面向装配的跨零件特征造型的模型表示与实现

Representation Scheme and Realization of Interpart Feature-Based Modeling for Assembly

在产品设计中 ,许多典型的结构特征具有跨零件性 ,如螺钉、销联接等。在现代 CAD系统中 ,特征造型是面向单个零件的 ,在处理跨零件特征时不仅造型效率低 ,而且破坏了这类跨零件特征明确的工程意义。本文在研究这类特征内在的跨零件性、局部修改性及装配关系的基础上 ,将面向零件的特征造型向面向装配的跨零件特征造型延伸 ,提出了虚零件等概念 ,建立了其数学模型 ,表达了在装配建模时通过虚零件对装配对象实体模型自动进行局部修改的关系 ,根据这一模型提出了其实现技术。在自主开发的超人 CAD/ CAM软件和商业 CAD/ CAM系统 UG上开发了机械联接单元智能快速设计软件包。实践表明 ,提出的方法在创建跨零件特征造型时工程语意明确 ,具有高效性、方便性、自然性、智能性等特点 。

During product design, there are many typical structure features which have the character of interpart such as the connecting elements of bolt, pin, and the like. Feature based modeling for single part in modern CAD system causes low efficiency and also blurs the definite engineering meaning of those interpart features. On the basis of the character of interpart, local modification and assembly relation, we extend part feature based modeling to interpart feature based modeling for assembly, propose a series of definitions, such as virtual part, and the like, establish representation scheme which expresses automatic local modification to the model of assembly objects by virtual part during assembly modeling, and propose an implementation method according to the proposed representation scheme. The mechanism is realized on Supperman, a self developed CAD/CAM integrated system and commerce software package UG, and a case study of mechanical connecting elements rapid design software package is illustrated. It possesses the characters of definite engineering meaning, high efficiency, manipulation and intelligence, and integrates well with traditional feature based modeling system.