共查询到19条相似文献,搜索用时 291 毫秒
1.
2.
3.
4.
利用产品原形的三维测量数据,通过逆向工程设计新产品、改进或生产旧产品的过程中,曲线拟合及曲面重构是关键。采用B样条曲线拟合及B样条曲面重构,曲线更改灵活,曲面连接光滑,在逆向工程中具有广泛的实用性。 相似文献
5.
基于实时重构的自由曲面自适应布点方法 总被引:1,自引:0,他引:1
针对现有的自适应算法计算量庞大、在工程中可应用性不强的缺陷,提出在等距法布点的基础上,对测量点进行实时重构来指导三坐标测量机根据曲面本身特性自动增加测量点的方法。测量过程中,当通过拟合五次B样条曲线、三次B样条曲面判断现有测量点不满足精度时,利用两侧测量点的曲率半径,计算出需增加测量点的准确位置,重新拟合包含新检测点的检测样本,直到满足精度要求。以曲面样件为例,辅以计算机图形可视化验证该算法,实验结果表明该方法测量精度及重构精度均可满足数字化检测要求,且在工程应用中相比曲率自适应算法其计算量大幅下降,有效提高了曲面检测效率。 相似文献
6.
7.
半正交B样条小波及其在曲线曲面光顺中的应用 总被引:2,自引:0,他引:2
基于B样条基函数及其对应的小波不具有平移正交性,因而不能用现有Mallat快速算法进行小波分析的特点,从B样条基函数以及多分辨分析的定义出发,用严格的数学推导实现半正交B样条小波的分解重构算法。详细阐述该算法在准均匀三次B样条曲线中的运用,并给出一条复杂曲线及一个复杂曲面的分解重构实例,表明该方法能够在复杂曲线曲面的光顺中取得良好效果。 相似文献
8.
该文针对CMM测量数据呈扫描线分布的特点,用Visual C++开发软件结合OpenGL图形显示库,以非均匀B样条基为核心,开发了非均匀B样条曲面重构软件.通过与专业逆向造型软件imageware的比较,证明了该软件能快速、有效、精确地完成曲面重构过程,为整个逆向工程节省时间. 相似文献
9.
10.
以发动机气道为研究对象,探讨了逆向工程在汽车发动机设计开发中的应用.利用光学扫描测量系统得到发动机气道曲面的点云数据,并进行数据处理和曲面重构得到三维数模,最后利用逆向工程得到的三维数模进行模具设计. 相似文献
11.
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
12.
Ming-Chih Huang Ching-Chih Tai 《The International Journal of Advanced Manufacturing Technology》2000,16(9):635-642
Reverse engineering has become an important tool for CAD model construction from the data points, measured by a coordinate
measuring machine (CMM), of an existing part. A major problem in reverse engineering is that the measured points having an
irregular format and unequal distribution are difficult to fit into a B-spline curve or surface. The paper presents a method
for pre-processing data points for curve fitting in reverse engineering. The proposed method has been developed to process
the measured data points before fitting into a B-spline form. The format of the new data points regenerated by the proposed
method is suitable for the requirements for fitting into a smooth B-spline curve with a good shape. The entire procedure of
this method involves filtering, curvature analysis, segmentation, regressing, and regenerating steps. The method is implemented
and used for a practical application in reverse engineering. The result of the reconstruction proves the viability of the
proposed method for integration with current commercial CAD systems. 相似文献
13.
为实现对微结构表面轮廓参数的精确测量,用基于像散原理的并行共焦检测系统获取微结构表面的三维信息,进而实现对微结构表面参数的可视化测量。考虑到微结构表面特点,采用累加弦长双三次样条插值曲面对其表面进行重构。并选择高的插值细分倍率获得连续光顺廓形表面,通过拾取拟合曲面上的点而不是廓形局部三角面片上的点实现三维廓形参数评定。由重构曲面模拟结果显示:累加弦长双三次样条重构微结构表面可以有效地实现对微结构表面参数的精确测量。 相似文献
14.
Cheng SiyuanZhang XiangweiXiong Hanweiculty of Electromechanical Engineering Guangdong University of Technology Guangzhou China 《机械工程学报(英文版)》2005,18(3):321-324
0 INTRODUCTIONReverse engineering is a technology to establish CAD mod-els from samples, prototype, molds or manufacturing parts bydigitization. In many research and application areas such asmedical science, biomedical engineering, and CAD/CAM, anobject i… 相似文献
15.
16.
基于散乱数据点的B样条曲线反求方法 总被引:1,自引:0,他引:1
逆向工程中,由3D散乱数据点反求B样条线,常用的方法是用最小二乘法通过B样条曲线逼近来拟合出B样条线,因而存在拟合误差,更无法提前预知需要多少控制顶点才能达到所要求的逼近精度.我们从B样条曲线的数学定义出发,对B样条线的重构进行了研究,通过反求B样条多边形控制顶点的方法,来反求得到插值B样条线,并以三次均匀B样条线的反求为例,通过编程加以实现验证. 相似文献
17.
18.
The scraping process involves traditional manual work and is an important technique for producing flat bearing surfaces with lubricating grooves on a sliding surface. In order to meet the requirements of precision engineering, the scraped surface should have an equally distributed pattern with a required number of high points per unit area while retaining good flatness. In the machine tool manufacturer’s workshop, however, the quality inspection of scraped surfaces still depends on human eyes. In this study, a 2-D evaluation system is first developed using image processing so that the peak points per area of square inch (PPI) and the percentage of points (POP) can be quantified as parameters. A vision-assisted laser focus probe system is then developed to measure the 3-D form of the scraped profiles. The laser probe is made of a DVD pickup head based on the astigmatic principle. Driven by an XY stage, the entire scraped profile can rapidly be scanned. The quality of the scraped surface can thus be interpreted in a more scientific manner. Based on the measured 3-D data, new evaluation methods are proposed for five parameters, namely the PPI, POP, height of points (HOP) or depth of surroundings (DOS), flatness, and oil retention volume. Experiments show that the 3-D system is consistent with the 2-D system. It not only reveals more surface quality parameters but also uncovers more characteristic surface phenomena than the 2-D image system. 相似文献
19.
A method is introduced to predict uncertainties of the B-spline freeform surfaces that are reconstructed from the measurement points for inspection of freeform surfaces. The uncertainties of a reconstructed B-spline surface are modeled by variances of coordinates of points on this freeform surface. Prediction of the uncertainty at any location on the reconstructed B-spline surface is carried out in two steps: (1) estimation of variances of the B-spline surface’s control points introduced by the surface reconstruction process, and (2) propagation of the variances from the control points to the points on the B-spline freeform surface. In this research, the variances of the control points of the reconstructed B-spline surface in all three directions are considered to improve the accuracy of uncertainty prediction in the regions with significant changes of geometric shapes. Both the errors and uncertainties at different locations on the reconstructed surface are considered in freeform surface inspection to compare the manufactured surface against the design surface and its tolerance. The developed method has been applied to two case studies to demonstrate its effectiveness. 相似文献