【作者】 宋春玉；

【导师】 孙立镌；

【作者基本信息】 哈尔滨理工大学 ， 计算机应用技术， 2004， 硕士

【摘要】 近年来,CAD软件结构正在经历着重大变革,正在从以实体造型为中心的“几何CAD”发展到以特征造型和约束造型为中心的“应用CAD”。作为CAD系统的重要组成部分,约束造型技术近年来得到普遍重视,提出了一些实用的解决方案,大大促进了CAD的变革和应用。同时,出现了新的定义特征的理论、方法及具体实现算法即语义特征,使得特征具有可调整性,提高了系统设计效率。因此,语义特征造型已成为当今CAID系统的主要研究的方向之一。HUST-CAID(哈尔滨理工大学计算机辅助工业造型设计系统)是一种基于特征的参数化造型设计系统。该系统在基于B-rep、CSG树和特征描述树(FDT)的混合模型基础之上,利用重用CSG树与特征描述树的技术,来完成实体模型的设计与编辑工作。但在特征造型过程中,随着造型体数目的增加,设计模型将变得越来越复杂,由此导致了系统设计效率的降低。为了能够正确地维护设计者的设计意图和满足用户的需求,本文在原系统的基础之上,提出了一种语义特征约束模型。同时为了解决现有系统约束模型在过约束状态和欠约束状态时求解难的问题,在对现有的各种约束求解机制和HUST-CAID系统原有约束求解充分研究的基础上,引入了一种新的自由度分析技术,并将此技术初步应用到了HUST-CAID的约束模型中。更多还原

【Abstract】 In recent years, the structure of CAD software is undertaking significant reforms, changing from solid modeling centered systems which are called “geometric CAD” to the feature and constraint based ones, which are called “applied CAD”. As an indispensable part in any CAD systems, technology concerning constraint modeling is highly emphasized, and many useful solutions have been raised which encourage the reform and application of CAD systems. At the same time, the new concept and arithmetic of semantic feature is applied to define feature, where the feature can be adjusted, which improves the efficiency of designing process. So, the semantic feature modeling technique has become very important in most CAID systems.HUST-CAID (Computer Aided Industry Design System developed by Harbin University of Science and Technology) is a parametric modeling design system based on feature. This system describes entities based on mixed model of boundary representation、CSG tree and feature description tree(FDT),in which the design of solid model and feature-editing can be completed with rebuilding CSG tree and feature description tree. But, in the feature modeling, with the number of features increasing, the design model becomes more and more complex. The efficiency of designing is decreased.In order to maintain the intent of designers and satisfy them, the concept of the semantic feature modeling is put forward based on old design system. At the same time, in order to settle the problem that over- and underconstrained models is difficult to solve, on the base of researching all kinds of existing constraint-solving mechanism and old constraint solver of HUST-CAID systems, a new freedom analysis technique is presented, and is elementarily applied to constraint modeling of HUST-CAID systems.更多还原