New Model of Tire Overturning Moment Characteristics and Analysis of Their Influence on Vehicle Rollover Behavior

A newly developed tire model for the Overturning Moment (OTM) characteristics and the analysis of the influence of OTM on vehicle rollover behavior are presented. The new OTM model was developed based on the so-called Magic Formula tire model. The concept of the new model involves identifying the difference between the simple model and the measurements to the newly defined functions. It was seen that the new model agrees very well with the measured data over a wide range of tire vertical loads, slip angles and camber angles. The influence of tire OTM on the vehicle rollover behavior was also investigated by using a full vehicle simulation in which a rather large steering angle was input. The results obtained from the vehicle simulation with three different tire models (model without OTM, simple model and new model) were compared with the experimental results. It was found that the calculated result obtained with the new OTM model agreed best with the experiment.     

Two-Dimensional Contact Area of a Pneumatic Tire Subjected to a Lateral Force

A mathematical model of a two-dimensional contact patch of pneumatic tires rolling over a rigid flat road surface at arbitrary slip and camber angles has been developed. The model is simple in concept, contains few parameters and is applicable to any tire simulation models. In addition to tire geometric parameters and vertical deflection, the carcass camber angle is introduced in the model. This angle is alone responsible for the asymmetric shape of the tire contact patch when the tire undergoes a lateral force. The computed contact patches agree well with the measured patches of an automotive tire at different slip and camber angles. Lastly, the influence of the contact patch geometry on the tire cornering and aligning properties has been discussed through a computational example. It has been shown that the effect of tire contact patch geometry on the steady state behavior is rather remarkable.     

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.     

Tire wear estimation based on nonlinear lateral dynamic of multi-axle steering vehicle

This paper presents a novel nonlinear dynamic model of a multi-axle steering vehicle to estimate the lateral wear amount of tires. Firstly, a 3DOF nonlinear vehicle dynamic model is developed, including dynamic models of the hydropneumatic suspension, tire, steering system and toe angle. The tire lateral wear model is then built and integrated into the developed vehicle model. Based on the comparison of experimental and simulation results, the nonlinear model is proved to be better than a linear model for the tire wear calculation. In addition, the effects of different initial toe angles on tire wear are analyzed. As simulation results shown, the impact of the dynamic toe angle on the tire wear is significant. The tire wear amount will be much larger than that caused by normal wear if the initial toe angle increases to 1° - 1.5°. The results also suggest that the proposed nonlinear model is of great importance in the design and optimazation of vehicle parameters in order to reduce the tire wear.     

A Versatile Flat Track Tire Testing Machine

Summary A flat track tire testing machine developed by the IMMa group is described. It permits the simulation and study of the dynamic behavior of a great variety of tires under controllable and repetitive highly dynamic realistic working conditions in the laboratory for a diversity of vehicles, from motorcycles to light trucks. The machine incorporates: – a hydraulically operated tire support and loading system with wide operating ranges; – a computer controlled brake system to simulate braking maneuvers with ABS systems; – a complete sensorial system; – a data acquisition and control system continually monitoring and acting on the experimental variables, i.e., tire and belt speed, longitudinal slip, slip and camber angles, tire pressure, tire normal force, etc. As an application example, results are presented that adjust the parameter of the magic formula for a standard 175/70 R14 passenger vehicle tire. Accurate mathematical tire models are recognized as essential for the prediction of vehicle dynamic performances using simulation tools.     

A Versatile Flat Track Tire Testing Machine

Summary A flat track tire testing machine developed by the IMMa group is described. It permits the simulation and study of the dynamic behavior of a great variety of tires under controllable and repetitive highly dynamic realistic working conditions in the laboratory for a diversity of vehicles, from motorcycles to light trucks. The machine incorporates: - a hydraulically operated tire support and loading system with wide operating ranges; - a computer controlled brake system to simulate braking maneuvers with ABS systems; - a complete sensorial system; - a data acquisition and control system continually monitoring and acting on the experimental variables, i.e., tire and belt speed, longitudinal slip, slip and camber angles, tire pressure, tire normal force, etc. As an application example, results are presented that adjust the parameter of the magic formula for a standard 175/70 R14 passenger vehicle tire. Accurate mathematical tire models are recognized as essential for the prediction of vehicle dynamic performances using simulation tools.     

实测道路载荷谱在新开发车型车身疲劳分析中的应用

根据新研发车和现有车型具有相同底盘平台的特点,提出一种利用现车道路载荷,快速进行新车车身疲劳分析和评估的方法。建立新车多体模型,放大现车道路载荷并结合轮胎接地位移为输入。根据车轮力传感器(WFT)载荷测量特点,正确地对模型加载激励,仿真得到车身载荷谱。选用合理疲劳分析方法预测车身寿命,以现车车身的疲劳分析损伤为目标,对不合格局部进行合理优化,最终新车车身达到设计耐久目标。     

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.     

用于公路车-桥系统振动分析的精细化轮胎模型

为了解决当前公路车桥耦合振动模型中轮胎模型过于简化、车轮-路面接触力与桥梁响应计算结果不够精确的问题,提出了一种精细化轮胎模型.首先基于车辆橡胶轮胎的几何、力学特征,建立了径向弹簧力学模型并进行了理论推导;然后考虑轮胎与路面接触面的刚度分布特征和高速状况下轮胎的惯性力,提出了轮胎接触面分布刚度的计算方法,保证了轮胎接触...     

基于制动与悬架系统的车辆主动侧翻控制的研究

为提高车辆抗侧翻能力,建立了10自由度整车侧翻动力学模型,应用车辆动力学和轮胎力耦合特性,提出了一种基于差动制动和半主动悬架协同工作的车辆主动抗侧翻控制策略。通过对制动力矩的差动调节和半主动悬架阻尼力的适时匹配,实现对车辆侧翻的有效控制。根据子系统运动特性,设计了制动系统基于滑移率的积分滑模控制器和悬架系统灰模糊控制器。分别对制动、悬架控制及综合控制进行的鱼钩试验仿真结果表明,综合控制策略可有效降低危险时域车辆的侧倾角,相对于单一系统控制进一步提高了车辆抗侧翻能力。     

路面抗滑性能影响弯道行车安全的仿真分析

为研究车辆制动工况下路面抗滑性能对弯道行车安全的影响,以车辆动力学分析软件AD-AMS为仿真平台,提出采用轮胎解析参数、整车参数、路面抗滑值构建耦合关联的车辆-轮胎-路面模型,在此基础上研究不同湿滑路面状态下弯道行驶车辆的运动学参数值变化情况,探索路面抗滑性能与表征行车安全风险的运动学参数值之间的关系.研究结果表明,路面抗滑性能影响车辆运动学参数值变化是诱发交通事故的主要因素.较低的弯道路面抗滑性能易使车辆在制动时出现急速横摆、甚至侧翻的交通事故;车辆两侧轮胎接地面抗滑值不均衡对弯道行车安全的影响高于对直道行车安全的影响,车辆极易在弯道制动时出现因抗滑值不均衡而无法保持有效转弯半径、进而冲出车道的交通事故.研究可为制定弯道行车安全的保障措施提供理论依据.      

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.     

汽车轮胎滚动阻力试验机测试方法分析

为了对汽车轮胎滚动阻力测试方案的可行性进行预先评估,基于检测设备的结构模型,提出了一种运用位移量对轮胎滚动阻力进行仿真分析的新方法。在简述滚动阻力有限元测试模型构建过程的基础上,通过改变轮胎的外部使用参数,分析传感器板在不同工况下位移场的分布情况,制定了设备的测试方案。以传感器的安装位置作为目标检测点,建立轮胎滚动阻力位移场与控制参数之间的关系曲线。最后将采集的数据经过平均滤波处理,与实验室的实测数据进行了趋势性对比。结果表明：采用该测试方法,轮胎滚动阻力随着轮胎负载和速度的增加而增大,随着气压的变大而减小;仿真结果和试验数据在相同工况下的变化趋势基本一致;该测试方法合理、可行。     

Modeling to Predict Rollover Threat of Tractor-Semitrailers

Summary A predictive model to determine a rollover threat index associated with tractor-semitrailers is proposed. The purpose of this model is to predict the rollover threat sufficiently in advance of the actual event so as to enable the driver to react accordingly. The predictive model is established using simple roll-plane models of the vehicle sprung and unsprung masses in conjunction with online vehicle parameter identification. Using this predictive model, the predicted Load Transfer Ratio (LTR) for the trailer axle can be determined as the rollover threat index. The proposed predictive model and the associated parameter-identification algorithm are verified using a 12-degree-of-freedom vehicle model. It is shown that the identified parameter values are close to the actual ones used in detailed simulation study. Similarly it is shown that the predicted values of the LTR are close to the simulated ones, and hence the proposed approach is potentially suitable as the basis for application in rollover threat assessment.     

Analysis of Tire Effect on the Simulation of Vehicle Straight Line Motion

In the dynamic simulation of vehicle straight line motion, a vehicle model usually drifts from its intended straight path even in the case of no external input. This is particularly true when a tire model based on experimental data is used. The purpose of this paper is to provide an enhancement of a basic understanding of a tire/vehicle system behavior in the straight line motion and to identify the effect of the tire on that motion. Through the analysis of a two degrees of freedom vehicle model, tire characteristic which causes a lateral drift in the straight line motion is identified. Then the results are confirmed from vehicle test and the simulations with a more complex full-car model.     

Analysis of Tire Effect on the Simulation of Vehicle Straight Line Motion

In the dynamic simulation of vehicle straight line motion, a vehicle model usually drifts from its intended straight path even in the case of no external input. This is particularly true when a tire model based on experimental data is used. The purpose of this paper is to provide an enhancement of a basic understanding of a tire/vehicle system behavior in the straight line motion and to identify the effect of the tire on that motion. Through the analysis of a two degrees of freedom vehicle model, tire characteristic which causes a lateral drift in the straight line motion is identified. Then the results are confirmed from vehicle test and the simulations with a more complex full-car model.     

Roll Dynamics of Commercial Vehicles

An analytical model is developed here for studying the roll dynamics of commercial vehicles. Large displacements and rotations are accounted for in this nonlinear model so that it can be used for the study of roll dynamics well beyond the limits of wheel lift-off. The model is used to illustrate some of the dynamic phenomena in vehicle rollover, especially the interactive coupling between the roll and the vertical modes of motion. The influence of suspension backlash on rollover resistance is demonstrated, and the phenomenon of roll motion resonance is illustrated to suggest new means for evaluating vehicle rollover sensitivity.     

轴重和胎压对车轮动荷载的影响

为研究重型运输车辆对路面作用的动荷载,建立车辆动力学模型,模型中将簧上质量处理为空载簧上质量与装载质量,将轮胎刚度表示为轴重和胎压的函数。研究了轴重和胎压对车辆动荷载的影响。结果发现,车轮动荷载随着轴重和胎压的增加而增加;动载系数随着胎压的增加而增加,但随着轴重的增加而减小;胎压越高,车轮动载随轴重增加速度越快;仅仅采用轴重不足以评价重载高压车辆对路面的破坏作用,在治理超载的同时也应进一步治理超压：空载车辆对路面的冲击作用较大,不能忽视空载车辆对路面的破坏作用;实际高速运行车辆对路面施加较大的附加动荷载,现有《公路沥青路面设计规范》没有考虑附加动荷载是引起路面结构发生早期破坏的原因之一。     

Design of rollover prevention controller with linear matrix inequality-based trajectory sensitivity minimisation

This paper presents a method to design a rollover prevention controller for vehicle systems. The vehicle rollover can be prevented by a controller that minimises the lateral acceleration and the roll angle. Rollover prevention capability can be enhanced if the controlled vehicle system is robust to the variation of the height of the centre of gravity and the speed of the vehicle. For this purpose, a robust controller is designed with linear matrix inequality-based trajectory sensitivity minimisation. Differential braking and active suspension are adopted as actuators that generate yaw and roll moments, respectively. The newly proposed method is shown to be effective in preventing rollover by the simulation on a non-linear multibody dynamic simulation software, CarSim^®.     

汽车侧翻和滚翻事故建模研究

分析汽车在侧翻和滚翻过程中的受力状态和轮胎或车身与路面的相互作用方式,建立汽车侧翻和滚翻的运动学和动力学模型,揭示汽车临界侧翻碰撞力与持续作用时间等参数的关系,推导侧翻车辆侧向速度的范围,确定滚筒模型中关键参数的选取方法。事故案例表明模型在实际应用中效果良好、定量准确、直观性强。