Uncertainty analysis for a phase-detector based phase noise measurement system

Phase noise is an important parameter to characterise the frequency stability of oscillators and synthesised signal generators. Accurate measurement of phase noise is required for various applications in radar, communication and navigation systems. A single-channel phase-detector based phase noise measurement system is described. The system’s measurement errors and uncertainties have been analysed in details. The expanded uncertainty is about 2.7 dB for calibrating phase noise of a signal generator at 0.001–1.6 GHz for frequency offsets from 1 Hz to 100 kHz. The uncertainty budget for measuring a signal generator’s phase noise at 640 MHz is also presented.     

Measurement of form error of a probe tip ball for coordinate measuring machine (CMM) using a rotating reference sphere

This study presents a method of measurement of the form error of the tip ball in the tactile probing systems of a coordinate measuring machine (CMM) by using a rotating reference sphere. The measurement of the form error of the CMM probe tip was conducted without the use of additional external measuring instruments or sensors. The form errors of the probe tip ball and the reference sphere were separated from the probing coordinates of CMM by rotation of the reference sphere. The effectiveness of the proposed method was evaluated based on an uncertainty analysis. The uncertainty in measurement of diameter of the probe tip ball was estimated to be less than 0.5 μm.     

Uncertainty analysis for measurement of measurand

For measuring the true value of a measurand, vague statistical concept of measurand results in inefficient uncertainty analysis of measurement. The vagueness is caused by the fact that true value of the measurand is an unknown parameter such as population mean or median and the measurement of this true value is a random variable. Generally a parameter may be estimated remarkably more efficiently than the prediction of the random variable. The classical uncertainty analysis in the literature has been developed based on the structure that a measurand is a random variable. This misspecification of statistical concept costs serious price of sacrificing efficiency in terms of length of the uncertainty interval. The purpose of present study is to formally formulate a statistical model for the true value of measurand and provide an uncertainty analysis for the measurement of this true value.     

Uncertainty assessment of a prototype of multilateration coordinate measurement system

Large Volume Metrology is essential to many high value industries to go towards the factory of the future, but also to many science facilities for fine alignment of large structures. In this context, we have developed a multilateration coordinate measurement system, traceable to SI metre, and suitable for outdoor measurements or industrial environments. It is based on a high accuracy absolute distance meter developed in-house and shared between several measurement heads by fibre-optic links. Thus, from these measurement stations, multiple distance measurements of several positions of a target can be performed. At the end, coordinates of the heads and of the different target locations are determined using a multilateration algorithm with self-calibration.In this paper, the uncertainty of this multilateration coordinate measurement system is determined with a consistent metrological approach. First, 13 different sources of errors are listed and quantified. Then, thanks to Monte Carlo simulations, the standard uncertainty on a single absolute distance measurement is assessed to 4.7 μm. This includes the uncertainty contribution of the telemetric system itself, but also the contributions of the mechanical designs of the measurement heads and the target. Lastly, measurements of three-dimensional coordinates of target positions are performed in a control environment, then in a large workshop without temperature control: these measurements validate the uncertainty assessment of the system.     

Dynamic analysis by FEM for a measurement system to observe viscoelasticity using levitation mass method

Dynamic analysis was carried out for a novel measurement system to obtain material viscoelasticity using the levitation mass method [Fujii and Yamaguchi, Rev Sci Instrum 75-71:119–123, 2004; Yamaguchi et al., Mech Syst Signal Process 20:1905–1922, 2006; Fujii and Yamaguchi, J Mater Sci 40-18:4785–4790, 2005], which was proposed by Fujii. For this measurement system, a viscoelastic specimen is attached to a block, which is levitated due to a pneumatic linear bearing. Impact load is applied to the levitated block, and then the movement of the block is measured by a laser interferometer. By following our proposed numerical procedure using nonlinear finite element method in our previous paper [Yamaguchi et al., Mech Syst Signal Process 20:1905–1922, 2006], the dynamic properties of the measurement system were investigated. Time histories of velocity for the block were simulated. These results were compared with experimental results. Furthermore, undesirable dynamic components for the measurement system were evaluated using the numerical model by varying pulse width of the input load.     

On-machine measurement of microtool wear and cutting edge chipping by using a diamond edge artifact

This paper presents precision on-machine measurement of microwear and microcutting edge chipping of the diamond tool used in a force sensor integrated fast tool servo (FS-FTS) mounted on a three-axis diamond turning machine. A diamond edge artifact with a nanometric sharpness is mounted on the machine spindle with its axis of rotation along the Z-axis to serve as a reference edge artifact. The diamond tool is placed in the tool holder of the FS-FTS to generate cutting motion along the Z-axis. By moving the X-slide on which the FS-FTS is mounted, the reference edge can be scanned by the diamond tool. During the scanning, the Z-directional position of the tool is closed-loop controlled by the FS-FTS in such a way that the contact force between the tool tip and the reference edge is kept constant based on the force sensor output of the FS-FTS. The tool edge contour can be obtained from the scan trace of the tool tip, whose X- and Z-directional coordinates are provided by the output of the linear encoder of the X-slide and that of the displacement sensor in the FS-FTS, respectively. Since the reference edge artifact has a good hardness and a nanometric sharpness to ensure the lateral resolution of measurement, a microwear on the cutting edge of the diamond tool can be indentified from the measured tool edge contour. Experiments of on-machine measurement of tool edge contour and microtool wear are carried out to demonstrate the feasibility of the proposed system.     

Uncertainty analysis in a novel method for transformer power losses measurement

The uncertainties obtained with a novel method for measuring power losses in transformers are examined. These uncertainties are compared with those obtained by measuring power losses as the difference between input power absorbed and output power delivered and it appears that the new method does offer certain advantages with a suitable choice of instruments. Uncertainties are evaluated in compliance with the relevant CIPM recommendation adopted in 1981 and reaffirmed in 1986.     

A new design of a support force measuring system for hypersonic vehicle aerodynamic measurement

In order to simulate the flight state of the aerocraft better, the aerodynamic parameters are obtained by integrating the airframe and propulsion system in a highly integrated configuration and ignition of the engine during the wind tunnel test. At present, the commonly used internal balance scheme forms a system composed of the model, internal balance and the support. However, most hypersonic vehicle models are flat or slender, which makes it difficult to provide installation space for internal balance, improves the difficulty of model design. This note proposes a support force measuring system. By integrating the balance into the structure of the support, it no longer occupies functional space in the cavity of the model, and its special structure can ensure that the additional torque generated by thrust/drag cannot act on the torque measuring element. This study provides a new way of thinking for the integrated model test with propulsion system.     

Evaluating the measurement capability of a wheel profile measurement system by using GR&R

Reliable data with less variation play a key role for acceptance of the usefulness of the measurement output of a wheel profile measurement system (WPMS) in a railway network. However, in practice, most studies are carried out without checking the reliability of data from such a system, which may lead to inappropriate maintenance strategies. To ensure the measurement capability of WPMS and to support robust maintenance in railway systems, this study has evaluated measurement data for the flange height, flange thickness, flange slope, and tread hollowing of rolling stock wheels by using gauge repeatability and reproducibility (GR&R). In this study, acceptance and rejection criteria for the precision-to-tolerance ratio (PTR), signal-to-noise ratio (SNR), and discrimination ratio (DR) have been employed to evaluate the measurement capabilities. For the purpose of illustration, we have implemented a new proposed approach. This approach involves both an analysis using graphs with four regions with a confidence interval (CI) of 95% and an analysis using a graph with three regions with only the predicted values; the latter type of graph represents an innovation made in this study. This graph has the advantages that it can visualize three different levels of data quality in same figure, namely “unacceptable”, “acceptable” and “good”, and also include a number of measures without becoming unclear, which are features that have been missing in previous presentations. The results show that the measurements of the flange slope are on an acceptable level, while those for the flange height, flange thickness and tread hollowing have to be rejected as unacceptable. The action proposed for increasing the quality of data on the flange height, flange thickness and tread hollowing is to enhance the calibration of the WPMS. In conclusion, GR&R is a useful tool to evaluate the measurement capability of WPMS and to provide helpful support for maintenance decision making. This investigation also shows that there is good reason to be careful when selecting measures and when interpreting the results, since, for a certain wheel profile parameter, when one measure is used, the results may be acceptable, but when another measure is used, the results may be unacceptable.     

Design and calibration test of a support force measuring system for hypersonic vehicle aerodynamic measurement

With the development of air-breathing integrated vehicle test models equipped with engines, the designing of traditional internal balance force measuring systems has become complicated. This is partly because hypersonic vehicle models have slender bodies, and engine systems inside such model cavities are densely distributed, thereby limiting the space available to house traditional internal balance systems. Moreover, traditional force measuring systems are assembled mechanical systems, and their dynamic force transmission characteristics are inevitably degraded under extremely short test time conditions. Thus, herein, we propose a support force measuring system that integrates the traditional internal balance system with a support in an integral design. The designed internal triangular concurrent force system considerably reduces the additional moment generated by the thrust/resistance force. Calibration tests reveal that the new system demonstrates good linearity and repeatability, and the results prove the correctness of the triangular concurrent force system structure principle.     

Uncertainty analysis of displacement measurement with Imetrum Video Gauge

Imetrum Video Gauge is a commercial image-based two-dimensional displacement measurement system which has been widely used. Its uncertainty analysis is presented in this paper. First, the procedure to use Video Gauge is introduced. Then, based on the measurement model, two major sources of uncertainty are identified: (1) the uncertainty associated with the calibration procedure u(C) which is composed of the uncertainty of the known length used in calibration u(L) and the uncertainty of the projection of the known length in the image u(D) and (2) the uncertainty associated with the measurement system itself u(P). Following the Guide to the Expression of Uncertainty in Measurement, the uncertainties can be quantified. In the end, 60 experiments are performed to analyze the relationship between the measurement uncertainty and the working parameters, which are working distance, acquisition frequency and focal length of the lens. In order to ensure the validity of the calculation, two calculation methods are used. The main results of this paper are as follows: (1) the displacement measurement uncertainty increases along with working distance and decreases with the increase of focal length. At the same time, the results indicate that using a longer known length in calibration can also reduce the measurement uncertainty. (2) u(C) is greatly influenced by the known length used in the calibration procedure. It can be reduced when u(L) is reduced. (3) Under the laboratory circumstances, reducing u(C) can greatly reduce the total measurement uncertainty. (4) The displacement measurement uncertainty is more sensitive to the measurement uncertainty of the known length used in calibration than the projection of the known length in the image. (5) As the working distance grows, the sensitivity to the known length is getting weaker and the sensitivity to the projection of the known length in the image is getting stronger. (6) When a longer focal length lens is used, the influence of the working distance to the sensitivity gets weaker. The reported results can help people better understand the characteristics of this system and better use the system for their own purposes.     

An investigation of wall-proximity effect using a typical large-scale five-hole probe

Effects of wall proximity on the calibration of a typical cone-type five-hole probe with a cobra-shaped stem have been investigated for various probe-wall orientations with the variation of yaw angle. In order to obtain a negligibly small boundary-layer thickness to the probe-head diameter, a large-scale five-hole probe is employed in a well-established laminar boundary layer, and the probe Reynolds number is kept to be 3.53×10⁴, which is a representative Reynolds number in turbomachinery flows. The wall-proximity effect, which is closely related to the complicated three-dimensional flow change due to the presence of the wall is found to be pronounced only when the wall proximity is less than two times the probe-head diameter. In general, larger orientation angle between the wall and the probe head results in smaller wall-proximity effect in flow angle measurements. In this study, changes in the pitch and yaw angles due to the wall proximity are evaluated through a typical non-nulling reduction procedure. The results may provide a useful guideline in the near-wall measurement.     

CCD摄像法在工件尺寸测量中的应用

建立了用于工件尺寸测量的 CCD摄像测量系统。讨论了 CCD摄像测量法的基本原理 ,简要介绍其软件系统 ,给出了部分工件尺寸的测量结果。实验表明 ,测量系统可快速、精确、非接触地测量工件的边长与直径等尺寸 ,测量精度误差小于± 2 .5 %。     

Natural mode analysis of a telescopic boom system with multiple sections using the Rayleigh-Ritz method

Journal of Mechanical Science and Technology - A truck crane, a type of construction machine, contains a boom consisting of several strips with different cross-sectional data. A set of the overall...     

基于聚类分析与支持向量机模型的缸盖座圈图像判别

为在生产现场及时检测出发动机缸盖气门座圈未被压装到位的情况,采用蚁群聚类算法对状态各异的缸盖气门座圈缝隙图像进行合理归类,并在聚类基础上推演相关支持向量机(SVM)模型实现检测的早期分流,从而提高现场运行速度与检测判别性能.首先,分析缸盖座圈缝隙图像差异,确定体现检测图像宏观特征的观测点,采用聚类数目未知时的蚁群聚类算...     

Uncertainty of residual stresses measurement by layer removal

A model to evaluate the uncertainty in the measurement of the through-thickness residual stress distribution in plates by the layer removal technique is presented. Thin layers were chemically etched from a stripe on rectangular specimens cut from a low carbon cold-rolled steel sheet. Phase shifting laser interferometry was used to measure the ensuing curvature. Polynomials were least-squares adjusted to the curvatures as a function of the etched depth. The polynomials were inserted into an integro-differential equation relating the curvature to the residual stresses, which were assumed to be a function of depth only. A comparison with X-ray diffraction measurement of the surface residual stresses showed good agreement. The uncertainty was found to increase steeply at the surfaces and to depend mainly on the assumed value for the modulus of elasticity, on the curvature fit, and on the depth of etching.     

Uncertainty of measurement in spectrometric analysis: A case study

The methods of spectrometric analysis belong to a group of measurement methods that are used for their simplicity, speed of analysis, and large selectivity to solve various problems of analytes. Accuracy and reliability of any chemical analysis largely depend on the way the analyzed sample is prepared.     

Contact force measurement using acoustic emission analysis and system identification methods

Acoustic emission (AE) signals were used to investigate the contact force occurring at the head/disk interface of a computer hard drive. The AE sensor was calibrated directly using the “ball drop method” and indirectly using system identification. For the indirect calibration, a high bandwidth laser Doppler vibrometer (LDV) was used. The transfer function was established from the harmonic response derived at different vibration modes and frequencies. A finite element method based transient response simulation of impact was used to estimate the velocity and stress response of the slider. In our experiments, contact forces were found to be in the range of 5–25 mN for nano sliders and 2–10 mN for pico sliders.     

翻车机卸车系统计量用电子轨道衡方案

本文通过对翻车机卸车系统来煤的三种计量方案进行分析,介绍了采用静态轨道衡称重计量的方案和优点。     

采用互扫描法自动标定工作空间定位系统

针对工作空间定位系统(wMPS)现有标定技术效率低,标定程序复杂且须依赖外部测量设备等问题,本文在在研究wMPS测量原理的基础上提出了一种采用互扫描技术的自动标定方法。该方法结合该系统的扫描激光平面测量原理及使用特点,通过在基站上安装已知坐标的接收传感器,采用互扫描技术完成自动标定。文中以两台基站为基础,详细阐述了该方法的数学原理,并给出了基于几何约束的平差模型及其迭代解法。依托天津大学研发的wMPS实验平台对本方法进行了验证,并与基准尺标定法进行了比对。实验结果显示,采用本方法可以实现系统的自动标定,在距离基站5m内的测量空间内可获得0.6mm的坐标测量精度。该方法在保证系统测量精度的同时大大提高了系统的测量效率。