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 of measurement by Monte-Carlo simulation and metrological reliability in the evaluation of electric variables of PEMFC and SOFC fuel cells

The aim of this work is presenting results of uncertainty of measurement calculations applied to both a low temperature PEMFC (proton exchange membrane fuel cell) and a high temperature SOFC (solid oxide fuel cell) by using Monte Carlo method simulations. The intention is correlating electric voltage, obtained in the technical literature, and energetic efficiency of the fuel cells studied in this work. In order to validate the Monte Carlo results achieved a comparison with the procedure for the evaluation of the uncertainty of measurement existing in the GUM 95 ”Guide to the Expression of Uncertainty in Measurement” (by BIPM, IEC, IFCC, ISO, IUPAC, IUPAP and OIML) is made. A reasoning of the balancing of the sources of uncertainty is presented as well. In last, it is discussed why the calibration process and traceability of the voltmeter are key factors in providing reliable metrological results in the production of electricity by fuel cell technology. This work is the first part of a broader study from which the next steps will be the validation of these presented simulations by fuel cell bench tests and the planning and development of Brazilian Conformity Assessment programs for PEMFC and SOFC fuel cells afterwards.     

航空发动机全流程参数试验中温度和压力测量综述

航空发动机全流程参数测量是发动机研制阶段的重要环节,是全面了解发动机性能的唯一手段。国内外各大发动机研究机构和工厂对此都非常重视并相当保密。对国内外航空发动机全流程参数测量发展状况进行了介绍,主要对试验中发动机温度和压力的测量技术进行了归纳和分析。     

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.     

机械零件可靠性试验数据的参数估计

本文介绍了可靠性试验数据的两种参数估计方法──回归分析法和最大似然值法。笔者采用最优化方法求三参数威布尔分布的似然函数的极值点及相关系数，取得了正确的结果。     

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.     

电动舵机减速器扭矩测量误差分析与补偿

减速器的扭矩输入输出特性是衡量电动舵机性能的重要指标.在测量实验中,由于机械安装,轴承摩擦和电机驱动器非线性等原因造成的误差会折算到扭矩测量结果中,导致扭矩测量误差并降低精度.以减速器为研究对象,通过动态方程建立电动舵机系统的数学模型,提出将扭矩测量误差进行分离,令机械安装与轴承摩擦作为已知的系统误差,最终得到电机驱动器误差的观点,采用基于最小二乘的曲线拟合算法,对实测静态和动态数据进行预处理从而对扭矩测量误差进行补偿.实验结果说明此方法能够补偿电机驱动器非线性引入的测量误差从而提高测量精度.     

航空发动机起动试车台的研制

设计某型航空发动机起动试车台,介绍了试车台的组成、工作原理、技术难题及解决方法;该型航空发动机起动试车台工作稳定可靠,能完全满足航空发动机起动试车技术要求。     

基于固定方差展开的提升机主轴装置可靠性优化设计

针对概率信息不完备条件下提升机主轴装置的可靠性优化设计问题,提出了一种基于固定方差展开的提升机主轴装置可靠性优化设计方法,首先,通过将提升机主轴装置强度失效的可靠性功能函数进行方差展开,获得了可靠性功能函数的前三阶矩;其次,采用基于矩的鞍点逼近方法,计算得到了主轴装置的失效概率;最后,结合优化设计方法,建立了以可靠度为...     

工程机械发动机检测适配器的设计

设计一套工程机械发动机检测适配器,介绍了该系统的硬件结构、检测方案以及系统的工作原理。该系统在通用检测平台和相应检测维修流程的配合下,可对处于不拆卸状态的工程机械发动机进行技术状态检查和故障诊断,将故障定位到独立设备和可更换单元(或组合)。实践表明:该系统方便快捷,提高了测试效率,具有较高的实用价值。     

利用可靠性筛选试验提高刀具可靠性的研究

利用可靠性筛选试验对刀具进行预选,可以提高一批刀具的可靠性。这里从理论上对可靠性筛选试验的筛选时间进行了分析,并通过试验对其选择进行了研究。     

小子样产品可靠性Bayes评定中的相容性检验方法研究

从工程实践的角度,讨论了小子样场合的产品可靠性Bayes评定中的相容性检验方法,提出了一种参数方法和两种非参数方法.最后通过两个实例说明了各种方法的正确性和可行性.     

CVT金属带钢环疲劳试验数据可靠性分析

在CVT金属带钢环疲劳试验数据的基础上,通过作图法和数值分析法检验,确定了钢环寿命符合对数正态分布;采用解析法和作图法估计了分布函数参数,并得到了钢环的可靠寿命表达式.     

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.     

Effect and measurement of the machine compliance in the macro range of instrumented indentation test

The contribution concerns the strong effect of the machine compliance in the upper macro range of the instrumented indentation test on hard materials. To achieve a minimum uncertainty in determination of the machine compliance the measurement and analysis needed for the determination are studied in detail. Based on the assumption that the hardness and/or the indentation modulus are force independent, four methods on the determination of the machine compliance are described. Experimental results of a commercial testing machine up to 2500 N and of a standard machine up to 200 N are analyzed. The results show that the uncertainty of the compliance is usually higher than requested for a precisely enough determination of hardness and further materials parameters. Especially for the calibration of reference materials with high hardness and/or Young’s modulus, the machine compliance should be limited in ISO 14577 part 3, 2003 [1].     

浅谈影响发动机试验数据准确性的几种因素

发动机试验,是用科学的试验方法揭示发动机内部的变化规律,找出提高其动力性、经济性、可靠性等各种性能的途径.从准备阶段到试验,再到试验后的数据处理,都存在着影响发动机试验数据准确性的因素:发动机的技术状态、安装位置、机油的添加量等会影响发动机的性能;试验人员的技术水平,测试仪器、试验方法的选择等会影响测试结果;试验条件的控制,测试数据的处理方法等也会影响测试结果.通过对试验全过程的分析可知,影响数据准确性的因素主要可分为样品、检测人员、测试仪器、试验方法及数据处理,试验环境和设施条件等几个方面.     

小型汽油发动机性能测试台

针对1E34F型小型汽油机研制了一套发动机性能测试台。应用相位差式扭矩转速传感器和液位变送器来测量发动机的扭矩、转速、功率和油耗。并以扭矩仪作为信号处理中心,测量数据存储并显示在计算机上。该套测试台可以全面反映发动机的综合性能。     

柴油机清洁度与可靠性问题浅析

笔者通过对柴油机检修、组装、试验过程中的清洁度分析,得出预防柴油机碾瓦事故的有效措施是提高柴油机在检修过程中的清洁度,这是确保柴油机检修质量必须加以控制的项目。     

柴油甲醇双燃料发动机动力性与经济性试验分析

介绍了柴油引燃甲醇双燃料燃烧对柴油机动力性和经济性的影响。在1台单缸、直喷、中冷柴油机上采用柴油引燃甲醇双燃料进行试验。结果显示甲醇柴油双燃料发动机在中高负荷及中高转速下运转可获得较好的燃油经济性。选择适当的引燃柴油量,双燃料发动机的动力性可以达到甚至超过原柴油的动力性。     

发动机活塞温度场试验与有限元分析

依据发动机活塞的热负荷,介绍热电偶法测量活塞温度的试验方法和过程,建立活塞有限元模型,分析热边界条件的施加方法。计算结果与试验结果很好地拟合,为发动机活塞的耦合分析和结构优化提供了可靠依据。