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题名: 义齿点云曲面重建方法研究
其他题名: Research on Method of Surface Reconstruction from Denture Scattered Point Cloud
作者: 张霞
导师: 赵吉宾
分类号: TP391.7
关键词: 计算机辅助几何设计 ; 曲面重建 ; 数据预处理 ; 蒙皮
索取号: TP391.7/Z36/2011
学位专业: 机械电子工程
学位类别: 硕士
答辩日期: 2011-05-27
授予单位: 中国科学院沈阳自动化研究所
学位授予地点: 中国科学院沈阳自动化研究所
作者部门: 装备制造技术研究室
中文摘要: 国内义齿CAD/CAM系统的研究还处于实验室阶段,目前还没有开发出一套实用的产品。由于国外市场的垄断以及国内义齿市场的需求,义齿系统的研制迫在眉睫。义齿曲面重建是CAD系统中非常重要的一部分,重建曲面的好坏直接影响到义齿的造型,以及进一步的义齿产品的数控加工。本文的研究目标是义齿散乱点云的曲面重建,主要内容包括义齿散乱数据点的预处理、义齿点云的三角网格曲面重建和参数曲面重建。 1、 散乱数据点的预处理 义齿点云获取过程中,会不可避免地引入数据误差,产生各种坏点、杂点等,这些异常点的存在会加大曲面重建的难度,造成重建后的模型极大扭曲变形甚至根本无法进行重建。针对以上情况,在曲面重构前,本文对义齿点云做了相应的数据预处理,主要包括通过交互手段对异常点的剔除、采用了主元分析法进行义齿点云的模型变换及提出了基于距离阈值的空间均匀栅格法精简散乱密集数据点,从而获得能够符合重建要求的数据点。 2、 义齿点云的三角网格曲面重建 预处理后的义齿模型数据往往还是散乱无序、无任何几何拓扑信息的,为了能够快速地重建出义齿曲面,本文研究了义齿点云的三角网格曲面重建。三角网格曲面重建对数据拓扑关系具有较宽的适应性,能够高效的完成曲面的重构。文中首先采用了空间delaunay三角剖分法来保证剖分网格的优质性;针对义齿点云数据量大的特点,采用空间栅格法对其进行三维空间划分,提高了曲面的重建效率。 3、 B样条参数曲面重建 三角网格曲面本身的性质决定了它无法精确的表达曲面信息,为了满足后续义齿CAM系统的数据加工的精度要求,需要重建出更为光顺、精确更高的义齿曲面,因此采用了广泛用于飞机、汽车等复杂曲面设计领域的参数曲面重建方法。本文研究了基于散乱点云的B样条曲面蒙皮造型算法,有效地实现了义齿点云光顺曲面的重建。算法首先对散乱义齿点云进行切片处理,提出了一种新的关联点对算法——极角排序法,从而获得更好的初始截面数据点。为了避免蒙皮时需要相容性处理而带来节点和控制顶点增加的问题,本文提出了先通过最小二乘法拟合截面线,再对其进行二次采样,获取各截面线数据点分布相同的坐标点集的重采样算法。利用重新参数化后的采样点,就能有效地解决各截面线的节点向量统一的问题。此算法避免了计算复杂度高的相容性处理过程,重建效率高,实现简单。
英文摘要: As the research of dental CAD/CAM in China was still at the laboratory stage, there is no practical product for dental restoration. With the monopoly of foreign markets and huge requirements of dental patients, it is so urgent to make dental CAD/CAM by ourselves. Surface reconstruction, as a very important part of dental CAD, will determine the quality of dental shape modeling and manufacture. Therefore, the content of this research is the algorithm of surface reconstruction for dental scattered point cloud. This system includes data preprocessing, Delaunay triangulation and B-spline surface reconstruction. 1. Data preprocessing of scattered point cloud It is inevitably to bringing various noise points such as useless points for the characteristic of computer vision. The noise points will not only increase the difficulty of surface reconstruction but also distort the modeled surface and even make the surface reconstruction failed. Hence, this paper presents corresponding data preprocessing algorithm for the denture scattered point cloud. This procedure include deleting noise points by interactive interface, model transformation though PCA(Principal Component Analysis) algorithm and data compacting with space uniform grid method. 2. Triangulation of denture scattered point cloud In order to fast reconstruct a three-dimension denture surface model as fast as possible, a surface reconstruction algorithm of triangulation is presented for those denture point cloud which are still scattered without any geometric topology after data preprocessing. In this paper, Delaunay triangulation is used to ensure the high quality of triangular meshes. Then, the method of space uniform grid is used to partition the large amount of denture points. This method will improve the efficiency of triangulation surface reconstruction. 3. B-spline surface reconstruction Due to the intrinsic property of triangular mesh surface, it cannot precisely present the original denture surface. This paper presents a skinning algorithm of B-spline surface reconstruction. B-spline is widely applied in complex surface modeling such as aircraft, automobile parts surface design. This method will meet the accuracy requirement of dental CAM which want a more smooth and accurate denture surface. First, a new pair-points method of the polar angle sorting is proposed to slice the preprocessed denture point cloud to obtain the cross-sectional points. To avoid the increasing of each cross-sectional control points and knot-vector brought by the compatibility processing of skinning, a curve resampling method is proposed. This procedure approximates cross-sectional curves through the least squares first. Then, these points are resampled according the same distribution on these fitted curves. By re-parameter zing the new points, we can easily get the same knot-vector. Obviously, our method is more efficient which avoid the complex compatibility process of skinning.
语种: 中文
产权排序: 1
内容类型: 学位论文
URI标识: http://ir.sia.cn/handle/173321/9307
Appears in Collections:装备制造技术研究室_学位论文

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张霞.义齿点云曲面重建方法研究.[硕士学位论文].中国科学院沈阳自动化研究所.2011
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