基于热交换的放出法测试流量特性的研究

给出了固定容积放气过程的热力学模型,提出了仅根据"停止法"的瞬态压力曲线求出容器壁和内部空气换热系数的方法,并应用于定容积放出法测量电磁阀的流量特性的数据处理过程中.从测试结果可以看出,在定容积放出法中考虑热交换可以很大程度提高测试结果的精度.并分析了换热系数对测试结果的影响.     

超精密外差利特罗式光栅干涉仪位移测量系统

开展了扫描干涉光刻机工作台超精密位移测量的实验研究,以提高扫描干涉光刻机的环境鲁棒性。针对扫描干涉光刻机工作台位移测量精度,提出了新型高环境鲁棒性外差利特罗式光栅干涉仪测量系统。介绍了系统测量原理,设计了测量系统,提出了基于Elden公式的系统死程误差建模方法。设计制造了尺寸仅为48mm×48mm×18mm的光栅干涉仪。基于误差模型计算了死程误差,计算结果表明:对于1.52mm死程的光栅干涉仪,宽松的环境波动指标(温度波动为0.01℃、压力梯度为±7.5Pa、相对湿度波动为1.5%、CO2含量波动为±50×10-6)仅引起±0.05nm的死程误差。最后,设计了基于商用双频激光平面镜干涉仪的测量比对系统,开展了光栅干涉仪原理验证实验和测并量稳定性实验。原理验证实验表明:光栅干涉仪原理正确且系统分辨率达0.41nm。测量稳定性实验表明:常规实验室环境下,环境波动引起的死程误差为7.59nm(3σ)@0.9Hz1~10Hz,优于同等环境条件下平面镜干涉仪的31.11nm(3σ)@0.9Hz1~10Hz。实验结果显示系统具有很高的环境鲁棒性。     

基于光纤光栅的高速气流总温测量方法

针对航空发动机高速气流总温测量的需求,结合光纤光栅尺寸小、无需回路的结构特点,本文提出一种采用光纤光栅作为感温元的滞止罩式微型总温探针设计与测量方法。通过数值模拟方法对光纤光栅总温探针进行了气动结构设计,分析了探针结构参数对总温测量结果的影响;在此基础上,制作了光纤光栅总温探针,搭建了总温测量数据处理系统,并通过亚音速风洞试验测试了光纤光栅总温探针的工作性能。结果表明,在马赫数为0.3～0.8亚音速气流冲击下,光纤光栅总温探针具有良好的滞止效果和稳定性,马赫数大于0.5时其复温系数达到0.8以上,在马赫数为0.8时达0.99。所制作的微型光纤光栅总温探针直径低至0.8 mm,结构尺寸远低于热电偶探针,在满足总温精准测量的同时,可有效降低对流场的干扰。     

双波长集成光栅干涉微位移测量方法

介绍了一种基于双波长激光的集成光栅干涉位移检测方法,利用该方法对硅-玻璃键合工艺制作的集成光栅位移敏感芯片进行了测试实验。实验系统主要由敏感芯片、波长为640nm和660nm的双波长半导体激光器、双光电二极管及检测电路组成,敏感芯片则由带反射面的可动部件和透明基底上的金属光栅组成。入射激光照射到光栅上产生衍射光斑,衍射光的光强随可动部件与光栅之间的距离变化,通过分别测量两个波长的衍射光强信号并交替切换选取灵敏度较高的输出信号,实现了一定范围内的扩量程位移测量,并得到绝对位置。实验结果表明,利用双波长集成光栅干涉位移检测方法测得敏感芯片可动部件与基底光栅的初始间隙为7.522μm,并实现了间隙从7.522μm到6.904μm区间的高灵敏度位移测量,其噪声等效位移为0.2nm。     

基于 C 4 D 技术的非满管液体流速测量方法研究

为满足目前小型化设备中液体流速测量的需求,通过将空间滤波测速与电容耦合非接触电导测量(C~4D)技术相结合,提出了一种适用于非满管液体流速测量的新方法。设计了一种轴向两电极结构的C~4D传感器,采用COMSOL仿真软件建立了传感器的三维仿真模型,并对其空间灵敏度分布特性进行了分析,然后基于该传感器的空间滤波效应对液体流速测量原理进行了理论推导,并采用等效峰值频率的方法得到了速度测量的数学表达式;在此基础上,设计了一套可适用于空间滤波的C~4D液体流速测量系统,并通过该测量系统验证了C~4D传感器具有良好的空间滤波效应,且实验结果表明,该测量方法具有良好的可行性,在1.39～2.35 m/s的速度范围内,测量速度的绝对误差均在5%以内。     

基于相关和最小二乘原理的光栅栅距动态测量

栅距是光栅位移精密测量的基准,测出栅距值是进一步提高位移测量精度的关键.根据光栅莫尔条纹的动态特性,提出在光栅传感器运动过程中将栅距量转换为时间量测量的新方法.首先基于相关原理测量莫尔条纹信号经过两个距离固定的光电转换器的时间延迟来获得传感器的运行速度,时延估计采用了小波自适应算法;其次基于最小二乘原理确定莫尔条纹信号的相邻两个最小值来获得光栅栅距所对应的时间;最后由运行速度与栅距所对应时间的乘积确定栅距值.实验结果表明对于20 μm栅距的光栅传感器测量误差小于0.08 μm,验证了方法的可行性.     

Straigtness measurement using a heterodyne moiré method

Optical heterodyne interferometry is a new interference technique, allowing quick and accurate measurements of dimension. A similar technique can determine the fringe phase of the moiré method as intensity is modulated by movement of the reference grating. The phase difference between certain points in the moiré pattern is detected automatically.The interference fringes generated by laser are used to measure straightness. Small displacement of fringes is detected with the heterodyne moiré method. Generally, beam flutter caused by air disturbance becomes a serious problem in systems using long beam paths, though it can be reduced by controlling the air flow.     

基于视频的交通流参数测量方法研究

道路交通流参数是交通安全管理、交通状况态势评估和决策的重要基础信息。提出一种改进的具有一定自适应功能的高斯背景建模法,并采用基于透视变换的计算模型,建立车辆的几何尺寸的视觉测量模型,通过CCD传感器感知道路环境并形成视频流记录,利用图像处理和分析方法,对视频流实时处理、跟踪和分析车辆状态参数及道路状况,实现道路交通流基础信息准确实时获取和辨识。实验和现场试验结果表明,平均测量精度达到工程应用需求,可为交通管理部门进行交通管理和交通规划决策提供科学的基础参数信息。     

基于啁啾光栅的温度与应变测量解耦方法研究

实际环境中光纤光栅存在对应变与温度测量交叉敏感问题,提出了利用啁啾光纤光栅(CFBG)进行双参数同时测量的方法。通过将CFBG胶封于等强度梁上,利用CFBG反射谱的中心波长与带宽对温度与应变的灵敏度差异,组成系数解耦矩阵,实现对应变与温度的同时测量。室温下,CFBG的中心波长与带宽随应变变化的灵敏度分别为0. 79、1. 38 pm/με,线性度为0. 998 8、0. 999 3;在-20～60℃温度范围内,CFBG的中心波长与带宽随温度变化的灵敏度分别为22. 74、23. 97 pm/℃,线性度为0. 999 8、0. 997 0,表明使用单个CFBG可以实现同时测量应变与温度。     

基于多频外差相移结构光的三维测量系统

基于相位投影和双目视觉的三维光学测量系统已经广泛应用于各领域。系统通过平板标定技术得到摄像机的内参和外参;针对格雷码与相移结合技术在测量物体边缘位置解相位误差大的问题,采用多频外差原理的测量方式,使用拟合负指数求解像素点的绝对相位,使用对极几何进行亚像素立体匹配。实验证明:该系统可以完成复杂面型测量并且获得高精度点云数据,测量标准偏差为0.03 mm。     

基于外差检测原理的绝对测距性能理论研究

基于双光学频率梳外差原理测距将长模糊距离、高精度和高更新率3个关键测距特性完美结合,使测量性能能够满足航空航天、科学研究和工业生产等众多领域的需求。然而所使用的双光学频率梳的脉冲时域宽度、重复频率及相对差值、脉冲的固有时间抖动等特性都将会影响测距的性能。对基于双光学频率梳外差原理测距进行了全面的理论分析,并数值模拟了数据脉冲宽度、双光学频率梳重复频率差、啁啾参量、定时噪声、脉冲类型等各因素对测距性能的影响。模拟结果在数值上验证了奈奎斯特采样定律对测距精度的显著影响,表明实验中数据脉冲宽度和重频差的选择应严格满足奈奎斯特采样定律;当飞秒脉冲序列存在一定的时间抖动时,重频差越小,测距性能越差;而脉冲的啁啾特性可转化为脉冲宽度的影响,随着啁啾的增大脉冲宽度被压窄,奈奎斯特采样频率对应的重频差临界值也会变小。通过上述数值分析,为研究人员在特定实验条件下优化测距性能提供了重要指导。     

基于三维速度场构建的微流量测量方法研究

采用微流体粒子图像测速仪(microscale particle image velocimetry,micro-PIV)对200μm宽、60μm深的长直通道三维速度场进行了非接触定量可视化测量,并在此基础上计算了通道内的微流量。实验采用二维分层速度场测量方法,将通道沿物镜景深方向划分为11个流体层,通过高精度的位移平台实现流体跨层粒子图像采集。分别针对64×64像素和32×32像素2种判读域,采用micro-PIV系综相关算法对流体层二维速度场进行分析,获得三维全场速度分布,在此基础上利用截面速度离散积分原理计算出截面微流量。实验结果表明,基于微流体粒子图像测速仪的三维速度场分析能够实现对微通道流量的精确测量。对于64×64像素判读域,输入流量在2.481～5.788μL/min范围的测量结果精度较高,最大相对误差为3.87%;对于32×32像素判读域,输入流量在3.307～8.269μL/min范围内均有较高测量精度,最大相对误差为3.69%,表明采用32×32像素判读域的流量测量精度总体上优于64×64像素判读域。     

一种基于光栅扭矩传感器的测量系统设计

扭矩测量是研究机械系统主轴在各种载荷下动态特性的关键方法.根据国内外扭矩测量系统的发展现状和实际,提出了一种基于光栅传感器进行非接触扭矩测量的方法,阐述了光栅传感器的基本原理及实现方法,给出了整个系统及实验平台的设计.该系统具有测量的高精度、全光性、绝缘性、防爆性、抗电磁干扰、耐高温等特点,适合于在恶劣环境下测量细长轴的扭矩,可应用于大型机械传动系统在各种负载和工作环境下主轴的动态特性响应分析.     

光纤光栅微应变测量系统研究

本文提出了一种新型的光纤光栅F-P腔传感探头,分析了其在轴向应变作用下分裂点处波长的漂移情况,设计出了基于此理论的微应变测量系统,并进行了实验验证.实验表明,此系统能够实现微应变的测量,其分辨率为0.0098με.     

A study of mass flow rate measurement based on the vortex shedding principle

Mass flow rate measurement is very important in the majority of industry processes because the mass of fluid is not affected by ambient temperature and pressure as the volume will be. Conventional mass flow rate is normally derived from the volumetric flow rate multiplied by fluid density. The density can be obtained by a densitometer or calculated according to the temperature and pressure measured by a thermometer and pressure gauge respectively. However the measurement accuracy is not always satisfactory. Flowmeters directly measuring mass flow rate have been studied and developed recently, such as Coriolis and thermal flowmeters. Unfortunately they still have some limits in practical applications. A new method in which mass flow rate can be directly measured based on the vortex shedding principle is presented in this paper. As a vortex flowmeter, von Kàrmàn vortex shedding is generated by a bluff body (vortex shedder), leading to a pressure drop and pressure fluctuation. A single differential pressure sensor is employed to detect the pressure difference between upstream and downstream sides of the vortex shedder. Both vortex shedding frequency and pressure drop are contained from the output signal of the differential pressure sensor, so that the mass flow rate can be obtained from the pressure signal. Numerical simulation has been done to analyze the characteristics of the fluid field and design the measurement device. The Computational Fluid Dynamics (CFD) codes Fluent were used in the numerical simulation. Experiments were carried out with water and gas, and the results show that this method is feasible and effective to measure the mass flow rate. This method has also robustness to disturbances such as pipe vibration and fluid turbulence.     

Study on wet gas online flow rate measurement based on dual slotted orifice plate

According to the current technical problems existing in gas and liquid flow measurement for wet gas production, the slotted orifice-couple flow meter was developed and the basic measurement principles for gas and liquid flow was presented. A new wet gas flow meter was developed based on the dual slotted orifice transducer. The flow characteristics of liquid flow through dual slotted orifice plate, the relationship of differential pressure between the dual slotted orifice plate, pressure, temperature, and flow rate of gas/liquid of different aperture ratio were studied. A mathematical measurement model was established to be applied in the flow meter measurement system with dual slotted orifice plate. The model was tested and calibrated by on-site field experiments in the China National Center of Metrology at Daqing Oil field. The results showed that the maximum measurement error of the gas and liquid flow was less than 10% and 15% respectively, when the Gas Volume Fraction (GVF) was greater than 90 vol%. The measurement accuracy of this industrial prototype can meet the requirements of well fluids.     

基于相控外差干涉技术的纳米定位方法的研究

针对工业领域和计量界对定位精度要求的提高,提出了一种基于迈克尔逊干涉仪反向特性的定位控制方法。该方法采用相位锁定控制和外差干涉技术来完成位置测量和控制。在严格控制实验环境条件下,得到了步距值为5 nm的双向步进位移。步距值的不确定度为8×10-9 nm,位移重复性误差小于1 nm。该定位方法的测量尺寸可直接溯源至长度标准,并且采用光电步进相移法可克服压电陶瓷的非线性和蠕变的机械缺陷。该方法在系统环境控制条件下适用于毫米行程位移,可应用于纳米计量和超精密加工等领域。     

In situ topography measurement in the SEM

An automatic technique for measuring heights in situ in the SEM based on a combination of stereo-metric and focusing methods has been developed. A pair of images of a surface element on the specimen is obtained by tilting the beam electrically in a manner such that the plane containing the tilt axis is coincident with the focal plane of the final lens. Cross-correlation is used to determine the parallax between the image pair which is then used to iteratively correct the height of the tilt axis by changing the lens focus. As a result, the lens focus tracks the specimen topography. With an appropriate specimen surface containing high resolution features for image correlation, the technique is capable of maintaining both its lateral and vertical resolutions over several decades of height displacement up to 100 μm. In an experimental system based on a commercial electron-optical column, spot, line profile, and three-dimensional measurements have been demonstrated.     

浮游植物粒级结构的原位测量

浮游植物粒级通常采用采集水样的分级叶绿素法来测定,比较费时且难以实现剖面连续测量。本文提出了一种基于测定海水光吸收来反演浮游植物粒级结构的原位测量系统。该测量系统硬件主要由高稳定光源、光学窗口、样品管、光纤高精度微型光谱仪、数据采集系统等组成。测量数据基于遗传算法来分析浮游植物粒级结构。海上初步试验结果表明,该仪器能够测定水下300 m之内的浮游植物粒级结构,实现1 m剖面分辨率的连续测量,尤其适用于分析50~80m深度叶绿素最大值层的浮游植物粒级结构变化,在未来海洋浮游植物粒级结构测定中有良好的应用前景。     

Light sheet based imaging flow cytometry on a microfluidic platform

We propose a light sheet based imaging flow cytometry technique for simultaneous counting and imaging of cells on a microfluidic platform. Light sheet covers the entire microfluidic channel and thus omits the necessity of flow focusing and point scanning based technology. Another advantage lies in the orthogonal detection geometry that totally cuts‐off the incident light, thereby substantially reducing the background in the detection. Compared to the existing state‐of‐art techniques the proposed technique shows marked improvement. Using fluorescently‐coated Saccharomyces cerevisiae cells we have recorded cell counting with throughput as high as 2,090 cells/min in the low flow rate regime and were able to image the individual cells on‐the‐go. Overall, the proposed system is cost‐effective and simple in channel geometry with the advantage of efficient counting in operational regime of low laminar flow. This technique may advance the emerging field of microfluidic based cytometry for applications in nanomedicine and point of care diagnostics. Microsc. Res. Tech. 76:1101–1107, 2013. © 2013 Wiley Periodicals, Inc.