多轴微细铣削机床的精度设计方法研究

高精度机床是实现微细加工的基础,目前对其设计主要还是依赖于经验或直观地根据加工精度要求来选取各个运动轴的精度,不能满足多轴微细铣削机床设计的需要. 以精度分析与精度分配为主要内容的精度设计方法,针对一种新型桌面五轴联动微细铣削机床,构建主要包括各运动轴定位精度的运动误差模型,求解各运动轴精度对末端精度的影响分布趋势,完成精度分析. 基于末端运动精度要求和关键设计参数,合理设置直线轴与旋转轴的精度要求,在工作空间内分别对B轴和C轴依次进行精度求解,实现各运动轴的运动精度优化与分配, 指导设计时科学地对各运动轴零部件进行选型.此设计方法对于多轴联动的中大型机床设计也具有一定的推广价值．     

Classification of measuring devices by their accuracy

Conclusions It is proposed to divide the general criterion for the accuracy of measures and measuring instruments expressed by a conventional sign or number into two notations, those of accuracy categories and accuracy classes. Categories of accuracy should be assigned to such groups of measuring devices (sets of measures of various nominal values) for which it is impossible to establish a single-valued characteristic expressed in relative units or measurement units. Categories of accuracy represent a nominal characteristic and its content can only be determined by evaluating the relation between a scale of a certain grade of accuracy and the numerical parameters which determine the accuracy of measurement by means of a given device without introducing corrections. Classes of accuracy characterize devices for which a given error characterizes completely and in a single-valued manner their metrological properties.For a more complete metrological characterization of measures and measuring instruments, it is advisable to indicate on the measures or measuring instruments, or in their certificates, in addition to their nominal categories and classes also their ranges, scale factors, or scale values.It is possible to use a double classification system, i.e., to assign to a single measure or measuring instrument both its category and class of accuracy. It has already been pointed out that the category characterizes the degree to which a measure of measuring instrument approaches its maximum attainable accuracy with the existing technique for measuring the given physical value. The class of accuracy indicates the tolerated and actually attainable limiting measurement error.     

Automated sampling decision scheme for the AVM system

Reducing the sampling rate to as low as possible is a high priority for many factories to reduce production cost. Automatic virtual metrology based intelligent sampling decision (ISD) scheme had been previously developed for reducing the sampling rate and sustaining the virtual metrology (VM) accuracy. However, the desired sampling rate of the ISD scheme is fixed and set manually. Hence, whenever the VM accuracy gets worse, it cannot adaptively increase the default sampling rate in the ISD scheme. As a consequence, it would take more time to collect enough samples for improving the VM accuracy. Moreover, when the VM accuracy performs well all the time, it cannot automatically decrease the default sampling rate in ISD, which may result in unnecessary waste. Accordingly, this paper proposes an automated sampling decision (ASD) scheme to adaptively and automatically modify the sampling rate online and in real time for continuous improvement. The ASD scheme can monitor the VM accuracy online as well as update the VM models in real time for maintaining the VM accuracy when the VM accuracy becomes poor. Also, the ASD scheme can automatically reduce the sampling rate while the VM accuracy performs well.     

面向颜色再现的光谱降维方法研究

目的为了解决颜色信息光谱反射率的高维数给颜色再现过程带来的诸多问题。方法利用主流的光谱降维方法(主成分分析,Lab PQR,WSPCA,WSPCAplus),实现利于颜色再现的光谱信息筛选,从光谱精度、色度精度及变光源色差稳定性等3个方面评价这些降维方法。结果实验证明,主成分分析(PCA)法的光谱精度最高,光谱误差只有0.0076,但是在色度精度及变光源色差稳定性方面表现不好;Lab PQR法在光谱精度和色度精度间达到了很好的平衡,但是当变换光源时,其色差稳定性较差;WSPCA法去除了光源的影响,其变光源后色差变化不大,并且同时兼顾了色度精度,但以牺牲光谱精度为代价,WSPCAplus在其基础上将光谱精度提高为0.0081。结论研究结果对颜色再现过程中降维方法的选择具有一定的指导作用。     

回转运动坐标定位精度的检测与误差补偿模型

在对回转运动坐标定位精度的干涉测量原理和方法进行深入研究的基础上,采用激光干涉法检测混联机床C轴的定位精度和重复定位精度,并做出了基于测量数据的混联机床C轴单向均位偏差特性曲线,推导出了C轴顺、逆时针旋转定位误差数学模型。利用最小二乘法拟合得到了机床回转运动坐标目标位置的均值误差补偿数学模型,提出了一种回转运动坐标定位精度的激光干涉测量方法和误差补偿模型的建模方法。     

标题位置等因素对表图使用绩效的影响

考察表、图标题位置、数据复杂度和问题难度对表、图使用绩效的影响。49名大学生随机分为表格组和图形组。结果表明:(1)从表中提取信息更快、更准确,但对图中信息的回忆正确率更高;(2)标题位于上方时提取信息更快更准,回忆正确率也更高;(3)数据复杂度主要影响反应正确率;(4)对简单问题的反应既快又准,但回忆正确率较低。     

一种新颖的检测摆动运动动态精度的仪器

我们为某超大型、高精度的摇摆台研制了一台动态精度检测仪,该检测仪原理新颖、测试精度高、结构简单、使用方便,有很高的性能/价格比。 本文将简要介绍其检测原理、仪器结构、关键技术及质量评定。     

贴标机供标机构运动精度可靠性分析

应用运动精确度理论和可靠性理论,对贴标机的关键装置供标机构运动精度进行可靠性分析。根据平面机构的几何约束方程,采用矩阵法推导平面机构运动精度误差表达式,建立贴标机供标机构——连杆滑块机构运动位移精度和速度精度失效的极限状态方程,并构建该机构运动精度位移和速度可靠性模型。在考虑杆长加工误差的情况下,通过Matlab计算程序实现了贴标机供标机构的运动精度可靠度计算,迅速准确地得到机构位移可靠度和速度可靠度,并用Monte-Carlo法进行验证。结果表明：与Monte-Carlo法相比,本文方法的相对误差均小于0.5%。本文方法实用、有效。     

Forecasting Characteristics of User Equipment in Space Navigation Systems

A method is proposed for predicting the parameters characterizing the metrological characteristics of user equipment in space navigation systems. The method uses an interval form of expression for the measurement accuracy and it estimates not only the accuracy of the measurements but also provides an estimate of the confidence in it. Solutions are provided for the commoner cases of initial specifications for the accuracy of coordinate determination.     

基于像元分解的亚像元级遥感数据分类精度评估方法

为减小混合像元现象给遥感数据分类精度评估过程带来的影响,将像元分解技术引入到分类精度评估中,提出了基于像元分解的亚像元级分类精度评估方法,并给出了相应的处理流程及精度评估所需误差矩阵的计算方法.实验结果表明,亚像元级分类精度评估方法能够体现混合像元在分类精度评估过程中的影响,能够从一定程度上细化各分类算法的优劣,降低由于空间分辨率所引起的分类精度评估结果的不确定性.     

数控机床手动补偿误差的方法研究

为了减少数控机床精度损失及维护成本,以SIEMENS、FANUCK和FAGRO数控系统为例,采用双频激光干涉仪系统完成数控机床的精度检测,以手动补偿的方式修正数控机床的误差。根据双频激光干涉仪的测量原理,结合数控机床精度检测的方法及影响因素,对手动方式补偿数控机床误差的方法进行了分析说明。实验表明,手动方式补偿数控机床误差的方法实用,较为安全、可靠和经济。     

直流电动机在高精度光电跟踪系统中的应用

高精度光电跟踪系统用以完成对模拟动态目标的准确跟踪 ,要求跟踪元件响应快、动态性能好、精度高 ,因此跟踪元件的性能直接影响系统的跟踪特性和精度。直流力矩电机的优点是调速性能好 ,启动转矩大。正是这一特点 ,在高精度光电跟踪系统中尝试使用直流力矩电机控制反射镜跟踪目标。高精度光电跟踪系统要求在一个较大的视场内实现对静态目标和动态目标的高精度快速跟踪。     

论感知精度在产品设计中的应用方法

论述了感知精度的概念及其在设计中的至关重要性,并结合学习和设计实践的过程,分析了感知精度在产品设计中的应用方法,以及设计者在产品设计过程中如何提升自己的感知精度,进而分析了感知精度的培养对提高设计水平大有裨益,最后得出感知精度能够锻炼设计者正确把握产品的精度和美感,并对产品物化的实现和提高消费价值有着积极的作用。     

线性参数累积法处理时的精度估计

精度估计是线性参数处理中重要的一部分,而累积法是进行线性参数处理的一种新方法。为此在简述了普通累积法的概念和进行线性参数估计的原理之后,推导出了等精度测量时线性参数精度估计的计算过程和公式,并以测量铜棒长度和线性膨胀系数为例,对其进行了精度估计。结果表明,计算过程简便、公式正确。对于不等精度测量,只需要转化为等精度测量即可。     

P-S-N曲线统计精度分析

分析了反映P S N曲线统计精度的主要指标 ,提出了P S N曲线参数估计量的均方误差计算机模拟求法。通过实例说明 ,采用精度较高的P S N曲线统计方法 ,可以在保证相同精度的条件下 ,比其它统计方法减少试件用量。     

CCD细分技术用于刻线的自动瞄准

用面阵ＣＣＤ对刻线进行二维瞄准定位，具有精度高，速度快的优点，本文介绍了亚象素细分定位的原理，瞄准精度的测量方法，以及所能达到的精度。     

Investigation of the Optimum Trigger Level in Time Interval Measurement

Measuring the time interval (TI) with an accuracy in the picoseconds range requires having an accurate measurement system and minimizing the sources of errors contributed by the signal being measured. Trigger level timing error is one of the main sources of error that dramatically affects the measurement accuracy. In this article we study the effect of changing the trigger level on the TI measurement accuracy for sinusoidal signals, introduce a laboratory method for determining the optimum trigger level that leads to the highest measurement accuracy, and make a method validation.     

含损伤板的动载荷识别精度研究

为了深入研究动载荷识别问题,改善识别精度受测点信息和传感器布置数目限制的影响。首先采用逆问题正分析的方法,在时域正演法识别的理论基础上,研究结构损伤对载荷识别结果的影响,然后分析讨论测点位置、采样时间间隔对识别精度的影响。结果表明,在板结构有损伤的情况下,该方法能有效地识别出非损伤处的载荷且计算效率较高,但对于损伤处载荷的识别精度较低。另外,通过优化传感器的布置以及选择合适的采样时间间隔,可较大程度提高识别精度,为载荷识别的准确性提供参考。     

Optimization of Multi-Fidelity Computer Experiments via the EQIE Criterion

Computer experiments based on mathematical models are powerful tools for understanding physical processes. This article addresses the problem of kriging-based optimization for deterministic computer experiments with tunable accuracy. Our approach is to use multi-fidelity computer experiments with increasing accuracy levels and a nonstationary Gaussian process model. We propose an optimization scheme that sequentially adds new computer runs by following two criteria. The first criterion, called EQI, scores candidate inputs with given level of accuracy, and the second criterion, called EQIE, scores candidate combinations of inputs and accuracy. From simulation results and a real example using finite element analysis, our method outperforms the expected improvement (EI) criterion that works for single-accuracy experiments. Supplementary materials for this article are available online.     

白车身顶盖激光钎焊焊缝装配尺寸控制方法研究

目的研究白车身顶盖与侧围激光钎焊装配尺寸控制方法,提高顶盖侧围激光钎焊焊缝装配精度,降低激光焊缺陷率。方法顶盖与侧围焊接配合形面由传统的面贴合设计更改为线贴合,降低对车身焊接合拼精度的要求;顶盖与侧围模具结构上采用整体整形及压料镶块提升零件的尺寸精度,避免因镶块交接造成的翻边面缺陷而影响激光钎焊质量;顶盖与侧围的成形焊夹具设计成y向浮动以及在激光焊夹具上设计z向夹紧功能,来实现侧围与顶盖装配间隙的调整。结果实际应用表明,侧围与顶盖激光钎焊装配尺寸得到了有效控制,满足激光钎焊的要求。结论顶盖与侧围产品的设计优化、冲压模具工艺和结构的创新和优化以及焊装焊接夹具的柔性化适配功能,可以有效保证白车身顶盖钎焊搭接部位尺寸精度。