Nonlinear interval model control of quasi-keyhole arc welding process

This paper addresses the development of a nonlinear model based interval model control system for the quasi-keyhole arc welding process, a novel arc welding process which has advantages over the laser welding process and conventional arc welding processes. The structure of the nonlinear model chosen was proposed based on an analysis of the quasi-keyhole process to be controlled. Because of the variations in the manufacturing conditions, the parameters of the nonlinear model are uncertain but bounded by 2xed intervals if the range of the manufacturing conditions is speci2ed. To determine the intervals, extreme operating conditions/parameters (manufacturing conditions) were used to conduct experiments. Each experiment gives a set of model parameters and the interval for each parameter is given by the minimum and maximum among the values obtained from di5erent experiments. Closed-loop control experiments have veri2ed the e5ectiveness of the developed system as a robust control which requires no re-adjustment and can function properly when 8uctuations/variations in manufacturing conditions, and thus the process dynamics, change, vary, or 8uctuate. ? 2003 Elsevier Ltd. All rights reserved.