轮胎制动与驱动特性的理论模型

轮胎印迹内垂直载荷的分布与形式的选择，对建立轮胎制动与驱动特性的理论模型有很大影响。根据轮胎制动和驱动时印迹内垂直载荷分布特性，以及轮胎的前后变形特性，建立了轮胎制动、驱动特性的理论模型。应用该理论模型的计算结果，与试验结果具有很好的一致性。     

用于汽车制动、驱动与转向运动模拟的轮胎力学统一模型

提出了一种包括任意垂直载荷分布的轮胎在纵滑与侧偏联合工况下的力与力矩的统一模型。该模型可归结为无量纲合力与无量纲综合滑移率的关系,因此简化了试验结果的归纳与整理,并可从较易行的单纯侧偏试验结果中推断出侧偏与纵滑联合工况下的无量纲力学特性,从而为汽车在转向、制动、驱动及其联合工况下动力学的模拟研究奠定基础。文中同时给出了一些轮胎台架试验结果和汽车转弯制动试验结果,并与按模型计算的结果作了比较。     

Magic Formula轮胎模型动力学性能研究

进一步研究Magic Formula轮胎模型的动力学性能。在Adams软件中建立Magic Formula轮胎模型,并进行纯制动、纯转向和制动转向联合三种工况下的仿真。仿真得到纵向力与纵向滑移率、侧向力与侧偏角、侧向力与纵向力和回正力矩与滑移率等关系曲线,并进行分析。结果表明,Adams软件完成了Magic Formula轮胎模型多种工况下的仿真工作,Magic Formula轮胎模型可以较好地模拟轮胎动力学特性。     

载重子午胎与沥青混凝土桥面全耦合瞬态接触响应的数值模拟

为了研究轮胎与路面接触响应的关系,帮助桥面沥青铺装系结构设计,利用ABAQUS有限元软件分别对传统11R22.5及新型425/65R22.5宽基胎与混凝土桥沥青铺装层在制动、自由滚动、驱动、侧偏、侧压等工况下的全耦合瞬态接触响应进行了数值模拟,结果发现:当轮胎制动或驱动加速时,接触区横向中部变形均滞后于胎缘两侧,而侧滑时纵向中部变形却滞后于前后边缘;同时,侧压工况下竖向应力、横向切应力则呈振荡曲线分布,随着远离侧压端呈振荡式衰减。     

基于模糊差动制动的运动型多功能汽车防侧翻控制

为了提高SUV高速紧急操纵下防侧翻性能,提出了基于模糊差动制动控制的防侧翻控制策略.研究中考虑轮胎非线性因素的影响,建立了4自由度非线性汽车侧翻模型,并通过横向载荷转移率负反馈设计了参数自整定的模糊PID控制器,以驱动电控机械制动系统(EMB)产生抗横摆力矩防止汽车侧翻.典型工况下的算例分析结果表明,该控制策略能充分发挥EMB响应快的特性,防止SUV高速紧急操纵下侧翻.     

整车不足转向特性影响因素研究

文章分析了悬架KC特性、轮胎力学特性对车辆不足转向特性的影响,其中悬架侧倾转向、侧向力转向、回正力矩转向及轮胎侧偏刚度对整车不足转向特性有重要贡献,而轮胎垂向载荷及复合工况下纵向滑移率则对轮胎侧偏刚度有明显影响,进而改变整车不足转向特性,为底盘开发提供了重要的理论依据。     

利用试验模态参数建立轮胎非稳态侧偏模型

在对轮胎垂直特性和稳态侧偏特性建模的基础上，利用由轮胎模态试验提取的试验模态参数建立了轮胎非稳态侧偏模型，该模型考虑了印迹的动态变形和胎宽的影响，对印迹进行离散化并初步计入了速度对非稳态性的影响，推导出侧向力和回正力矩关于侧向位移和摆动角的传递函数的解析公式，可以计算不同载荷下的非稳态特性，计算结果与文献中的试验结果相符，建模和计算结果说明利用试验模态参数可以方便地建立轮胎的非稳态特性，计算结果与     

A Study on the Tire Load Calculation for Multi-axle Vehicles Based on Displacement Method

针对多轴汽车轮胎载荷计算的超静定问题的求解复杂性,基于位移法、刚体车身假设和车身刚体位移与轮胎等效变形之间的关系,以车身位移为未知量建立了车身的平衡方程;考虑整车重力、纵横向惯性力和转弯工况质心侧向位移引起的侧倾力矩的作用,建立了多轴汽车在弯曲、扭转、起动/制动和转弯等工况下轮胎载荷的矩阵方程,只需简单的线性代数计算即可方便地求得各种工况下的轮胎载荷.     

轿车车轮应力的实验研究

介绍轿车车轮在轮胎充气、螺栓拧紧、垂直负荷、制动四种工况的应力测试及结果分析，由此可得出其应力在轮辋、轮辐上的分布规律。     

排气制动对增压器轴向载荷影响的研究

针对车辆上同时应用排气制动与涡轮增压的情况,研究了排气制动对增压器轴向载荷的影响。通过排气制动与增压器联动试验测量了增压器在各个工况下的轴向载荷,从而确定了数值计算所需的边界条件,并通过数值计算获取了增压器在各个工况的轴向载荷的分布情况。结果表明,与正常工况相比,增压器在排气制动工况下其轴向载荷显著增大,且排气背压越高,增压器轴向载荷越大;涡轮级轴向载荷反向且增大;压气机级轴向载荷显著下降,但方向不变。     

轮胎附着极限下差动制动对汽车横摆力矩的影响

本文以纵滑－侧偏联合工况的稳态轮胎模型为基础，分析了汽车极限转向条件下制动作用于不同车轮时对汽车横摆力矩的影响，并通过整车动力学仿真进行了验证，研究结果为利用差动制动控制提高汽车的高速操纵稳定性提供了动力学依据。     

轮胎动力学特性仿真分析研究

分析了各种常用轮胎模型的特点与应用范围,根据汽车操纵动力学研究的需求,在Matlab环境下运用魔术公式建立了轮胎动力学模型,并对汽车轮胎力与纵向滑移率,纵向力、侧向力及回正力矩与纵向滑移率、侧偏角、外倾角、垂直载荷的关系等轮胎特性进行了仿真分析,实验结果表明,魔术公式轮胎动力学模型可以较好地模拟轮胎的动力学特性,适用于车辆动力学研究领域。     

电子差速系统轮胎附着特性模拟仿真研究

电子差速系统相对于传统的机械式差速器可以实现转矩的精准分配,根据轮胎的纵向运动特性以及侧向运动特性,结合轮胎滑移率让内外侧车轮在过弯时拥有足够的附着力,减小整车的横摆角速度,提高过弯稳定性。采用后轮双电机的驱动方案,驱动电机采用直接转矩控制的方法,由整车控制器将指定的计算转矩信号发送给电机控制器完成动力分配,所需转矩根据驾驶员的加速踏板及方向盘转角,运用阿克曼转向模型计算得到。     

Longitudinal Tire Dynamics

This article begins with a brief review of the traditional concept of lateral relaxation length. The review illustrates that this concept yields a useful approximation which can be used with semi-empirical tire models which assume lateral forces are a function of steady-state slip angles. The article then presents an analogous derivation for longitudinal slip. Like its lateral counterpart, the derivation yields an approximation for transient longitudinal slip which can be used with tire models which assume longitudinal forces are a function of steady-state longitudinal slip. It is shown that, like the relaxation-length-based lateral slip angle, this formulation for longitudinal slip yields the ability to compute shear forces at the tire/road interface for either high or low speed applications, a necessary feature of simulations which support human in the loop driving simulation. Like traditional kinematically-based longitudinal slip, the transient formulation presented here is coupled with the wheel spin equation, and it shares the characteristic that it is very stiff compared to the equations of vehicle motion. This characteristic is a challenge impeding the real-time calculations required for driving simulation. The paper shows that local linearization of the wheel spin equations coupled with analytical solutions of the transient longitudinal slip formulation provide the basis for both insight into the longitudinal dynamics of the tire and for integrating the model in real-time.     

汽车防抱死制动系统的自抗扰控制研究

汽车防抱死制动系统(Anti-lock Braking System,ABS)的作用是确保汽车制动时行驶方向的稳定性、可靠性,但是目前仍存在非线性、时变性以及参数不确定性等问题.为保证汽车制动行驶过程中的操纵稳定性和安全性,进一步实现各工况下防抱死制动系统的优化控制,以影响整车稳定的变量滑移率为研究对象,分析所设计策略...     

Longitudinal Tire Dynamics

SUMMARY

This article begins with a brief review of the traditional concept of lateral relaxation length. The review illustrates that this concept yields a useful approximation which can be used with semi-empirical tire models which assume lateral forces are a function of steady-state slip angles. The article then presents an analogous derivation for longitudinal slip. Like its lateral counterpart, the derivation yields an approximation for transient longitudinal slip which can be used with tire models which assume longitudinal forces are a function of steady-state longitudinal slip. It is shown that, like the relaxation-length-based lateral slip angle, this formulation for longitudinal slip yields the ability to compute shear forces at the tire/road interface for either high or low speed applications, a necessary feature of simulations which support human in the loop driving simulation. Like traditional kinematically-based longitudinal slip, the transient formulation presented here is coupled with the wheel spin equation, and it shares the characteristic that it is very stiff compared to the equations of vehicle motion. This characteristic is a challenge impeding the real-time calculations required for driving simulation. The paper shows that local linearization of the wheel spin equations coupled with analytical solutions of the transient longitudinal slip formulation provide the basis for both insight into the longitudinal dynamics of the tire and for integrating the model in real-time.     

变路面车辆稳定性控制策略研究

建立了某四轮汽车9自由度车辆模型和轮胎动力模型,并提出了一种基于侧向力利用系数的差动制动、主动转向切换控制策略。模拟了汽车以车速24.5m/s行驶时的一个紧急避让情况,研究了无控制模式、差动制动控制模式、联合控制模式下的车辆横摆角速度、质心侧偏角、质心侧向位移的变化。结果表明,所提出的差动制动联合主动转向技术的控制策略可以满足变路面下车辆稳定性控制要求。     

Electronic stability control for electric vehicle with four in-wheel motors

The electric vehicle with four direct-driven in-wheel motors is an over actuated system. A three-level control strategy of electronic stability control (ESC) is proposed to achieve optimal torque distribution for four in-wheel motors. The first level is a gain-scheduled linear quadratic regulator which is designed to generate the desired yaw moment command for ESC. Control allocation is the second level which is used to distribute the desired longitudinal tire forces according to the yaw moment command while satisfying the driver’s intent for acceleration and deceleration. The associated weighting matrix is designed using the work load ratio at each wheel to prevent saturating the tire. The third level is slip ratio control (SRC) which is employed at each wheel to generate the desired longitudinal tire force based on a combined-slip tire model. Simulation results show that the proposed method can enhance the ESC performance for the test maneuvers. Since the tire model is often unknown for practical implementation, the effectiveness of the SRC is studied using the sine with dwell test. It is found that the SRC is not crucial for achieving performance similar to the proposed method with SRC, if the slip ratio can be maintained in the stable region using traction control system/anti-lock braking system.     

Dynamic Friction Models for Road/Tire Longitudinal Interaction

Summary In this paper we derive a new dynamic friction force model for the longitudinal road/tire interaction for wheeled ground vehicles. The model is based on a dynamic friction model developed previously for contact-point friction problems, called the LuGre model. By assuming a contact patch between the tire and the ground we develop a partial differential equation for the distribution of the friction force along the patch. An ordinary differential equation (the lumped model) for the friction force is developed, based on the patch boundary conditions and the normal force distribution along the contact patch. This lumped model is derived to approximate closely the distributed friction model. Contrary to common static friction/slip maps, it is shown that this new dynamic friction model is able to capture accurately the transient behaviour of the friction force observed during transitions between braking and acceleration. A velocity-dependent, steady-state expression of the friction force versus the slip coefficient is also developed that allows easy tuning of the model parameters by comparison with steady-state experimental data. Experimental results validate the accuracy of the new tire friction model in predicting the friction force during transient vehicle motion. It is expected that this new model will be very helpful for tire friction modeling as well as for anti-lock braking (ABS) and traction control design.