Influence of Tire Dynamics on Slip Ratio Estimation of Independent Driving Wheel System

The independent driving wheel system, which is composed of in-wheel permanent magnet synchronous motor（I-PMSM） and tire, is more convenient to estimate the slip ratio because the rotary speed of the rotor can be accurately measured. However, the ring speed of the tire ring doesn’t equal to the rotor speed considering the tire deformation. For this reason, a deformable tire and a detailed I-PMSM are modeled by using Matlab/Simulink. Moreover, the tire/road contact interface（a slippery road） is accurately described by the non-linear relaxation length-based model and the Magic Formula pragmatic model. Based on the relatively accurate model, the error of slip ratio estimated by the rotor rotary speed is analyzed in both time and frequency domains when a quarter car is started by the I-PMSM with a definite target torque input curve. In addition, the natural frequencies（NFs） of the driving wheel system with variable parameters are illustrated to present the relationship between the slip ratio estimation error and the NF. According to this relationship, a low-pass filter, whose cut-off frequency corresponds to the NF, is proposed to eliminate the error in the estimated slip ratio. The analysis, concerning the effect of the driving wheel parameters and road conditions on slip ratio estimation, shows that the peak estimation error can be reduced up to 75% when the LPF is adopted. The robustness and effectiveness of the LPF are therefore validated. This paper builds up the deformable tire model and the detailed I-PMSM models, and analyzes the effect of the driving wheel parameters and road conditions on slip ratio estimation.

Dynamics and Wheel's Slip Ratio of a Wheel-legged Robot in Wheeled Motion Considering the Change of Height

The existing research on dynamics and slip ratio of wheeled mobile robot （WMR） are derived without considering the effect of height, and the existing models can not be used to analyze the dynamics performance of the robot with variable height while moving such as NOROS- Ⅱ. The existing method of dynamics modeling is improved by adding the constraint equation between perpendicular displacement of body and horizontal displacement of wheel into the constraint conditions. The dynamic model of NOROS- Ⅱ in wheel motion is built by the Lagrange method under nonholonomic constraints. The inverse dynamics is calculated in three different paths based on this model, and the results demonstrate that torques of hip pitching joints are inversely proportional to the height of robot. The relative error of calculated torques is less than 2% compared with that of ADAMS simulation, by which the validity of dynamic model is verified, Moreover, the relative horizontal motion between fore/hind wheels and body is produced when the height is changed, and thus the accurate slip ratio can not be obtained by the traditional equation. The improved slip ratio equations with the parameter of the vertical velocity of body are introduced for fore wheels and hind wheels respectively. Numerical simulations of slip ratios are conducted to reveal the effect of varied height on slip ratios of different wheels. The result shows that the slip ratios of fore/hind wheels become larger/smaller respectively as the height increases, and as the height is reduced, the reverse applies. The proposed research of dynamic model and slip ratio based on the robot height provides the effective method to analyze the dynamics of WMRs with varying height.

Parametric Study on the Effect of Aspect Ratio of Selected Cooling Hole Geometries on the Mechanical Response of an Automobile Aluminium Alloy Wheel

Aluminium alloy wheels are increasingly popular for their light weight and good thermal conductivity. Cooling Holes (CH) are introduced to reduce their weight without compromising structural integrity. Literature is sparse on the effect of aspect ratio (AR) of CHs on wheels. This, work, therefore, attempts to undertake a parametric study of the effect of aspect ratio (AR) on the mechanical response of an aluminium alloy wheel with triangular, quadrilateral and oval-shaped CHs. Three-dimensional wheel models (6JX14H2ET42) with triangular, quadrilateral and oval shaped CH (each with CH area of 2229 mm2) were generated, discretized, and analyzed by FEM using Creo Elements/Pro 5.0 to determine the mechanical response at the inboard bead seat at different ARs of 1, 0.5, 0.33 and 0.25, each for quadrilateral-CH and oval-CH, at a static Radial Load of 4750 N and Inflation Pressures of 0.3 and 0.15 MPa, respectively. The study shows that the magnitude of stress and displacement is affected by shape and AR of CH. From the results, it could be established that oval-shaped-CH wheel at AR of 0.5 offers greater prospect in wheel design as it was least stressed and deformed and, that the CH combination with highest integrity was the oval-CH and quadrilateral-CH at AR of 0.5.

Research of Magnesium Alloy Wheel Vibration Performance Based on Finite Element Method

As the automotive industry is increasingly demanding on energy saving and environmental protection,people are taking more attention on the lightweight design and comfort of automobiles.Wheel vibration is one of the most important parts of a vehicle performance.The dynamic characteristics of the vehicle are determined by the modal parameters of the vehicle system.The wheel also has a great influence on the vibration.Based on finite element method,we analyze wheel vibration performance.This research studies the effect of different damping properties on wheel frequency.By comparing of acceleration and speed of the wheel,we can improve the vibration performance of the vehicle.

A Research on Thrust Ratio of Front Wheels to Rear Wheels of Front Wheel Assist Tractor

Based on dynamic analysis of Front wheel Assist (FWA) Tractor,a method for calculating the thrust Ratio of front wheels to rear wheels is described in this paper,a mathematical model is established and verified,The article introduces the definition of thrust ratio of front wheels to rear wheels,which is an important parameter affecting the tractive performance of FWA tractor.

磨粒有序化砂轮排布参数对磨削筋条表面影响

为了使用磨粒有序化砂轮磨削出减阻筋条表面,首先,分析了磨粒有序化砂轮的排布参数与磨削减阻筋条表面深宽比的关系,设计出了磨粒有序化砂轮的几何和数学模型,并且建立了磨粒运动轨迹方程;然后,建立了减阻筋条深宽比与有序化砂轮排布参数之间的数学方程;最后,由仿真结果得到了砂轮排布参数对减阻筋条表面形貌与深宽比的影响规律。研究结果表明,在磨粒有序化砂轮的排布参数中,倾斜角度、磨粒间距和磨削深度的改变会直接对减阻筋条尺寸有影响并且对其深宽比的大小起到决定性作用。

四驱电动汽车变附着路面行驶操稳性控制研究

针对四轮驱动电动汽车行驶时路面峰值附着系数和附着利用率变化的问题,提出利用直接横摆力矩控制提高操纵稳定性的控制策略。该策略采用分层控制,上层控制器负责目标车速的追踪、滑移率调整力矩的计算、以及根据行驶危险程度实现对质心侧偏角和横摆角速度的协调控制,下层控制器包括以轮胎利用率最优为目标的分配算法及集成滑移率控制的分配算法,根据滑移率大小实时切换。Carsim-Simulink联合仿真结果表明,在对开路面行驶时,相比于转矩平均分配控制策略,该控制策略能够使车辆具有良好操稳性的同时保持各车轮处于最佳滑移率区间内,有效改善了车辆性能。

微晶陶瓷磨料砂轮磨削轴承钢实验探讨

特定的生产或试验条件下不同的磨料制作的砂轮具有不同的性能表现,为了考察市售微晶陶瓷磨料(CA)的适用性,选取四种不同品牌相近规格的CA磨料制作新型CA磨料砂轮进行磨削试验,以等效组分等量替代法采用相同的砂结比、成型、干燥等工艺技术条件,制成砂轮样品并分别编号为1^(#)~4^(#),对轴承钢工件进行磨削试验,比对磨削比、磨削功率的变化以及磨削后工件表面质量、砂轮表面形貌特征,了解该工艺技术条件下不同CA磨料制得的低温陶瓷结合剂砂轮的性能.结果表明,1^(#)和2^(#)磨料制作的砂轮综合磨削性能较好,4^(#)无明显优势,但磨削后工件表面光洁度较好,3^(#)砂轮表现不佳.

基于能量损耗比的驱动轮减振结构ANSYS一阶优化分析

针对应用于履带式工程车辆驱动轮的“阻尼层+过渡层”复合减振结构,通过建立能量损耗比模型,分析了其应力、应变特性。此外,在四层管状过渡阻尼减振结构厚度值恒定的情况下,基于ANSYS一阶优化方法,探究并优化了不同设计变量(基层、约束层、过渡层、阻尼层的厚度值和过渡层、阻尼层材料的弹性模量以及损耗因子)对结构优化目标函数能量损耗比的影响规律。研究结果表明,相比于优化前结构的能耗比参数,优化后结构的耗能值增加了56.8%,增长值为0.1654。所提分析方法可为中国高端大型履带式工程车辆的减振设计以及绿色化提供参考,同时对于遗传算法优化在各种车辆结构设计中的运用具有一定的借鉴价值。

打水轮位置在高湿环境下对移动空调性能的影响

移动空调依靠其灵活度高、局部降温能力强的优点,具有广阔的市场前景。为解决其在高湿环境下水满停机的问题,在移动空调冷凝器底部安置了打水轮。研究了打水轮位置在高湿工况下对移动空调整体性能的影响。结果发现:打水轮的安装位置对移动空调的性能有较大的影响,在四种不同位置的打水轮中,越能够将冷凝水打入冷凝器高温区域的打水轮效果越好,移动空调EER越高,冷凝水排除能力最强;随着打水轮的打水效果增强,移动空调的蒸发压力和冷凝压力都随之下降,而制冷量增加。由于其中冷凝压力下降幅度更剧烈,移动空调输入功率减少;同时随着室内空气相对湿度升高,移动空调显热比降低。

透水沥青混合料车辙试验离散元仿真

为分析车辙对透水沥青混合料内部空隙的影响,以透水沥青混合料PAC-13为研究对象,进行按级配上限及级配中值成型的沥青混合料试件的车辙试验,得到轮迹处的车辙及空隙率的变化规律;基于车辙试验数据,采用离散元软件PFC 2D,从细观角度建立透水沥青混合料离散元颗粒仿真模型,分析透水沥青混合料车辙产生过程中内部空隙及颗粒间接触力的变化规律,并考虑试件厚度对空隙率的影响。研究结果表明:车辆荷载作用处沥青混合料空隙率变化比其他部位大;在相同荷载作用下,级配中值沥青混合料的空隙率变化比级配上限沥青混合料小;级配上限沥青混合料的模型厚度增大,空隙率变化减小,颗粒间接触力向下传递的趋势降低,且车辙板底部所受颗粒间接触力较小;厚8 cm的车辙板在荷载位置的空隙率变化较大,且随距表面距离的增大,空隙率变化幅度减小。

风载作用下高速列车曲线通过性能研究

在风载和曲线欠超高叠加的不利工况下,高速列车的运行安全性表现出复杂的变化规律,因此需要针对风载作用下高速列车的曲线通过安全性进行深入研究。采用空气动力学和车辆动力学相结合的分析方法,考虑车速和风速变化、实际轮轨匹配及线路激励情况,建立瞬态风载模型、横风作用下高速列车空气动力学模型及车辆动力学模型;对高速列车在不同车速和风速作用下的气动载荷变化规律进行分析,并对其以不同速度通过不同欠超高曲线线路时的脱轨系数、轮重减载率和轮轴横向力等车辆关键动力学参数的变化规律进行分析,研究风载和曲线欠超高对高速列车脱轨和倾覆的影响。结果表明:风速变化引起的侧向力系数变化幅度大于车速;在风载和曲线欠超高叠加的不利工况下,除轮重减载率安全裕量明显降低外,轮轴横向力的安全裕量也降低,且车辆关键悬挂部件工作状态恶化,其中二系横向止档的位移迅速增大且工作状态接近压并,左右两侧空气弹簧压力差也迅速增大,车辆动力学性能的安全裕量明显下降。

金刚石砂轮的磨削整形法研究

为研究金刚石砂轮修整的工艺,采用绿碳化硅砂轮对金刚石砂轮进行磨削整形法修整。通过改变修整量、修整速比、切削进给量、工作台速度得出修整参数对砂轮磨削性能的影响规律。研究结果表明,工件表面粗糙度随着修整量增加而增大,修整量增加到一定次数时粗糙度变化不大;修整速比增大时,工件表面粗糙度值增大;切削进给量增大时,工件磨削表面粗糙度增大;工作台速度增大时,工件表面粗糙度增大。所得结论为绿碳化硅砂轮修整金刚石砂轮的工艺参数选取提供了切实有效的参考价值。

A Fuzzy-based Sliding Mode Control Approach for Acceleration Slip Regulation of Battery Electric Vehicle

Due to quick response and large quantity of electric motor torque,the traction wheels of battery electric vehicle are easy to slip during the initial phase of starting.In this paper,a sliding mode control approach of acceleration slip regulation is designed to prevent the slip of the traction wheels.The wheel slip ratio is used as the state variable for the formulation of system dynamics model.The fuzzy algorithm is utilized to adjust the switch function of sliding mode controller.After stability and robustness analysis,the sliding mode control law is transferred into C code and downloaded into vehicle control unit,which is validated under wet and dry road conditions.The experimental results with a small overshoot and a quick response during starting indicate that the sliding mode controller has good control efect on the slip ratio regulation.This article proposes an acceleration slip regulation method that improves the safety during acceleration for battery electric vehicle.

Unsteady-State Grinding Technology (II) Experimental Studies of Grinding Forces and Force Ratio

As is known to all, grinding force is one of the most important parameters to evaluate the whole process of grinding. Generally, the grinding force is resolved to three component forces, namely, normal grinding force F n, tangential grinding force F t and a component force acting along the direction of longitudinal feed which is usually neglected because of insignificance. The normal grinding force F n has influence upon surface deformation and roughness of workpiece, while the tangential grinding force F t mainly affect power consumption and service life of grinding wheel. In order to study deep into the process of the unsteady state grinding, we set up a measurement system to monitor the change of grinding force during the course of grinding and try to find some difference in the change of grinding force between the steady state grinding and unsteady state grinding. In the test, the normal and tangential grinding forces, F n and F t were measured by using a set of equipments including sensor, amplifier, oscilloscope and computer monitor. From the results, we can conclude that: 1) In the unsteady state grinding process, the values of the grinding forces are much lower than those of the steady state grinding process and the grinding force ratio showed a nonlinear fluctuation. 2) The tendency of the grinding forces in the process of the unsteady state grinding proved the existence of the cutting and micro-cutting actions. 3) Because the grinding force signals of the unsteady state grinding are much weaker than those of the steady state grinding, to obtain accurate value of the grinding forces, wave filtering is needed to be done. The whole process to filter the perturbation wave can be separated into three steps in order, changing the grinding force signals from analog signals into digital signals, FFT (fast Fourier transform) treatment to the digital signals, and IFFT(inversion fast Fourier transform) treatment to the digital signals after spectrum limitation.

Analysis of torque transmitting behavior and wheel slip prevention control during regenerative braking for high speed EMU trains

The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recovery.There remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact conditions.This research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion stability.Then,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control.The proposed methodology achieves the optimal braking performancewithoutthewheel-railcontactinformation.Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.

Grinding Characteristics Of Directionally Aligned SiC Whisker Wheel - Comparison With A12O3 Fiber Wheel

A unique SiC whisker wheel was invented,in which the whiskers were aligned normally to the grinding wheel surface.In this paper,grindabilities of the SiC whisker wheel are investigated and compared with those of other wheels of SiC grains,Al2O3 grains,as well as Al2O3 long and short fibres which were also aligned normally to the grinding wheel surface,respectively.The main research contents concern grinding characteristics of a directionally aligned SiC whisker wheel such as material-removal volume,wheel-wear rates,integrity of the ground surfaces,grinding ratios and grinding efficiency.Furthermore,grinding wheels of whiskers and fibres have a common disadvantage:they tend to load easily.The authors have proposed a simple method of loading-free grinding to overcome this propensity and investigate some related grinding characteristics under loading-free grinding conditions.

Study on Running Performance of Flexible Wheels for Lunar Rovers： Relation between Stress Distribution of Flexible Wheel and Running Performance

On lunar exploration missions, the rovers which can move and explore directly are considered by various agency like NASA （National Aeronautics and Space Administration）, JAXA （Japan Aerospace Exploration Agency）, ESA （European Space Agency）. Lunar rovers are required to move on rough terrains such as craters and rear cliffs where it is scientifically very important to explore. However, there is a problem that the rovers have possibility of stack because of the lunar surface is covered with loose soil named Regolith. Therefore, this paper investigates a mechanism of kinetic behavior between the wheels of the exploration rovers and loose soil. And then, this paper proposed a flexible wheel to solve like that problems. The flexible wheel has the surface which can be changed flexibly toward rough terrain. Running experiments on loose soil which imitated regolith were carried out to observe the traversability of the flexible wheel using slip ratio. Traversality of flexible wheel was better than the circular rigid wheel. The authors believe that stress distribution is important. The stress distribution of the flexible wheels is horizontally long and stress value is small. However, the stress distribution can be changed by loaded more weight. Therefore, the relationship between the stress and the running performance was considered using this differential stress distribution. In experiments, the authors used the flexible wheel with simple structure （3 limbs）. From these considerations, the relationship between the stress of the flexible wheel and the running performance was described.

基于多目标优化的砂轮杆结构轻量化设计研究

为了得到大长径比砂轮杆合理的结构及支撑方式,保证砂轮杆满足刚度要求,通过建立大深径比孔磨削用砂轮杆的三维参数化模型,用有限元方法分析了砂轮杆的静力变形和约束模态,采用最佳空间填充试验设计(optimal space-filling design)方法构建了砂轮杆各设计变量与优化目标的二阶响应面模型,采用NSGA-Ⅱ算法对砂轮杆进行了多目标优化。经过轻量化优化设计及仿真比较,得到一种大长径比砂轮杆及支撑的合理化结构,轻量化率达到10.3%。分析结果表明:砂轮杆质量、刚度及模态均满足工程要求。

磨粒有序化砂轮滚磨外圆筋条表面的研究

为了在外圆零件表面加工出用于表面减阻的结构化筋条,基于滚齿加工原理,提出利用磨粒有序化(工程化)砂轮滚磨外圆筋条表面的加工方法。根据筋条表面的特征,对外圆筋条表面进行设计;利用筋条表面的特征参数设计了磨粒有序化砂轮,并给出实现滚磨外圆筋条表面的条件;对滚磨过程进行仿真分析,获得了磨削相关参数对筋条表面形貌的影响规律。研究结果表明:磨粒有序化砂轮能够实现对外圆筋条表面的磨削,筋条表面的主要特征为深宽比,选用合适的磨削用量和排布参数可以满足减阻功能深宽比筋条表面的滚磨。