Abstract: The weld seam tracking and the welding torch height are controlled, the waveform of the welding voltage or the welding current of the arc is detected, the waveform of the above-described welding voltage or welding current under an appropriate welding condition to a reference gap G.sub.ref is stored as a reference waveform, the area .vertline..DELTA.SG.vertline. of a deviation part of the detected waveform to the above-described reference waveform is obtained, .DELTA.SG is obtained by judging the positive and negative of .vertline..DELTA.SG.vertline., the relationship between the value of .DELTA.SG and the root gap G is experimentally determined in advance, and the root gap G is calculated from the value of .DELTA.SG.

Abstract: An apparatus for detecting a shape of a groove, comprises: a device for forming picture images of a groove and a groove face of a work piece of metal to be welded with the use of a welding arc as illuminating light; a storage device for storing information on picture elements of the picture images formed by the device for forming picture images; an integrating device for integrating the information of the picture elements stored in the storage device in a predetermined direction of a memory in the storage device; a differentiating device for differentiating the integrated information in the direction rectangular to the predetermined direction of the memory; and a detecting device for detecting information of shapes of the groove and the groove face on the basis of the differentiated information on the picture elements.

Abstract: An apparatus for automatically welding a cylindrical vessel, which comprises: a rotating means (8) for rotating a cylindrical vessel to be welded around the center axis thereof; a travelling carriage (1); a manipulator (2) mounted on the carriage (1), said manipulator comprising a vertical post (10) secured onto the carriage (1), a horizontal column (11) movable horizontally and vertically along the vertical post (10), and an expansion arm (12) fitted rotatably to the leading end of the horizontal column (11); a welding head (4) fitted through an L-shaped fitting member (3) to the tip of the arm (12), said welding head comprising a welding nozzle (16), a groove profiling means (17) and a groove shooting means (20); a welding wire feeder (5) mounted on the carriage (1); a welding electric power source (6) mounted on the carriage (1); and a welding controller (9) mounted on the carriage (1), said welding controller comprising an image processor (32), a welding current controller (33), a welding wire feed contro