Research On Assembly Sequence Planning And Accuracy Analysis Based On Assembly Information Model

Assembly accuracy is one of the important indicators for evaluating mechanical products assembly quality,and its analysis technology is an important means to ensure product assembly performance.Since there are multiple factors that affect assembly accuracy,and they share the coupling relationship between them,simulation results often differ significantly from the actual situation.With the rapid development of information technology,digital process simulation has become an effective way to improve assembly quality.Therefore,this dissertation conducts the research on the construction of digital models for mechanical products,assembly sequence planning,and assembly accuracy calculation,in order to obtain optimal assembly process parameters and provide a theoretical basis and implementation technology for improving the assembly accuracy of products.The main work of this dissertation is as follows:1.A recognition method based on basic geometry is proposed to address the issue of inefficient on assembly feature recognition in parts.According to the concavity and convexity between the triangulation model patches,the solid model is segmented.The random forest algorithm is used to recognize the basic geometry,and the classification tree representing the mapping relationship between the geometry and assembly features is established to realize the recognition of assembly features in parts.Based on the establishment of a feature importance evaluation function in the model,the key features are extract while the integrity of the parts is ensured.Then a hierarchical information model is proposed based on the abstraction level of assembly information to achieve effective management of assembly information.2.Aiming at the insufficient intelligence of assembly sequence planning,a feasible assembly sequence search method and a multi-factor assembly sequence optimization method are proposed.The assembly constraint model constructed in a spherical coordinate system is used to express the motion constraints of the contact surfaces between parts.By virtual of set operations,the actual motion states under multiple constraints can be obtained.Based on the idea of "disassembly and assembly sequences are reversed ",a geometrically feasible assembly sequence set is obtained.A comprehensive evaluation system for assembly efficiency of assembly sequences has been established,and the relative weights of influencing factors have been determined by using the grey system correlation entropy theory,achieving optimization of assembly sequences for similar mechanical products.3.In response to the problems of multiple factors affecting assembly accuracy and the difficulty in searching for 3D dimension chain,a search method based on determining assembly sequences is proposed.A unified expression form for deviation sources such as dimensional tolerance and geometric tolerance is constructed.In the deviation transfer model,the mating faces between parts are obtained based on the assembly sequence,and then the transfer path of deviation in the parts is searched based on the shortest path theory,hence forming a complete three-dimensional dimension chain.By using Monte-Carlo method to calculate assembly accuracy,and conducting statistical analysis on the obtained results,the design scheme can be evaluated and improved.4.Based on the research results of the dissertation,a visualization system for assembly process simulation has been developed.The system integrates simulation algorithms and natural interaction methods,and verifies the feasibility and effectiveness of the system using actual mechanical products as examples.