本科毕业设计--cad模型局部区域分割与检索技术研究.docVIP

各专业完整优秀毕业论文设计图纸 摘 要 有研究表明，新产品中40%可以采用零部件，40%的部分可以通过修改已有零部件完成，只有20%需要全新设计为了寻找参考方案，设计者60%的时间用于资料存在的重复设计与制造现象，企业巨大的其根源是缺乏有效的资源管理工具。三维系统的推广应用使得设计资源主要三维CAD模型模型文本记录的信息CAD系统、设计者和设计时间文本记录模型结构B-rep模型初始分割为凸区域、凹区域和平区域的集合；最后，采用区域融合优化方法，将初始分割得到的局部区域优化组合为数量最少、具有一定工程语义的局部区域集合。 (2) 提出基于区域分割的CAD模型多级形状描述方法。这里用体范围内的面上下文码和区域上下文码、以及局部区域内的面上下文码来对CAD模型进行多级形状描述。上下文码由于引入了模型面或局部区域的上下文邻接关系，大大提高了表征模型形状的辨识能力。 (3) 提出基于多级形状描述符的CAD模型整体与局部形状检索方法。为了满足用户的不同检索需求，这里提出基于上下文码度量和基于区域属性码匹配统计度量的CAD模型整体与局部检索方法。前者用体范围内的面上下文码和区域上下文码相似性度量相比较模型的相似性，后者用局部区域内的面上下文码相似性度量相比较模型的相似性。 在以上的，三维CAD模型系统。。 Abstract Some researches demonstrate that about 40% of new products can apply the previous design cases directly, about 40% of new products can adapt the existing design cases to meet new requirements, and only 20% of new products need a new design from scratch. To find the reference cases, engineers spend about 60% of their time retrieving the desired information. Nevertheless, the repeated design and manufacture have widely existed in the enterprises, which caused a tremendous loss for enterprise. The reason is that they lack an effective design resource management and retrieval tool. The popularity of three-dimensional (3D) CAD systems in industry has resulted in a large number of CAD models being generated. Because the descriptive texts for CAD models have huge uncertainty as the variation of CAD systems, designers and design dates, which leads to text-based retrieval for CAD models with serious limitations. If a complex object is segmented into several local regions with engineering semantics, it will obtain salient shape features and effectively reduce the complexity of a model. This research mainly discusses CAD model segmentation and retrieval approaches, which includes the following aspects: (1) A surface segmentation approach for CAD models is proposed. First, a CAD model is transformed into a face attributed relational graph (FARG). Second, in a FARG, clustering the faces that definitely belong to a CvR or Cc