共查询到20条相似文献,搜索用时 78 毫秒
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针对汽车A—class特征曲线高精度、高光顺性的基本要求,提出了基于控制顶点规范的Bezier曲面迭代微调方法,用曲面反算变换为NURBS曲面,经过基于最小弯曲能曲面修改以后,对进行外形优化。该法核心是控制顶点的微调计算和基于最小弯曲能曲面修改,实现对空间型值点的光顺拟合,实现迭代拟合过程的快速收敛,同时实现了曲面微调和曲面修改的自动化,使基于逆向工程得到的复杂曲面不仅满足精度要求,更可以进行美学设计。结合某汽车的A级曲面的点云数据实例,应用迭代微调有效地提高了生成CAD数据的效率和准确性。 相似文献
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真实齿面的数字化重建是虚拟仿真与测量的重要基础,提出了基于几何线特征的渐开线齿轮齿面的数字化曲面构造方法,根据渐开线齿轮齿面的渐开线、螺旋线和接触线三条特征线之间的相交关系划分齿面网格点,分别构造出三角面片组成的渐开螺旋面和双三次NURBS渐开线螺旋面。与三角面片集拟合得到的曲面进行面型拟合特征与拟合精度、特征线拟合特征与拟合精度的比对分析、特征线拟合精度与光顺性的分析计算。分析结果表明,两种数字化曲面具有明显不一样的特征,NURBS渐开螺旋面具有良好的精度和光顺性。 相似文献
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以某车后挡玻璃为研究对象,通过三坐标测量仪非接触式测量获取零件曲面的点云数据,并利用UG软件进行点云数据处理,且基于NURBS曲面重构理论进行零件曲面造型,同时对曲面进行光顺性检查。与传统的设计方法相比,提高了工作效率,缩短了新产品的研发周期。 相似文献
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利用自组织神经网络对原始曲面上的散乱数据点进行聚类,应用Unigraphics软件中的NURBS对聚类数据进行曲面重构,以获取原始曲面的CAD数字化模型.具体方法是利用Unigraphics软件设计原始曲面,在所设计的原始曲面上随机设置大量的散乱点数据,应用MATLAB中的神经网络工具箱中的自组织神经网络,对原始曲面上的散乱点数据进行聚类,获取样条曲线,再应用Unigraphics软件中的NURBS完成曲面重构. 相似文献
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散乱测量数据多层次B样条逼近曲面拟合算法 总被引:1,自引:0,他引:1
提出了一种散乱测量数据的快速曲面拟合方法。该方法使用由粗到精的有继承关系的控制网格分级,从而产生相应的拟合逼近函数,每一级都比前一级更加逼近测量数据。拟合曲面的精度与光顺性可通过适当选择分级层数得到控制。当控制网格分级足够多,密度足够大时,最后拟合结果是插值于测量数据的C2连续曲面。 相似文献
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童森林 《中国制造业信息化》2003,32(8):117-119
相邻曲面的光滑连接是曲面造型的关键技术,相接处使用倒圆角的设计方法已经不能适应时代发展对外观审美的要求。着重阐述了在使用Pro/Engineer2001软件设计零件时,如何合理选择边界类型、准确控制边界的相切条件,以实现相邻曲面的光滑连接,并归纳出几种常用的复杂异型曲面的应用场合和构建方案。 相似文献
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为解决高效、快速、精确地生成曲面等问题,将偏微分方程(PDE)应用到曲面生成中(PDE方法优越性在于可以通过相对较少的参数生成一张光滑的曲面)。研究了用解析伪谱法快速生成一张解析近似的四边PDE曲面片,与分离变量法不同的是,该方法生成曲面的近似解由3部分组成:一个特征函数;一个多项式的解,两者皆可精确地满足偏微分方程;附加一个剩余函数,以确保精确的满足边界条件;进行了相同边界条件下分离变量法与解析伪谱法生成曲面的试验。实验结果表明,解析伪谱法生成的PDE曲面较分离变量法精确度高,且更为光滑。 相似文献
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散射法表面粗糙度测量 总被引:6,自引:1,他引:5
介绍了标量和矢量两种散射理论,并用软X射线反射率对超光滑表面进行散射测量,同时应用这两种理论计算了超光滑表面粗度均方根值,从计算结果来看,两种理论所得结果与WYKO测量结果吻合较好。 相似文献
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基于临界约束的四轴数控加工刀轴优化方法 总被引:1,自引:0,他引:1
针对自由曲面四轴加工中复杂刀具运动导致的干涉和刀具运动不连续等现象,提出一种基于临界约束的刀轴优化方法。基于刀具与工件约束曲面之间的相对位置关系,利用曲线上的点搜索算法确定切触点处的临界刀轴矢量,并计算当前切触点刀轴摆动的可行域;以切削行内所有切触点的刀轴可行域为基础,建立当前切削行内无干涉且相邻刀轴变化最小的刀轴矢量优化模型,实现了自由曲面四轴加工无干涉刀轴矢量的光顺控制。整体叶盘四轴加工试验表明,利用此方法获得的刀轴矢量可以显著改善机床运动的连续性,并避免刀具干涉的产生,提高了加工质量。 相似文献
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M. Ya. Panovko 《Journal of Machinery Manufacture and Reliability》2010,39(6):539-548
We formulate and numerically solve the problem of elastohydrodynamic point contact, taking into account that one of the two
lubricated contact surfaces has a single irregularity in the form of a hump or hole. Three variants are considered: movement
of a surface with an irregularity relative to a fixed smooth surface (slip mode); movement of a surface with an irregularity
at a rate equal to the speed of a smooth surface (rolling mode); and movement of a smooth surface relative to a stationary
surface with an irregularity (pure slip mode). For the first two modes the problems is solved in a non-stationary statement
and for the third it is solved in a stationary statement. The features of influence of the kinematic conditions on distributions
of pressure and thickness of the lubricant slick in the contact zone are shown. A numerical algorithm for solving systems
of equations and inequalities was based on the Newton method and application of an implicit difference scheme for approximating
unsteady equations. 相似文献
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基于Pro/E环境介绍了酒瓶模具的设计方法,玻璃模具有其自身的特点,其中重要的是分型面的建立方法,本文以浏阳河酒瓶为例,提出一种建立酒瓶模具分型面的新方法,即平整和复制方法.该方法易于掌握,在酒瓶模具的设计中有广泛的应用前景. 相似文献
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Jiang H Campbell G Canas R 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2005,219(2):143-152
Reverse engineering technology was used to reconstruct the complex leaflet geometry of a commercial pericardial valve in our study. Results show that the three-dimensional computer-aided design model of the leaflet surface can be rendered by fitting the surface either to cloud points or by a group of B-splines fitted to a set of cloud points that had been obtained by the process of laser-scanning digitizing. However, an acceptable smooth surface is usually not guaranteed and additional manipulation is required. An alternative method is introduced in this paper, which involves the fitting of an equation to the leaflet geometry to create a smooth surface. The geometrical profile of a pericardial artificial heart valve was scanned using a laser digitizing system. The leaflet profile is represented as a set of cloud points. A quadric surface is fitted to a set of unique points, which were located on the set of cloud points. A mathematical equation is obtained by solving a least-squares fit. The geometry of the fitted leaflet surface has been proven to be closely represented by an elliptical hyperboloid. The quadratic equations of the leaflet curvatures, calculated along both the circumferential and the radial directions, resulted in simple hyperbolic curvatures. The advantages of using elliptical hyperboloid geometry for the leaflet surface are discussed and compared with other types of conicoid geometries. The concepts of parametric representation of the leaflet geometry and parametric design for leaflets are discussed. A smooth surface without inflection points and with an adjustable surface area suitable for a series of stent sizes with incremented diameters is created by this method of a single parametric design. Finally, a generic method to apply the geometry extraction and parametric representation to most pericardial heart valve prostheses was discussed. The application to valves with natural shape was introduced, challenges were identified, and a technical solution was proposed. 相似文献