A Study Of Wave-control CO₂ Welding Inverter's Control System Based On Digital Signal Processor

With the further application of advanced technology in the welding field, the research of digital technology and wave controlled technology in new welding machine have been exploited two mainstream directions. In this paper, the control system of the power source for CO₂ short circuiting transfer is researched which is based on the technology of STT (the Surface tension transformation) and DSP (digital signal process). In terms of the character of short circuit transfer of CO₂ welding, the process is fractionalized into seven subsections. During the neck of metal becoming, rising the current make it coming into being. And at the later of short-circuiting transfer, the welding current is declined, as makes the bridge destroyed at the low energy and finishes the transfer without splash. During the process, the real time current and voltage values information are obtained and sent to the DSP (digital signal processor) for processing, then the wave of current is produced by the control of DSP at the output end that is suit for the short-circuiting transfer. The problem of the accurate capture and estimate of each subsection's characteristic signal is a bottleneck in the development of the Surface tension transformation. With the development of detecting technology in welding process, it has been known that welding current and arc voltage carry about abundance information of various arc physics phenomena. This paper designs a welding arc information testing and processing system based on data acquisition card PCL₈18L, which can deal with data acquisition and signal analysis processing in Visual C++. The system has a friend by interface and is very easy to use. It contains instantaneous I-U, differential analysis, welding voltage and current probability density distribution diagram, arc power, metal transfer frequency distribution diagram and the time of metal transfer period etc. Instantaneous I-U diagram can be used to find the irregular metal transfer. Welding voltage probability density distribution diagram, the variance of metal transfer period and metal transfer frequency distribution diagram can be used to judge the stability and the regularity of metal transfer. By these functions, the arc character of the CO2 droplet transfer welding process can be analyzed so as to extract more valuable information. In this paper, basing on the welding arc information testing and processing system, the control project of short-circuiting transfer is probed and two control projects are obtained. One is that at the time of day of short circuit, arc and other subsections, the arc values are exactly checked in real time and processed by DSP, then, initializing the time constant of per subsection so as to realize the control. The other is that at the time of day of short circuit, arc and other subsections, the arc values and the welding current are exactly checked in real time and processed by DSP. The out character of the power source that comes up to every subsection of short circuit transfer of CO2 welding is obtained. In software technology, interrupting service technology is used, which can disposal every kind of malfunction in time and real time control. The structure of software adopts the subroutine thinking which is in focus and easy to debug and modify and improve the system stability and replantation. The estimation system of experimentation, which can estimate the effect of DSP control in CO2 welding, is designed in the paper. The pretreatments of welding current and arc voltage, which is good linearity and sensitive to inspect welding current and arc voltage so as to insure that welding current and arc voltage are not distortion before they enter the A/D of data acquisition card and DSP, are also designed in the paper. The hardware and software have been tested in simulated conditions, and it is proved that the overall plan and control idea is original and available through simulation tests and welding tests. It is a sort of new beneficial attempt for the research of waveform controlled CO2 arc-welding power.