Improving the integrity of IR based online moisture measurement used in the paper and board industry

The automatic control of product moisture content in the paper industry is based upon online moisture measurement. Furthermore, the automatic control of other quality variables such as coat weight may also rely on the moisture measurement. The integrity of infrared radiation (IR) based online moisture measurement systems was studied by performing basic calibrations at the mills with references sealed between two glass plates. The calibrations were performed according to the EN ISO/IEC 17025 standard which is a requirement for calibration laboratories. The observed measurement errors were 2.9% moisture in the first time calibrations at the 95% confidence level. It is demonstrated that these errors can be reduced to under 0.5% moisture by applying traceable methods in the basic calibration, thus improving the integrity of online moisture measurements. Also a standardised algorithm, based on the experience from the performed calibrations, is proposed to ease the adjustment of different moisture measurement systems.     

Application of traceable sample area measurement in the calibration of online dry grammage measurement used in board production

A method is described for the simultaneous calibration of online grammage and moisture measurement by applying machine reel sampling and traceable sample area measurement. The area measurement is based on a flatbed scanner and image analysis. It is demonstrated that a relative uncertainty of 0.5% can be achieved in dry grammage calibration at the 95% confidence level. The determination of grammage and moisture were performed by applying the EN ISO 536 and the EN ISO 287 standards, respectively. The described technique can also be applied with the calibrations performed for the paper industry.     

基于被动激励的结构应变监测系统在线校准方法

针对在役桥梁结构应变监测系统全天时工况下的在线校准问题,提出了一种基于被动激励的在线校准方法,建立了在线校准系统模型。该模型以桥梁正常通行车辆的动态荷载为激励源,通过应变监测系统与参考系统对结构应变响应参量的同步测量,构建校准溯源链,实现在役应变监测系统不间断工作状态下的在线校准。根据结构应变监测系统计量性能评测需要,建立了基于大样本数据的期间测量误差、基本误差及置信区间的量化分析模型。依托广东九江大桥开展了试验验证,结果表明,所提方法具有现场实施的可行性,由不同数据集计算所得的在线校准结果一致性较好,在包含概率大于90%时,基本误差区间的半宽度偏差不大于±0.005。     

火电厂煤粉浓度软测量研究

软测量技术是基于推断控制理论的一门新兴工业技术。本文在介绍软测量技术的基本原理及其设计步骤的基础上,详细介绍了火电厂采用热平衡法、动压法建立煤粉浓度的软测量模型,通过模型校正和在装置上实现软测量,保证煤粉浓度的在线测量。     

Prototype cantilevers for quantitative lateral force microscopy

Prototype cantilevers are presented that enable quantitative surface force measurements using contact-mode atomic force microscopy (AFM). The "hammerhead" cantilevers facilitate precise optical lever system calibrations for cantilever flexure and torsion, enabling quantifiable adhesion measurements and friction measurements by lateral force microscopy (LFM). Critically, a single hammerhead cantilever of known flexural stiffness and probe length dimension can be used to perform both a system calibration as well as surface force measurements in situ, which greatly increases force measurement precision and accuracy. During LFM calibration mode, a hammerhead cantilever allows an optical lever "torque sensitivity" to be generated for the quantification of LFM friction forces. Precise calibrations were performed on two different AFM instruments, in which torque sensitivity values were specified with sub-percent relative uncertainty. To examine the potential for accurate lateral force measurements using the prototype cantilevers, finite element analysis predicted measurement errors of a few percent or less, which could be reduced via refinement of calibration methodology or cantilever design. The cantilevers are compatible with commercial AFM instrumentation and can be used for other AFM techniques such as contact imaging and dynamic mode measurements.     

基于共面点的多视觉测量系统的全局标定方法

本文提出了一种基于共面点的世界坐标唯一全局标定方法,利用激光跟踪仪在现场构建系统总体坐标系,通过拟合基准面来设置共面标定点,系统中各摄像机传感器直接获得标定点的图像,从而实现了各局部相机的全局标定,不需要中间坐标系的转换,避免了多次坐标转换带来的精度损失,标定过程简单。通过在实际的由多个高速视觉传感器组成的飞行器外部姿态测量系统中进行标定实验,在测量范围较大的情况下,系统精度的均方根误差不超过0.8mm。 关键词：全局标定 视觉测量 激光跟踪仪 共面点     

Multivariate control charts for monitoring internal camera parameters in digital photogrammetry for LSDM (Large-Scale Dimensional Metrology) applications

Industrial non-contact dimensional measurements using photogrammetry rely critically upon stability in time of camera calibration. This is particularly relevant for multi-camera systems employed for continuous and/or long term monitoring of some dimensional process, e.g. dimensional checks of the same manufactured component as it comes off the production line. In most of these cases, camera calibration is updated regularly to ensure optimal accuracy. Specifically, the use of photogrammetric systems requires the knowledge of both internal and external camera parameters estimated by calibration. Constancy of both sets is required during use. Internal parameters, pertaining to camera-specific properties, require stability over the operational lifespan of the system, while external parameters, concerning location and orientation, may change between calibrations. A diagnostic method for internal parameters based on multivariate control charts is proposed. The purpose of this method is to provide a comprehensive stability control over all the performed calibrations, especially for those systems used for regular monitoring of production lines. By integrating chart building into calibration software, no additional steps are added to the operator's workload for the calibration process. A practical application of the described methodology is presented at the end of the paper.     

激光跟踪仪测角误差补偿

由于激光跟踪仪的角度测量精度直接影响仪器的测量精度,本文提出了用自准直仪结合多面棱体对跟踪仪金属圆光栅测角误差进行离散标定的方法。研究了基于谐波分析的误差补偿方法,取金属柱面圆光栅测角误差中幅值较大且相位基本不变的谐波分量建立了补偿模型,避免了最小二乘法不收敛的问题。分析了标定测角误差的不确定度,结果显示：水平测角精度补偿前后分别为1.60"和0.90",俯仰测角精度补偿前后分别为4.89"和0.91",精度分别提高了44%和81%,从角秒级提高到了亚角秒级。结果表明,提出的方法可为激光跟踪仪水平和俯仰轴系提供测角误差补偿,对类似测角系统的误差补偿也有参考价值。     

METHOD FOR PRECISION CALIBRATION OF ROTARY SCALE ERRORS AND PRECISION DETERMINATION OF GEAR TOOTH INDEX ERRORS

A method using the ‘closure principle’ is developed for precision calibration of rotary scale errors of gear measurement machines and precision calibration of gear tooth index errors (accumulated tooth-spacing errors) after ‘removal’ of rotary scale errors. The method uses the standard machine procedure for measuring gear tooth index errors applied to a spur gear artifact mounted between machine centers. Therefore, the rotary scale calibrations include consistent effects arising from eccentricities of machine gear-mounting centers and scale-mounting center relative to the instantaneous axis of table rotation, wobble of the instantaneous axis of table rotation, as well as scale graduation errors, etc. Gear-artifact index errors are referenced to the axis connecting the mounting centers located on the gear. Successful implementation of the method does not require super precision of the gear artifact. A method for obtaining approximate uncertainties (standard deviations) of both scale and index error calibrations is developed that utilises the same measurement data required for the scale and index error calibrations. The developed methods are illustrated by applications to scale and index error calibrations obtained from multiple sets of measurements. Typical standard deviations achieved are under 0.05 μm (1/10th of the wavelength of light). Good consistency is achieved between predicted and measured results. The general methods developed should be useful for other types of rotary axis calibrations.     

High-precision and low-cost wireless 16-channel measurement system for multi-layer thin film characterization

A novel automatic multi-channel measurement system is developed for evaluation of multi-layer thin films. With the aim to solve the unsuitability of conventional four-probe measurements with van der Pauw and Montgomery configurations for multi-layer thin film structure, this measurement system can acquire the temperature coefficient of resistance (TCR) and the I–V characteristics of multi-layer thin films. The wireless technology adopted in this measurement system separates the data acquisition and control circuit, which facilitates the application of the system. The maximum measurement capability of multi-channel acquisition system is 16 samples in a batch. The present work also proposes a highly accurate resistance measurement method for characterizing the multi-layer thin films. The advantages of this system include perfect functions, user-friendly interface, high integration and low-cost. The practical application of the system demonstrates a measurement error less than 0.005% of sample resistance. The testing results show that this system performed well in multi-layer thin film measurement.     

一种基于工具坐标系的机器人运动学参数标定方法

机器人末端执行器位姿误差在基础坐标系中表示时,误差模型中包含姿态误差与位置矢量的乘积项,影响了参数标定识别精度。以工具坐标系为参考系,给出一种基于指数积公式包含关节约束条件的机器人位姿误差标定模型,避免了姿态误差与位置矢量的乘积项对参数标定识别精度的影响。以UR5机器人为标定对象,采用LeciaAT960-MR激光跟踪仪为测量设备,进行参数标定试验。试验结果表明,经参数标定后UR5机器人位置误差模和姿态误差模的平均值分别减小了91.07%和89.16%。     

足部三维测量系统中CCD传感器的全局标定

介绍了足部三维形貌测量系统的原理以及利用测量系统已有的一维运动机构和专用标定组件对测量系统所有CCD进行全局标定的实用方法。建立了基于光平面坐标系、标定坐标系、一维运动机构坐标系和CCD图像坐标系的测量系统模型;在测量系统一维运动机构的控制下,光平面分别对标定组件中两个斜面进行扫描,求取两个斜面上扫描线在光平面坐标系中的交点坐标,并根据光平面坐标系中交点坐标和CCD图像坐标系中交点坐标的对应关系,采用坐标映射方法建立光平面与CCD图像坐标系之间的坐标转换关系;确定了基于坐标系之间转换参数的优化目标函数,并根据标定块的标称值和实际测量结果,利用POWEL直接优化方法对坐标系之间的转换参数进行了优化。测量结果表明,单个CCD重复测量误差＜0.062 5%;4个CCD测量值相对误差＜0.365%。实验结果表明,所述全局标定方法减小了一维运动机构、光平面和足支撑玻璃平板之间安装调节误差以及CCD等器件非线性带来的影响,且简便、实用、不需要其它精密标定仪器,可以对测量系统进行现场标定。     

一种新型激光粉尘浓度在线测量仪的研究

本文提出了一种基于光散射原理的粉尘浓度激光测量新方法，该方法无需预先获取粉尘颗粒的平均粒径，可直接测量浓度。基于新方法设计了一套粉尘浓度在线测量仪，测量仪以8031单片机为核心，具有浓度的实时LED显示和数模输出功能，并通过与上位机的串行通信实现浓度数据的后台存储。该仪器具有新颖的光学构造，可在单片机的控制下进行在线标定和在线光路对中，并已用于某钢厂粉尘排放的实时测量，测量结果表明仪器具有良好的灵敏度和可靠性，可满足实时在线测量粉尘浓度的要求。     

原位检测系统中触发式测头的误差分析与补偿

在分析了原位检测系统中触发式测头误差来源的基础上,提出了自动调整测头偏心的方法,并用标定球对测头的实际作用半径进行了校准。同时,面向实际测量任务,提出了基于在线标定和双线性插值技术的逐点测头半径补偿方法,实验验证,所提出的半径补偿方法比商用软件提供的方法更准确,提高了测量结果的准确性。     

Development and analysis of an automated dimension measuring microscope

A theoretical model is developed to describe the operation of a bright field, optical microscope intended to be used for making automated measurements of features as small as 0·3 μm. The measurement of gap lengths in magnetic recording heads and linewidths on integrated circuit photomasks is discussed in detail. Different measurement techniques are investigated theoretically and their perfomances in the presence of aberrations, focus errors and non-ideal transducer responses are assessed. An automated measurement technique based on image shearing is presented and compared with other measurement techniques based on bright field image scanning. It is demonstrated that the automated image shearing method is much less prone to measurement errors due to system parameters. The model was used to develop an optimized design for the measurement system and a complete instrument was built. The performance of the practical measurement system agreed well with theoretical predictions. A calibration standard and a simple but accurate calibration algorithm were also developed.     

Calibration procedures and uncertainty analysis for a thermal mass gas flowmeter of a new generation

This paper deals with the differences between traditional and new technology gas meters, and focuses specifically on the calibration procedure and uncertainty evaluation of CTTMFs (Capillary Type Thermal Mass Flow Meter). In particular, measurements performed on a sample set of commercial CTTMFs for natural gas in domestic/residential (G4) applications allowed to evaluate the modifications to calibration procedures required by the new generation, digital, gas flow meters. Indeed, traditionally natural gas is metered by means of volumetric measurement techniques, while the modern, static gas flow meters (thermal and ultrasonic ones) are based on electronic flow sensors. This implies that the gas volume through the meter is measured by sampling the flow rate at selected time points and integrating the flow rate in time. The measurement time becomes therefore an important parameter, thus requiring a thorough rethinking of the calibration procedure. In order to analyse the effects of the various parameters, a series of ad-hoc calibrations were performed. Specifically, one set of calibrations was performed with constant totalized volume, while the other required a constant measurement time. In order to highlight the novelties that will have to be implemented in ordinary calibration procedures to get the best of the new technologies, the two procedures as performed on a sample set CTTMFs will be compared; the theoretical (generic) evaluation of the associated uncertainty will also be presented. Measurements were carried out at the test facility of INRIM, the Italian National Metrology Institute.     

A high-throughput maize kernel traits scorer based on line-scan imaging

Maize kernel traits such as kernel length, kernel width and kernel number determine kernel weight and, consequently, maize yield. Therefore, the measurement of kernel traits is important for maize breeding and the evaluation of maize yield. The conventional method for measuring kernel traits is still manual, which is time consuming, costly and subjective. In this study, a novel maize kernel traits scorer (MKTS) was developed for the automatic measurement of 12 maize kernel traits based on line-scan imaging, image processing, and automatic control techniques. Here, total of 615 samples were measured to evaluate the system performance. The results showed that the MKTS was capable of evaluating maize kernel traits with the mean absolute percentage error of the manual and automatic measurements less than 5% and the measurement efficiency of approximately 72 s for the measurement of 6 ears. In conclusion, this high-throughput scorer will provide maize scientists with a novel tool to assist in maize functional genetics and maize breeding.     

Acoustic velocity measurements in resonators of thermoacoustic systems using hot-wire anemometry

Acoustic velocity measurements in resonators of thermoacoustic systems using hot-wire anemometry technique flow are presented. The hot-wire calibration is based on the determination of the acoustic velocity reference value through an acoustic pressure measurement and their relationship using a linear acoustic model. In this model, an analytical approach involving the coupling between the sound source and the resonant cavity effects and the viscous and the thermal effects in the boundary layers is used. The amplitude and phase calibrations are reported for the first time, simultaneously, either by varying the sound source input voltage for a fixed frequency, or by varying the frequency for a given source input voltage. The amplitude calibration is detailed by using a filtering technique to eliminate either the acoustic streaming effects or the anemometer basic electric voltage variations effects. This provides a simple way to an amplitude calibration with good accuracy when measuring an average of a stationary oscillating velocity. The phase calibration is proposed here by considering the phase difference between the microphone and the hot-wire anemometer output signals. The results obtained by using a simple fluid-filled resonant cavity are encouraging on the feasibility of this method to carry out a first-order acoustic velocity measurement. However, the complexity of the dynamic calibration due to that of the heat transfer mechanism around the hot-wire probe in various frequency ranges clearly merits more investigation.     

A fast calibration-independent method for complex permittivity determination at microwave frequencies

A transmission/reflection microwave method based on uncalibrated S-parameter measurements for complex permittivity determination of dielectric materials is presented. There are three main advantages of the proposed method. First, the measurements are performed without the need of any calibration standards. Second, it does not require any additional dielectric sample with different thickness; two uncalibrated measurements are required: (i) with a sample filled waveguide and (ii) with an empty waveguide. Third, it does not need a precise location or precise shifting distance of the sample inside the waveguide. The method is iterative needing an initial guess to start the mathematical calculations, and high measurement accuracy can be expected. The method is validated by complex uncalibrated S-parameter measurements at X-band frequencies of low-loss samples (Teflon, Celotex and Duroplex) fitted into a waveguide section.     

三点法中测头角位置的精密测量方法

研究了三点法圆度及轴系误差测量中测头角位置的精密测量方法。设计了能直接测量非接触电容传感器测头实测状态下的角位置的测角系统,提出了克服测头角位置测量误差及三个测头灵敏度标定误差影响的校正方法。实验表明：采用本文提出的“多刻线”法测角精度优于1′,测头角位置测量误差及三个测头灵敏度标定误差对测量精度的影响可降致最小。