Study concerning the effect of wheel center trajectory angle on harshness vibration

Harshness vibration can be reduced by modifying the side-view inclination angle of the wheel center trajectory, but the dynamic mechanism involved is not clearly understood. The mechanism is explained here by formulating it with equations of motion and verifying it by comparing the numerical simulation results with experimental data. It is shown that the force generated by tire rotational slip should be considered. An analytical study was made of the relationship between suspension specifications and the optimal inclination angle of the wheel center trajectory for minimizing harshness vibration.     

Vehicle Energy Dissipation Due to Road Roughness

SUMMARY

Road roughness and surface texture are known to affect tire rolling resistance; however, little emphasis has been placed on the consequent changes in total vehicle energy dissipation due to road roughness. Thus, tire rolling resistance, in isolation from vehicle contributed losses such as dissipation in the suspension, appears to be a weakness in present evaluation procedures as they relate to fuel economy and pollution level testing: Recent work by Funfsinn and Korst has shown that substantial and measurable increases in energy losses occur for vehicles traveling on rough roads. The present investigation uses vehicle axle accelerations as a means of examining various road surfaces. Correlation with computer simulations has allowed the development of a deterministic road roughness model which permits the prediction of energy dissipation in both the tire and suspension as functions of road roughness, tire pressure, and vehicle speed. Comparison to the experiments of Korst and Funfsinn results in good agreement and shows that total rolling loss increases of up to 20 percent compared to ideal smooth roads are possible. The aerodynamic drag coefficient is also found to increase while driving on rough roads.     

基于车路系统的事故现场轮胎印迹强度参数化研究

为明确事故现场可视轮胎印迹强度与车辆动力学特性、轮胎橡胶磨损特征及道路表面灰度之间的关联特性,提出基于车路耦合的事故现场轮胎印迹强度参数化研究方法。通过结合动态滑动摩擦因数模型及轮胎非线性模型,建立车辆路面9 DOF非线性系统动力学模型,运用VBOX惯性测量技术验证模型的有效性。运用胎面磨损能量模型,从车路系统角度确定车辆、轮胎和路面特性对轮胎全局摩擦力及胎面磨损特性的影响。结合印迹强度特征模型提出轮胎印迹强度参数研究方法,选取不同制动、转向角工况及3组路面、胎面特性对轮胎路面接地力学特性、胎面橡胶磨损量、可视轮胎印迹特征进行仿真分析。结果表明：印迹强度仅与全局摩擦力大小有关,与轮胎路面滑移方向无关;滑移工况下胎面橡胶磨损量随着全局摩擦力和滑移速度的增大而增大,而印迹强度变化不明显;制动力矩和道路表面灰度对产生可视轮胎印迹起决定作用,转向角主要影响不规则可视轮胎印迹的产生;前轮轮胎最先出现可视印迹,且可视印迹长度和强度均高于后轮轮胎;采取可视印迹起点作为事故车辆速度判定具有一定的误差,应根据具体情况进行具体分析;研究成果能够为基于可视轮胎印迹的交通事故重建提供理论基础。     

Vehicle Energy Dissipation Due to Road Roughness

Road roughness and surface texture are known to affect tire rolling resistance; however, little emphasis has been placed on the consequent changes in total vehicle energy dissipation due to road roughness. Thus, tire rolling resistance, in isolation from vehicle contributed losses such as dissipation in the suspension, appears to be a weakness in present evaluation procedures as they relate to fuel economy and pollution level testing: Recent work by Funfsinn and Korst has shown that substantial and measurable increases in energy losses occur for vehicles traveling on rough roads. The present investigation uses vehicle axle accelerations as a means of examining various road surfaces. Correlation with computer simulations has allowed the development of a deterministic road roughness model which permits the prediction of energy dissipation in both the tire and suspension as functions of road roughness, tire pressure, and vehicle speed. Comparison to the experiments of Korst and Funfsinn results in good agreement and shows that total rolling loss increases of up to 20 percent compared to ideal smooth roads are possible. The aerodynamic drag coefficient is also found to increase while driving on rough roads.     

轮胎空腔共振噪声与力传递率关系的试验研究

为研究轮胎空腔共振噪声特性及其评价方法,通过在轮胎内部充入空气与氦气,在内衬层粘贴不吸音泡沫和不同的吸音材料,对轮胎的力传递率特性与轮胎跌落噪声、室内转鼓噪声和实车道路噪声等空腔共振特性之间的关联关系进行试验研究.结果表明:轮胎内充入氦气与添加多孔吸音材料对轮胎力传递特性和轮胎空腔共振噪声有明显的影响,轮胎跌落噪声和室...     

An Optimal Continuous Time Control Strategy for Active Suspensions with Preview

A continuous time control strategy for an active suspension with preview, based on optimal control theory, is presented. No approximation is needed to model the time delay between the excitation of the front and the rear wheels. The suspension is applied to a two DOF model of the rear side of the tractor of a tractor-semitrailer. The purpose of the suspension is to reduce either the required suspension working space or the maximum absolute acceleration of the sprung mass, without an increase of the dynamic tire force variation. For a step function as road input, reductions of 65% and 55%, respectively, are possible compared with a passive suspension.     

Drive control system design for stability and maneuverability of a 6WD/6WS vehicle

This paper describes a drive controller designed to improve the lateral vehicle stability and maneuverability of a 6-wheel drive / 6-wheel steering (6WD/6WS) vehicle. The drive controller consists of upper and lower level controllers. The upper level controller is based on sliding control theory and determines both front and middle steering angle, additional net yaw moment, and longitudinal net force according to the reference velocity and steering angle of a manual drive, remotely controlled, autonomous controller. The lower level controller takes the desired longitudinal net force, yaw moment, and tire force information as inputs and determines the additional front steering angle and distributed longitudinal tire force on each wheel. This controller is based on optimal distribution control and takes into consideration the friction circle related to the vertical tire force and friction coefficient acting on the road and tire. Distributed longitudinal/lateral tire forces are determined as proportion to the size of the friction circle according to changes in driving conditions. The response of the 6WD/6WS vehicle implemented with this drive controller has been evaluated via computer simulations conducted using the Matlab/Simulink dynamic model. Computer simulations of an open loop under turning conditions and a closed-loop driver model subjected to double lane change have been conducted to demonstrate the improved performance of the proposed drive controller over that of a conventional DYC.     

电控空气悬架系统综述

随着车辆控制技术的发展,电控空气悬架系统逐步取代了传统空气悬架.文章介绍了电控空气悬架系统的结构组成及其功能特点,概述了国内外电控空气悬架的发展情况,简要分析了其发展趋势.与传统弹簧悬架相比,电控空气悬架系统具有较优越的动态传递特性,能降低车轮与路面之间的相对动载,减少汽车对路面的冲击损坏,较好地改善汽车的行驶平顺性和操纵稳定性.     

半主动悬架的SIRMs模糊控制算法研究

文章以车身垂向振动速度、车身垂向振动加速度、悬架动行程和轮胎动位移为输入项目,主动悬架所产生的阻尼力F作为输出量,即设计一个包含4个输入项目和1个输出量的半主动SRIM模糊控制模型,并进行了凸起路面和随机路面下的仿真分析,计算结果显示该控制方法相对于半主动悬架经典控制方法有着更好的控制效果。     

Tire Lateral Force Estimation Using Kalman Filter

As for the tire analysis, lateral tire force is a fundamental factor that describes the stability of vehicle handling. Attempts to analyze the vehicle stability have been made based on various objective test methods and some specific factors such as yaw, lateral acceleration and roll angle. However, the problem to identify which axle is lack of the tire grip at a certain situation still remains. Since indoor tire force measurement system cannot represent a real road and vehicle conditions, tire force measurement through a real vehicle test is inevitable. Due to the high price of the tire force measurement device, tire force estimator can be an alternative toward cost reduction and device failure. In this paper, nonlinear planar full car model combined with tire model is proposed. Then, using discrete-time extended Kalman-Bucy filter (EKBF), individual tire lateral force are estimated with modified relaxation length model.     

Vertical Load-Deflection Behaviour of a Pneumatic Tire Subjected to Slip and Camber Angles

In this paper the vertical load-deflection behaviour of a pneumatic tire has been studied theoretically. A simple mathematical model which is especially suitable for a tire applied by a side force has been developed. Researches carried out in the past show that the tire vertical stiffness varies neither proportionally nor symmetrically as the slip angle of a cambered tire is changed. This effect can be explained by the theory developed here.

The model predictions have been verified using experimental results obtained from literature. Moreover, tire cornering characteristic curves obtained under different test conditions, i. e. during increasing of the slip angle the vertical load is kept constant or not, have been discussed through a simulation example. This study shows that the characteristic curves vary rather considerably under the different conditions.     

Constrained Optimal Control of Semi-Active Suspension Systems with Preview

Controllers for semi-active suspensions have to account for constraints on damper range, tire force and suspension travel. Two approaches to incorporate these constraints in the design of controllers to minimize peak values in the chassis acceleration are considered. It is assumed that information on the oncoming road elevations (preview) is available. In the soft constraint approach, the constraints on tire force and suspension travel are included in a quadratic performance index. Two clipped optimal control laws, which deal with preview in a different way, are presented. Simulation results with a 2-DOF vehicle model on some rounded pulses show that these laws do not work satisfactorily with respect to the constraints. Therefore, the control problem is reformulated as a constrained optimization problem with hard constraints on tire force and suspension travel. Simulations with the same model on the same rounded pulses show that the hard constraint approach handles the constraints more properly.     

路面激励引起车内噪声的模拟和试验

本文建立了因路面不平度随机激励所产生的车内噪声的数学模型，借助了测得的车身悬置连接点的导纳函数，各连接点到车内耳旁位置的噪声传递函数以及悬置和轮胎参数，计算了由路面不平度所引起的车内耳旁噪声的大小，并将其与道路模拟机上的测量结果相比较，结果表明两者获得了较好的一致，还进一步分析了改变悬置和轮胎参数对车内噪声的影响，为车内噪声的分析、悬置参数的择优选取和汽车的声学设计提供了简易方法。     

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.     

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.     

前轮定位角对汽车转向回正作用的影响

利用数学方法，通过将前悬挂系统简化为相关杆系，论述了车轮外倾角、主销内倾角和后倾角以及转向轮转角改变时对汽车转向回正作用的影响，并求出了使汽车具有转向回正作用时，上述有关角度之间的数学关系。     

考虑弹性支撑边界条件的电动汽车-路面系统机电耦合振动特性分析

轮毂电机驱动电动汽车的簧下质量大导致轮胎动载荷增加,并且电机电磁力和转矩波动对车轮造成电机激励,进一步加剧车轮振动引起垂向振动负效应的问题。鉴于此,考虑电机的电磁激励,建立了电动汽车-路面系统的机电耦合动力学模型,推导了弹性支撑边界条件下路面结构的模态频率和振型表达式,以及路面振动引起的二次激励。计算了简支与弹性支撑边界条件下的路面模态频率,根据频率分布进行了截断阶数选取,并分析了边界条件、电机激励和车速对路面响应的影响。在此基础上,研究了不同行驶速度、路基反应模量及路面不平顺幅值下,激励形式对汽车车身加速度、悬架动挠度和轮胎动载荷的影响。结果表明：路面不平顺幅值越小,弹性支撑对路面响应的影响越大,弹性支撑边界条件下的路面响应较小,电机激励会引起路面响应的增加;弹性支撑边界条件下,路面不平顺幅值和路基反应模量越小,考虑路面不平顺、路面二次激励和电机激励的三重综合激励对电动汽车响应的影响越大,激励形式对轮胎动载荷的影响最大,对车身加速度的影响次之,对悬架动挠度的影响最小;电机激励导致轮胎动载荷增加,对路面破坏和寿命产生的负效应不容忽视。所建电动汽车-路面系统机电耦合模型及研究思路可为电动汽车垂向动力学分析提供参考与理论支持。     

Numerical Simulation of Vehicle Behavior during Straight Line Keeping on Undulating Road Surfaces

SUMMARY

Numerical design of vehicles having optimal straight line stability on undulating road surfaces requires an accurate vehicle model based on knowledge of the relevant phenomena. Therefore, vehicle behavior on undulating straight roads has been analyzed and modeled. Measurements on a flat road surface have shown that the dedicated vehicle model yields accurate simulation results of the steering response to medium steering wheel angle inputs. In addition, the model has been validated by measuring two vehicle responses during normal driving on an undulating straight road: viz. the responses to the small steering wheel angle input and to the input by the global inclination of the road surface.     

基于自适应模型预测的智能汽车横向轨迹跟踪控制

当路面附着情况和车辆行驶状态不断变化时,基于恒定侧偏刚度的模型预测控制(MPC)不能考虑轮胎非线性特性的影响,难以保证车辆轨迹跟踪的适应性。为此,提出一种考虑轮胎侧向力计算误差的自适应模型预测控制(AMPC),以提高智能汽车在不确定工况下的轨迹跟踪性能。分析了路面附着系数和垂向载荷对轮胎侧向力的影响,基于平方根容积卡尔曼滤波(SCKF)算法,设计了利用侧向加速度和横摆角速度作为测量变量的前后轮胎侧向力估计器。利用轮胎侧向力线性计算值与估计值的差值计算得到侧偏刚度修正因子,设计了前后轮胎侧偏刚度的自适应修正准则,进而提出了一种基于时变修正刚度的AMPC控制方法。基于CarSim与MATLAB/Simulink联合仿真和硬件在环测试平台,对AMPC控制的有效性和实时性进行了验证。研究结果表明：在不同的路面附着情况和车辆行驶状态下,AMPC控制都能够降低横向位置偏差和航向角偏差,有效提高车辆的轨迹跟踪精度,其控制效果明显优于基于恒定侧偏刚度的标准MPC控制。尤其在低附着工况下,标准MPC控制会因为线性轮胎力的计算误差过大而导致车辆在轨迹跟踪时严重失稳,而AMPC控制通过估计轮胎力修正侧偏刚度依然能够保证车辆稳定有效的跟踪参考轨迹。所提出的AMPC控制在保证控制精度的同时具有良好的实时性,对智能汽车控制系统的设计与优化具有重要参考价值。