Development Of Tracking Technology Based On Laser Vision In High-Speed Welding Of Aluminum Alloy

With regard to problems that the heavy interferences in welding process, and deviation in tracking of curvatures,system can' meet the requirements of high-speed welding, image processing and intelligent control were studied. The conflicts between the accuracy and real-time of image processing was worked out,and the system could achieve real-time within all curves of a certain curvature, in which foundation the high speed welding will be realized.To improve the visual sensing devices which based on structured light,980nm wavelength semiconductor laser diode,980nm narrow band passing-filter and 1% cutting-filter were choosed to make up the laser vision sensor, then clear images of the joint were obtained and the reflection of light on the Aluminum alloys, spatters and arc interferences in the process of welding were eliminated. The new system had good flexibility and opened the way to the subsequent image processing.The Images of common material in different welding process were studied and classified, and the images with two kind of noise which matched different image process were analyzed. Then the initialization interface of seam tracking was figured out, from which the system integrated the critical information and derived the optimal system processing and control flow,In order to make the image processing both real-time and accuracy, several important processing algorithms were optimized, for example, median filtering, mean filter, two-dimensional otsu threshold segmentation. Then based on multi-threaded processing, the traditional process was seperated into one main thread and two subordinate thread,which improved the using of CPU and at the same time made the entire process faster,At last the entire process costed less than 40ms which met the requirements of real-time control.The transfer function of the system was established, and simulation based on Fuzzy-PID,P and fuzzy control to supervise parameters of PID (P-FPID)sub-section control were conducted with Simulink software.The results showed that the accuracy and response speed of the latter control were better, so fuzzy control to supervise parameters of PID control was more effective than the fuzzy control alone.Finally, to verify the performance of image processing and control system had been improved, real-time tracking test of aluminum alloys of diagonal and curved joints was carried out. As a result, the maximum deviation existed in 1mm when the welding speed was in 0.9m/min～1.2m/min and the slope of joints were in the 10°～20°,and the deviation existed in 0.7 mm when the welding speed was 0.6m/min in tracking the curve seam.