Research On The Process Parameter Decision Method Of Hull Sub-assembly Welding Based On Knowledge Modeling

Sub-assembly is an intermediate product in the process of ship construction,which involves cutting,assembling,welding and other processes.In the process of sub-assembly welding,the verticality error,floor straightness error,floor size error and other precision deviations will occur,which will affect the quality of the section and the whole ship.Some operators can adjust the welding process parameters such as welding current and welding speed according to the actual welding state and their own long-term experience,so as to reduce the deviation of group vertical accuracy during welding.This method can reduce the cost of ship construction and improve the efficiency of ship construction compared with relying on a large number of compensation processes such as fire engineering and secondary repair.However,there are also some problems in the adjustment of subassembly welding process parameters based on experience.On the one hand,the adjustment of process parameters by operators needs to be scientifically verified.This problem can be verified by collecting relevant data and studying the relationship between the accuracy deviation of subassembly welding and the welding process parameters.On the other hand,the method of adjusting process parameters according to experience is difficult to be inherited,so experience needs to be converted into knowledge by means of mathematical model,so that it can be popularized and applied in the manufacturing field.Therefore,the main contents are as follows:(1)Designing an experimental system for batch acquisition of the deviation of the welding accuracy of the sub-assembly.In the traditional way,the verticality error and the straightness error data of the subassembly are collected for a long time,and it is necessary to develop a hardware system that can batch-acquire the accuracy deviation information.In this paper,based on the visual sensor and spatial coordinate transformation variance design sub-assembly,the precision deviation data acquisition system is used.Open CV is used to extract the laser features,and the sub-assembly verticality error and straightness error data are calculated in batches.Accumulate data foundation for subassembly welding knowledge modeling.(2)Study on the relationship between accuracy deviation and welding process parameters.Analyze the error source of the accuracy problem of the current sub-assembly welding,the precision control standard of the research sub-assembly,and the descriptive statistical analysis for different types of sub-assembly welding.At the same time,in order to explore the "experience" form of the workers,the experience form of the adjustment of the process parameters of the workers in the sub-assembly welding work was mastered in depth.(3)Sub-assembly welding modeling based on VPRS.In this paper,the variable precision rough set theory is used to study the relationship between welding process parameters and sub-assembly welding precision deviation.This process includes: data preprocessing;building a group of welding decision model tables;data processing;VPRS model reduction finally obtained four sub-assembly of CO2 welding VPRS model.(4)Model verification and process parameter decision making.The accuracy of the model was verified by the ten-fold intersection method,and the application effect of the model was verified by comparative experiments.In order to extract the most appropriate model rules in the sub-assembly welding process for reasoning decision,the " sub-assembly welding process parameter decision" small program was developed.When the model was applied to the longitudinal girder sub-assembly line in a shipbuilding company in Shanghai,the acceptance rate of verticality error,straightness error and dimension error on the sub-assembly line increased by about 2%.