Research On Knowledge And Coding Of Assembly Sequence Planning

Computer Aided Assembly planning(CAAP) is an important research issue on assembly planning,and the research method of ASP has been divided into geometric reasoning and knowledge-based reasoning. With the introducing of experience of human being and heuristics assembly rules in knowledge-based reasoning, the combinational explosion of results problem which usually occurred in geometry reasoning, have been largely reduced, it avoided the blindness of ASP.How to reusing existing experience and knowledge is an important problem in assembly planning. Through the analysis and imitation of method in Computer Aided Process Planning(CAPP), Group Technology has been introduced into ASP, part coding has been expanded to assembly coding to search for similar objects, and through the assembly coding searching, parts matching and sequences correction, to realize the reuse of assembly sequences.This thesis defined concept of assembly tree and Binary Rooted Assembly Tree(BRAT), introduced the computer representation and storage method of BRAT, and established assembly knowledge base which including ASP knowledge and assembly rules, to store fundamental connection, transmission knowledge and heuristic assembly rules, and introduced how to represent assembly knowledge in computer.The common mechanical assembly was divided into basic level, component level, product level with the idea and method of hierarchy. By using the method which similar to parts coding to encode assembly unit, defined the method of general assembly coding and meaning of the codes, described assembly unit from name and category, shape and size, assembly complexity three aspects, further divided and encoded the common assembly units like shaft type and box type assembly.Searched the assembly sequence knowledge base with the key features of assembly names and codes, and it is a retrieving method which is gradually relax the matching conditions. By matching and mapping the same or similar parts, completed the assembly sequence planning, and then update the database. In order to define the difference of two BRAT in database, the Robinson-Foulds distance and its deduction form, and the encoding method of BRAT has been introduced. A classic mechanical product has been introduced to illustrate the ASP process proposed in this thesisBased on CATIA and Secondary Development Technology, a function module was created to introduce the principle and process of the realization of the system.