Multivariable adaptive control of the bead profile geometry in gas metal arc welding with thermal scanning

This research implements the newly introduced scan welding technique in processes with material deposition. A laboratory station is developed with robotic plasma-arc welding under infrared pyrometry sensing for thermal scanning, and with gas metal arc welding under laser profilometry feedback for material transfer. The dynamics of the weld profile geometry (i.e. the bead width and reinforcement height) are modeled experimentally with respect to the process conditions (weld speed and wire feed). This model serves as the basis for the development of a simple geometry feedback control scheme. A multivariable adaptive control system, based on a generalized one step ahead regulation algorithm is also established and validated experimentally. Application of such bead profile regulation is explored in multipass weld joining, orbital welding, coating hardfacing and rapid manufacturing methods. (C) 2002 Elsevier Science Ltd. All rights reserved.