the interference conditions, the MAC address of bus passengers online was recognized based on five feature levels of classification calculation, namely, the number of MAC address occurrences, K-means clustering, online duration, online displacement, and the maximum acquisition time interval. Integrating vehicle positioning information, combined with the opening rate correction coefficient, the bus OD was calculated, and the accurate boarding and alighting locations of some passengers were obtained. The research results indicate that, the results of the manual car-following survey verify that the proposed system can better provide the most timely and accurate bus travel data for the bus operation managers, compared with the bus IC card survey method, image (video) recognition and other methods.

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Front Vehicle Detection System Based on Convolutional Neural Network

QIU Chengqun1, LI Peirun2, YANG Feng3, ZHU Rui1

2022, 41(11): 58-63. DOI: 10.3969/j.issn.1674-0696.2022.11.08

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In view of the situation that vehicles are partially blocked by green belts, roadblocks and other vehicles and encounter low lighting, which brings great difficulty to the field image detection of vehicles, a convolutional neural network algorithm was proposed to detect vehicles. The geometric model of the vehicle was defined based on the computer vision system, including the shape of the vehicle, the symmetry and the shadows it produced. Target detection and data processing technology of convolutional neural network algorithm in deep learning was adopted as the algorithm of the proposed system. The convolutional neural network was applied to detect obstacles in front of vehicles. By comparing different sampling convolutional neural networks, a convolutional neural network to detect vehicles ahead was designed. Through the design and testing of the proposed system, the algorithm of detecting the vehicle in front can ensure the rapidity and the accuracy. The experimental results show that the convolutional neural network with overlapping sampling and pooling layer of Max+Ave+Ave structure has relatively high accuracy and stability.

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Bending Moment Separation Method for Failure History of Single Ring Shield Tunnel

DONG Xinping1, CHEN Xiaoyang2, CHEN Hao2

2022, 41(11): 64-71. DOI: 10.3969/j.issn.1674-0696.2022.11.09

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Based on the incremental analytical solution for the failure history of single ring shield tunnel, the segment joint effect bending moment separation method was derived, and the principle, function, effect, implementation method, verification method and application effect of the moment separation method were analyzed. The research shows that the bending moment separation method can quantify and trace the influence of specific segment joints on the internal force (bending moment) of segments. At the low load level stage, the bending moment separation method can establish an explicit functional relationship between the segment bending moment and the elastic rotational stiffness of the segment joint. At the high load level stage, the incremental expression of the bending moment separation method can trace the internal relationship between the segment bending moment and the nonlinear rotational stiffness of the segment joint. In the failure history of single ring shield tunnel, the influence of segment joints at different locations on the internal force (bending moment) of segments is obviously unbalanced. The increase or decrease of segment bending moment at a specific location and its variation range are dominated and controlled by a few key segment joints. Different segment positions lead to different segment joints that play a leading and controlling role in segment bending moment changes.

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Multi-scale BIM Forward Design of Steel-Concrete Composite Beam

CAO Bingyong, SHI Xinxin, CHEN Shasha, DONG Bing, CUI Xiaojian

2022, 41(11): 72-80. DOI: 10.3969/j.issn.1674-0696.2022.11.10

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Firstly, aiming at the specific requirements of forward design for the steel-concrete composite beam, a multiscale BIM modeling method was introduced, and a model grading scheme based on level of development (LOD) was proposed. Firstly, through the structure tree framework and naming rules, the linkage mechanism of hierarchical models was established to achieve effective transfer of model data at different levels of granularity. Secondly, the basic process of multiscale BIM forward design for steel-concrete composite beam was proposed on the basis of BIM platform, which realized the semi-automatic design of elevation, section and plane of the steel-concrete composite beam by the embedded design logic and construction principles. And the decision table was used to solve the problems of understanding deviation and condition omission under the combination of multiple logic conditions. Finally, the corresponding BIM models according to different LOD were generated, and the model instantiation efficiency was tested. The results show that the application of multi-scale BIM forward design method in the design of steel-concrete composite beams can effectively improve the efficiency of forward design and the reusability of three-dimensional models.

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Fatigue Causes and Structural Optimization of Web Weld of Main Girder in Steel Plate Girder Bridge

YAO Yue, JI Bohai, YANG Liangze, FU Zhongqiu

2022, 41(11): 81-88. DOI: 10.3969/j.issn.1674-0696.2022.11.11

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In view of the fatigue cracking problem of the web weld of the steel girder of the steel plate composite beam bridge, the global model of four-span continuous steel plate composite girder bridge and the segment model of steel girder with small cross beam were established. The out-of-plane deformation characteristics of the typical cracked web gap were analyzed, and the stress characteristics of the welds between the web plate and the vertical stiffener under different structural forms were compared to identify the cause of fatigue cracking and the mechanism of out-of-plane deformation. Based on the above cause analysis, a structural optimization method to improve the fatigue resistance were proposed. The results show that the transverse stiffeners have a “pull” effect on the web of the main beam towards the inner side of the main beam and vertically downward, which is the direct cause of the out-of-plane deformation of the web gap. The method of cutting the bottom of transverse stiffener could reduce the local peak stress by more than 80%, which can effectively relieve stress concentration and reduce fatigue damage caused by external load.

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Effect of Bond Condition of Beam Longitudinal Bars on Seismic Performance of Slag Geopolymer Concrete Beam-Column Joints

MAO Yuguang1,2,3, LIU Yuzhong1,2,3, DU Yunxing1,2,3, SU Jie1,2,3, HU Xiang1,2,3, SHI Caijun1,2,3

2022, 41(11): 89-98. DOI: 10.3969/j.issn.1674-0696.2022.11.12

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To investigate the effect of beam longitudinal bars bond condition on the seismic performance of slag geopolymer concrete (GC) beam-column joints, one common concrete beam-column joint specimen and three geopolymer concrete beam-column joint specimens with different bonding conditions were prepared, and low cycle repeated loading tests were carried out. The crack development trend, failure mode, hysteretic curve, and strain values of beam longitudinal bars of joint specimens were analyzed. Seismic performance, including ductility, strength and stiffness degradation, energy dissipation capacity, and shear deformation of joint specimens, was discussed. The results show that: under the action of low cycle repeated load, the low bond strength of beam longitudinal bars and the large slip of beam longitudinal bars make the seismic performance of joints in geopolymer concrete worse than that in ordinary concrete. Increasing the axial compression ratio or increasing the length of the beam longitudinal reinforcement penetration can improve the bonding condition of the joint beam longitudinal reinforcement in the GC joints, which further improves its seismic performance. According to the blank of the limiting conditions of joint bond conditions of geopolymer concrete in GB 50010-2010 Code for Design of Concrete Structures, the recommended values are proposed.

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Material Design and Performance Study of Concrete Based on Particle Interference Theory

WANG Ruiyan1,2, ZHANG Ying1, LONG Hao3, ZHANG Zhaochen1, WANG Ziyi1

2022, 41(11): 99-104. DOI: 10.3969/j.issn.1674-0696.2022.11.13

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According to the design requirements of cast-in-place wet joint concrete material for the bridge deck of Chongqing Jialing River Shuitu Bridge, the aggregate composite gradation design was carried out by using particle interference theory. And on this basis, the influence of spreading coefficient on concrete performance was studied. The research indicates that: the aggregate can reach the maximum bulk density when the particle size ratio is 1:8 by using particle interference theory for aggregate composite gradation. The workability of concrete mixture is adjusted by changing the spreading coefficient and adjusting the volume of cementitious material paste. When the spreading coefficient is between 1.10 and 1.20, the workability of concrete mixing is good, and the fluidity of mixing increases with the increase of spreading coefficient. When the spreading coefficient is 1.18, the comprehensive performance of workability and strength is the best. According to the recommended dosage of calcium sulfoaluminate and calcium oxide expansion agents, the performance of concrete can meet the engineering requirements for shrinkage compensation.

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Concrete Crack Identification Method and Program Development

YANG Shasha1,2, HAO Long3, LI Ying3, FU Shaojun2,4, HE Changhai5

2022, 41(11): 105-111. DOI: 10.3969/j.issn.1674-0696.2022.11.14

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The acquired RGB image of concrete surface crack was grayed, filtered and segmented by MATLAB software to obtain a binary grayscale image. Then, crack judgment and segment connection processing were carried out. The crack area, length, maximum width and other parameters of concrete structure surface were calculated. A digital-image-based recognition program for surface cracks of concrete structures—IPCW was developed. The IPCW was verified by an example of shallow surface crack identification in a concrete dam project. The research indicates that the relative error between the crack width value identified by IPCW and the measured value is generally within 11%, and the identification accuracy meets the engineering requirements. IPCW has great advantages in searching for cracks in a wide range and can be applied to the preliminary inspection of cracks in civil engineering.

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RAP Heating Uniformity of Hot Recycled Asphalt Pavement Maintenance Vehicle

CAO Yuanwen1, HUANG Xingsheng1, LI Cheng1, WU Peng2, QIU Xiaojun2

2022, 41(11): 112-117. DOI: 10.3969/j.issn.1674-0696.2022.11.15

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Aiming at the heating uniformity of the reclaimed asphalt pavement (RAP) of the hot recycled asphalt pavement maintenance vehicle, three-dimensional models of the mixing and heating mechanism of the maintenance vehicle before and after improvement were established. According to the discrete element method and heat transfer theory, the mixing and heating process of RAP with different stirring and heating devices was simulated with the help of EDEM software. The temperature distribution and temperature change rule of asphalt mixture before and after improvement were obtained through comparative analysis of construction site tests. The results show that: the addition of the three-blade spiral stirring knife can reduce the variance of the temperature distribution of the mixture, and the uniformity of stirring and heating is better. As the spiral angle of the outer circle of the spiral blade of the three-blade spiral stirring knife increases from 30° to 35°, the temperature variance of the mixture decreases from 8.62 to 8.37, and the heating efficiency addition increases from 1.26% to 4.70%. The heating efficiency of the stirring and heating device with a 35-degree spiral stirring knife is increased by 29.73% compared with the original stirring and heating device.

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Influencing Factors on Shear Performance of Gussasphalt Mixture Based on Triaxial Shear Strength

WANG Min1, WANG Hao1, XIAO Li2, YANG Xinyao1, WANG Tao2

2022, 41(11): 118-122. DOI: 10.3969/j.issn.1674-0696.2022.11.16

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In order to research the influence of material composition, temperature and loading speed on the shear performance of gussasphalt, triaxial shear test was used to test the maximum failure load and its corresponding axial deformation of gussasphalt. Based on Coulomb-Moore theory, the shear strength parameters such as cohesion c, internal friction angle φ and shear strength τ were calculated. The research results show that: For three kinds of composite modified asphalt mixtures, the shear strength of the mixture is polymer composite modification>lake asphalt composite modification>hard asphalt composite modification. The shear strength and parameters of polymer composite modified asphalt mixture are the largest and the comprehensive shear performance is the best. With the increase of the asphalt aggregate ratio, the internal friction angle is gradually decreased, and the shear strength and cohesion first increase and then decrease, reaching the maximum value respectively when the asphalt aggregate ratio is 7.8% (τ= 1.15 MPa, c=0.82 MPa）. The shear resistance of the mixtures with medium gradation is the best. When the gradation is changed from fine to coarse, the cohesion and shear strength increase at first and then decrease, and the influence is more significant. It can be seen that the shear resistance of gussasphalt with suspended dense structure depends more on the bonding effect. Temperature is the most significant factor affecting the shear performance of the mixtures, and the shear strength and cohesion gradually decrease with the increase of temperature. When the temperature rises from 25 ℃ to 60 ℃, the shear strength and cohesion decrease by 33% and 37% respectively. The internal friction angle decreases with the increase of temperature, but the change trend is not obvious. The shear resistance indexes gradually increase with the increase of the loading rate, but the trend is relatively slow. The internal friction angle has little effect on the loading rate, and the maximum difference is only 1.52°. Compared with other factors analyzed, the loading rate has no significant effect on the shear strength of the mixture.

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Settlement and Deformation Control of Overlying Pipe Culvert under Approach Channel of Ship Lock in Coastal Area

PAN Guohua1, ZOU Kunyi2, ABI Eedi2, LIU Mingwei2, KONG Zengzeng1

2022, 41(11): 123-130. DOI: 10.3969/j.issn.1674-0696.2022.11.17

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The intersecting of the culvert and the approach channel of the lock in coastal area is easy to cause the uneven settlement, structural cracking and water stop failure of the culvert, which will affect the stability of the culvert structure. Aiming at the deformation and control problem of overburden culvert structure under approach channel, a simulation model of the whole construction process of the culvert was established by using the numerical simulation method. Combined with the field measured data, the settlement law and deformation control effect of the culvert under different construction loads and foundation reinforcement schemes were analyzed. The research results show that the small strain plastic hardening model can be used to simulate the whole process of pipe culvert construction in coastal area. In the case study, the average settlement of the pipe culvert exceeds the allowable value due to the uneven load on the pipe culvert. The foundation treatment scheme of the culvert with bored cast-in-place pile is proposed to enhance the foundation stiffness and effectively reduce the settlement of the culvert. Uneven settlement will still occur in the box where the foundation treatment is different, resulting in differential settlement between the structural joints of the box. Affected by the excavation and unloading of the approach channel, the pipe culvert under the approach channel has an upward displacement, which reduces the uneven settlement of the box and the settlement difference at the structural joints, and is conducive to the stability of the pipe culvert. The proposed deformation control scheme of pipe culvert meets the engineering requirements.

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Characterization of Three-Dimensional Water Temperature Distribution in the Channel of Tongluowan Section of the Lower Minjiang River

LI Wenjie1, FAN Yuqi2, DAI Zhuo2, YANG Wei1, YANG Shengfa1

2022, 41(11): 131-136. DOI: 10.3969/j.issn.1674-0696.2022.11.18

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Water temperature is a key ecological factor affecting fish and their habitat, and its changes have a significant impact on fish physiological processes and behavioral patterns. The Tongluowan river section was located in a national nature reserve for rare fishes in the upper reaches of the Yangtze River, and the water temperature was an important factor to be considered in the construction of Minjiang ecological waterway. The hydrodynamic module of MIKE 3 software was used to simulate the three-dimensional water temperature structure of the water body in the Tongluowan section of the lower Minjiang River under the lowest design water level condition. The simulation values of three points were taken and verified by the measured data that the proposed model had relatively high reliability. The research results show that the water temperature stratification characteristics exist in the side beach area on both sides of the water body in the Tongluowan river section, and the water temperature values are higher than those in the channel area which is more favourable to the survival of fish. The water temperature at the deep pits of the side beach is more constant and closer to the suitable water temperature for the main fish in the lower reaches of Minjiang River, and the bottom environment of the water body is more favorable for benthic fish to feed and spawn. It is recommended to minimize the engineering measures such as reef blowing and excavation of the riverbank in the Tongluowan river section to reduce the impact on fish habitat.

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Thermal Management of Lithium-ion Battery Liquid Cooling Module Based on High Temperature Uniformity

TANG Zhiguo, ZHAO Renchen, ZHAO Zhijian, WANG Shoucheng

2022, 41(11): 137-144. DOI: 10.3969/j.issn.1674-0696.2022.11.19

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In order to improve the temperature uniformity of the thermal management module of the lithium-ion power battery, a structure of liquid-cooled power battery thermal management module based on the gradient increase of the contact surface radian angle of the heat-conductive block (referred to as the contact angle) was established. Based on the experimental verification of the thermal model of the single cell, a method of numerical calculation was used to study the influence of the contact angle (αi), the contact angle gradient (Δα) and the coolant inlet velocity (v) on the cooling performance of multiple single cells in the module. The research results indicate that simply increasing αi could reduce the maximum temperature (Tmax) of the battery in the module, but it will cause a decrease in its temperature uniformity. While the gradient change of αi is adopted, the temperature uniformity of the battery in the module could be effectively improved, and the uniformity increases with the increase of the Δα value. And in the case that αi is gradient changed, there is a v that can further improve the temperature uniformity. When Δα is 15° and v is 0.01m/s, the maximum temperature difference (ΔTmax) of the battery in the module discharged at a rate of 3C can be reduced to below 4 ℃.

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Parameter Matching Design and Control Strategy of Dual Drive Powertrain for Pure Electric Vehicle

LI Shengqin, DING Xuemei, YU Bo

2022, 41(11): 145-152. DOI: 10.3969/j.issn.1674-0696.2022.11.20

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How to determine the motor working mode and ensure that both motors work in the working range with the optimal efficiency is the focus of the research on the power transmission system of pure electric vehicles with double motors driven. Aiming at the pure electric vehicle driven by dual motor coupling, the powertrain parameter matching design was carried out, and the control strategy of power transmission was proposed based on the principle of optimal efficiency. Firstly, according to the dynamic requirements of the target vehicle, the parameter matching design of the motor and battery of the power system was carried out, and the simulation model was established by CRUISE software to simulate and verify the maximum speed and climbing performance of the vehicle. Then, according to the driving efficiency of power transmission system, the optimal working point of motor was solved by sequential quadratic programming optimization algorithm, and the multi-mode switching dual electric power distribution control strategy was proposed. Finally, a co-simulation model was established to verify the proposed efficiency optimal control strategy. The results show that under the optimal control strategy of transmission system efficiency, the power performance and economy of the whole vehicle are improved, and the energy utilization rate is better. Under the typical cycle conditions of WLTC, the average efficiency of the dual motor coupling drive system is 85.9%. And the motor working point with the efficiency of the drive system greater than 85% accounts for 55% of the whole working range, and the dynamic performance of the vehicle is improved. The research can provide a theoretical basis for the design of power transmission system and the research of control strategy of pure electric vehicle.

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Intelligent Vehicle Trajectory Planning Algorithm Based on Improved Artificial Potential Field Method

ZHAO Fengkui,GE Zhen ,DONG Fengwei, ZHANG Yong

2022, 41(11): 153-160. DOI: 10.3969/j.issn.1674-0696.2022.11.21

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Trajectory planning, as a key module of behavioral decision-making and bottom-level control, determines whether the automatic driving command of intelligent vehicles can be successfully executed. In review of the problem of current trajectory planning algorithm that it didn’t consider the actual driving characteristics of the vehicle, such as the maximum angle of the front wheels at different speeds and the condition whether the trajectory of the vehicle was smooth when avoiding obstacles, an improved artificial potential field method was proposed. Kinematic constraints based on two degree of freedom model of vehicle were added, so that the path planning algorithm could plan the path adapted to different vehicle speeds. The vehicle movement space was set as a secondary highway, and the road constraint with lane keeping function was set. In order to make the curve smoother and could guide the vehicle to avoid obstacles, the traditional circular obstacle model was changed to the irregular elliptical obstacle model based on a safe distance model of overtaking. Finally, MATLAB was used to simulate. The comparison experiment shows that the improved scheme can better complete the overtaking path planning of vehicles on structured roads, and the path is smoother when vehicles make obstacle avoidance and lane change behavior.

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