傅里叶变换轮廓术中三维坐标同时校准方法

在相位测量型光学三维面形测量中,最终都要将相位信息转换成被测物体的高度分布信息,这个过程往往是通过对已知世界空间坐标的特征点事先标定,获得测量系统的内外特征参数后,完成被测物体的三维坐标转换.因此,标定是三维面形测量的关键环节.本文基于双向二次相位-高度映射方法和摄像机针孔模型线性无畸变标定技术,充分利用傅里叶变换的频谱方向特性,提出了对含有特征点的二维标定物表面变形条纹的频谱进行方向滤波操作,同时获取测量系统XYZ三个方向上的标定数据,对测量系统进行立体校准的系统标定方法.结合旋转风扇叶片形变的测量系统,给出了该方法的标定结果:在XY面内(230mm×230mm)的标准偏差小于0.27mm;在Z方向上小于0.022mm,位移测量灵敏度优于0.05mm.该方法为测量系统的实用化奠定了基础.     

3D测量系统中的高精度摄像机标定算法

本文在分析完整的摄像机镜头畸变模型的基础上,提出了一种新的标定算法.该算法包括三个步骤,首先在不考虑镜头畸变的情况下利用标定块上的中间若干个点,采用线性优化方法求出除畸变系数以外的其他外部参数和主要的内部参数;然后固定上述已求得的参数,利用线性优化方法求解畸变系数;最后对所有内部参数和外部参数进行全局非线性优化.最后对本文的标定算法进行了标定实验,实验结果表明,本文算法的标定精度可以达到0.0367 mm,可以满足高精度三维测量及其他应用的要求.     

基于交比不变性的投影仪镜头畸变参数标定方法

利用了透视投影中的交比不变的性质,针对由CCD和投影仪组成的测量系统,在CCD已经标定的情况下,仅考虑投影仪畸变模型为一阶径向畸变的情况,只需要投影仪投射共线的投影坐标已知的4个点,利用交比不变性,建立一元二次方程就可以标定投影仪镜头的畸变参数.该方法的特点是算法简单,易于实施,需要已知条件较少.     

基于扫描线模型的电子激光经纬仪自动瞄准方法研究

为了提高基于视觉引导的经纬仪测量系统的测量效率,提出了一种对空间平面上目标点坐标进行精确瞄准测量的方法。利用激光电子经纬仪对目标做单轴扫描,进一步获得像平面扫描轨迹的平行网格模型,通过该模型建立了扫描线长度与经纬仪单轴旋转角度的关系,并对镜头畸变进行校正,最后利用插值算法得到经纬仪瞄准目标点时的精确角度值。实验结果表明,在矫正畸变后在 10 m×10 m空间内精度可达到 3″,该方法可以有效提高测量效率,保证测量精度。     

基于相位映射的结构光相位误差补偿方法研究

为减小结构光投影视觉测量系统中相位失真对测量结果的影响,基于最小二乘法和线性插值方法,建立实际光栅相位与理想光栅相位映射关系,并以此关系对投影条纹的相位误差进行校正。在校正过程中,为满足线性插值的单调性、有效性和唯一性,对所采集到的相位进行线性拉伸变换,使其覆盖全部投射相位值,并引入微调函数使其形成单调变化的相位序列。为验证该方法的有效性,搭建由摄像机、投影仪组成的光栅投影结构光三维测量系统。实验结果表明:该方法能够对投影仪生成的光栅条纹的非正弦畸变进行补偿和校正,并最终给出合理的相位测量结果。该方法简单可行,可用于实际结构光测量系统的校正。     

自动图像校正原理与方法及在火车导轨图像测量中的应用

提出了一种操作简便的隐参数校正方法。通过校正板上特征点的世界坐标和对应的畸变图像中的图像坐标求出两坐标系之间的转换矩阵元素——隐参数,再由隐参数将被测图像还原到世界坐标系中,得到相当于摄像机在与测量平面垂直并且镜头不存在任何畸变的情况下拍摄得到的图像,并进行图像测量。将此方法应用于火车导轨磨耗图像测量中,现场测试的结果表明,图像校正精度可达0.2 mm,测量系统精度达到0.5 mm,符合标准要求。     

数字图像相关测量中镜头成像畸变的估计和校正

提出一种用于高精度数字图像相关测量的镜头成像畸变估计和校正方法.通过对由刚体平移实验得到的畸变位移场进行分析获得镜头的畸变系数,并根据畸变系数对畸变位移场进行校正.对一25mm固定焦距镜头的成像畸变进行估计,并进一步讨论了该镜头成像畸变对位移测量误差的影响.结果显示,可有效消除由镜头成像畸变引起的位移测量误差,达到高精度测量的目的.     

一种高精度的非线性相位误差校正方法

在相位测量轮廓术中,测量系统中投影仪等存在的非线性响应大大影响了相位测量的精度,因此,如何快速高效地消除系统中的非线性误差是提高测量精度的关键.本文建立了相位误差的精确模型,并提出了一种基于相位误差精确模型的相位提取方法,利用高步数相移算法预先标定各频谱分量的比例关系,再通过迭代运算即可得到高精度的相位分布.实验结果表...     

直升机光电助降系统的双摄影测量算法及实验研究

基于信标的摄影测量定位技术,提出了一种用于光电助降系统的双摄影测量算法.利用两台CCD 摄像机探测直升机两侧各四个信标,建立目标坐标系、摄像机坐标系和图像坐标系,根据信标、镜头中心和信标像点的共线性得到关于旋转矩阵和平移矢量的线性方程组,由此计算出直升机相对于着降点的位姿.设计了一套直升机光电助降实验系统,使用高性能DSP 系统进行实时图像处理,运用双摄影测量算法实时计算直升机着降引导信息.模拟实验结果表明,在两摄像机距离着降点8～13 m 范围内,光电助降实验系统的距离测量精度达到±5 cm,而角度测量精度达到±3°.     

图像尺寸测量中镜头畸变的影响及校正研究

图像尺寸测量是一种非接触式测量技术,系统中的光学镜头畸变严重影响测量的精度.提出利用图像识别技术和最小二乘法,拟合出标准线经成像系统所得到的畸变曲线函数,根据曲线上任一位置的曲率大小来表征镜头畸变率的大小.通过软件编程,直接得出被测镜头各空间区域的畸变率大小.利用测量结果对畸变图像进行校正,通过实验验证,图像尺寸测量的...     

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.