Abstract：The synchronous acquisition and analysis of information about arc shape and current variations during the polarity commutation process of variable polarity tungsten inert gas (VP-TIG) arc welding are helpful to understand the arc dynamics mechanism. However, the polarity commutation process is relatively short, which leads to higher accuracy requirements for synchronous acquisition of the current information and arc image, as well as the acquisition frequency and image resolution of the image acquisition equipment. In this paper, the synchronous input and output functions of a data acquisition board were related to the synchronous trigger of a high-speed camera to realize synchronization acquisition of the welding current and arc image during polarity commutation with the synchronization error controlled to within 2 μs. In addition, use of the difference between the trigger voltage pulse and variable polarity periods enabled approximately continuous observation of the arc images with a lower acquisition frequency and higher image resolution, which reduces the camera speed requirement. The observations of the welding arc changes with the current showed that the arc shape variation lags behind the current change during the polarity commutation process and arc extinction does not occur at or around the time when the current value passes zero. In addition, the arc with the lowest gray level appears in the current recovery stage after the polarity commutation process. The results indicate directions for further improving the arc burning stability of VP-TIG arc welding.
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