Autonomous Acquisition of Seam Coordinates for Arc Welding Robot Based on Visual Servoing

Abstract

Autonomous acquisition of seam coordinates is a key technology for developing advanced welding robot. This paper describes a position-based visual servo system for robotic seam tracking, which is able to autonomously acquire the seam coordinates of the planar butt joint in the robot base frame and plan the optimal camera angle before welding. A six-axis industrial robot is used in this system, which has an interface for communicating with the master computer. The developed visual sensor device is briefly presented that allows the charge-coupled device (CCD) cameras to rotate about the torch. A set of robust image processing algorithms are proposed so that no special requirements of light source are needed in this system. The feedback errors of this servo system are defined according to the characteristics of the seam image, and the robust tracking controller is developed. Both the image processing program and tracking control program run on the master computer. The experimental results on straight line seam and curve seam show that the accuracy of the seam coordinates acquired with this method is more adequate for high quality welding process.