Experimental Vision Based Robot System for Arc Welding

Abstract

An experimental visual seam tracking system for robotic arc welding has been developed. A visual sensor was constructed and mounted on the welding head of a robot. The sensor was interfaced with a microcomputer and the micro-computer was interfaced with the robot's control unit. Software was made for image processing and controlling the path of the robotduring welding inreal-time. The welding robot is a Unimation Puma 560 robot. The operating system is VAL II, which allows receiving path control information from an external computer through a serial link. The robot basically follows a preprogrammed path and corrections to the path are transferred at intervals of 28 ms to the robot. The communication is carried out by its own processor. The groove measurement system uses structured HeNe-laser light and the triangulation principle for the determination of the groove position and profile close to the arc. Fibre optics have been used for transferring laser light to the sensor head and image to the camera. Welding tests have been carried out for square butt and single V preparations, but the system has been designed to be applicable for fillet welds too. The seam tracking accuracy has been found to be about ± 0.5 mm in the horizontal plane and ± 1 mm in the vertical plane. The system is able to adapt to surfaces of different brightness. The image processing is performed in the 16-bit microcomputer. An image processing speed of 8 images per second has been reached.