装配体断层图像边界轮廓的提取和内外环识别

研究装配体断层图像边界轮廓的提取,提出通过构造轮廓包含树及其变形处理来识别装配体断层图像的内、外边界的方法。     

复杂装配体装配关系自动识别方法

提出了利用三维CAD装配模型低层几何信息提取装配关系的方法.通过装配结构树构造的层次包围盒、子装配体以及零件交包围盒、表面包围盒与多包围盒的联合相交检测等策略,减少包围盒相交检测次数.通过几何条件判断两表面是否贴合、对中和相切.通过验证构成相切装配关系的切点、切线(圆)是否在两表面的区域内,构成贴合装配关系的两表面区域是否重叠,构成对中装配关系的两表面平移对中间隙后区域是否重叠对装配关系进行验证.以Autodesk Inventor 2012为应用软件,以汽油钻孔机为例验证了方法的有效性.     

装配体ICT图象的内外边界识别研究

用小波变换提取装配体ＩＣＴ图象中的边界轮廓,提出基于简单环识别装配体ＩＣＴ图象的内外边界,该算法可用于装配体的结构形状分析并能正确地建立实体模型。     

产品装配建模及子装配体识别

首先对装配建模的深入研究,本文采用无向图的方法进行装配建模,主要包括了零件以及零件之间的装配联接关系。通过装配联接关系矩阵将装配模型中的装配关系信息转化成数学信息,并进一步给出了基础件的识别算法。一个装配体中往往包含多个子装配体,子装配体的正确识别可以提高装配操作的并行性。根据装配联接关系信息,本文提出了Ⅰ型子装配体、Ⅱ型子装配体的识别算法．并用实例进行了分析。     

基于文本描述的装配体零件尺寸自动协调

参数化特征方法已经在零件设计中得到了较为广泛的应用。当把这种方法应用于装配体的设计时,必须涉及零部件尺寸约束的描述表示与求解。本文以文本描述的方法表示零部件间的尺寸驱动关系,实现了装配体零部件尺寸的自动协调。     

基于装配概念模型的装配体建模方法研究

提出了一种基于装配概念模型的装配体建模方法,该方法采用自顶向下的设计,先确定产品的基本功能,根据基本功能用机构简图初步进行产品概念设计,并逐步向具体能实现该功能的结构映射,得到产品的装配概念模型,然后以此模型为产品的骨架,完成各零件的详细设计。     

STL模型切片轮廓数据的生成算法研究

对基于STL模型的切片处理技术进行了深入分析,并在吸收现有算法优点的基础上,提出了分组排序、对边求交的分层算法。该算法先根据三角面片中顶点在分层方向的最大坐标值和最小坐标值对各面片进行排序并形成分层关系矩阵,然后对每层的三角面片采用对边依次追踪求交的方法生成切片轮廓数据。实际应用表明,该算法具有高效、稳定和可靠等优点。     

基于零件属性EMD测度的装配体模型检索

提出一种利用EMD算法计算装配体中零件属性矢量差值,实现装配体模型检索的算法.装配体中各零件按照其位置、转动惯量、体积和表面积信息生成属性矢量,组合全部零件的属性矢量,形成集合作为装配体的描述符.使用EMD算法计算装配体模型间零件匹配的最低成本,也即获得装配体模型间的非相似度值,实现装配体模型检索.实验证明使用零件属性...     

装配体静力学仿真中的零件隔离分析法

装配体的仿真在机械设计实践中得到了广泛的应用,如何对一个复杂装配体中的某个零件进行高效、高精度仿真引起了许多研究者的关注。基于子模型法和受力分析法,提出了在装配体仿真中的零件隔离分析法。该法首先对整个装配体进行一般网格划分并进行静力学仿真,再隔离所研究零件,把约束与它的关系用边界条件及边界节点位移来取代,然后只对该零件进行精密网格的强度分析。用一个连杆系统中的所有杆件进行了验证,证明该法具有高精度和高效率。     

基于Web的产品子装配体可装配性评价方法

提出基于Web的产品子装配体可装配性评价方法.从静态、动态和整体三个层次对子装配体的可装配性进行分析,建立了兼有定性和定量评价的子装配体可装配性评价方法体系;开发了支持异地协同设计的子装配体可装配性评价系统.最后通过某型号卫星太阳翼实例验证了该评价方法的适用性、评价指标选取的合理性以及三层评价体系的有效性.     

面向ICT切片图像复杂轮廓数据的三角网格拼接

针对从ICT(Industrial Computerized Tomography)切片图像中提取出的复杂轮廓数据的三维重建中数据量过多、算法复杂等问题,提出一种简单快速有效的三角网格拼接方法。即采用Freeman链码对断层图像的轮廓数据进行存储和精简,再根据相邻层间轮廓的相似性采用凸包理论来确定轮廓对应点,最后根据轮廓对应点情况对原有的轮廓点集合进行增补后采用最短对角法进行网格拼接。试验结果表明,该方法在保证重建精度的情况下有效减少数据量和计算消耗。     

Direct slicing and G-code contour for rapid prototyping machine of UV resin spray using PowerSOLUTION macro commands

Rapid prototyping processes produce parts layer by layer directly from 3D CAD models. An important technique is required to slice the geometric model of a part into layers and to generate a motion code of the cross-sectional contour. Several slicing methods are available, such as slicing from sterolithgraphy (STL) files, tolerate-error slicing, adaptive slicing, direct slicing, and, adaptive and direct slicing. This paper proposes direct slicing from 3D CAD models and generating a G-code contour of each layer using PowerSOLUTION software (Delcam International, Birmingham, UK). PowerSOLUTION includes two main modules: PowerSHAPE is used to build 3D CAD models and PowerMILL is used to produce G-Code tool paths. It provides macro language, picture files and cutting paths for secondary development work.The authors used macro commands to write an interface generating direct slicing from 3D CAD models and G-code contours for all layers. Most well-known controllers in the market accept the G-Code. Therefore, it is easier to apply this scheme in a CNC-machining center to produce rapid prototyping such as laminated object manufacturing (LOM) for complex geometries. The interface was successfully applied the interface to the UV resin spray rapid prototyping (UVRS-RP) machine that was developed to produce RP.     

EM 3D contour maps provide protein assembly at the nanoscale within the neuronal porosome complex

The neuronal porosome complex, the secretory machinery at the plasma membrane of nerve terminals, is a 12–17‐nm cup‐shaped lipoprotein structure possessing a central plug. Since the porosome is a membrane associated, multi‐protein complex measuring >650 kD, it has precluded generation of 3D crystals for x‐ray diffraction studies, nor structural analysis at the atomic level using solution magnetic resonance spectroscopy. These limitations were partially overcome in the current studies, furthering our understanding of the porosome structure. Using atomic force microscopy, electron microscopy and electron density and 3D contour mapping, finally provides at the nanoscale, the structure and assembly of proteins within the neuronal porosome complex. Results from this study demonstrate a set of eight protein units lining the porosome cup, each connected via spoke‐like elements to a central plug region within the structure. The isolation of intact porosomes for near‐atomic resolution using cryo‐electron diffraction measurements, is finally possible.     

基于轮廓的血细胞图像拼接算法的设计与实现

针对显微镜下血细胞切片图视野较小的问题,提出了一种基于轮廓的拼接算法。首先通过改进的迭代法分割出白细胞胞核;采用边界跟踪法提取胞核轮廓后,计算各轮廓图像的不变矩,并构建不变矩的欧式距离矩阵;根据最近邻原则找出匹配轮廓,以匹配轮廓的重心为控制点计算仿射坐标变换系数。实验结果表明,该方法具有旋转、平移、缩放（RTS）不变性,且精度高,自动化程度好。     

Adaptive slicing of functionally graded material objects for rapid prototyping

Slicing is a fundamental process planning task and an important procedure in rapid prototyping. However, most research currently focuses on the slicing of homogeneous objects and few approaches for slicing of heterogeneous objects have been reported in the literature. In this article, we present an approach for adaptive slicing of functionally graded material objects. Unlike homogeneous objects, functionally graded material objects contain both geometry and material information. The layer thickness is computed by considering not only geometry but also material variation along the build direction. The continuous material distribution in each layer is discretised into step-wise gradings by subdividing the slice into sub-regions, which can be regarded as homogeneous material regions. An algorithm that summarised the slicing procedure is described and an example is also presented.     

车身焊装质量评价方法及其存在的问题

目前常用的轿车车身焊装质量评价方法有CⅡ指数、AUDIT扣分和Pass Rate等三种,它们分别从车身尺寸标准差的波动、车身表面缺陷、车身测点尺寸在公差带范围内的通过率等三个不同的角度来评价车身焊装质量;本文阐述了各评价方法的原理,并结合车身生产过程的质量控制对各评价方法的特点进行分析,指出各车身焊装质量评价方法存在的问题。     

基于边界矩的机械零件图像轮廓特征提取技术

为实现机械零件的有效分类,针对零件具有比较明显的轮廓特征的特点,提出了基于边界矩的零件图像轮廓特征提取方法.首先采用轮廓提取算法,提取零件二值图像的轮廓,在进行水平倾斜校正后,以零件的质心为中心,将轮廓图像划分为若干个扇形子区域.利用改进的边界矩计算方法,分别计算出各子区域的边界矩,从而得出零件轮廓图像边界矩的分布特性.最后,采用K均值聚类算法对提取的零件轮廓特征进行分类,实验结果证明了该方法的有效性.     

工业CT图像轮廓数据提取研究

零件CT扫描设备在扫描过程中不可避免会产生大量冗余信息,导致获取的零件轮廓离散点数据存在噪声和冗余数据,使得特征点提取变得异常困难.传统轮廓数据点的提取和平滑除噪是采用不同方法分开进行的,这种传统方法可能会剔除有用的特征数据和造成得到的边界点数据发生畸变和偏移.利用多尺度分析技术研究轮廓离散数据的处理,通过对原始轮廓离散数据曲率进行小波多分辨率分解,然后根据尺度间相关性来去除轮廓数据冗余信息和提取特征点,便于在随后的重建过程中实现更精确的表达.基于该方法开发的软件,在实际应用中取得了良好的效果.     

快速成型技术中分层算法的研究综述

作为快速成型技术中必不可少的环节,根据对零件制造精度和装配要求及效率的侧重不同,多年来多种分层算法已被国内外学者开发出来。在同等加工条件下,根据加工精度要求和层厚变化的不同,将分层算法大致分为等层厚分层算法和适应性分层算法两类。从常用的立体光刻(STL)模型、原始计算机辅助设计(CAD)模型和点云数据3种数据模型入手,简述了两类分层算法的研究和发展;介绍了采用斜边的分层算法、基于区域划分的混合算法、曲面分层算法等先进分层算法;讨论了分层算法中待解决的问题:直接分层算法的文件格式标准和轮廓的精确拟合等问题。最后,总结得出了分层算法未来的研究方向和趋势。     

Constraint factor graph cut–based active contour method for automated cellular image segmentation in RNAi screening

Image‐based, high throughput genome‐wide RNA interference (RNAi) experiments are increasingly carried out to facilitate the understanding of gene functions in intricate biological processes. Automated screening of such experiments generates a large number of images with great variations in image quality, which makes manual analysis unreasonably time‐consuming. Therefore, effective techniques for automatic image analysis are urgently needed, in which segmentation is one of the most important steps. This paper proposes a fully automatic method for cells segmentation in genome‐wide RNAi screening images. The method consists of two steps: nuclei and cytoplasm segmentation. Nuclei are extracted and labelled to initialize cytoplasm segmentation. Since the quality of RNAi image is rather poor, a novel scale‐adaptive steerable filter is designed to enhance the image in order to extract long and thin protrusions on the spiky cells. Then, constraint factor GCBAC method and morphological algorithms are combined to be an integrated method to segment tight clustered cells. Compared with the results obtained by using seeded watershed and the ground truth, that is, manual labelling results by experts in RNAi screening data, our method achieves higher accuracy. Compared with active contour methods, our method consumes much less time. The positive results indicate that the proposed method can be applied in automatic image analysis of multi‐channel image screening data.