Inverter Welding Power Adaptive Fuzzy Control Technology

In recent years, with the development of chinese steel industry, the demands for the welding machine called steel sewing machine are increasing rapidly, The requirements for welding quality is also strengthened increasingly. Digital welding machine which is famous for small size, light weight, high efficiency, and flexibility of controlling method have gradually become the mainstream, however, most control methods are simple PID control, so the control performance is not good enough. In this paper, adaptive fuzzy PID control method is proposed, which combined fuzzy reasoning with classical PID control theory, and determined the three PID control parameters with artificial intelligence. Experimental results show this method is correct and effective.(1) The hardware circuit of inverter welding power source system is designed. Over voltage circuit, under voltage circuit, over-current, and overheating circuit are designed respectively. TMS320LF2407A (DSP) digital signal processing chip is used as the hardcore of the control ciecuit. Then designed the peripheral circuits including DSP-powered circuit, clock circuit, the signal acquisition circuit, JTAG emulation circuit, reset circuit, LCD display and keyboard input circuit.(2) The fuzzy adaptive PID control algorithm is studied. To meet the requirement of the welding rod on the power output and dynamic characteristics, combining the the fuzzy control and classic PID control, the fuzzy-PID controller is designed. The simulation models about the main circuit, the fuzzy controller and PWM controller are built with MATLAB/SIMULINK toolbox. Then the designed controller is verified by the simulation models.(3) The softwares of control system are designed. To reflect the features of the welding machine on digital, easy operation and visibility, the programs about the AD sample, PWM generater, LCD display keyboard input and fuzzy adaptive PID control algorithm are designed. Fuzzy adaptive PID control Principles and the implement of the programs are expounded in depth.(4) Simulation and experiment are studied. The simulations when no-load to load and the load changes are researched respectively, then compared with the normal PID control's simulation results. Fixed resistor load and on-site welding are studied respectively, the feasibility of fuzzy adaptive PID algorithm is verified by the steady state and transient's study. No-load-short circuit-welding-short circuit-welding process can be simulated by simulation model, the comparison of experimental waveform and simulation waveform, shows the control methods are correct and effective.