A strategy for oflline programming and adaptive control of a robotic welding cell

Abstract

Offline programming for arc welding applications has not yet been widely adopted by the industry owing to a series of factors, which include absolute accuracy of the robots, calibration of the workcell, fixturing, parts tolerances, joint fit up errors, varying gap size, and online joint movement due to thermal distortion. The presence of some or all of these factors may lead to poor quality weld beads, which can cause undesirable product rejections. In order to deal with these problems, an offline programming interface, which includes the generation of the welding parameters, and a control strategy are presented. This paper discusses each source of error, classifying them into three categories, namely robot discrepancies, programming errors, and component errors. Based on this classification, corrective actions for the first two categories and an adaptive control strategy for controlling the component errors are proposed.