Abstract: Aimed at submerged arc inner welding of spirally steel tubes, a visual sensor for automatic weld seam tracking system is developed. Visual camera is used as sensor, the image of the side obtuse edge is taken at three hundred millimeters front of welded point. Video signal is magnified, trimmed and processed into binary, the pulse waveform of obtuse edge is obtained. Based on vertical center in video signals, the deviation from direction is judged and the deviation value is estimated by computer on-slice, and the deviation signals in the form of pulse signals are transmitted to the drive of AC servo motor, the motor will control the movement of torch sliding platform, so as to ensure the welding wire to be directed at the weld in real time. Experiment results show that the method is feasible to identify obtuse edge with visual camera; a reliable system for real-time seam tracking to submerged arc inner welding of spirally steel tubes is developed. The response cycle of this system is less than 50 ms, and the tracking precision is ± 0.3 mm.

Key words: Automatic tracking, Spirally steel tubes, Submerged arc welding, Visual sensing