Study On Arc Length Automatic Control Of Tig Welding

Since twenty-first Century,quality control and quality assurance of welding products have become one of the key problems in the welding manufacturing technology.The new hybrid TIG welding technology not only retains the common advantages of TIG welding,but also breaks through the limitations of traditional TIG welding.The new hybrid TIG welding technology has the advantages of high quality and high welding speed and has wide application prospect.The stability of arc length in TIG welding process has a direct effect on the quality of welding,so it is necessary to introduce TIG arc length automatic control system to ensure the welding quality.In this paper,based on the investigation of the automatic control technology and the design scheme of the mainstream TIG arc length,the disadvantages of the existing TIG arc length control system are analyzed,such as single function,complex structure,low degree of automation,high cost and so on.A new AC/DC and pulse TIG arc length automatic control system based on digital PID is proposed:The system use arc voltage as arc length signal and the step motor subdivision drive is adopted to improve the control accuracy.the MCU is also used as the control core to enhance the flexibility of the system.In the design of the system hardware circuit,based on the consideration of the adaptability of the system to the high frequency arc starting,the high voltage pulse starting arc and the high voltage pulse arc stabilization and the compatibility of the AC and DC TIG welding,the signal selection circuit,the arc voltage acquisition and processing circuit,the SCM control system,the liquid crystal display circuit,the subdivided driving circuit and the position detection circuit are designed.The design and selection of the stepping motor and moving mechanism of the welding torch adjusting mechanism are also presented.According to the modular program,AD transformation,extreme value filter signal processing control algorithm,LCD display,control signal generation and other functional subroutine is programmed by C language to realize the basic function of arc length automatic control.The TIG welding arc length control test platform is built,the arc length tracking control experiment is designed,and the system parameters are obtained through the trial and error method.Results shows:variable integral PID control algorithm applied to TIG welding arc length automatic control can significantly improve the system response speed and control accuracy and has a better application prospect.