标题: 以特征为基础之工作构建方法论
Feature-based Design Methodology for Part Modelling
作者: 张诏帆
Chang, Chao-Fan
彭德保
Perng, Der-Baau
工业工程与管理学系
关键字: 电脑辅助设计;特征为基础设计;组装树模式;关系图模式;CAD;Feture-based Design;Tree Model;Relational Graph Model
公开日期: 1995
摘要: 本论文在研究以特微为基础之工件构建方法论,并以所提出之方法论实做一操作简便的范例系统。本文中视特征为物件,并于实做系统中应用了物件导向的观念。此范例系统由三个子系统组成:(1)特征为基工件设计子系统;(2)特征基工件编辑系统;(3)特征为基组装件设计子系统。
(1)特徽为基工件设计子系统:本研究着眼于探讨具凹特征之方形工件设计,其中透过预先定义之三维凹特徽做设计及修改之基本元件。所提供的两组功能可使设计人员方便地构建及修改工件。特征为基之工件设计结果,则同时以构建式实体几何资料及零件边界资料表达方式存档。而此构建式实体几何资料之特微使本子系统不需透过繁复的特征辨认及抽取过程,即可轻易地与电脑辅助制程规划/电脑辅助制造系统整合。
(2)特征为基工件编辑子系统:本研究针对工件编辑时,特征交互作用情形(尤其是特征交集和特征包含)所产生的影响及对应解决方案的深入探讨;并以系统化的分析方式,推导出一套更新工件零边界资料及构式实体几何资料之法则,得以迅速有效地完成工件编辑后之资料更新动作,并保有最精简的工件特征资料。
(3)特征为基组装件设计子系统:此子系统具备了完整之零件/组装件设计、编辑功能;在易学易用的操作界面上,设计人员可透过本系统充分表达其设计理念。本计画利用“装配特征”的描述,可减化设计人员在零件定位之资料输入工作,及协助编辑工作之进行。所设计的组装件,分别以组装树及组装关系图来表达,除了易于构建外,也使得工件资料之编辑、更新更易达成。
本论文在工件构建理论,及在使设计人员简便修改工件理伭上均有相当贡献。所构建完成的工件特征资料更可成为电脑辅助设计及电脑辅助制造系统极佳的沟通界面。不谨单一工作可方便地由本研究所提出的方法论进行构建外,单一工作间更可透过彼此共有的特征资讯,以本文所提之电脑辅助定位方法快速地进行组装件之装配。
This dissertation is to study a feature-based design methodology for part modelling. A prototype system of the proposed methodology with user-friendly design environment is implemented. A feature is treated as an object in part modelling. The object-oriented concept is used in implementing the proposed system, including a feature-based part design subssytem, a feature-based part editing substem, and a feature-based assembly desin subsystem.
In the feature-based part design subsystem, this research focuses on the design of prismatic parts in which predefined 3D depression features, instead of low-level 2D lines and points are used as entities for representation and manipulation. Two special sets of functions are devised which enable designers to freely construct and modify the parts. The feature-based parts are saved in both CSG form and B-rep form. The feature-based CSG form allows the propos d 3D part design subsystem to be easily integrated into CAPP/CAM systems without complex feature-recognition and-extraction processes.
In the feature-based part editing subsystem, this research aims to address the issue about the problem of feature interaction, especially for enclosure and intersectionk among the modified feature and the other existing features. An efficient new approach to solving the feature interaction problem encountered in part-editing is thus proposed. A set of rules that facilitate updating the B-rep data and the feature-based representation of the part are devised. Such that, the B-rep data of the modified part can be updated efficiently and its feature list can be stored compactly. Moreover, the resulting part will be consistent with the designer's internt.
Finally, in the prototype feature-based assembly design subsystem, this research tries to propose full design and edit functions for individual parts and assemblies. Through the userfriendly interface, designers can easily implement their design intent. A new convenient method for computer-aided positioning parts in an assembly is presented. High-level entities of mating features and mating relations are used to describe the composed state of parts in an assembly. Both the tree model and the relational graph model are used to represent the assembly in the developed subsystem. An effecient algorithum of transforming the tree model of an assembly into its relational graph model is also presented. With this hybrid representation scheme and the computer-aided part positioning approach, the assembly can be modelled more easily with less input data; meanwhile, the related data for mating parts can be modified consistently and quickly.
This dissertation contributes to not only the construction aspects, but also the issue of enabling designers to modify feature models of existing parts conveniently. The created part feature models can be a well communication medium in CAD/CAM applications. Moreover, individual parts with feature information can be easily mated into an assembly model through the proposed computer-aided part positioning approach.
URI: http://140.113.39.130/cdrfb3/record/nctu/#NT843030002
http://hdl.handle.net/11536/61074
显示于类别:Thesis