共查询到20条相似文献,搜索用时 31 毫秒
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类螺旋特征测点数据的闭曲面建模方法研究 总被引:1,自引:0,他引:1
复杂曲面及海量点云测量数据的曲面建模已成为通用CAD/CAM软件的重要功能;然而,对于复杂的闭曲面建模方法,仍然存在许多技术上的难题,至今尚未能很好的解决,比如,基于海量的测量数据,如何进行闭曲面特征点识别,如何进行区域分割与处理,这一切都使得闭曲面建模过程中很难采用已经成熟的自由曲面建模技术和方法。通过研究异步仿形测量原理以及测量数据类型,针对鞋楦测量形成的空间螺旋线数据特征,提出一种闭曲面建模方法。该方法包括如下步骤:首先对测量点数据处理;并以特征螺旋线数据为基础对曲面进行三角分割;最后,以三角Bezier曲面为基础进行曲面构造,并将各曲面进行拼接、裁剪,形成完整的曲面。采用本文方法对鞋楦测量数据的建模实例说明,该方法能够有效地对具有空间螺旋线数据特征的闭曲面进行数据处理、曲面重构,提高了产品建模效率。 相似文献
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H. Woo T. K. Dey 《The International Journal of Advanced Manufacturing Technology》2006,30(3-4):261-272
In a manufacturing area, design changes for an original surface model are frequently required: for example, when the physical parts are modified or when the parts are partially manufactured from analogous shapes. In this case, an efficient surface updating method by locally adding scan data for the modified area is highly desirable. For this purpose, this paper presents a new procedure to update an initial model that is composed of combinatorial triangular facets based on a set of locally added point data. Nowadays, many people are using surface models that are represented by triangular facets in reverse engineering, since it is fast and easy to create the triangular meshes directly from large amounts of point data. The initial surface model is first created from the initial point set by tight cocone, which is a water-tight surface reconstructor; and then the point cloud data for the updates is locally added onto the initial model maintaining the same coordinate system. In order to update the initial model, the special region on the initial surface that needs to be updated is recognized through the detection of the overlapping area between the initial model and the boundary of the newly added point cloud. After that, the initial surface model is eventually updated to the final output by replacing the recognized region with the newly added point cloud. The proposed method has been implemented and tested with several examples. This algorithm will be practically useful to modify the surface model with physical part changes and free-form surface design. 相似文献
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基于三角曲面的逆向工程CAD建模方法 总被引:15,自引:1,他引:15
根据目前逆向工程CAD建模中存在的问题,提出一种基于三角Bezier曲面模型初始表达的跨平台产品逆向工程CAD建模策略,既能利用三角Bezier曲面的优势,又能有效地与通用CAD软件集成。对涉及产品逆向建模方案、数字化测量规划、实际建模过程和再创新设计等具体内容进行了详细阐述,并结合具体实例说明了该方法的可行性和有效性。 相似文献
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提出基于曲面透视投影和其内在几何的自由曲面造型方法。给出从曲面数据点的透视投影坐标、曲面法矢、切矢及主曲率,计算曲面三维数据点坐标的原理和过程。利用参数双三次样条曲面造型方法,从曲面三维数据点构造了自由曲面。给出的两个算例证明自由曲面初始数据法具有几何意义明显和便于控制的优点。 相似文献
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在反求工程中,从样件表面采集得到的通常是数量非常庞大的点云数据,严重影响了曲面重建算法的效率;另外,基于四边域曲面的重建算法通常要求型值点数据呈拓扑矩形排列,而采样得到的散乱点云通常不满足这一拓扑要求。文中提出了一种新的数据压缩技术路线,用于把海量散乱点云数据合理地压缩到四边域曲面重建所要求的数据量和拓扑形式。该方法的核心是B样条曲线的拟合和采样。为使采样点更好地反映原始模型的外形特征,给出了一种基于曲率的自由曲线自适应采样算法。应用实例表明本文提出的方法达到了预期的效果。 相似文献
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基于三角网格模型的B样条曲面重建技术得到深入发展,计算与显示重建后的B样条曲面与原始测量三角网格之间的误差对分析曲面重建品质有重要作用。一种较为实用的B样条曲面重建方法是对三角网格模型进行四边界区域划分后进行栅格式采样,再根据采样点进行B样条曲面拟合。针对这种重建方法,研究了一种建立三角网格顶点与四边界区域对应关系的算法,再用离散的方法计算点到对应曲面的距离误差,最后用线性插值方法实现误差彩色.云图的显示。 相似文献
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反求工程中基于边界扩展的三角网格构造 总被引:1,自引:0,他引:1
针对非接触式方式测量的大规模散乱点云数据建模,提出一种三角剖分算法,该算法适用于多张自由曲面片构成的曲面物体,尤其适用于含内孔的曲面对象。算法过程包括两个阶段:第一阶段,采用一种空间栅格装点法来进行初始点云数据精简,精简比率通过栅格小正方体单元尺寸控制;第二阶段,构造种子三角形,通过连接已剖分网格区域的边界边与最优扩展点采形成三角网格,从而向外延展,也可以时一个带有内孔的复杂自由曲面直接进行三角剖分,无需人工分区。实验结果表明该算法可以快速、有效地从三维数据点云建立几何模型。 相似文献
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Fengwei HUO Zhuji JIN Renke KANG Dongming GUO Chun YANG 《Frontiers of Mechanical Engineering in China》2008,3(3):325-331
The accurate evaluation of grinding wheel surface topography, which is necessary for the investigation of the grinding principle,
optimism, modeling, and simulation of a grinding process, significantly depends on the accurate recognition of abrasive grains
from the measured wheel surface. A detailed analysis of the grain size distribution characteristics and grain profile wavelength
of the fine diamond grinding wheel used for ultra-precision grinding is presented. The requirements of the spatial sampling
interval and sampling area for instruments to measure the surface topography of a diamond grinding wheel are discussed. To
recognize diamond grains, digital filtering is used to eliminate the high frequency disturbance from the measured 3D digital
surface of the grinding wheel, the geometric features of diamond grains are then extracted from the filtered 3D digital surface,
and a method based on the grain profile frequency characteristics, diamond grain curvature, and distance between two adjacent
diamond grains is proposed. A 3D surface profiler based on scanning white light interferometry is used to measure the 3D surface
topography of a #3000 mesh resin bonded diamond grinding wheel, and the diamond grains are then recognized from the 3D digital
surface. The experimental result shows that the proposed method is reasonable and effective.
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Translated from Journal of Dalian University of Technology, 2007, 47(3): 358–362 [译自: 大连理工大学学报] 相似文献
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Free-form surfaces have been widely used in aerospace, automotive and other fields. Due to its complex geometry, free-form surface inspection is generally conducted by touch-trigger or measuring probe-based Coordinate Measurement Machines or On-machine Measurement. Sampling strategy plays a decisive role in improving both measurement accuracy and efficiency, which is determined by sample size and distribution of sample points. However, it is difficult to simultaneously take the surface curvature, sampling density and approximation error into account, considering the complexity of surface geometry. In this paper, triangle mesh simplification is innovatively adopted in sampling planning to achieve multi-geometric constraints. As triangle mesh has outstanding advantages in representing the surface features, strong stability and is easy to modify its structure, free-form surface is converted to a dense triangle mesh. Triangle mesh simplification is implemented by iteratively contracting triangle edges. An improved quadric error metric is established to decide contraction order and optimal target vertices under discrete curvature constraint. Sampling density is controlled by limiting the triangle edge length. Detailed adaptive sampling algorithm under multi-geometric constraints is then developed. Both simulation and experiment are conducted to validate feasibility and robustness of the proposed method. The results are compared with uniform sampling and existing adaptive sampling strategy to show that the proposed method can prominently reduce sampling error when sample size is small. 相似文献
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以激光-机器视觉测量方式得到的曲面数据云为基础,探讨基于给定精度的曲面密集散乱数据点群的数据压缩以及几何建模方法。其中,根据激光测量方式和三维点群分布的特点,提出一种在给定采样精度基于曲率的曲面自适应采样的方法;通过激光扫描曲线间的采样点匹配为进一步数据压缩提供依据;并由度量曲面的初步网格点阵对测量点逼近程度好坏来进一步完成对曲面模型的修正。通过实例验证这种方法的可行性。 相似文献
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M. Shi Y. F. Zhang H. T. Loh C Bradley Y. S. Wong 《The International Journal of Advanced Manufacturing Technology》2006,30(1-2):54-60
This paper presents a triangulation method for modelling very large sets of cloud data. The three-dimensional (3D) data sets are produced by a machine vision system and/or coordinate measuring machine (CMM). The algorithm is suitable for processing the data collected from objects composed of free form surface patches especially with interior holes. This is accomplished from the 3D data sets in two steps. Firstly, the original cloud data is reduced into a simplified data set employing a data reduction technique (voxel binning method), in which the error between the cloud data and the meshed surface is used to control the data reduction. Secondly, the triangulation process starts with a randomly selected seed triangle. The triangular mesh extends outward by continuously linking suitable external points to it along the boundary edges of the meshed area. A complex free form surface with interior holes can be triangulated in one computing session without manually dividing it into several simple patches. The error-based data reduction parameters are extracted from the cloud data set, by a series of local surface patches, and the required spatial error between the final triangulation and the cloud data. Experimental results are given to illustrate the efficacy of the technique for rapidly constructing a geometric model from 3D digitised cloud data. 相似文献
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分析了复杂曲面CAD重构设计中的基本流程,重点介绍了重构设计中涉及的几个关键技术。首先,介绍一种基于Bezier曲线曲面造型原理的复杂曲面重构方法。该方法用三角网格对将离散点云进行拓扑划分,将一个复杂的零件曲面划分为多个小曲面;然后采用轨迹线生成技术重构复杂曲面中的特征线,采用网格优化技术提高重构效率;最后,采用曲面光顺技术,使重构后的曲面达到应用需求。 相似文献
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Heping Chen Ning Xi 《The International Journal of Advanced Manufacturing Technology》2008,35(7-8):680-696
Automatic trajectory generation for spray painting is highly desirable for today’s automotive manufacturing. Generating paint
gun trajectories for free-form surfaces to satisfy paint thickness requirements is still highly challenging due to the complex
geometry of free-form surfaces. In this paper, a CAD-guided paint gun trajectory generation system for free-form surfaces
has been developed. The system utilizes the CAD information of a free-form surface and a paint gun model to automatically
generate a paint gun trajectory to satisfy the paint thickness requirements. Complex surfaces are divided into patches to
satisfy the constraints. A trajectory integration algorithm is developed to integrate the trajectories of the patches. The
paint thickness deviation from the required paint thickness is optimized by modifying the paint gun velocity. A paint thickness
verification method is also developed to verify the generated trajectories. The results of simulations have shown that the
trajectory generation system achieves satisfactory performance. This trajectory generation system can also be applied to generate
trajectories for many other CAD-guided robot trajectory planning applications in surface manufacturing. 相似文献
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Zhang Guojun He Jiabing Zhu Haiping Chen Xuan 《Frontiers of Mechanical Engineering in China》2007,2(4):453-458
Stochastic statecharts are widely used in modeling systems. Considering that the comparability between different subsystems
can streamline the modeling process, a stochastic statechart is improved by using the abstract sub-system and general system
chart to express the comparability and integrity of a stochastic statechart respectively. Per formance data can be obtained
by using a continuous-time Markov chain, which is transformed from a manufacturing system model described by the improved
stochastic statechart. The case study shows that the improved stochastic statechart can effectively simplify the modeling
and performance evaluation process and the results are useful to the configuration and optimization of a manufacturing system.
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Translated from Journal of Beijing University of Technology, 2006, 32(8): 693–698 [译自: 北京工业大学学报] 相似文献