【正文】 the prototype case and is distinguished by the different last three digits. From the concept that has been explained, the following strategies are adopted: 1) If a new case matches any existing case family, it has the same first 13 digits as an existing prototype case, so the case is not saved because it is represented well by the prototype case. Or is just saved as a reference case (the last 3 digits are not “ 000” , and not the same with others) in the case library. 2) If a new case matches any existing case family and is thought to be better at representing this case family than the previous prototype case, then the prototype 9 case is substituted by this new case, and the previous prototype case is saved as a reference case. 3) If a new case does not match any existing case family, a new case family will be generated automatically and the case is stored as the prototype case in the case library. 4 Process of CBR in Fixture Design According to the characteristics of fixture design, the basic information of the fixture design such as the name of fixture, part, product and the designer, etc. must be input first. Then the fixture file is set up automatically, in which all ponents of the fixture are put together. Then the model of the workpiece is input or designed. The detailed information about the workpiece is input, the case index code is set up, and then the CBR begins to search the analogical cases, relying on the similarity measure, and the most analogical case is selected out. If needed, the case is adapted to satisfy the current design, and restored into the case library. The flowchart of the process is shown in . 10 5 Illustrating for Fixture Design by CBR This is a workpiece (). Its material is 45 steel. Its name is seat. Its shape is block, and the product batch size is middle, etc. A fixture is turning fixture that serves to turn the hole, which needs to be designed. The value of feature, attribute, case index code and weight of the workpiece 11 is show n in . Through searching, and calculating the similarity, the case index code of the most similar case is 193255133214020xx, and the detailed information is show n in Tab. 3. The similarity is calculated as follows: 12 So the value of similarity measure of the fixture which needs to be designed with the most analogical case in case library is , and the structure of the most analogical case is shown in . After having been substituted the ponent, modified the locating model and clamp model, and adjusted the relative dimension, the new fixture is designed, and the figure is show n in . 13 As there is not the analogical fixture in the case library, the new fixture is restored in to the case library. The case index code is 193255133114020xx. 6 Conclusion CBR, as a problem solving methodology, is a more efficient method than an expert system to simulate human thought, and has been developed in many domains where knowledge is difficult to acquire. The advantages of the CBR are as follows: it resembles human thought more closely。因?yàn)閵A具的結(jié)構(gòu)依賴于產(chǎn)品的特點(diǎn)和在企業(yè)規(guī)劃中加工工序的地位 ,所以它的設(shè)計(jì)是制造過(guò)程中的瓶頸 ,制約著效率的提高 . 夾具設(shè)計(jì)是一個(gè)復(fù)雜的過(guò)程 ,需要有從大量的設(shè)計(jì)論文中了解質(zhì)量知識(shí)的經(jīng)驗(yàn)，這些設(shè)計(jì)論文包括工件的結(jié)構(gòu)設(shè)計(jì)、涉及加工工藝，和加工環(huán)境。 前 13 位數(shù)代表 13 個(gè)特征。在設(shè)計(jì)系統(tǒng)時(shí) ,三個(gè)項(xiàng)目的屬性信息沒(méi)有這些選擇 ,這就意味著必須選擇確定的屬性。事例的描述是基于事例推理的最重要的 16 問(wèn)題之一。整個(gè)夾具的設(shè)計(jì)資料通常是由工件資料和工件加工資料組成 ,這就意味著夾具的設(shè)計(jì)應(yīng)滿足特別功能的需求 .全部夾具事例是由功能成分組 成，它是用功能成分的名字和數(shù)字來(lái)進(jìn)行描述的。所以成分事例圖書(shū)館應(yīng)記錄特殊參數(shù)和保持它們的方法。例如，如果事例索引碼包括夾具類(lèi)型的磨削夾具，就只查找所有的磨削夾具，然后查找工件形狀的盒子，第三查找一個(gè)平面兩個(gè)銷(xiāo)的定位方法。 3） 整理相似尺寸的次序，最大的架子是最類(lèi)似的事例。非數(shù)字化的價(jià)值也能計(jì)算，例如，現(xiàn)在前13 位索引碼都是非數(shù)字化的價(jià)值。一個(gè)方法是建立數(shù)值。另外一個(gè)方法是只建立相似事例的數(shù)字（例如 10），這是類(lèi)型單里相似尺寸的最大值。如果它有 18 價(jià)值的話，設(shè)計(jì)者在保存之前必須分析一下，看看這個(gè)事例是否作為標(biāo)準(zhǔn)事例或參考事例被存儲(chǔ)了。一個(gè)參考事例屬于同族標(biāo)準(zhǔn)事例，最后三位用不同數(shù)字區(qū)分。 3）如果一個(gè)新的事例和任何一個(gè)存在的事例族不一致，一個(gè)新的事例族將會(huì)自動(dòng)產(chǎn)生，并作為標(biāo)準(zhǔn) 事例保存到事例庫(kù)中。如果需要的話，事例要滿足通用性設(shè)計(jì)，再存儲(chǔ)到事例庫(kù)中。 圖 3 需要設(shè)計(jì)夾具的一個(gè)工件 （最大尺寸 80mmx49mmx22mm） 工件的特征值，屬性值，事例索引碼和重量在表 1 中列出。 6 結(jié)論 基于事例推理，作為一個(gè)問(wèn)題解決的方法，是一個(gè)比模仿人類(lèi)思想的專(zhuān)業(yè)系統(tǒng)更有效的方法，已經(jīng)在 很多難獲取知識(shí)的領(lǐng)域里得到發(fā)展。這個(gè)發(fā)展的標(biāo)準(zhǔn)系統(tǒng)，用于航空項(xiàng)目，幫助夾具設(shè)計(jì)者提高設(shè)計(jì)效率和重新使用先前的設(shè)計(jì)資源。本次畢業(yè)設(shè)計(jì)是對(duì)我大學(xué)四年學(xué)習(xí)下來(lái)最好的檢驗(yàn)。 首先，我要特別感謝我的知道郭謙功老師對(duì)我的悉心指導(dǎo)，在我的論文書(shū) 寫(xiě)及設(shè)計(jì)過(guò)程中給了我大量的幫助和指導(dǎo)，為我理清了設(shè)計(jì)思路和操作方法，并對(duì)我所做的課題提出了有效的改進(jìn)方案。 其次，我要感謝大學(xué)四年中所有的任課老師和輔導(dǎo)員在學(xué)習(xí)期間對(duì)我的嚴(yán)格要求，感謝他們對(duì)我學(xué)習(xí)上和生活上的幫助，使我了解了許多專(zhuān)業(yè)知識(shí)和為人的道理，能夠在今后的生活道路上有繼續(xù)奮斗的力量。從這里走出，對(duì)我的人生來(lái)說(shuō)，將是踏上一個(gè)新的征程，要把所學(xué)的知識(shí)應(yīng)用到實(shí)際工作中去。四年的風(fēng)風(fēng)雨雨，我們一同 走過(guò)，充滿著關(guān)愛(ài)，給我留下了值得珍藏的最美好的記憶。老師們認(rèn)真負(fù)責(zé)的工作態(tài)度，嚴(yán)謹(jǐn)?shù)闹螌W(xué)精神和深厚的理論水平都使我收益