This study describes real-time monitoring of the arc state during variation of a beat input demanded to control the $CO_2$ arc welding process. The arc state is one of the major factors to effect to the soundness of weld bead and is affected by the welding condition, shielding gas, characteristics of a welding power source and the variation of the feeding speed of a electrode wire.
In this paper, new index to reflect the arc state is proposed through waveform analysis and the power source modeling. The index is a standard deviation of arc frequency, which means the amount of the uniformity of the arc voltage waveform.
For real-time monitoring of the arc state, the index is calculated recursively. Through the welding experiments, the arc state in accordance with several welding conditions was well monitored quantitatively.
