Journal of Chongqing Jiaotong University(Natural Science)

Design of Integrated Simulation Platform for Traffic Signal Control Based on Scene Driven

ZHANG Lili, WANG Li

2020, 39(01): 1-7. DOI: 10.3969/j.issn.16740696.2020.01.01

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In view of the problems of small scale, slow speed and difficult to realize signal strategy in traditional urban road traffic signal control simulation, and the contradiction of largescale parallel realtime evolutionary computing requirements proposed by the multiscene overlapping traffic signal control simulation in the future, the integrated simulation platform of traffic signal control based on scenedriven was designed and developed, by reconstructing the open source traffic simulation engine and the hardware and software framework of signal control equipment. Through the design of a standardized API interface, the simulation requirements of urban road traffic control driven by multiscenes could be realized. Based on the road network of Shunyi District and Weifang City, the performance of the integrated simulation platform was tested by the simulation of different scales of the fleet. The research results show that the road network simulation of the proposed simulation platform is large in scale, good in realtime performance, stable in performance and reliable in operation, which can be used for urban traffic signal control requiring largescale realtime simulation.

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Recognition on Invaders into Automobile Proving Ground Based on Convolution Neural Network

XIANG Huarong1,2，ZENG Jing1,2

2020, 39(01): 8-14. DOI: 10.3969/j.issn.1674-0696.2020.01.02

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In order to recognize and alarm invaders which entered into automobile proving ground, Faster-RCNN framework was established by Tensorflow, combining with current video monitoring system. InceptionV2 and ResNet101 were taken as core convolution neural network respectively. The final training was carried out with the self-built annotation data set, and the migration test was carried out with the obtained model. The experimental results show that the average precision value of InceptionV2 system and ResNet101 system reaches 81.7% and 84.1% respectively. The joint test combining the two systems with the image capture function of Opencv and current video monitoring system was carried out. The results prove that both systems can recognize, classify, mark and alarm the high-speed or low-speed moving objects in real time under cloudy weather or low-pixel camera condition.

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Pedestrian-Vehicle Conflict Probability Estimation at Uncontrolled Crosswalks

MA Yingying, WEN Chen, LU Siyuan

2020, 39(01): 15-22. DOI: 10.3969/j.issn.1674-0696.2020.01.03

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In order to estimate the pedestrian-vehicle conflict probability during the design stage and provide a basis for safety assessment of pedestrian crossings, taking uncontrolled crosswalk as the study objective, a pedestrian-vehicle conflict probability estimation model based on the arrival volume and operation characteristics of pedestrians and vehicles was developed by estimating the probability of vehicles and pedestrians appearing at each section of the variation crosswalk. Then the proposed model was applied to analyze the variation characteristics of the conflict probability of each section of the crosswalk. The results show that: the pedestrian-vehicle conflict probability increases with the increase of pedestrian and vehicle arrival volume; the distribution of pedestrian-vehicle conflict probability within a lane is related to the lateral migration of vehicles; the proposed conflict probability estimation model is consistent with the actual situation.

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Mechanism and Signal Light Setting of the Rear Car Running the Red Light by Mistake Caused by the Front Car Blocking

HAN Baorui1,DING Lisha1,LI Ying2,GUAN Chenfeng1,ZHOU Yu1

2020, 39(01): 23-27. DOI: 10.3969/j.issn.1674-0696.2020.01.04

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Aiming at the phenomenon of running the red light caused by small cars following large vehicles at the end of the green light period, whether the unreasonable position of the signal light will cause the forced red light running by mistake was studied. Based on the traffic flow data of an intersection in Nanjing, the conclusion that sight occlusion may have a significant impact on the distribution of speed and headway of the following vehicles was obtained by the single factor analysis of variance. Based on the premise that the car can find the signal light in time and brake safely, the geometric relationship of the sight between the vehicle and the signal lamp was analyzed. The range of setting height of signal lamp based on the reasonable following distance was discussed, and two kinds of car-following condition models were built, which could protect drivers from running the red light. The research results show that the adverse effect of the large vehicle on the sight blocking of the following car can be eliminated, when the signal lamp is moved to the parking line of the entrance lane.

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Safety Analysis of Different Vehicle Types in Urban-Rural Binding Regions Based on Logit Model

NIU Shifeng1, LI Guiqiang2, LIU Enquan3

2020, 39(01): 28-33. DOI: 10.3969/j.issn.1674-0696.2020.01.05

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Compared with urban areas, urban-rural binding regions have the characteristics of frequent accidents and high severity. Although the effort has been made in many ways, the effect is limited. The urban-rural binding region has become a key bottleneck area that affects Chinas traffic safety. The accident data of the urban-rural binding regions of a city in the past three years were collected, and the vehicle CWI(crash worthiness index) and CAI(crash aggressivity index) were introduced as the vehicle type safety indexes.Based on the polytomous ordered Logit model, the safety analysis method of different vehicle types in the urban-rural binding area was designed, and the safety of each vehicle type was determined.The influence of various factors on vehicle safety was analyzed in depth, and the relevant improvement suggestions were put forward.

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Analysis and Countermeasure of Multimodal Coordinated Development of High-Speed Railway Transportation Channel —— A Case Study of Yunnan High-Speed Railway

LIU Lan1，2, ZHANG Sijia1，RONG Tengfeng1,ZHANG Jun1

2020, 39(01): 34-39. DOI: 10.3969/j.issn.1674-0696.2020.01.06

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In order to effectively cope with the impact of the operation of high-speed rail on the regional transportation patterns, a multimodal partaking rate improved Logit model of high-speed rail transportation channel was constructed by introducing channel utility amplification factor named a. The choice of passenger transportation mode was studied. The multimodal partaking rate before and after the opening of Kunming-Nanning, Kunming-Shanghai and Kunming-Yuxi high-speed railway was solved and a comparative analysis was also carried out, so as to provide countermeasures for the multimodal coordinated development. The research results show that the proposed model has high reliability. As far as Yunnan Province is concerned, after the opening of high-speed railway, it is advisable to form a transportation pattern of “railway in series, highway expansion and air water connection”, so as to realize the coordination and cooperation of various transportation modes, and to develop towards the direction of “provincial highway-oriented, trans-provincial railway-oriented and air-oriented”.

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Prediction of Urban Rail Transit Station Inflows Based on ARIMA Model

ZHAO Peng1，LI Lu2

2020, 39(01): 40-44. DOI: 10.3969/j.issn.1674-0696.2020.01.07

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Passenger flow prediction is the foundation of the passenger transport organization, and the prediction results can provide the basis for decision making of operation management and emergency disposal. Aiming at the passenger flow prediction of urban rail transit, an autoregressive integral moving average ARIMA model was established for short-term prediction of station inflows, which was based on analyzing the periodic fluctuation law and change trend of the passenger flow in rail transit stations. Taking Beijing subway as an example, an empirical analysis was carried out. The seasonal ARIMA model meeting the requirements was used to carry out the short-term prediction of passenger flow, the actual passenger flow of Dongzhimen station was selected for model parameter calibration, and the passenger flow prediction of typical stations (terminal station, intermediate station, transfer station and interchange station) in the road network was carried out. The research results show that the average prediction error of ARIMA model is only 4%, which has high prediction accuracy and verifies the correctness of the prediction method.

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Modal Parameter Identification for Large Span Cable-Stayed Bridge Based on Improved Stochastic Subspace Identification

WEN Peng, CHEN Qiaofeng, YANG Fengfan

2020, 39(01): 45-50. DOI: 10.3969/j.issn.1674-0696.2020.01.08

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In practical engineering, in order to detect whether the bridge structure was in good operation state at any time, various types of sensors were usually installed on the bridge structure. The modal parameters were obtained by analyzing the response signals collected by the sensors, and the change law of modal parameters was analyzed to indirectly evaluate the operation state. Based on this, in order to improve the accuracy of modal parameter identification, aiming at the deficiency of the most commonly used modal parameter identification algorithm, stochastic subspace algorithm (SSI), a real modal selection algorithm was proposed, which took the frequency value, damping ratio and modal shape as the discriminant factors. Finally, the proposed algorithm was applied to identify the modal parameters for a large cable-stayed bridge. The recognition results show that the proposed algorithm can not only effectively realize the intelligent filtering of real modes, but also the recognition results are reliable.

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Steering Configuration of External Prestressed Tendon in UHPC Box Girder with Dense Diaphragms

LU Bangze1,2, SHAO Xudong1,2, QIU Minghong1,2, ZHOU Linyun1,2, ZHANG Yang1,2

2020, 39(01): 51-59. DOI: 10.3969/j.issn.1674-0696.2020.01.09

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In order to explore the reasonable configuration forms of external prestressed tendon steering block in the UHPC (ultra-high performance concrete) box girder bridge with dense diaphragms, the UHPC rib-shape steering block was proposed on the basis of the structural characteristics of the UHPC box girder diaphragms. On the background of a UHPC continuous box girder bridge proposed to be built in Guangdong Province, the control effect of UHPC rib-shape steering block on web stress under the prestressed tendon steering force was verified by establishing a linear elastic contrast model of whether or not to use diaphragm for steering. 5 kinds of local effects of the UHPC rib-shape steering block subjected to steering force were proposed. According to the calculation results, the full-scale test of UHPC rib-shape steering block was designed to observe the crack development, deflection change and failure mode. The nonlinear finite element model of the whole test process was established. The parameters of different reinforcement methods of the steering block were analyzed, and the reinforcement suggestions were put forward. The whole research results show that the nominal stress limit of UHPC rib-shape steering block with the design of crack resistance is 9.6 MPa. When the UHPC consumption is 0.2 m3, the steering force of external prestressed tendon of UHPC rib-shape steering block is up to 2,004 kN, and the durability of the structure is guaranteed.

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Simulation Analysis on Adhesive Anchorage of CFRP Cables Based on Tsai-Wu Criterion

LI Yang1, JIA Lijun2

2020, 39(01): 60-66. DOI: 10.3969/j.issn.1674-0696.2020.01.10

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In order to further study the proper design parameters of the adhesive anchorage for carbon fiber reinforced polymer (CFRP) cables, the Tsai-Wu failure criterion of composite material was introduced firstly, and the simulation analysis method of the adhesive anchorage for CFRP cables was proposed. Then, a parametric study on the anchorage performance indexes of adhesive anchorage for CFRP cables was conducted by use of the proposed method. The results show that the mechanical properties of the anchorage can be significantly improved by optimizing the total length of the anchor cup, the length of the straight tube section, the inclination angle of the inner cone section, the interval between CFRP bars and anchor cup, and by setting films between anchor cup and epoxy resin.

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Simulation Efficiency Analysis for Acoustic Wave Equation Based on Matrix Finite Difference Algorithm

DAI Zhili1,2，XIANG Zhongfu1,2，ZHOU Hui3

2020, 39(01): 67-71. DOI: 10.3969/j.issn.1674-0696.2020.01.11

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Ultrasonic wave is widely used in bridge detection, and its propagation process in the object is an important content in the research of ultrasonic imaging detection. The propagation process of ultrasonic can be simulated by computer simulation. And the finite difference algorithm is a common algorithm. To improve the simulation efficiency of the algorithm, a matrix finite difference simulation algorithm was proposed. When the simulation area was small, the proposed algorithm can greatly improve the simulation efficiency. Within a certain range, the simulation efficiency improvement rate was inversely proportional to the simulation area approximately. Finally, through the comparison of simulation results, it is concluded that the matrix finite difference algorithm has the same simulation results with the conventional algorithm, and has higher simulation efficiency.

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Rheological Property of Graphene Modified Asphalt and Its Burgers Rheological Model

LI Peng

2020, 39(01): 72-77. DOI: 10.3969/j.issn.1674-0696.2020.01.12

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Asphalt is a kind of viscoelastic material. Under high temperature conditions, the elastic component of asphalt will gradually decrease, while the viscous component will gradually increase, which improves the fluidity of asphalt. When subjected to repeated loads, the structure of asphalt concrete will change and eventually lead to rutting and other diseases. Graphene is a kind of two-dimensional carbon material with excellent mechanical properties, which has a wide and important application prospect. Therefore, it was proposed to try to add graphene into asphalt to improve the composition change and flow state of asphalt at high temperature, so as to improve the rheological properties of asphalt concrete at high temperature. The results show that the addition of graphene improves the transient elasticity of the asphalt and reduces the viscous components therein, so that the modified asphalt has good flow and resistance to deformation throughout the frequency range. Under the high-temperature irradiation environment in summer, the asphalt concrete pavement with graphene still has good anti-rutting and other anti-deformation ability after repeated rolling, which can reduce the maintenance cost of asphalt pavement in the later period and effectively extend the road performance and service life of asphalt concrete.

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Application of Waste Tire Rubber Powder in High-Viscosity Modified Asphalt

DONG Dawei1，LING Tianqing2，JIANG Kuan3，CHEN Lin4，ZHANG Liqun5

2020, 39(01): 78-84. DOI: 10.3969/j.issn.1674-0696.2020.01.13

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The feasibility of preparing high-viscosity modified asphalt with better performance by using rubber powder was studied by contrastive experiments. The results show that the high-viscosity modified asphalt meeting the requirements of the specification can be prepared by blending high mesh rubber powder with appropriate SBS, alkene polymer and petroleum resin, and the blending ratio was adding 12% 80 mesh rubber powder, 6% SBS, 2% Sasolbit wax and 2% terpene resin. In order to further reduce the cost, the feasibility of preparing high-viscosity modified asphalt from activated rubber powder was preliminarily explored. The test results show that the performance of high-viscosity modified asphalt can be greatly improved and the material cost can be greatly reduced by adding 25% desulfurized rubber powder (activation degree is about 50%), 6% SBS, 2% Sasolbit wax and 2% terpene resin.

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Performance of Waterborne Epoxy-Emulsified Asphalt and Its Mixture

WANG Jinyong1,2 ，CHEN Fei1,2 ，CHENG Xu3，MIAO Chaojie4， WANG Huoming1,2

2020, 39(01): 85-91. DOI: 10.3969/j.issn.1674-0696.2020.01.14

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(1. China Merchants Chongqing Communications Research & Design Institute, Chongqing 400067, China； 2. National Local Joint Engineering Laboratory for Road Engineering and Disaster Prevention and Reduction Technology in Mountainous Areas, Chongqing 400067, China; 3. School of Civil Engineering, Chongqing Jiaotong University, Chongqing 400074, China； 4. South Operation Branch, Chongqing Expressway Group Co., Ltd., Chongqing 401346, China)

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Mixing Ratio Design of Graded Crushed Stone Based on Shear Resistance

ZHENG Li,WANG Wei

2020, 39(01): 92-97. DOI: 10.3969/j.issn.1674-0696.2020.01.15

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Shear deformation of graded crushed stone material is the main failure form of graded gravel base. In order to reduce the occurrence of this kind of disease, a new method of mixing ratio design with shear resistance as the key control index was established by using self-developed direct shear test equipment and using safety factor as the design index. The new index of “safety factor” is derived from the necessary and sufficient conditions of Mohr Coulomb strength theory. The actual application results show that: the proposed index not only conforms to the shear failure mode of granular materials, but also can link the material design and structural design of granular materials such as graded crushed stone, which has strong theoretical value and practical application value.

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Numerical Simulation Study on the Improvement of Flow Pattern by Guide Wall Permeable Technology of Approach Channel

JIANG Ziwei1, 2, XU Guangxiang1, TONG Sichen1

2020, 39(01): 98-102. DOI: 10.3969/j.issn.1674-0696.2020.01.16

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It is of great significance to study the flow condition at the entrance area of approach channel, which will directly affect the safety of the ship. Based on Jinghong Power Station, the orifice outflow of permeable core wall at approach channel was equivalently turned into weir outflow through the principle of equal flow, and the multi-connected calculation domain was changed into the single-connected one. The proposed method was convenient for modifying plane node elevation, and it effectively solved the problem that the two-dimensional flow mathematical model was difficult to deal with the multi-connected domain boundary. The calculation results show that: the maximum reflux, maximum longitudinal flow and maximum transverse flow are weakened in different degrees after the boundary processing of core wall with permeable structure, and the weakening degree of maximum reflux is the most obvious, which is also consistent with the experimental results of physical model. It shows that the equivalent weir flow method is effective in dealing with this kind of boundary, and the calculation results are consistent with the actual situation.

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Laboratory Tri-axial CD Test of Cement Solidification for Soft Soil in Typical Area

QIN Wanggen1,2，CAI Zhengyin1，GUAN Yunfei1，LI Xiaomei1

2020, 39(01): 103-108. DOI: 10.3969/j.issn.1674-0696.2020.01.17

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In view of the problems such as the insufficient bearing capacity of foundation and the failure of slope on the soft soil foundation, the stress-strain characteristics, deformation laws, strength characteristics and failure forms of the cement soil were analyzed and studied by carrying out triaxial CD tests with different cement content and confining pressure in the laboratory. The test results show that: under the same confining pressure, with the increase of cement content, the shear strength of cement soil shows a nearly linear growth relationship; with the increase of confining pressure, the strain, shear strength and residual strength after failure of cement soil increase gradually; with the increase of cement content, the volume strain of cement soil increases first and then decreases, which has dilatancy characteristics and finally tends to a certain stable value. The failure mode of cement soil is related to cement content and confining pressure, which mainly presents as three failure modes, such as plastic shear failure (low ac/high po), brittle fracture failure (high ac/low po) and oblique shear failure {(low/high ac, high/low po)}.

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Comprehensive Assessment of Water Quality of Eight Rivers in Chongqing Main Urban Area

ZHANG Zhanmei1,2, LI Yuanli2, SHI Ruiqi2, HU Weiwei2

2020, 39(01): 109-114. DOI: 10.3969/j.issn.1674-0696.2020.01.18

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In order to understand the pollution situation of the rivers in the main urban area of Chongqing and provide some data basis and support for their future remediation work, eight secondary rivers in the main urban area of Chongqing were selected for water quality assessment with comprehensive water quality identification index method, taking CODMn, TP, TN, NH3-N, and DO as assessment indicators. The research results show that: the water quality of Huaxi River, Xiaojia River, Kuxi River, Huangxi River and Panxi River is within or superior to class V water quality standard of surface water in GB3838-2002, whereas that of the Qingshui Stream, Gailan Stream and Taohua Stream is inferior to class V, with poor overall water quality, but not yet to black smelly level. Moreover, it is confirmed that the river pollution is mainly caused by the eutrophication of TN, NH3-N and TP, in which the rivers with TN exceeding the water quality standard in the effluent functional area account for 100%, the rivers with NH3-N exceeding the standard account for 50%, and the rivers with TP exceeding the standard account for 37.5%.

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Sensitivity Analysis of Weld Parameters for Straddle-Type Double Axle Wide Wheel Bogie Frame

WEN Xiaoxia, KONG Dexu, DU Zixue

2020, 39(01): 115-119. DOI: 10.3969/j.issn.1674-0696.2020.01.19

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In order to overcome the problems of excess strength of base metal and insufficient strength of weld seam caused by the whole method in strength design of welded structure, a new finite element model of bogie frame with double axle and wide track width, including weld seam, was established. The static strength analysis was carried out by using the Optistruct module in Hyperworks, and the vehicle dynamics simulation model including the bogie was set up in the dynamic software Adams. According to the actual operation, the time load history of each key point for fatigue calculation was obtained by simulation. Considering the influence of notch stress and stress correction on the weld, the fatigue damage of the weld was analyzed, and the sensitivity of key weld parameters was analyzed. The results can be seen from the analysis that the influence of the weld penetration and weld thickness on the fatigue damage of the weld is decisive, and the influence of weld inclination angle is almost zero, and the effect of the notch size on the fatigue damage of weld is particularly critical.

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Influence of Split Injection on Spray and Combustion Characteristics of GDI Gasoline Engine

HE Yituan, TAO Youdong, ZHANG Pengbo, HONG Yun, REN Haigen

2020, 39(01): 120-125. DOI: 10.3969/j.issn.1674-0696.2020.01.20

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A three-dimensional simulation model of the GDI gasoline engine was established, and the spray and combustion models were verified through the constant volume bomb test and the engine bench test. The spray and combustion process adopting single, two-stage and three-stage injection strategies was simulated under 2000r/min full load conditions. The results show that the split injection strategy is beneficial for fuel evaporation; compared with the single injection strategy, the two-stage injection and three-stage injection strategy increase fuel evaporation by 15.6% and 19.5%, respectively. The single injection strategy forms homogeneous mixture at ignition time, while the two-stage injection and three-stage injection strategies form thick stratified mixture near spark plug and thin stratified mixture in other regions at ignition time. Compared with the single injection strategy, the peak value of cylinder pressure of the two-stage injection strategy has been greatly improved. The peak value of cylinder pressure of the three-stage injection strategy is further increased, which is 0.73 MPa higher than that of the single injection strategy. The two-stage injection strategy has a shorter flame development period and a longer combustion period. The three-stage injection strategy has a shorter flame development period and rapid combustion period, which means better combustion characteristics can be gained by employing three-stage injection strategy. Compared with the single injection strategy, both two-stage injection strategy and three-stage injection strategy can improve the indicated thermal efficiency, which increases by 0.4% and 5.9% respectively.

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Curve Car Following Model Based on Optimal Velocity and Its Stability Analysis

CHEN Xiufeng, GAO Yanyan, SHI Yingjie, QU Dayi, SONG Zhuhe

2020, 39(01): 126-130. DOI: 10.3969/j.issn.1674-0696.2020.01.21

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In order to study the following characteristics and stability conditions of vehicles on road curves, on the basis of the classical OV model, the OV model of curve was established by considering the influence of road friction, curve radius and super high factors and combining the mechanical characteristics of curve. Based on the following perturbation principle of the vehicle in the curve section, the linear stability of the model was analyzed by using the convergence of Fourier series, and the disturbance stability conditions of the curve following model were obtained. Then, according to the influence factors of sensitivity coefficient, the curve of traffic flow stability region in different curve radians was drawn. In order to verify the validity of the curve following model, computer simulation and road test experiments were carried out to verify the proposed model. The results show that under the same initial density, the stability of the traffic flow in the curve decreases with the increase of curve radian.

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