考虑停车距离的载货汽车制动危险状态辨识

通过对紧急制动下的停车距离计算,可间接预测出车辆的安全行驶间距,从而实现车辆防追尾避撞。以载货汽车为研究对象,提出了停车距离模型参数计算方法,从制动距离影响因素着手,通过对驾驶员制动反应时间、制动管路压力、制动蹄片温度、路面附着系数等停车距离的影响参数分析,建立了停车距离分析模型;通过空挡怠速、滑行试验来标定了制动距离计算模型中车辆内外阻力参数;最后综合考虑制动距离、驾驶员反应距离和路面情况,建立在人-车-路闭环系统下多参数融合的载货汽车停车距离模型,提出了载货汽车制动危险状态辨识方法;在不同工况下对停车距离进行仿真试验及实车道路试验,通过对仿真结果和试验结果的分析,验证了停车距离计算模型的可行性,为车辆运行安全状态预警技术的研究提供理论依据和技术支持。     

一种附着系数实时可调的汽车制动模拟试验台 设计、分析与实验研究

为了实现车辆制动模拟试验中附着系数的准确模拟和实时可调,设计了一种汽车制动模拟试验台,通过控制磁粉离合器励磁电流,实时模拟不同路面附着系数;搭建了基于路面识别的单轮车辆制动系统仿真模型,进行了单一路面和跃变路面下的制动仿真;研制了车辆制动模拟实验系统,开展了单一路面下汽车制动模拟实验和跃变路面下附着系数跟踪控制实验。研究结果表明,在湿沥青路面上以120 km/h初速度制动时,相比于基于固定目标滑移率,基于路面识别的最佳滑移率下的制动距离缩短了3.1%,且在低附着路面下更为明显;单一路面下制动时车速和轮速的实验值与仿真值基本吻合;跃变路面下附着系数最大跟踪误差仅为6.2%,跟踪控制效果良好。     

对开路面弯道制动的控制方法

运用多体动力学软件SIMPACK建立汽车模型,着重研究了汽车在外侧附着系数低、内侧附着系数高路面上弯道制动的情况.通过仿真,在分析轮胎受力的基础上,提出了一种基于转角预测前馈的动态调节内侧车轮最佳滑移率的控制方法,并在Matlab中搭建了模糊控制系统进行联合仿真.结果显示,所提出的控制策略可以改善车辆在这种极限工况下的侧偏位移和横摆角速度,减轻了驾驶员的操纵心理负担,并且车辆的制动距离基本保持不变,保证了制动效能,提高了车辆侧向稳定性.     

利用Matlab/Simulink的轮式汽车制动过程仿真分析

以在坡度为α的坡道上制动的汽车为研究对象,结合整车和前、后车轮的旋转运动微分方程,建立轮式汽车制动的力学模型,利用工程仿真软件Matlab中Simulink模块,建立轮式汽车制动的仿真模型,将某车型的参数代入仿真软件进行数值模拟仿真。分析轮式汽车制动时滑移率的影响规律得出:在相同的道路附着系数条件下,车速越高滑移率越大,制动距离越长;设计汽车时适当地增加汽车制动器的制动力,增大速率,可以控制滑移率的增长速度。     

基于逻辑门限值的汽车ABS控制策略与试验研究

研究了一种考虑汽车前、后轴轴荷不同和制动时轴荷转移的汽车防抱死制动系统(ABS)逻辑门限值控制策略。该控制策略以车轮滑移率为主要控制目标,以车轮角加速度为辅助控制目标,通过仿真试验确定前、后车轮不同的最佳滑移率范围,采用前轴制动压力高选和后轴制动压力低选控制方式,提高汽车在低附着系数、对开路面的制动性能。编写控制策略程序,应用驾驶模拟器硬件在环制动试验台进行低附着系数、对开路面紧急制动工况验证。试验结果表明:控制策略具有良好的实时性,缩短了制动距离,提高了汽车制动时的方向稳定性。     

基于Matlab的汽车制动力分配比优化设计

对某中型两轴货车进行制动时的受力分析,建立计算两轴汽车前后轴制动利用附着系数φ_rφ_f的数学模型。以φ_rφ_f曲线与φ=z直线最接近为优化目标建立多目标优化评价函数,以ECE法规为约束条件,以制动力分配比β为设计变量。运用Matlab优化工具箱进行解算,求出最优点β;运用Matlab计算并输出优化后的φ_rφ_f曲线与φ=z直线图;β曲线与I曲线图;运用Matlab对制动距离仿真计算,得出采用最优点β的汽车制动性能更好。该优化设计方法对汽车的制动系统设计有一定的指导作用。     

计算机辅助系统（CAT）在汽车ABS部件试验台上的应用

1 概述 ABS是汽车在紧急刹车时防止车轮抱死的制动装置,它可在汽车制动过程中,对车轮的运动状态进行迅速、准确而又有效的控制,使车轮尽可能地处于最佳制动状况。在汽车制动时,ABS可使车轮的纵向处于附着系数的峰值,同时使其侧向也保持着较高的附着系数,从而使汽车具有良好的防侧滑能力和最短的制动距离,以提高车辆行驶的安全性。汽车ABS主要分为液压制动系统和气压制动系统两种类型。液压制动系统具有体积小,     

基于MatLab/Simulink的ABS控制策略实用性研究

针对汽车制动防抱系统ABS的常用控制策略进行分析,提出了基于路面附着系数的控制方法,并在MatLab/Simulink中对其进行模拟仿真研究,同时对ABS制动系统的仿真结果进行对比分析,得出了基于路面附着系数的控制策略是简单、实用、控制效果较好的ABS控制方法,也是一种值得推广的方法。     

基于路面识别的汽车ABS模糊控制仿真

汽车防抱制动系统（ABS）通过在制动过程中自动控制车轮的制动力矩,从而防止了车轮抱死。为了进一步提高汽车ABS的性能,在对汽车制动过程进行动力学分析的基础上,建立了ABS系统的模糊控制模型;采用路面识别方法,对变附着系数路面进行了ABS制动模拟仿真。仿真结果表明,基于路面识别的模糊控制防抱制动系统能取得较好的控制效果,并具有一定的自适应能力。     

考虑路面附着条件影响的电动汽车制动力变比值优化分配算法研究

制动力分配算法是电动汽车再生制动研究的基础,为了能够在不同路面制动时均能获得较好的制动效果,设计了 一种考虑路面附着条件影响的电动汽车制动力变比值优化分配算法.利用汽车动力学方程进行滑移率和利用附着系数估算,实现对路面类型的辨识.然后根据辨识的路面类型选择对应的制动力变比值分配系数,进行算法实现.最后通过与dSPACE软件联合仿真验证了算法有效性,与未考虑路面附着条件的算法相比,新算法制动所需时间至少减少了 6.6％.     

石墨种类对铜基粉末冶金摩擦材料性能的影响

采用柔性石墨、造粒石墨和鳞片石墨分别制备粉末冶金烧结摩擦材料，研究不同种类片状石墨对摩擦材料摩擦磨损性能的影响。结果表明：不同种类石墨制备的摩擦材料的密度和力学强度差异，将影响材料基体在制动过程中的组织形态，使摩擦界面呈现不同的磨损形式，其中柔性石墨摩擦材料的主要磨损机制为氧化磨损，造粒石墨摩擦材料的主要磨损机制为犁削磨损和磨粒磨损，鳞片石墨摩擦材料的主要磨损机制为犁削磨损和黏着磨损；造粒石墨制备的摩擦材料在不同速度下制动和重复单次制动时的摩擦因数波动值较小，摩擦因数稳定性好，且具有适中的磨耗量，综合摩擦磨损性能最佳。     

带式输送机树脂基摩擦片干式制动条件下摩擦学行为

采用热压烧结技术制备桐油改性酚醛树脂和腰果壳油改性酚醛树脂基摩擦片,通过CFT环块摩擦磨损试验机研究其在不同的制动速度、制动正压力下以及在瞬时制动时的摩擦因数以及磨损率的变化规律,采用扫描电镜(SEM)对试样摩擦后的表面形貌进行观察分析。结果表明,2种树脂基摩擦片摩擦因数以及磨损率变化规律具有一致性:摩擦因数均随着制动正压力与制动速度的增加而减小;磨损率随着制动速度的增加而减小,随着制动正压力的增加而增加。以桐油改性酚醛树脂为基体,碳纤维为增强纤维的摩擦片在瞬时制动时具有较稳定的摩擦因数,而且在不同制动正压力与制动速度下磨损率较低。     

制动条件下石墨对铜基摩擦材料瞬时摩擦性能的影响

为研究石墨对铜基摩擦材料瞬时摩擦性能的影响,采用粉末冶金技术制备铜-SiO2和铜-石墨-SiO2烧结材料,通过干摩擦惯性试验,在始末速度不同的制动区间,测试材料的瞬时摩擦因数、瞬时磨损率,并观察摩擦表面形貌的变化。结果表明:在高速度制动区间,石墨的存在使得铜基摩擦材料摩擦因数的稳定性明显提高,磨损率降低,原因在于铜-石墨-SiO2材料剥落石墨颗粒的分隔和保护作用,减弱冲击波动,从而提高瞬时摩擦因数稳定性并降低磨损;但较低制动速度时,石墨的存在反而提高了磨损率,原因在于摩擦层对颗粒的包裹度和基体强度降低。     

摩擦副组合对摩擦磨损性能的影响

在1：1惯性力矩制动试验台上研究了两种不同石墨形态的铸铁制动盘与两种混杂纤维增强的酚醛基制动闸片配副时的摩擦磨损性能。结果表明，对于某一配方的制动闸片，使用灰口铸铁盘的摩擦副具有较高的摩擦系数，但制动盘表面温度较高，闸片磨损量较大；对于某一种制动盘，使用B配方制动闸片时，制动盘表面的温度较高，但闸片的磨损量较小；在所有四种组合中，B配方制动闸片与灰口铸铁盘配副的瞬时摩擦系数能够完全满足有关技术要求。     

Objective Characterization on the Dynamic Friction Coefficient of Disc Brake

As the most significant parameter for evaluating the friction state of disc brakes, the friction coefficient was characterized solely by its average and stability coefficient, which cannot accurately represent its dynamic variation characteristics during braking. In this article, a new characterization parameter set consisting of an overall and a partial characteristic parameters subset was established to characterize the dynamic variation in friction coefficient of disc brakes. Moreover, the influence of braking conditions on these new parameter sets was studied by tribological experiments. Several simulated braking experiments were carried out and the dynamic variation rules were observed. Secondly, a new characterization parameter set including eight parameters (mean value, stability coefficient, energy coefficient, end point of rapid rising, starting and end points of the up-tail, trend coefficient, and catastrophe coefficient) was established. Finally, the influence of initial braking velocity and braking pressure on these parameters and its mechanism was analyzed by braking experiments. It is concluded that the parameter set established in this article can be used to characterize the dynamic variation rules of the friction coefficient of disc brakes more objectively and comprehensively.     

Tribological Properties of Short Fiber C/SiC Brake Materials and 30CrSiMoVA Mate

In this study, the short fiber C/SiC brake materials were prepared by a combined process of the fibers dipped with resin, chopping, warm pressing, pyrolyzing, and the liquid silicon infiltration process. The tribological properties of short fiber C/SiC brake materials and 30CrSiMoVA mate were investigated. The results indicated that the average friction coefficient decreased with the increase of braking speed (initial braking speed), and the friction coefficient tended to be constant when the braking speed was higher than 20 m/s. The braking was stable when the braking speed was 5 m/s, and the braking was unstable when the braking speed was higher than 10 m/s. The wear rate of the C/SiC increased with the increase of braking speed when the braking speed was less than 10 m/s, decreased with the increase of braking speed when the braking speed was less than 20 m/s, and then increased afterward with the increase of braking speed. When the braking speed was higher than 20 m/s, an oxidation-abrasion mechanism could occur. With braking speed increasing, the number of the ribbon debris increased, and the ribbon debris got long and thick, and the number of big granular debris increased.     

汽车风冷盘式制动器摩擦学特性试验研究

为得出制动参数对汽车风冷盘式制动器摩擦学特性的影响机理,考虑空气流动和车辆惯性因素,基于噪声、振动与声振粗糙度（NVH,Noise Vibration and Harshness）台架试验机精确模拟制动工况,研究摩擦副表面在不同制动压力（1.0~3.0 MPa）、行驶速度（5~30 m/s）以及温度（100~350  ℃）条件下平均摩擦系数与摩擦稳定系数的变化规律。试验结果表明：制动压力增大时,摩擦力矩并非一定随之增大,尤其是较高行驶速度条件;当制动盘表面温度超过300 ℃时,低速条件下的平均摩擦系数和摩擦稳定系数急剧减小。     

Estimation of Road Friction Coefficient in Different Road Conditions Based on Vehicle Braking Dynamics

The accurate estimation of road friction coefficient in the active safety control system has become increasingly prominent. Most previous studies on road friction estimation have only used vehicle longitudinal or lateral dynamics and often ignored the load transfer, which tends to cause inaccurate of the actual road friction coefficient. A novel method considering load transfer of front and rear axles is proposed to estimate road friction coefficient based on braking dynamic model of two-wheeled vehicle. Sliding mode control technique is used to build the ideal braking torque controller, which control target is to control the actual wheel slip ratio of front and rear wheels tracking the ideal wheel slip ratio. In order to eliminate the chattering problem of the sliding mode controller, integral switching surface is used to design the sliding mode surface. A second order linear extended state observer is designed to observe road friction coefficient based on wheel speed and braking torque of front and rear wheels.The proposed road friction coefficient estimation schemes are evaluated by simulation in ADAMS/Car. The results show that the estimated values can well agree with the actual values in different road conditions. The observer can estimate road friction coefficient exactly in real-time andresist external disturbance. The proposed research provides a novel method to estimate road friction coefficient with strong robustness and more accurate.     

电液混合动力轨道车的复合制动特性

针对蓄电池轨道工程车制动性能的不足设计了一套液压再生制动系统,在车辆原底架结构基础上与原制动系统共同作用形成了一套复合制动系统。为探究复合制动系统制动、能量回收和缓速的有效性,对电液轨道车下坡纯摩擦制动的能力进行了理论计算,并利用AMESim和MATLAB/Simulink建立的液压系统模型对复合制动过程进行仿真运算。仿真结果表明:复合制动方式能大大提高下坡制动性能同时回收制动能量;在高速工况下制动时,马达变排量控制方式能够提高液压再生制动扭矩,从而减少制动距离和磨损。复合制动系统能有效地调节轨道车下坡速度,保证车辆安全性。     

Fundamental studies on the brake friction of resin-based friction materials

The effects of various factors on brake friction were studied on the braking of a cast iron disk by small brake specimens made of resin, resin-asbestos composites and three-component composites. When the disk temperature rises, the resin-based composites containing asbestos and high melting point additive exhibit considerably lower friction during braking following high friction in the initial braking stage. The initial high friction is attributed to the deformation resistance of the resin in the composite. Low friction is attributed to the lubricating action of resin decomposition products in the neighbourhood of the filler raised to a high temperature by frictional heating. Increase of friction toward the end of braking is mainly due to increase of the true contact area as the frictional speed decreases. Variation of the average frictional coefficient during braking with load and the initial speed is generally small. There is no correlation between the mechanical properties and the brake frictional behaviour of resin-based composites.