The Digital Control System Research Of Waveform Controlling CO₂ Arc Welding Power Source Based On DSP

With the further application of microcomputer and DSP in the weldingfield, the precise control especially the wave controlled technic in newwelding machine exploits a mainstream method. In this paper, the new powersource for short circuiting transfer was researched and based on the technologyof DSP and wave control. In terms of the character of short circuit transfer ofCO₂ welding, the process was divided into seven subsections. At the beginninglower electric current with low voltage promoting dissolving pool forms thefirm short circuit bridge; then rising the current velocity cause the neck ofmetal coming into being. Then, the welding current is detracted, so as to makethe bridge braking at the low energy and finish the transfer without splash. Theshort circuit signal detecting circuit specially designed for judging the start andend of welding short circuit, and neck forming detecting circuit especiallydesigned for detecting setting value of du/dt, During the process, the real timecurrent and voltage values information are obtained with sensor and sent to theDSP for processing, then the wave of current and voltage was controlled bythe PWM of DSP'S EVA.This paper, based on analyzing of the reasons for splashing of CO₂welding, made discussing about short circuiting transfer controlling strategy.The semi bridge inverter IGBT type main circuit which have ability resistingno-balance was applied. Well designed hardware circuit can obtain all phase'sarc parameter of CO₂ welding process. According to PWM principle, IGBT ismade to works in a on-off statue with the high-speed and precise controlling ofDSP, out character voltage and current wave of the power source that comesup to every subsection of short circuit transfer of CO₂ welding was obtained.The digital control system takes TI company's TMS320LF2407 as thecontrolling CPU, some DSP'S special port and module such as XINT1,XINT2, PDPINTA and PDPINTB also including A/D,EVA module are used. Inorder to keep system's normal working, driving circuit, keyboard and displaycircuit,protecting and alarm circuit etc are all designed. Applying themoduling skills in software designing, except the main program, the interrupting vector table introduced,every function has its subprogram, so thehappening of interrupt will swift to corresponding subprogram. The hardwaredesign adopts Multisim 8 for circuit's simulating,this process can reduce thelose and save the time as well as optimize circuit function. In order to improvethe system stability, hardware and software synthesis measures are adopted forthe disturbance problem.After the analysis of every wave detected by oscilloscope, It can beconcluded that the project is workable for main circuit responding quickly,hardware are simple and stable,software with great stability and efficiency.