Table of Content

25 November 2022, Volume 44 Issue 11 Previous Issue    Next Issue

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Car Following Model for Intelligent Vehicles Based on Dynamic Balance of Perception Risk Qiaobin Liu,Lu Yang,Bolin Gao,Jianqiang Wang,Keqiang Li 2022, 44 (11):  1627-1635.  doi: 10.19562/j.chinasae.qcgc.2022.11.001 Abstract ( 342 )   HTML ( 36 )   PDF (2437KB) ( 318 )   Save Aiming at the decision-making difficulties of the trade-off between the vehicle following risk and the driving efficiency caused by heterogeneous vehicle types in the complex traffic environment， a human-like vehicle following model for intelligent vehicles based on dynamic balance of perception risk is proposed on the basis of analyzing natural driving data. Firstly， an empirical model of the vehicle following distance is established for vehicle following modes with four different truck-car combination， and the “two invariances” law of time headway （THW） and inverse time to collision （i-TTC） existing in the driver’s steady-state vehicle following behavior is discovered， with the balance lines obtained by drawing method. Then， the mechanism of vehicle following decision-making is revealed from the perspective of the dynamic balance between perception risk and acceleration response during driving， and the commonly-used vehicle following models are unified within the framework of dynamic balance of perception risk. Finally， a simple nonlinear function is proposed as a mathematical expression of dynamic balance of perception risk， and the accuracy of the model is verified by using the tested vehicle following data. Figures and Tables | References | Related Articles | Metrics

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Risk Assessment of Safety of the Intended Functionality Scenes Based on Driving Safety Field Theory Hao Chen,Hong Wang,Weihan Li,Xianxu Bai,Jiong Chen,Chuzhao Li,Qin Shi,Jun Sun 2022, 44 (11):  1636-1646.  doi: 10.19562/j.chinasae.qcgc.2022.11.002 Abstract ( 375 )   HTML ( 24 )   PDF (3891KB) ( 333 )   Save Facing different test calibration requirements and emphases of the safety of the intended functionality （SOTIF） scene for autonomous vehicles （AVs）， a risk assessment method of SOTIF scene based on driving safety field （DSF） theory is proposed in this paper. Firstly， DSF is utilized to conduct risk quantification on each layer of scene elements， and hence to achieve integrated risk calculation. The definition， architecture of SOTIF scene， and the parameters of DSF model are analyzed to prove that DSF model meets the risk assessment requirements of SOTIF scene. Then， the method proposed is applied to divide the vehicle operation scenes into three types： known safe， known unsafe and unknown safe/unsafe. For realizing scene division， different driving states in DSF theory are matched with the operational scenes of vehicles in SOTIF. Finally， closed field tests and road tests are carried out. On one hand， the relative driving safety indicator （RDSI） is compared with time-to-collision （TTC） to verify that RDSI can more accurately and sensitively assess the driving risk. On the other hand， it is proved that the method proposed can effectively fulfill scene division. Figures and Tables | References | Related Articles | Metrics

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Automatic Extraction Method for Autonomous Vehicle Test Scene Primitives Bing Zhu,Yuhang Sun,Jian Zhao,Peixing Zhang,Tianxin Fan,Dongjian Song 2022, 44 (11):  1647-1655.  doi: 10.19562/j.chinasae.qcgc.2022.11.003 Abstract ( 238 )   HTML ( 15 )   PDF (1686KB) ( 275 )   Save In this paper， an automatic test scene primitive extraction method from the naturalistic driving dataset for autonomous vehicles is proposed. With the hidden Markov model （HMM） as framework， the extraction method uses the vector autoregressive model as the observation probability distribution function， and adopt the Hierarchical Dirichlet Process to fulfill prior distribution and posterior updating for HMM. Then the disentangled and sticky process are used to suppress the frequent switching of the HMM hidden states for achieving the solution of hidden states with given observation data， and the scene primitives are automatically divided according to the hidden states. Finally， a piece of naturalistic driving series is randomly selected to verify the method. The results show that the method proposed can automatically extract explicable test scene primitives with clear physical meanings from the naturalistic driving dataset without setting parameters， laying a good foundation for scene-based autonomous vehicle testing. Figures and Tables | References | Related Articles | Metrics

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Semantic Segmentation Method of Point Cloud in Automatic Driving Scene Based on Self-attention Mechanism Dafang Wang,Hai Shang,Jiang Cao,Tao Wang,Xiangteng Xia,Yulin Han 2022, 44 (11):  1656-1664.  doi: 10.19562/j.chinasae.qcgc.2022.11.004 Abstract ( 234 )   HTML ( 13 )   PDF (3148KB) ( 169 )   Save Semantic segmentation of vehicle lidar scene point cloud is the basic work of automatic driving environment perception. In view of the insufficient ability to extract local features and difficulty to capture the global context information of the existing processing method of point cloud in large-scale automatic driving scene， the local and global self-attention encoders are designed based on the self-attention mechanism and the feature aggregation module is built for feature extraction. The experimental results show that compared with RandLA-Net， also adopting local feature aggregation， the method proposed can increase the MIoU by 5.7 percentage points on SemanticKITTI dataset， and adding local self-attention encoder also raises the segmentation accuracy of small targets such as vehicles and pedestrians by more than 2 percentage points. Figures and Tables | References | Related Articles | Metrics

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Path Tracking Strategy for All-Wheel Steering of Multi-axle Heavy-Duty Vehicles Based on Tube MPC Weichen Wang,Junqiu Li,Fengchun Sun,Jian Song,Yonghua Wu 2022, 44 (11):  1665-1675.  doi: 10.19562/j.chinasae.qcgc.2022.11.005 Abstract ( 320 )   HTML ( 13 )   PDF (5308KB) ( 210 )   Save An all-wheel steering path tracking strategy based on model predictive control with robust invariant set is proposed for a five-axle heavy-duty vehicle in this paper. Firstly， an all-wheel steering path tracking strategy based on first-axle and fifth-axle steering angle control is put forward to make the multi-axle vehicle more flexible in control， with the lateral force response synchronized and fully utilized. Then with considerations of the uncertainty of tire parameters and the bounded disturbance caused by side-wind in the control model， the Tube MPC is used to solve the path tracking problem. Meanwhile， a simplified minimum robust positively invariant set （mRPI） based on support function calculation is adopted to replace the general Minkowski sum-based mRPI operation， effectively saving the offline computation time of mRPI， reducing the number of vertices in the invariant set， and ensuring the online implementation of Tube MPC. Finally， a hardware-in-the-loop simulation is carried out with a result verifying that the Tube MPC-based all-wheel steering strategy proposed has higher path tracking accuracy and vehicle stability and stronger robustness when facing unknown disturbance， compared with ordinary all-wheel steering strategy. Figures and Tables | References | Related Articles | Metrics

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Robust Control for Shared Steering Control System Based on Authority Level Dynamic Allocation Xueyun Li,Yiping Wang,Chuqi Su,Xinle Gong,Hung Jin,Xun Liu,Xiaohong Yuan,Huiqian Li 2022, 44 (11):  1676-1688.  doi: 10.19562/j.chinasae.qcgc.2022.11.006 Abstract ( 181 )   HTML ( 17 )   PDF (2547KB) ( 173 )   Save When the sum of the driving rights of the driver and autonomous driving system is fixed to 1， the vehicle steering demand may not match the output of the shared steering control （SSC） system in complex scenarios， which will affect the driving safety of the vehicles. To solve the problem， an authority dynamic allocation approach is proposed， and a robust controller is designed considering the uncertainty of the authority levels and model parameters. Firstly， based on the parallel SSC system framework， an SSC system expansion framework including the driver model， trajectory tracking controller， authority dynamic allocation model， and vehicle model is proposed. The driving state evaluation model， vehicle trajectory tracking state evaluation model， and authority level allocating and decision-making model are proposed. The results of driver’s driving state evaluation and vehicle trajectory tracking state evaluation results are used as the basis for decision-making， combined with the calculation result of the authority allocation model， the authority level of the driver and controller can be determined dynamically. Then， the robust feedback controller is proposed considering the uncertainty of the authority level and vehicle model parameters. Finally， the effectiveness of the proposed SSC system is verified by simulation. The simulation results show that the proposed SSC system can effectively reduce the influence of interference and driver’s misoperation on vehicle safety， and can reduce the driver’s driving load， psychology load and controller workload during steering. Figures and Tables | References | Related Articles | Metrics

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Research on Thermal Runaway Mechanism and Safety Risk Control Method of Power Battery in New-Energy Vehicles Zirun Jia,Zhenpo Wang,Qiushi Wang,Xiaohui Li,Fengchun Sun 2022, 44 (11):  1689-1705.  doi: 10.19562/j.chinasae.qcgc.2022.11.007 Abstract ( 242 )   HTML ( 17 )   PDF (6076KB) ( 375 )   Save Aiming at the thermal runaway and safety risk of the power batteries for new energy vehicles， the research status quo and latest progress of power battery safety issues are summarized in this paper by analyzing the existing power battery safety control methods， proceeding from the induction and reaction mechanism of thermal runaway. The main problems existed in current power battery safety control research are analyzed， and the development trend of the safety risk control technology of new-energy vehicles is pointed out， so as to promote the enhancement of the warning and control technology of power battery safety risk， to ensure the life and property safety of drivers and passengers， and to eliminate the safety anxiety of consumers， promoting the development of new-energy vehicle industry. Figures and Tables | References | Related Articles | Metrics

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Current Situation and Prospect of Traction Battery Safety Standards for Electric Vehicles in China Qiang Shu,Yifan Wang,Yuan Liang 2022, 44 (11):  1706-1715.  doi: 10.19562/j.chinasae.qcgc.2022.11.008 Abstract ( 232 )   HTML ( 27 )   PDF (685KB) ( 268 )   Save In order to ensure the operation safety of electric vehicles， relevant standards of intrinsic safety， active protection safety and passive protection safety of traction battery have been formulated in China， forming a standard system. In this paper， through analyzing the history， faced challenges and improvement suggestions of the existing safety standards， combined with the research and application of traction battery safety technology and national guidance policies， etc， it is shown that the monitoring and early warning of traction battery operating state based on big data is an effective way to prevent thermal runaway， with the suggestions for further completing and perfecting standard system and management mechanism put forward. Figures and Tables | References | Related Articles | Metrics

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Influence of Structural Parameters of Pre-combustion Chamber on the Development Characteristics of Gasoline Hot Jet Fangxi Xie,Jingang Wang,Huili Dou,Jiaxing Li,Bin Wang,Wei Hong 2022, 44 (11):  1716-1724.  doi: 10.19562/j.chinasae.qcgc.2022.11.009 Abstract ( 118 )   HTML ( 11 )   PDF (5182KB) ( 116 )   Save In order to promote efficient application of the pre-combustion chamber ignition system and strengthen understanding of the hot jet itself， the influence of the key structural parameters on the formation of the mixture and the development characteristics of the hot jet in the pre-combustion chamber is studied through the Converge software simulation. The research results show that with the increase of surface-to-volume ratio and cross-section ratio， the penetration distance and distribution area of the jet flame both show a trend of increasing first and then decreasing. When the surface-to-volume ratio of the pre-combustion chamber is 0.02-0.036 cm-1， a relatively large penetration distance and distribution area can be obtained； at the same time， a smaller surface-to-volume ratio is more conducive to the development of the heat jet in its axial direction， and the pre-combustion chamber with a larger surface-to-volume ratio has a larger radial diffusion range of the heat jet. The cross-section ratio of 0.15 and 0.20 can obtain relatively larger penetration distance and distribution area. When the cross-section is larger， the quality of the mixture formed in the pre-combustion chamber deteriorates and the combustion pressure decreases； when the cross-section gets smaller， the combustion pressure also decreases. When the upper structure of the pre-combustion chamber adopts the circular truncated cone structure， relatively better combustion pressure as well as penetration distance and distribution area of the jet flame can be obtained， and the jet formation and development performance are poorer when the stepped structure is adopted. Figures and Tables | References | Related Articles | Metrics

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A Superposition-Based Variable-Weight Over-Modulation Method for Drive PMSM Controller in Electric Vehicles Cheng Lin,Xiongwei Jiang,Xingming Zhuang,Huanran Liu,Jilei Xing,Shuai Gao 2022, 44 (11):  1725-1734.  doi: 10.19562/j.chinasae.qcgc.2022.11.010 Abstract ( 145 )   HTML ( 9 )   PDF (8082KB) ( 108 )   Save The over-modulation method used in the drive motor controller of electric vehicle can increase the maximum output power of motor drive system， and enhance the capabilities of torque output and speed regulation in high-speed region. However， the traditional over-modulation method has the problem of voltage mutation in the over-modulation zone II， leading to a large jitter of the output torque of motor drive system and affecting the power and NVH performances of the vehicle. In view of this problem， a superposition-based variable-weight over-modulation method is proposed in this paper. The method eliminates the voltage mutation and hence reduces the total harmonic distortion by introducing the phase angle of the reference voltage into the calculation of the superposed weighting factor. The results of simulation and test show that this method can enhance the current stability in drive motor control， reduce the output torque jitter of the drive motor system， and enable the motor drive system of electric vehicle to output the maximum torque and maximum speed in the high-speed region. Figures and Tables | References | Related Articles | Metrics

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Research on Driving Cycles of Heavy Semi-trailer Tractor and Optimization of Its Powertrain System Guogui You,Jianwei Lu,Junshou Su,Mingyong Luan,Shuai Huang 2022, 44 (11):  1735-1745.  doi: 10.19562/j.chinasae.qcgc.2022.11.011 Abstract ( 195 )   HTML ( 12 )   PDF (5192KB) ( 150 )   Save In this paper， the driving data of heavy semi-trailer tractor in Shanxi region are collected on the spot by utilizing the big data platform of vehicle driving information. Principal component analysis， cluster analysis and Markov method are used to construct the driving cycle of heavy semi-trailer tractor in Shanxi region. The fuel consumptions of C-WTVC， CHTC-TT， and Shanxi driving cycles are simulated respectively， and the simulation results verify the accuracy of the driving cycles constructed. The powertrain system of the vehicle is optimized and matched based on Shanxi driving cycles. As a result， the probability of the vehicle engine working in economy zones increases， and the fuel consumption per 100 km is 0.94 L less than that of the original vehicle. The fuel consumption data of the real vehicle tested confirm that the driving cycle curve can better represent the driving characteristics of heavy semi-trailer tractors in Shanxi region. The simulation method of vehicle powertrain matching based on Shanxi driving cycles proposed is helpful to the design of highly-efficient powertrain system of heavy semi-trailer tractors suitable for Shanxi region. Figures and Tables | References | Related Articles | Metrics

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Lateral Dynamics Modeling and Stability Analysis of Bus with Air Suspension System Long Chen,Ming Chen,Xiaoqiang Sun,Yingfeng Cai,Pak Kin Wong,Ziqiang Wu 2022, 44 (11):  1746-1754.  doi: 10.19562/j.chinasae.qcgc.2022.11.012 Abstract ( 147 )   HTML ( 12 )   PDF (3477KB) ( 181 )   Save A system nonlinear dynamic modeling and stability analysis method is proposed in this paper to revealing the lateral dynamic instability of air suspension bus under special driving conditions. A three degree of freedom dynamic model of the system considering the nonlinear mechanical characteristics of air spring and tire is established. In order to realize the stability analysis of complex high-dimensional dynamic system， the dimension of the system is reduced based on the central manifold theory firstly， and then the qualitative behavior of the reduced system is analyzed to determine the necessary and sufficient conditions for the system to meet the requirements of saddle node bifurcation. The bifurcation behavior of the system under four working conditions at the equilibrium point is analyzed in the phase plane， and the evolution law of lateral dynamic instability of the air suspension bus with the change of vehicle speed and front wheel angel under different road conditions is mastered. Finally， the system stability analysis results are verified based on the vehicle dynamics simulation. The results show that the analytical analysis results are consistent with the simulation analysis results， which proves that the nonlinear stability analysis method proposed in this paper is effective and practical. Figures and Tables | References | Related Articles | Metrics

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Co-simulation of Vehicle Redundant Steering System Based on Virtual Prototype Bo Zhang,Wenzhi Yang,Yong Lu 2022, 44 (11):  1755-1762.  doi: 10.19562/j.chinasae.qcgc.2022.11.013 Abstract ( 115 )   HTML ( 7 )   PDF (3208KB) ( 112 )   Save For the problem of long design cycle and high cost of redundant steering system， a method of virtual prototype system of redundant steering system is proposed by using multi-body dynamics software ADAMS and control simulation software Simulink. The dynamics model of steering system is established based on the analysis of rack and pinion dynamics. The control model of redundant steering system is established based on Simulink， and the co-simulation model is built by Simulink. The virtual prototype system is used to simulate the power assist performance of the redundant steering system. Through simulation and experiment， the designed redundant steering system has good power performance and fault tolerance， and meets the requirements of the steering system. The error of the co-simulation data and the test is within 5%， which proves the method of co-simulation is feasible. Figures and Tables | References | Related Articles | Metrics

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Research on Shift Schedule of DCT Vehicle on Flat-Straight Road Based on Driving Data Mining Datong Qin,Kang Wang,Jihao Feng,Yonggang Liu 2022, 44 (11):  1763-1771.  doi: 10.19562/j.chinasae.qcgc.2022.11.014 Abstract ( 98 )   HTML ( 4 )   PDF (3844KB) ( 90 )   Save In view of the poor adaptability of the shift schedule formulated based on vehicle dynamics， and the inability of gear decision model trained based on multidimensional data and intelligent algorithm in being directly applied to real vehicles， a method is proposed of extracting the shift schedule on flat-straight road by mining the driving data of skilled drivers. Firstly， a test is conducted to collect a large amount of driving data. Then three most important features of flat-straight road driving are extracted by using wavelet de-noising， spearman correlation analysis and information gain calculation. Finally， by comparing the classification accuracy of six machine learning algorithms for decision values （upshift， downshift and maintenance） in each gear， the random forest algorithm with the highest accuracy is selected to generate the three-parameter shift schedule， in which the parameters are vehicle speed， accelerator pedal position and engine angular acceleration. The simulation results show that this method can effectively collect the shift strategy of skilled drivers running on flat-straight road， and the shift schedule extracted achieves a fuel consumption level close to that with the economic shift strategy and a good power performance. Figures and Tables | References | Related Articles | Metrics

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Study on Inflator for CAB Pressure Maintaining Using Heat Transfer Theory Philips Shan,Xuezhe Wei,Victor Jing 2022, 44 (11):  1772-1778.  doi: 10.19562/j.chinasae.qcgc.2022.11.015 Abstract ( 107 )   HTML ( 5 )   PDF (1028KB) ( 89 )   Save After the promulgation of C-NCAP 2021， 6 seconds pressure maintaining requirement poses a challenge to the design and development of curtain airbag （CAB）. This paper aims to conduct a study on inflator， as one of the key components of CAB. Based on heat transfer theory with the knowledge of thermodynamics， the deployment process of CAB is divided into three sub-processes， the effects of inflator on the pressure maintaining process of CAB are expounded， and the role and influence of inflator’s key parameters are summed up in detail. It is concluded by theoretical analysis and case study that the pyrotechnic inflator is not suitable to pressure maintaining CAB， cold-gas inflator is weak in product competitiveness， while the hybrid inflator with competitive price can possibly meet the requirements of CAB in pressure maintaining as long as its temperature is lower than the critical one such as 450 K. Figures and Tables | References | Related Articles | Metrics

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Influence of the Windward Angle of Front Bumper Deflector on the Aerodynamic Drag of a Light Bus Shuangshuang Li,Wei Song,Liang Zou,Junying Min,Jianping Lin 2022, 44 (11):  1779-1785.  doi: 10.19562/j.chinasae.qcgc.2022.11.016 Abstract ( 157 )   HTML ( 6 )   PDF (3190KB) ( 129 )   Save In order to reduce the aerodynamic drag of light bus during driving for energy saving， the influence of the windward angle of the front bumper deflector on the wind resistance of the vehicle is investigated in this paper. Computational fluid dynamics analysis is carried out on both the original vehicle and the vehicles equipped with a deflector with a windward angle of 35°~90°. The results show that adding deflectors with different windward angles on the front bumper has a drag reduction effect， with the minimum drag coefficient achieved at a windward angle of 45 °. A wind tunnel test on the vehicle is also performed and the results indicate that with a test wind speed of 80~120 km/h， the drag coefficient reduces by 0.2%~0.5% and 3.3%~3.9% respectively under the conditions of opened and closed air intake grilles by adding a deflector with a windward angle of 45°. Figures and Tables | References | Related Articles | Metrics

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Influence of Nanosecond Pulsed Laser Cleaning on Laser Welding Quality of AZ31B Magnesium Alloy Mingjun Zhang,Xiong Li,Heqing Li,Chenxi Li,Jian Zhang,Bo Cheng,Kaiming Wang,Cong Mao,Yongle Hu 2022, 44 (11):  1786-1796.  doi: 10.19562/j.chinasae.qcgc.2022.11.017 Abstract ( 93 )   HTML ( 3 )   PDF (11669KB) ( 66 )   Save In order to enhance the laser welding quality of AZ31B magnesium alloy， the surfaces of specimen are cleaned by nanosecond pulsed laser before welding. The surface morphologies and chemical compositions with different ways of cleaning are analyzed by scanning electron microscope and energy spectrometer. The dynamic processes of laser welding are observed via high-speed photography to analyze the effects of the different ways of cleaning and parameters on the surface cleaning effect and welding quality. The results show that the oxide film on magnesium alloy surface can be effectively removed by nanosecond pulsed laser cleaning， with the surface of specimen exhibiting fine microstructure features. Compared with the untreated or steel-brushed processes， laser cleaning process has a positive effect on the stabilities of the keyhole and molten pool during laser welding of magnesium alloy： the scale-like ripples on weld surface are uniform and fine， the microstructure of the joint is evenly distributed along the direction of plate thickness， with few defects of pores and cracks. Furthermore， the pre-weld laser cleaning can significantly increase the elongation rate of the laser weld joint of magnesium alloy. Compared with the untreated or steel-brushed processes， its joint elongation increases by 50.3% and 16.4% respectively. Appropriate laser cleaning can effectively remove the oxide film on the magnesium alloy surface， improve the surface microstructure， and obtain a higher tensile strength and elongation rate of the weld joints. Figures and Tables | References | Related Articles | Metrics