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毕业设计（论文）档案袋内组成部分一、毕业设计（论文）册内容与装订顺序：l 封面：论文题目不得超过20个字，要简练、准确，可分为两行。l 内容1、毕业设计（论文）任务书；任务书由指导教师填写，经所在系部审查签字后生效。2、毕业设计（论文）开题报告；3、毕业设计（论文）学生申请答辩表与指导教师毕业设计（论文）评审表；4、毕业设计（论文）评阅人评审表；5、毕业设计（论文）答辩表；6、毕业设计（论文）答辩记录表；7、毕业设计（论文）成绩评定总表；8、论文：(1)中文题目与作者；(2)英文题目与作者；(3)中文内容摘要和关键词；(4)英文内容摘要和关键词；(5)目录；(6)正文；(7)致谢；(8)参考文献及引用资料目录；(9)附录；(10)实验数据表、有关图纸(大于3#图幅时单独装订)；l 封底。二、英文资料翻译册内容与装订顺序：l 封面；l 内容 1、英文原文； 2、中文翻译； 3、阅读书目；l 封底。1毕业设计（论文）任务书系 部机械工程系指导教师王海涛职 称副教授学生姓名郭嘉文专业班级05机制本（2）学 号0515011202设计题目关节式自动上下料机械手设计（PLC控制）设计内容目标和要求（设计内容目标和要求、设计进度等）内容:了解关节式机械手的基本结构和设计方法，学习PLC控制的有关内容，利用PLC的梯形图编写程序，掌握液压系统的设计，学会查找资料，利用资料解决问题。要求：1 完成关节式机械手的整体装配图；2 完成液压系统原理图；3 完成PLC外部接线图；4 完成PLC梯形图编程，运行程序通过；5 完成相关英文翻译一篇；6 撰写设计说明书，要求字迹工整。指导教师签名：年 月 日系 部审 核 此表由指导教师填写 由所在系部审核2-1毕业设计（论文）学生开题报告课题名称关节式自动上下料机械手设计（PLC控制）课题来源生产实践课题类型AX指导教师王海涛（副教授）学生姓名郭嘉文学 号0515011202专业班级05机制2班本课题的研究现状、研究目的及意义工业机械手是人类创造的一种机器,更是人类创造的一项伟大奇迹,其研究、开发和设计是从二十世纪中叶开始的.我国的工业机械手是从80年代七五科技攻关开始起步,在国家的支持下,通过七五,八五科技攻关,目前已经基本掌握了机械手操作机的设计制造技术,控制系统硬件和软件设计技术,运动学和轨迹规划技术,生产了部分机器人关键元器件，开发出喷漆，孤焊，点焊，装配，搬运等机器人，其中有130多台喷漆机器人在二十余家企业的近30条自动喷漆生产线（站）上获得规模应用，孤焊机器人已经应用在汽车制造厂的焊装线上。但总的看来，我国的工业机械手技术及其工程应用的水平和国外比还有一定距离。如：可靠性低于国外产品，机械手应用工程起步较晚，应用领域窄，生产线系统技术与国外比有差距。影响我国机械手发展的关键平台因素就是其软件，硬件和机械结构。目前工业机械手仍大量应用在制造业，其中汽车工业占第一位（占28.9%），电器制造业第二位（占16.4%），化工第三位（占11.7%）。发达国家汽车行业机械手应用占总保有量百分比为23.4%53%，年产每万辆汽车所拥有的机械手数为（包括整车和零部件）：日本88.0台，德国64.0台，法国32.2台，英国26.9台，美国33.8台，意大利48.0台世界工业机械手的数目虽然每年在递增，但市场是波浪式向前发展的。在新世纪的曙光下人们追求更舒适的工作条件，恶劣危险的劳动环境都需要用机器人代替人工。随着机器人应用的深化和渗透，工业机械手在汽车行业中还在不断开辟着新用途。机械手的发展也已经由最初的液压，气压控制开始向人工智能化转变，并且随着电子技术的发展和科技的不断进步，这项技术将日益完善。上料机械手与卸料机械手相比，其中上料机械手中的移动式搬运上料机械手适用于各种棒料，工件的自动搬运及上下料工作。例如铝型材挤压成型铝棒料的搬运及高温材料的自动上料作业，最大抓取棒料直径达180mm，最大抓握重量可达30公斤，最大行走距离为1200mm。根据作业要求及载荷情况，机械手各关节运动速度可调。移动式搬运上料机械手主要由手爪，小臂，大臂，手臂回转机构，小车行走机构，液压泵站电器控制系统组成，同时具有高温棒料启动疏料装置及用于安全防护用的光电保护系统。整个机械手及液压系统均集中设置在行走小车上，结构紧凑。电气控制系统采用OMRON可编程控制器，各种作业的实现可以通过编程实现。2-2本课题的研究内容工业机器人系统由三大部分六个子系统组成。 三大部分是：机械部分，传感部分，控制部分。六个子系统是：驱动系统，机械结构系统，感受系统，机器人环境交互系统，人机交互系统，控制系等等。该机械手为机床上下料机械手，圆柱体工件约30千克，要求下料之后马上上料,一次完成上下料两步骤。动作顺序：加工工位等候-机械手臂下降-手爪收拢夹紧已加工好的工件-手臂上升-手臂回转至卸料工位-手臂下降-（手腕回转）手爪松开工件-手臂上升-回转至加工工位-手臂下降-手爪松开工件-手臂上升至等待工位等候。机械手的动作全部采用液压驱动，PLC控制。一、机械手驱动系统的选择：设计机械手时,选择哪一类驱动系统,要根据机械手的用途,作业要求,机械手的性能规范,控制功能,维护的复杂程度,运行的功耗,性能与价格比以及现有条件等综合因素加以考虑.在注意各类驱动系统特点的基础上,综合上述各因素,充分论证其合理性,可行性,经济性以及可靠性后进行最终的选择。按动力源的不同机器人又分为:电气驱动、液压驱动、气动驱动三种。液压驱动的特点是功率大，气动驱动存在冲击力大，精度难以控制等缺点，而电气驱动具有控制方便、J性能好等优点。（综合考虑本机械手采用液压驱动）二、机械手结构设计：机械结构是物料抓取机械手最终的执行机构，是机器人赖以实现各种运动的实体，机械结构的布局、类型、传动方式以及驱动系统的设计直接关系着机器人的工作性能。机械结构按坐标形式主要有直角坐标型、球坐标型、圆柱坐标型、SCARA型和关节型等。直角坐标型机器人操作臂的优点是结构简单、刚度高，三个关节的运动相互独立，其间没有祸合，不影响末端手爪的姿态，不产生奇异状态，运动和控制都比较简单;缺点是占地面积大，动作范围小，操作灵活性差。球坐标机器人和圆柱坐标机器人占地面积小，工作空间较大，在空间中的定位也比较直观，但是它们的移动关节不容易防护，极坐标型机器人也存在移动关节不易防护的问题，它们多用于一些特殊的作业环境。SCARA型机器人的主要特点是结构轻便，响应快，最适用于在垂直方向完成零件的装配作业。关节型机器人操作臂的优点是结构紧凑，占地面积小，动作灵活，在作业空间内手臂的干涉最小，工作空间大;缺点是进行控制时计算量比较大，确定末端执行部件的位姿不直观。针对该上下料机械手，为了使它具有一定的操作灵活性和较好的使用性能，在结构设计上采用圆柱坐标型。整个机器人系统设计为四个自由度。 自由度的分布情况为：机身的升降和回转，手臂的伸缩，手腕的回转。三、手部的结构设计：手部就是与物件接触的部件。由于与物件接触的形式不同，可分为夹持式和吸附式手部。为了使机械手的通用性更强，把机械手的手部结构设计成可更换结构，当被夹持工件是圆柱刀柄时，使用夹持式手部;当该机械手做其他用途，被夹持工件是板料时，可使用气流负压式吸盘。（本课题工件为圆柱体工件，所以手部采用夹持式）2-3具体设计内容和要求一、设计内容：1了解关节式机械手的基本结构和设计方法2械手手部结构和运动机构的结构设计3机械手驱动系统的设计4学习PLC控制的有关内容，利用PLC的梯形图编写程序5绘制零件图和装配图，设计说明书一份二、设计要求：1完成关节式机械手的整体装配图2完成液压系统原理图3完成PLC外部接线图4完成PLC梯形图编程，运行程序通过5完成相关英文翻译一篇6撰写设计说明书，要求字迹工整本课题研究的实施方案、进度安排一、实施方案：通过生产厂房中的实际观察，以及利用网络或图书馆参阅有关关节式上下料机械手的资料，根据已有的标准规格和设计要求，在老师的指导下进行合理的设计。二、进度安排： 1）3月20-31日，主要进行毕业设计的准备工作，熟悉题目，收集资料，明确研究目的和任务； 2）4月1-25日，设计方案的确定，设计参数和尺寸的计算和分析； 3）4月26-5月15日，绘制机械手各部分图纸（手爪图、手腕图、手臂图和它们的组合图）； 4）5月16-5月27日，收尾完善，编写毕业设计论文，准备毕业设计答辩； 5）5月28-6月5日，毕业答辩。3毕业设计（论文）学生申请答辩表课 题 名 称关节式自动上下料机械手设计（PLC控制）指导教师（职称）王海涛（副教授）申 请 理 由申请毕业学生所在系部机械工程系专业班级05机制（本）2学号0515011202 学生签名： 日期：毕业设计（论文）指导教师评审表序号评分项目（理工科、管理类）评分项目(文科)满分评分1工作量外文翻译152文献阅读与外文翻译文献阅读与文献综述103技术水平与实际能力创新能力与学术水平254研究成果基础理论与专业知识论证能力255文字表达文字表达106学习态度与规范要求学习态度与规范要求15总 分100评语 （是否同意参加答辩） 指导教师签名： 另附毕业设计（论文）指导记录册 年 月 日4毕业设计（论文）评阅人评审表学生姓名郭嘉文专业班级05机制（本）2学号0515011202设计（论文）题目关节式自动上下料机械手设计（PLC控制）评阅人评阅人职称序号评分项目（理工科、管理类）评分项目(文科)满分评分1工作量外文翻译152文献阅读与外文翻译文献阅读与文献综述103技术水平与实际能力创新能力与学术水平254研究成果基础理论与专业知识论证能力255文字表达文字表达106学习态度与规范要求学习态度与规范要求15总 分100评语 评阅人签名： 年 月 日5毕业设计（论文）答辩表学生姓名郭嘉文专业班级05机制（本）2学号0515011202设计（论文）题目关节式自动上下料机械手设计（PLC控制）序号评审项目指 标满分评分1报告内容思路清新；语言表达准确，概念清楚，论点正确；实验方法科学，分析归纳合理；结论有应用价值。402报告过程准备工作充分,时间符合要求。103创 新对前人工作有改进或突破，或有独特见解。104答 辩回答问题有理论依据，基本概念清楚。主要问题回答准确，深入。40总 分100答辩组评语 答辩组组长（签字）： 年 月 日 答辩委员会意见答辩委员会负责人（签字）： 年 月 日6-1毕业设计（论文）答辩记录表学生姓名郭嘉文专业班级05机制（本）2学号0515011202设计（论文）题目关节式自动上下料机械手设计（PLC控制）答辩时间答辩地点答辩委员会名单问题1提问人： 问题：回答（要点）：问题2提问人： 问题：回答（要点）：问题3提问人： 问题：回答（要点）：记录人签名问题4提问人： 问题：回答（要点）：问题5提问人： 问题：回答（要点）：问题6提问人： 问题：回答（要点）：问题7提问人： 问题：回答（要点）：问题8提问人： 问题：回答（要点）：记录人签名6-27毕业设计（论文）成绩评定总表学生姓名： 郭 嘉 文 专业班级： 05机制（本）2 毕业设计（论文）题目：关节式自动上下料机械手设计（PLC控制）成绩类别成绩评定指导教师评定成绩评阅人评定成绩答辩组评定成绩总评成绩40%+20%+40%评定等级注：成绩评定由指导教师、评阅教师和答辩组分别给分(以百分记)，最后按“优(90-100)”、“良(80-89)”、“中(70-79)”、“及格(60-69)”、“不及格(60以下)”评定等级。其中， 指导教师评定成绩占40%，评阅人评定成绩占20%，答辩组评定成绩占40%。参考文献1 唐镇宝、常建蛾.机械设计课程设计.2006,华中科技大学出版社2 王为、汪建晓.机械设计.2007，华中科技大学出版社3 邓星钟.机电传动控制.2001，华中科技大学出版社4 第一工业机械部编.机床液压元件样本，19725 杨叔子、杨克聪.机械工程控制基础，2002，华中科技大学出版社6 左建民.液压与气压传动，2006.机械工业出版社7 付永领, 王岩, 裴忠才. 基于CAN总线液压喷漆机器人控制系统设计与实现. 机床与液压. 20038 丁又青, 朱新才. 一种新型型钢翻面机液压系统设计. 机床与液. 20039 刘剑雄, 韩建华. 物流自动化搬运机械手机电系统研究. 机床与液压. 200310 徐轶, 杨征瑞, 朱敏华, 温齐全. PLC在电液比例与伺服控制系统中的应用. 机床与液压. 2003 References1 Town, Bao Tang, Chang Jian moth. .2006 Mechanical design curriculum design, Huazhong University of Science and Technology Publishing House2 Wang,.2007 Mechanical design, Huazhong University of Science and Technology Publishing House3 DENG Xing-Zhong. .2001 Electrical Drive Control, Huazhong University of Science and Technology Publishing House4 Department of industrial machinery for the first. Hydraulic machine samples, 19725 Yang Shuzi, Yang Ke-Cong. Control based on mechanical engineering, 2002, Huazhong University of Science and Technology Publishing House6 Yang Shuzi, Yang Ke-Cong. Control based on mechanical engineering, 2002, Huazhong University of Science and Technology Publishing House7 FU Yong-ling, Wang Yan, Zhong-only. Based on the CAN bus control system for hydraulic robot painting Design and Implementation. Machine tools and hydraulic. 20038 Ding Qing, Zhu Xin-Cai. A new type of steel surface over the design of hydraulic systems. Machine with liquid. 20039 LI JIAN XIONG HAN JIAN HUA. Logistics automated mechanical handling system of mobile phone power. Machine tools and hydraulic. 200310 XU Yi, Yang Zheng Rui, SIP Chu, temperature range. PLC in electro-hydraulic proportional and servo control systems. Machine tools and hydraulic. 20031The Effect of a Viscous Coupling Used as a Front-Wheel Drive Limited-Slip Differential on Vehicle Traction and Handling1 ABCTRACTThe viscous coupling is known mainly as a driveline component in four wheel drive vehicles. Developments in recent years, however, point toward the probability that this device will become a major player in mainstream front-wheel drive application. Production application in European and Japanese front-wheel drive cars have demonstrated that viscous couplings provide substantial improvements not only in traction on slippery surfaces but also in handing and stability even under normal driving conditions.This paper presents a serious of proving ground tests which investigate the effects of a viscous coupling in a front-wheel drive vehicle on traction and handing. Testing demonstrates substantial traction improvements while only slightly influencing steering torque. Factors affecting this steering torque in front-wheel drive vehicles during straight line driving are described. Key vehicle design parameters are identified which greatly influence the compatibility of limited-slip differentials in front-wheel drive vehicles.Cornering tests show the influence of the viscous coupling on the self steering behavior of a front-wheel drive vehicle. Further testing demonstrates that a vehicle with a viscous limited-slip differential exhibits an improved stability under acceleration and throttle-off maneuvers during cornering.2 THE VISCOUS COUPLINGThe viscous coupling is a well known component in drivetrains. In this paper only a short summary of its basic function and principle shall be given.The viscous coupling operates according to the principle of fluid friction, and is thus dependent on speed difference. As shown in Figure 1 the viscous coupling has slip controlling properties in contrast to torque sensing systems.This means that the drive torque which is transmitted to the front wheels is automatically controlled in the sense of an optimized torque distribution.In a front-wheel drive vehicle the viscous coupling can be installed inside the differential or externally on an intermediate shaft. The external solution is shown in Figure 2.This layout has some significant advantages over the internal solution. First, 2there is usually enough space available in the area of the intermediate shaft to provide the required viscous characteristic. This is in contrast to the limited space left in todays front-axle differentials. Further, only minimal modification to the differential carrier and transmission case is required. In-house production of differentials is thus only slightly affected. Introduction as an option can be made easily especially when the shaft and the viscous unit is supplied as a complete unit. Finally, the intermediate shaft makes it possible to provide for sideshafts of equal length with transversely installed engines which is important to reduce torque steer (shown later in section 4).This special design also gives a good possibility for significant weight and cost reductions of the viscous unit. GKN Viscodrive is developing a low weight and cost viscous coupling. By using only two standardized outer diameters, standardized plates, plastic hubs and extruded material for the housing which can easily be cut to different lengths, it is possible to utilize a wide range of viscous characteristics. An example of this development is shown in Figure 3.3 TRACTION EFFECTSAs a torque balancing device, an open differential provides equal tractive effort to both driving wheels. It allows each wheel to rotate at different speeds during cornering without torsional wind-up. These characteristics, however, can be disadvantageous when adhesion variations between the left and right sides of the road surface (split-) limits the torque transmitted for both wheels to that which can be supported by the low- wheel.With a viscous limited-slip differential, it is possible to utilize the higher adhesion potential of the wheel on the high-surface. This is schematically shown in Figure 4.When for example, the maximum transmittable torque for one wheel is exceeded on a split-surface or during cornering with high lateral acceleration, a speed difference between the two driving wheels occurs. The resulting self-locking torque in the viscous coupling resists any further increase in speed difference and transmits the appropriate torque to the wheel with the better traction potential.It can be seen in Figure 4 that the difference in the tractive forces results in a yawing moment which tries to turn the vehicle in to the low-side, To keep the vehicle in a straight line the driver has to compensate this with opposite steering input. Though the fluid-friction principle of the viscous coupling and the resulting soft 3transition from open to locking action, this is easily possible, The appropriate results obtained from vehicle tests are shown in Figure 5.Reported are the average steering-wheel torque Ts and the average corrective opposite steering input required to maintain a straight course during acceleration on a split-track with an open and a viscous differential. The differences between the values with the open differential and those with the viscous coupling are relatively large in comparison to each other. However, they are small in absolute terms. Subjectively, the steering influence is nearly unnoticeable. The torque steer is also influenced by several kinematic parameters which will be explained in the next section of this paper.4 FACTORS AFFECTING STEERING TORQUEAs shown in Figure 6 the tractive forces lead to an increase in the toe-in response per wheel. For differing tractive forces, Which appear when accelerating on split-with limited-slip differentials, the toe-in response changes per wheel are also different.Unfortunately, this effect leads to an undesirable turn-in response to the low-side, i.e. the same yaw direction as caused by the difference in the tractive forces.Reduced toe-in elasticity is thus an essential requirement for the successful front-axle application of a viscous limited-slip differential as well as any other type of limited-slip differential.Generally the following equations apply to the driving forces on a wheelVTFF With Tractive ForceTF Vertical Wheel LoadVF Utilized Adhesion CoefficientThese driving forces result in steering torque at each wheel via the wheel disturbance level arm “e” and a steering torque difference between the wheels given by the equation:=eTloHhiHFFecosWhere Steering Torque DifferenceeT e=Wheel Disturbance Level Arm King Pin Angle4 hi=high-side subscript lo=low-side subscriptIn the case of front-wheel drive vehicles with open differentials, Ts is almost unnoticeable, since the torque bias () is no more than 1.35.loHhiTFF/For applications with limited-slip differentials, however, the influence is significant. Thus the wheel disturbance lever arm e should be as small as possible. Differing wheel loads also lead to an increase in Te so the difference should also be as small as possible.When torque is transmitted by an articulated CV-Joint, on the drive side (subscript 1) and the driven side (subscript 2),differing secondary moments are produced that must have a reaction in a vertical plane relative to the plane of articulation. The magnitude and direction of the secondary moments (M) are calculated as follows (see Figure 8):Drive side M1 =vvTTtan/)2/tan(2Driven side M2 =vvTTtan/)2/tan(2With T2 =dynTrF =TsystemJoTfint, 2Where Vertical Articulation Anglev Resulting Articulation Angle Dynamic Wheel Radiusdynr Average Torque LossTThe component acts around the king-pin axis (see figure 7) as a cos2Msteering torque per wheel and as a steering torque difference between the wheels as follows:)tan/2/tan()sin/2/tan(cos22liwhiwTTTTT where Steering Torque DifferenceT WWheel side subscriptIt is therefore apparent that not only differing driving torque but also differing 5articulations caused by various driveshaft lengths are also a factor. Referring to the moment-polygon in Figure 7, the rotational direction of M2 or respectively change, Tdepending on the position of the wheel-center to the gearbox output.For the normal position of the halfshaft shown in Figure 7(wheel-center below the gearbox output joint) the secondary moments work in the same rotational direction as the driving forces. For a modified suspension layout (wheel-center above gearbox output joint, i.e. negative) the secondary moments counteract the moments caused vby the driving forces. Thus for good compatibility of the front axle with a limited-slip differential, the design requires: 1) vertical bending angles which are centered around or negative () with same values of on both left and right sides; and 2) 0v0vvsideshafts of equal length.The influence of the secondary moments on the steering is not only limited to the direct reactions described above. Indirect reactions from the connection shaft between the wheel-side and the gearbox-side joint can also arise, as shown below:Figure 9: Indirect Reactions Generated by Halfshaft Articulation in the Vertical PlaneFor transmission of torque without loss and both of the secondary vdvwmoments acting on the connection shaft compensate each other. In reality (with torque loss), however, a secondary moment difference appears: WDDWMMM12With TTTWD22The secondary moment difference is:DWMVWWVWWVDVDWTTDTwTTtan/2/tansin/tan22/2For reasons of simplification it apply that and to VVWVDTTTWDgiveVVVDWTMtan/1sin/12/tan requires opposing reaction forces on both joints where DWM. Due to the joint disturbance lever arm f, a further steering torque LMFDWDW/also acts around the king-pin axis:LfMTDWf/cos6loloDWhihiDWfLMLMfT/cosWhere Steering Torque per WheelfT Steering Torque DifferencefT Joint Disturbance Leverf Connection shaft (halfshaft) LengthLFor small values of f, which should be ideally zero, is of minor influence.fT5EFFECT ON CORNERINGViscous couplings also provide a self-locking torque when cornering, due to speed differences between the driving wheels. During steady state cornering, as shown in figure 10, the slower inside wheel tends to be additionally driven through the viscous coupling by the outside wheel.Figure 10: Tractive forces for a front-wheel drive vehicle during steady state cornering The difference between the Tractive forces Dfr and Dfl results in a yaw moment MCOG, which has to be compensated by a higher lateral force, and hence a larger slip angle af at the front axle. Thus the influence of a viscous coupling in a front-wheel drive vehicle on self-steering tends towards an understeering characteristic. This behavior is totally consistent with the handling bias of modern vehicles which all under steer during steady state cornering maneuvers. Appropriate test results are shown in figure 11.Figure 11: comparison between vehicles fitted with an open differential and viscous coupling during steady state cornering.The asymmetric distribution of the tractive forces during cornering as shown in figure 10 improves also the straight-line running. Every deviation from the straight-line position causes the wheels to roll on slightly different radii. The difference between the driving forces and the resulting yaw moment tries to restore the vehicle to straight-line running again (see figure 10).Although these directional deviations result in only small differences in wheel travel radii, the rotational differences especially at high speeds are large enough for a viscous coupling front differential to bring improvements in straight-line running.High powered front-wheel drive vehicles fitted with open differentials often spin 7their inside wheels when accelerating out of tight corners in low gear. In vehicles fitted with limited-slip viscous differentials, this spinning is limited and the torque generated by the speed difference between the wheels provides additional tractive effort for the outside driving wheel. this is shown in figure 12Figure 12: tractive forces for a front-wheel drive vehicle with viscous limited-slip differential during acceleration in a bend The acceleration capacity is thus improved, particularly when turning or accelerating out of a T-junction maneuver ( i.e. accelerating from a stopped position at a “T” intersection-right or left turn ).Figures 13 and 14 show the results of acceleration tests during steady state cornering with an open differential and with viscous limited-slip differential .Figure 13: acceleration characteristics for a front-wheel drive vehicle with an open differential on wet asphalt at a radius of 40m (fixed steering wheel angle throughout test).Figure 14: Acceleration Characteristics for a Front-Wheel Drive Vehicle with Viscous Coupling on Wet Asphalt at a Radius of 40m (Fixed steering wheel angle throughout test)The vehicle with an open differential achieves an average acceleration of 2.0 while the2/smvehicle with the viscous coupling reaches an average of 2.3 (limited by 2/smengine-power). In these tests, the maximum speed difference, caused by spinning of the inside driven wheel was reduced from 240 rpm with open differential to 100 rpm with the viscous coupling.During acceleration in a bend, front-wheel drive vehicles in general tend to understeer more than when running at a steady speed. The reason for this is the reduction of the potential to transmit lateral forces at the front-tires due to weight transfer to the rear wheels and increased longitudinal forces at the driving wheels. In an open loop control-circle-test this can be seen in the drop of the yawing speed (yaw rate) after starting to accelerate (Time 0 in Figure 13 and 14). It can also be taken from Figure 13 and Figure 14 that the yaw rate of the vehicle with the open differential falls-off more rapidly than for the vehicle with the viscous coupling starting to accelerate. Approximately 2 seconds after starting to accelerate, however, the yaw rate fall-off gradient of the viscous-coupled vehicle increases more than at the 8vehicle with open differential.The vehicle with the limited slip front differential thus has a more stable initial reaction under accelerating during cornering than the vehicle with the open differential, reducing its understeer. This is due to the higher slip at the inside driving wheel causing an increase in driving force through the viscous coupling to the outside wheel, which is illustrated in Figure 12. the imbalance in the front wheel tractive forces results in a yaw moment acting in direction of the turn, countering the CSDMundersteer.When the adhesion limits of the driving wheels are exceed, the vehicle with the viscous coupling understeers more noticeably than the vehicle with the open differential (here, 2 seconds after starting to accelerate). On very low friction surfaces, such as snow or ice, stronger understeer is to be expected when accelerating in a curve with a limited slip differential because the driving wheels-connected through the viscous coupling-can be made to spin more easily (power-under-steering). This characteristic can, however, be easily controlied by the driver or by an automatic throttle modulating traction control system. Under these conditions a much easier to control than a rear-wheel drive car. Which can exhibit power-oversteering when accelerating during cornering. All things, considered, the advantage through the stabilized acceleration behavior of a viscous coupling equipped vehicle during acceleration the small disadvantage on slippery surfaces.Throttle-off reactions during cornering, caused by releasing the accelerator suddenly, usually result in a front-wheel drive vehicle turning into the turn (throttle-off oversteering ). High-powered modeles which can reach high lateral accelerations show the heaviest reactions. This throttle-off reaction has several causes such as kinematic influence, or as the vehicle attempting to travel on a smaller cornering radius with reducing speed. The essential reason, however, is the dynamic weight transfer from the rear to the front axle, which results in reduced slip-angles on the front and increased slip-angles on the rear wheels. Because the rear wheels are not transmitting driving torque, the influence on the rear axle in this case is greater than that of the front axle. The driving forces on the front wheels before throttle-off (see Figure 10) become over running or braking forces afterwards, which is illustrated for the viscous equipped vehicle in Figure 15.Figure 15:Baraking Forces for a Front-Wheel Drive Vehicle with Viscous 9Limited-Slip Differential Immediately after a Throttle-off Maneuver While CorneringAs the inner wheel continued to turn more slowly than the outer wheel, the viscous coupling provides the outer wheel with the larger braking force . The force fBdifference between the front-wheels applied around the center of gravity of the vehicle causes a yaw moment that counteracts the normal turn-in reaction.GCM0When cornering behavior during a throttle-off maneuver is compared for vehicles with open differentials and viscous couplings, as shown in Figure 16 and 17, the speed difference between the two driving wheels is reduced with a viscous differential.Figure 16: Throttle-off Characteristics for a Front-Wheel Drive Vehicle with an open Differential on Wet Asphalt at a Radius of 40m (Open Loop)Figure 17:Throttle-off Characteristics for a Front-Wheel Drive Vehicle with Viscous Coupling on Wet Asphalt at a Radius of 40m (Open Loop)The yawing speed (yaw rate), and the relative yawing angle (in addition to the yaw angle which the vehicle would have maintained in case of continued steady state cornering) show a pronounced increase after throttle-off (Time=0 seconds in Figure 14 and 15) with the open differential. Both the sudden increase of the yaw rate after throttle-off and also the increase of the relative yaw angle are significantly reduced in the vehicle equipped with a viscous limited-slip differential.A normal driver os a front-wheel drive vehicle is usually only accustomed to neutral and understeering vehicle handing behavior, the driver can then be surprised by sudden and forceful oversteering reaction after an abrupt release of the throttle, for example in a bend with decreasing radius. This vehicle reaction is further worsened if the driver over-corrects for the situation. Accidents where cars leave the road to the inner side of the curve is proof of this occurrence. Hence the viscous coupling improves the throttle-off behavior while remaining controllable, predictable, and safer for an average driver.6. EFFECT ON BRAKING The viscous coupling in a front-wheel drive vehicle without ABS (anti-lock braking system) has only a very small influence on the braking behavior on split- surfaces. Hence the front-wheels are connected partially via the front-wheel on the low- side is slightly higher than in an vehicle with an open differential. On the other side ,the brake pressure to lock the front-wheel on the high- side is slightly lower. 10These differences can be measured in an instrumented test vehicle but are hardly noticeable in a subjective assessment. The locking sequence of front and rear axle is not influenced by the viscous coupling.Most ABS offered today have individual control of each front wheel. Electronic ABS in front-wheel drive vehicles must allow for the considerable differences in effective wheel inertia between braking with the clutch engaged and disengaged.Partial coupling of the front wheels through the viscous unit does not therefore compromise the action of the ABS - a fact that has been confirmed by numerous tests and by several independent car manufacturers. The one theoretical exception to this occurs on a split-surface if a yaw moment build-up delay or Yaw Moment Reduction(YMR) is included in the ABS control unit. Figure 18 shows typical brake pressure sequences, with and without YMR.figure 18: brake pressure build-up characteristics for the front brakes of a vehicle braking on split- with ABS. In vehicles with low yaw inertia and a short wheelbase, the yaw moment build-up can be delayed to allow an average driver enough reaction time by slowing the brake pressure build-up over the ABS for the high- wheel. The wheel on the surface with the higher friction coefficient is therefore, particularly at the beginning of braking, under-braked and runs with less slip. The low- wheel, in contrast, can at the same time have a very high slip, which results in a speed difference across the viscous differential. The resulting self-locking torque then appears as an extra braking force at the high- wheel which counteracts the YMR.Although this might be considered as a negative effect and can easily be corrected when setting the YMR algorithm for a vehicle with a front viscous coupling, vehicle tests have proved that the influence is so slight that no special development of new ABS/YMR algorithms are actually needed. Some typical averaged test results are summarized in Figure 19.figure 19 : results form ABS braking tests with YMR on split-(Vo=50 mph, 3rd Gear, closed loop ) in figure 19 on the left a comparison of the maximum speed difference which occurred in the first ABS control cycle during braking is shown. It is obvious that the viscous coupling is reducing this speed difference. As the viscous coupling counteracts the YMR, the required steering wheel angle to keep the vehicle 11in straight direction in the first second of braking increased from 39 to 51 (figure 19,middle). Since most vehicle and ABS manufacturers consider 90 to be the critical limit, this can be tolerated. Finally, as the self-locking torque produced by the viscous coupling causes an increase in high-. Wheel braking force, a slightly higher vehicle deceleration was maintained(figure 19,right).7 SUMMARYin conclusion,it can be established that the application of a viscous coupling in a front-axle differential. It also positively influences the complete vehicle handling and stability , with only slight, but acceptable influence on torques-steer. To reduce unwanted torque-steer effects a basic set of design rules have been established: Toe-in response due to longitudinal load change must be as small as possible . Distance between king-pin axis and wheel center has to be as small as possible. Vertical bending angle-rang should be centered around zero(or negative). vertical bending angles should be the same for both sides. Sideshafts should be of equal length.Of minor influence on torque-steer is the joint disturbance lever arm which should be ideally zero for other reasons anyway. Braking with and without ABS is only negligibly influenced by the viscous coupling. Traction is significantly improved by the viscous limited slip differential in a front-wheel drive vehicle.12The self-steering behavior of a front-wheel drive vehicle is slightly influenced by a viscous limited slip differential in the direction of understeer. The improved reactions to throttle-off and acceleration during cornering make a vehicle with viscous coupling in the front-axle considerably more stable, more predictable and therefore safer.131 基本概念 黏性连接器主要地被认为是在四轮驱动的汽车上驱动路线的一部件。然而，在近些年的发展中，施用在前轮驱动的趋势中将成为重要角色的观点是可能的。在欧洲和日本前轮驱动轿车产量的施用已经证明黏性连接器不仅对于光滑路面的汽车牵引，而且在正常行驶条件下对于操纵性和稳定性都有所改善。这篇文章展示出调查黏性连接器对汽车牵引和操纵的影响的重大检验场试验，试验证明大多数牵引的改善仅仅轻微地影响转向装置的扭转力。前轮驱动的汽车在直线行驶时影响发动机转矩的因素被描述出来。在前轮驱动的汽车上极大地影响限制滑移差速器适合性的关键汽车设计参数被确定。转弯试验展现出黏性连接器在前轮驱动的汽车上独立转弯时的影响。进一步的试验证明安装黏性限制滑移差速器的汽车在加速和转弯时节气门频繁关闭的 情况下显示出一个改善的稳定性。2 黏性连接器 黏性连接器被广泛认为是驱动列车的一组成部件。在这篇文章中仅仅给出它的基本功能和原理的简明概要。黏性连接器是根据液体摩擦的原理和依靠速度差来运转的。正如图 1 所示黏性连接器的滑动控制特性和驱动观察系统的对比。这表明传送到前轮的驱动扭转力是由一个优化的扭转力分配检测器自动控制的。在前轮驱动的汽车上黏性连接器可以安装在差速器的内侧或者一根中间轴的外面。外面的方式如图 2 所示。内部的这种设计方式有很大的优点。首先，在中间轴区域可以得到足够的空间来提供符合要求的黏性特性。这和当今前轮轴差速器只留下有限的空间相对比。其次，差速器架和转送轴套只需要很小的修改。而且差速器壳体的生产也仅仅只有一点影响。引用作为一个选择性的事很容易做到尤其当轴和黏性单元作为一个整体单元被共给时。最后，中间轴使为等长的的侧偏轴提供横向安装发动机是可能的，横向地安装发动机对于减小扭转力的操纵是很重要的（后面第四部分说明了） 。14这种特殊的设计也为有实际意义的重量和黏性单元费用的降低给出了很好的可能性。GKN Viscodrive 正在发展一种低重量和低成本的黏性连接器。通过使用仅仅两个标准化的直径、标准化的盘，塑料轮毂和挤压成型的材料造成的储存室它能很容易地被截成不同的长度，使用一个宽的黏性范围是可能的。在图 3 中显示出这种发展的一个例子。3 牵引力的影响作为一个扭转力平衡装置，一个开的差速器提供相等的力到两个驱动轮上。它也允许每个车轮在扭转没结束转弯时以不同的速度转动。然而，这种特性当道路表面滑动系数为限制扭转力传递到两轮的左、右附着变动时是不利的，它能被低滑动系数的轮子支持。安装黏性限制滑移差速器,在高的值的路面上它可能利用高车轮附着潜在性.这在图 4 中显示出。例如，当一个车轮传递的最大扭转力超出表面滑动系数允许值或者以一个高的侧面加速度转弯时，两个车轮的速度是不同的.在黏性连接器中产生的自锁扭转力抵抗速度差的增加并且传递合适的扭转力到车轮上它具有更好的牵引力潜能。在图 4 中可以看出牵引力的不同导致汽车瞬间向低滑动系数值()一侧跑偏，为了保持汽车直线行驶驾驶员必须施加一个相反的扭转力来补偿。通过黏性连接器的液体摩擦原理和从打开到锁死柔和的传递结果,这是很可能的，从汽车实验中得到的合适结果如图 5 所示。报告称平均操纵轮扭转力和为保持带有一个开式的并且黏性的差速器在ST加速期间在滑动系数的路面上直线行驶应输入的平均正确的相对的转向操纵。相互对照开式差速器和那些黏性连接器是相对大的。然而，在绝对条件下它们是小的。主观地说，转向装置的影响是不明显的。扭转力操纵也受几个运动参数影响这些参数将在这篇文章下个部分解释。4 影响转向装置扭转力的因素 如图 6 所示牵引力引起一个从头到尾的增加来反应每个车轮。因为带有限15制滑动差速器的车轮在滑动系数的路面上加速时会出现不同的牵引力，所以从头到尾反应每个车轮的变化也是不同的。不幸的是，这个作用将导致一个不期望的朝低滑动系数一侧的反应，也就是说在不同的牵引力下产生相同的跑偏方向。降低从头到尾的弹力是黏性限制滑动差速器像其它任何形式差速器一样在前轴的成功应用所必须具备的。普遍地用下面的公式计算一个车轮的驱动力TVFF 牵引力TF车轮垂直载荷VF利用的附着系数这些驱动力导致在车轮之间每个车轮的转向装置扭转力经过车轮干扰常数e 干扰后与每个车轮的转向装置扭转力是不同的，给出下面的等式。cos()ioeH hH lTeFF 这里 扭转力矩差值eT e车轮干扰常数 主销倾角高滑动系数一侧下标ih低滑动系数一侧下标ol 在带有开式差速器前轮驱动汽车的情况下，是很不明显的，因为扭转力ST基数是不大于 1.35 的。(/)H hiH loFF然而，因为应用了限制滑动差速器，这个影响是很有意义的。这样车轮干扰常数 e 就应该尽可能的小。不同的车轮载荷也会导致的增加所以差别也eTAeTA要尽可能的小。当扭转力通过铰接“CV 连接”传递时，在主动一侧（下标 1）和从动一侧16（下标 2） ，必须反应垂直平面相对于连接平面的不同的第二个力矩产生了。第二个力矩（M）大小和方向用于下面的式子计算（如图 8）：主动一侧12tan(/2)/tanvvMTTA从动一侧 22tan(/2)/tanvvMTTA2TdynTF rA2(,Tf T连接系统）这里 纵向连接角v 产生的连接角 产生变化的轮子半径dynr平均扭转力矩损失T当每个装置的转向扭转力以及轮子之间的转向装置扭转力不同时，将围绕着主销轴线变动，如下所示：2cosMAcosT 22(tan/2/sin)(tan/2/tan)vvw hivvw liTTTT这里 转向装置扭转力矩差T W轮子一侧的下标因此很明显不仅不同的驱动扭转力而且黏性驱动轴长度的不同也是一个因素。说道图 7 中的力矩多边形，的旋转方向或者各自地变化，都取决于2MT轮子中心到变速箱输出的位置。如图 7 所示由于半轴的正常位置（轮子中心低于变速箱的输出点）第二个力矩产生和驱动力一样的旋转方向。由于改进的悬挂装置设计（车轮中心高于变速箱输出点，也就是说，为负值）第二个力矩抵消了由驱动力引起的力矩。v这样为了得到带一个限制滑动差速器前轴好的适应性，设计要求：1）纵向弯曲角近似或者负值（）且左侧和右侧的值相等；2）等长度的侧轴。0v0vv第二力矩在转向装置的影响不仅仅是上面描述的限制直接反应。从连接轴17到车轮侧面和变速箱侧面之间的连接点间接反应也会产生，如下所示：图表 9：由纵向平面的半轴连接产生的间接反应因为扭转力传递没有损失并且两个在连接轴上的第二个力矩都相vwvd互补偿。然而，事实上（有扭转力损失） ，第二个力矩出现不同： 21DWDWMMM 22DWTTT第二个力矩不同点是：22()tan/2/sintan/2/tanDWWWVDWvwWvwMTTTTT为了简化应用给出和fTVDVWVDTT wT(tan/2 1/sin1/tan)DWvvvMTA需要在两个连接处都有抵抗反应的力这里DWM。由连接处引起的干扰常数 f，一个附加的转向装置扭转力矩/DWDWFML 也围绕着主销轴线变动： cos/fDWTMfL A A这里 每个车轮的转向装置扭转力矩fT 转向装置扭转力矩差fT f连接处干扰系数 L连接轴（半轴）的长度由于 f 值小，理想值是 0，的影响较小。fT5 转弯时的效应扭转时由于驱动轮的速度不相等，黏性连接器也提供一个自琐的扭转力矩。如图表 10 所示，在平稳转向过程中，速度较慢的内侧车轮被外侧车轮黏性连接器施加的一个附加的驱动力。如图表 10：前轮驱动力的汽车稳定状态下转向时的牵引力。18不同的牵引力和导致一个侧偏力矩 MCOG，它必须被一个较大的flDfrDflD侧偏力补偿，因此在前轴有一个大的滑动角 af。因此前驱动轮的汽车自动转向装置上黏性连接器的影响趋向一个在转向装置状态下的特性。这个运动方式整体上和所有转向操纵下在稳定状态下转弯移动时的现代汽车操纵方式的偏重心相一致.合适的试验结果如图表 11 所示。如图表 11：安装有开式差速器的汽车饿安装有黏性连接器的汽车在稳定状态下转弯时的对比如图表 10 所示