机床误差检测系统的动态不确定度研究

介绍了测量不确定度的定义及内容,借助于灰色系统理论的特点,着重探讨了检测系统的动态不确定度的计算步骤和方法.结合自主研发的数控机床热误差实时补偿检测系统,对车削加工中心热误差进行了测试,通过获得的测试数据来进行动态不确定度分析和研究,最终得出了检测系统的动态不确定度表达式,并与其静态不确定度进行了比较.分析了产生误差原因,通过残差修正进一步提高了动态不确定度的精度.为科学地评价检测系统、提高检测系统的有效性提供了依据.     

刨花板吸水厚度膨胀率检测不确定度研究

根据JJF1059.1-2012《测量不确定度评定与表示》要求，对刨花板吸水厚度膨胀率的检测不确定度进行分析。根据刨花板吸水厚度膨胀率的数学计算模型，分析试验过程，确定影响检测结果不确定度的因素有千分尺测量误差、恒温水槽控温误差、操作人员操作误差等。对P2型刨花板进行2 h吸水厚度膨胀率检测，结果表明试验条件下P2型刨花板吸水厚度膨胀率检测结果的扩展不确定为0.1%。     

矿用风速传感器信号传输误差的不确定度评定

矿用风速传感器的信号传输误差直接影响煤矿监控系统监测数据的准确可靠,关系着煤矿的安全生产。通过分析检测过程中影响信号传输误差不确定度的输入量,建立测量模型,利用实际检测数据,进行测量不确定度评定。     

平均值法交流共模抑制比测量不确定度评定北大核心CSCD

介绍了使用幅度绝对值的平均值法进行数据采集系统交流共模抑制比的测量不确定度分析和评价过程。使用测量幅度绝对值的平均值计算干扰分量值和本底噪声分量值,并采用直接代数相减方式剔除本底噪声的影响。讨论了主要的不确定度来源,包括信号源误差、数据采集系统增益误差、幅度测量误差、幅度分辨力误差,以及测量重复性等,给出了不确定度模型。并结合一个实例,给出了交流共模抑制比的不确定度评价结果。     

非正交轴系全站仪坐标测量系统误差分析技术研究

基于非正交轴系全站仪坐标测量系统的结构特点和测量模型,用数学分析的手段对其进行误差分析和测量不确定度评定。确定系统的主要误差分量是转台旋转角误差和激光跟踪仪测距值误差,并用GUM法评定各分量的不确定度。通过测量模型推导出系统的测量不确定度,并用MATLAB进行仿真,结果表明:当测距值不变时,测量不确定度几乎不受水平角变化的影响,而随着垂直角绝对值的增大而增大,当角度值不变时,测量不确定度随着被测点到视准轴上标定点的距离值增大而增大。实验初步验证了仿真结果的准确性。     

端基直线法测量直流增益和直流偏移的不确定度

介绍了用端基直线法评价线性测量系统直流增益和直流偏移指标时,测量结果的不确定度,包含了测量结果的不确定度分析和评价过程.讨论了影响评价结果不确定度的几个主要误差来源,包括信号源误差、被校系统测量误差、被校系统量化误差的影响等等,给出了端基直流增益和直流偏移测量结果的不确定度.在一个实际评价例子上,给出了直流增益和直流偏移指标不确定度分析和评价结果;不确定度验证表明了该过程的正确性和切实可行性.该过程及结论可应用在对于计量标准进行直流增益和直流偏移指标的不确定度分析上.     

苯气体检测报警器的应用及测量值的不确定度评定

文章对苯的性质、危害以及测量方法做了简要阐述,介绍了苯气体检测报警器的工作原理、分类和选择原则。文章列出所有影响测量苯气体检测报警器相对示值误差校准结果的影响量,并给出用以评定测量不确定度的测量模型,评定各输入量的标准不确定度,最后给出合成标准不确定度和扩展不确定度。     

基于最小二乘法的大型平板平面度误差自动检定系统

介绍了平板平面度误差的检测方法,研制了基于最小二乘法的大型平板平面度误差自动检定系统。详细阐述了系统结构、工作原理和平面度误差的最小二乘法评定过程,评定了测量结果的不确定度。实验对比结果显示了该系统的优势及其应用价值。     

直流增益和直流偏移的不确定度

介绍了用最小二乘法评价线性测量系统直流增益和直流偏移指标时测量结果的不确定度分析和评价过程。讨论了影响评价结果不确定度的几个主要因素 ,包括信号源误差、被校系统量化误差、被校系统重复性影响、非线性误差影响等等。对一个实例 ,给出了直流增益和直流偏移几项指标不确定度分析和评价结果。该过程及结论可用于分析计量标准相应指标的不确定度 ,也可用于估计直流增益和直流偏移的测量不确定度     

超声波检测焊缝缺陷深度的不确定度评定

采用GUM法对超声波检测焊缝缺陷深度的测量不确定度来源进行了分析,并对检测过程中的测量不确定度进行了评定。结果表明:超声波检测焊缝缺陷深度的不确定度来源主要有超声波探伤仪水平线性误差、斜探头性能以及试块规格;为了得到精确的测量结果,测试前应对超声波探伤仪水平线性误差进行检查并确保其在合适范围内,然后选用合适的探头及试块。     

Probabilistic Fatigue Life Prediction and Structural Reliability Evaluation of Turbine Rotors Integrating an Automated Ultrasonic Inspection System

The paper presents a general method and procedure for fatigue reliability assessment integrating automated ultrasonic non-destructive inspections. The basic structure of an automated ultrasonic inspection system is presented. Fatigue reliability assessment methodology is developed using uncertainty quantification models for detection, sizing, and fatigue model parameters. The probability of detection model is based on a classical log-linear model coupling the actual flaw size with the ultrasonic inspection reported size. Using probabilistic modeling, the distribution of the actual flaw size is derived. Reliability assessment procedure using ultrasonic inspection data is suggested. A steam turbine rotor example with realistic ultrasonic inspection data is presented to demonstrate the overall method. Calculations and interpretations of assessment results based on risk recommendations for industrial applications are given.     

航天器单机产品真空室检漏法测量结果的不确定度评定

航天器推进系统的单机产品的漏率测试往往采用氦质谱真空室检漏法,研究该方法测量结果的不确定度评定具有重要的工程应用价值。本文首先对真空室检漏法的原理进行了分析探讨,并从不确定的基础理论出发系统地研究了氦质谱真空室检漏法测量结果的不确定度评定方法,并结合工作的具体案例给出了评价的具体步骤。     

需求和供应不确定下的选址研究

在需求不确定的同时,考虑了由于意外事件导致设施失灵而造成的供应不确定性,提出了这两个不确定因素下的设施选址模型.已知各个设施的失灵风险概率,通过情景规划描述需求不确定性,在保证供应系统的稳定性和鲁棒性不低于既定值的情况下,使得运输费用和设施失灵不能提供服务时的风险费用之和最小,提出了拉格朗日松弛算法,并通过大量算例验证...     

Uncertainty Modelling of the Reference Pressure Generating with OIML and ASTM Weights in Pressure Balances

A pressure balance is a combined with a piston-cylinder unit and a system for the application of a vertical load on the piston. Pressure balances are primary measuring systems those measure pressure in terms of force per unit area. Reference pressure can be generated by a pressure balance. There are many parameters to calculate reference pressure, such as piston’s area, linear deformation of piston and cylinder, measuring temperature, mass, local gravity, surface tension of measuring liquid… All of these parameters have got measurement uncertainty, effects of these uncertainty components must be added to the uncertainty budget of reference pressure. In this study, the uncertainty model function of reference pressure is derived. And the uncertainty model function is rearranged. If the masses of pressure balance are calibrated according to the OIML R-111 or ASTM E-617 guides, the uncertainty model function that is given in the study can be used directly to calculate uncertainty of reference pressure.     

A probability model of system downtime with implications for optimal warranty design

Traditional approaches toward modeling the availability of a system often do not formally take into account uncertainty over the parameter values of the model. Such models are then frequently criticized because the observed reliability of a system does not match that predicted by the model. This paper extends a recently published segregated failures model so that, rather than providing a single figure for the availability of a system, uncertainty over model parameter values is incorporated and a predictive probability distribution is given. This predictive distribution is generated in a practical way by displaying the uncertainties and dependencies of the parameters of the model through a Bayesian network (BN). Permitting uncertainty in the reliability model then allows the user to determine whether the predicted reliability was incorrect due to inherent variability in the system under study, or due to the use of an inappropriate model. Furthermore, it is demonstrated how the predictive distribution can be used when reliability predictions are employed within a formal decision‐theoretic framework. Use of the model is illustrated with the example of a high‐availability computer system with multiple recovery procedures. An BN is produced to display the relations between parameters of the model in this case and to generate a predictive probability distribution of the system's availability. This predictive distribution is then used to make two decisions under uncertainty concerning the offered warranty policies on the system: a qualitative decision and an optimization over a continuous decision space. Copyright © 2009 John Wiley & Sons, Ltd.     

A review of different perspectives on uncertainty and risk and an alternative modeling paradigm

The literature in economics, finance, operations research, engineering and in general mathematics is first reviewed on the subject of defining uncertainty and risk. The review goes back to 1901. Different perspectives on uncertainty and risk are examined and a new paradigm to model uncertainty and risk is proposed using relevant ideas from this study. This new paradigm is used to represent, aggregate and propagate uncertainty and interpret the resulting variability in a challenge problem developed by Oberkampf et al. [2004, Challenge problems: uncertainty in system response given uncertain parameters. Reliab Eng Syst Safety 2004; 85(1): 11-9]. The challenge problem is further extended into a decision problem that is treated within a multicriteria decision making framework to illustrate how the new paradigm yields optimal decisions under uncertainty. The accompanying risk is defined as the probability of an unsatisfactory system response quantified by a random function of the uncertainty.     

嫦娥一号激光高度计在轨月球高程数据测量不确定度研究

对嫦娥一号激光高度计月球表面在轨高程探测数据进行了误差分析处理和不确定度评定研究。首先,选择了月海平坦地形区域的激光高度计高程数据;然后分析了主要的探测不确定度来源,建立了相应数学模型;最后采用了蒙特卡洛方法(MCM)进行了不确定度评定研究,给出了某些月海区域高程探测不确定度评定结果,并与测量不确定度表示指南方法(GUM)进行对比。研究结果表明:MCM评定方法与GUM方法结果基本一致;处理结果也能和其他月球探测结果进行对比研究,希冀对月球及空间环境有更多、更新的发现。     

A stochastic framework for hydraulic performance assessment of complex water distribution networks: Application to connectivity detection problems

This paper is concerned with the hydraulic performance assessment of large scale water distribution networks in presence of uncertainty. In particular, the associate connectivity detection problem is examined in detail. For this purpose, a Bayesian system identification methodology is combined with an efficient hydraulic simulation model. A number of hydraulic model classes are defined as potential connectivity events. Based on information from flow rates in the pipes, the proposed updating technique provides estimates of the most probable connectivity scenarios. Such scenarios correspond to the model classes that maximize their evidences or posterior probabilities. The effectiveness of the proposed identification framework is illustrated by applying the connectivity detection approach to a real water distribution system.     

基于圆判据的超空泡航行体非线性控制研究

超空泡航行体在高速航行过程中大部分表面被空泡包裹,航行体尾部与空泡间相互作用产生剧烈变化的滑行力,该滑行力是导致航行体失稳的主要因素。由于航行体与空泡相互作用机理的复杂性,使得滑行力表达式存在很大的建模差异和参数不确定性,针对这一问题,该文首先通过一系列变换将系统模型表示为线性环节和非线性环节反馈连接的形式,然后基于圆判据定理给出了航行体绝对稳定的充分条件,并依据该条件采用状态反馈极点配置方法设计控制器。仿真结果表明,该控制器针对滑行力建模不确定性和参数不确定性的情况,可以通过合理配置闭环极点实现系统对不同非线性条件的绝对稳定。     

A simulation-based experimental investigation of supply/timing uncertainty in MRP systems

The uncertainty inherent in material requirements planning (MRP) systems is of two general types: demand uncertainty and supply uncertainty. Supply uncertainty is a result of late deliveries (timing) or order shrinkage (quantity) or both. The purpose of this paper is to examine the impact of operating policies on an MRP system given supply uncertainty resulting from timing factors, specifically the uncertainty caused by variability in the lead time of purchased parts. Experiments arc conducted to assess the impact of four factors: the amount of lead time variability, the amount of safety stock or safety lead time, the lot-size rule, and the holding cost and lateness penalty, on the total cost of the MRP system given supply/timing uncertainty. An MRP/Production simulator is employed to perform the experiments. Practical guidelines for the manager of an MRP system with supply/timing uncertainty are presented.