Online welding path detection in automatic tube-to-tubesheet welding using passive vision

A passive vision system based on image processing technology for automatic welding system is researched in order to enhance the efficiency for the tube-to-tubesheet welding of heat exchanger in this paper. To this end, the detection and extraction methods of the welding path are studied in tubesheet welding through the passive vision system. A calibration procedure is proposed for the vision system, and the positional relationships between the cameras and the robot are obtained. The Hough transform is used to extract the tubes’ position roughly through a camera that is fixed above the workpiece, and another camera is used to extract the feature of the tubes accurately one by one. A multiple iteration method of least squares is also proposed in this paper to remove the background noises. The edge of the inside tube circle is accurately extracted, and the welding path is obtained. Validation experiments are finally conducted to confirm the reliability and accuracy of this method.