共查询到18条相似文献,搜索用时 750 毫秒
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结合球度误差的几何定义,提出了一种基于几何搜索的球度误差最小区域评价方法。首先,以初始参考点为基准,布置一定边长的正方体,依次以正方体的每个顶点为假定理想球心计算所有测量点的半径值,通过比较判断,调整正方体的位置及边长,最终获得包容所有测点的最小区域,实现球度的最小区域评定。在终止搜索条件为0.00001mm时,对同一组测量数据,该算法的结果比最小二乘法减小了0.6μm,并与解析法、遗传算法的结果相一致。计算过程及结果表明,该算法不仅能准确地得到最小区域解,而且计算结果有良好的稳定性。 相似文献
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通过直接降低同心球半径之差的方法,以达到逐步降低球度误差计算值为目的,寻求球心的移动方向和移动步长,不断把半径之差减小,从而令球度误差的计算向“最小区域球”收敛,以求得符合“最小条件原则”评定标准下的球度误差。 相似文献
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文章指出球度是一个纯的形状误差,整球只有形状误差和参数误差,半球才有位置误差。平面可以用平面度或球度进行评定,但其结果必然不一样。文章介绍了球面的各种测量方法,并指出目前对整球还不能作全面测量。文章介绍了最小二乘法、最小区域法、最小外接球法及最大内接球法四种评定方法及其计算公式,并用实例予以说明,并指出评定的球心可能不唯一,产生不唯一的条件和原因,以及如何找出球心的集合空间。介绍了编程的原理框图。 相似文献
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圆度误差的最小二乘法、最小包容区域法和最优函数法评定精度之比较 总被引:5,自引:0,他引:5
目的在于寻找符合最小条件的圆度误差评定方法。首先详细介绍圆度误差评定的最小二乘法、最小包容区域法和最优函数法的算法模型与实现方法;然后,在三坐标测量机上对被测圆进行采样点坐标数据提取,分别用最小二乘法、最小包容区域法和最优函数法对给定圆进行误差评定。结果表明,最小包容区域法评定精度最高,最优函数法评定精度次之,最小二乘法评定精度较低。 相似文献
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文章指出球度是一个纯的形状误差,整球只有形状误差和参数误差,半球才有位置误差。平面可以用平面度或球度进行评定,但其结果必然不一样。文章介绍了球面的各种测量方法,并指出目前对整球还不能作全面测量。文章介绍了最小二乘法、最小区域法、最小外接球法及最大内接球法四种评定方法及其计算公式,并用实例予以说明,并指出评定的球心可能不唯一,产生不唯一的条件和原因,以及如何找出球心的集合空间。介绍了编程的原理框图。文章指出“凸理论”位置准则的适用性有一定局限性,如何完善有待学者进一步探讨。 相似文献
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本文在机器坐标系中建立球度误差最小二乘法评定和包容评定的数学模型.并采用精确、快速的算法求解。计算实例表明本文方法直接、快速、有效,非常适用于三坐标测量机的球度误差评定。 相似文献
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为了实现对球形工件球度误差的精确评定,在4种球度误差评定数学模型的基础上,对文献提供的两组数据采用一种动态改变权重的粒子群算法(PSO)进行计算,这种算法在优化迭代过程中使惯性权重值随粒子的位置和目标函数的性质而更新。与基本PSO算法、最小二乘法、遗传算法和一种改进的PSO算法进行了比较。实验结果显示,相比其他方法,在最小包容区域法模型下使用动态改变权重粒子群算法得到的球度误差最小,第1组数据只需迭代30代左右,约50ms即可收敛,第2组数据收敛也很迅速,且多次实验显示其稳定性很高。因此,所提算法可精确快速地评价球度误差。 相似文献
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Several methods for the evaluation of sphericity error exist. The Minimum Radial Separation (MRS) spheres method is a method that has been studied by several researchers. In the MRS criterion, two concentric spheres at minimum radial separation must be found such that they contain all points on the actual spherical surface. The existing procedures for finding MRS spheres are either too complex and time consuming or do not provide an optimal solution to the sphericity error evaluation problem. In this paper, mathematical optimization concepts are utilized to develop a theory and an algorithm for the evaluation of sphericity error based on MRS criterion. Results indicate that the algorithm is fast and accurate in providing optimal solution to the sphericity error evaluation problem. 相似文献
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Assessment of methods for computing the closest point projection,penetration, and gap functions in contact searching problems 下载免费PDF全文
Ján Kopačka Dušan Gabriel Jiří Plešek Miran Ulbin 《International journal for numerical methods in engineering》2016,105(11):803-833
In computational contact mechanics problems, local searching requires calculation of the closest point projection of a contactor point onto a given target segment. It is generally supposed that the contact boundary is locally described by a convex region. However, because this assumption is not valid for a general curved segment of a three‐dimensional quadratic serendipity element, an iterative numerical procedure may not converge to the nearest local minimum. To this end, several unconstrained optimization methods are tested: the Newton–Raphson method, the least square projection, the sphere and torus approximation method, the steepest descent method, the Broyden method, the Broyden–Fletcher–Goldfarb–Shanno method, and the simplex method. The effectiveness and robustness of these methods are tested by means of a proposed benchmark problem. It is concluded that the Newton–Raphson method in conjunction with the simplex method significantly increases the robustness of the local contact search procedure of pure penalty contact methods, whereas the torus approximation method can be recommended for contact searching algorithms, which employ the Lagrange method or the augmented Lagrangian method. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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为了对ICF靶丸的表面形貌及球度误差进行高精度测量,开发了一台五轴坐标测量机,并采用锥光全息技术的激光测头实现对靶丸表面的高精度、非接触检测。首先,根据靶丸表面的结构特点,改进了基于最小二乘的球度误差评价算法;然后,介绍了作为实验平台的五轴坐标测量机的整体配置,推导了该坐标测量机的测量数学模型,该坐标测量机可实现在多个姿态下对靶丸的非接触取点测量;最后,在相同条件下,进行了5次实验测量,其结果表明:靶丸球度误差测量的均值为0.0021 mm,标准差为2.07 x10^-4 mm。该检测方法可以满足对靶丸表面形貌及球度误差高精度、高稳定性的测量要求。 相似文献
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High accuracy of locating the sphere center imaging points is crucial for the vision measurement system. This paper investigates the effect of projection projective model on extraction of the sphere center, upon which the sub-pixel edge-location algorithm based on the sphere projection model is proposed. The sphere center projection model is established by analysing the process of sphere imaging, and the sub-pixel edge-location algorithm consisted of the novel edge model and the improved Zernike moment computing is studied. The novel edge model based on the Erf (error function) is adopted for modelling the practical edge part, which obtains the edge distribution points with high precision. Then a closed-form solution of edge locating error compensation is calculated based on Zernike moments. Finally, the proposed method is verified via simulations and experiments. The relevant results show that the proposed method can accurately locate the sphere center imaging point, which further improves the precision and robustness of the vision measurement system. 相似文献
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