Thermal modeling and adaptive control of scan welding

Abstract

This article introduces scan welding as a redesign of classical joining methods, employing automation technology to ensure the overall geometric, material and mechanical integrity of the joint. This is obtained by real-time control of the welding temperature field by a proper dynamic heat input distribution on the weld surface. This distribution is implemented in scan welding by a single torch, sweeping the joint surface by a controlled reciprocating motion, and power adjusted by feedback of infrared temperature measurements in-process. An off-line numerical simulation of the thermal field in scan welding is established, as well as a linearized multivariable model with real-time parameter identification. An adaptive thermal control scheme is thus implemented and validated - both computational ly and experimentally on a robotic plasma arc welding (PAW) station. The resulting thermal features related to the generated material structure and properties of the joint are finally analyzed in scan welding tests and simulations.