【作者】 陈涛；

【导师】 周来水；

【作者基本信息】 南京航空航天大学 ， 机械电子工程， 2004， 硕士

【摘要】 我国航空工业对逆向工程技术有着迫切的需求。本文在理解产品设计意图的思路下，研究了结构件CAD模型重建中的数据分块技术和曲面拟合算法。完成的主要工作如下： 对结构件建模中所遇到的各类特征、特征间的约束进行了详细的分类，并给出由规则曲面组成的结构件CAD模型的约束方程。 逆向工程中，数据分块是一个非常关键的环节。本文借鉴特征分块的思想和八叉树的理论，利用八叉树元格的逐步细分实现点云的分块；然后基于元格点域的法矢和曲率，通过八叉树的回溯，完成各局部区域块的识别；最后按照规则曲面、扫掠曲面、自由曲面的顺序进行特征的自动识别。 研究了规则曲面的拟合算法，给出最小二乘法拟合平面、球面、圆柱面、圆锥面、圆环面等规则曲面的方法，这些方法的显著优点是提高了计算效率，避免了拟合过程中奇异点的影响。更多还原

【Abstract】 With the development of aviation industry in our country, the application of reverse engineering in CAD/CAM becomes more widely and important than ever. Based on capturing designers’ intentions, this thesis studies segmentation of point clouct-and fitting of regular surfaces (including planes, spheres, cylinders, cones, tori, etc.) in structural parts modeling. The main work is as follows: Features and constraints in the reconstruction of CAD models are classfied in detail, and the constraint equations about structural parts constituted by regular surfaces are given. Data segmentation that extracts the edges and partitions point cloud plays an important role in reverse engineering. This thesis proposes an octree-based 3D-cell subdivision method for data segmentation. Firstly, the final 3D-cells are constructed through a refinement process and iterative subdivision of cells. Then, based on normals or curvatures of cells, this method identifies local surface parts through backdating octree. Lastly, feature recognition is implemented automatically according to the sequence of regular surfaces, swept surfaces and free-form surfaces. The least-squares fitting for regular surfaces, such as planes, spheres, cones, tori to 3D data points is researched. The efficiency of computing is improved greatly and the effect of singularities on fitting is avoided.更多还原