Research On Virtual Assembly Hybrid Model Construction Technology And Its Application Based On Local Reverse

Complex products of small batch or single-piece production are mainly assembled by manual assembly and repair, which process requires continued cycle trail assembly, trimming and re-assembly until the assembly requirement is met. The whole assembly cycle is very long, and the assembly efficient is very low, which seriously affected the rate of product development and equipment.Aiming at solving this problem, this dissertation studies the methods and processes of building virtual assembly hybrid model which can be used in assembly simulation from the cloud data collected by detecting the surface of physical objects, which can convert the trial assembly of physical model to the trial assembly of virtual model, predict the assembly precision before the actual assembly, timely guide the workers on-site repair and adjustment, greatly improving the efficiency of assembly.The first chapter summarizes the key technologies on the research of conversion process from point cloud model to virtual assembly hybrid model at home and abroad, discusses the existing problems of these technologies, gives the subject source and the research content, and introduces the organization structure of this dissertation.The second chapter proposes a surface building method of assembly feature based on local reverse. With satellite truss structure as the research object, this chapter analyses the composition of its assembly feature surface, builds block guide template library based on design model for fast automatic segmentation of the assembly feature surface of point cloud model, and construct the assembly feature surface using local reverse method.The third chapter researches the extraction method of geometric precision information based on the measurement point cloud data. For the dimensional precision information, this chapter puts forward the method based on oriented bounding box to extract the dimension value fast and one-time, then the size error value is obtained by comparison with the ideal value. For the form and position precision, this chapter establishes the corresponding optimization mathematical model according to the minimum zone method, and proposes a method based on improved genetic algorithm to quickly get the accurate values conforming to the definition.The fourth chapter presents the construction technology and its application of virtual assembly hybrid model integrated assembly feature. In order to solve the next two problems:common facet model cannot be directly assembled and ideal geometric model does not reflect the actual part geometry processing morphology, this chapter puts forward constructing a virtual assembly hybrid model with a hierarchical structure, which can associate with triangle mesh model representing the real physical surface and assembly feature containing assembly feature element, geometric precision and assembly constraints. This chapter also puts forward a method of using assembly constraints and pose transformation to implement assembly positioning, then gives the application of the hybrid model in virtual assembly simulation of truss structure.The fifth chapter describes the development of the prototype system based on the CAA secondary development technology in CATIA system and MATLAB algorithm toolbox, which includes the overall design, user interface and function module of the system.The six chapter summarizes the achievements of this dissertation, and discusses the area which needs to be improved in further research.