Research On Composite Surface Reconstruction Based On The Closed-loop Theory

Reverse Engineering(R&E) is a new R&D technology, developed since 1980. At present, it has been widely used in various of industries. Different with the traditional R&D process, R&E technology combines the application of many high-tech in digestion and absorption of the original products, to realize rapid development of new products. Based on the existing R&E idea, a new type of R&E design method is proposed. It realizes the measurement and modeling a closed-loop operation. This new design method greatly reduces the development cycle and costs, so it has great practical value. Focused on this new design idea, the key technologies of R&E are studied in this paper, and a special R&E system was developed.Familiar with the characteristics of different measurement technologies, the CMM was selected for data collection. In order to realize the automatic measurement, adaptive measurement method is the key study in this paper. Based on the study of the existing adaptive measurement methods, three diffrent Bezier adaptive measurement methods are introduced. Comparing the experimental results, the curvature continuous Bezier adaptive measuring method performs the best prediction effect. Therefore, it is used for automatic measurement in this paper. By the study of composite surface measurement planning, the actual composite surface automatic measurement is realized with the written DMIS language.In this paper, B-spline surface is used for free surface reconstruction. Data points, control points, node vector and the B-spline basis function are the basic elements to construt a B-spline surface, so in order to get a reconstrution surface, the algorithm of these basic elements are studied. Firstly, after comparing the results of non-uniform and quasi-uniform B-spline curve reconstruction for data points, which are free distributed in a line, the non-uniform B-spline is used for its adaptive characteristic to general situation as the basis function. Secondly, through the programming, the 3th, 4th and 5th B-spline surface reconstruction are realized. By the application example, we can see that the 4th and 5th are not suitable for their concussion. Thirdly, the 3th B-spline surface reconstruction algorithm is tested by a known mathematical model. Finally, the composite surface reconstruction is also realized according to the joining theory, and an example is used to verify the effectiveness of surfaces joining together.A R&E system is developed to realize the new R&E design idea, it establishes the link between measuring and modeling. It can calculate the data of test points, output the automatic test procedures which will guide the CMM executive real-time testing. If the test result can not satisfy the needed precision, then these actual test points can be used to modify the reconstruction surface, and again testing, until the reconstruction precision meets the request. At the end of this article, we take two composite surface examples to test this software, and the results show that its reconstruction function is in high efficient and precise. Therefor, this new R&E system can satisfy the general product development requirements, and has high practical application values.