面向三维工序数模构建的特征标注方法研究

针对以三维工序数模开展工艺设计时尺寸标注工作量非常大的问题,提出了基于制造特征完成工序模型的自动标注的方法。首先,对零件MBD模型进行预处理,并对其尺寸标注信息进行提取;其次,基于零件MBD模型上特征的定位尺寸和工艺基准构建特征尺寸链,通过特征尺寸链换算求解工序尺寸,解决工艺设计中工艺基准与设计基准不重合的问题;然后,对其尺寸标注进行显示;最后,在UG平台下通过实例测试,验证了该方法的可行性和有效性。     

简单零件的三维自动标注

结合零件设计,阐述了三维尺寸自动标注的必要性。传统的手工标注方法速度慢、效率低、重复性工作多。介绍了弯管和钣金2类零件的自动标注方法,阐述了在UG平台上二次开发实现三维尺寸自动标注的具体方法和步骤。     

简单零件的三维自动标注

结合零件设计,阐述了三维尺寸自动标注的必要性。传统的手工标注方法速度慢、效率低、重复性工作多。介绍了弯管和钣金2类零件的自动标注方法,阐述了在UG平台上二次开发实现三维尺寸自动标注的具体方法和步骤。     

三维轴类零件尺寸自动标注算法

由于目前CAD软件不具备三维零件尺寸标注的功能,本文针对三维轴类零件提出了一种尺寸自动标注的算法。该算法首先对零件模型进行局部特征形状的识别,对不同的特征用相应的结构体存储信息,并对其设定优先级,然后根据优先级进行排序,把同类型的特征放入对应的数组,然后对数组里面的对象依次进行尺寸标注,标注过程当中可能会出现尺寸冗余的情况,本文采用图论中的并查集算法对冗余尺寸进行判断,给出了算法判断的步骤;最后通过UG平台,用C++语言开发了对应的程序,对算法进行实例测试来验证其可行性与正确性。     

基于B－rep表示的机械零件工作图尺寸标注的智能化

基于实体造型和特征造型技术，对机械零件工作图尺寸标注智能化进行了系统的研究．建立了尺寸标注综合模型，论述了尺寸标注冗余性判断基本原理，将神经网络、特征识别和尺寸键技术相结合，确定零件的尺寸标注方案；采用了基于范例推理（ＣＢＲ）的方法完成了零件标注尺寸的自动市置，最后通过ＡｕｔｏＣＡＤ输出零件工作图．     

基于B－rep表示的机械零件工作图尺寸标注的智能化

基于实体造型和特征造型技术，对机械零件工作图尺寸标注智能化进行了系统的研究．建立了尺寸标注综合模型，论述了尺寸标注冗余性判断基本原理，将神经网络、特征识别和尺寸键技术相结合，确定零件的尺寸标注方案；采用了基于范例推理（ＣＢＲ）的方法完成了零件标注尺寸的自动市置，最后通过ＡｕｔｏＣＡＤ输出零件工作图．     

基于相差轨迹的三维标注缺失尺寸推荐

为保证三维尺寸标注的完整,研究了零件缺失尺寸的推荐方法。在轨迹相交法的基础上,根据轨迹生成规则建立了缺失尺寸与相差轨迹之间的映射关系,通过逆向推理轨迹相交规则建立了相差轨迹的生成规则。以尺寸标注数目最少为原则,通过求取相差轨迹建立了几何基元的最少缺失尺寸提取流程。在刚性体识别法的基础上,通过分析刚性体的等价定位元组的固定条件,建立了刚性体间的缺失尺寸提取算法。给出了零件的三维缺失尺寸推荐的总体流程,并以一个尺寸标注模型为例演示了缺失尺寸的推荐过程,验证了算法的有效性。     

基于特征的公差分析与综合中尺寸链的自动建立

在特征造型基础上阐明了零件和装配体中尺寸、公差的表达和记录，并讨论了尺寸、公差链自动建立的一种方法，以便进行公差分析与综合，使产品成本和精度最佳协调。在产品的三维实体模型上，设计者只需捡取待分析的封闭环的两个端元素，程序就会在零件模型和装配模型中自动搜索建立与此封闭环有关的尺寸链，并确定尺寸链各环的增减性。     

基于二维图形信息的轴类零件三维特征识别

在研究三维轴类零件与二维图形的关联关系基础上,提出一种基于二维图形信息的平面几何特征封闭结构的创建方法;并结合尺寸标注,提出一种轴类零件的三维结构特征的识别方法.实例与应用表明,所提方法可实现典型轴类零件三维特征的提取与识别,效率高,结果准确.     

基于特征的公差分析与综合尺寸链的自动建立

在特征造型基础上阐明了零件和装配体中尺寸，公差的的记录，并讨论了尺寸，公差链自动建立的一种方法，以便进行公差分析与综合，使产品成本的精度最佳协调。在产品的三维实体模型上，设计者只需检取待分析的封闭环的两个端元素，程序就会在零件模型和装配模型中自动搜索建立与此封闭环有关的尺寸链，并确定尺寸链和环的增减性。     

A History-Independent Modelling-Oriented Approach to Solve Geometric Constraints Between Features in 3D Space

History-independent modelling systems are more flexible than history-based ones. They let designers manipulate the model in a more associative, rather than prescribed, way. In this paper, an approach based on 2D geometric constraint solving and a topological entity naming mechanism (TENM) is presented to solve the geometric constraints between features in 3D space. Firstly, in order to break the unidirectional dependency between features in a history-based modelling system, a data structure named feature constraint graph(FCG) is adopted to represent the geometric constraints between features in 3D space. Then a solving sequence is obtained using degree-of-freedom (DOF) based graph analysis. And finally, during the evaluation of the solving sequence, the dimensions in 3D space are mapped to 2D space, the dimensions in 3D space are satisfied indirectly by solving the corresponding 2D geometric constraint system. An example is given to illustrate the process of our approach.     

On-Line Layer Profile Dimensions Measurement of Model Maker Rapid Prototyping Using Vision Technology

The key principle of rapid prototyping (RP) is to fabricate a 3D object, layer by layer, which is a 2D fabrication process. Vision technology is being successfully applied in general industry to inspect object dimensions on-line, but most of the applications are limited to objects with 2D patterns. Hence, it should be possible to apply vision technology to inspect RP layer profile dimensions on-line. A CCD camera was employed to capture the layer profile image of the Model Maker (MM) RP system layer by layer. The captured image was processed to identify the RP profiles and further to calculate the real profile dimensions of the fabricated layer. The experimental results demonstrate that the dimensions of an RP part could be measured in situ, layer by layer, and could, potentially, be real-time monitored. This paper presents the vision calibration and the detailed image processing algorithms for the single layer profile identification and dimensions measurement. The results show that the measurement accuracy of the layer profile was about 98%.     

Application of Fourier transform‐second‐harmonic generation imaging to the rat cervix

We present the application of Fourier transform‐second‐harmonic generation (FT‐SHG) imaging to evaluate the arrangement of collagen fibers in five nonpregnant rat cervices. Tissue slices from the mid‐cervix and near the external orifice of the cervix were analyzed in both two‐dimensions (2D) and three‐dimensions (3D). We validate that the cervical microstructure can be quantitatively assessed in three dimensions using FT‐SHG imaging and observe collagen fibers oriented both in and out‐of‐plane in the outermost and the innermost layers, which cannot be observed using 2D FT‐SHG analysis alone. This approach has the potential to be a clinically applicable method for measuring progressive changes in collagen organization during cervical remodeling in humans.     

电容式角位移传感器电场有限元仿真研究

对电容式角位移传感器二维及三维的电场进行了有限元法分析 ,同时对不同结构参数的敏感元件进行仿真研究 ,仿真结论与样机实验结果相吻合     

A prototype system of three-dimensional non-contact measurement

A prototype 3D measurement system is proposed in this paper which consists of a 1D laser displacement sensor, a 2D image system and a servo controlX,Y-table. The laser sensor and CCD camera are installed on theZ-axis perpendicular to theX,Y-table. The image-processing system employs the adaptive resonant theory (ART) neural networks to classify the outer shape of the measured object. The edge values of the object are then obtained by using the image processing procedures of sliding, stretching, edge enhancement and binary disposal. The 2D dimensions of the object are searched by employing the Hough theory based upon the edge values. The 3D dimensions of the object are measured and assembled by combining theX,Y-coordinates of the table and the scanning results of the 1D laser for the height of theZ-axis. A 3D plaster model is chosen as the specimen for non-contact measurement to verify the feasibility of this approach. The limitations and resolution of the 3D measurement of this system are discussed.     

反求建模中的模型尺度计算方法

根据基于反求工程获得的零件模型信息,研究产品的几何尺度快速计算方法。三维物体尺度计算实质是在空间求取模型最小外接长方体问题,提出三次投影和旋转变换策略,把复杂的三维问题转化为二维平面问题。采用最佳拟合直线方法,计算产品模型投影轮廓多边形的长轴方位,并据此计算旋转变换所需转动角度。最后,针对变换后的零件模型,求取与坐标平面正交的外接长方体,以获得模型的三向尺度。     

基于SolidEdge的岸边集装箱起重机小车机构的参数化设计系统

介绍了采用Vi．sual Basic6．0对三维制图软件Solid Edge进行二次开发,研究岸边集装箱起重机小车机构参数化设计的技术和方法,开发出只需用户输入原始参数和部分零部件的尺寸,系统自动对尺寸进行校核,最终生成符合用户设计要求的三维小车机构模型的系统。     

Development of a percentile based three-dimensional model of the buttocks in computer system

There are diverse products related to human buttocks, which need to be designed, manufactured and evaluated with 3D buttock model. The 3D buttock model used in present research field is just simple approximate model similar to human buttocks. The 3D buttock percentile model is highly desired in the ergonomics design and evaluation for these products. So far, there is no research on the percentile sizing system of human 3D buttock model. So the purpose of this paper is to develop a new method for building three-dimensional buttock percentile model in computer system. After scanning the 3D shape of buttocks, the cloud data of 3D points is imported into the reverse engineering software(Geomagic) for the reconstructing of the buttock surface model. Five characteristic dimensions of the buttock are measured through mark-points after models being imported into engineering software CATIA. A series of space points are obtained by the intersecting of the cutting slices and 3D buttock surface model, and then are ordered based on the sequence number of the horizontal and vertical slices. The 1st, 5th, 50 th, 95 th, 99 th percentile values of the five dimensions and the spatial coordinate values of the space points are obtained, and used to reconstruct percentile buttock models. This research proposes a establishing method of percentile sizing system of buttock 3D model based on the percentile values of the ischial tuberosities diameter, the distances from margin to ischial tuberosity and the space coordinates value of coordinate points, for establishing the Nth percentile 3D buttock model and every special buttock types model. The proposed method also serves as a useful guidance for the other 3D percentile models establishment for other part in human body with characteristic points.     

基于2D轮廓和约束变形的个性化脚型快速定制

介绍了一种从二维形状信息获取三维个性脚型的方法.首先通过扫描仪获取50位参与者的脚型样本,平均各样本顶点坐标构建标准脚型.利用特定脚型的正、侧面轮廓信息作为约束条件,采用离散Laplacian坐标线性求解系统对标准脚型进行变形,获得个性化的三维脚型.利用20位参与者的数字脚型对该方法进行检验,结果证明,该方法是有效的,其平均误差为1.03mm.方法可在不用扫描实际脚型的前提下用于鞋楦定制,实现鞋子的个性化定制.     

基于双测量设备的涡轮精确逆向重构方法

针对车用涡轮增压器中涡轮的结构特征,考虑不同测量设备的特性,提出了一种采用两种测量设备构建涡轮精确逆向模型的方法.通过非接触结构光三维扫描仪获取涡轮叶片点云数据,采用分区域处理法得到涡轮曲面模型,利用二维投影仪得到涡轮外轮廓边界形状和准确尺寸,将其与曲面模型进行数据匹配,在CAD软件中对匹配的曲面进行边界修整,完成涡轮三维建模.利用本方法能可靠重构涡轮三维模型,缩短设计开发的周期.