Multipass Seam Tracking Based On Vision Sensor

Most of the arc welding robots are utilized in the mode of teaching and play back, which can not adapt to the welding process for the thick plate structure. Because of the welding process of deep sheet has been influence by the power, we need to multi-path/multi-layer welding. We needed archive automatic deep sheet welding, in order to improve quality of welding process and flexibility of the welding robot, and seam tracking is an essential technique of automatic welding. Seam tracking system of multipass welding has been researched, based on laser vision sensor, and actuating mechanism which is consist of arc welding robot.It is very difficulty to gather clear and steady image in metal active-gas welding(MAG), owing to the noise interferences that exist in the nearby welding line caused by vast arc and spatter. This paper designed an appropriate dimmer system, which can wave length out of the range of650±10nm, the remains kept as light source.Accuracy and reliability of image processing algorithmic is very important, because of accurate identifying character of image and getting practice position information is the premise of seam tracking. This paper aim at difficulty of multi-path/multi-layer welding, brought forward a reasonable image processing flow. Develop a series of image process including middle value filtering, hardware image delousing, binary threshold segmentation, upedge searching, straight-line fitting, we successfully distil position information of character, making foundation for offset calculate, and ensure the Real-time.Based on the accurately extracting welding deviation information, it brought forward Fuzzy-P control method including Fuzzy control technology and the convenient Proportional control technology. When the deviation is big, the Proportional control is applied which can improve the response speed of tracking system and accelerate the respond process; when the deviation is small, Fuzzy technology is applied which can achieve small error.The seam tracking system of multipass welding, which is designed on Visual C++6.0, under Windows XP environment. It includes image gathering, image processing and seam tracking. In order to improve the accuracy, we use multi-thread technology.To validate the system performance, we use V-grooved joint of multipass on the flat plates(700mm×150mm×20mm), experiment to different shape and offset on rendering layer, filling layer, cover layer, the tracking accuracy is±0.3mm.