Robust segmentation of CMM data based on NURBS

Segmentation is a crucial step towards the interpretation of discrete three-dimensional measurement data. This paper presents a robust method for compound free-form surface segmentation and reconstruction. In the proposed method, a cloud of measurement data are collected through a coordinate measuring machine (CMM). The set of measurement data is then sliced along, at most, three orthogonal directions. On each slicing plane, measurement data is fitted by a 2D NURBS spline. Now, maximum curvature points on each NURBS spline can be calculated. These points represent the boundary of the digitised object. With the proposed method, three-dimensional segmentation is simplified to a two-dimensional problem. The effectiveness of the proposed segmentation method will be illustrated with examples of a hair drier and a telephone receiver.     

Reverse engineering of composite sculptured surfaces

A reverse engineering technique is proposed in this study for modelling composite sculptured surfaces. The proposed technique includes a surface fitting algorithm and a surface blending algorithm. The former is formulated as the least-squares minimisation problem for which an error expression was minimised which yields the optimised position of control points and parameter values for the non-uniform rational B-spline patch. Cubic spline and bicubic surface algorithms are developed for two-patch and four-patch blending, respectively. Computer simulation results clearly demonstrate that the proposed technique is useful for composite surfaces modelling applications. Factors affecting the convergence speed and surface accuracy in the optimisation process are also discussed.     

逆向工程技术及其应用

表面数字化和三维CAD建模是逆向工程中的关键技术.对目前逆向工程中的表面数字化及CAD建模技术进行总结和分析,给出应用实例,并指出存在的不足和进一步发展的方向.     

基于CMM的双面凸轮反求设计

三坐标测量机不但可用于零件的质量检测,还可用于反求工程当中.本文以双面凸轮的反求设计为例,介绍了三坐标测量机在反求工程当中的应用.     

Reverse engineering employing a 3D laser scanner: A case study

An important step in many manufacturing processes is the definition of the three-dimensional form of an object's shape. A common example is the definition of a designer's model created in clay or wood. A three-dimensional laser scanner offers the advantage of speed and non-contact sensing compared to traditional touch probe sensing. The three-dimensional data produced have been used in a multi-patch reverse engineering program in order to model objects where many types of surface patches, such as quadric and free-form, are blended together on one object. The surface reconstruction algorithms have been demonstrated to provide accurate and smooth surfaces that are suitable for CAD database integration and CNC machine toolpath generation. The algorithms have been implemented in an interactive 3D surface modelling program that produces surfaces compatible with current CAD/CAM systems. The application of the technology to the reverse engineering of a typical injection moulded part is described.     

Reverse engineering of complex geometry using rational B-splines

Rational B-splines have become the new standard for representing free-form curves and surfaces. This paper presents a method for approximating rational B-splines using digitised data. Instead of using the classical optimisation approach to solve the multivariable nonlinear equations, a new method based on iterations of least-squares solutions and single variable mimimisation is developed. This is made possible by modifying the original objective function to avoid the rational format. Simulation of fitting a 90° arc shows that the algorithm can produce accurate solutions close to nominal values. The efficiency of the algorithm also makes it possible to apply the method to day-to-day reverse engineering problems using rational B-splines.     

逆向工程软件在曲面建模技术中的综合应用

结合逆向工程软件Surfacer、Geom agic、ICEM Surf的各自特点及优势,根据优势互补原则,详细探讨逆向工程软件的综合应用。最后以某健身器材的机罩模型为例,高效优质地构建其CAD曲面模型。     

基于三坐标测量机的曲面数字化研究与实践

曲面数字化是逆向工程关键技术,针对三坐标测量机原有曲面扫描方式的不足,探讨曲面测量中面片的划分方式和扫描路径的规划技术。     

基于三坐标测量机的数据采集技术

数据采集是逆向工程建模的关键环节，测量数据的可靠性决定建模的效果和效率。以三坐标测量机为例，介绍逆向工程中利用三坐标测量机进行数据采集的基本过程。     

反求工程中三坐标机与CAD/CAM系统的数据交换

ＩＧＥＳ格式是一种简单、方便的点坐标数据数据转换格式。在产品反求工程中,三坐标机的数据可根据产品测量需要,转换为ＣＡＤ／ＣＡＭ能接受的图形信息格式,本文根据ＩＧＥＳ的格式要求,编制了一ＩＧＥＳ格式转换程序应用于实践。     

反求工程中横截面扫描数据预处理

介绍了反求工程中非接触式横截面扫描的概念、3种传统的去噪声方法和2种数据平滑方法.基于上述方法,并通过对数据点云特征的分析,提出了适合横截面扫描类型点云的去噪声点和数据平滑的改进算法,并分别给出了实例.     

在机测量与反求系统

在机测量与反求系统是在机测量技术和反求工程技术相结合的产物.该系统重新组合并改造企业现有资源,扩展加工设备的功能,从而缩短新产品设计周期,提高产品精度和质量,增强企业竞争力.本文提出在机测量和反求系统的模型,建立由FV1000三轴立式加工中心、FANUC-0MC数控系统、EP6BL型测头、UG和自行开发的计算机辅助测量软件组成的在机测量与反求实验系统.     

光学扫描和CMM测量数据的配准研究

研究了光学扫描和CMM测量数据的配准问题。给出了基于配准工作台的配准方法,分析了影响配准的误差因素;以法矢准则提取了扫描数据中的标准球数据,并由基准点连接线段的中点代替原来的基准点改进了三点定位算法。实验对比了几种配准方法的误差,验证了改进方法的可行性。     

基子曲面仿形测量的发动机气道逆向工程设计

介绍了仿形测量技术和复杂曲面重构技术，运用于发动机气道逆向工程设计实践中。发动机气道外形准确描述为后续CAM／CAE提供了必要基础和支撑，优化后CAD模型用于快速成型加工出样件。     

逆求工程研究现状综述

首先介绍逆向工程技术发展历程,随后从基于点云的数据处理、曲面重构（非均匀有理B样条曲面和三角Bezier曲面）、国内外常用逆求软件3个方面阐述了逆求工程研究现状。     

反求技术在搅拌机拌筒叶片三维建模中的应用

通过反求技术在搅拌机拌筒叶片上的应用,探讨了原形的数字化技术和叶片原形CAD模型的重建技术,解决了 叶片反求过程中的测量技术及曲面构造技术等关键难点技术。     

基于实物模型的反求工程造型应用

基于实物模型的反求工程造型在设计依据、设计思路、处理方法与造型技术等方面与通常的CAD造型比较,存在明显区别。通过汽车零件的实物测量、造型实例,介绍了按照实物模型反求CAD模型的过程及特点     

逆向工程与计算机辅助产品创新

这里提出了面向计算机辅助产品创新的逆向工程系统，分析了系统的主要特点，论述了系统各个功能模块的详细设计，介绍了系统关键技术的实现方法，在此基础上构建了系统的整体框架．通过一个典型案例展示了系统在实际工程中的应用[1]。     

拖拉机覆盖件的逆向设计方法

针对拖拉机覆盖件的特点,利用逆向工程技术对拖拉机覆盖件进行了再设计,采用三维激光扫描设备和逆向工程软件,经过数据预处理、曲面重构等过程,得到拖毒王机覆盖件的初步结构模型,然后把得到的三维模型导入三维造型软件中,进行相关的结构再设计,结果表明,所创建的新产品快速制造系统对提高拖拉机产品的开发质量和效率具有重要的意义.     

实物逆向工程的关键技术

介绍实物逆向工程中的各种数据采集技术、数据分割技术、曲面重构技术的原理、特点及适用范围,并探讨实物逆 向工程中有待进一步研究的特征建模技术。