共查询到19条相似文献,搜索用时 203 毫秒
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将欧氏空间中两非均匀B样条曲线间G1连续条件拓展到曲面空间,提出一种构造网格曲面上两相离曲线光滑过渡曲线的方法.网格曲面上的曲线采用测地B样条表示,具有与欧氏空间中传统B样条相一致的明确数学模型.基于三角网格模型的拓扑邻接关系,提出一种网格曲面上测地线的延长线离散逼近算法,以此为基础,建立两测地B样条曲线间G1连续条件,将边界连续条件转化为控制顶点的位置约束,从而构建两曲线间的光滑过渡曲线.试验结果表明,所提方法健壮、高效,不依赖于参数化和投影技术,即使对于具有尖锐特征的曲面亦有很强的适应性. 相似文献
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《计算机集成制造系统》2015,(2)
为了用明确的数学形式表示三角曲面网格中的基曲线和等距曲线,提出一种流形网格曲面上曲线等距线的计算方法,网格曲面上的曲线用测地B样条表示,具有明确的数学表示形式。采用节点插入技术将源曲线分解为分段Bezier曲线,并进行线性化逼近,通过曲线细分策略使其误差控制在给定的容差ε1内;提出一种给定源点和初始方向的离散化测地线构造算法,以该算法为基础,按照顶点等距方法获得源曲线的初始等距线;以初始等距线作为控制多边形并适当插入一些顶点,构造满足给定容差ε2的G1连续分段Bezier曲线作为源曲线的等距线。等距曲线的整体逼近误差由ε1和ε2之和构成,因此可以实现误差的全局控制。针对曲面上曲线自交点计算工作量大的问题,提出先识别局部自交区域再求自交点的策略,减少了线段求交的计算量。实验结果表明,所提方法健壮、有效,能满足曲面上曲线的等距计算要求。 相似文献
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针对环切刀轨中存在的拐角及残区问题,提出采用三段式Clothiod曲线光滑拼接的方法进行过渡优化。首先,借鉴骨架线提取的原理判断拐角残区并提取出残区步长;然后,在残区步长的基础上,选取过渡控制点和初始插入点作为曲线过渡的特征点;最后,在特征点的约束下,将曲线和直线进行过渡连接,并保证过渡曲线的C2阶连续。仿真加工测试结果表明,该方法能有效切除环切拐角残余并实现刀轨的平稳过渡,同时能很好地缩短加工时间和提高整体的加工质量。 相似文献
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圆柱体相贯线上的圆角表示法是CAD和计算机辅助设计中众所周知的难题。所有的CAD/CAM软件中都没有这一功能。本文借助"滚球法",以二次圆弧曲线的NURBS生成原理为基础,利用NURBS方法可精确表示圆及圆弧的特点,给出了构造圆柱体相贯线上圆角过渡曲面的实用算法,同时给出了过渡曲面的NURBS表示。 相似文献
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针对注塑机双曲肘内翻式合模装置十字头连杆过渡结构应力集中现象和出现断裂问题,以双曲肘内翻式合模装置为研究对象进行分析,研究并提出了一种采用曲面过渡的设计方法。对合模装置十字头连杆进行了动力学、静力学仿真分析表明过渡处应力集中明显,超出安全系数1.5的许用应力值,是导致十字头连杆断裂的原因。根据圆过渡设计方法中的半径和出现最大应力值位置的关系,提出了一种过渡曲线方程,以该曲线构造过渡曲面,降低过渡结构最大应力值。通过与圆过渡设计方法和楔形面过渡设计方法对比,研究结果表明,该方法对降低过渡处最大应力值具有有效性。 相似文献
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基于截面轮廓的NURBS曲面重建 总被引:2,自引:0,他引:2
提出了一种基于变截面轮廓线族重建NURBS曲面的方法。用自动跟踪法反求出轮廓线组的脊线,并用脊线自动调整各轮廓线的起始点位置。然后插值各个轮廓线,构造封闭的样条曲线,以特征点处的节点为分段点实现多条样条曲线的分段相容,并蒙皮构造封闭的B样条曲面。对于有特征点的轮廓线,通过设置特征点的重数及在曲线构造和曲面蒙皮中的相应处理,可以在曲面上保留轮廓线中的特征。 相似文献
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反求工程中过渡曲面特征提取算法研究 总被引:18,自引:1,他引:18
针对反求工程中常见的过渡曲面特征,提出了一种过渡曲面特征的提取算法。该算法包括数据分块和过渡曲面参数提取两部分,在数据分块算法中,通过数据精简,曲率估算和曲率比较等步骤,将过渡区域的数据点从原努点云数据中分离出来,在过渡曲面参数提取算法中,通过圆柱拟合和过渡区域跟踪算法,计算出一系列过渡曲面的截面线,该算法和已有的过渡曲面特征提取算法相比,无需人工交互,而且适用于等半径过渡曲面特征和变半径过渡曲面特征。 相似文献
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Rafael BenÍtez Susana Moreno‐flores Vicente J. BolÓs JosÉ Luis Toca‐Herrera 《Microscopy research and technique》2013,76(8):870-876
A new method for estimating the contact point in AFM force curves, based on a local regression algorithm, is presented. The main advantage of this method is that can be easily implemented as a computer algorithm and used for a fully automatic detection of the contact points in the approach force curves on living cells. The estimated contact points have been compared to those obtained by other published methods, which were applied either for materials with an elastic response to indentation forces or for experiments at high loading rates. We have found that the differences in the values of the contact points estimated with three different methods were not statistically significant and thus the algorithm is reliable. Also, we test the convenience of the algorithm for batch‐processing by computing the contact points of a force curve map of 625 (25×25) curves. Microsc. Res. Tech. 76:870–876, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
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基于B样条曲面的点云孔洞拟合填充 总被引:1,自引:0,他引:1
为了后续曲面重构的需要,针对有孔洞的点云数据,提出了一种孔洞拟合填充的自适应方法。由于孔洞与其周围离散点有一定的连续性,该算法首先从孔洞周围已有的点云数据中选取离散点,用新的参数化方法对得到的离散点参数化后,用最小二乘法进行自适应曲面拟合,对得到的拟合曲面通过迭代法逐步逼近优化,考虑曲率变化的影响在曲面上取点,实现了孔洞光滑填充。实例表明,改进的参数化方法使算法的复杂度减低,进一步迭代优化提高了曲面拟合精度,在面上取点时考虑了曲率变化,因此该方法可以应用于具有复杂曲面形状的点云中的孔洞填充。 相似文献
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Qiuzhi Song Zhengdong Huang Liping Chen Yifang Zhong 《The International Journal of Advanced Manufacturing Technology》2004,23(7-8):475-488
A method of generating
n-sided (n=3, 5, 6) G2 blending surfaces (except that the 3-sided blending surface is C0 continuous at the three vertexes and the 5-sided blending surface is C0
continuous at a vertex) is presented in this paper. When this method is used to generate n-sided (n=3, 5, 6) G2 blending surfaces between the base surfaces, the base surfaces are expressed as n-sided (n=3, 5, 6) by reparameterising the base surfaces; then the
n-sided (n=3, 5, 6) G2 blending surfaces are convex combinations of the base surfaces expressed as n-sided (n=3, 5, 6) surfaces. When the contact curves are arbitrary curves in the base surfaces, the regions near the contact curves in the base surfaces are reparameterised and expressed as n-sided (n=3, 5, 6) surfaces; then the n-sided (n=3, 5, 6) G2 blending surfaces are convex combinations of the reparameterised local base surfaces expressed as n-sided (n=3, 5, 6) surface styles. The shape of the n-sided (n=3, 5, 6) blending surfaces can be adjusted by changing the size of the reparameterised local base surfaces and the combination weights. An example of a 5-sided surface generated between an aerofoil, the body and the fringe surface of a missile is given. 相似文献
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WangXiaoping ZhangWeizhong ZhangLiyan ZhouRurong 《机械工程学报(英文版)》2005,18(2):192-195
The problem of constructing curve on parametric surface (or surface that can be parameterized) such that it interpolates a sequence of points with prescribed tangent direction and curvature vector (or geodesic curvature) at every point and the issue of curve blending on this kind of surface are researched. The mapping and tangent mapping from the surface to its parametric plane are introduced and thus several conclusions with differential geometry are deduced. Based on those conclusions, the problem of interpolating (or blending) curve on a parametric surface is converted to a similar one on its parametric plane. The final solution curve of either interpolation or blending issue is explicit and can still be expressed by parametric form. And so, unlike existing methods, the presented method needs not to use any surface/surface intersection algorithms, usually a troublesome process, for displaying such interpolation curve. Experiment results show the presented methods are feasible and applicable to CAD/CAM and computer graphics. 相似文献
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Wang Xiaoping Zhang Weizhong Zhang Liyan Zhou Rurong Research Center of CAD/CAM Engineering Nanjing University of Aeronautics Astronautics Nanjing China 《机械工程学报(英文版)》2005,(2)
The problem of constructing curve on parametric surface (or surface that can be parameterized) such that it interpolates a sequence of points with prescribed tangent direction and curvature vector (or geodesic curvature) at every point and the issue of curve blending on this kind of surface are researched. The mapping and tangent mapping from the surface to its parametric plane are introduced and thus several conclusions with differential geometry are deduced. Based on those conclusions, the problem of interpolating (or blending) curve on a parametric surface is converted to a similar one on its parametric plane. The final solution curve of either interpolation or blending issue is explicit and can still be expressed by parametric form. And so, unlike existing methods, the presented method needs not to use any surface/ surface intersection algorithms, usually a troublesome process, for displaying such interpolation curve. Experiment results show the presented methods are feasible and applicable to CAD/CA 相似文献
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针对单值散乱点云曲面刀具路径规划问题,提出了一种基于最小二乘支持向量机的计算方法。在计算过程中,将点云数据向平面投影,得到二维点集。应用网格划分和边界网格内测量点高斯映射技术,提取平面区域内的边界特征点。用边界特征点定义点云曲面的实际加工区域,在此区域内规划平行等间距刀具路径。应用最小二乘支持向量机拟合点云数据,求得被加工曲面的连续表达模型,经此模型将二维刀具路径数据向三维空间映射,求出刀触点数据。将刀触点经法向偏置计算,求得刀位点。实例验证证明,该方法能较好地解决信息不完备散乱点云曲面刀具路径生成问题。 相似文献