【作者】 刘云峰；

【导师】 柯映林；

【作者基本信息】 浙江大学 ， 机械制造及其自动化， 2004， 博士

【摘要】 反求工程是针对已有产品原型，消化、吸收和挖掘蕴含在其中的涉及产品设计、制造和管理等各个方面的原理和知识的一系列分析方法、手段和技术的综合。近年来，随着特征技术的引入，基于特征的反求工程逐渐成为反求工程新的发展方向，受到广泛的研究和关注。 目前，在基于特征的反求工程中，有关曲面特征处理的研究已经比较深入，可以方便的直接从点云数据中提取二次曲面特征、简单自由曲面特征和过渡曲面特征，基本形成了一种基于曲面特征的反求工程CAD建模方法。与之相比，截面特征作为模型重建中的一类重要元素，其相关处理技术研究却很少，还没有形成基于截面特征的反求工程CAD建模方法。本文针对这一问题，在总结基于特征的反求工程建模CAD方法的基础上提出了基于截面特征的反求工程CAD建模方法，研究了该方法的实现流程、系统框架和关键技术，并分析了运用该方法进行反求工程建模的优势。在总结了相关的数学基础和技术基础后，指出了在基于特征的反求工程中实现该方法的可行性。 在基于截面特征的反求工程建模方法中，截面数据获取和数据预处理是第一步。点云切片是从点云中获取截面轮廓的主要方法，在详细研究点云切片算法的基础上提出了针对自由曲面特征类型点云数据的五条切片原则，重点研究了具有带状曲率分布的点云数据的切片方向确定方法。研究了用圆弧曲率估算截面数据离散曲率的方法和特征点提取方法，提出了基于曲线拟合的截面特征识别方法。 截面特征曲线全局约束优化是实现基于截面特征的反求工程CAD建模方法的最为关键的一步。直线、圆弧、B样条曲线的最小二乘拟合是实现该步聚的基础，在研究截面特征曲线拟合表达和曲线间约束表达的基础上提出了截面特征曲线全局约束优化模型。研究了惩罚函数法和改进牛顿法两种数值求解方法求解该模型的流程，并结合3个实例对两种方法进行了对比分析。 基于截面特征曲线的拉伸、旋转、扫成等简单自由曲面的重建方法已经比较成熟，因此重点研究了基于特征对应的蒙皮曲面重建方法。与传统的蒙皮曲面重建方法相比，运用基于截面特征的反求工程建模方法和特征对应的蒙皮曲面重建方法，可以得到保细节特征的高质量的曲面模型。 基于截面特征的反求工程CAD建模方法已成功应用于基于特征的反求工程CAD建模系统RE-SOFT中，结合一个反求工程建模实例论证了该方法的可行性和适用性。最后在总结全文工作的基础上，指出了有待进一步研究的内容。更多还原

【Abstract】 Reverse engineering techniques are the integration of associated methods, means and techniques with the principle and knowledge related to product design, manufacture and management etc. The main task reverse engineering performs is to extract these information from a physical object to reconstruct a CAD model for a particular purpose like redesign, reproduction or quality control. Along with the introduction of feature technology into reverse engineering, the feature-based reverse engineering is proposed and has been becoming a hot topic of current research in this area.At present, surface-feature based reverse engineering has been studied deeply, and has reached the state where quadric surface, simple free-form surface and blend surface feature can be extracted from point cloud directly and conveniently. Otherwise, the section feature, as an important element in model reconstruction, has rarely been studied. In this paper, a methodology for section-feature based remodeling is introduced, and the flow, architecture, and key techniques related to this methodology are studied. After the investigation of associated mathematics- and technology basis, the feasibility of this methodology is analyzed.In feature-based reverse engineering, with the research of surface feature handling done wieldy and deeply, a methodology of surface-feature based re-modeling has come into being, with which the quadric surface, simple free-form surface and blend surface feature can be directly extracted from point cloud conveniently. Otherwise, the section feature, as an important element of model reconstruction, has rarely studied, and the methodology of section-feature based re-modeling has not come into being. Aiming at this problem, based on the summarizing of feature-based remodeling method, a methodology of section-feature based re-modeling are proposed, the flowchart, architecture, and key techniques of this methodology are studied. The feasibility of this methodology is analyzed based on the investigating of mathematics basement and technology basement.In the section-feature based re-modeling methodology, the section data acquisition and preprocessing is the first step. The point cloud slicing is a main method for section data acquisition from point cloud. Based on the study of slicing algorithms, five slicing principles, applied to the point cloud of free-form surface feature, are proposed. Among them, the method of calculating the slicing planedirection of point cloud, whose curvature map has the property of band distribution, is studied in detail. Other preprocessing methods such as discrete curvature estimation and feature point extraction are also studied, and a section-feature recognition algorithm, based on curve fitting, is proposed.Global constrained model optimization is the most important step in section-feature based re-modeling methodology. The least square method (LSM), applied to fitting line, arc, and B-spline, is the mathematical basis. Under the efficient representation of objects and constraints, the global optimization model is proposed. The penalty function method and modified Newton iteration method are adopted to solve the constrained nonlinear optimization problem. The effectiveness and robustness of the two methods are compared and analyzed through 3 examples.Simple free-form surface reconstruction problem, where the surface is formed by the extrusion, revolution and sweep of section feature curve, has been well solved. So the feature corresponding based skinning method are discussed in detail. Contrast to the traditional skinning surface reconstruction method, the section-feature based re-modeling method and feature corresponding based skinning method can guarantee the small detail feature on surface model. So, with the new methodology, a surface model with better quality can be obtained.The proposed methodology has been approached in the feature based reverse engineering software: RE-SOFT. Through a re-modeling example in RE-SOFT, the feasibility and applicability of the section-feature based re-modeling met更多还原