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平面参数三次样条曲线的优化光顺算法 总被引:1,自引:0,他引:1
给出了基于Kjellander和离散曲率的平面参数三次样条曲线的一种优化光顺算法.首先介绍了离散曲率和Kjellander的光顺法,进而给出了一个带有修改因子λ的目标函数,并通过求解得到λ值和光顺后的型值点,最后得到光顺后的曲线.此法使曲线的曲率变化均匀,使光顺后的曲线与原曲线的偏差小,并且算法简单易行,计算量较小. 相似文献
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在工业设计和反求工程中,曲线是形状设计和数据拟合的重要对象。曲线的光顺性对最终产品的外观质量有着直接影响。文章利用文献[1]构造出带有参数调配函数的模型,用其生成三次C-Bézier曲线。在能量法的基础上,研究了控制参数α对这种新曲线形态的影响,通过调整α和控制顶点使得曲线的能量最小,得到最优的光顺逼近曲线。通过最小二乘法和非线性泛函的极小值优化计算,对平面数据点进行光顺逼近,达到光顺的目的。该算法既可以对曲线进行全局光顺又可以进行局部光顺。最后给出了由数据拟合的C-Bézier曲线光顺的实例。 相似文献
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系统利用计算机图形平台来模拟船体数学放样和手工光顺,用Beta样条和B样条两种技术来拟合型线,实现船体水下部分型线的交互设计。系统可自动读取型值表中的数据,直观方便地进行各个站点型值点的参数化交互设计,实时记录和保存修改结果,自动更新后台数据文件型值表,并自动绘出水下部分船体型线。系统在绘图的同时自动生成曲线插值的数据文本文件和图形的DXF文件,使图形的输出可以方便与AutoCAD接口。 相似文献
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B-样条曲面的局部形状改进算法 总被引:2,自引:0,他引:2
提出了一种双三次B-样条曲面局部形状改进算法。首先根据节点处三阶不连续性的近似局部光顺准则,选择曲面待光顺的节点;然后利用约束的最小二乘逼近法修改相应的局部控制顶点网,从而降低曲面局部的三阶不连续性,使局部形状得到改进。在详细描述算法原理后,给出了算法的实现步骤。 相似文献
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基于粒子群优化算法的结构模型修改 总被引:12,自引:0,他引:12
结构模型修改已经演化为一个多学科的研究课题.在最优化框架内,应用了国际上最近提出的粒子群优化算法,该算法具有全局搜索能力并且不需要目标函数的解析表达式。对于一实际钢结构,利用部分和全部测量得到的模态数据进行了模型修改的实验研究.并与基于灵敏度分析、神经网络和遗传算法的模型修改方法进行了对比.以修改后模型计算出的模态数据与实验测得的模态数据的相似度来衡量模型修改的准确性。结果表明,在多数情况下,所提出的模型修改方法得到了最好的修改结果,因此,应用粒子群优化算法进行结构模型修改是可行的。 相似文献
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HUANG Dong-zhao ZHU Zhi-hong ZHOU Hui-cheng SHI Han-min National NC System Engineering Research Center School of Mechanical S cience & Engineering Huazhong University of Science Technology Wuhan P.R.China 《国际设备工程与管理》2008,13(2)
This paper presents a novel curve modeling method based on controlling rules of the shaping technique.The method describes the curve based on steplength and turning angle,and the characteristics of the curve near a point.Then it introduces the process to extract ″growing-rules″ for 2D and 3D curves described by familiar analytical expressions and curvature-torsion expressions.Examples of self-growing modeling for familiar analytical curves are presented.New curves are obtained by designing the grow-rules;co... 相似文献
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Quiroga JA Servin M Cuevas F 《Journal of the Optical Society of America. A, Optics, image science, and vision》2002,19(8):1524-1531
The fringe orientation angle provides useful information for many fringe-pattern-processing techniques. From a single normalized fringe pattern (background suppressed and modulation normalized), the fringe orientation angle can be obtained by computing the irradiance gradient and performing a further arctangent computation. Because of the 180 degrees ambiguity of the fringe direction, the orientation angle computed from the gradient of a single fringe pattern can be determined only modulo pi. Recently, several studies have shown that a reliable determination of the fringe orientation angle modulo 2pi is a key point for a robust demodulation of the phase from a single fringe pattern. We present an algorithm for the computation of the modulo 2pi fringe orientation angle by unwrapping the orientation angle obtained from the gradient computation with a regularized phase tracking method. Simulated as well as experimental results are presented. 相似文献
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Parametric curves such as Bézier and B-splines, originally developed for the design of automobile bodies, are now also used in image processing and computer vision. For example, reconstructing an object shape in an image, including different translations, scales, and orientations, can be performed using these parametric curves. For this, Bézier and B-spline curves can be generated using a point set that belongs to the outer boundary of the object. The resulting object shape can be used in computer vision fields, such as searching and segmentation methods and training machine learning algorithms. The prerequisite for reconstructing the shape with parametric curves is to obtain sequentially the points in the point set. In this study, a novel algorithm has been developed that sequentially obtains the pixel locations constituting the outer boundary of the object. The proposed algorithm, unlike the methods in the literature, is implemented using a filter containing weights and an outer circle surrounding the object. In a binary format image, the starting point of the tracing is determined using the outer circle, and the next tracing movement and the pixel to be labeled as the boundary point is found by the filter weights. Then, control points that define the curve shape are selected by reducing the number of sequential points. Thus, the Bézier and B-spline curve equations describing the shape are obtained using these points. In addition, different translations, scales, and rotations of the object shape are easily provided by changing the positions of the control points. It has also been shown that the missing part of the object can be completed thanks to the parametric curves. 相似文献
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提出一种圆锥体组件加工信息快速高精度检测与生成的方法。首先,使用Delaunay网格划分法对圆锥体组件点云数据进行处理,得到其三角网格模型;其次,利用最小二乘拟合方法计算圆锥体组件点云数据各空间点最近邻域平面及其法向量,并构建空间点与法向量之间的映射关系,再根据该映射关系提取锥角;最后,通过对圆锥体组件点云数据的整体形貌分析提取锥高,利用锥角与锥高之间的关系计算出底面圆半径,通过计算的方式快速得到圆锥体组件的高精度加工信息。实验结果表明:该方法与几何测量方法相比,圆锥体组件的锥角θ、锥高h和底面圆半径r的误差分别降低了77.64%、70.53%和73.48%,时间减少了81.74%,能够实现圆锥体组件快速高精度加工信息检测与生成。 相似文献
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提出了一种新的算法用于实现VB语言对CATIA曲面法向量和坐标转换的二次开发。该算法基于方向余弦法和新坐标系轴上3个特殊点实现转换,巧妙地解决了CATIA提供给VB语言二次开发中用于测量角度的函数的不稳定性问题,规避了直接采用测量角度进行的一系列计算(如用角度来求方向余弦值),为CMM数据源的正确性提供了有力保证。基于该研究成果,现已利用VB语言成功开发出“CMM测量点采集辅助软件”,并取得了相关软件著作权。 相似文献