Monitoring weld pool oscillation using reflected laser pattern in gas tungsten arc welding

A single laser vision method was proposed to carry out real-time sensing of the oscillation signal from the reflected laser pattern. A robust algorithm based on the image centroid of reflected laser pattern was developed to extract the oscillation frequency of weld pool and fluctuation amplitude of centroids of laser pattern Delta H-cen. The correlation between fluctuation amplitude of centroids of laser pattern Delta H-cen and oscillation amplitude of weld pool surface Delta h(act) were simulated based on the law of reflection. Several experiments were conducted in stationary and traveling welding processes with different penetration status. The oscillation frequency and Delta H-cen were extracted. An abrupt transition mode of oscillation frequency and Delta h(act) exists from partial to full penetration status in stationary welding process. By contrast, an abrupt transition occurs in zlhact in the case of traveling welding process. Two transition modes of oscillation frequency, continuous and abrupt change mode, occurred with different welding speeds, which correlated with the oscillation behavior of weld pool surface.