【作者】 皇甫中民；

【导师】 刘雪梅；

【作者基本信息】 华北水利水电学院 ， 计算机应用技术， 2007， 硕士

【摘要】 逆向工程技术作为消化吸收先进技术和产品快速开发的重要支撑技术,已成为制造业关注的热点。体现设计意图的逆向工程几何模型重构是近年来发展起来的一项具有广阔应用前景的新技术,包括组成物体各表面的曲面提取以及约束关系提取。它不仅可以大大提高重构模型的精度,而且便于产品的再设计。本文主要针对曲面提取技术进行深入研究。重点研究了基于离散点云的法矢曲率精确估算、二次曲面提取和拉伸面、旋转面提取等内容。在此基础上,设计并开发出一个软件原型系统,对本文的理论、方法和系统进行实例验证。论文的主要成果包括:1.提出了一种改进的法矢和曲率估算方法。逆向工程中一个基本而关键的步骤是基于离散数据点估算法矢和曲率,现有估算方法的计算精度和抗噪声能力均无法满足实际应用的需要,本文针对传统估算方法的缺陷进行改进,提出以传统方法估算的法矢为初值,通过迭代的方式不断对其进行修正和优化,最终得到满足精度要求的结果。2.研究了二次曲面的提取技术。初步探讨了曲面识别的基本方法,并依据曲面类型深入研究了各种常见二次曲面的提取方法。提出了使用基于实数编码的遗传算法来解决二次曲面提取这样的多参数寻优问题,分析并实现了基于最小二乘法的二次曲面提取技术,并将遗传算法的提取结果与最小二乘法进行比较,分析了遗传算法和最小二乘法各自的特点。3.研究了拉伸面和旋转面提取技术。在常规估算方法的基础上,提出了采用RANSAC算法来提高拉伸方向及旋转轴的估算精度和抗噪声能力。针对由直线和圆弧构成的复杂轮廓线,采用基于特征点的方法进行分段,提出了一种基于曲率差值的切点提取方法。然后,对曲线类型的识别及轮廓线分段拟合进行了较深入的研究。最后,在Visual C++6.0集成开发环境下利用MFC+OpenGL设计并开发了可视化原型系统。在系统中,实现了本文所提各种算法,以统一、友好的形式对算法的可行性、正确性和有效性进行了验证。更多还原

【Abstract】 As an important supporting technology, reverse engineering can absorb advanced technology and accelerate the product manufacturing, so it has been paid attention by more and more manufacturing industry. The reconstruction of geometric model, which include the designing intention, is not only accurate, but also convenient for the redesign of a product. It is composed of surface extracting and constrained fitting.This thesis studies surface extracting and especially focus on the estimating of the normal vector and curvature based on scattered points clouds, extracting of quadric surface, translational surface and rotational surface. Main results achieved in this thesis are summarized as follows:1. An improved algorithm is presented to estimate the normal vector and curvature from scattered points clouds. To avoid the shortcoming of the standard algorithm, we estimate the normal vector with the standard algorithm initially, and then, the normal and curvature can be solved accurately by a iterative process, the initial normal being used as a starting value.2. Quadric surface extracting from scattered points is studied. Firstly, surface recognition is performed. Then, Genetic algorithm based real-coded and Least-Squares is used respectively to extract quadric surface from scattered points, and the merit and shortcoming of these algorithms are analyzed according to the experiment results.3.Translational and rotational surfaces extracting are studied. We use the RANSAC algorithm to estimate the translational vector and the rotational axis, because it’s more accurate than the standard algorithm. After acquiring profile curve data by projection-based slicing, projection data sets are segmented based on feature points. A algorithm, based on curvature difference, is presented to acquire the tangency points. Finally, the profile curve is reconstructed by each data segment based on the segments types recognition.In the last part of this dissertation, a prototype system is designed and implemented by MFC+OpenGL under Visual C++6.0, which is a professional integrated programming entironment, to demonstrate the algorithms proposed.更多还原