基于柔性控制点的三维数据拼接方法

针对大型零件全局测量中的数据拼接问题,提出一种基于柔性控制点的三维数据拼接方法。本文详细介绍了基于机器视觉的阶梯式三维数据拼接原理及实验测量过程,通过投影柔性控制点的方式避免了粘贴标志点的繁琐过程,提高了测量效率。同时采用标准尺和壁板对本文提出的方法进行了验证,实验结果表明该方法有效能够满足大型零件的现场测量要求。     

摄影测量中编码标志点设计方案概述

大尺寸三维测量中,通常在被测物体表面设置一些具有唯一特征的编码标志点,通过解码可实现不同图像中同名点的匹配。本文首先介绍了摄影测量技术中编码标志点的作用和分类,分析了点状编码标志点和环状编码标志点的编码原理及存在的问题,总结了各种改进方案的特点,然后根据编码标志点的设计要求讨论了两类编码标志点的特点,最后对编码标志点的设计提出了一些改进思路。     

基于线结构光的柴油机缸盖三维形貌测量

为了获取某种型号内燃机工件的三维形貌数据,设计了线结构光非接触方式的移动扫描测量系统。探索出了以虚拟双目立体视觉原理为理论基础的相机光心平移轨迹所在直线的方向余弦标定的实现方法,从而确定由系统中各局部坐标系变换到系统全局坐标系的旋转矩阵R和平移向量T,进而求出系统中各个局部坐标系原点在系统全局坐标系下的坐标值,最后得到相机光心移动轨迹所在直线的方向余弦。探索出利用相机的移动距离及方向余弦将局部坐标系数据转换至全局坐标系的计算方法,扫描获取了某种型号柴油机缸盖的三维形貌点云数据,在此基础上设计算法从中提取出气道口的中心坐标,测量精度较高。采用逆向工程软件对工件进行了表面重构,结果与实际表面特征信息吻合良好。     

一种浮空器气囊体积测量装置的现场校准方法探讨

介绍一种浮空器气囊体积测量装置的现场校准方法,通过设定现场校准区域,构建地面控制点的局部三维坐标;在被测对象侧边的6个地面控制点设立测站,用激光全站仪和棱镜组件按照极坐标法观察得到被测对象侧边精密标定杆上所有准校点的局部三维坐标,建立校准参考坐标系,构建完整的现场校准场。测量装置对在校准参考坐标系中的精密标定杆上校准点进行拍摄获得图片,解算得到测量装置的每个相机的外方位元素,得到其位置和姿态,完成校准工作。本文提出的现场校准方法解决了测量装置在任意场景下浮空器囊体体积测量的应用问题和测量装置使用中需要搬动情况下的校准问题。     

基于视觉测量的碟式聚光器面形检测

为保证太阳能热发电系统的发电效率,聚光器镜面必须符合设计精度要求,该文采用单目视觉测量的方法对碟式聚光器镜面进行实际测量。搭建相应的实验测量系统,通过CCD相机采集多幅多位置的镜面和靶标图像,利用Matlab软件进行相机标定、立体匹配以及一系列图像处理,获得镜面各标志点的三维空间坐标值。运用最小二乘法对三维散点数据进行拟合得到800 mm×800 mm碟式聚光器镜面模型。通过聚光器镜面相邻点坐标的差值估计得镜到面整体斜率误差为0.005 56 rad,最大斜率误差位于镜面边缘为0.027 26 rad。结果表明基于视觉测量的碟式聚光器面形检测系统能快速有效地检测镜面面形。     

基于GPS、三维激光扫描技术的堤坝扫描测量

本文介绍了用三维激光扫描技术对堤坝进行扫描测量工作。针对堤坝呈线性分布,且长度较长,扫描角度较差的特点,导致难于寻找公共点实现自动拼接的难题,提出用GPS沿坝体方向布设基准点,再用全站仪测量坝体上标靶点坐标的方法来完成整个堤坝的扫描工作。从而实现把多次的扫描数据统一到同一个坐标系下的目的,成功避开被测堤坝难于寻找同名点实现自动拼接的难题。     

白车身视觉检测系统中多类型传感器全局校准技术

针对白车身视觉检测系统中传感器数量多、种类各异、分布空间大、位置关系复杂等问题,提出了一种适用于工业现场的多视觉传感器全局校准技术。基于坐标系间接统一法,设计多个精密立体靶标作为坐标系转换中介,利用激光跟踪仪获取现场校准数据,在单位四元数数学模型的基础上,求解两坐标系间最优转换矩阵,将固定式传感器和柔性传感器的测量坐标系统一到全局坐标系。该方法已在某企业在线测量项目中成功应用,现场只需完成传感器坐标系与全局坐标系转换关系标定,降低了复杂现场环境对多传感器全局校准的限制,简化了校准过程,提高了环境适应性,校准后检测系统各向测量精度均优于±0.2 mm,满足白车身在线测量精度要求。     

大型水轮机叶片快速检测的新方法

为解决大型水轮机叶片尺寸检测这一行业性难题,实现对叶片型面外型尺寸的快速检测,提出了一种基于视觉测量技术的新方法.该方法以摄影测量原理为理论基础,首先在物体表面待测位置粘贴标志点,然后从不同角度拍摄一组照片,作为测量的原始数据输入计算机中进行解析处理.在测量软件中通过对照片组进行图像检测,识别出各张照片中标志点并定位其中心,匹配同名标志点,最后根据标志点的多个二维坐标重建出对应物体点的三维坐标,从而实现对被测对象的数字化建模和测量.现场实验表明,与传统的水轮机叶片检测方法相比,该方法具有工作量小,速度快,成本低,容易实现在线检测,并且不易受现场灰尘、振动、湿度和温度变化等外界因素的干扰.     

王冠虫化石三维数字建模与几何形态测量

基于结构光扫描方法,实现王冠虫化石空间形貌特性精密测量.经过形貌扫描、数据采集、整合拼接等步骤,建立王冠虫化石三维数字模型.利用数字模型,通过局部最小二乘法,得到具有典型几何形态特征的关联直线,再通过直线相交获得几何标志点的精确空间位置,进而得到王冠虫化石的精密几何形态信息,如标志点间距离、间肋沟与背沟夹角、近三角形尾甲处轴叶各边长与角度等.采用万能工具显微镜与王冠虫化石数字模型进行对比测量,距离测量精度优于0.1 mm,角度测量精度优于1'.     

一种平面标靶的校正方法

提出一种新的标靶校正方法.首先,用一台数码相机从不同角度拍摄标靶,获取多幅图像.分别提取各图像中标志点的中心作为特征点,根据标靶图案的拓扑关系,建立各幅图像间同名标志点的对应关系,并结合光束平差计算特征点的三维坐标,该特征点的三维坐标由尺度因子所约束.最后,根据任意两个特征点的实际距离来获取尺度因子,并将各特征点的三维...     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.