Constant Current Control Of The Welding Process And Nugget Size Prediction System

Resistance spot welding process and quality control are always one of important research subjects in welding field, adopting the intelligent control technology has already become its certain trend. In this thesis, on the basis of fuzzy control and artificial neural networks, the idea of spot welding quality control, which integrates constant welding current fuzzy control with artificial neural networks forecast of spot welding nugget sizes is presented. A spot welding fuzzy controller is designed, a nugget sizes forecast model is established and the spot welding constant current fuzzy controller is initially realized in this thesis.Firstly, the general scheme of control system is made principle analysis, the feasibility of realizing fuzzy control, the principle of testing and computing the valid value of current adopting point-by-point integration and the rationality of choosing control parameter and the method of realizing spot welding nugget sizes artificial neural networks forecast are demonstrated. The input and output variables, fuzzy language variables, field, membership function that fuzzy controller deals with, determination of the fuzzy control rule, the methods of fuzzy reasoning, defuzzying and generation of the fuzzy control table are emphatically analyzed and simulation process and results of fuzzy controller are introduced. In addition, the methods of establishing spot welding nugget sizes model on the basis of ANN technology, the verifying result of established models and the way of nugget sizes forecast function realized on the single micro-computer system, relative assemble language program designing are systemically discussed.Secondly, the central controller (80C196KC single micro-computer) of the control system, the measuring circuit of current valid value and other hard-ware circuits that realize spot welding circling process and control are analyzed. The soft-wares of system main program adopting modularization designing method and subprogram of setting, prepressing, electrifying, interrupting and fuzzy control are generally introduced.Finally, the debugging and testing of control system in the spot are analyzed. The result manifests that the measuring the valid value of spot welding current of non-sine wave of the control system agrees with the one of Japan current meter MM-315( its precision is?%), the average different value is 59A. the regularity of spot welding constant current control is correct, the effect of constant current control is good.The phased achievement that the thesis makes has certain theory and project practical value for realizing the intelligentizing control of spot- welding process and quality.