FRONT IMAGE SENSING OF THE KEYHOLE PUDDLE IN THE VARIABLE POLARITY PAW OF ALUMINUM-ALLOYS

The front image sensing of the keyhole puddle invariable polarity plas ma are welding of aluminum alloys has been investigated in this paper, to extract the characteristically geometrical size of the keyhole and to realize the feedback control for weld formation in the welding pro cess. The results show that the approach of composite are light filter ing with narrow-band spectrum can be applied to take the image of the keyhole puddle of aluminum alloys. The reason for the image formation of the keyhole puddle is that the highly depressed keyhole puddle can be used as a convex mirror-like surface to reflect the light of a brig ht are cone. The image of the visible keyhole is a composite picture o f the spatial pattern of the keyhole puddle. The geometrical sizes of the visible keyhole in the image, such as the area, the width, etc. ca n be used to monitor both the keyhole puddle and the weld formation in the welding process. The algorithm for the image processing of the vi sible keyhole puddle and the periphery extracting of the visible keyho le developed in the paper can be used to determine the geometrical siz es of the visible keyhole under the condition of an off-line welding p rocess. (C) 1998 Elsevier Science S.A. All rights reserved.