汽车碰撞安全与轻量化研发中的若干挑战性课题

汽车结构与动力电池的碰撞安全性是开发轻量化、电动化汽车的强制性要求和关键基础性支撑技术。通过3个方面的10个典型课题及研究结果，介绍并综述了汽车碰撞安全性研发的技术挑战。第一，采用夹层式汽车前舱罩盖技术，提升罩盖结构力学特性的横向均匀性以及冲击响应历程的均匀性，满足汽车吸能位移限定下的行人头部碰撞响应控制；采用精细人体有限元模型解析复杂工况下行人下肢损伤机理和影响参数，基于人体组织损伤层面的虚拟评估改进汽车结构的人体碰撞保护设计；面向复杂道路交通事故工况和多样化人体特征，解决强非线性条件下的自适应乘员智能保护系统优化设计难题，通过在时间和空间上对乘员约束载荷的均衡化实现针对工况可调的碰撞保护。第二，揭示材料冲击测试中系统共振导致信号振荡和材料屈服放大振荡的机理，开发抑制信号振荡的轻质动态力传感器；精细表征材料在碰撞载荷和复杂应力状态下的力学行为，针对高强钢、塑料、胶粘和焊点等轻质高强材料及复合连接接头建立大变形失效断裂预报方法及仿真模型。第三，基于动力电池多工况挤压试验，建立电池在外载荷作用下的材料失效、电压陡降与温度上升的响应特征关联性，提出用力学响应特征预测电池内部损伤起始和短路发生的判据，解决电池在机械滥用载荷下的短路预测问题，建立能准确预测电池变形响应的数值模型及碰撞安全评估方法，并应用于电池包和电动车的轻量化与碰撞安全性设计。     

汽车预碰撞制动下乘员离位影响及参数优化分析

对于汽车制动后发生的碰撞工况，乘员前倾将会增加人体损伤风险。本文进行了汽车预碰撞制动下乘员离位影响及参数优化分析研究。通过实车制动试验得到车辆在不同制动工况下的乘员颈部前向位移量分布区间；建立了MADYMO主动人体仿真模型，采用变量分析法研究不同制动波形下乘员离位特征；运用正交设计方法进行滑台碰撞试验，得到乘员离位因子对乘员碰撞损伤影响；建立乘员响应面模型，采用中心复合试验设计（Central composite design）方法，研究了主动式安全带参数与乘员离位位移之间的相关性，通过优化设计，得到了最优参数组合。     

基于动量定理的汽车碰撞事故再现模型抗扰性分析

基于摄动理论，应用3种常用的数学方法对基于动量定理建立的汽车碰撞事故模型的抗扰性进行分析。结果表明：对于特定模型在复杂的扰动条件下，采用不同的数学方法，处理效果截然不同。通过理论分析，建立了解决此类问题的方法，给出了数学表达式。经过对代表车型的实际分析，验证了该方法的有效性。     

前轮转角和车轮制动状态对汽车轨迹模拟的影响

对于碰撞后失去动力的汽车，建立其运动轨迹的计算机模型需要碰撞后汽车的初始速度和前轮转角，制动情况等初始值作为轨迹模型的输入参数，以便观察碰撞发生后的汽车运动情况。分析了碰撞后汽车车轮的受力情况，给出不同初始值情况下的轨迹模拟模型。分析结果得出，车轮在自由状态下，前轮的转角对汽车的运动距离有较大影响；当前轮转角为零时，汽车的质心运动几乎为一条直线；当车轮未完全抱死且前轮转角不为零时，汽车的质心运动为一条曲线。     

基于最小二乘法的事故再现分析

从提高计算机模拟汽车碰撞事故的实用性出发，以物理学和力学为基础，结合恢复系数、摩擦系数等建立车辆碰撞的力学模型，以已知的碰撞参数离差最小为目标，提出采用穷举法，通过计算机编程来实现基于最小二乘法模型的目标函数求解，进行汽车碰撞事故再现分析，通过对一实际交通事故案例的分析，验证了所采用的方法对事故再现的实用性。     

基于LS-DYNA的汽车正碰分析

文中利用NX三维建模软件构建了某汽车的三维几何模型,然后利用ANSA网格软件对三维模型进行网格划分处理,并用LS-DYNA对汽车正面碰撞安全性能进行分析,通过对某汽车正面碰撞仿真计算,分析了汽车正面主要结构在碰撞中的结构耐撞性,并就仿真结果与真实实验数据进行对比,以研究仿真结果的准确性。     

汽车车身碰撞建模影响因素的研究

汽车碰撞分析的有限元建立十分复杂，在对汽车车身典型的构件的碰撞进行了系统研究的基础上，从实用角度分析了用有限元方法解决汽车碰撞模拟时各种因素对计算结果的影响，提出了有关建模的要求和建议，对建立大型碰撞分析模型有指导价值。     

道路交通事故重现计算机模拟研究

建立汽车运动学模型和碰撞模型，采用运动学模型及碰撞模型相结合的研究方法，研究事故重现，并利用计算机进行模拟。通过与实车碰撞试验数据对比验证了该方法的有效性，可为研究和裁定交通事故提供科学的手段。     

轻型汽车前部偏置碰撞特性研究

从汽车前部偏置碰撞动量分析入手提出碰撞前后汽车运动状态间的关系，得出结论：汽车碰撞时９５％以上的能量均由汽车车体变形所吸收；碰撞后汽车的运动状态（即汽车运动的速度及角速度）与汽车碰撞位置有关，与汽车碰撞前的速度成正比。该结论通过ＡＮＳＹＳ／ＬＳ－ＤＹＮＡ３Ｄ有限元模拟计算获得验证。     

基于中国保险汽车安全指数 C-IASI的商业车险纯保费研究

车险作为我国第一财险险种，费率厘定不够精准一直是行业发展的痛点。在国外发达保险市场上，汽车碰撞安全等级及其修复性一直是重要费率厘定因子，并设有相关机构进行汽车碰撞测试。为了弥补我国在这方面的空白，中保研汽车技术研究院和中国汽车工程研究院在中国保险协会的指导下跨界合作开展低速碰撞测试，模拟事故常见的正碰和追尾，从耐撞性、维修经济性、维修比、维修费用、气囊是否直接起爆等 5个维度进行汽车耐撞性及经济维修性测评，构建中国保险汽车安全指数C-IASI。通过引入C-IASI的9项指标，并建立泊松-伽马模型和Tweedie模型，探究汽车自身耐撞性和维修经济性导致的不同赔付差异与机动车辆保费的适配性。实证结果表明，加入中国保险汽车安全指数C-IASI后，商业车险纯保费预测效果有明显提升，泊松-伽马模型和Tweedie模型预测效果接近。     

基于扩展卡尔曼滤波的汽车质心侧偏角估计

基于二自由度汽车动力学模型和轮胎模型,运用扩展卡尔曼滤波方法建立了汽车质心侧偏角估计器.利用汽车动力学仿真平台,通过仿真对比了线性轮胎模型和非线性轮胎模型的质心侧偏角估计结果.仿真结果表明,轮胎模型对于质心侧偏角估计精度至关重要,而采用非线性轮胎模型能显著提高质心侧偏角估计精度,估计结果能满足ESC控制的要求.     

车内低频振动噪声的虚拟传递路径分析

传递路径分析法是诊断汽车振动噪声问题准确有效的方法。试验传递路径分析耗时耗力且需要实制样车,为在整车开发初期诊断汽车振动噪声问题,对整车虚拟传递路径分析法进行了研究。首先建立了包含底盘的整车声固耦合有限元模型,采用频率响应法预测车内声学振动响应,发现驾驶员右耳声压在38 Hz处以及驾驶员座椅导轨振动在59 Hz处存在较大峰值。在有限元模型基础上建立了整车虚拟传递路径分析模型,该模型合成的声学振动结果与频率响应法结果吻合较好,验证了模型的正确性。利用虚拟传递路径法对两处峰值作诊断分析,根据分析结果对贡献量大的路径进行优化。优化结果表明,38 Hz处驾驶员右耳声压降低2 dB,59 Hz处座椅振动改善效果明显。     

基于融合特征稀疏编码模型的车辆品牌识别方法

提出了一种基于融合特征稀疏编码模型的车辆品牌识别方法,该方法首先提取车脸图像的方向梯度直方图特征作为融合特征稀疏编码模型的一级特征向量,然后将车脸图像的一级特征向量作为过完备字典中训练样本集的线性组合,并构建非负性约束稀疏编码模型,最后采用重构误差最小原则对车辆品牌进行识别。基于东南大学的车脸数据库进行了试验,结果表明,基于融合特征稀疏编码模型的车辆品牌识别方法优于HOG+SVM、传统稀疏表示和字典学习稀疏表示的车辆品牌识别方法,其平均识别率达到96.16%。理论分析和试验结果表明,基于融合特征稀疏编码模型的车辆品牌识别方法具有较强的鲁棒性和适用性。     

Design and evaluation of sideslip angle observer for vehicle stability control

This paper presents a method for estimating the vehicle side slip angle, which is considered as a significant signal in determining the vehicle stability region in vehicle stability control systems. The proposed method combines the model-based method and kinematics-based method. Side forces of the front and rear axles are provided as a weighted sum of directly calculated values from a lateral acceleration sensor and a yaw rate sensor and from a tire model according to the nonlinear factor, which is defined to identify the degree of nonlinearity of the vehicle state. Then, the side forces are fed to the extended Kalman filter, which is designed based on the single-track vehicle model associated with a tire model. The cornering stiffness identifier is introduced to compensate for tire force nonlinearities. A fuzzy-logic procedure is implemented to determine the nonlinear factor from the input variables: yaw rate deviation from the reference value and lateral acceleration. The proposed observer is compared with a model-based method and kinematics-based method. An 8 DOF vehicle model and Dugoff tire model are employed to simulate the vehicle state in MATLAB/SIMULINK. The simulation results shows that the proposed method is more accurate than the model-based method and kinematics-based method when the vehicle is subjected to severe maneuvers under different road conditions.     

基于带切换增益模糊调节的滑模控制算法的车辆电液制动系统

针对汽车线控电液制动系统建立了单轮车辆模型,研制了一种新的状态观测器对车速进行估算,试验结果表明该方法正确实用.采用切换增益模糊调节的滑模控制算法对非线性时变的车辆实施基于最佳滑移率的制动控制,在Matlab/Simulink中的仿真结果和验证试验都表明在汽车线控制动系统应用该算法是可行、有效的,在该算法的控制下汽车可获得比一般滑模控制更好的制动性能.     

极限工况下主动前轮转向汽车稳定性控制

轮胎对汽车稳定性有重要影响,研究和利用轮胎的非线性特性有助于扩展汽车的稳定域。本文基于非线性轮胎模型,提出一种改进型线性时变模型预测控制(LTV-MPC)方法。该方法能扩展主动前轮转向汽车的稳定范围,提高极限工况下主动前轮转向汽车的稳定性。仿真结果表明,该方法比传统的LTV-MPC方法具有更好的稳定性控制效果。     

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.     

Damper Models for Heavy Vehicle Ride Dynamics

A laboratory rig for testing hydraulic dampers using the 'hardware-in-the-loop' method is described, and the accuracy of the test method is investigated. A mathematical model of a hydraulic shock absorber is then developed. The model is suitable for vehicle simulations and has seven parameters which can be determined by simple dynamic measurements on a test damper. The shock absorber model is validated under realistic operating conditions using the test rig, and the relative importance of various features of the model on the accuracy of vehicle simulations is investigated.     

Vehicle dynamics and road curvature estimation for lane departure warning system using robust fuzzy observers: experimental validation

This paper describes a new approach to estimate vehicle dynamics and the road curvature in order to detect vehicle lane departures. This method has been evaluated through an experimental set-up using a real test vehicle equipped with the RT2500 inertial measurement unit. Based on a robust unknown input fuzzy observer, the road curvature is estimated and compared to the vehicle trajectory curvature. The difference between the two curvatures is used by the proposed lane departure detection algorithm as the first driving risk indicator. To reduce false alarms and take into account driver corrections, a second driving risk indicator based on the steering dynamics is considered. The vehicle nonlinear model is deduced from the vehicle lateral dynamics and road geometry and then represented by an uncertain Takagi–Sugeno fuzzy model. Taking into account the unmeasured variables, an unknown input fuzzy observer is proposed. Synthesis conditions of the proposed fuzzy observer are formulated in terms of linear matrix inequalities using the Lyapunov method.     

Velocity and normal tyre force estimation for heavy trucks based on vehicle dynamic simulation considering the road slope angle

A precise estimation of vehicle velocities can be valuable for improving the performance of the vehicle dynamics control (VDC) system and this estimation relies heavily upon the accuracy of longitudinal and lateral tyre force calculation governed by the prediction of normal tyre forces. This paper presents a computational method based on the unscented Kalman filter (UKF) method to estimate both longitudinal and lateral velocities and develops a novel quasi-stationary method to predict normal tyre forces of heavy trucks on a sloping road. The vehicle dynamic model is constructed with a planar dynamic model combined with the Pacejka tyre model. The novel quasi-stationary method for predicting normal tyre forces is able to characterise the typical chassis configuration of the heavy trucks. The validation is conducted through comparing the predicted results with those simulated by the TruckSim and it has a good agreement between these results without compromising the convergence speed and stability.