| Welding automation is one of the solutions to solve the problems of traditional manual welding such as labor cost, product quality, safety and health issues. The welding robot technology is one of the highest degree of automation and the most complicated technologies in welding automation technology.Stability of welding arc length have an important impact in welding seam quality and uniformity of molten pool depth. In this dissertation, in order to improve dynamic stability of arc length in the robot welding process, closed loop arc length control system was designed and some control algorithms was studied.Firstly, some important arc characteristics of robot welding were elaborated, such as melting drop transition and arc property. On this basis, the principle of arc length control system was analyzed. Secondly, the model of welding robot arc length control system was established based on modular modeling. The model simulated in Matlab/Simulink can be used to analyze the parameter fluctuations of welding and the wire feed speed variation curve which maintain the stability of arc length. By the means of model simulating, PID control algorithm and gain scheduling fuzzy PID control algorithm were researched. Furthermore, control parameters of the both control algorithms were optimized by generic algorithm. Finally, the closed-loop arc length control system was designed, and the control algorithms were tested by this system.In the experiment, comparison and analysis of the arc voltage which can characterized the arc length can draw conclusion that gain scheduling fuzzy PID control algorithm better than traditional PID control algorithm in arc length control, because of its control parameters can be adjusted online. What’s more, there is a certain reference function in molten depth intelligent control of robot welding by the modeling and the research of control algorithm in this dissertation. |
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