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  • 2017, Vol. 08 No. 01 Published on:23 March 2017 Previous issue    Next issue
    Progress & Prospects
    State-of-the-art and technical trends of intelligent and connected vehicles
    LI Keqiang, DAI Yifan, LI Shengbo, BIAN Mingyuan
    2017, 08(01):  1-14.  doi:10.3969/j.issn.1674-8484.2017.01.001
    Abstract ( 1555 )   PDF (2806KB) ( 6108 )  

    The state-of-the-art and technical trends of intelligent and connected vehicle (ICV) are illustrated.
    The ICV system architecture included the value chain, technology chain and industrial chain. The four stages of
    ICVs were the advanced assistance, connected assistance, cooperative automation and highly/fully automated
    driving. Some key technologies of ICVs were introduced such as environmental perception, decision making,
    dynamical control, human-machine copilot, V2X communication and platform, cyber security. Therefore, China
    should develop the ICV industry rely on the top-down design by using the national institutional advantages
    because the ICV will be an important direction of the automotive technology in the future, and the ICV
    development is a great opportunity for the transformation and upgrading of China's automobile industry.

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    Review for mechanical integrity of lithium-ion battery
    2017, 08(01):  15-29.  doi:10.3969/j.issn.1674-8484.2017.01.002
    Abstract ( 338 )   PDF (1505KB) ( 2301 )  

    This paper reviews the current status of the mechanical integrity study on electric vehicle lithium-ion batteries, points out shortcomings and unsolved problems, and pinpoints important future research frontiers. Due to the inevitable traffic crash accidents, lithium-ion battery would experience internal short-circuit, temperature rise, pressure increase thus leading to thermal runaway, and finally causing catastrophic consequences such as fire and explosion, subject to mechanical abuse conditions including vibration and shock, large deformation and nail penetration. The possible safety issue may restrain the further spreading and wider pplication of electric vehicles. Researchers have a comprehensive study for lithium-ion battery through experiment, theory and simulation considering multi-physics field from different scale, such as material, cell, modulus and system.

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    Automotive Safety
    Modified particle swarm optimization algorithm using in lightweight design of auto-body
    LIU Zhao, ZHU Ping,LI Zeyang
    2017, 08(01):  30-37.  doi:10.3969/j.issn.1674-8484.2017.01.003
    Abstract ( 239 )   PDF (1561KB) ( 1074 )  

    A modified Particle Swarm Optimization (PSO) algorithm was built based on stagnation judging criterion and particle velocity updating equation to improve the diversity of particles during optimization procedure. A new velocity updating equations was activated to improve the diversity between particles while the particles optimization procedure fell into stagnation. The modified PSO algorithm was compared with the standard version of PSO based on a set of benchmark functions by mathematical experiments. Auto body lightweight optimization design was made by using the modified PSO incorporated with metamodeling technique and reasonable constrained handling method, considering 100% frontal impact, 40% frontal offset impact, side impact, rear impact and roof crash conditions, and under the premise of satisfying each structural performance index. The results show that the optimization solutions by modified PSO algorithm are superior to those by standard PSO with areduced mass of 23.41 kg. This will provide a referential method for light mass design of auto-body.

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    Dynamic identification method of driver and vehicle features based on travel time
    WANG Xiaoyuan, LIU Yaqi, ZHANG Jinglei
    2017, 08(01):  38-45.  doi:10.3969/j.issn.1674-8484.2017.01.004
    Abstract ( 195 )  

    It is of great significance for the people-centered safe driving assistant system to realize the dynamic identification of driver’s propensity and vehicle type. Considering the privacy protection, a dynamic identification model for driver and vehicle characteristics was established using Bayesian decision tree. The ravel time obtained by global position system (GPS) data when cars went through an intersection was used to identify the vehicle type and driver’s propensity in the model. The identification effectiveness of human-vehicle characteristics under different permeability conditions was verified by real and virtual driving experiments. The results show that the accuracy rate of the established recognition model was above 80% and the established model was significantly better than the traditional decision tree model. The good consistency between the microscopic simulation considering driving tendency and the actual situation was verified by simulation experiment, and the rationality of the research results was proved indirectly.

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    Hygrothermal degradation and recoverability of mechanical properties of epoxy adhesive joints for automotives
    YAO Li, XIA Yong,ZHOU Qing
    2017, 08(01):  46-52.  doi:10.3969/j.issn.1674-8484.2017.01.005
    Abstract ( 195 )   PDF (1300KB) ( 819 )  

    Automobile lightweight requires the adoption of adhesion technology. However, the hot-humid service environment poses a threat to the mechanical properties of structural adhesives. This experimental study uncovered the effect of hygrothermal degradation (HTD) and drying on an epoxy adhesive and its joint. The tests for uniaxial tensile, notched tensile, double cantilever beam peel and cross tensile peel were conducted to explore the performance of adhesive bulk and joint of varied HTD histories. The result shows that 1) HTD reduced bulk adhesive properties, such as elastic modulus, peak stress, failure strain and energy absorption; 2) Upon drying, elastic modulus and peak stress almost fully recovered; failure strain further decreased; energy absorption hardly restored; 3) HTD reduced the interfacial strength between adhesive and aluminum substrate leading to interfacial failure; 4) Upon drying, the interfacial strength significantly recovered. Therefore, it is suggested to design a bonded vehicle body per the worst case of hygrothermal degradation.

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    Influence of small overlap frontal oblique impact conditions on crashworthiness of car body
    NIU Weizhong, XU Pengshan, LIU Jinxin
    2017, 08(01):  53-58.  doi:10.3969/j.issn.1674-8484.2017.01.006
    Abstract ( 225 )   PDF (1988KB) ( 869 )  

    A finite element model of two colliding sports utility vehicle (SUV) cars of same type was developed to evaluate the crashworthiness of passenger car in small overlap frontal oblique impact accident by using HyperWorks and LS-DYNA software. Through simulating several impact conditions of 25% overlap, the influences of collision angle and velocity on the crashworthiness of two car bodies were analyzed in terms of three important evaluation indexes i.e. maximum acceleration at the bottom of B-pillar, maximum bending angle on the upper part of A-pillar and dash panel intrusion. The results show as follows: In a 0° ~ 45° small overlap
    frontal oblique impact, this type of car had its worst crashworthiness when it was collided as an inserted highspeed car by an inserting high-speed car at 0° ~ 15°; and with the increase of relative collision velocity of two cars, its crashworthiness deteriorated sharply. So the condition can be chosen for the pointed optimizing design to the car body.

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    Optimization on stepping automotive wake structures based on orthogonal test method
    QU Xian, YU Feng
    2017, 08(01):  59-64.  doi:10.3969/j.issn.1674-8484.2017.01.007
    Abstract ( 174 )   PDF (1300KB) ( 873 )  

    An orthogonal test for wake structures was conducted with computational fluid dynamics (CFD) technique to optimize the stepping automotive wake flow field. The method of controlling variable was applied to analyze six main rear structures, and the factor level was preferred. The L25 (56) orthogonal optimization test of
    the tail structure method was designed. And the degree of influence from different rear structures was analyzed by use of the range analysis method. The wake flow field of the optimum tail model was obtained. The results show that the wake structure comprehensive optimization decreases the coefficient of the aerodynamic drag by 14.4%. The wake flow structure is improved as the rear airflow was separated and vortexes were suppressed effectively. These results provide an important basis for the optimal design of automotive wake shape.

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    Multi-phase impact pulse and structure design for pedestrian headform impact on vehicle hood
    NIE Bingbing, ZHOU Qing, XIA Yong
    2017, 08(01):  65-71.  doi:10.3969/j.issn.1674-8484.2017.01.008
    Abstract ( 199 )   PDF (1681KB) ( 1048 )  

    The impact response of pedestrian headform was analyzed to understand the influence of vehicle hood design in assessment tests of pedestrian protection performance. The impact pulse (acceleration-time history) of the pedestrian headform generally composed of multiple peaks. Each phase was dominated by
    location specific factors, including active mass, structural stiffness, boundary constraints and deformation space under vehicle hood. Vehicle hood design shall take into account of these dominating factors under given design constraints to minimize value of the head injury criterion. As an application example, the study presented a sandwich hood structure design on a production vehicle model. The results show that the sandwich hood structure can prove capable of improving the headform protection performance compared to conventional hood.

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    Experimental study on charicteristics of overdischarged Li-NCM batteries
    ZHOU Ping, SUN Lin, ZHENG Yuejiu, OUYANG Minggao, ZHOU Long
    2017, 08(01):  72-78.  doi:10.3969/j.issn.1674-8484.2017.01.009
    Abstract ( 219 )   PDF (1606KB) ( 1912 )  

    Overdischarge of the Li-NiCoMnO2 (NCM) batteries causes internal short circuit. The overdischarged battery has the ability of self-healing during the storage process. The overdischarged NCM batteries were investigated to further clarify the characteristic of overdischarged battery. The overdischarged NCM batteries
    were firstly rested for 100-day and followed by 20 cycles and 3-day rest. The results indicate that the capacity of overdischarged battery cells degraded during the storage. No matter to what extent the NCM batteries was overdischarged, the internal short circuit level decreased while the ISC resistance rose, and the leakage current droped after the 100-day rest of the overdischarged batteries. The cycle life test after storage proved that the higher degree of the overdischarge, the faster a battery capacity faded. The performance of the battery after overdischarge is helpful to understand the characteristics of the battery, and it is also helpful to the verification of the algorithm for the identification of the short circuit resistance

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    Automotive Energy Efficiency & Environment Protection
    Performances of DC-DC converter for fuel cell vehicle based on SiC and Si device
    2017, 08(01):  79-86.  doi:10.3969/j.issn.1674-8484.2017.01.010
    Abstract ( 340 )   PDF (2093KB) ( 1356 )  

    The performances in circuit loss of an interleaved dual Boost high power derect-curent to derectcurent (DC-DC) converters were analyzed by using Si devices or/and SiC devices in a fuel cell vehicle to regulate and control the output voltage and output power. The circuit losses and efficiency in the whole SiC devices (i.e. SiC Metal-Oxide-Semiconductor Field-Effect Transistor, MSOFET and SiC diode) converter, hybrid devices (i.e. SiC MOSFET and Si diode) converter and the whole Si devices (i.e. Si Insulated Gate Bipolar Transistor, IGBT and Si diode) converter were compared base on circuit loss numerical calculation and efficiency simulation. The results show that the Si IGBT losses are 3 times for switching on and 10 times for switching off as that of SiC MOSFET and the efficiencies of All-SiC devices are 1%~3.1% higher than All-Si devices in different conditions. Therefore, the SiC devices can improve the power density, reliability and efficiency of the power system for high power DC-DC converters.

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    Optimal charge depleting control of plug-in hybrid electric vehicles based on driving condition
    YANG Lin, HU Yanqing, YAN Bin
    2017, 08(01):  87-96.  doi:10.3969/j.issn.1674-8484.2017.01.011
    Abstract ( 239 )   PDF (2778KB) ( 1147 )  

    The optimized battery power consumption law (also means the optimized control trajectory of the stage of charge (SOC) ) of plug-in hybrid electric vehicles (PHEVs) was obtained using a four-mode plug-in hybrid bus based on driving conditions. The main driving condition parameters that have the most influence on optimal SOC control trajectory were given by dynamic programming (DP) and correlation analysis method, and an optimized SOC trajectory planning method was proposed. The results of comprehensive driving cycles tests show that, compared with existing mileage-based linear programming method, the established SOC trajectory
    planning method significantly reduced the SOC trajectory deviation from DP-based optimal results. The mean deviation was reduced by 75.2% to less than 3.6%, and the maximum deviation decreased by 72.3% to less than 8.2%. Computing time was reduced from 7.6~8.5 h to less than 0.18 s compared with DP. An adaptive
    equivalent consumption minimization strategy (A-ECMS) that trace the planned SOC trajectory can improve the fuel economy, only 2.7% worse than DP, which can effectively solve the key problem of the on-line optimal planning of SOC trajectory and the energy optimal control, and provide a novel way for PHEV on-line energy
    management optimization.

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    Safe fast charging algorithm of lithium ion battery based on an electrochemical model
    SUN Zhanyu
    2017, 08(01):  97-101.  doi:10.3969/j.issn.1674-8484.2017.01.012
    Abstract ( 325 )   PDF (1231KB) ( 2478 )  

    Although traditional fast charging methods can increase charging time of lithium ion battery, they are usually detrimental to battery life and causes safety problem. A control-oriented electrochemical model of lithium ion battery was used to develop a novel model-based fast charging algorithm to solve the problem of accelerated degradation or safety issues during the fast charging. The algorithm was validated by charging a commercial Li(NiMnCo)O2 (NMC) cathode battery of 42 Ah. The effect of the key parameters of the strategy on the algorithm performance, such as threshlod potential and initial charging rate, were also discussed. The results show that safe fast charging was achieved and charging rate was enhanced by 20.5%. As the critical parameters in the algorithm, threshold potential and initial charging rate influenced the charging time and anode overpotential during charging

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    Energy-saving technology application for conventional energy passenger cars in China
    ZOU Yuhong, REN Huanhuan, YU Rujie
    2017, 08(01):  102-108.  doi:10.3969/j.issn.1674-8484.2017.01.013
    Abstract ( 219 )   PDF (1468KB) ( 1008 )  

    It is of instructive significance for the development of our country vehicle industry to investigate the application ratio trend of vehicle energy conservation technology. Based on statistics from the U.S. Environment Protection Agency, the International Council on Clean Transportation and China Automotive Technology and Research Center, a technology penetration three-stage model (initial stage, quickly develop stage and saturation stage) was proposed. The application of variable valve timing (VVT) technology in America, turbocharging technology, gasoline direct injection (GDI) technology and advanced transmission in China was analyzed
    considering the effect of related regulation, original equipment manufactures (OEMs), etc. The result shows that under the double inspiration of fuel economy standard improving and oil price increasing, the growth rate of VVT penetration rose while multi-valve technology remained same in America. EU-Sino, US-Sino and Japan-Sino cars accelerated the adoption of turbocharging technology, GDI technology and advanced transmission in China.

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