Research Of The Digital Control System Based On DSP For CO₂Welding

With the processing development of the power electronic technology, the modern centralcontrol technology and digital signal technology have the realization of the full-digital controlsystem for welding inverter possible. Because of the advantages such as the more flexible, thehigher control precision and a better stability, also easier to realize theflexible controller, full-digital control system is the development aim of welding inverterpower source. Therefore, this paper study digital control system of the CO₂welding inverterpower source, introduce the full-digital control technology which based on DSP and CPLD,through the way of digital control, we can meet the need of CO₂welding inverter applications,improve the performance of the welding inverter.This paper combine the current digital signal technology DSP and the latest study resultof the embedded system, choose DSP TMS320F2812, CPLD EPM240T100C5and AT89S55,DSP TMS320F28016to design a full-digital control system for CO₂welding and establish aplatform of the research of welding digital control system. Among them, DSP TMS320F2812is a center control in charge of the whole management of the power. CPLD EPM240T100C5is in charge of digital PWM, digital protection and filter functions. The MCU AT89S55isresponsible for the control of the man-machine interaction system. TMS320F28016is incharge of control the wire feeding speed. The communication between the MCU and DSPTMS320F2812and between TMS320F2812and TMS320F28016is established by RS485protocols using the SN75179to complete the data interaction.After accomplished the testing and adjusting of soft and circuit, the CO₂welding inverterdigital control system could achieve these functions:（1） the PWM circuit which we used theDSP TMS320F2812and the CPLD EPM240T100C5achieved digital PWM, digital guardcircuit and digital filter circuit. Using the voltage-current feedback system to control and thesoft ware PI to control the algorithm, we achieved accuracy controlling the welding process.（2） We used the DSP TMS320F28016to make the wire feedback control system, used thelight code dish to let the wire speed feedback so that we could enhance the stability andconsistency of the wire speed.（3） We used the MCU to build the man-machine interfacesystem to achieve welding parameters adjustment, real-time display and real-timecommunication. What’s more, it can achieve storing parameters, calls and power failsafeguard, too.We can conclude from these experiments that the CO₂welding inverter power supply control system, which we discussed in this paper, is able to control the process of waveformsprecisely and constantly, and the wire speed is stable and the man-machine interaction isflexible and humanized and meet the design requirements. They would make a foundground for the subsequent of CO₂welding procedure.