Mô hình hóa bề mặt trong CAD/CAM dựa trên thuật toán Nurbs

Trong quá trình thiết kế số, mô hình hóa bề mặt yêu cầu độ chính xác cao nhằm hỗ trợ hiệu quả cho các lĩnh vực sản xuất cũng như là công việc tích toán số. Bài báo trình bày những kỹ thuật mô phỏng bề mặt dựa trên thuật toán NURBS (non-uniform rational B-spline). Các mặt NURBS có thể dễ dàng dịch sang nhiều phần mềm CAD/CAM, thuận lợi trong công việc mô phỏng và ứng dụng các phương pháp tính toán phần tử hữu hạn | Science & Technology Development, Vol 14, 2011 SURFACE MODELING FOR CAD/CAM BASED ON NURBS Tat-Hien Le(1), Nguyen Xuan Hung(2), Vo Trong Cang(1) (1) University of Technology, VNU-HCM (2) University of Science, VNU-HCM (3) University of Technology, VNU-HCM (Manuscript Received on May 16th 2011, Manuscript Revised January 01st 2012) ABSTRACT: In the digital design process, surface modeling is required to be as accurate as possible for the effective support of production as well as for numerical performance analysis. This article reviews the geometric modeling techniques, based on non-uniform rational B-spline (NURBS). The NURBS surface can be readily translated into many CAD/CAM packages (Computer Aided Design/Computer Aided Manufacturing), which is more convenient for visualization performance and finite element methods. Key words: Surface modeling, NURBS, CAD/CAM, visualization. [8,1]. 1. INTRODUCTION The main problem is the parameterization of B-spline surface. It needs Surface modeling is the key to integration of design, analysis, manufacturing, and other calculation [3]. There are two principle categories for surface fitting techniques. The first one works with reverse engineering in two steps; first the given data points are rearranged into the rectangular mesh, then the surface is constructed by some matrices inversion and Bspline algorithm procedures. The first problem is that the data points are often scattered. The second problem comes from the matrices to be estimated from an initial unknown surface. The approximation of surface fitting using genetic algorithm is developed by Birmingham [5], Le et al [6]. However, this method gets stuck in case of complicated surfaces. The main contribution of this research is to use non uniform B-spline (NUB) surface fitting through a GA technique. This approach has more advantages with regard to surface representation, and fairness of the interior surface. inversion. In fact, the matrices inversion .