图像传感器的应用测量技术(续三)

5测量结果和误差分析 5．1测量结果 5．2误差分析 5.2.1引言 测量精度是衡量一台测量仪器的重要指标,由此提高仪器的测量精度是仪器设计、加工以及安装过程中需要重点考虑的因素之一。本系统测量结果的误差是由多方面因素所引起的．主要有机械系统误差、光学系统误差、标定及数据处理误差以及环境误差等。下面将针对本系统中的各项误差进行理论分析。     

高速弹丸轨迹精度影响因素研究

高速弹丸轨迹动力学建模结果的精度依赖于从测量数据中合理选择初值，但当前对初值的选取没有明确标准，无法保证得到高精度的建模结果。研究了测量轨迹全程的误差分布，为合理的初值选取提供了基本依据。基于误差传递理论对高速弹丸的雷达测量结果进行精度估计，采用零攻角三自由度模型进行弹道轨迹建模，确定对建模结果有影响的6个精度参数，并进行仿真计算，分析雷达测元误差和弹丸相对雷达的运动情况对测量轨迹精度的影响。整体而言，弹道轨迹精度与目标和雷达测站的相对关系及目标弹道特点有很强的相关关系。雷达测元误差对速度精度影响不大，位置精度的变化与测元变化趋势明显相关，x和z方向的误差逐步变小，而y方向的误差在末段明显增大。本研究结果有助于合理选择最优初值点，进而有助于提高建模结果精度。     

平面运动的串联测量方法研究及其与并联方法的比较

提出了用于测量平面运动位姿的三自由度串联和并联测量方法,介绍了串联和并联测量方法的测量原理．通过建立串联测量方法的误差模型,得出了几何误差源与原始测量参数的映射关系和对末端位姿误差的影响情况,得到了这种方法的精度分析结果．仿真结果和试验数据证明了分析的正确性．同时,从几何误差源的产生和测量运动特性等方面对串联和并联测量方法进行了比较．     

测井缆长的误差建模及应用

为提高测井电缆缆长测量精度,给光纤陀螺连续测斜仪提供高精度缆长信息,对基于光电编码器的缆长测量方法进行了详细误差分析并建立了缆长拉伸误差数学模型。构建了基于FPGA@虚拟仪器的缆长测量系统并应用拉伸误差模型进行拉伸误差的软件补偿．实现了测井缆长的高精度测量。最后刺ABAQUS有限元软件对测量结果进行了仿真验证,结果表明。经误差补偿后缆长测量相对误差低于0．3‰,满足测斜仪对缆长精度的要求。     

提高大型激光加工机器人精度的方法

本文介绍了大范围、高精度5轴激光加工机器人系统的研究开发情况．在提高 其绝对精度的前提下，对大范围框架式机器人的结构、高精度机器人的误差补偿方法进行了 探讨．采用有限元分析的方法对机器人本体进行了优化设计，确保了高精度大型激光加工机 器人设计的正确性．基于测量数据，建立了机器人误差模型，对机器人系统误差进行了补偿 ，取得了较好的结果，保证机器人系统的激光加工精度．     

平行双目视觉系统的定位误差补偿

测量精度在平行双目视觉系统的应用中非常重要.为了提高测量系统的精度，提出了基于改进的BP神经网络的误差补偿策略。采用不同位置处的测量数据作为学习样本，利用训练好的网络模型预测测量系统的误差，对测量结果进行误差补偿，得到新的数据作为测量值。实验结果表明，该方法的结果值相较原始数据，误差减少了70%，为提高视觉系统的定位精度提供了一种新的思路。     

基于相对坐标的机器人末端位姿测量方法

为了解决机器人末端6维位姿难以测量的问题,提出了一种末端位姿的间接测量方法,并给出了适用条件．该方法只需测量末端平台6个目标点在单方向上的相对位移,便可得到机器人末端的6维位姿数据,而且可以消除测量工具的零值系统误差．分析了各几何误差对测量精度的影响,得到了误差影响矩阵以指导测量精度补偿．最后,以一台6自由度运动模拟器为例验证了该方法的有效性．     

基于图像处理的光纤阵列误差测量

利用计算机图像处理技术测量光纤阵列的几何间距误差，给出了光纤图像处理所应用到的阈值分割、形心计算等算法，进而计算出阵列中各光纤纤芯的间距；并且研究了图像的标定方法。其测量精度可达0．1μm。并自动分析和输出测最结果供生产监控，极大地提高了测量精度和生产效率。     

高参数密闭容器液位非接触测量装置

研究了利用γ射线穿透方法进行高参数容器液位连续测量的可行性。介绍了仪表的工作原理，结构设计，分析了误差对测量结果的影响，给出了提高测量精度和检测距离的方法。     

镜面杂质与水汽吸放对露点仪影响的实验研究

显微成像露点仪在研制和测试过程中发现镜面杂质和内腔材质吸放水汽等影响测量精度的问题。针对镜面杂质对显微成像露点仪测量的影响开展了镜面图像特征的实验研究，结果表明：镜面杂质点处露珠凝结具有优先性，且反复凝结消散后镜面出现杂质沉降现象。针对水汽吸放对显微成像露点仪的影响开展了水汽释放与吸附效应的实验研究，结果表明：当温度发生变化时，显微成像露点仪感应舱内壁氧化铝材质存在释放（或吸附）水汽现象，使得显微成像露点仪测量值偏大（或偏小）。研究结果为露点仪在功能设置及镜面与腔体材料选择方面提供了参考。     

Effects of measurement errors on psychometric measurements in ergonomics studies: Implications for correlations,ANOVA, linear regression,factor analysis,and linear discriminant analysis

This paper aims to demonstrate the effects of measurement errors on psychometric measurements in ergonomics studies. A variety of sources can cause random measurement errors in ergonomics studies and these errors can distort virtually every statistic computed and lead investigators to erroneous conclusions. The effects of measurement errors on five most widely used statistical analysis tools have been discussed and illustrated: correlation; ANOVA; linear regression; factor analysis; linear discriminant analysis. It has been shown that measurement errors can greatly attenuate correlations between variables, reduce statistical power of ANOVA, distort (overestimate, underestimate or even change the sign of) regression coefficients, underrate the explanation contributions of the most important factors in factor analysis and depreciate the significance of discriminant function and discrimination abilities of individual variables in discrimination analysis. The discussions will be restricted to subjective scales and survey methods and their reliability estimates. Other methods applied in ergonomics research, such as physical and electrophysiological measurements and chemical and biomedical analysis methods, also have issues of measurement errors, but they are beyond the scope of this paper. As there has been increasing interest in the development and testing of theories in ergonomics research, it has become very important for ergonomics researchers to understand the effects of measurement errors on their experiment results, which the authors believe is very critical to research progress in theory development and cumulative knowledge in the ergonomics field.     

On adaptive Kalman filtering for the Luenberger canonical form

This work reports on simulation results obtained from an adaptive filter for systems in Luenberger canonical form. In particular the effects of errors in estimation of innovations, autocorrelations and initial conditions are examined. The scheme proves to be more efficient than a similar one based on measurement autocorrelations. For a certain class of systems new formulae are given for calculating the structural indices required by the algorithm from the state and measurement dimensions. Extension is made to the more general problem of coloured measurement noise.     

A method for calculation of arterial acid-base and blood gas status from measurements in the peripheral venous blood

In non-emergency medical departments such as internal medicine sampling of arterial blood and analysis for acid-base status is not routinely performed. Peripheral venous blood is routinely taken but interpretation of its acid-base status is difficult. This paper presents a method for calculation of arterial acid-base and blood gas status from measurements in peripheral venous blood combined with a pulse oximeter measurement of arterial saturation. The use of the method has been illustrated using the data of three patients with different acid-base, haemodynamic, and metabolic conditions. The sensitivity of the method has been tested for measurement errors including venous blood acid-base and blood gas status and pulse oximetry; errors due to physiological assumptions including the values of RQ and strong acid production at the tissues; and errors due to air bubbles in the blood. Errors due to these effects are relatively insignificant except for errors in calculated arterial PO(2), particularly when SpO(2) is greater than 97%; and errors when the change in base excess across the sampling site due to strong acid production is greater that 1.3 mmol/l.     

Estimation of measurement errors in orthotropic elastic moduli determined from natural frequencies

Orthotropic elastic moduli of composite structures can be identified by nonlinear least squares fit between measured and computed natural frequencies. However, due to measurement errors contained in the measured natural frequencies and mode shapes, the process of elastic moduli identification is error-prone. This paper proposes an efficient method to estimate the errors in the elastic moduli caused by the measurement errors in the natural frequencies. The method utilizes an efficient semi-analytic expression of the sensitivities of the eigenvalues with respect to the orthotropic elastic moduli. First, the first-order approximation of the analytic sensitivity of orthotropic elastic moduli with respect to the measurement errors is introduced. The approximation is then used to estimate the variability of the identified elastic moduli due to the measurement errors. It is shown that the aspect ratio of the test specimen greatly affects the standard deviation of the identified elastic moduli. Second, using the first-order approximation, the effects of aspect ratio of the test specimen as well as the values of the elastic moduli are further investigated. Based on the results of numerical experiments, guidelines for the dimension of the test specimen for the elastic moduli identification are proposed.     

基于传感器响应校正的阅读环境照度测量研究

设计实现了阅读环境光度测量装置.用Canon SC50HS相机、BENETECH—GM1020型数字式照度计、标准灰板进行光度测量和标定,编制了基于LuxLAB,OriginLab软件平台的计算机采集和数据处理等程序.结合高校阅读光照环境的质量检测和评价问题,提出了区域平均法、传感器响应两点校正法的测量方法,并对测量操作误差进行了分析和验证,因位置不准确造成的误差在-3%~3%之间,实际可控制在2%左右.进行了自然采光、人工照明等典型情况下照度测量和阅读光环境的照明效果实验.比照国际CIE阅读光度标准,结合实际测量和结果,进行了阅读光环境数据分析评价.在光度测量检测、阅读光照环境评价和改进等方面具有重要参考价值.     

基于激光位移传感器的小转角测量方法研究

针对结构刚度测试中的转角测量问题,提出了一种新的小转角测量方法。采用激光位移传感器测量待测物体的切向线位移值,再通过几何关系将其转换成转角值。建立了包含4个因素的误差数学模型,分析了±1°的测量范围内各误差因素分别对测量结果的影响,结果表明：光斑距刻线标志偏距Δl对误差的影响较大。应用本方法,针对一异形构件进行了扭转刚度测试,当Δl上下限为±1 mm时,测量误差在2%左右,验证了本方法的有效性和准确性。     

Compensation of the RLS algorithm for output nonlinearities

It is shown how the recursive least squares (RLS) algorithm can be modified to compensate for a priori known errors of linearity in the output measurement. A novel signal model is used for this purpose. Only the nonlinear effects are modeled by an output error model, and much of the output measurements are used directly in the regression vector. The main benefit with this approach is that the advantages of the RLS, like quick initial convergence for infinite impulse response models, can be retained for small linearity errors. At the same time the output nonlinearity is allowed to be noninvertible. This can be important to treat, for example, small deadzones and also to avoid the amplification of additive measurement disturbances. Such amplification can result from inversion of the output nonlinearity. Simulations illustrate the performance of the algorithm     

Laplace random effects models for interlaboratory studies

A model is introduced for measurements obtained in collaborative interlaboratory studies, comprising measurement errors and random laboratory effects that have Laplace distributions, possibly with heterogeneous, laboratory-specific variances. Estimators are suggested for the common median and for its standard deviation. We provide predictors of the laboratory effects, and of their pairwise differences, along with the standard errors of these predictors. Explicit formulas are given for all estimators, whose sampling performance is assessed in a Monte Carlo simulation study.     

On the estimation of the linear relation when the error variances are known

The problem of consistent estimation in measurement error models in a linear relation with not necessarily normally distributed measurement errors is considered. Three possible estimators which are constructed as different combinations of the estimators arising from direct and inverse regression are considered. The efficiency properties of these three estimators are derived and the effect of non-normally distributed measurement errors is analyzed. A Monte-Carlo experiment is conducted to study the performance of these estimators in finite samples.     

面向测量误差模型的外生变量估计方法

从观察数据中发现因果关系在近年来得到了越来越多学者的关注,其中外生变量在理解因果机制中扮演者重要的角色。然而,现有的因果发现方法大多假设观察变量就是真实发生的因(果)变量,忽略了测量误差带来的影响。为此,提出了一种解决测量模型下的外生变量估计方法。通过引入triad约束,根据此约束来找出与其余所有相关成对变量都满足triad约束的变量,即外生变量。该算法不仅能够解决含有测量误差数据的估计问题,而且对于没有测量误差的数据仍然适用。实验将该算法应用于真实网络产生的数据中,结果表明,无论变量是否含有测量误差,提出方法均优于现有的其他算法。同时,基于移动基站的真实数据实验也验证了算法的有效性。