Structural Optimization for Roof Crush Test Using an Enforced Displacement Method

A roof crush test has been utilized to reduce passengers’ injuries from a vehicle rollover. The Federal Motor Vehicle Safety Standards (FMVSS) 216 and the Insurance Institute for Highway Safety (IIHS) perform actual vehicle tests and evaluate the vehicle’s ratings. Nonlinear dynamic response structural optimization can be employed not only for achievement of a high rating but also minimization of the weight. However, the technique needs a huge computation time and cost because many nonlinear dynamic response analyses are required in the time domain. A novel method is proposed for nonlinear dynamic response structural optimization regarding the roof crush test. The process of the proposed method repeats the analysis domain and the design domain until the convergence criteria are satisfied. In the analysis domain, the roof crush test is simulated using a high fidelity model of nonlinear dynamic finite element analysis. In the design domain, a low fidelity model of linear static response structural optimization is utilized with enforced displacements that come from the analysis domain. Correction factors are employed to compensate the differences between a nonlinear dynamic analysis response and a linear static analysis response with enforced displacement. A full-scale vehicle problem is optimized with a constraint on the rigid wall force from the analysis in the design domain.     

Roof strength performance improvement enablers

Before 2009, rollover in vehicle accidents had not been significantly studied not only because its rate is lower than other types of accidents but also because it had been easy to meet the rollover regulation, the FMVSS 216 Roof Crush Resistance target. The regulation only requires that the strength-to-weight ratio (SWR) be 1.5, i.e., it was acceptable when the roof could withstand a force of only 1.5 times the vehicle??s weight. In other words, rollover is not considered an important safety factor. However, presently, the situation has completely changed. Rollover is now considered a key safety factor. Recently, the number of rollover incidences has been increasing, reaching as much as the number of front, side and rear accidents. Furthermore, the IIHS has begun to require that the roof must withstand a force of 4.0 times the vehicle??s weight, a more severe restriction than FMVSS. To satisfy this requirement, many manufacturers, universities and institutes are studying the topic. This paper focuses on changing the body structure to minimize injury to the occupant when rollover occurs and help rollover safety performance become excellent. This paper draws on a simple analysis that is based on general factors: changes in the material, the addition of welds and additional reinforcements. The best result will be determined, as described by this paper.     

乘用车顶部抗压强度试验及发展趋势

由于交通事故中侧滚翻事故的死亡率非常高,为达到车辆发生侧翻时对乘员的保护,充分考虑我国国情,2011年1月14日,我国正式发布GB26134--2010《乘用车项部抗压强度》国家强制性标准,明确对车身强度试验的准备和实施过程及要求,文章以标准规定的试验方法为主要内容,详细介绍了试验的准备和实施过程,并结合美国联邦机动车法规FMVSS216a提出了汽车顶部抗压强度法规的发展趋势。     

Heavy duty vehicle rollover detection and active roll control

This paper presents the results of a comprehensive study on heavy-duty vehicle (HDV) roll stability improvement technology. The proposed rollover threat warning system uses the real-time dynamic model-based time-to-rollover (TTR) metric as a basis for online rollover detections. Its feasibility for implementation in a HDV rollover threat detection system is demonstrated through vehicle dynamic simulation studies. The research on the development of a rollover threat detection system is further enhanced in combination with an active roll control system using active suspension mechanism to improve heavy-duty trucks’ roll stability both in the static cornering and in emergency maneuvers. It has been demonstrated that the roll stability of typical heavy-duty trucks has been largely improved by the proposed active safety monitoring and control system.     

Investigation into untripped rollover of light vehicles in the modified fishhook and the sine maneuvers. Part I: Vehicle modelling, roll and yaw instability

Vehicle rollovers may occur under steering-only maneuvers because of roll or yaw instability. In this paper, the modified fishhook and the sine maneuvers are used to investigate a vehicle's rollover resistance capability through simulation. A 9-degrees of freedom (DOF) vehicle model is first developed for the investigation. The vehicle model includes the roll, yaw, pitch, and bounce modes and passive independent suspensions. It is verified with the existing 3-DOF roll-yaw model. A rollover critical factor (RCF) quantifying a vehicle's rollover resistance capability is then constructed based on the static stability factor (SSF) and taking into account the influence of other key dynamic factors.

Simulation results show that the vehicle with certain parameters will rollover during the fishhook maneuver because of roll instability; however, the vehicle with increased suspension stiffness, which does not rollover during the fishhook maneuver, may exceed its rollover resistance limit because of yaw instability during the sine maneuver. Typically, rollover in the sine maneuver happens after several cycles.

It has been found that the proposed RCF well quantifies the rollover resistance capability of a vehicle for the two specified maneuvers. In general, the larger the RCF, the more kinetically stable is a vehicle. A vehicle becomes unstable when its RCF is less than zero. Detailed discussion on the effects of key vehicle system parameters and drive conditions on the RCF in the fishhook and the sine maneuver is presented in Part II of this study.     

概念阶段应用超静定力学规划车顶抗压性能的研究

近几年北美和中国的翻滚事故致死人数和死亡率居高不下,对社会和交通人身安全造成了恶劣影响,而翻滚伤害又与车顶抗压强度有关。应用超静定力学分析法预测各个路径的受力,进而明确关键力学路径,通过梁结构弯矩提高的理论,选取关键力学路径中受压侧的板件厚度作为正交试验的因素,分析各因素对车顶抗压强度和质量的贡献度。研究发现,连接中立柱内板和顶盖中横梁的接头支架对车顶抗压性能的贡献度最大。通过对接头支架进一步的优化设计,在提高车顶抗压性能的情况下,实现轻量化。     

客车车身侧翻刚度仿真研究

建立客车骨架的有限元模型,依照ECE R66法规,使用LS-DYNA软件对其进行侧翻仿真分析.在此基础上,分别改变客车顶盖、侧围和前后围的材料,并再次进行仿真计算.对比仿真结果发现.增强前后围刚度可有效提高整车的侧翻刚度.     

Design of a rollover index-based vehicle stability control scheme

This paper presents a rollover index (RI)-based vehicle stability control (VSC) scheme. A rollover index, which indicates an impending rollover, is developed by a roll dynamics phase plane analysis. A model-based roll estimator is designed to estimate the roll angle and roll rate of the vehicle body with lateral acceleration, yaw rate, steering angle and vehicle velocity measurements. The rollover index is computed using an estimated roll angle, estimated roll rate, measured lateral acceleration and time-to-wheel lift. A differential braking control law is designed using a direct yaw control method. The VSC threshold is determined from the rollover index. The effectiveness of the RI, the performance of the estimator and the control scheme are investigated via simulations using a validated vehicle simulator. It is shown that the proposed RI can be a good measure of the danger of rollover and the proposed RI-based VSC scheme can reduce the risk of a rollover.     

Measurement of roof deformation caused by vehicle rollover

A vehicle rollover is a critical accident that could have many causes. This paper describes a novel vision-based system for measuring vehicle roof deformation due to a rollover accident. A vision-based measurement system offers an overall view of structural deformation simply at low cost. Our measurement system was constructed using a Kinect camera from Microsoft, a battery, and a remote-controlled recording computer. Color images and distance maps can be obtained using two sensors embedded in the Kinect along with customized software, and the distance from the camera lens to a specific object can be calculated with a simple equation. To test our proposed approach, actual vehicle rollover experiments were conducted and the resulting roof deformations were compared to those indicated by our system. Moreover, cross-sectional image of Apillar was analyzed to calculate bending moment of inertia. From the research results, it was able to show that deformation errors were within 13 mm, and roof deformation was correlated with vehicle type, or vehicle curb weight.     

某中型校车顶部强度分析与结构改进

依照相关标准和法规,对某型校车车身顶部强度进行静态压溃、准静态压溃和整车跌落的仿真研究,系统评价校车车顶结构的抗压强度特性,并对关键承载结构进行改进。     

Analysis of bus rollover protection under legislated standards using LS-DYNA software simulation techniques

A bus rollover is one of the worst vehicle accidents that can occur. Because of the large numbers of passengers, the casualties in a bus rollover are often high and severe. The compliance with rollover safety standards for buses and coaches is mandated by law. This paper presents a comparative analysis of the physical meanings of regulation number 66 of the Economic Commission for Europe (ECE R66) and standard number 220 of the American Federal Motor Vehicle Safety Standards (FMVSS 220). This comparison was carried out using a LS-DYNA finite-element analysis. After performing a comparative analysis following ECE R66 and FMVSS 220 assessments, the investigation further demonstrated the distortion configuration of the vehicle superstructure through the absorbed energy and its distribution over the vehicle and in sections of vehicle superstructure as well as the violation of the passenger compartment under the rollover testing conditions of both ECE R66 and FMVSS 220. Great differences were found between ECE R66 and FMVSS 220 in distortion configuration, reflecting differences in capability and rollover testing conditions. These findings provide a means of evaluating bus superstructure strength and provide guidelines useful in the assessment of regulations applied to the evaluation of bus rollover strength.     

半挂汽车列车高速公路弯道下坡路段运行安全研究（双语出版）

为提升半挂汽车列车在高速公路弯道下坡路段的运行安全，采用TruckSim仿真软件，构建了车辆模型、道路模型和驾驶人动力学仿真模型；基于蒙特卡罗可靠性分析法，分别建立了半挂汽车列车发生侧滑失效、侧翻失效、折叠失效和系统失效的功能函数，并选取设计速度80 km·h^-1的高速公路为研究路段，通过进行大量车辆动力学仿真试验，对不同圆曲线半径、纵坡坡度、路面附着系数、车速和车辆总质量对半挂汽车列车的运行安全的影响进行了数值分析。研究结果表明：半挂汽车列车发生侧滑和侧翻的概率随着圆曲线半径的增加而显著降低，在一般最小半径400 m的情况下，半挂汽车列车发生侧滑失效和侧翻失效的概率趋近于0；随着下坡坡度的增加，半挂汽车列车发生侧滑失效和侧翻失效的概率基本呈线性增长趋势；车速对于半挂汽车列车运行安全的影响尤为显著，当车速均值由60 km·h^-1增加到90 km·h^-1时，发生侧滑失效和侧翻失效的概率分别增加了634倍和336倍；车辆总质量的增加对半挂汽车列车侧翻有显著影响；在路面附着系数较低的条件下，半挂汽车列车的主要事故形态为侧滑和折叠，在路面附着系数较高的情况下，半挂汽车列车的主要事故形态为侧翻。因此，在道路设计中，应避免极限最小半径与陡坡组合，严格限速和限载可确保半挂汽车列车的运行安全性能。     

多用途乘用车侧翻稳定性能动态测试方法研究

对比分析了国内外车辆侧翻稳定性相关的标准法规的基本情况。研究了车辆发生侧翻的类型和机理,基于侧向加速度判断车辆侧翻状态的方法,通过整车道路试验对比了正弦停滞试验和鱼钩试验诱导车辆发生侧翻的效果,初步探讨了多用途乘用车侧翻稳定性动态测试方法和评价指标,为国内车辆侧翻稳定系统的开发和测评标准的制定提供了参考。     

Contour line of load transfer ratio for vehicle rollover prediction

For vehicle rollover control systems, an accurate and predictive rollover index is necessary for a precise rollover threat detection and rollover prevention. In this paper, the contour line of load transfer ratio (CL-LTR) and the CL-LTR-based vehicle rollover index (CLRI) are proposed, describing LTR threshold and LTR change rate precisely, providing an accurate prediction of vehicle rollover threat. In detail, the CL-LTR is proposed via the roll dynamics phase plane analysis, and its analytical solution of one-degree-of-freedom vehicle roll model and extension for full vehicle are derived. Moreover, the predictive CLRI is proposed and evaluated via vehicle dynamics study. The results demonstrate that vehicle rollover threat is predicted accurately based on the CLRI, which shows benefits for the vehicle rollover prediction and stability control.     

基于车辆动态控制的防侧翻方法分析研究

本文基于49CFR Part 575法规对车辆防侧翻评价指标进行初步探索,并利用CarSim软件建立具有高质心特性的SUV车辆模型,对车身、制动系统、转向系统、轮胎及悬架等子模块进行了定义,完成非线性动力学模型的建立,结合汽车动态控制系统,建立车辆防侧翻控制策略,同时,利用CarSim与Matlab/Simulink进行联合仿真,模拟SUV在极限工况Fishhook环境下的工作情况,验证防侧翻的作用效果,结果表明:防侧翻策略有效的减小了侧向加速度,使得车辆的抗侧翻能力有所增强,汽车的安全性与稳定性得到了有效的保证,为实车试验提供科学依据。     

Effectiveness of ECE R66 and FMVSS 220 standards in rollover crashworthiness assessment of paratransit buses

The main objective of the presented study was to compare the effectiveness of two standard test procedures for evaluating bus roof integrity: the dynamic rollover test according to UN-ECE Regulation 66 (ECE-R66), and the quasi-static symmetric roof loading according the Federal Motor Vehicle Safety Standard 220 (FMVSS 220). Both tests were applied to a selected Paratransit Bus. The investigation was carried out primarily using a numerical study backed up by experimental validation tests on components and full scale rollover tests. A sensitivity analysis using LS-OPT? was performed to identify the most important structural components influencing the response of the bus in these two tests. The results obtained from this study show that the final outcome of the crashworthiness assessment of the selected paratransit bus depends on the selection of the evaluation standard. Although the two tests are used for the same purpose of roof integrity evaluation, their results are divergent and may lead to different conclusions. The paper presents a discussion on the effectiveness of both standards in evaluating the rollover crashworthiness.     

矿用货车自动驾驶条件下侧翻安全分析与极限参数研究

为防止自动驾驶条件下矿用货车发生侧翻,对依靠规划控制层实现侧翻事故的主动预防方法进行研究.针对该问题先建立矿用货车侧倾数学模型,推导静态稳定因子(Static Stability Factor,SSF)与车辆侧倾稳定极限(Roll Stability Limit,RSL)公式.利用TruckSim仿真软件完成水平路面1...     

Vehicle dynamic estimation with road bank angle consideration for rollover detection: theoretical and experimental studies

This article describes a method of vehicle dynamics estimation for impending rollover detection. This method is evaluated via a professional vehicle dynamics software and then through experimental results using a real test vehicle equipped with an inertial measurement unit. The vehicle dynamic states are estimated in the presence of the road bank angle (as a disturbance in the vehicle model) using a robust observer. The estimated roll angle and roll rate are used to compute the rollover index which is based on the prediction of the lateral load transfer. In order to anticipate the rollover detection, a new method is proposed in order to compute the time-to-rollover using the load transfer ratio. The used nonlinear model is deduced from the vehicle lateral dynamics and is represented by a Takagi–Sugeno (TS) fuzzy model. This representation is used in order to take into account the nonlinearities of lateral cornering forces. The proposed TS observer is designed with unmeasurable premise variables in order to consider the non-availability of the slip angles measurement. Simulation results show that the proposed observer and rollover detection method exhibit good efficiency.     

顶盖挤压的试验法规及有限元分析

在翻滚事故中,车辆的主要承载件是车顶及其支承结构。只有这些结构有足够的刚度才能保证翻滚事故中乘员必要的生存空间。我国将颁布顶盖挤压标准,对车顸刚度及检测方法提出要求。本文通过有限元分析法进行预测,物理实验结果表明,该方法是可行的。     

基于侧碰耐撞性的B柱轻量化设计

研究了薄壁梁三点弯曲工况压溃力与材料强度和板厚的关系,并提出了一种B柱轻量化设计方法。对于B柱下端,侧撞时发生压溃折弯,可近似等效为三点弯曲工况,且用高延性高强钢代替普通的强度较低的高强钢,进行B柱下端的轻量化设计。至于B柱上端,因其侧撞时主要发生刚性转动,可等效为静力学问题,施加侧撞等效静载力,将B柱上端划分成N段,利用Optstruct软件对各段板厚进行优化。最后以某车型为例,将B柱上、下端优化方案导入整车侧撞模型中进行优化。结果表明优化后B柱关键部位的侵入速度和侵入量与原始设计几乎相当,证明该轻量化设计是有效的,优化实现了24%(1.9 kg)的轻量化效果,而其耐撞性不受影响。