【作者】 何朝明；

【导师】 李柏林；

【作者基本信息】 西南交通大学 ， 机械设计及理论， 2007， 博士

【摘要】 反求工程之三维重构过程中的曲面造型技术，由于所依据的数据已经隐含了源误差(实物的制造、测量、磨损等误差)，反求工程需要研究如何从散乱点云中提取隐含几何信息、拓扑信息，并建立约束。问题是如何将现存实物原形与拟合参数结合起来，寻找出其原始设计参数，并阐述其存在的合理性，促进设计水平的提高。在本文中，作者主要研究了散乱点云几何处理中的一个重要问题，即，如何从散乱点集中重建网格模型和点元模型的几何特性，并研究散乱点云隐含特征识别和约束方程建立，实现反求CAD建模设计。本文主要的工作内容有：1．提出基于数据分块和控制点对应技术对产品CAD模型与磨损模型进行初次匹配，然后运用散乱数据点云距离、曲面数据分块、法矢过滤的二次匹配进行准确定位，从而实现基于最短距离的磨损区域识别。在深入分析影响多视匹配误差链的性能、制造和加工等因素的约束情况下，建立多视匹配误差链并进行灵敏度分析，从而确定测量规划，并探讨了基于多视匹配误差链的加权平均误差分配算法。2．探讨了非流形拓扑网格模型的几何特性计算，推导了基本单元惯性矩和惯性积的建立，提出基于四面体单元计算三维复杂物体几何特性。对点元模型复杂实体造型从模型的建立原理到几何特性计算进行研究，提出基于CSG表示和布尔造型技术实现复杂实体造型，同时探讨了布尔造型边界求交计算的精确方法，解决不具有任何拓扑关系的点实体模型的几何特性计算。3．探讨了利用数据分块和特征线提取技术，将原始的无序数据点云转化为具有层列结构的有序组织形式，同时保持特征信息并减少数据冗余。提出应用切片技术实现对孔洞周围特征进行识别，并建立局部曲面片，采用线上取点策略进行孔洞位置的修补。在阐述和完善变动几何约束的定义和分类，变动几何约束网络的生成及其运动学模型的基础上，将现存实物原形与散乱点云拟合参数结合起来，利用基本特征、拟合特征、派生特征建立拓扑约束关系，寻找原始设计参数，建立原始设计参数还原约束求解方程。综上所述，本文对散乱点云离散几何信息处理的各个关键环节提出了新的设想和新的算法，为反求工程提供了新的方法和技术，其在计算辅助设计和图形学的工程实际中具有广阔的应用前景。更多还原

【Abstract】 Points of cloud have errors of manufacturing, measurement, assembling and abrasion, the Three-dimensional Surface Model Technology of reverse engineering has to make researches on how to recover hidden geometric and topological information, and construct constraint. The major problem is how to combine with the existing physical object and the parameter to get out its initial design parameter, to elaborate the rationality of its existence and to boost the design level.This paper studies the problem of the discrete points of cloud process technology. That is, how to reconstruct mesh or surfel model to achieve its geometry property, and how to get the basic dimension and the constraint for CAD model of reverse engineering.The main researches are as follows:1. Perform pre-registration to the CAD model and the abrasive model with global registration based on the points of cloud data segmentation and the corresponding technology of the controlled point sets. Utilize the data segmentation, the distance of discrete points of cloud and the normal filter for the precise registration of the two models to recognize the damaged region. Based on the comprehensive analysis of effects on constraints of the multi-views registration error-chain such as performance, manufacturing cost and process ability, the error-chain of multi-views registration is constructed and a sensitivity sequence analysis algorithm is used to determine the measurement plan. The weighted average algorithm for multi-views registration is also presented.2. The computation method of non-manifold mesh model to be mesh solid model is presented. Moment of inertia and product of inertia about the elementary cell is deduced. Geometric properties of the three-dimensional model based on tetrahedron and parallel axis is studied. Through researches on complex solid model of the surfels model from the construction principle of the model to the geometric properties, this paper proposes an algorithm for surfels model from Boolean operation and CSG representation to its geometry property and discusses the accurate method of surface fitting for Boolean operations to resolve calculation of boundary intersection without any topological information.3. This paper discusses that utilizing the technology of data segmentation and feature line extraction reorganizes the scattered data points to layered structure, and keeps the features and reduces data redundant. The paper proposes to apply slicing to recognize features of the hole and construct partial surface matches. Adopt the method of getting points from the line to repair the hole. Based on the definition and classification of Variation geometric constrains, the generation and kinematics model of variation geometric constraints network, the existing physical object and the parameter of discrete points of cloud are combined. Making use of basic feature, associated feature and derived feature to construct the topological constraints and to seek the initial design parameter, establish the constraint equation of initial design parameter retrieval.In a word, this paper proposes new ideas and algorithms to each key procedure in discrete points of cloud information process, and presented new means and new techniques for reverse engineering in this dissertation. It indicates that they have wide applications in computer aided design and computer graphics.更多还原