Automatic weld seam tracking of tube-to-tubesheet TIG welding robot with multiple sensors

Welding height and welding distance were the two important parameters for tube-to-tubesheet welding. This paper introduced an automatic tube-to-tubesheet TIG welding robot. The center of tube was extracted by a vision sensor. The arc voltage between the tungsten electrode and the tubesheet was monitored by a voltage convertor. The initial welding height was measured by a laser sensor. The optimal image recognition algorithm was selected through comparative experiments. The experiment showed that the calculation error of tube center can be controlled within 0.2 mm. The tube center can be accurately aligned with the rotary center of welding torch by the robot. Thus, the distance between the tungsten electrode and the tube can be ensured to meet the process requirements, namely welding distance consistency. Arc voltage tracking was realized after arc voltage acqui-sition, peak extraction and arc voltage threshold control. This can regulate the welding torch move towards or away from the tubesheet, namely real-time control of the welding height. The voltage fluctuation can be reduced from 1.84 V to 1.15 V by arc voltage tracking, which was beneficial for welding robot to obtain better weld seam.