Abstract
近十年來，已經有許多研究投注於特徵技術(feature technologies) 的研究上，而且也穫得了許多重要的結論及新的觀念。然而，如何將這許多新的技術觀念加以整合，卻也成了今日刻不容緩的課題。本論文研究在此前題下，提出了特徵設計環境(feature-based environ- ment) 的觀念，作為整個研究的主要精神。在此環境中，相關的應用將會建立在共享的工件資料庫上，所以，如何將特徵資訊完整地表達出來，遂成為本研究的中心課題。論文中首先探討特徵設計的功能需求及相關的已發展技術，而後得到的結論為特徵表達架構為首先必須加以研究發展的部份。在這方面，本研究提出一新的特徵表示法，稱為 FDG(Feature Dependency Graph)。其中，形狀特徵可以以基本的構成要素定義出來，並可以用特徵的設計尺寸來驅動幾何性質。所以，特徵的擴充性及設計者意念的表達，皆可得到相當大的改進。而整個工件模型以維繫特徵間相互關係的圖狀結構表達，可以幫助應用程式快速、完整的獲得所需的特徵資訊。建立在 FDG模型的基礎上，本研究同時發展了工件設計模組及製程規劃系統。兩者皆藉助於專家系統之推理，以期更符合實務的需求。其中，整合專家系統於設計上，也提昇了特徵設計法的層次，是為未來特徵設計法繼續研究的一個重要方向。The functional requirements and methodologies being developedfor feature creation, feature editing and the applicationsbased on feature information are investigated first. Aconclusion is reached that a feature representation scheme tosupport explicit form feature information and inter-featurerelationships is essential for pro- viding a unified productdatabase within the "feature-based environment." The FDG(Feature Dependency Graph) scheme is therefore developed toenable efficient feature manipulation by a high-level graphstructure. It retains complete geometric information in the B-Rep level as well. Five basic constituents - B-Rep solidcomponent, measure entities, size, location and constraints -are used to define a single form feature. The scheme also helpsin extending the available fea- tures in the system bystructurally combining feature constituents. Furthermore, thescheme uses dimensions to represent form features' size andlocations. Therefore, the manipulation of form features isconsistent with the designer's intent. On the basis of FDGscheme, an architecture of design system for prismatic parts,in which an expert system shell is used to acquire knowledgefrom experienced designers, is proposed. The co- operation ofexpert systems and feature-based design systems can providesignificant advan- tages. A wide range of features' behavior isavailable during the product design and sound design decisionscan be made by the design sys- tem. The structure of knowledgebase for product design and the interface between the expertsys- tem shell and feature database are explained in detail.Finally, a CAPP system called OBPLAN is included in this thesisto complete a basic link of CAD and CAM.