测量不确定度引起的抽样检验误判率计算

为合理配置测量资源,提高产品检验结果的可靠性,对抽样检验中测量不确定度引起的误判风险进行了量化评估。分析了抽样检验中可能存在的各种风险,重点对测量不确定度的影响进行了讨论;分别针对检验前误判率预估和检验结果误判率计算两种应用情况,提出了误判率计算公式;以产品尺寸合格性检验为例,进行了误判率计算和分析。结果表明,抽样检验误接收和误拒收概率均随测量不确定度的增大而增大,产品检验前应根据可接受误判率合理选择测量方法;对具体产品批的合格性判定结果,应同时计算对应的误判率,以保证产品检验结果的可靠性。     

基于新一代GPS的产品检验符合性不确定度评定*

新一代产品几何技术规范将测量不确定度的概念拓展至符合性不确定度,但并未给出相对应的评定方法。为全面估计产品检验中测量结果与产品规范所有可能的差异,基于新一代产品几何技术规范,研究产品检验符合性不确定度评定。基于产品几何技术规范定义,提出规范不确定度、方法不确定度、符合性不确定度的评定方法;借助不确定度的黑箱模型,通过测量结果统计学量值特性指标,评定执行不确定度。以产品圆度检验为例,研究符合性不确定度评定操作过程,基于符合性不确定度划分产品检验的合格区间。实例分析结果表明,规范不确定度和方法不确定度的量值与执行不确定度相当,不可忽略;由于符合性不确定度包含测量结果与图纸规范所有可能的不一致性,基于符合性不确定度进行产品合格判定更为可靠。     

GPS不确定度理念在自动检测分选技术中的应用

测量不确定度是产品几何量技术规范(GPS)不确定度的重要组成部分,位于规范限附近存在一个不确定区,位于不确定区的测量结果会出现一定概率的误判现象。在测量不确定度基础上,提出了将ISO/TS 14253-1制定的按规范检验合格与不合格的判定规则应用于自动检测分选技术中。与传统的极限判定原则相比,本文给位于不确定区的测量结果提供了一个合理有效的判定原则,误判现象得到明显改善。本文以自主研制的活塞环自动分选仪作为实验平台,分别按照极限判定原则与按规范检验合格与不合格的判定规则对活塞环闭口间隙进行自动检测分选。结果表明:将测量不确定度应用于自动检测分选技术中,可以明显改善由于存在测量不确定度所引起的对测量结果误判的现象。     

基于新一代GPS的表面粗糙度Ry评定研究

目前的表面粗糙度Ry(轮廓最大高度)往往只给出检验结果,而没有考虑检验结果的不确定因素.为了保证Ry测量结果的完整性和有效性,根据新一代GPS原理,提出了一种表面粗糙度Ky测量不确定度的计算方法.该方法依据表面粗糙度最小二乘检验的基本原理计算检验结果,并根据ISO/TS 14253-2给出的不确定度传递公式计算检验结果的不确定度.实验结果表明,Ry的测量结果及其不确定度可以依据ISO14253-1给出的判定原则定量地判定产品是否合格,从而减少产品的误收和误废.     

双重公差原则同轴度误差评定的不确定度研究

为了全面地分析影响产品合格性的可能因素,使零件在满足可装配性的情况下降低加工成本,基于双重公差原则同轴度误差评定方法,对零件的依从不确定度进行了研究。根据规范不确定度的定义,充分考虑其组成因素中的提取、拟合和滤波规范,通过极差法求得相应的规范不确定度分量,并合成规范不确定度;采用正交设计的方法,根据优化后的测量方法评定方法不确定度;借助不确定度的黑箱模型,计算执行不确定度分量;最后将上述三种不确定度合成依从不确定度,并进行了实例验证。实验结果表明,该方法可以更全面地分析影响产品合格性的可能因素,从而提高产品检验的合格率,降低其加工成本。     

平面度坐标测量的不确定度计算

目前的坐标测量只是给出平面度最小二乘检验的结果,并没有给出检验结果的不确定度.根据平面度最小二乘检验的基本原理和ISO/TS 14253-2给出的不确定度传递公式,提出了一种平面度坐标测量的不确定度的计算方法.该方法的特点是将平面方程的系数看作一个随机向量,通过计算该随机向量的均值和协方差矩阵来确定平面方程和平面度的检验结果及其不确定度.这不仅保证了平面度检验结果的完整性,而且符合新一代产品几何规范(GPS)标准的要求,从而可以提高工件检验的准确性.实验结果表明,根据平面度最小二乘检验的结果及其不确定度,可以根据ISO 14253-1给出的判定原则定量地判定平面是否合格.     

MATLAB与WinBUGS在贝叶斯方法测量不确定度评定中的应用

针对贝叶斯方法仪器测量不确定度评定计算的复杂性,分析基于蒙特卡罗的贝叶斯测量不确定度评定实现方法;应用MATLAB软件和WinBUGS软件实现测量不确定度分布的传递,并应用WinBUGS软件与MATLAB软件的接口程序,实现MAT LAB对WinBUGS程序的设置与控制。     

MC模拟法在热耗率测量不确定度评定中的应用

对于汽轮机组热耗率测量不确定度的评定,常采用传统不确定度传播律计算法,因水蒸汽性质计算模型比较复杂,使灵敏系数和各输入量间的相关系数难以确定,故热耗率测量的不确定度计算较为困难。基于此,采用一种基于随机试验和统计计算的数值方法即蒙特卡罗(MC)模拟法对汽轮机组热耗率测量不确定度进行评定。将采用该方法进行的评定结果与ASME PTC6-1996中的算例进行比较,得出"评定结果与该例的相对扩展不确定度值相近"的结论,验证了MC模拟法在热耗率测量不确定度评定中的简单有效性。     

不确定度在链长精度测量中的应用

一个完整的测量结果应包含测量不确定度,测量不确定度的大小决定了测试结果的可信程度。对于不同产品和测试方法,影响测量不确定度的因素以及不确定度的计算方法不同。在链条行业链条产品的链长精度测量中首次引入不确定度,通过大量的试验测试和理论分析,找出了影响不确定度的主要因素。在此基础上,根据贝塞尔公式得出计算链长精度不确定度的理论公式,给出了不确定度在报告中的表述方法,讨论了不确定度对测量结果的影响。     

几何产品测量不确定度的混合熵评定方法

针对几何产品测量不确定度的评定,提出基于混合熵的测量不确定度评定方法.该方法是在随机熵的基础上,考虑到模糊熵引起的不确定度,将二者有机结合,计算出总体不确定度值.通过实例验证,结果表明,基于混合熵的测量不确定度评定方法合理、可靠,有效地减少了检验过程中产品零件的误收和误废.     

Probabilistic measurement evaluation for the implementation of the Measuring Instrument Directive

The approval of the European Measuring Instrument Directive (2004) constitutes a noteworthy novelty in legal metrology, since this Directive implements the so called “new approach” to technical normalization and harmonization and moves toward a “global approach” to evaluation and conformity. According to the principles of the new approach regulatory model, the Directive establishes some essential requirements for a wide class of measuring devices, subject to legal control, whilst leaving manufacturer free to develop proper technical solutions for meeting them. Moreover, the conformity of instruments to prescribed requirement may now be ensured through quality assurance procedures, in the context of a quality system. This increase in technical and metrological freedom on the manufactures side may promote innovation, social benefit and costumers’ satisfaction, provided that some recent advances in measurement theory are properly employed.In this paper, after a brief discussion regarding the philosophy of the Directive, a probabilistic approach to conformity assessment is presented. The proposed approach concerns some currently open issues such as measurement uncertainty due to the influence of operating conditions, the assessment and reduction of the risk related to measurement uncertainty in conformity decision and the costs of instrument uncertainty and of non-conformity, for both the manufacturer and the user. The approach is supported by a package of software codes that assists the application of verification procedures, with a user-friendly approach.All these aspects are discussed with reference to the case of water meters, considering both end-of-production acceptance tests and the performance of meters under operation.     

Estimation of non-statistical uncertainty in precision measurement using grey system theory

A new uncertainty assessment method is proposed to characterize non-statistical uncertainties in precision measurement. The proposed method is based on grey system theory to address the problem involved in uncertainty assessment where the sampling size is small and the distribution of the data is unknown. The advantage of the proposed approach is that the requirements of the statistics based methods are removed. In the proposed method, an accumulated true size vector and an accumulated measurement data vector are established to reduce the effects of the errors in the measurement and in the numerical calculation. The uncertainty assessment is based on the l norm of the difference between the accumulation of the sorted measurement data vector and that of the true size vector. A number of computational and experimental tests were carried out. The results demonstrated the effectiveness and consistency of the proposed method in non-statistical uncertainty assessment, compared with the existing methods.     

基于微分几何的离合器接合过程速度跟踪滑模控制

针对离合器控制系统中存在的非线性、外部干扰和参数不确定问题,提出了基于微分几何的离合器接合过程速度跟踪滑模控制方法。考虑系统参数的不确定性和外界干扰等不确定因素,建立了单个离合器起步动力学模型;基于微分几何的反馈线性化方法,得出系统的控制律;采用基于趋近律的滑模控制方法,设计了存在不确定干扰的离合器控制系统滑模控制器。利用Lyapunov理论对系统的稳定性进行了证明。仿真结果表明该控制器使离合器接合过程的速度跟踪精度高,且鲁棒性好。     

Monte carlo method for the uncertainty evaluation of spatial straightness error based on new generation geometrical product specification

Straightness error is an important parameter in measuring high-precision shafts. New generation geometrical product specification(GPS) requires the measurement uncertainty characterizing the reliability of the results should be given together when the measurement result is given. Nowadays most researches on straightness focus on error calculation and only several research projects evaluate the measurement uncertainty based on "The Guide to the Expression of Uncertainty in Measurement(GUM)". In order to compute spatial straightness error(SSE) accurately and rapidly and overcome the limitations of GUM, a quasi particle swarm optimization(QPSO) is proposed to solve the minimum zone SSE and Monte Carlo Method(MCM) is developed to estimate the measurement uncertainty. The mathematical model of minimum zone SSE is formulated. In QPSO quasi-random sequences are applied to the generation of the initial position and velocity of particles and their velocities are modified by the constriction factor approach. The flow of measurement uncertainty evaluation based on MCM is proposed, where the heart is repeatedly sampling from the probability density function(PDF) for every input quantity and evaluating the model in each case. The minimum zone SSE of a shaft measured on a Coordinate Measuring Machine(CMM) is calculated by QPSO and the measurement uncertainty is evaluated by MCM on the basis of analyzing the uncertainty contributors. The results show that the uncertainty directly influences the product judgment result. Therefore it is scientific and reasonable to consider the influence of the uncertainty in judging whether the parts are accepted or rejected, especially for those located in the uncertainty zone. The proposed method is especially suitable when the PDF of the measurand cannot adequately be approximated by a Gaussian distribution or a scaled and shifted t-distribution and the measurement model is non-linear.     

The use of measurement uncertainty and precision data in conformity assessment of automotive fuel products

In order to use a test result to decide whether it indicates compliance or non-compliance, it is necessary to take into account the dispersion of the values that can be attributed to the measurand. When dealing with conformity assessment of automotive fuel samples against European Union specification limits, this dispersion may be represented by uncertainty estimates based on either standard method precision data (ISO 4259 approach) or within laboratory precision data (intermediate precision approach). The present work presents possible decision rules based on these approaches and directly related to the required or acceptable level of probability of making a wrong decision. Acceptance limits for 95% and 99% confidence levels are calculated for all the properties of automotive fuels. Moreover, the effect of different approaches for defining guard bands, different levels of confidence or different number of replicate measurements is investigated using the results of the analyses of 769 diesel fuel samples for the determination of sulfur mass concentration.     

User interface for optical multi-sensorial measurements at extruded profiles

Nowadays the process control of concave extruding is a measuring task with rising requirements. A novel optical bi-sensorial measurement system - consisting of a shadow- and a light-section-system - as well as suitable methods of analysis for the in-line inspection are presented. The proposals help to ensure the product quality on a higher level than before. The combination of dimensional accuracy and data-density leads to excellent results. The optical multi-sensor measurement system has to be calibrated and aligned to detect the same surface zone despite of high refresh rates and optical resolutions. The metered characteristics will be coordinate transformed to extrinsic world-coordinates for evaluating form deviations of complex parts. An appropriate user interface enables to re-calculate measurement objects in-line and evaluate the conformity of the part consequently. Finally the real length information assists to influence the process control. After successful test in laboratory the results will be proved in production to the target: measurement uncertainty of better 0.1 mm at every profile.     

Adaptive Monte Carlo and GUM methods for the evaluation of measurement uncertainty of cylindricity error

Measurement uncertainty is one of the most important concepts in geometrical product specification (GPS). The “Guide to the expression of uncertainty in measurement (GUM)” is the internationally accepted master document for the evaluation of uncertainty. The GUM method (GUMM) requires the use of a first-order Taylor series expansion for propagating uncertainties. However, when the mathematical model of measurand is strongly non-linear the use of this linear approximation may be inadequate. Supplement 1 to GUM (GUM S1) has recently been proposed based on the basis of probability density functions (PDFs) using the Monte Carlo method (MCM). In order to solve the problem that the number of Monte Carlo trials needs to be selected priori, adaptive Monte Carlo method (AMCM) described in GUM S1 is recommended to control over the quality of the numerical results provided by MCM.The measurement and evaluation of cylindricity errors are essential to ensure proper assembly and good performance. In this paper, the mathematical model of cylindricity error based on the minimum zone condition is established and a quasi particle swarm optimization algorithm (QPSO) is proposed for searching the cylindricity error. Because the model is non-linear, it is necessary to verify whether GUMM is valid for the evaluation of measurement uncertainty of cylindricity error. Then, AMCM and GUMM are developed to estimate the uncertainty. The procedure of AMCM scheme and the validation of GUMM using AMCM are given in detail. Practical example is illustrated and the result shows that GUMM is not completely valid for high-precision evaluation of the measurement uncertainty of cylindricity error if only the first-order terms in the Taylor series approximation are taken into account. Compared with conventional methods, not only the proposed QPSO method can search the minimum zone cylindricity error precisely and rapidly, but also the Monte Carlo simulation is adaptive and AMCM can provide control variables (i.e. expected value, standard uncertainty and lower and higher coverage interval endpoints) with an expected numerical tolerance. The methods can be extended to the evaluation of measurement uncertainty of other form errors such as roundness and sphericity errors.