Development Of Welding Seam Location System Using Laser-vision

Welding technology plays an important role in modern industry. However harsh working environment, extreme physical demands on manual welder and increasing request in quality of welding have made it to be one of the greatest demands for automation. Welding seam location technology is the key issue to solve the problem. And Laser-Vision welding seam location technology with the advantages of high precision, high speed and full digital measurement is the most advanced one, which has been widely studied and applied.A laser-vision based welding seam location system for welding robot is developed in this paper. The system consists of a CCD camera, a line structure laser, a narrowband optical filter to overcome the interference from arc light and other light sources, and an embedded computer board for image processing and error calculation. By making use of optical triangulation measurement method, the welding seam positions of cross direction and vertical direction can be measured from the feature points' positions of the welding seam in captured images. Advanced image processing algorithms are developed and implemented on the embedded computer board to process the images captured by the camera. Laser stripe region is defined from the entire image, and the effects of bright spots on the images caused by spatters and reflection are eliminated by area-size filtering algorithm. In order to detect the feature points, an algorithm based on the second centre differences of the column indexes of the pixels on the laser stripe is implemented. The software developed on embedded Linux system can capture the image from camera, process the image by using OpenCV library, and display the results on the touch screen. System parameters can be also set through the touch screen.Experimental results show that the measurement errors in cross direction and vertical direction are within the range of 0.5mm and 1.0mm respectively, which can meet the demands of accuracy for welding seam location. The processing speed of the system can reach 16 points per second, which can meet the demands of speed for welding robot.