Surface Modeling And Assembly Simulation Based On Discrete Modal Decomposition

Based on the National Natural Science Foundation of China(51575484)"Theory and Method of Tolerance Analysis for Complex Assemblies Based on Number Theory",the surface modeling with deviation and assembly simulation research are carried out based on discrete modal decomposition method.Firstly,the deviation surface of the part is constructed when considering the tolerance principle.And then,the position of variant parts is determined in assembly.So,it can help designers complete assembly quality prediction in the stage of product design.Chapter 1:The background and significance of the research are described in detail,research Status of tolerance modeling at home and abroad is introduced.In addition,relative positioning of deviation parts and transmission of assembly error are at home and abroad introduced.Present the content and overall architecture of the paper in the end.Chapter 2:The theory of discrete modal decomposition method is introduced.The simulation process of the part surface based on the discrete modal decomposition method is discussed.Firstly,the geometric error vector field is constructed.Secondly,generating methods of coefficients of geometric errors and dimensional errors considering the tolerance principles are proposed in this chapter,and then the simulation surface is obtained according to the mathematical model of the surface topography.Finally,the feasibility of the method is verified by an example.Chapter 3:Methods of single-feature matching and multi-feature surfaces matching are discussed.Firstly,the corresponding points are selected according to the nearest-point query method of DT triangulation.Then the Euclidean distance between the corresponding points is used as the objective function.The positional deviation of the parts after assembly is obtained,and the deviations of the position in the course of the movement are obtained by further calculation.Chapter 4:The assembly and positioning relations of the parts at the feature level are introduced.Determine the deviation transmission and accumulation route of the assembly in the three-dimensional space through the assembly and positioning relation of the parts.Dimensional coordinate deviation of the assembly is obtained by homogeneous coordinate transformation.The 4×1 dimensional vector is used to describe the spatial points.The mating error between the parts is calculated according to the simulation surface and the 3D cumulative deviation of the assembly is obtained by homogeneous coordinate transformation.Chapter 5:Introduce the parts surface topography model and kinematic analysis prototype system based on Matlab,and provide data processing flow and function modules of the system.Chapter 6:The research contents of this paper are summarized,and the future research directions are prospected.