【正文】 he 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 . 22 5 Illustrating for Fixture Design by CBR This is a work piece (). 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 work 23 piece is show n in . Through searching, and calculating the similarity, the case index code of the most similar case is 19325513321402020, and the detailed information is show n in Tab. 3. The similarity is calculated as follows: 24 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 . 25 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 19325513311402020. 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。這個發(fā)展的標(biāo)準(zhǔn)系統(tǒng)，用于航空項目，幫助夾具設(shè)計者提高設(shè)計效率和重新使用先前的設(shè)計資源。 9 圖 3 需要設(shè)計夾具的一個工件 （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。 (3)如果一個新的事例和任何一個存在的事例族不一致，一個新的事例族將會自動產(chǎn)生，并作為標(biāo)準(zhǔn)事例保存到事例庫中。如果它有價值的話，設(shè)計者在保存之前必須分析一下，看看這個事例是否作為標(biāo)準(zhǔn)事例或參考事例被存儲了。一個方法是建立數(shù)值。 (3)整理相似尺寸的次序，最大的架子是最類似的事例。所以成分事例圖書館應(yīng)記錄特殊參數(shù)和保持它們的方法。事例的描述是基于事例推理的最重要的問題之一。 前 13 位數(shù)代表 13 個特征。同時 ,提出了基于知識引導(dǎo)的夾具事例檢索算法 ,以及事例的修改和采用同族事例碼進行相似事例的存貯 ,形成了基于事例推理的夾具設(shè)計 .所開發(fā)的原型系統(tǒng)在型號工程夾具設(shè)計等項目的設(shè)計過程中得到了應(yīng)用 ,并取得了令人滿意的使用效果 . 關(guān)鍵詞 : 基于事例的推理 夾具設(shè)計 CAD 夾具是以確定工件安全定位準(zhǔn)確為目的的裝置，并在加工過程中保持工件與刀具或機床的位置一致不變。 系統(tǒng)規(guī)定 :夾具的類型，工件的形狀，位置模式不能是 *和 ?。所以，整個夾具事例庫，成分事例庫，夾具的成分事例庫形成相同。首先在深度上查找，然后在寬度上；知識指導(dǎo)策略意味著在來自客觀事物根源的知識規(guī)則上查找，這就要首先查找固定類型，然后查找工件的形狀，第三查找定位方法。相似點的價值可以通過數(shù)字化的價值來計算，例如比較重量分別是 50kg 和 20kg 的工 件。如果有大量的相似事例，數(shù)值就應(yīng)該建的大一些。一個標(biāo)準(zhǔn)事例的最后三位通常是“ 000”。輸入有關(guān)工件的細節(jié)信息，建立事例索引碼，然后 CBR 開始依靠相似尺寸查找相似事例，選出最相似的事例。事例索引碼是19325523311402020。 puter aided design(CAD) Fixtures are devices that serve as the purpose of holding the work piece securely and accurately, and maintaining a consistent relationship with respect to the tools while machining. Because the fixture structure depends on the feature of the product and the status of the process planning in the enterprise, its design is the bottleneck during manufacturing, which restrains to improve the efficiency and leadtime. And fixture design is a plicated process, based on experience that needs prehensive qualitative knowledge about a number of design issues including work piece configuration, manufacturing processes involved, and machining environment. This is also a very time consuming work when using traditional CAD tools (such as Epigraphic, CATIA or Pro/E), which are good at performing detailed design tasks, but provide few benefits for taking advantage of the previous design experience and resources, which are precisely the key factors in improving the efficiency. The methodology of case based reasoning (CBR) adapts the solution of a previously solved case to build a solution for a new problem with the following four steps: retrieve, reuse, revise, and retain [1]. This is a more useful method than the use of an expert system to simulate human thought because proposing a similar case and applying a few modifications seems to be self explanatory and more intuitive to humans .So various case based design support tools have been developed for numerous areas[24], such as in injection molding and design, architectural design, die casting die design, process planning, and also in 15 f