| In the actual welding process, a variety of uncertain interference factors are existed. And the seam position and size are disturbed by such as the workpiece assembly error and the deformation caused from the thermal stress in the welding process, which makes the deviation between welding trajectory and welding seam, then will affect the quality of welding formation. Therefore, the capability of detecting trajectory deviation and adjusting the welding path in real-time is in demand. The research on the seam tracking has a significant influence on improving the welding automation level. The GTAW seam tracking technology based on the composite sensors for thin plate butt seam was studied in this paper.The passive vision sensor system was designed. Through test and analysis, the clear and stable welding image was obtained by adopting an appropriate composted filter system. A set of complete image process algorithm was proposed according to the obtained image. And the center of the tungsten electrode and seam centerline location information were extracted effectively. The arc voltage signal was acquired by using the designed arc sensor. The anti-pulse interference sliding average method was studied to eliminate the noise on the influence of arc voltage signal in welding process. On this basis, the relation model between arc voltage and arc length was established. The more reliable and more comprehensive welding seam shape information was obtained by using the designed composite sensors. The horizontal and vertical position deviation was extracted effectively, which laid a foundation for the three-dimensional seam position tracking. In addition, the welding seam pose tracking of walking angel was studied by computing the welding path point location and welding torch posture information with the composite sensing system. Welding seam modeling method was proposed to extract the deviation of welding torch gesture.On the basis of accurately extracting deviation information, Fuzzy-P dual mode controller was designed. Within the scope of big deviation, the proportional controller was using to improve the response speed. And within the scope of small deviation, the fuzzy controller was chosen. The results of MATLAB simulation test show that the Fuzzy-P controller has advantages of good reliability and tracking ability, which meet the requirements of GTAW seam tracking system.The seam tracking system software was developed with the Visual C++ multithreading technology under Windows XP platform. The system software included a main thread and three child threads, the main thread was responsible for the system hardware initialization, the child threads were responsible for image acquisition and processing, arc signal acquisition and processing and the extraction of torch walking angel deviation respectively.In order to verify the reliability of system, some experiments were done by using the designed GTAW seam tracking system for thin plate butt seam. The results show that the precision of the three-dimensional position tracking can be controlled within ±0.4mm. Since the pose tracking is still on the exploration stage, the further research should be done for improving the precision of pose tracking. |
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