Development of B-spline Curves and Surfaces Reconstruction Techniques for Massive Point Data in Reverse Engineering

• Main Authors: Kuan-Yuan Lin, 林冠元
• Other Authors: Jiing-Yih Lai
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/20167258418684123493

博士 === 國立中央大學 === 機械工程研究所 === 99 === Reverse engineering is a process of acquiring the sirface model from the digitized points of a physical part. It usually plays an important role on the development of new products. In addition to the implementation and integration of plenty of skills, a reverse engineering process always needs considerable time and efforts for generating satisfactory surface models as it is experience-oriented. In this study, we propose an automatic surface reconstruction method to deal with the above- mentioned problem, which can improve both the efficiency and quality of the reconstructed surfaces. Its main characteristic is as follows: different from the common methods where only a set of triangle meshes is used as the input, a set of boundary contours/curves are added for constraining the internal of external boundary of the final shape. It not only can save the efforts required for the pre-processing of the original meshes, but also can improve the surface quality and the efficiency of the entire process. For the task of automatic surface reconstruction, some specific algorithms for processing points, meshes, curves and surfaces are provided first. An intact process integrating all the related algorithms is then introduced in detail. In addition, the related algorithms for curves are further applied in computer-aided manufacturing for automatic generation of Nurbs-based NC paths from linear and circular NC paths. Concretely speaking, the techniques developed in this study can be listed as follows: (1) An error-bounded curve fitting method is proposed to realize the goal of automatic curve construction. It not only takes the minimization of the sum of squared deviations, the strain energy minimization and the boundary continuity constraints into consideration, but also utilizes the allowed maximum and root-mean-square errors as extra constraints; (2) A method of NC code conversion is proposed for indirectly achieving the high-speed and high-precision machining under low-cost conditions. It can transform a plenty of conventional G01 codes into the less G-codes of B-spline curves; (3) A NURBS interpolator is proposed for effectively realizing the aim of high-speed and high-precision machining. It can generate sampled points on curves appropriately to meet the confined chord error, feedrate, acceleration and jerk; (4) A surface warping method is proposed for providing high-efficiency computing and suitable surface quality. It was composed of the creation of a specific initial surface and the shape-modifying operations; (5) An automatic surface reconstruction method with extra constrained boundary contours is proposed for dramatically reducing the time spent for surface reconstruction in practice. It can automatically generate a set of surface patches with G1 continuity across the shared boundaries in an efficient way according to a triangle mesh and extra boundary curves.