Driving Force Model for Non-pneumatic Elastic Wheel

In order to obtain good driving performance,a driving force model is presented for non-pneumatic elastic wheel.Brush model of pneumatic tyres is introduced and the deformations of elastic supports and tread are also taken into account.The longitudinal slip rate is redefined.The grounding pressure distribution of elastic wheels is analyzed and corrected according to speed,temperature and stiffness.Then rolling resistance equation is developed.Finally,simulation is conducted by software CarSim,and the results show that the estimated values are consistent with simulation values,especially at low longitudinal slip rate.The research can help to optimize design of non-pneumatic elastic wheel.

Non-pneumatic mechanical elastic wheel natural dynamic characteristics and influencing factors

Non-pneumatic tire appears to have advantages over traditional pneumatic tire in terms of flat proof and maintenance free.A mechanical elastic wheel(MEW) with a non-pneumatic elastic outer ring which functions as air of pneumatic tire was presented.The structure of MEW was non-inflatable integrated configuration and the effect of hinges was accounted for only in tension. To establish finite element model of MEW, various nonlinear factors, such as geometrical nonlinearity, material nonlinearity and contact nonlinearity, were considered. Load characteristic test was conducted by tyre dynamic test-bed to obtain force-deflection curve. And the finite element model was validated through load characteristic test. Natural dynamic characteristics of the MEW and its influencing factors were investigated based on the finite element model. Simulation results show that the finite element model closely matched experimental wheel. The results also show that natural frequency is related to ground constraints, material properties, loads and torques. Influencing factors as above obviously affect the amplitude of mode of vibration, but have little effect on mode of vibration shape. The results can provide guidance for experiment research, structural optimization of MEW.

Influence Analysis of Machining and Installation Errors on the Radial Stiffness of a Non-Pneumatic Mechanical Elastic Wheel

Machining and installation errors are unavoidable in mechanical structures. However, the effect of errors on radial stiffness of the mechanical elastic wheel(ME-Wheel) is not considered in previous studies. To this end, the interval mathematical model and interval finite element model of the ME-Wheel were both established and compared with bench test results. The intercomparison of the influence of the machining and installation errors on the ME-Wheel radial stiffness revealed good consistency among the interval mathematical analysis, interval finite element simulation,and bench test results. Within the interval range of the ME-Wheel machining and installation errors, parametric analysis of the combined elastic rings was performed at different initial radial rigidity values. The results showed that the initial radial stiffness of the flexible tire body significantly influenced the ME-Wheel radial stiffness, and the inverse relationship between the hinge unit length or suspension hub and the radial stiffness was nonlinear. The radial stiffness of the ME-Wheel is predicted by using the interval algorithm for the first time, and the regularity of the radial stiffness between the error and the load on the ME-Wheel is studied, which will lay the foundation for the exact study of the ME-Wheel dynamic characteristics in the future.

Steady-State Cornering Properties of a Non-pneumatic Tire with Mechanical Elastic Structure

Mechanical elastic wheel(ME-wheel)is a new type of non-inflatable safety tyre,and the structure is significantly different from traditional pneumatic tyre.In order to investigate cornering properties of ME-wheel,experimental research on mechanics characteristics of ME-wheel under steady-state cornering conditions are carried out.The test of steady-state cornering properties of ME-wheel at different experimental parameter conditions is conducted by test bench for dynamic mechanical properties of tyre.Cornering property curves are used to analyze the steady-state cornering properties of ME-wheel,namely the variation tendency of lateral force or aligning torque with the increase of side-slip angle.Moreover,evaluation indexes for cornering properties of ME-wheel are extracted and the effect of different experimental parameters(including vertical load,friction coefficient,and speed)on cornering properties of ME-wheel is contrastively analyzed.The proposed research can provide certain reference to facilitate structure parameters and cornering properties optimizing process of ME-wheel.

Integrated yaw and rollover control based on differential braking for off-road vehicles with mechanical elastic wheel

Aiming at the issue of yaw and rollover stability control for off-road vehicles with non-pneumatic mechanical elastic wheel(MEW),an integrated control system based on fuzzy differential braking is developed.By simplifying the structure of the MEW,a corresponding fitting brush tire model is constructed and its longitudinal and lateral tire force expressions are set up,respectively.Then,a nonlinear vehicle simulation model with MEW is established to validate the proposed control scheme based on Carsim.The designed yaw and rollover control system is a two-level structure with the upper additional moment controller,which utilizes a predictive load transfer ratio(PLTR)as the rollover index.In order to design the upper integrated control algorithm,fuzzy proportional-integral-derivative(PID)is adopted to coordinate the yaw and rollover control,simultaneously.And the lower control allocator realizes the additional moment to the vehicle by differential braking.Finally,a Carsim-simulink co-simulation model is constructed,and simulation results show that the integrated control system could improve the vehicle yaw and roll stability,and prevent rollover happening.

Static Radical Stiffness and Contact Behavior of Nonpneumatic Mechanical Elastic Wheel

Conventional pneumatic tires exhibit disadvantages such as puncture,blowout at high speed,pressure maintenance,etc.Owing to these structural inevitable weaknesses,non?pneumatic tires have been developed and are investigated.A non?pneumatic mechanical elastic wheel(NPMEW)is introduced and investigated as a function of static radical stiffness characteristics and contact behavior.A bench test method is utilized to improve the riding comfort and the traction traffic ability of NPMEW based on tire characteristics test rig,and the static radical stiffness characteristics and the contact behavior of NPMEW are compared with that of an insert supporting run?flat tire(ISRFT).The vertical force?deformation curves and deformed shapes and contact areas of the NPMEW and ISRFT are obtained using a set of vertical loads.The contact behavior is evaluated using extracted geometrical and mechanical feature parameters of the two tires.The results indicate that the NPMEW appears to exhibit considerably high radical stiffness,and the numerical value is dependent on the mechanical characteristic of the flexible tire body and hinge units.NPMEW demonstrates more uniform contact pressure than ISRFT within a certain loading range,and it can efficiently mitigate the problem of stress concentration in ISRFT shoulder under heavy load and enhance the wear resistance and ground grip performances.

ELASTIC-PLASTIC FINITE ELEMENT ANALYSIS OF THREE-DIMENSIONAL CONTACT-IMPACT AT RAIL JOINT

Using the finite element code ANSYS/LS-DYNA, a dynamic finite element modelwith an elastic-linear-kinematic-hardening plastic material is established to analyzeelastic-plastic stresses in the railhead in the impact process of wheel and rail occurring at thegap of rail joint. The model is based on the discrete elastic support condition of the rails, whichis suitable for the actual situation of wheel/track rolling contact. In the analysis the influencesof axle load, yield stress and tangent modulus of rail material on the stresses and strains areinvestigated in detail. The distribution of stresses and strains in the jointed railhead are given.It is found that the axle load, yield stress and tangent modulus of rail material greatly affect thestresses and strains in the railhead during impacting. The study provides a reliable method anduseful datum for the further research on fatigue and wear of railhead and improving the rail jointmode.

Investigation into rail corrugation in high-speed railway tracks from the viewpoint of the frictional self-excited vibration of a wheel–rail system

A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the model, the creep forces between the wheels and rail are considered to be saturated and equal to the normal contact forces times the friction coefficient. The oscillation of the rail is coupled with that of wheels in the action of the saturated creep forces. When the coupling is strong, self- excited oscillation of the wheel-rail system occurs. The self-excited vibration propensity of the model is analyzed using the complex eigenvalue method. Results show that there are strong propensities of unstable self-excited vibrations whose frequencies are less than 1,200 Hz under some conditions. Preventing wheels from slipping on rails is an effective method for suppressing rail corrugation in high-speed tracks.

采用弹性车轮的独立轮对有轨电车曲线通过动力学性能研究

采用动力学仿真软件SIMPACK,利用离散刚度阻尼单元模拟弹性车轮的弹性变形特性,建立了三编组现代有轨电车列车动力学计算模型,对比分析了曲线半径R400 m线路条件下弹性车轮在时域和频域内的减振性能,讨论了50~400 m不同半径的曲线线路条件下不同轮对形式的弹性车轮对中间拖车曲线通过性能的影响。计算结果显示:弹性车轮能够减小20~40 Hz、50~70 Hz和180~300 Hz频率范围内的车体垂向振动以及20~550 Hz范围内的车体横向振动。从轮对横移量和轮重减载率看,曲线半径R200 m左右是弹性车轮传统轮对和弹性车轮独立轮对曲线导向能力的分界点;从轮轨横向蠕滑率、轮对摇头角、脱轨系数和轮轴横向力看,曲线半径R100 m左右是分界点。

组合弹性无缘轮半被动行走的混沌和同步分析

本文提出了组合弹性无缘轮模型,通过加入周期振荡的间接控制,实现了组合弹性无缘轮的半被动行走.通过观察组合弹性无缘轮半被动行走的步态,分析了混沌和同步化的非线性行为.首先,建立组合弹性无缘轮半被动行走的动力学模型,使其能够实现稳定的周期行走;其次,通过对组合弹性无缘轮半被动行走的典型步态分析,表明极限环的稳定性对初始条件敏感;最后,通过观察组合弹性无缘轮半被动行走的步态,分析振荡频率与系统行走频率关系,以及振荡频率与系统行走频率的相位差与行走步数之间是否存在同步化和混沌等非线性行为.仿真结果表明,对于振荡频率与系统行走频率之间的关系,较轻的摆动质量和较小的摆动振幅呈现出同步化现象,较重的摆动质量和较大的摆动振幅呈现出混沌现象;对于振荡频率与系统行走频率的相位差与行走步数的关系,较轻的摆动质量和较小的摆动振幅呈现出混沌现象.

基于变腿长的弹性无缘轮动力学与行走控制

研究弹性无缘轮沿斜面半被动行走的动力学建模和控制问题.首先基于弹簧负载倒立摆模型,利用拉格朗日方法建立弹性无缘轮的动力学模型;其次采用反馈线性化的思想设计控制器,通过控制弹性腿的长度,缩小弹性无缘轮行走误差,实现稳定的周期行走;最后,在理论研究的基础上进行了仿真实验,验证了基于变腿长的控制策略在外部干扰和自身参数误差的情况下的控制效果,同时在仿真实验中发现,相同的外部扰动作用在单、双支撑不同阶段会产生不同的影响,分析了产生这种差异的原因.仿真结果表明:基于变腿长设计的控制器能够实现弹性无缘轮沿斜坡的稳定行走,同时能对来自外界的干扰进行有效抑制,使弹性无缘轮迅速恢复到周期性稳定行走状态,并且在弹性无缘轮自身参数有误差时仍具有相当的鲁棒性.

基于车辆动力学的铁路轨道曲线啸叫时域模型

曲线啸叫是轮轨切向黏滑接触、轮轨动力学和通过曲线时车辆运行状态的综合结果。为综合研究曲线啸叫的影响因素,基于整车车辆多体动力学,并采用改进的轮轨接触力计算方法,建立了曲线啸叫时域模型。在接触力计算中,使用了离散接触模型,为引入下落摩擦机理,在切向力计算中使用迭代方法确定摩擦系数和接触力,使用模态叠加法计算车轮振动响应,采用无限元方法计算车轮声辐射。研究不同曲线半径和通过速度下,曲线段轮轨间接触力的变化及接触区的黏着-滑动状态,对车轮振动特性进行分析,并研究了车轮声学响应。研究发现,在下落摩擦和整车车辆运动状态的共同作用下会出现啸叫现象;曲线段轮轨间的法向力和切向力均会出现振荡,接触区呈现黏滑振荡状态;车轮振动速度谱的峰值频率与车轮特征模态相近,车轮轴向和径向模态的高幅振动是高频啸叫的原因之一。啸叫现象主要出现在前轮上,相同工况下,前后轮声压级相差近20 dB,车辆速度和曲线半径对啸叫程度有明显影响,当车辆的曲线通过速度为60 km/h时,小曲线半径会出现严重啸叫现象;当曲线半径由200 m增大到400 m时,最大声压级降低34 dB;曲线通过速度由60 km/h降至40 km/h时,最大声压级下降13 dB。

机械弹性电动轮驱动车辆横摆稳定性协调控制

针对匹配机械弹性电动轮(MEEW)车辆的横摆稳定性控制问题,提出一种基于主动前轮转向(AFS)与直接横摆力矩控制(DYC)的稳定性协调控制策略。为修正车辆行驶过程中的前轮转角输入,设计了基于微分平坦与RBF神经网络的AFS控制器,从而提高车辆的转向能力。针对AFS控制器在极限工况下易失效的缺陷,引入基于线性二次型调节器(LQR)的直接横摆力矩控制算法,并依照轴荷比分配四轮力矩。最后,依据机械弹性电动轮的质心侧偏角-质心侧偏角速度相平面图划分稳定域,实现AFS与DYC的协调控制。通过Matlab/Simulink和Carsim进行联合仿真,结果表明:所提出的AFS控制算法在高速高附着工况下有良好的稳定控制性能,但在高速、低附着极限工况下控制效果受到影响。而AFS/DYC协调控制策略效果较好,跟踪精度优于单一控制器,质心侧偏角和横摆角速度的最大跟踪误差仅为3.03°和1.82(°)/s,可保证汽车在极限工况下转向时的横摆稳定性。

机械弹性车轮的滚动模态特性研究

轮胎是农用车辆行走系的重要部件,直接影响车辆各种使用性能的发挥。针对传统农用车轮胎在使用过程中易扎伤、易磨损等问题,设计了一种新型机械弹性车轮。利用有限元方法结合LMS模态试验,研究了各种因素对机械弹性车轮模态参数的影响机理和规律,计算了滚动状态下机械弹性车轮的模态参数,获得了转速对车轮模态参数的影响规律,从而得到了滚动状态下机械弹性车轮的模态特性。研究结果表明,机械弹性车轮在滚动状态下的模态特性可为其与农业车辆的匹配提供一定的指导。

弹性车轮动刚度与随机振动疲劳仿真分析

在城市轨道交通中,弹性车轮作为列车的主要承载部件,在减振降噪方面发挥着极大的作用。为了进一步探究某型弹性车轮相对于刚性车轮在减振降噪方面的优势,在弹性车轮建模方法和对弹性车轮中橡胶材料本构模型研究的基础上,利用Hypermesh软件建立了弹性车轮和刚性车轮的有限元模型,基于Optistruct模块对弹性车轮和刚性车轮的动刚度进行仿真分析,得出了两者在相同测试点的速度、加速度频率响应曲线,结果表明弹性车轮在高频率区间内具有显著的减振效果。另外在Ansys软件中对该型弹性车轮在随机振动条件下的疲劳寿命进行了预测,通过分析车轮的等效应力分布云图和疲劳寿命分布云图,对弹性车轮应力集中部位进行尺寸改进,结果表明改进后弹性车轮的疲劳寿命显著提高。

弹性腿无边轮的节律步态分析与仿真

本文针对弹性腿的被动平面无边轮的行走步态特征进行不同结构参数下的仿真模拟对比,并对其运动过程中的能量转换行为及结构参数对生成被动行走节律步态的影响进行分析。

某型有轨电车弹性车轮迟缓试验研究

[目的]某型有轨电车在服役过程中出现弹性车轮迟缓线错位,对车辆的安全运维存在较大影响,故有必要开展相关研究。[方法]利用弹性车轮的质量检测、列车正线测试和仿真计算等方法开展试验研究,深入分析车轮迟缓线错位的原因。[结果及结论]弹性车轮的自身产品性能满足标准和服役要求,其稳定性和可靠性较高;列车在小曲线区段的振动水平高于直线区段,其中垂向振动加速度均方根值达2.77 g;且在曲线区段存在300.00~450.00 Hz的振动主频,与弹性车轮的固有模态频率340.37 Hz相匹配,导致车轮与钢轨在该区段的耦合共振。因此,建议该线路在运维中一方面加强轮轨的润滑作业,另一方面提高小曲线区段钢轨波磨的勘察频次,以实现轮轨摩擦因数的降低和车轮运维环境的提升。

弹性车轮橡胶块疲劳寿命分析及刚度设计

采用Mooney-Rivlin模型,建立了弹性车轮橡胶块非线性有限元本构模型,并仿真分析和计算了橡胶块运行过程中各工况下的应力和应变;研究了弹性车轮整体刚度与橡胶块使用寿命的关系。结果表明,为保证弹性车轮的使用安全性和经济性,弹性车轮径向刚度和轴向刚度设计范围应在100~200 MN/m和10~20 MN/m之间。

聚氨酯橡胶弹簧在平面闸门导向装置中的应用

针对传统平面闸门反向导向装置易造成止水贴合不严、无法计算变形反力等缺点,文章介绍了一种采用聚氨酯橡胶弹簧的弹性导向轮,用作平面闸门的反向、侧向导向装置,在实际工程运用中取得良好效果,可供类似工程参考。

A New Method for Dressing Fine Grain Diamond Wheels——the Soft-Elastic Dressing Method

This paper describes a completely new dressing technique, the soft-elastic dressing method, which can effectively dress fine grain diamond wheels. A rotating and vibrating abrasive belt is used in the soft-elastic dressing method. The principle of the new dressing technique and the soft-elastic dressing equipment are presented. Factors that influence the truing efficiency, truing precision and sharpening quality are carefully investigated. The grinding surface roughness after soft-elastic dressing is performed is investigated experimentally. The dressing and grinding experiments both prove that the soft-elastic dressing method has high truing efficiency, high truing precision and good sharpening quality.[