關節(jié)式自動上下料機械手設計【三自由度 圓柱坐標式液壓驅動】【三菱PLC】【CAD高清圖紙和文檔】

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畢業(yè)設計（論文）檔案袋內組成部分 一、畢業(yè)設計（論文）冊內容與裝訂順序： l 封面：論文題目不得超過20個字，要簡練、準確，可分為兩行。 l 內容 1、畢業(yè)設計（論文）任務書；任務書由指導教師填寫，經(jīng)所在系部審查簽字后生效。 2、畢業(yè)設計（論文）開題報告； 3、畢業(yè)設計（論文）學生申請答辯表與指導教師畢業(yè)設計（論文）評審表； 4、畢業(yè)設計（論文）評閱人評審表； 5、畢業(yè)設計（論文）答辯表； 6、畢業(yè)設計（論文）答辯記錄表； 7、畢業(yè)設計（論文）成績評定總表； 8、論文： (1)中文題目與作者； (2)英文題目與作者； (3)中文內容摘要和關鍵詞； (4)英文內容摘要和關鍵詞； (5)目錄； (6)正文； (7)致謝； (8)參考文獻及引用資料目錄； (9)附錄； (10)實驗數(shù)據(jù)表、有關圖紙(大于3#圖幅時單獨裝訂)； l 封底。 二、英文資料翻譯冊內容與裝訂順序： l 封面； l 內容 1、英文原文； 2、中文翻譯； 3、閱讀書目； l 封底。 1 畢業(yè)設計（論文）任務書 系 部 機械工程系 指導教師 王海濤 職 稱 副教授 學生姓名 郭嘉文 專業(yè)班級 05機制本（2） 學 號 0515011202 設計題目 關節(jié)式自動上下料機械手設計（PLC控制） 設 計 內 容 目 標 和 要 求 （設計內容目標和要求、設計進度等） 內容:了解關節(jié)式機械手的基本結構和設計方法，學習PLC控制的有關內容，利用PLC的梯形圖編寫程序，掌握液壓系統(tǒng)的設計，學會查找資料，利用資料解決問題。 要求： 1． 完成關節(jié)式機械手的整體裝配圖； 2． 完成液壓系統(tǒng)原理圖； 3． 完成PLC外部接線圖； 4． 完成PLC梯形圖編程，運行程序通過； 5． 完成相關英文翻譯一篇； 6． 撰寫設計說明書，要求字跡工整。 指導教師簽名： 年 月 日 系 部審 核 此表由指導教師填寫 由所在系部審核 2-1 畢業(yè)設計（論文）學生開題報告 課題名稱 關節(jié)式自動上下料機械手設計（PLC控制） 課題來源 生產實踐 課題類型 AX 指導教師 王海濤（副教授） 學生姓名 郭嘉文 學 號 0515011202 專業(yè)班級 05機制2班 本課題的研究現(xiàn)狀、研究目的及意義 工業(yè)機械手是人類創(chuàng)造的一種機器,更是人類創(chuàng)造的一項偉大奇跡,其研究、開發(fā)和設計是從二十世紀中葉開始的.我國的工業(yè)機械手是從80年代"七五"科技攻關開始起步,在國家的支持下,通過"七五","八五"科技攻關,目前已經(jīng)基本掌握了機械手操作機的設計制造技術,控制系統(tǒng)硬件和軟件設計技術,運動學和軌跡規(guī)劃技術,生產了部分機器人關鍵元器件，開發(fā)出噴漆，孤焊，點焊，裝配，搬運等機器人，其中有130多臺噴漆機器人在二十余家企業(yè)的近30條自動噴漆生產線（站）上獲得規(guī)模應用，孤焊機器人已經(jīng)應用在汽車制造廠的焊裝線上。但總的看來，我國的工業(yè)機械手技術及其工程應用的水平和國外比還有一定距離。如：可靠性低于國外產品，機械手應用工程起步較晚，應用領域窄，生產線系統(tǒng)技術與國外比有差距。影響我國機械手發(fā)展的關鍵平臺因素就是其軟件，硬件和機械結構。目前工業(yè)機械手仍大量應用在制造業(yè)，其中汽車工業(yè)占第一位（占28.9%），電器制造業(yè)第二位（占16.4%），化工第三位（占11.7%）。發(fā)達國家汽車行業(yè)機械手應用占總保有量百分比為23.4%～53%，年產每萬輛汽車所擁有的機械手數(shù)為（包括整車和零部件）：日本88.0臺，德國64.0臺，法國32.2臺，英國26.9臺，美國33.8臺，意大利48.0臺 世界工業(yè)機械手的數(shù)目雖然每年在遞增，但市場是波浪式向前發(fā)展的。在新世紀的曙光下人們追求更舒適的工作條件，惡劣危險的勞動環(huán)境都需要用機器人代替人工。隨著機器人應用的深化和滲透，工業(yè)機械手在汽車行業(yè)中還在不斷開辟著新用途。機械手的發(fā)展也已經(jīng)由最初的液壓，氣壓控制開始向人工智能化轉變，并且隨著電子技術的發(fā)展和科技的不斷進步，這項技術將日益完善。 上料機械手與卸料機械手相比，其中上料機械手中的移動式搬運上料機械手適用于各種棒料，工件的自動搬運及上下料工作。例如鋁型材擠壓成型鋁棒料的搬運及高溫材料的自動上料作業(yè)，最大抓取棒料直徑達180mm，最大抓握重量可達30公斤，最大行走距離為1200mm。根據(jù)作業(yè)要求及載荷情況，機械手各關節(jié)運動速度可調。移動式搬運上料機械手主要由手爪，小臂，大臂，手臂回轉機構，小車行走機構，液壓泵站電器控制系統(tǒng)組成，同時具有高溫棒料啟動疏料裝置及用于安全防護用的光電保護系統(tǒng)。整個機械手及液壓系統(tǒng)均集中設置在行走小車上，結構緊湊。電氣控制系統(tǒng)采用OMRON可編程控制器，各種作業(yè)的實現(xiàn)可以通過編程實現(xiàn)。 2-2 本課題的研究內容 工業(yè)機器人系統(tǒng)由三大部分六個子系統(tǒng)組成。 三大部分是：機械部分，傳感部分，控制部分。六個子系統(tǒng)是：驅動系統(tǒng)，機械結構系統(tǒng)，感受系統(tǒng)，機器人—環(huán)境交互系統(tǒng)，人機交互系統(tǒng)，控制系等等。 該機械手為機床上下料機械手，圓柱體工件約30千克，要求下料之后馬上上料,一次完成上下料兩步驟。 動作順序：加工工位等候--機械手臂下降--手爪收攏夾緊已加工好的工件--手臂上升--手臂回轉至卸料工位--手臂下降--（手腕回轉）手爪松開工件--手臂上升--回轉至加工工位--手臂下降--手爪松開工件--手臂上升至等待工位等候。機械手的動作全部采用液壓驅動，PLC控制。 一、機械手驅動系統(tǒng)的選擇： 設計機械手時,選擇哪一類驅動系統(tǒng),要根據(jù)機械手的用途,作業(yè)要求,機械手的性能規(guī)范,控制功能,維護的復雜程度,運行的功耗,性能與價格比以及現(xiàn)有條件等綜合因素加以考慮.在注意各類驅動系統(tǒng)特點的基礎上,綜合上述各因素,充分論證其合理性,可行性,經(jīng)濟性以及可靠性后進行最終的選擇。按動力源的不同機器人又分為:電氣驅動、液壓驅動、氣動驅動三種。液壓驅動的特點是功率大，氣動驅動存在沖擊力大，精度難以控制等缺點，而電氣驅動具有控制方便、J性能好等優(yōu)點。（綜合考慮本機械手采用液壓驅動） 二、機械手結構設計： 機械結構是物料抓取機械手最終的執(zhí)行機構，是機器人賴以實現(xiàn)各種運動的實體，機械結構的布局、類型、傳動方式以及驅動系統(tǒng)的設計直接關系著機器人的工作性能。 機械結構按坐標形式主要有直角坐標型、球坐標型、圓柱坐標型、SCARA型和關節(jié)型等。 直角坐標型機器人操作臂的優(yōu)點是結構簡單、剛度高，三個關節(jié)的運動相互獨立，其間沒有禍合，不影響末端手爪的姿態(tài)，不產生奇異狀態(tài)，運動和控制都比較簡單;缺點是占地面積大，動作范圍小，操作靈活性差。 球坐標機器人和圓柱坐標機器人占地面積小，工作空間較大，在空間中的定位也比較直觀，但是它們的移動關節(jié)不容易防護，極坐標型機器人也存在移動關節(jié)不易防護的問題，它們多用于一些特殊的作業(yè)環(huán)境。 SCARA型機器人的主要特點是結構輕便，響應快，最適用于在垂直方向完成零件的裝配作業(yè)。 關節(jié)型機器人操作臂的優(yōu)點是結構緊湊，占地面積小，動作靈活，在作業(yè)空間內手臂的干涉最小，工作空間大;缺點是進行控制時計算量比較大，確定末端執(zhí)行部件的位姿不直觀。 針對該上下料機械手，為了使它具有一定的操作靈活性和較好的使用性能，在結構設計上采用圓柱坐標型。整個機器人系統(tǒng)設計為四個自由度。 自由度的分布情況為：機身的升降和回轉，手臂的伸縮，手腕的回轉。 三、手部的結構設計： 手部就是與物件接觸的部件。由于與物件接觸的形式不同，可分為夾持式和吸附式手部。為了使機械手的通用性更強，把機械手的手部結構設計成可更換結構，當被夾持工件是圓柱刀柄時，使用夾持式手部;當該機械手做其他用途，被夾持工件是板料時，可使用氣流負壓式吸盤。（本課題工件為圓柱體工件，所以手部采用夾持式） 2-3 具體設計內容和要求 一、設計內容： 1．了解關節(jié)式機械手的基本結構和設計方法 2．械手手部結構和運動機構的結構設計 3．機械手驅動系統(tǒng)的設計 4．學習PLC控制的有關內容，利用PLC的梯形圖編寫程序 5．繪制零件圖和裝配圖，設計說明書一份 二、設計要求： 1．完成關節(jié)式機械手的整體裝配圖 2．完成液壓系統(tǒng)原理圖 3．完成PLC外部接線圖 4．完成PLC梯形圖編程，運行程序通過 5．完成相關英文翻譯一篇 6．撰寫設計說明書，要求字跡工整 本課題研究的實施方案、進度安排 一、實施方案： 通過生產廠房中的實際觀察，以及利用網(wǎng)絡或圖書館參閱有關關節(jié)式上下料機械手的資料，根據(jù)已有的標準規(guī)格和設計要求，在老師的指導下進行合理的設計。 二、進度安排： 1）3月20-31日，主要進行畢業(yè)設計的準備工作，熟悉題目，收集資料，明確研究目的和任務； 2）4月1-25日，設計方案的確定，設計參數(shù)和尺寸的計算和分析； 3）4月26-5月15日，繪制機械手各部分圖紙（手爪圖、手腕圖、手臂圖和它們的組合圖）； 4）5月16-5月27日，收尾完善，編寫畢業(yè)設計論文，準備畢業(yè)設計答辯； 5）5月28-6月5日，畢業(yè)答辯。 3 畢業(yè)設計（論文）學生申請答辯表 課 題 名 稱 關節(jié)式自動上下料機械手設計（PLC控制） 指導教師（職稱） 王海濤（副教授） 申 請 理 由 申請畢業(yè) 學生所在系部 機械工程系 專業(yè)班級 05機制（本）2 學號 0515011202 學生簽名： 日期： 畢業(yè)設計（論文）指導教師評審表 序號 評分項目（理工科、管理類） 評分項目(文科) 滿分 評分 1 工作量 外文翻譯 15 2 文獻閱讀與外文翻譯 文獻閱讀與文獻綜述 10 3 技術水平與實際能力 創(chuàng)新能力與學術水平 25 4 研究成果基礎理論與專業(yè)知識 論證能力 25 5 文字表達 文字表達 10 6 學習態(tài)度與規(guī)范要求 學習態(tài)度與規(guī)范要求 15 總 分 100 評 語 （是否同意參加答辯） 指導教師簽名： 另附《畢業(yè)設計（論文）指導記錄冊》 年 月 日 4 畢業(yè)設計（論文）評閱人評審表 學生姓名 郭嘉文 專業(yè)班級 05機制（本）2 學號 0515011202 設計（論文）題目 關節(jié)式自動上下料機械手設計（PLC控制） 評閱人 評閱人職稱 序號 評分項目（理工科、管理類） 評分項目(文科) 滿分 評分 1 工作量 外文翻譯 15 2 文獻閱讀與外文翻譯 文獻閱讀與文獻綜述 10 3 技術水平與實際能力 創(chuàng)新能力與學術水平 25 4 研究成果基礎理論與專業(yè)知識 論證能力 25 5 文字表達 文字表達 10 6 學習態(tài)度與規(guī)范要求 學習態(tài)度與規(guī)范要求 15 總 分 100 評 語 評閱人簽名： 年 月 日 5 畢業(yè)設計（論文）答辯表 學生姓名 郭嘉文 專業(yè)班級 05機制（本）2 學號 0515011202 設計（論文）題目 關節(jié)式自動上下料機械手設計（PLC控制） 序號 評審項目 指 標 滿分 評分 1 報告內容 思路清新；語言表達準確，概念清楚，論點正確；實驗方法科學，分析歸納合理；結論有應用價值。 40 2 報告過程 準備工作充分,時間符合要求。 10 3 創(chuàng) 新 對前人工作有改進或突破，或有獨特見解。 10 4 答 辯 回答問題有理論依據(jù)，基本概念清楚。主要問題回答準確，深入。 40 總 分 100 答 辯 組 評 語 答辯組組長（簽字）： 年 月 日 答 辯 委 員 會 意 見 答辯委員會負責人（簽字）： 年 月 日 6-1 畢業(yè)設計（論文）答辯記錄表 學生姓名 郭嘉文 專業(yè)班級 05機制（本）2 學號 0515011202 設計（論文）題目 關節(jié)式自動上下料機械手設計（PLC控制） 答辯時間 答辯地點 答辯委員會名單 問題1 提問人： 問題： 回答（要點）： 問題2 提問人： 問題： 回答（要點）： 問題3 提問人： 問題： 回答（要點）： 記錄人簽名 問題4 提問人： 問題： 回答（要點）： 問題5 提問人： 問題： 回答（要點）： 問題6 提問人： 問題： 回答（要點）： 問題7 提問人： 問題： 回答（要點）： 問題8 提問人： 問題： 回答（要點）： 記錄人簽名 6-2 7 畢業(yè)設計（論文）成績評定總表 學生姓名： 郭 嘉 文 專業(yè)班級： 05機制（本）2 畢業(yè)設計（論文）題目：關節(jié)式自動上下料機械手設計（PLC控制） 成績類別 成績評定 Ⅰ指導教師評定成績 Ⅱ評閱人評定成績 Ⅲ答辯組評定成績 總評成績 Ⅰ×40%+Ⅱ×20%+Ⅲ×40% 評定等級 注：成績評定由指導教師、評閱教師和答辯組分別給分(以百分記)，最后按“優(yōu)(90--100)”、“良(80--89)”、“中(70--79)”、“及格(60--69)”、“不及格(60以下)”評定等級。其中， 指導教師評定成績占40%，評閱人評定成績占20%，答辯組評定成績占40%。 參考文獻 1 唐鎮(zhèn)寶、常建蛾.機械設計課程設計.2006,華中科技大學出版社 2 王為、汪建曉.機械設計.2007，華中科技大學出版社 3 鄧星鐘.機電傳動控制.2001，華中科技大學出版社 4 第一工業(yè)機械部編.機床液壓元件樣本，1972 5 楊叔子、楊克聰.機械工程控制基礎，2002，華中科技大學出版社 6 左建民.液壓與氣壓傳動，2006.機械工業(yè)出版社 7 付永領, 王巖, 裴忠才. 基于CAN總線液壓噴漆機器人控制系統(tǒng)設計與實現(xiàn). 機床與液壓. 2003 8 丁又青, 朱新才. 一種新型型鋼翻面機液壓系統(tǒng)設計. 機床與液. 2003 9 劉劍雄, 韓建華. 物流自動化搬運機械手機電系統(tǒng)研究. 機床與液壓. 2003 10 徐軼, 楊征瑞, 朱敏華, 溫齊全. PLC在電液比例與伺服控制系統(tǒng)中的應用. 機床與液壓. 2003 References 1 Town, Bao Tang, Chang Jian moth. .2006 Mechanical design curriculum design, Huazhong University of Science and Technology Publishing House 2 Wang,.2007 Mechanical design, Huazhong University of Science and Technology Publishing House 3 DENG Xing-Zhong. .2001 Electrical Drive Control, Huazhong University of Science and Technology Publishing House 4 Department of industrial machinery for the first. Hydraulic machine samples, 1972 5 Yang Shuzi, Yang Ke-Cong. Control based on mechanical engineering, 2002, Huazhong University of Science and Technology Publishing House 6 Yang Shuzi, Yang Ke-Cong. Control based on mechanical engineering, 2002, Huazhong University of Science and Technology Publishing House 7 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. 2003 8 Ding Qing, Zhu Xin-Cai. A new type of steel surface over the design of hydraulic systems. Machine with liquid. 2003 9 LI JIAN XIONG HAN JIAN HUA. Logistics automated mechanical handling system of mobile phone power. Machine tools and hydraulic. 2003 10 XU Yi, Yang Zheng Rui, SIP Chu, temperature range. PLC in electro-hydraulic proportional and servo control systems. Machine tools and hydraulic. 2003 1 The Effect of a Viscous Coupling Used as a Front-Wheel Drive Limited-Slip Differential on Vehicle Traction and Handling 1 ABCTRACT The 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 COUPLING The 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, 2 there 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 today’s 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 EFFECTS As 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-μ) limits the torque transmitted for both wheels to that which can be supported by the low-μ wheel. With a viscous limited-slip differential, it is possible to utilize the higher adhesion potential of the wheel on the high-μsurface. This is schematically shown in Figure 4. When for example, the maximum transmittable torque for one wheel is exceeded on a split-μ 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-μside, 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 3 transition 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-μtrack 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 TORQUE As 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- μwith 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- μside, 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 wheel?VTF? With Tractive Force Vertical Wheel LoadV Utilized Adhesion Coefficient? These 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: △ =eT??loHhiF???cos Where △ Steering Torque Difference?eT e=Wheel Disturbance Level Arm King Pin Angle? 4 hi=high-μside subscript lo=low-μside subscript In the case of front-wheel drive vehicles with open differentials, △Ts is almost unnoticeable, since the torque bias ( ) is no more than 1.35.loHhiTF?/ 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 = vvTT???tan/)2/tan(?? Driven side M2 = ? With T2 = dynTrF =???stemJofi,2? Where Vertical Articulation Anglev ?? Resulting Articulation Angle Dynamic Wheel Radiusdynr? Average Torque Loss?T? The component acts around the king-pin axis (see figure 7) as a ?cos2?M steering torque per wheel and as a steering torque difference between the wheels as follows: ])tan/2/tan()sin/2/tn[(cos 22 liwhiwTTT ?????? ??????? ????? where Steering Torque Difference ??? W Wheel side subscript It is therefore apparent that not only differing driving torque but also differing 5 articulations 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, ?T depending 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 v? by 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) 0?v?0?v v? sideshafts 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 Plane For transmission of torque without loss and both of the secondary vdw?? moments acting on the connection shaft compensate each other. In reality (with torque loss), however, a secondary moment difference appears: △ WDWM12? With ???T2 The secondary moment difference is:?DWM?? VWVWVDVDTwT ?????? tan/2/tansi/tan22/2 ??? For reasons of simplification it apply that and to ??TD? give △ ??VVVDWT???tan/1si/2tan??? △ requires opposing reaction forces on both joints where . Due to the joint disturbance lever arm f, a further steering torque LMF/? also acts around the king-pin axis:fTDWf /cos??? 6 ??loDWhiDWf LMT//cos????? Where Steering Torque per Wheel ?f Steering Torque Differencef Joint Disturbance Lever ?? Connection shaft (halfshaft) LengthL For small values of f, which should be ideally zero, is of minor influence.fT? 5．EFFECT ON CORNERING Viscous 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 7 their 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 12 Figure 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/sm vehicle with the viscous coupling reaches an average of 2.3 (limited by 2/sm engine-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 8 vehicle 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 CSDM understeer. 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 9 Limited-Slip Differential Immediately after a Throttle-off Maneuver While Cornering As 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 fB difference between the front-wheels applied around the center of gravity of the vehicle causes a yaw moment that counteracts the normal turn-in reaction.GCM0 When 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-μ surfaces. Hence the front-wheels are connected partially via the front-wheel on the low-μ 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-μ side is slightly lower. 10 These 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 the