四轴全轮转向车辆操纵稳定性分析

建立了四轴全轮转向车辆的线性二自由度车辆模型,进行了理论分析和数学公式推导。以某四轴重型运输车为例,基于零质心侧偏角策略确定转向瞬心位置以及后桥转角与前桥转角的比例关系,并讨论了全轮转向对车辆稳态响应和瞬态响应的影响。     

A Steering Dynamics Analysis for Skid-Steering Wheeled Vehicle Based on Single-axle Model

通过对速差转向车辆进行简化,建立了其2自由度动力学单轴模型.在此基础上,考虑转向时轮荷的转移,给出整车的动力学微分方程,继而研究车辆参数对速差转向性能的影响.结果表明,速差转向轮式车辆的速度瞬心位于车辆几何中心之前,其内侧车轮仅在转向半径较小时吸收功率.     

小词典

车辆响应车辆响应是指由外界输入或内部输入引起的摩托车的运动。其有: 由驾驶员控制转向把引起的摩托车的运动称为控制响应; 由施加于摩托车上的非所需输入而引起的摩托车的运动称为扰动响应,例如风力或路面不平引起的摩托车的运动。稳态响应当周期性的控制输入和扰动输入施加于摩托车,引起了不是随时间而变的周期性的摩托车运动时,称摩托车处     

不同转向模式的多轴转向车辆性能分析

为解决重型车辆转向时的低速机动性和高速稳定性的问题,提出了多轴动态转向技术,并以三轴车辆为研究对象进行分析。首先建立多轴转向的二自由度车辆模型以及运动微分方程,为提高车辆的稳定性,以零质心侧偏角为目标,推导各轴间的转角比例系数及有关的状态空间矩阵、传递函数,使用MATLAB软件对不同转向模式下的操纵稳定性进行了稳态响应、瞬态响应以及频域响应的仿真。通过分析比较,说明采用多轴动态转向技术,车辆在转向时具有低速机动性高、高速稳定性好的特点。     

整体式梯形转向机构最优区域值计算和优化

为了得到整体式梯形转向机构尺寸的最优值,结合其工作特性进行了数学模型建立与优化分析。在以往以外侧车轮实际转角与理论转角误差为目标函数的基础上,提出了以汽车实际瞬心位置与阿克曼瞬心位置的误差为目标函数,使实际瞬心位置在理论瞬心位置附近波动的最大值最小,从而优化转向梯形机构的相关尺寸参数,进一步得到更接近理想的阿克曼转向机构。通过数值方法,模拟了瞬心位置曲线,以梯形杆长作为优化目标,并以位置误差最小化作为目标函数,得到了机构杆长最优区域值。在得到的计算区域里选取数值计算与理论数学模型计算进行结果对比,认为最优区域是存在的。通过引入已有计算参数,在得到的最优区域里选配合适的机构杆长尺寸,进一步绘制出理想的优化后转向机构外侧车轮转角误差和瞬心位置误差的偏差曲线,对方法进行了验证。结果表明:在最优区域内选取转向机构的杆长进行数值计算是合理的;外侧车轮转角误差最大值不超过0. 45°,误差在2%以内,同时,瞬心位置误差最大值不超过40 mm。整体式梯形转向机构最优区域值计算方法为该类优化问题提供了一种全局最优解,并为梯形转向机构的设计提供了规范性的指导与依据。     

某轿跑SUV提升转向响应的硬点优化仿真与验证

针对某SUV车型的前悬架响应慢,进行了前悬架的仿真优化分析,通过抬高转向器安装硬点位置可以优化前悬架侧倾转向和平跳转向的特性,减小不足转向度,提升整车响应特性,然后进行客观测试来对比指标变化,最后得出结论通过加高转向器安装硬点可以提升整车转向响应。     

某超重型越野汽车全轮转向系统转角匹配研究

本文对全轮转向系统的使用工况、安全性设计等进行了解析,并初步归纳了不同转向模式的使用条件。根据分析,对转向瞬心的布置、转向系统的转角分配、车轮转角控制要求等进行了阐述,为全轮转向的工程应用提供了理论基础。     

电动助力转向中间位置转向感觉分析

针对电动助力转向系统(EPS)的转向感觉进行了系统分析,其中转向盘中间位置的转向主观感受是汽车转向感觉研究的主要内容,直接影响驾驶员对稳定性、安全性和行驶的判断,研究通过整车中间位置转向感觉主观评价试验,介绍了试验及数据处理方法,并对客观评价指标进行了分析.分别研究了中间位置转向灵敏程度,转向手力特性,以及中间位置行驶时的汽车响应特性等三方面的客观评价指标.应用这些指标参数,可以系统全面的评定EPS中间位置转向感觉,指导EPS与整车的匹配开发,以获得更适宜的中间位置转向感觉.     

多轴分布式电驱动车辆后桥差动转向控制策略研究

首先建立了八轴分布式电驱动车辆动力学模型,提出了基于质心侧偏角的差动转向双层控制策略,上层控制器以质心侧偏角及其变化率和前轮转角为输入,采用模糊控制生成机械转向桥和差动转向桥的转向中心相对位置,从而获得后桥转向参考转向角;下层控制器以上层转向参考角为控制目标,采用增量式数字PI控制得到后桥电机的差动转矩。最后选取中高速工况,进行硬件在环仿真,验证了后桥差动转向控制效果和实时性。结果表明,与理想阿克曼转向策略相比,该策略能有效减小车辆转向过程中质心侧偏角,并保证了转向稳定性。     

双横臂独立悬架的设计中转向与悬架的匹配

针对汽车双横臂前独立悬架系统，提出了一种确定转向系统向拉杆理想长度和理想角度的近似计算公式，指出车轮纵摆瞬心的存在对转向拉杆理想长度和前束角变化的影响。并以ＺＱ６４００、ＺＱ６４５０Ｎ，ＺＱ６４４０３种类型为例，探讨了应如何确定转向拉杆的参数，控制前束的变化规律，以保证与悬架导向机构的匹配，提高汽车操纵稳定性。     

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。     

双前桥转向系统瞬时转动中心理论分析及二轴转角的确定

建立了双前桥转向系统瞬时转动中心的数学模型,进行了理论分析和数学公式推导,得出了转动中心位置的一般公式以及一轴、二轴转角关系式。以某车型为例讨论了二轴转角、偏移和转动半径分别在不同双后轴距离处以及一轴不同转角条件下的变化规律。结果表明,瞬时转动中心不在后二轴中心线上,而是相对后二轴中心向后偏移,且偏移量随后二轴轴距增大而增大;前一轴转角对于瞬时转动中心的影响不大。转向半径随着后二轴轴距增大而增大;当一轴转角较小时,转向半径变化很大,当一轴转角最大时转向半径达到最小。     

Overturning Stability of Three Wheeled Motorized Vehicles

Three wheeled motorized vehicles are a major mode of public transport in many countries. These vehicles are prone to overturning even during normal turning and obstacle avoidance maneuvers. This paper presents a parametric analysis of a mathematical model of the vehicle and evolves guidelines for improving the overturning stability in terms of vehicle geometry and suspension properties.

Differential equations governing the dynamic behavior of the vehicle are derived on the basis of a six degree of freedom model. The vehicle response to variations in steering, engine power and braking inputs is then numerically simulated. The effects of vehicle geometry and elasto-damping suspension coefficients on the vehicle stability are presented. The results indicate an optimum position of the center of gravity where the vehicle is most stable. While stiffer suspensions favour stability, there exists an optimum value of suspension damping for which the minimum wheel load is a maximum.     

Static Turning Analysis of Vehicles Subject to Externally Applied Forces - A Moment Arm Ratio Formulation

A formulation for representing the static turning response of a two-axle vehicle due to applied external or control forces is expressed in terms of a simple ratio of two distances along the vehicle longitudinal axis. The two distancescoincide with points on the vehicle at which externally applied/ control forces and their reactive inertial forces act with respect to the vehicle neutral steer point. The resulting formulation is equivalent to the rotational equilibrium equation written with respect to the neutral steer point. The method allows a simple “visual analysis” of the steady turning process by showing how key forces and associated moment arms can change with respect to one another due to vehicle modifications or different operatingconditions, thereby affecting the static turning response of the vehicle.     

模数式桥梁伸缩缝水平向动力学响应分析

运用有限元分析软件对模数式桥梁伸缩缝进行水平向动力学研究,建立了其水平向有限元动力学模型,研究了车轮对中梁的水平冲击以及车速、中梁弹性支承刚度及预压量、滑动摩擦系数和剪切弹簧刚度的变化对中梁水平位移的响应特性。研究表明,当车速高于100 km/h,中梁弹性支承刚度小于70 000 N/mm时,应考虑车轮对中梁的水平冲击,当车速低于120 km/h,中梁弹性支承刚度及预压量分别大于80 000 N/mm和0.3 mm,滑动摩擦系数大于0.03,剪切弹簧刚度大于400 N/mm时,此时中梁水平位移小于0.5 mm,且车轮对中梁的水平冲击也可不考虑。     

Static Turning Analysis of Vehicles Subject to Externally Applied Forces - A Moment Arm Ratio Formulation

SUMMARY

A formulation for representing the static turning response of a two-axle vehicle due to applied external or control forces is expressed in terms of a simple ratio of two distances along the vehicle longitudinal axis. The two distancescoincide with points on the vehicle at which externally applied/ control forces and their reactive inertial forces act with respect to the vehicle neutral steer point. The resulting formulation is equivalent to the rotational equilibrium equation written with respect to the neutral steer point. The method allows a simple “visual analysis” of the steady turning process by showing how key forces and associated moment arms can change with respect to one another due to vehicle modifications or different operatingconditions, thereby affecting the static turning response of the vehicle.     

重型车双前轴转向梯形及杆系的设计与计算

转向梯形机构的几何参数决定汽车转向时内、外转向轮转角的几何关系,在汽车转向时,各车轮的转向必须保证纯滚动而无滑动,使各车轮的转角必须保证有统一的瞬时转向中心。本文主要概述了重型车双前轴转向梯形及杆系的设计与计算。     

Effects of multiple axles on the lateral dynamics of multi-articulated vehicles

This paper describes an analytical study of the lateral dynamics of multi-articulated vehicles with multiple axles. A linear planar model of vehicle dynamics is adopted for multiple-axle vehicle combinations with an optional number of trailers. Two tractor and double-trailer combinations are examined for their directional stability and response. Non-oscillatory stability and steering sensitivity in steady-state turning and lane changing are analysed using a stability factor of multiple-axle vehicle combinations. Off-tracking in the steady-state turning of multiple-axle vehicle combinations is also analysed. Numerical calculations for oscillatory stability, steering sensitivity, and off-tracking are presented for multiple-axle vehicle combinations.     

Roll Plane Analysis of Articulated Tank Vehicles During Steady Turning

The rollover immunity levels of articulated tank vehicles with partial loads are investigated. A static roll plane model of the articulated vehicle employing partially filled cylindrical tank is developed. The vertical and lateral translation of the liquid cargo due to vehicle roll angle and lateral acceleration, encountered during steady turning, are evaluated. The roll moments arising from vertical and lateral translation of the liquid cargo are determined and incorporated in the roll plane model of the vehicle. The adverse influence of the unique interactions of the liquid within the tank vehicle, on the rollover limit of the articulated vehicle is demonstrated. The influence of compartmenting of the tank on the steady turning roll response of the vehicle is analyzed, and an optimal order of unloading the compartmented tank is discussed.     

Roll Plane Analysis of Articulated Tank Vehicles During Steady Turning

SUMMARY

The rollover immunity levels of articulated tank vehicles with partial loads are investigated. A static roll plane model of the articulated vehicle employing partially filled cylindrical tank is developed. The vertical and lateral translation of the liquid cargo due to vehicle roll angle and lateral acceleration, encountered during steady turning, are evaluated. The roll moments arising from vertical and lateral translation of the liquid cargo are determined and incorporated in the roll plane model of the vehicle. The adverse influence of the unique interactions of the liquid within the tank vehicle, on the rollover limit of the articulated vehicle is demonstrated. The influence of compartmenting of the tank on the steady turning roll response of the vehicle is analyzed, and an optimal order of unloading the compartmented tank is discussed.