Some Problems In Study Of Digital Pre-Assembly System

In the 21st. century, competitions between different manufacture enterprises become more and more impetuous, as a newly developed technology, IT (Information Tech.), is making a stupendous effect on today's manufacture industry. Production is changing from single-volume mode to diverse-composite one, therefore, the rationally use of information technology is going to be the key factor for those companies to succeed in the competition.Digital pre-assembly is a chief technology that used a lot in today's advanced techniques such as agile manufacture and virtual manufacture etc. It aims to establish a virtual intermediate environment, where the 3D models designed by different CAD softwares can be imported, and re-displayed as their actual state. The virtual system plans out a reasonable assembly sequence for models according to their geometrical and topological features, and simulate the movement of each part by the calculated sequence under certain platform. It also exams the mis-designs and weakness while planning, and backs off to designers as early as possible if there is any. Thus, the assembly process can be improved and optimized so as to save the operating cost, reduce product's design cycles, and enhance the commercial competition capabilities.This thesis is sponsored by the Special Funds for Major State Basic Research Program (973) of China under grant 2002CB312106. In this thesis, some technical problems in digital pre-assembly system are discussed based on the former research and proposed works, including discrete face model based simplification, Brep model based simplification, interference checking of assembly sequence programming, etc.The thesis is organized as follows:Chapter 1 introduces the Digital pre-assembly system, including generated background, research content, develop status quo, key techniques etc. And also describes the objective of this thesis, presents the research frame.On the basis of related studies, Chapter 2 mainly talks about the LOD (Levels of Detail) model representation, discusses Top-Down design mode, also in detail, introduces the discrete face model representation which used in digital pre-assembly system.Chapter 3 gives a simplification method for discrete face model, which consists of invisible face simplification and screw thread simplification, and presents theoperation result at the end.Chapter 4 gives another simplification method wholly for Brep model. This method also divided into two parts, tiny single face simplification and concavo-convex texture simplification.Chapter 5 discusses interference test in pre-assembly process, presents an original strategy which based on 2D projection using OpenGL as an accessorial tool. Algorithms for dynamic interference test and static interference test are given out.Chapter 6 introduces the ASM digital pre-assembly system, the one developed by our research team, shows the real application of model simplification, sequence plan and emulation, also analyzes the final results.In Chapter 7, all achievements of the thesis are summarized and the future research work is sketched out.