Case-based Reasoning Welding Fixture CAD System Development

Now it's difficult for the car body welding fixture to reuse the past experience and knowledge of experts.And this restricts the development of automotive body welding fixture efficiency and product quality.So it is important to develop an intelligent CAD system for body welding fixture based on case-based reasoning.Based on case-based reasoning,this dissertation develops a CBR-CAD system for car body welding fixture.The main research contents and progress are as follows:(1)After studying the classification and characteristics of body welding fixture,the dissertation puts forward the CBR-CAD idea based on body welding fixture.According to the needs analysis,I built a total of seven modules of the system framework: user management module,user workspace module,case-based reasoning module,welding fixture standard parts library module,quick assembly module,2D drawing module,BOM management module.Then I analyzed the CATIA document structure and command interaction mechanism and chose CAA as the development model.(2)Based on the analysis of the principle and characteristics of case-based reasoning,I focus on the key technology of case-based reasoning.Especially in the case of instance expression,on the basis of using the object model to create the object,I introduced the "pool" concept to create the object.All related data is distributed in the relationship pool,rule pool,parameter pool and method pool,which speeds up the creation of object speed.In the aspect of case extraction,the decision tree is extracted from the example of the body welding fixture,and then the nearest neighbor algorithm is used to retrieve the instance.The validity of the retrieval is verified by an example.Then I discussed how the conflict in the case of conflict exists and how the organization was organized and how it was maintained.(3)Combining CAA framework,I analyze how to parameterize in CATIA,and finally determine the parameterization technology based on knowledge engineering.Using database,I analyze the idea of standard parts creation.And then I developed the standard parts library and it can use CAA framework to read the parameters of knowledge engineering in real time,modify and reconstruct the model.Finally,I take the L block as an example to illustrate how to operate the database including retrieve data,filter data and sort data.(4)This dissertation presents a complete test on the CAD system of the welding fixture based on case-based reasoning.The working flow of each module of the system is illustrated by an example of the welding fixture of the vehicle body side,which verifies the feasibility and effectiveness of the system.