基于Matlab评定圆柱度误差

针对圆柱度误差评定的特点,建立了用Matlab实现圆柱度误差最小区域法、最小外接圆柱法和最大内接圆柱法评定时目标函数数学模型的计算方法。通过不同评价方法对圆柱度误差在不同初始值下进行多次评定,证明该方法都能收敛到全局最优解,而且计算结果稳定。该算法可以推广应用到其他形状误差评定中。     

圆柱度误差评定的最小面积准则及其应用

本文提出圆柱面形状误差评定的一个新准则－－“最小面积准则”，以此建立空间一般位置圆柱度误差评定的数学模型，用有效集法方便地求得理想圆柱面的描述参 和圆柱度误差。文章从理论上证明了在小误差条件下，最小面积准则等价于ＩＳＯ关于形状误差评定的最小区域准则，因而本文方法为圆柱度平定实现最小条件提供了一个有效方法。     

圆度误差评定的曲率法研究

提出了基于曲率的圆度误差评定方法.从曲率的定义出发,推导出了用最大内接圆或最小外接圆评定圆度误差时筛选点的条件:用最大内接圆评定时,筛选掉曲率半径最小的点;用最小外接圆评定时,筛选掉曲率半径最大的点.根据这一条件,可以得到满足圆度误差评定原则的3个特征点,从而确定圆度误差.筛选点时,用最小二乘圆把测量点分成内点集合和外点集合,最大内接圆从内点集合中筛选,最小外接圆从外点集合中筛选,这样就可大大减少了计算量.经过实例验证,表明该方法的正确性和可行性.     

进化策略实现圆度误差的统一评定研究

圆度误差的评定有最小区域法、最小外接圆法、最大内接圆法和最小二乘法4种方法,文中提出了将进化策略用于上述多种圆度误差的统一评定.该算法基于实数编码,采用(μ λ)选择策略和高斯变异算子,即父代种群参与竞争,算法简单、鲁棒性强,优化效率高.同时建立了进化策略评定上述圆度误差时目标函数的数学模型.最后,通过不同评价方法对圆度误差进行评定,结果证明该方法不仅能快速收敛到全局最优解,而且计算结果的稳定性好,易于在工程计量中推广使用.     

最小条件下零件圆柱度误差数学模型及其计量实现

依据ISO及国家标准规定的形位误差最小条件评定原则,针对圆柱度误差评定的特点,建立了基于柱坐标系下圆柱度误差的最小区域法评定数学模型.结合数学规划模型的特点,并根据线性规划的原理和求解方法,提出了适合模型求解的改进单纯形算法.通过实例给出符合新一代GPS标准规范的圆柱度误差计量方法,从而为零件圆柱度的精确测量及评定提供了理论和应用基础,对提高零件几何误差的数字化计量技术具有一定的促进作用.     

基于多种群遗传算法的圆柱度误差评定

分析了最小区域条件下求解圆柱度误差的研究现状,针对现有的圆柱度误差评定方法不能适用于任意位置圆柱度误差计算的情况,提出了一种求解多变量、非线性圆柱度误差的实数编码多种群遗传算法,阐述了算法的基本思想和步骤,建立了基于最小区域条件的优化目标函数。实验结果表明该方法有效地提高了全局搜索能力,进化过程稳定,能够快速获得多变量非线性问题的最优解,适用于各种位置情况的圆柱度误差评定。     

圆柱度误差及其评定方法综述

针对圆柱度误差评定的特点，建立了四种圆柱度误差的数学模型，并将已有的圆柱度误差评定方法进行归纳分类，总结了各种方法的评定特点，同时阐述了圆柱度误差评定的最新研究成果即基于改进遗传算法的圆柱度误差评定，该成果可以推广应用到其它形状误差的评定。     

基于MATLAB的圆度评定方法

本文利用MATLAB优化工具箱,采用最小区域圆法、最小二乘圆法、最小外接圆法和最大内接圆法进行圆度的评定。并给出了参考程序和运行结果。     

基于极坐标测量的圆度误差评定算法

提出一种利用极坐标测量数据求解圆度误差的网格搜索算法,其原理是在最小二乘圆心周围按一定规则布置一系列的极坐标网格点,依次以各网格点为理想圆心计算所有测点的半径值,通过比较这些半径值,实现最小区域法、最小外接圆法和最大内接圆法的圆度误差精确评定。详细叙述了算法求解圆度误差的过程和步骤,给出了数学计算公式及程序流程图。试验结果表明,该算法可有效、正确地评定圆度误差。     

圆柱度误差评定的最小面积准则及其应用

本文提出圆柱面形状误差评定的一个新准则──“最小面积准则”，以此建立空间一般位置圆柱度误差评定的数学模型，用有较集法方便地求得理想圆柱面的描述参数和圆柱度误差。文章从理论上证明了在小误差条件下，最小面积准则等价于ＩＳＯ关于形状误差评定的最小区域准则，因而本文方法为圆柱度误差评定实现最小条件提供了一个有效方法。     

4种圆度误差评定方法分析

介绍了圆度误差评定的4种方法:最小区域法、最小二乘法、最小外接圆法和最大内切圆法.研究了4种评定方法的判别准则,分别建立数学模型进行理论推导.在深入研究基础上,采用Visual C++编程加以实现算法.利用美国OGP公司研制的"flash2000"影像测量仪对光滑环规工件进行5次重复测量,应用4种算法分别计算结果,并进行结果比对.实验结果表明,4种方法都能较好地实现圆度误差评定,其中最小区域法圆度评定的准确性相对较高.     

Evaluation of cylindricity using combinatorics

Several numerical methods have been developed for finding the minimum zone of a cylinder. This paper presents a combinatorial method termed the Minimum Shell for cylindricity evaluation. For a given set of measured data points, the method efficiently searches for the six points that determine the minimum zone of cylindricity. This method is self-contained, without the requirement of mathematical programming software support, and is equal to or superior to other methods of evaluating cylindricity in terms of accuracy, efficiency, and simplicity. Computational results are given.     

三维实体结构NURBS等几何分析

等几何分析是近年来在有限元法基础上发展起来的一种新的数值方法,它消除了有限元的几何误差,具有高阶连续性。该文研究了三维结构等几何分析中NURBS几何体的表示方式及载荷、约束的施加方法,分别从计算精度和仿真效率两个方面对比了等几何分析的计算结果与有限元法一阶单元和二阶单元的计算结果,展示了等几何分析相对于标准有限元法的优势,并以厚壁圆筒模型算例验证了等几何分析的实用性。将NURBS单元应用于几何形状精度要求高的齿轮和变截面圆筒,数值结果表明三维NURBS等几何分析方法在复杂三维结构的仿真计算中具有较好的灵活性和适用性,可得到连续的应力场,有望在工程中得到广泛应用。     

计算几何在测试计量技术中的应用-求解最小外接圆

提供一种在机械科学中评定最小外接圆柱形状误差的高效、高精度算法。该算法的核心是提出了一种删除对求解最小外接圆不会起任何作用的无关样本点的有效方法。交替运用计算几何中的最远点Voronoi图的性质和统计分析方法撮小二乘法原理,可使最后参与求解最小外接圆的样本点数减至少量几个,相应算法的运算时间比以往的最优化快10倍以上。     

Kernel Entropy Based Extended Kalman Filter for GPS Navigation Processing

This paper investigates the kernel entropy based extended Kalman filter (EKF) as the navigation processor for the Global Navigation Satellite Systems (GNSS), such as the Global Positioning System (GPS). The algorithm is effective for dealing with non-Gaussian errors or heavy-tailed (or impulsive) interference errors, such as the multipath. The kernel minimum error entropy (MEE) and maximum correntropy criterion (MCC) based filtering for satellite navigation system is involved for dealing with non-Gaussian errors or heavy-tailed interference errors or outliers of the GPS. The standard EKF method is derived based on minimization of mean square error (MSE) and is optimal only under Gaussian assumption in case the system models are precisely established. The GPS navigation algorithm based on kernel entropy related principles, including the MEE criterion and the MCC will be performed, which is utilized not only for the time-varying adaptation but the outlier type of interference errors. The kernel entropy based design is a new approach using information from higher-order signal statistics. In information theoretic learning (ITL), the entropy principle based measure uses information from higher-order signal statistics and captures more statistical information as compared to MSE. To improve the performance under non-Gaussian environments, the proposed filter which adopts the MEE/MCC as the optimization criterion instead of using the minimum mean square error (MMSE) is utilized for mitigation of the heavy-tailed type of multipath errors. Performance assessment will be carried out to show the effectiveness of the proposed approach for positioning improvement in GPS navigation processing.     

可见光成像系统MRC测试技术的研究

通过分析国外现行的实现最小可分辨对比度(MRC)测量的方法,提出了一种采用两个重叠积分球对测试图案正反两面均匀照明,获取可调对比度的实现MRC测量的新方法,研制了相应的测量MRC仪器。采用新的方法测试图案的目标亮度和背景亮度可以单独调节,而且还能得到精确的控制。测试结果表明,该仪器测量亮度的误差在±0.3 cd/m2的范围内,MRC的扩展不确定度不超过3%,适合各种试验现场对可见光成像系统成像质量的在线评价。     

微分进化算法在圆度误差评定中的应用

为了精确快速计算圆度误差,提出了基于微分进化智能优化算法的最小区域圆度误差评定方法。介绍了微分进化算法的基本原理及种群初始化、变异、交叉、选择实现步骤,建立了该算法求解最小区域圆度误差的数学模型。为验证算法的有效性,进行了大量实验并与多种算法进行对比,证实了方法的评定结果不仅小于最小二乘法及标准遗传算法评定结果,精度高,而且计算结果稳定,运算速度快。实验表明:微分进化算法用于最小区域圆度误差评定有较强的自适应能力、快速全局收敛性和高稳定性,适于对高精度圆度误差的快速评定。     

An analytical solution for the diffraction problem of a submerged vertical cylinder considering bottom-mounted barrier effect

Using the methods of variable separation and eigenfunction expansion for velocity potentials, an analytical expression for the composite structure of a submerged cylinder over a coaxial, bottom-mounted cylinder in finite depth is developed. This model is also applicable for the isolated submerged truncated cylinder by careful choice of bottom cylinder height. The exciting forces on the submerged cylinder obtained by the proposed analytical solution and the boundary element method (BEM) agree well with each other, which shows good reliability of the analytical expression. Based on the proposed model, the effects of wave force on submerged cylinder owing to the existence of topographical obstacles of different sizes are investigated. The results show that various geometrical parameters of the bottom cylinder alter wave force on the upper cylinder significantly. Considering the impact of barrier, horizontal wave force and vertical wave force on submerged cylinder arrive there are several peaks at different frequencies, while the isolated cylinder always reaches the peak at a certain frequency. The peak value of wave forces may increase or decrease, but that of overturning moment has a maximum value of two to four times amplitude.     

Optimizing dimensional accuracy of titanium alloy features produced by wire electrical discharge machining

This study investigates geometrical errors such as cylindricity, circularity and diametral errors of a feature (a hole) produced from wire electrical discharge machining of Ti6Al4V alloy where tension in wire, pulse on time, and flushing pressure are varied. Pareto analysis of variance (ANOVA), Taguchi design of experiment (DoE), and traditional analysis estimate the influence of variables on errors of holes. It was noted that flushing pressure is the most significant factor with individual contributions of 31.02%, 49.5% and 37.84% to circularity, cylindricity, and diametral errors, respectively. The circularity error of holes decreases as the flushing pressure and tension in wire rise, but decreases with the rise of pulse on time. The cylindricity error decreased with the increase of wire tension, flushing pressure and pulse on time. The absolute diametral error reduced as the pulse on time and tension in wire raised, but it raised with the rise of pulse on time. All these trends are associated with the influence of tension in wire on the flexibility of wire, the dependence of heat generation and dissipation on pulse on time, and ability of the flushing pressure to control the cooling, as well as debris removal from the machining zone.