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系主任 批準(zhǔn)日期 茂 名 學(xué) 院 畢 業(yè) 設(shè) 計(jì)（論 文）任 務(wù) 書 機(jī)電工程 系 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 專業(yè) 機(jī)電04－2 班 學(xué)生 廖志華 一、畢業(yè)設(shè)計(jì)(論文)課題 法蘭盤斜孔和徑向孔加工回轉(zhuǎn)分度鉆床夾具設(shè)計(jì) 二、畢業(yè)設(shè)計(jì)(論文)工作自 2008年 3 月 17日起至 2008 年 6 月 15 日止 三、畢業(yè)設(shè)計(jì)(論文)進(jìn)行地點(diǎn) 茂名學(xué)院機(jī)電工程學(xué)院 四、畢業(yè)設(shè)計(jì)(論文)的內(nèi)容要求 （一）、已知條件 （1）、被加工的零件的零件圖 （2）、成批生產(chǎn) （二）、主要內(nèi)容及要求 （1）、按要求寫出開題報(bào)告 （2）、結(jié)合課題到工廠進(jìn)行畢業(yè)實(shí)習(xí) （3）、收集國內(nèi)外有關(guān)情報(bào)資料，查閱文獻(xiàn)資料15篇以上 （4）、翻譯不少于5000字的英語科技文獻(xiàn) （5）、研究形成總體方案 （6）、設(shè)計(jì)繪制出夾具的總裝工作圖 （7）、繪制出主要零件圖 （8）、按學(xué)校規(guī)定格式編寫出不少于20000字的設(shè)計(jì)計(jì)算說明書（含文獻(xiàn)綜述） （9）、準(zhǔn)備和參加畢業(yè)答辯。 （三）、主要參考資料： （1）機(jī)床夾具圖冊P18~19 孟憲棟等主編 機(jī)械工業(yè)出版社 （2）巧改機(jī)床 陳榕林 張磊 編著中國農(nóng)業(yè)機(jī)械化出版社 （3）金屬切屑機(jī)床 上、下冊 顧熙賞等主編 上海科技出版社 （4）組合機(jī)床設(shè)計(jì)手冊 機(jī)械工業(yè)出版社 （5）機(jī)電傳動(dòng)與控制 鄧星鐘等 華中理工大學(xué)出版社 （6）新編機(jī)械設(shè)計(jì)手冊 徐生 機(jī)械工業(yè)出版社 （7）機(jī)械可靠性設(shè)計(jì) 劉信主編 機(jī)械工業(yè)出版社 （8）機(jī)械設(shè)計(jì)手冊 機(jī)械工業(yè)出版社 （9）機(jī)床夾具設(shè)計(jì) 龔定安等 西安交通大學(xué)出版社 （10）機(jī)床夾具設(shè)計(jì) 李慶壽 機(jī)械工業(yè)出版社 （11）機(jī)床設(shè)計(jì)圖冊 華東五高校編 華東科技大學(xué)出版社 （12）機(jī)電一體化系統(tǒng)設(shè)計(jì)手冊 楊黎明 主編 國防工業(yè)出版社 教研室負(fù)責(zé)人 指導(dǎo)教師 王安民（教授） 接受設(shè)計(jì)論文任務(wù)開始執(zhí)行日期 2008 年 3 月 17 日 學(xué)生簽名 廖志華 茂 名 學(xué) 院 畢業(yè)設(shè)計(jì)說明書 題 目： 法蘭盤斜孔和徑向孔加工臥、斜軸 回轉(zhuǎn)分度鉆床夾具的設(shè)計(jì) 英文并列題目: The Design of the Rotary-Drilling Fixture of the Horizontal and Inclined Shaft about Flange of the Slanting-Holes and Radial Holes Machining 學(xué)院 機(jī)電工程學(xué)院 專業(yè) 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 班級 機(jī)電04-2班　 學(xué)生 廖志華 指導(dǎo)教師（職稱） 王安民 (教授) 完成時(shí)間 2008年 3月 17日至 2008年 6月 15日 畢業(yè)設(shè)計(jì)（論文） 開題報(bào)告 題 目 法蘭盤斜孔和徑向孔加工臥、斜軸回轉(zhuǎn)分度鉆床夾具的設(shè)計(jì) The Design of the Rotary-Drilling Fixture of the Horizontal and Inclined Shaft about Flange of the Slanting-Holes and Horizontal Radial Holes Machining 學(xué) 院 茂名學(xué)院 年 級 2004級 專 業(yè) 機(jī)械設(shè)計(jì)制造及自動(dòng)化 學(xué) 號(hào) 04024020214 姓 名 廖志華 指導(dǎo)教師 王安民(教授) 2008年 3 月 17日 畢業(yè)設(shè)計(jì)（論文）開題報(bào)告 題目 法蘭盤斜孔和徑向孔加工臥、斜軸回轉(zhuǎn)分度鉆床夾具的設(shè)計(jì) 時(shí) 間 2008年 3月 17日至 2008年 6月 15 日 本課題的目的意義 （含國內(nèi)外的研究現(xiàn)狀分析） 機(jī)床夾具是機(jī)械制造工藝系統(tǒng)重要的組成部分，其實(shí)現(xiàn)工件定位和夾緊； 使工件加工時(shí)相對于機(jī)床刀具有正確的位置； 以保證工件的加工精度。其質(zhì)量的高低直接影響到零件制造的質(zhì)量、工人的勞動(dòng)強(qiáng)度、產(chǎn)品成本和生產(chǎn)率。通過機(jī)床夾具的設(shè)計(jì)，提高設(shè)計(jì)、計(jì)算、分析問題和解決問題的能力，綜合運(yùn)用計(jì)算機(jī)繪圖能力、表達(dá)技術(shù)問題的能力以及開拓創(chuàng)新的能力等。通過本夾緊機(jī)構(gòu)的設(shè)計(jì)進(jìn)而掌握一般機(jī)床夾具的一般方法、步驟和技巧，從而達(dá)到掌握一般機(jī)械的設(shè)計(jì)方法和技巧，綜合運(yùn)用所學(xué)的知識(shí)來解決工程實(shí)際問題。 機(jī)床夾具是用以裝夾工件和引導(dǎo)刀具的附加裝置。主要用于金屬切削加工，在機(jī)床與工件、刀具之間起橋梁作用，是工藝系統(tǒng)中的一個(gè)重要環(huán)節(jié)。它可準(zhǔn)確地確定工件與刀具、機(jī)床的相對位置，確保加工質(zhì)量；它可以提高生產(chǎn)效率，確保勞動(dòng)強(qiáng)度；它可以擴(kuò)大或改變機(jī)床的使用范圍等。因此，機(jī)床夾具是保證機(jī)械加工工藝過程正常進(jìn)行的技術(shù)硬件之一。 綜上所訴，需要對零件進(jìn)行夾具設(shè)計(jì)。 設(shè)計(jì)(論文)的基本條件及設(shè)計(jì)(論文)依據(jù) 零件圖1張，材料為45鋼 設(shè)計(jì)夾具的主要依據(jù) (1) 根據(jù)給定的生產(chǎn)量大小來確定夾具類型。 (2) 根據(jù)本單位的先有生產(chǎn)條件，注意充分發(fā)揮現(xiàn)場技術(shù)條件手段和技術(shù)力量的潛力來設(shè)計(jì)夾具。 本課題的主要內(nèi)容、 重點(diǎn)解決的問題 主要內(nèi)容: (1)設(shè)計(jì)該零件鉆孔的專用夾具 (2)繪制毛坯圖1張 (3)繪制裝配圖1張及零件圖若干張 (4)完成設(shè)計(jì)說明書一份,書寫格式符合茂名學(xué)院本科生畢業(yè)設(shè)計(jì)格式規(guī)范 (5)完成外文翻譯一份,內(nèi)容與畢業(yè)設(shè)計(jì)相關(guān),且不少于5000字符 重點(diǎn)解決問題:在保證零件加工質(zhì)量前提下,提高生產(chǎn)效率,降低消耗,以取得較好的經(jīng)濟(jì)效益和社會(huì)效益. 本課題欲達(dá)到的目的或預(yù)期研究的結(jié)果 畢業(yè)設(shè)計(jì)是學(xué)生完成本專業(yè)教學(xué)計(jì)劃的最后一個(gè)極為重要的實(shí)踐性教學(xué)環(huán)節(jié)，是使學(xué)生綜合運(yùn)用所學(xué)過的基本理論、基本知識(shí)與基本技能去解決專業(yè)范圍內(nèi)的工程技術(shù)問題而進(jìn)行的一次基本訓(xùn)練。這對學(xué)生即將從事的相關(guān)技術(shù)工作和未來事業(yè)的開拓都具有一定意義。 其主要目的： 一、 培養(yǎng)學(xué)生綜合分析和解決本專業(yè)的一般工程技術(shù)問題的獨(dú)立工作能力，拓寬和深化學(xué)生的知識(shí)。 二、 培養(yǎng)學(xué)生樹立正確的設(shè)計(jì)思想，設(shè)計(jì)構(gòu)思和創(chuàng)新思維，掌握工程設(shè)計(jì)的一般程序規(guī)范和方法。 三、 培養(yǎng)學(xué)生樹立正確的設(shè)計(jì)思想和使用技術(shù)資料、國家標(biāo)準(zhǔn)等手冊、圖冊工具書進(jìn)行設(shè)計(jì)計(jì)算，數(shù)據(jù)處理，編寫技術(shù)文件等方面的工作能力。 四、 培養(yǎng)學(xué)生進(jìn)行調(diào)查研究，面向?qū)嶋H，面向生產(chǎn)，向工人和技術(shù)人員學(xué)習(xí)的基本工作態(tài)度，工作作風(fēng)和工作方法。 計(jì) 劃 進(jìn) 度 時(shí) 間 工 作 內(nèi) 容 備 注 2008.3.20~2008.4.6 2008.4.7~2008.4.20 2008.4.21~2008.5.4 2008.5．5~2008.5.18 2008.5．21~2008.6.8 課題資料收集、寫開題報(bào)告 夾具的方案設(shè)計(jì) 工序設(shè)計(jì)與夾具方案的確定 夾具設(shè)計(jì)與繪制裝配圖及零件圖 畢業(yè)論文的撰寫整理及排版打印 指 導(dǎo) 教 師 意 見 指導(dǎo)教師簽名： 年 月 日 先進(jìn)制造與自動(dòng)化技術(shù)的發(fā)展 1　我國制造業(yè)面臨的挑戰(zhàn) 世紀(jì)之交，世界的政治、經(jīng)濟(jì)和技術(shù)發(fā)生了前所未有的巨大變化，經(jīng)濟(jì)全球化正在形成。信息技術(shù)對制造業(yè)產(chǎn)生了極其深刻和全面的影響，使制造業(yè)的發(fā)展打上了明顯的信息化烙印。經(jīng)濟(jì)全球化和信息化使制造業(yè)的競爭環(huán)境、發(fā)展模式及運(yùn)行效率與活動(dòng)空間等發(fā)生了深刻變化，這些變化對我國制造業(yè)提出了嚴(yán)峻的挑戰(zhàn)，同時(shí)也為實(shí)現(xiàn)我國制造業(yè)的跨越式發(fā)展提供了有利條件和機(jī)遇。 1.1　制造業(yè)競爭環(huán)境的變化 隨著經(jīng)濟(jì)全球化進(jìn)程的加快，出現(xiàn)了新的國際分工格局：發(fā)達(dá)國家主要發(fā)展知識(shí)密集型的高新技術(shù)產(chǎn)業(yè)和服務(wù)業(yè)，而把勞動(dòng)和資源密集型的產(chǎn)業(yè)向發(fā)展中國家轉(zhuǎn)移。經(jīng)濟(jì)全球化的浪潮和我國加入WTO，使我國正在逐步成為世界的重要制造基地?？鐕炯娂娫谖覈顿Y建立企業(yè)和技術(shù)中心，國外產(chǎn)品大舉進(jìn)入中國。這使產(chǎn)品的市場競爭更加激烈，也使得我國制造企業(yè)必須直接同跨國公司在技術(shù)、資源、人才等方面進(jìn)行正面競爭。面對如此嚴(yán)峻的挑戰(zhàn)，我國制造業(yè)只能背水一戰(zhàn)，加快技術(shù)升級的步伐，提高企業(yè)綜合競爭能力。 1.2　制造業(yè)發(fā)展模式的變化 信息化提高了生產(chǎn)要素的信息屬性，促使企業(yè)競爭模式從自然資源和人力的競爭轉(zhuǎn)向創(chuàng)新能力和創(chuàng)造高附加值產(chǎn)品的競爭；信息化使得知識(shí)的重要性凸顯，人才成為競爭優(yōu)勢的重要因素；信息化促使企業(yè)管理由金字塔型結(jié)構(gòu)向扁平型結(jié)構(gòu)轉(zhuǎn)變。經(jīng)營思想由粗放型向集約型轉(zhuǎn)變，出現(xiàn)了各種先進(jìn)制造模式，如并行工程、敏捷制造、網(wǎng)絡(luò)化制造和虛擬制造等，為我國企業(yè)向先進(jìn)制造模式轉(zhuǎn)變、提升我國制造企業(yè)的水平和能力提供了可以借鑒的模式。 1.3　制造企業(yè)運(yùn)行效率與活動(dòng)空間的變化 信息化促進(jìn)了國際金融市場的快速發(fā)展，不僅保障了跨國經(jīng)濟(jì)活動(dòng)的正常運(yùn)行，而且提高了資金在全球的流動(dòng)速度；信息化可以大大縮短產(chǎn)品上市時(shí)間，提高產(chǎn)品質(zhì)量，降低生產(chǎn)消耗和交易成本，提高資源利用率，從而大幅度提高制造企業(yè)的效率；信息化使企業(yè)在規(guī)模、經(jīng)濟(jì)實(shí)力和創(chuàng)新能力等方面得到了空前的發(fā)展，跨國公司的力量進(jìn)一步加強(qiáng)；信息化和經(jīng)濟(jì)全球化打破了國界的阻隔，跨國經(jīng)營日益普遍，國際貿(mào)易高速增長，國際投資日趨活躍，為企業(yè)發(fā)展創(chuàng)造了廣闊空間。 我國的制造業(yè)在國民經(jīng)濟(jì)中占有重要的地位，在工業(yè)化的進(jìn)程中又同時(shí)面；臨著信息化的艱巨任務(wù)。中共中央提出的“用信息化帶動(dòng)制造業(yè)現(xiàn)代化，用高新技術(shù)改造制造業(yè)，以實(shí)現(xiàn)制造業(yè)跨越發(fā)展”戰(zhàn)略，為我國發(fā)展先進(jìn)制造與自動(dòng)化技術(shù)指明了方向。 2　我國制造業(yè)存在的主要差距 由于我國工業(yè)化進(jìn)程起步較晚，與國際先進(jìn)水平相比，我國的制造業(yè)和制造技術(shù)還存在著階段性差距。為了迎接經(jīng)濟(jì)全球化和信息化的挑戰(zhàn)，迫切需要解決以下幾方面的問題。 a．產(chǎn)品創(chuàng)新能力較差，開發(fā)周期較長。我國機(jī)械制造業(yè)的新產(chǎn)品貢獻(xiàn)率約為18.09％（20O0年），而美國已經(jīng)達(dá)到52％左右（1995年）。我國大中型企業(yè)生產(chǎn)的 2 000多種主導(dǎo)產(chǎn)品的平均生命周期為10．5年，是美國同類產(chǎn)品生命周期的3．5倍。 我國有8O％以上的企業(yè)生產(chǎn)能力利用不足或嚴(yán)重不足，但同時(shí)每年還要進(jìn)口數(shù)以千億美元國內(nèi)短缺的產(chǎn)品。 b．制造工藝裝備落后，成套能力不強(qiáng)。我國大多數(shù)企業(yè)目前還采用較落后的制造工藝與技術(shù)裝備進(jìn)行生產(chǎn)，優(yōu)質(zhì)高效低耗工藝的普及率不足10％，數(shù)控機(jī)床、精密設(shè)備不足 5％，配有國產(chǎn)數(shù)控系統(tǒng)的中檔數(shù)控機(jī)床不超過 25％，高檔數(shù)控機(jī)床的90％以上依賴進(jìn)口；我國在大型成套裝備技術(shù)方面嚴(yán)重落后， 100％的光纖制造裝備、85％的集成電路（IC）制造裝備、 80％的石化裝備、 70％的轎車工業(yè)裝備都依賴進(jìn)口。 C．生產(chǎn)自動(dòng)化和優(yōu)化水平不高，資源綜合利用率低。我國平均勞動(dòng)生產(chǎn)率為0．263萬美元，而美國、日本和印度分別為9.37萬美元、10.47萬美元和0.34萬美元；我國的能源綜合利用率僅為32％左右，比國外的先進(jìn)水平低IO多個(gè)百分點(diǎn)；我國每萬元國民生產(chǎn)總值的能耗比發(fā)達(dá)國家高4倍多，主要產(chǎn)品單位能耗比發(fā)達(dá)國家高30％～90％，工業(yè)排放的污染物超過發(fā)達(dá)國家1O倍以上。 d．企業(yè)管理粗放，協(xié)作能力較差，國際市場開拓能力弱。我國多數(shù)企業(yè)缺少現(xiàn)代化管理的概念、方法和手段，眾多的企業(yè)尚處于經(jīng)驗(yàn)管理階段，企業(yè)機(jī)構(gòu)臃腫，富裕人員一般多達(dá) 3O％～ 4O％。我國機(jī)械工業(yè)的專業(yè)化水平僅為15％～30％，而美國、西歐諸國、日本企業(yè)的專業(yè)化水平已經(jīng)達(dá)到75％～95％，小而全、大而全的“莊園式企業(yè)”缺乏快速響應(yīng)市場需求的能力。經(jīng)過20多年的努力，我國出口商品占世界市場份額從0.5％提高到目前的3．5％，但是根據(jù)近3年的統(tǒng)計(jì)數(shù)據(jù)分析，高附加值和高技術(shù)含量的出口商品僅占我國出口商品總量的10％左右。 e．戰(zhàn)略必爭裝備和競爭前核心技術(shù)的開發(fā)相對薄弱。戰(zhàn)略必爭裝備涉及國家安全和經(jīng)濟(jì)命脈，對國民經(jīng)濟(jì)有重大影響。競爭前核心技術(shù)在未來的國際競爭中有可能開拓新的廣闊市場或成為新的重大關(guān)鍵技術(shù)。例如：用于海洋資源開發(fā)的水下作業(yè)裝備，用于高精尖設(shè)備制造的超精密加工裝備，面向IT等產(chǎn)業(yè)的集成電路制造關(guān)鍵裝備，對未來許多行業(yè)將產(chǎn)生重大影響的微機(jī)電系統(tǒng)（MEMS）以及集高技術(shù)于一身的仿人形機(jī)器人等。由于國外的技術(shù)封鎖，這些裝備和技術(shù)是花錢也很難買到的，必須靠自己的力量加以解決。 綜上所述，我國的制造業(yè)和制造技術(shù)還不能很好滿足國民經(jīng)濟(jì)發(fā)展和參與國際競爭的需要。不解決上述問題，中國的制造業(yè)就不能在激烈的競爭中生存和發(fā)展。為了使我國制造業(yè)在國內(nèi)、國際市場競爭中立于不敗之地，為了盡快形成我國自主創(chuàng)新和跨越發(fā)展的先進(jìn)制造技術(shù)體系，積極發(fā)展和應(yīng)用先進(jìn)制造與自動(dòng)化技術(shù)刻不容緩，勢在必行。 3 先進(jìn)制造與自動(dòng)化技術(shù)發(fā)展現(xiàn)狀 世界各國十分重視發(fā)展先進(jìn)制造與自動(dòng)化技術(shù)，許多跨國公司應(yīng)用先進(jìn)制造與自動(dòng)化技術(shù)實(shí)現(xiàn)了設(shè)計(jì)、制造后理和經(jīng)營的一體化，加強(qiáng)了在國際市場的壟斷地位。例如，美國波音公司在波音777客機(jī)的研制中，由于使用了先進(jìn)的產(chǎn)品開發(fā)設(shè)計(jì)技術(shù)，使開發(fā)周期從過去的8～9年縮短到4．5年，縮短了40％以上。成本降低25％，出錯(cuò)返工率降低75％，用戶滿意度也大幅度提高。美國通用汽車公司應(yīng)用現(xiàn)代集成制造系統(tǒng)技術(shù)，將轎車的開發(fā)周期由原來的48個(gè)月縮短到了24個(gè)月，碰撞試驗(yàn)的次數(shù)由原來的幾百次降到幾十次，應(yīng)用電子商務(wù)技術(shù)降低銷售成本 10％；美國 Exxon－ Mobil石油公司應(yīng)用先進(jìn)的綜合自動(dòng)化技術(shù)后，使企業(yè)的效益提高5％～8％，勞動(dòng)生產(chǎn)率提高例％～15％；機(jī)器人技術(shù)與自動(dòng)化工藝裝備的核心技術(shù)一直受到世界各國的重視，面向未來服務(wù)的水下機(jī)器人、微機(jī)器人。醫(yī)用機(jī)器人、仿人形機(jī)器人等特種機(jī)器人，面向國防、航空、航天等方面的超精密加工裝備，面向基礎(chǔ)設(shè)施建設(shè)的智能化大型工程機(jī)械，面向制造業(yè)的高精度、高效率、低成本和高柔性基礎(chǔ)制造裝備等已成為目前的研究開發(fā)重點(diǎn)。先進(jìn)制造與自動(dòng)化技術(shù)已經(jīng)成為帶動(dòng)制造業(yè)發(fā)展的重要推動(dòng)力。 為了占領(lǐng)先進(jìn)制造與自動(dòng)化技術(shù)的制高點(diǎn)，許多國家提出了跨世紀(jì)的研究計(jì)劃。例如，美國政府提出了《美國國家關(guān)鍵技術(shù)》、《先進(jìn)制造技術(shù)計(jì)劃》、《敏捷制造與制造技術(shù)計(jì)劃》和《下一代制造（NGM）》等計(jì)劃；在歐共體的《尤里卡計(jì)劃（EURE－KA）》、《信息技術(shù)研究發(fā)展戰(zhàn)略計(jì)劃（ESPRIT）》和《第五屆框架研究計(jì)劃》中，與先進(jìn)制造技術(shù)有關(guān)的項(xiàng)目占有相當(dāng)大的比重；德國政府提出了《制造2000計(jì)劃》、《微系統(tǒng)2000計(jì)劃》和《面向未來的生產(chǎn)》等計(jì)劃；日本的《智能制造系統(tǒng)計(jì)劃》、《極限作業(yè)機(jī)器人研究計(jì)劃》、《微機(jī)器研究計(jì)劃》和《仿人形機(jī)器人研究計(jì)劃》；英國的《國家納米技術(shù)計(jì)劃》（NION）；韓國的《高級先進(jìn)技術(shù)國家計(jì)劃》（G7計(jì)劃）等。這些國家均將先進(jìn)制造與自動(dòng)化技術(shù)列為重要研究內(nèi)容。通過政府、企業(yè)、大學(xué)和科研院所的合作實(shí)施，這些計(jì)劃大大促進(jìn)了先進(jìn)制造與自動(dòng)化技術(shù)的發(fā)展。 近10多年來，我國有關(guān)部門有計(jì)劃地部署了一系列國家級重點(diǎn)科技項(xiàng)目，有效地促進(jìn)了我國先進(jìn)制造與自動(dòng)化技術(shù)的研究與應(yīng)用推廣，如。科技部組織實(shí)施的863計(jì)劃的CIMS主題、智能機(jī)器人主題，“九五”國家科技攻關(guān)計(jì)劃的CAD應(yīng)用工程、精密制造技術(shù)開發(fā)與應(yīng)用、數(shù)控技術(shù)與裝備、現(xiàn)場總線控制技術(shù)開發(fā)與應(yīng)用、工業(yè)機(jī)器人應(yīng)用、激光技術(shù)應(yīng)用等重點(diǎn)項(xiàng)目；總裝備部（原國防科工委）在“九五”期間，組織實(shí)施了我國武器裝備先進(jìn)制造技術(shù)的發(fā)展項(xiàng)目；航空。航天、兵器和機(jī)械等許多行業(yè) 和部門在“九五”期間組織實(shí)施了行業(yè)先進(jìn)制造技術(shù)項(xiàng)目；國家計(jì)委、經(jīng)貿(mào)委等部委在用高技術(shù)改造傳統(tǒng)產(chǎn)業(yè)方面也推行了一系列計(jì)劃。上述計(jì)劃和項(xiàng)目極大地推動(dòng)了我國先進(jìn)制造與自動(dòng)化技術(shù)的發(fā)展。 綜觀各國先進(jìn)制造與自動(dòng)化技術(shù)計(jì)劃的制定和實(shí)施情況可以看到，先進(jìn)制造和自動(dòng)化技術(shù)的發(fā)展有其深刻的國際經(jīng)濟(jì)競爭背景。這些先進(jìn)制造與自動(dòng)化技術(shù)計(jì)劃提出時(shí)，即以提高本國制造業(yè)的國際競爭能力、促進(jìn)經(jīng)濟(jì)增長和提高國家綜合實(shí)力為目標(biāo)，既注重技術(shù)的超前性，更重視來自產(chǎn)業(yè)界的實(shí)際需求；在關(guān)鍵技術(shù)的選擇上注重系統(tǒng)集成技術(shù)與工藝裝備研究開發(fā)并重，通過系統(tǒng)技術(shù)、信息技術(shù)和自動(dòng)化技術(shù)的引入，提高制造企業(yè)的競爭能力；同時(shí)也可以看到，各國在發(fā)展先進(jìn)制造與自動(dòng)化技術(shù)的過程中，政府通過若干計(jì)劃的實(shí)施起到了關(guān)鍵的引導(dǎo)和調(diào)控作用，并形成了一套有效的研究開發(fā)及推廣應(yīng)用的管理機(jī)制和創(chuàng)新機(jī)制。 4 先進(jìn)制造與自動(dòng)化技術(shù)重大發(fā)展方向 目前制造業(yè)正在從以機(jī)器為特征的傳統(tǒng)技術(shù)時(shí)代向著以信息為特征的系統(tǒng)技術(shù)時(shí)代邁進(jìn)，進(jìn)入了一個(gè)能夠增強(qiáng)企業(yè)在不可預(yù)見的多變環(huán)境中生存能力的全球化敏捷制造階段。合理開發(fā)利用資源、保護(hù)生態(tài)環(huán)境、實(shí)現(xiàn)經(jīng)濟(jì)一社會(huì)相互協(xié)調(diào)的可持續(xù)發(fā)展戰(zhàn)略和綠色制造成為全社會(huì)的共識(shí)。今后15年制造技術(shù)的發(fā)展將超過以往的75年。當(dāng)前先進(jìn)制造與自動(dòng)化技術(shù)發(fā)展的主要特點(diǎn)是產(chǎn)品設(shè)計(jì)制造和企業(yè)管理的信息化、生產(chǎn)過程控制的智能化、生產(chǎn)裝備的數(shù)字化和機(jī)器人的與人和諧化。 4.1　產(chǎn)品設(shè)計(jì)制造和企業(yè)管理的信息化 信息技術(shù)在制造業(yè)中的廣泛應(yīng)用，促進(jìn)了產(chǎn)品設(shè)計(jì)制造和企業(yè)管理信息化程度的提高，改變了現(xiàn)代制造企業(yè)的產(chǎn)品設(shè)計(jì)、產(chǎn)品制造和管理模式。以并行工程、虛擬制造為代表的信息技術(shù)的應(yīng)用提高了創(chuàng)新產(chǎn)品的設(shè)計(jì)制造水平，以敏捷制造、動(dòng)態(tài)聯(lián)盟、企業(yè)電子商務(wù)為代表的企業(yè)管理技術(shù)的應(yīng)用促進(jìn)了新型制造企業(yè)的迅速發(fā)展，形成了新型的跨國企業(yè)和基于供應(yīng)鏈的戰(zhàn)略企業(yè)聯(lián)盟。 4．2生產(chǎn)過程控制的智能化 生產(chǎn)過程的控制是典型的復(fù)雜大系統(tǒng)問題，提高生產(chǎn)過程的控制水平和生產(chǎn)效率是工業(yè)界急待解決的具有挑戰(zhàn)性的問題，采用智能化方法進(jìn)行生產(chǎn)過程控制是一個(gè)有前途的發(fā)展方向。采用智能化技術(shù)可以解決生產(chǎn)過程控制中存在的強(qiáng)耦合、非線性和不確定性問題，從而顯著提高生產(chǎn)效率和產(chǎn)品質(zhì)量。研制開發(fā)智能化的生產(chǎn)過程控制設(shè)備也是發(fā)展高新技術(shù)產(chǎn)業(yè)的重要基礎(chǔ)。 4．3生產(chǎn)裝備的數(shù)字化 信息技術(shù)的廣泛采用，提高了生產(chǎn)裝備的數(shù)字化程度，從而顯著提高了產(chǎn)品的高技術(shù)附加值。生產(chǎn)裝備的數(shù)字化不僅增強(qiáng)了產(chǎn)品的功能和集成能力，提高了產(chǎn)品的市場競爭力和經(jīng)濟(jì)效益，還顯著提高了產(chǎn)品的可操作性、可維護(hù)性，降低了產(chǎn)品的運(yùn)行和維護(hù)成本。發(fā)展高度數(shù)字化的生產(chǎn)裝備是制造企業(yè)贏得市場競爭的主要手段之一。 4．4機(jī)器人的與人和諧化 機(jī)器人集當(dāng)代眾多高技術(shù)于一身，特別強(qiáng)調(diào)人機(jī)和諧共存。人機(jī)和諧共存是機(jī)器人進(jìn)入人類未來工作和生活的基礎(chǔ)，已經(jīng)成為公認(rèn)的21世紀(jì)前沿高技術(shù)。目前重點(diǎn)研究的特種機(jī)器人有仿人形機(jī)器人、水下機(jī)器人、醫(yī)用機(jī)器人、服務(wù)機(jī)器人、網(wǎng)絡(luò)機(jī)器人、軍用機(jī)器人、農(nóng)林與農(nóng)副產(chǎn)品加工機(jī)器人等等，在航空、航天、能源、交通、海洋、生物、醫(yī)療、服務(wù)、農(nóng)業(yè)、軍事和娛樂等領(lǐng)域具有非常廣闊的應(yīng)用前景。 5　先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域擬解決的問題 “十五”863計(jì)劃先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域針對我國國民經(jīng)濟(jì)建設(shè)的主戰(zhàn)場的重大需求，瞄準(zhǔn)國際先進(jìn)制造與自動(dòng)化技術(shù)前沿，擬有重點(diǎn)地選擇能夠主導(dǎo)21世紀(jì)初期我國制造業(yè)發(fā)展和升級的關(guān)鍵技術(shù)和裝備，促進(jìn)形成我國先進(jìn)制造與自動(dòng)化技術(shù)產(chǎn)業(yè)的群體優(yōu)勢，提升我國制造業(yè)綜合競爭能力，實(shí)現(xiàn)制造業(yè)的跨躍式發(fā)展；擬有重點(diǎn)地選擇若干涉及國家安全的戰(zhàn)略必爭裝備和競爭前核心技術(shù)，實(shí)現(xiàn)局部領(lǐng)域的突破和跨越式發(fā)展，打破國外的技術(shù)封鎖，在國際相關(guān)高技術(shù)領(lǐng)域占有一席之地。 5.1　制造業(yè)信息化工程關(guān)鍵技術(shù)的研究開發(fā)和集成應(yīng)用 面對經(jīng)濟(jì)全球化和信息化對我國制造業(yè)的挑戰(zhàn)和機(jī)遇，為了增強(qiáng)我國制造業(yè)的綜合競爭能力，“十五”期間，本領(lǐng)域擬在科技部開展的“制造業(yè)信息化工程”專項(xiàng)行動(dòng)中發(fā)揮關(guān)鍵作用。重點(diǎn)解決制造業(yè)信息化急需的關(guān)鍵技術(shù)及支撐系統(tǒng)平臺(tái)，主要包括：基于三維產(chǎn)品模型的CAD／CAE/CAPP/CAM/PDM系統(tǒng)，流程工業(yè)MES／PCS系統(tǒng)，基于中國先進(jìn)管理模式的ERP和電子商務(wù)系統(tǒng)，支持整體解決方案的PLM系統(tǒng)，支持制造協(xié)同、資源共享與集成服務(wù)的區(qū)域制造網(wǎng)絡(luò)系統(tǒng)等。通過支持技術(shù)產(chǎn)品的開發(fā)和典型示范應(yīng)用，促進(jìn)相關(guān)軟件產(chǎn)品的產(chǎn)業(yè)化，為制造業(yè)信息化工程提供技術(shù)支撐。 5．2戰(zhàn)略必爭裝備和競爭前核心技術(shù)的研究開發(fā) “十五”期間，本領(lǐng)域擬選擇若干迫切需要解決的戰(zhàn)略必爭技術(shù)與裝備和競爭前核心技術(shù)進(jìn)行重點(diǎn)開發(fā)，主要包括：開發(fā)擁有自主知識(shí)產(chǎn)權(quán)的7 000m深海載人潛器，提供深?？辈熳鳂I(yè)技術(shù)裝備，為使我國贏得“藍(lán)色圈地運(yùn)動(dòng)”的主動(dòng)權(quán)做出貢獻(xiàn)；突破數(shù)據(jù)庫管理系統(tǒng)（DBM）關(guān)鍵技術(shù)，形成自主產(chǎn)權(quán)的、能與主流產(chǎn)品相抗衡的DBM核心系統(tǒng)與應(yīng)用套件，為我國信息化工程和信息安全提供支撐；掌握一批微機(jī)電系統(tǒng)（MEM）的關(guān)鍵技術(shù)，取得自主知識(shí)產(chǎn)權(quán)，并開發(fā)出若干MEMS器件及微系統(tǒng)，為MEMS在未來形成產(chǎn)業(yè)打下良好的基礎(chǔ)；突破傷人形機(jī)器人系統(tǒng)中的關(guān)鍵技術(shù)，研制具有自主知識(shí)產(chǎn)權(quán)的國際先進(jìn)水平的仿人形機(jī)器人，奠定仿人形機(jī)器人應(yīng)用的基礎(chǔ)，促進(jìn)人工智能、傳感等技術(shù)的發(fā)展。 5．3基礎(chǔ)制造裝備與成套裝備的研究開發(fā) “十五”期間，本領(lǐng)域擬重點(diǎn)選擇若干基礎(chǔ)制造裝備和成套裝備進(jìn)行開發(fā)，實(shí)現(xiàn)產(chǎn)業(yè)化，主要包括：以中檔精切類數(shù)控機(jī)床裝備的產(chǎn)業(yè)化作為切人點(diǎn)，掌握數(shù)控裝備關(guān)鍵技術(shù)，塑造中國數(shù)控機(jī)床品牌，提高市場占有率；根據(jù)國防工業(yè)的具體需求，設(shè)計(jì)制造高精尖精密加工裝備，打破國外封鎖；通過整機(jī)帶動(dòng)相關(guān)的機(jī)床設(shè)計(jì)技術(shù)，系統(tǒng)與伺服、高附加值關(guān)鍵部件以及配套工具的技術(shù)創(chuàng)新，全面提升國家基礎(chǔ)制造裝備的核心競爭力；支持典型的成套工程機(jī)械產(chǎn)品的信息化、智能化研究開發(fā)和示范應(yīng) 用，促進(jìn)我國工程機(jī)械產(chǎn)品的升級換代，提高國際競爭力；研制適應(yīng)我國典型土層的6．3m全斷面隧道掘進(jìn)機(jī)，進(jìn)行實(shí)際應(yīng)用，掌握自主知識(shí)產(chǎn)權(quán)的全斷面隧道掘進(jìn)機(jī)關(guān)鍵技術(shù)，制定相關(guān)的標(biāo)準(zhǔn)和規(guī)范體系，提高國產(chǎn)全斷面隧道掘進(jìn)機(jī)的市場占有率。 5．4先進(jìn)制造與自動(dòng)化前沿創(chuàng)新技術(shù)的研究 “十五”期間，本領(lǐng)域擬支持一批以原始創(chuàng)新和取得具有自主知識(shí)產(chǎn)權(quán)為目的的前沿創(chuàng)新技術(shù)課題研究。擬在數(shù)字化設(shè)計(jì)與制造、過程自動(dòng)化、企業(yè)管理與電子商務(wù)、現(xiàn)代集成制造系統(tǒng)平臺(tái)、制造工藝與裝備、特種機(jī)器人、基礎(chǔ)部件與系統(tǒng)等7個(gè) 方面推進(jìn)前沿創(chuàng)新技術(shù)的研究，為先進(jìn)制造與自動(dòng)化技術(shù)的可持續(xù)發(fā)展與創(chuàng)新跨越奠定技術(shù)基礎(chǔ)。 6　先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域總體戰(zhàn)略目標(biāo)與布 6.1　總體戰(zhàn)略目標(biāo) 總體戰(zhàn)略目標(biāo)包括：(1)面向國民經(jīng)濟(jì)建設(shè)主戰(zhàn)場和先進(jìn)制造與自動(dòng)化技術(shù)發(fā)展前沿，結(jié)合重大工程和產(chǎn)品，積極推進(jìn)具有椰沿性。前瞻性和戰(zhàn)晗性的高技術(shù)研究，形成有原始創(chuàng)新的理論方法、有知識(shí)產(chǎn)權(quán)的成果和技術(shù)儲(chǔ)備，取得發(fā)明專利、專利受理和軟件著作權(quán)登記500項(xiàng)以上；(2)力爭在制造業(yè)信息化、深海載人潛器微機(jī)電系統(tǒng)（MEMS）、數(shù)據(jù)庫管理系統(tǒng)（EBMS）。仿人形特種機(jī)器人、智能化工程機(jī)械和全斷面隧道掘進(jìn)機(jī)（盾構(gòu)）等對提升我國制造業(yè)競爭力有重大影響的共性技術(shù)與裝備以及戰(zhàn)略必爭裝備和競爭前核心技術(shù)方面研發(fā)出一批具有自主知識(shí)產(chǎn)權(quán)的創(chuàng)新產(chǎn)品：(3)在重點(diǎn)行業(yè)、典型區(qū)域、試點(diǎn)省市和骨干企業(yè)進(jìn)行集成示范應(yīng)用，產(chǎn)生顯著的經(jīng)濟(jì)效益，提高我國制造業(yè)競爭力；(4)仿委立先進(jìn)制造與自動(dòng)化技術(shù)戰(zhàn)略研究體系、咨詢服務(wù)體系和研究開發(fā)基地，培養(yǎng)一批高水平拔尖人才，全面實(shí)施人才戰(zhàn)略、專利戰(zhàn)略與標(biāo)準(zhǔn)戰(zhàn)略。 6.2戰(zhàn)略布局 a．先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域由現(xiàn)代集成制造系統(tǒng)技術(shù)和機(jī)器人技術(shù)2個(gè)主題組成?，F(xiàn)代集成制造系統(tǒng)技術(shù)主題的主要任務(wù)是：突破一批戰(zhàn)略性、前沿性和前瞻性的現(xiàn)代集成制造技術(shù)，開發(fā)一批具有自主知識(shí)產(chǎn)權(quán)的應(yīng)用軟件系統(tǒng)，以若干重大行業(yè)和典型區(qū)域的集成應(yīng)用為突破口，推進(jìn)制造業(yè)信息化工程。機(jī)器人技術(shù)主題的主要任務(wù)是：研究開發(fā)具有戰(zhàn)略性、前沿性和前瞻性的機(jī)器人和自動(dòng)化工藝裝備中的核心技術(shù)，在深海載人潛器、微機(jī)電系統(tǒng)和特種機(jī)器人等方面取得突破，為我國的可持續(xù)發(fā)展做出貢獻(xiàn)，促進(jìn)中高檔數(shù)控裝備和大型工程機(jī)械等關(guān)鍵基礎(chǔ)裝備的產(chǎn)業(yè)化，提高制造企業(yè)的生產(chǎn)能力和市場競爭力。 b．先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域的研究發(fā)展工作在內(nèi)容上可分成前沿創(chuàng)新技術(shù)研究、產(chǎn)品研發(fā)與產(chǎn)業(yè)化、集成應(yīng)用示范Xi程3個(gè)層次。前沿創(chuàng)新技術(shù)研究以探索技術(shù)前沿為主要目標(biāo)，鼓勵(lì)原始創(chuàng)新，取得具有自主知識(shí)產(chǎn)權(quán)的技術(shù)成果；產(chǎn)品研發(fā)與產(chǎn)業(yè)化以關(guān)鍵產(chǎn)品的研發(fā)與產(chǎn)業(yè)化為重要目標(biāo)，開發(fā)一批對提高我國企業(yè)競爭力有重大作用的技術(shù)和裝備，以及戰(zhàn)略必爭裝備和競爭前核心技術(shù)；集成應(yīng)用示范工程面向我國重點(diǎn)行業(yè)和典型區(qū)域，利用先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域研發(fā)的關(guān)鍵技術(shù)和產(chǎn)品，實(shí)施重大集成應(yīng)用，取得顯著的經(jīng)濟(jì)效益和社會(huì)效益。 C．先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域的發(fā)展戰(zhàn)略目標(biāo)充分體現(xiàn)了“創(chuàng)新跨越，精簡聚焦”的精神。在2O01年8月第一次戰(zhàn)略目標(biāo)論證會(huì)后，先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域先后召開了2次有地方、部門。行業(yè)及領(lǐng)域、主題專家參加的戰(zhàn)略目標(biāo)研討會(huì)，逐步明確了先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域以信息化帶動(dòng)工業(yè)化，推進(jìn)制造業(yè)信息化的工作主線，并將先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域的主要工作內(nèi)容整合到科技部“制造業(yè)信息化關(guān)鍵技術(shù)研究及應(yīng)用示范工程”（簡稱“制造業(yè)信息化工程”）重大專項(xiàng)中。制造業(yè)信息化工程將通過信息技術(shù)、自動(dòng)化技術(shù)、現(xiàn)代管理技術(shù)等與制造技術(shù)相結(jié)合，帶動(dòng)產(chǎn)品的設(shè)計(jì)制造方法和工具創(chuàng)新、企業(yè)管理模式的創(chuàng)新、企業(yè)間協(xié)作關(guān)系的創(chuàng)新，實(shí)現(xiàn)產(chǎn)品設(shè)計(jì)制造和企業(yè)管理的信息化、生產(chǎn)過程控制的智能化、生產(chǎn)裝備的數(shù)字化、社會(huì)服務(wù)和咨詢的網(wǎng)絡(luò)化，實(shí)現(xiàn)用信息技術(shù)改造我國傳統(tǒng)產(chǎn)業(yè)和以信息化帶動(dòng)工業(yè)化，促進(jìn)提升我國制造業(yè)的綜合競爭能力。 d．先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域?qū)⒏鶕?jù)國際先進(jìn)制造與自動(dòng)化技術(shù)的最新發(fā)展動(dòng)向和國家的實(shí)際需求，動(dòng)態(tài)地調(diào)整領(lǐng)域的布局和研究內(nèi)容。為此先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域?qū)l(fā)展戰(zhàn)略研究作為一項(xiàng)長期的任務(wù)來抓，組織專門的戰(zhàn)略研究小組，不斷調(diào)整先進(jìn)制造與自動(dòng)化技術(shù)領(lǐng)域規(guī)劃，本領(lǐng)域的布局和課題的設(shè)置更切合實(shí)際。 科技譯文 Improved Workpiece Location Accuracy Through Fixture Layout Optimization Abstract Inaccuracies in workpiece location lead to errors in position and orientation of a machined feature on the workpiece. The ability to accurately locate a workpiece in a machining fixture is strongly influenced by rigid body displacements of the workpiece caused by elastic deformation of loaded fixture-workpiece contacts. This paper presents a model for improving workpiece location accuracy in fixturing. A discrete elastic contact model is used to represent each fixture-workpiece contact. Reduction in workpiece locating error due to rigid body displacements is achieved through optimal placement of locators and clamps around the workpiece. The layout optimization model is also shown to improve the overall workpiece deflection and reaction force characteristics. 1.Introduction The accuracy of location of a machined feature depends on the machining fixture’s ability to precisely locate the workpiece relative to the machine tool axes. Workpiece location in a fixture is significantly influenced by localized elastic deformation of the workpiece at the fixturing points. These deformations are caused by the clamping force(s) applied to the workpiece. For a relatively rigid workpiece the localized elastic deformations cause it to undergo rigid body translations and rotations which alter its location with respect to the cutting tool. It is therefore important to minimize such effects through optimal design of the fixture layout. Previous work in fixture layout optimization has focused on the use of finite element and rigid body models. Menassa and DeVries [1], Rearick et al. [2], Trappey et al. [3], and Cai et al [4] used finite element models of the fixture-workpiece system as input to the layout optimization. In these works the fixture layout design is formulated as a constrained nonlinear optimization problem. The goal is to determine the positions of locator-clamp pairs that will minimize a nonlinear function of the elastic deformation at selected points on the workpiece. Such a formulation requires solution of the complete finite element model during each iteration of the optimization process. Hence, the technique is computationally intensive. DeMeter [5] presented a min-max algorithm to determine the optimal fixture layout and clamping force intensity that minimizes the maximum contact force. In this study the workpiece and fixture were assumed to be perfectly rigid. Such a formulation does not allow the effect of workpiece displacement on locating errors to be minimized directly. Recently, Gui et al [6] reported a model for improving workpiece location accuracy by optimizing the clamping force. They model the elasticity of fixtureworkpiece contacts using linear springs of known stiffness. However, methods for determining the contact stiffness are not addressed. In addition, the fixture layout is assumed fixed for a given workpiece and cutting force system. This paper presents a method that directly minimizes workpiece location errors due to localized elastic deformation of the workpiece at the fixturing points by optimally placing the locators and clamps around the workpiece. The method considers the fixtureworkpiece contact to be linearly elastic and uses closed-form contact stiffness models derived from well-known contact mechanics problems. Also, the method outlined here is computationally less intensive than the finite element approach. The following sections give details of the underlying models and constraints used to formulate the fixture layout optimization procedure. Model simulations are presented to demonstrate the ability of the method to minimize workpiece location errors through optimal arrangement of locators and clamps. 2.Fixture Layout Optimization Fixture layout optimization requires formulation of an objective function and constraints. In this paper our objective is to minimize the effect of localized elastic deformation of the workpiece at the fixturing points on workpiece location. As stated earlier, the elastic deformations cause the workpiece to undergo a rigid body motion, which in turn shifts the workpiece location. The objective function for optimization is constructed as follows. Objective Function Formulation. Consider a solid rectangular workpiece held in a fixture consisting of several locators and clamps (see Figure 1). The fixture is typically very rigid compared to the workpiece. It can hence be assumed that the locators do not undergo any rigid body displacement. In contrast, forces acting on the workpiece at the locating and clamping points cause the workpiece to translate and rotate in the global coordinate system. Assume that the rigid body motion of the workpiece due to normal and tangential elastic deformations at the ith fixturing point is given by vector δ i=[δ δ δ ] xiyizi T . Note that the components of δ i are expressed in the local coordinate system fixed to the ith point. Geometric transformations are applied so that the rigid bodymotion due to deformation at the ith fixturing point is expressed in the global coordinatesystem as: where Tgi is a general rotation matrix that transforms quantities expressed in the ith local coordinate system into the global coordinate system. Thus, the total rigid body motion ofthe workpiece due to elastic deformations at all the fixturing points is: where N is the total number of locators and clamps. In order to minimize the effect of rigid body motion on workpiece location, a quadratic objective function for fixture layout optimization can now be formulated as follows: Note that the above expression is not an explicit function of the fixture element positions.But the rigid body motion δ i , and therefore Δ , is dependent on the fixturing forces which are in turn uniquely determined by the layout of fixturing points and elastic contact properties. Hence, changing the fixture layout changes the value of the objective function indirectly. Fixture-Workpiece Contact Constraints. The fixture-workpiece system is subject toseveral contact constraints that the optimum fixture layout must also satisfy. In particular, constraints specifying the geometric compatibility of elastic deformation andfrictional resistance are needed. These constraints are developed using a discrete elasticcontact modeling approach similar to that of Conry and Seireg [7], and Sinha and Abel[8]. The workpiece is assumed to be elastic in the contact region and rigid elsewhere.The fixture is assumed to be completely rigid. At each fixturing point a square contact surface tangent to the fixture and workpiece surfaces is assumed. The contact surface isdiscretized into a grid containing M square elements as shown in Figure 2. A distributed normal force of intensity p ji and a distributed friction force of intensity (q) (q) xjiyj2 i 2 +are assumed to act across an arbitrary element j of the ith contact surface. The total normal ( Pi ) and friction (Qi ) forces acting at the ith fixturing point are then given by: The localized deformation at a fixturing point causes distant points in the workpiece to undergo a rigid body motion in the normal direction given by δ zi . If s ji isthe initial separation of the fixture and workpiece surfaces for the jth element at the ith fixturing point, the normal deformation, wji , must satisfy the following contact condition[9]: The equality sign applies to points that lie inside the equilibrium contact area and the inequality sign for outside points. Orthogonal components of tangential deformation, uji and v ji , produced by the frictional forces acting at a fixturing point lead to tangential rigid body motions δ δ xiy, i ,respectively. The deformation and rigid body motion should satisfy the following geometric compatibility conditions [9]: where the equality and inequality signs apply for slip and no slip cases, respectively. Contact Deformation Model.The workpiece is assumed to be a linear elastic solid in the vicinity of the fixturing points. Hence, by linear superposition, the normal deformation in the jth element of the ith contact region can be written as: where e e e jknjkxjk, , y are the flexibility influence coefficients for deformation in the normal direction due to fixturing forces in the normal (n) and tangential directions (x, y).Similarly, the x and y components of tangential deformation are given by: where are the normal and tangential flexibility influence coefficients for workpiece deformation in the local x and y directions at the ith fixturing point, respectively. In this paper the influence coefficients are derived from closed-form solutions for the contact compliance of an elastic half-space subjected to distributed normal and tangential loads. Details of the influence coefficient models may be found in [8, 9]. Contact Friction Constraint. Coulomb friction is assumed to apply at each fixturing point. This implies a nonlinear relation between the normal and frictional forces acting at a fixturing point, i.e., (q) (q) p xj where μ s is the coefficient of static friction for the fixture-workpiece material pair. For simplicity, a linearized version of this constraint is used: Static Equilibrium Constraint. The workpiece must be in static equilibrium after application of fixturing forces at the selected points. This constraint is given by the following force and moment equilibrium equations: ΣF = 0 (12) ΣM = 0 (13) where the forces and moments are expressed in terms of the elemental normal ( p ji ) and tangential forces ( qxji , qyji ) acting at the contact surface for each fixturing point. Clamping Force Constraint. When the clamping force applied by the clamps isspecified, it is necessary that the sum of the elemental normal forces at the clampingpoint equal the specified force. This constraint is expressed as follows: where C is the number of clamps in the fixture. In this paper the clamping force isassumed to be known. In general however the clamping force could be treated as adesign variable in the layout optimization process [5]. Fixture Element Position Constraints. The fixture layout optimization procedure seeksto find the optimal locations of the fixturing points. In general, fixture element positionson a workpiece datum surface cannot be chosen randomly and are often constrained bythe geometric complexity of the workpiece surfaces, size and location of the features tobe machined, and other process related issues. Hence, the position of a fixture element isrestricted to a bounded region on the datum surface. In this paper each fixture elementposition is constrained to lie inside a convex polygonal region. A sequence of orderedstraight edges represents each convex polygon. Mathematically, the system of linearinequalities constructed from the line equations for all ordered edges (for N fixturingpoints) is used to specify the bounded region: A X C p p p ≤ (15) Where And The elements of Ai and ci are coefficients of the line equations of the polygon edges usedto specify the polygon boundary for the ith point, xi is the position vector (global) to the ithpoint on the workpiece surface, and li is the number of ordered edges making up thebounding polygon for the ith point.The above inequalities can now be used to easily establish the location of afixturing point relative to its polygon boundary. Points inside or on the boundarycompletely satisfy the above inequalities whereas points outside the bounded region do not [10]. Layout Optimization Model. The complete fixture layout optimization problem cannow be formally stated as follows: Minimize ： Subject to: Bounds: pji ≥ 0 i = 1, …, N; j = 1, …, M; k = 1, …, C Note that the normal compatibility constraint has been multiplied by -1 to convert it intoa ≤ type inequality. Also, by definition, the friction force components qxji and qxji lie inthe contact surface plane, and p ji is assumed to be positive when directed into the9workpiece surface. 3.Solution Method A nonlinear programming method is used to solve the above layout optimizationproblem. Specifically, Zoutendijk’s method of feasible direction [11] is used. Thismethod is similar to that used by DeMeter [5] and involves the solution of the followinggeneral nonlinear program: Minimize f(x) Subject to Gx ≤ b (linear inequality constraint) H(x) = 0 (nonlinear equality constraint) Ex = e (linear equality constraint) where x is the feasible solution. For the nonlinear program given in equation (16) the solution x =[F δ X ] pT where: Note that in addition to position of the fixturing points, Xp, the solution procedure treats the fixturing forces F and rigid body motion δ also as design variables during theoptimization process. This is because the fixturing forces and rigid body motion dependon the fixture layout and are determined uniquely for each layout by the physics of theproblem. The first linear inequality constraint is constructed by combining all the inequality constraints given in equation (16). The second nonlinear constraint arises from themoment equilibrium equation in (16). Finally, the linear equality constraint equation isconstructed by combining all the equality constraints listed in (16). For the problem athand, G, H, and E result in matrices with the following sizes: [(4MN+N liiN= Σ1) x(3MN+6N)], [3 x (3MN+6N)], and [(3+C) x (3MN+6N)]. Note that x is a [(3MN+6N) x1] column vector. The method of feasible directions solves the nonlinear program by moving from a initial feasible solution to an improved feasible solution. This is accomplished in four steps: a) find initial feasible solution, b) determine line search direction, c) determine step size, d) solve quadratic program. By iterating between steps (b) and (d) furtherimprovements in the feasible solution can be obtained. Mathematical details of step (b)through (d) can be found in reference [11]. The initial feasible solution x is obtained by solving the elastic fixture-workpiececontact model for the initial layout. This is done by minimizing the total complementaryenergy for the fixture-workpiece system. Details of the solution procedure andexperimental validation can be found in [7, 8, 12]. Note that the contact model needs tobe solved only once at the beginning to obtain the initial feasible solution. Thereafter,the layout optimization model relies on the contact constraints and the contactdeformation model to compute valid rigid body displacements and fixturing forces. 4.Results and Discussion The fixture layout optimization model and solution algorithm has been implemented in MATLAB (version 5.0). The capability of the model is illustrated through an example. Consider the initial fixture layout shown in Figure 3. This layout uses a "4-2-1" location scheme with two simultaneously actuated hydraulic clamps to hold the workpiece against the locators. Table 1 lists the positions and orientations of thefixture elements in the initial layout. Locators L1-L4 and clamps C1-C2 have sphericaltips while locators L5-L7 have small area planar tips (area = 63 mm2). A clamping forceof 703 N is assumed to act at each clamping point. The workpiece is a 127mm x 127mmx 382 mm block of Aluminum 7075-T6. The Young's modulus (E) and Poisson’s ratio(ν) for the workpiece are 70.3 GPa and 0.354 respectively, and 201 GPa and 0.296respectively for the fixture elements. The initial feasible solution vector x is computed by solving the fixture-workpiececontact model for the initial fixture layout using the minimum complementary energymethod. The layout optimization problem is then solved using the four step iterationprocedure outlined in the previous section. The fixture element position constraints usedfor this problem are given in Table 2. The improved fixture layout that minimizes the11effects of rigid body motion is given in Table 1. The objective function value is reducedfrom 528 μm2 to 426 μm2. The impact of the optimization process on the fixture layout is shown in Figure 4.The initial fixture layout was intentionally designed to violate well-known empirical“l(fā)ocating rules” [13]. For instance, it is standard practice to position the locators on adatum surface as far apart as possible. This is done to ensure the best possible locationalstability of the workpiece. In the initial layout, locators L1-L2 and L4-L7 clearly do notsatisfy this rule. Also, the initial position of clamps C1 and C2 do not provide adequateclamping stability. It is clear from Figure 4 and Table 1 that the layout optimizationmodel gives a solution that supports the empirical rules. Specifically, L1 and L2 arepushed as far apart as possible. Also, locators L4-L7 are spread out on the primarydatum plane so as to include the projected center of gravity of the workpiece inside thebounding polygon formed by joining L4-L7. This improves workpiece stability in thefixture. The new position of clamp C1 is approximately half-way between locators L1and L2. Similarly, clamp C2 and locator L3 directly oppose each other in the improved lay out. If, for simplicity, only the normal component of rigid body motion ( δ z ) isconsidered, it can be shown through suitable geometric transformations that the locationerror, Ep, of a point P on the workpiece is reduced by the optimization process surface(see Figure 5). For instance, the location error of the point (30, 100, 19.1) decreases from15.3 μm for the initial fixture layout to 11.7 μm for the improved layout. Thus, thefixture layout optimization model and solution procedure described above improve workpiece location accuracy by minimizing the effect of workpiece rigid bodydisplacement. Finite Element Analysis. In order to further analyze the effect of the fixturelayout optimization process on overall workpiece deformation a finite element model wasconstructed using ANSYS? (version 5.3). The locators were modeled as displacementconstraints that prevent workpiece translation in the normal direction. The clampingforce was modeled as a uniformly distributed force acting over the workpiece-clampcontact area. The deflection of the top surface of the workpiece (i.e., the surface to bemachined) is shown for the initial and improved fixture layouts in Figures 6 and 7,respectively. The initial fixture layout shows a significant deflection gradient across thetop surface of the workpiece. Deflection magnitudes range from 0.25 x 10-4 mm to 0.76 x10-2 mm. In general a large variation in deflection magnitudes is not desirable. On theother hand, the improved fixture layout produces a relatively uniform distribution ofdeflections that range from 0.10 x 10-2 mm to 0.19 x 10-2 mm. The maximum deflectionof the top surface is much less for the improved layout (0.19 x 10-2 mm compared to 0.76x 10-2 mm). Also, the reaction forces at L1 and L2 are 638.05 N and 65.31 Nrespectively for the initial layout, and 327.20 N and 376.16 N respectively for theimproved layout. Thus reaction forces in the improved layout are more uniformlydistributed than the initial layout. Therefore the optimization process produces a fixture layout that improves theoverall workpiece deflection and reaction force characteristics in addition to improvingworkpiece location accuracy. 5.Conclusions The paper presented a fixture layout optimization model for improving thelocation accuracy of the workpiece when clamped in a machining fixture. Theinaccuracy in workpiece location was due to rigid body motion of the workpieceproduced by the localized elastic deformation at the fixturing points. A discretizedelastic contact model of the fixture-workpiece interaction was used to develop t