Research For Big Fixture Designing On Case-Based Reasoning

Computer aided fixture planning(Fixture CAD) is one of the key techniques of research in area of computer aided fixture design. The knowledge based fixture have some shortcomings. The key problems of traditional knowledge based fixture planning system include the bottle neck of knowledge getting, no self-learning ability and poor adaptability. These problems need more research work. To use CBR in big fixture design system can take full advantage of exist designs, can avoid some technology difficulty to some extent. This thesis analysis the research work done by international and domestic scholars. Summarized the important problems Case-Based big fixture design system need to be solved and proposed current solutions. The research work done as follow.Researched the typical model and the workflow of CBR big fixture design system. Compared the main reasoning techniques and summarized their good qualities and problems. Described the key technics of CBR. Validated the feasibility to use CBR in the big fixture design system.Proposed the big fixture case representation model which supports the full process of case based fixture design. By analysis the information requirement of case based fixture planning, setup the information model to support demand of fixture case retrieval and case modification and case organization. Use the frame method to represent the model, and establish the database structure model for the case model so as to meet the information requirement of fixture case retrieval, case modification and case base maintenance.Study the fixture case retrieval algorithm which combine use of template retrieval method and nearest neighbor retrieval method. Base on the analysis of fixture structure similarity, use template retrieval method to carry out total structure retrieval and then use nearest neighbour to retrieval the detail structure similarity to ensure the big fixture structure reuse ability.Researched the navigation based module of the CBR big fixture design system. Use the navigation module into the CBR system exactly and effectively, designers can retrieval the cases very expediently. The navigation module lead designers to retrieval the cases step by step effectively. Besides, the process of navigation customization is also the process of preserving basic information of big fixture. Then designers can use template retrieval method very expediently because of the basic information. On the other hand, the navigation module is also a independence cell, new cases will be created according to navigation customization. Then save the successful case to the case database.Base on above-mentioned key technologies, take advantage of Microsoft Visual C++, PTC's Pro/Toolkit develop the prototype system on the platform of CAD package and Oracle server. Validate the feasibility of these techniques to a certain extent.