Abstract

This chapter designs a vision-based seam tracking system for butt joint of thin plate. Image-based visual control method is adopted due to its many merits. A key feature of this system is that it is compact and reliable. Smart camera is selected as the vision sensor and programmable logic controller (PLC) as the controller. Since the seam is so narrow, the visual measurement is based on natural lighting. To effectively extract the image features, “and” operation is proposed to eliminate the effect of splash of welding. Moreover, a new adaptive thresholding method is presented to segment the seam from the image, and combination of Hough transform and least square line fitting technique is used to extract the seam line. In terms of controller, a novel method is proposed to define reference and feedback image features to form a closed loop in image space. In addition, image error filtering and output pulse verification are added to the controller to improve the reliability. Finally, a series of experiments were conducted to verify the performance of the proposed seam tracking system.