共查询到20条相似文献,搜索用时 62 毫秒
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针对在分层过程中,如何调节分层效率与成型精度之间矛盾的问题,通过对现有分层算法,分层过程中初始分层厚度确定、数据精简及轮廓线拟合等方法的研究,提出了一种基于点云距离变化的自适应分层算法。基于散乱点云模型,通过计算每层切片中各线段与最近点的距离,筛选出了距离的最大值;计算了相邻两层之间最大距离的变化率,然后与设定的阈值进行了比较,自动地调整了分层厚度;经过对斗齿点云模型的分层实验,验证了算法的有效性。实验结果表明:该算法能够在一定程度上平衡分层效率和成型精度之间的关系,并且适应于高精度、型面较复杂模型的分层。 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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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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为提高自由曲面测量速度和重构精度,基于三坐标测量机CMM,提出自适应测量的曲面重构方法。测量过程中,通过不断拟合样件上已测点,预算待测点及其测量矢量,指导CMM自动采集曲面上数据。由点云拟合自由曲面模型后,检验拟合模型上点与样件上相应点的误差;若误差偏大,则在测量点云中加入检测点后重新拟合曲面,进一步检测重拟合实体模型直至满足精度要求,得到精准数据点和精致的自由曲面模型。辅以计算机图形可视化实例验证本法,测量精度及其重构精度可达μ级,具有自由曲面特征的零部件整个逆向周期呈数量级下降,算法鲁棒性强。 相似文献
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基于散乱数据截面线的曲面重构算法研究 总被引:8,自引:0,他引:8
提出了一个新的散乱数据的曲面重建算法,该算法采用一组平行平面去剖切点云,除恰好位于该截面上的数据点之外,如果一数据点与某一截面的距离小于给定的距离域值,则将其投影到该截面上,把上述点通称为用距离域值来确定截取点:将每一张截面上的截取点用最小二乘法拟合成B样条曲线,然后对生成的一组B样条曲线进行处理,即统一节点矢量、重新参数化和起点相对应,重新拟合一组闭合B样条曲线,再对其运用蒙面操作,从而构造一张曲面。 相似文献
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基于光线测试的点云数据与CAD模型归属处理研究 总被引:1,自引:0,他引:1
针对非接触测量方法进行复杂型面零件数字化检测中,点云数据量大及点云与计算机辅助设计模型配准和偏差计算中存在着如何有效处理点云与测量面的归属问题,提出了采用光线测试模型确定计算机辅助设计模型的可见面.以待测计算机辅助设计模型面的采样型值点作为光源,其外法矢作为光源方向与计算机辅助设计模型进行相交测试,确定出测量可见面,然后进行点云与可见面的归属处理.试验结果证明了该方法的有效性. 相似文献
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M. Y. Zhou J. T. Xi J. Q. Yan 《The International Journal of Advanced Manufacturing Technology》2004,23(1-2):20-27
Adaptive slicing varies layer thickness by taking the geometry change of the CAD model in the build direction into account to improve surface finish. Direct slicing generates exact slice contours from the original CAD model and avoids an intermediate representation, known as an STL file. At present, most direct slicing approaches are restricted to some CSG solids or some CAD systems. In this paper, an approach toward adaptive direct slicing with non-uniform cusp heights independent of CAD systems for rapid prototyping is presented. First the geometry model is imported into the adaptive direct slicing system from CAD systems using the standard STEP format. Using OpenGL graphics libraries, the solid model is then displayed and the user is prompted to specify the allowable cusp height for each highlighted surface. Lastly, the CAD model is sliced adaptively with different cusp heights (tolerance requirements) for different surfaces. With non-uniform cusp heights, adaptive slicing has a higher efficiency. Implementation details and results are also presented. 相似文献
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AutoCAD环境下直接适应性切片方法及实现 总被引:1,自引:0,他引:1
数据分层处理是快速成型技术的核心.适应性分层可以有效解决快速成型中成形精度和速度之间的矛盾.利用AutoCAD二次开发技术,通过比较相邻层片截面的面积确定切片厚度,提出了一种基于CAD模型的直接适应性切片方法,并对该方法进行了实现,同时与定层厚切片方法进行了比较,最后给出了分层实例并对结果进行了分析. 相似文献
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M. Y. Zhou 《The International Journal of Advanced Manufacturing Technology》2004,24(5-6):345-352
Slicing is a fundamental process planning task and an important procedure in rapid prototyping. However, most research currently focuses on the slicing of homogeneous objects and few approaches for slicing of heterogeneous objects have been reported in the literature. In this article, we present an approach for adaptive slicing of functionally graded material objects. Unlike homogeneous objects, functionally graded material objects contain both geometry and material information. The layer thickness is computed by considering not only geometry but also material variation along the build direction. The continuous material distribution in each layer is discretised into step-wise gradings by subdividing the slice into sub-regions, which can be regarded as homogeneous material regions. An algorithm that summarised the slicing procedure is described and an example is also presented. 相似文献
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S. H. Sun H. W. Chiang M. I. Lee 《The International Journal of Advanced Manufacturing Technology》2007,34(7-8):702-701
Slicing a 3D graphic model into layers of 2D contour plots is an essential step for all rapid prototyping (RP) machines. Various
methods are available, such as stereo lithography (STL) file slicing, direct slicing and adaptive direct slicing. Amongst
these, adaptive direct slicing is the most advanced for its capability of adapting the slicing thickness according to the
curvature of any contour. In this study, an adaptive direct slicing method complete with the algorithm for calculating the
thickness of each layer is proposed. As an illustration of the method, the algorithm was programmed within the commercial
CAD software package, PowerSHAPE. The method was shown to be fast and accurate in comparison with STL file slicing and direct
slicing, which both used a constant layer thickness.
An erratum to this article can be found at 相似文献
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Improved intermediate point curve model for integrating reverse engineering and rapid prototyping 总被引:1,自引:1,他引:0
V. K. Kumbhar P. M. Pandey P. V. M. Rao 《The International Journal of Advanced Manufacturing Technology》2008,37(5-6):553-562
Direct integration of reverse engineering and rapid prototyping removes two intermediate steps of surface fitting from point
cloud data and STL file generation from CAD models. Therefore errors introduced due to surface fitting and triangulations
are eliminated and also the process of STL data validation and repair is avoided. Intermediate point based curve model (IPCM)
method is one of the promising approaches for direct integration of reverse engineering and rapid prototyping however this
approach has the limitation that it cannot handle objects, which result in multiple contoured slices. Moreover, IPCM based
method is implemented with layers of constant thickness slices, and adaptive slicing with this method is not attempted. The
present work is an attempt towards improving the capabilities of IPCM based method by overcoming the above-mentioned two limitations.
The new system developed here has been tested on many parts, which demonstrates the capability of the proposed system.
An erratum to this article can be found at 相似文献
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Xue-Chang Zhang Jun-Tong Xi Jun-Qi Yan 《The International Journal of Advanced Manufacturing Technology》2006,30(1-2):70-75
It is necessary to smooth point cloud data in reverse engineering or the inspection of free-form surfaces because noisy points will have a negative influence on the post-processing of this data. The big problem in smoothing point cloud data is how to solve the dilemma between removing noisy points and keeping feature boundary information, whilst controlling the diffusiveness of noisy points. In this paper, the theory of anisotropic heat conduction is adopted to establish a mathematical model of point cloud data smoothing. The point cloud data can be considered as a temperature field with an adiabatic boundary. So the heat is only conducted inside the temperature filed and has no effect on the outer side. For point cloud data, it means that the smoothing is only on the local area, which makes a good balance between deleting noisy points and keeping feature boundary information. The method has been implemented by using two cases for practical application, and the result proves its efficiency. 相似文献
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In this study, a complete 3D surface reconstruction method is proposed based on the concept that the vertices of surface model
can be completely matched to the unstructured point cloud. In order to generate the initial mesh model from the point cloud,
the mesh subdivision of bounding box and shrink-wrapping algorithm are introduced. The control mesh model for well representing
the topology of point cloud is derived from the initial mesh model by using the mesh simplification technique based on the
original QEM algorithm, and the parametric surface model for approximately representing the geometry of point cloud is derived
by applying the local subdivision surface fitting scheme on the control mesh model. And, to reconstruct the complete matching
surface model, the insertion of isolated points on the parametric surface model and the mesh optimization are carried out.
Especially, the fast 3D surface reconstruction is realized by introducing the voxel-based nearest-point search algorithm,
and the simulation results reveal the availability of the proposed surface reconstruction method. 相似文献