大型油罐容量计量中3D空间建模方法研究与比对试验分析

油罐的容量计量是石化企业生产运行的核心工作之一.为了提高计量检定效率,提出一种基于三维激光扫描原理的油罐容量全自动测量方法.讨论了一种扫描点云数据分析方法,通过三角网格和曲面拟和的方法计算出不同液位高度对应的油罐容积值.设计了对比试验系统,选取60 m~3和37 m~3两个标准油罐为研究对象,根据OIML R71和R80的技术要求,以0.025%准确度的容量比较法测量值为参考依据,三维激光扫描方法进行油罐容量测量具有好的复现性,而测得的容量值相对偏差满液位量程处可达0.4%,验证了这种方法的有效性,而且有效提高了油罐容量检定工作效率.     

基于爬壁机器人技术的油罐容积测量新方法的研究

大型石油储油罐经过长期使用后 ,会由于油罐变形而导致其容积变化。因此需要在油罐的使用过程中对其容积进行重新测量。通常采用的传统测量方法 ,如光学参比法和围尺法 ,其操作者的劳动强度大 ,操作危险 ,测量效率低。本文提出的基于爬壁机器人技术的油罐容积测量新方法 ,在此称为自移动法 ,该方法由爬壁机器人绕油罐爬行 ,通过安装于机器人上的一系列传感器而测量计算出油罐容积。该方法提高了测量的自动化程度和测量效率 ,并满足测量精度的要求     

卧式金属罐量入量出双标定法研究

针对卧式金属罐几何测量法、容量比较法在标定准确度及标定效率方面存在的不足,提出量入量出双标定方法。设计以标准金属量器、标准流量计或高精度电子秤为标准器的量入量出双标定装置,以实现同时进行两个卧式金属罐容积标定。介绍了该方法设计原理及装置基本结构,并用实例说明具体的操作过程。在罐容数据处理方面,采用拉格朗日三次插值方法进行插值运算并绘制罐容曲线,对罐容数据进行分析和监测。为验证方法的有效性进行比对试验,试验结果表明,量入量出双标定法及罐容数据插值方法具有较好的准确性及可靠性,可作为卧式金属罐优选的标定方法来使用。     

Method of measuring the change in volume of a diaphragm bellows used in a volume displacer of a constant-pressure gas flowmeter (with a practical guide)

Construction of constant-pressure gas flowmeters utilizing directly driven bellows and diaphragm bellows as volume displacers were described in recent decades. They have important advantages: accuracy, reliability, easy operation and maintenance.Difficult is to scale sufficiently accurately the changes in volume at compression, to evaluate the uncertainty of this measurement, and to include all the emerging uncertainties into generated throughput uncertainty budget.A compensation method has been proposed for precise measurement of this dependence. This paper presents guides for the implementation of it. The requirements that must be met to achieve a very low uncertainty are described. The method was used for measuring two diaphragm bellows of different sizes as example illustrating achievable values. The attained uncertainty of measurement is analyzed and a procedure is described for determination of the volume of the displaced gas and its uncertainty when using a directly driven diaphragm bellows in a constant-pressure gas flowmeter.     

Water density formulations and their effect on gravimetric water meter calibration and measurement uncertainties

In the gravimetric calibration method of water meters, the volume of water that has passed through the equipment under test (EUT) is generally collected into a tank and the quantity (mass) determined by weighing. The mass of water collected is then converted into a volume. This conversion of mass into volume requires knowledge of the water density, which can be estimated, measured directly or determined by other means. The error of measurement of the EUT is determined by comparing the volume recorded by the EUT and the volume collected in the tank. The density of water is, therefore, one of the major causes of measurement uncertainty in laboratory calibration of water meters using the gravimetric method. Water meter calibration facilities commonly use density formulations proposed by the International Standards Organisation (ISO) and the Organisation for International Legal Metrology (OIML). In Australia, additional guidance in water density determination is provided by the National Measurement Institute (NMI). In this study, testing was undertaken using ten positive displacement water meters arranged in series in the test rig to evaluate some of the common water density formulations used in Australia. The effect of these different formulations on the water meter error measurement was determined, as well as the effect on the measurement uncertainties. The results shows that the use of these different density formulations evaluated do not significantly affect the water meter error of measurement or the uncertainty of measurement. There was no apparent correlation between the water meter error and the meter position in the test rig. It was also determined that if the water density was adjusted only for temperature effects, a maximum of 0.05 and 0.15% drift in meter error and measurement uncertainty respectively, can be expected.     

Reaffirmation of measurement uncertainty in pressure sensitivity determination of LS2P microphones by reciprocity method

The paper presents the accuracy and precision associated with realization of primary standard of sound using the reciprocity method. An experimental determination of the front cavity volume on Universal Measuring Machine has lead to reaffirmation of measurement uncertainty in pressure sensitivity determination to 0.04–0.15 dB in frequency range 31.5 Hz to 25 kHz. The reduced measurement uncertainty has also been validated from the results of the recent APMP Key comparison and also by comparison to the manufacturer’s value for LS2P microphones. The use of optical method for measuring the front cavity volume has refined the measurement methodology followed with adaptation of a self reliant, traceable and systematic measurement procedure in comparison to the earlier use of nominal values for sensitivity fitting exercise conducted on MP.EXE program. Consequently, the measurement uncertainty associated with the calibration of working standard microphones, multifunction acoustic calibrator and A-weighted sound pressure level measurements is also reduced.     

电子探针测定镁橄榄石中元素含量的不确定度

本文基于氧化物的ZAF修正法对典型样品进行定量分析。在得出了定量分析结果之后,分析了样品测量不确定度的来源,得出电子探针定量分析的不确定度模型,测算了每个影响因素的具体数据,最后计算出了定量结果的扩展不确定度。结果表明ZAF修正法引入的不确定度对测试结果的不确定度影响非常小,主要影响结果不确定度的因素是测量重复性引入的不确定度造成的。利用不确定度提高测试和仪器校准的准确度,可以对电子探针定量分析的后续工作提供基础和保障。     

α-硫辛酸中有机溶剂残留量的不确定度评定

研究了α-硫辛酸中有机溶剂残留量气相色谱定量方法的测量不确定度的评定方法。通过建立数学模型,对测量过程的不确定度来源如：样品称样量、定容体积、工作曲线、测试方法的回收率和重复性的各不确定度分量进行分析评定和量化,计算了合成不确定度和扩展不确定度,α-硫辛酸中有机溶剂残留量的GC定量结果表示为乙醚（0.252±0.006）%;k=2;异丙醚（0.092±0.002）%;k=2。本试验的不确定度主要由外标工作曲线所引起。     

Evaluation of the standard measurement uncertainty due to the ISO50 surface determination method for dimensional computed tomography

Surface determination is the process by which a CT volume is converted from an image-based representation of an object to a surface-based representation. The process of surface determination relies on well-established image processing algorithms, but these algorithms are not exact, surface determination therefore contributes a component of uncertainty to X-ray CT based dimensional measurements. The purpose of this work is to develop a method for quantifying the standard uncertainty due to surface determination such that this standard uncertainty can be combined with other standard uncertainties in order to calculate the combined standard uncertainty for X-ray CT based dimensional measurements. The proposed method relies on evaluating the mode and the 68% dispersion of the air and material grey values of a given CT data-set. These values are propagated through the ISO50 threshold calculation to give the standard uncertainty of the ISO50 threshold value from which the standard uncertainty due to the ISO50 surface determination method can be evaluated. The proposed method is verified numerically and then demonstrated experimentally for dimensional measurements of an aluminium workpiece, a polymer workpiece, and a steel additively manufactured workpiece. The results show that the measurement uncertainty due to the ISO50 surface determination method is largest for dimensions that have both internal and external surfaces such as wall thicknesses, followed by dimensions such as internal and external diameters, whilst dimensions that are not sensitive to surface determination, for example centre-to-centre distances have the smallest uncertainty due to the ISO50 surface determination method.     

基于蒙特卡罗法与GUM法的直线度测量不确定度评定

由于形位误差测量的复杂性和测量结果评定的多样性,导致在实际测量结果中形位误差的不确定度评定成了难题。通过GUM法和蒙特卡罗法对直线度的测量不确定度进行评定。首先,根据最小二乘法得到直线度的误差模型;然后采用GUM方法对测量结果进行不确定度评定,采用蒙特卡罗仿真方法对测量值进行模拟仿真,从而得到直线度误差的不确定度;设置实验对比,通过数据分析验证了蒙特卡罗方法评定的可行性,为形位误差测量结果不确定度评定提供了更加简便的方法。     

罐车罐体的容积精确计算与尺寸反求方法研究

为计算罐车罐体的容积和在已知容积的情况下确定罐体的设计尺寸,基于UG NX软件的内空间分析器(SpaceFinder)以及实体体积计算和优化功能,提出了两种罐体容积计算和尺寸反求方法。一种快捷的方法是利用Space Finder计算容积,并在此基础上对设计尺寸进行反求计算;另一种精确的方法是利用关联性复制,将装配环境中的模型保持装配关系转换到零件环境中,运用布尔运算和抽取面以及修剪体,得到罐体内空间的实体表示,然后利用实体体积计算功能得到罐体的容积,再利用实体优化功能,在得到内空间实体表示的基础上,根据给定的容积迭代反求出设计尺寸。通过UG/Open二次开发,编写出专用工具。最后,通过对某型号罐车罐体的容积计算与尺寸反求,对该方法进行验证,证明该方法的准确性和有效性。     

分光光度法测定高温合金中铁的不确定度评定

对分光光度法测量高温合金中铁含量的测量不确定度进行评定。通过建立分光光度法测定高温合金中铁含量的数学模型,分析了测量过程中不确定度的主要来源,如测量重复性,溶液浓度,溶液体积,试样溶液定容体积,分取溶液体积等,并对各不确定度分量进行了量化,结果表明：分取试样溶液体积（V1）和试样称量（m0）引入的不确定度所产生的影响很小,可以忽略。对铁含量为0.05%～3.00%的高温合金,置信度水平为95%时,测量结果的扩展不确定度为0.03%。     

New data‐driven method from 3D confocal microscopy for calculating phytoplankton cell biovolume

Confocal laser scanner microscopy coupled with an image analysis system was used to directly determine the shape and calculate the biovolume of phytoplankton organisms by constructing 3D models of cells. The study was performed on Biceratium furca (Ehrenberg) Vanhoeffen, which is one of the most complex‐shaped phytoplankton. Traditionally, biovolume is obtained from a standardized set of geometric models based on linear dimensions measured by light microscopy. However, especially in the case of complex‐shaped cells, biovolume is affected by very large errors associated with the numerous manual measurements that this entails. We evaluate the accuracy of these traditional methods by comparing the results obtained using geometric models with direct biovolume measurement by image analysis. Our results show cell biovolume measurement based on decomposition into simple geometrical shapes can be highly inaccurate. Although we assume that the most accurate cell shape is obtained by 3D direct biovolume measurement, which is based on voxel counting, the intrinsic uncertainty of this method is explored and assessed. Finally, we implement a data‐driven formula‐based approach to the calculation of biovolume of this complex‐shaped organism. On one hand, the model is obtained from 3D direct calculation. On the other hand, it is based on just two linear dimensions which can easily be measured by hand. This approach has already been used for investigating the complexities of morphology and for determining the 3D structure of cells. It could also represent a novel way to generalize scaling laws for biovolume calculation.     

Machine tool probes testing using a moving inner hemispherical master artefact

The growing popularity of usage of touch probes for CNC machine tools has created an increasing requirement to test their accuracy. Indirect methods used until now, based on the measurement of a material gauge with a machine tool equipped with a probe, made the separation of machine tool errors from probe errors impossible. In this article, a new method of testing the probe accuracy, which does not employ a machine tool, is presented. This method employs a moving master artefact in the form of an inner hemisphere. The standard uncertainty of the determination of triggering radius variation is 0.35 μm.     

Measurement uncertainty evaluation of conicity error inspected on CMM

The cone is widely used in mechanical design for rotation, centering and fixing. Whether the conicity error can be measured and evaluated accurately will directly influence its assembly accuracy and working performance. According to the new generation geometrical product specification(GPS), the error and its measurement uncertainty should be evaluated together. The mathematical model of the minimum zone conicity error is established and an improved immune evolutionary algorithm(IIEA) is proposed to search for the conicity error. In the IIEA, initial antibodies are firstly generated by using quasi-random sequences and two kinds of affinities are calculated. Then, each antibody clone is generated and they are self-adaptively mutated so as to maintain diversity. Similar antibody is suppressed and new random antibody is generated. Because the mathematical model of conicity error is strongly nonlinear and the input quantities are not independent, it is difficult to use Guide to the expression of uncertainty in the measurement(GUM) method to evaluate measurement uncertainty. Adaptive Monte Carlo method(AMCM) is proposed to estimate measurement uncertainty in which the number of Monte Carlo trials is selected adaptively and the quality of the numerical results is directly controlled. The cone parts was machined on lathe CK6140 and measured on Miracle NC 454 Coordinate Measuring Machine(CMM). The experiment results confirm that the proposed method not only can search for the approximate solution of the minimum zone conicity error(MZCE) rapidly and precisely, but also can evaluate measurement uncertainty and give control variables with an expected numerical tolerance. The conicity errors computed by the proposed method are 20%-40% less than those computed by NC454 CMM software and the evaluation accuracy improves significantly.     

正弦力法动态力传感器灵敏度不确定度评定

随着汽车技术的日益发展,动态力传感器在汽车NVH、模态试验中用到的越来越多,一般采用动态法校准.本文依据振动与冲击传感器校准方法,以标准振动传感器为标准器,采用正弦力法校准动态力传感器灵敏度,并计算动态力传感器灵敏度测量值的不确定度,确保量准的准确一致和正确传递.     

Development of an optical measurement method for “sampled” micro-volumes and nano-flow rates

Radiopharmaceuticals used in nuclear medicine for therapy or diagnosis (molecular imaging, PETscan, scintigraphy) are characterized in terms of volume activity before injection to patients. The current measurement process relies on dose calibrators which have to be calibrated by transfer standards, traceable to primary standards. For very short half-life radionuclides (few minutes), the metrological traceability can only be assured through an on-site calibration with primary standards. However, until now, there is no primary system for the direct measurement of such high activity radioactive solutions. This study presents the sub-system under development for the measurement of a sampled volume of the order of 1 μL with an associated relative target standard uncertainty of 1%. The volume of solution is a key parameter in activity per unit of volume calibration of radiopharmaceuticals solutions. This article focuses on the volume measurement method development and its validation by comparison to the gravimetric method.The paper, in a first part, describes the developed method and the associated hardware and software. The authors have chosen a non-contact optical method implemented by a microscope camera and associated optics in front of a transparent capillary.The second part of the paper describes the measurement process. Several image processing steps are described and the traceability to dimensional units is presented.Finally, the paper presents some validation results by comparison to a gravimetric measurement, including repeatability and accuracy tests. Further development and improvements, necessary for the finalization of the prototype and the measurement of nano-flow rates are discussed.     

寄生式时栅传感器测量不确定度的分析与评定

为了全面分析寄生式时栅误差和不确定度来源,提高寄生式时栅的测量精度,建立符合国际GUM规范检测结果的不确定度评定模型,以84对级的寄生式时栅为研究对象,根据其测量原理分析所测量角度的计算公式,进而将不确定度来源分为插补脉冲个数的误差、插补脉冲信号的量化误差、行波信号的周期误差和环境误差四大类,从理论上建立各不确定度分量之间的理论传递关系,应用现代不确定度理论,推导出合成测量不确定度计算公式。搭建实验平台,利用示波器等仪器的测量结果评定各不确定分量具体数值大小,计算被测角度的合成测量不确定度值。通过与寄生式时栅整圆周的实际测量误差相比较,可以看出利用该评定方法评定的传感器角度测量不确定度与实际误差相符,因此可以用于寄生式时栅传感器的实际评定。     

Adaptive sampling method for inspection planning on CMM for free-form surfaces

Coordinate measurement machines (CMMs) have been widely used in inspecting mechanical parts with higher accuracy. Both the distribution and the number of the sampled points on measurand have an important effect on the efficiency and quality of the measurement of CMMs. In this paper, an adaptive sampling method is proposed for inspection planning on CMM for free-form surface. The points are iteratively sampled from a form error model, which is constructed by superimposing appropriate form errors on the nominal data. Moreover, a modified algorithm is introduced to determine the deviation of two point sets for the improvement of the inspecting accuracy, and the inspection uncertainty is also analyzed. A comparison is performed between the proposed method and the two well-known sampling methods, which are the equi-parametric method and the patch mean Gaussian curvature-based method, both simulated and experiment results show the effectiveness and robustness of this method.     

两种测度方法表征粗糙表面的效果研究

为了比较结构函数与均方根2种测度方法对粗糙表面的分形表征效果,模拟了具有不同理论分形维数的表面轮廓曲线,然后用结构函数和均方根2种方法对它们进行分形特性表征和分形维数计算,并对表征结果进行了理论分析。研究表明,2种测度方法均具有较好的表征效果。与结构函数测度方法相比,均方根测度方法的分维计算精度高,表征曲线的线性度好,反映分形特征的无标度区间宽,分形表征效果显著。另外,均方根测度方法还具有物理意义明确和分维计算简单的优点。因此均方根测度方法不失为粗糙表面分形表征的一种有效方法。