A compact sensor for welding process control

The purpose of vision based sensing devices in the welding industry is to electronically replicate the role of a skilled welder, and emulate the human eye with a light sensing device such as camera and the human brain with a computer algorithm that interprets the images. Just as optical feedback from human eye guides the human welder, optical feed back in this electronic system would be used to control a mechanical welding system, in the case of this research, a Gas Tungsten Arc Welding (GTAW) system, in order to control the quality of the weld. Such sensing systems have been developed, but our purpose is to build one using more commonly available elements and on a much smaller scale, as to be able to attach it to an already-existing welding system without imposing dramatic space requirements on the system. Building a system to replicate the function of a human welder requires research into optics, specifically charge-coupled devices (CCDs) and lenses. This paper discusses the procedure employed in developing the knowledge base and the experimental system used for building this compact sensor. Experiments have been performed to determine the positioning of the lens, its focal length, and size. A study of the illuminating system is also documented to understand how light is dispersed under welding environment. The illumination system is based on structured laser light, where a laser line is projected on the weld pool. The weld pool is divided into three parts, the front (deepest), middle and back(shallow). Experiments are performed to determine the position where the laser light needs to hit the weld pool and how it is reflected from various points of the weld pool.