Method and apparatus for automatically controlling arc welding

An apparatus for automatically controlling arc welding comprising:

• optical means for alternately picking up pieces of optical information provided by at least two bands of different wavelengths of light radiated from a weld area being arc-welded by a welding unit controlled according to predetermined welding conditions;
• means for extracting the weld factors representing the actual status of the weld area from said optical information picked up by said optical means with said weld factors including at least one of the shape of the groove, the physical position of the weld torch, the height of the lower end of the weld torch from the molten pool, the shape of the molten pool, and the shape of the arc;
• means for comparing said extracted weld factors representing the actual status of the weld area with the desired values of the weld factors representing the desired status of the weld area to compute the error or errors of the welding conditions;
• and
• means for correcting the welding conditions of said welding unit on the basis of said detected error or errors of the welding conditions, whereby said weld factors can be controlled to their desired values.

A method for automatically controlling arc welding, comprising simultaneously conducting the steps of:

• arc welding metal and producing a molten metal weld pool;
• picking up, by optical means, pieces of optical information provided by at least one band of different wavelengths of light radiated from said molten pool, the different wavelengths presenting different information, being arc-welded under predetermined welding conditions;
• extracting at least one weld factor representing the actual status of the weld area from said optical information, with said one weld factor being the physical shape of the molten pool;
• comparing said extracted weld factor representing the actual status of the molten pool with the fixed desired value of the weld factor representing the desired status of the weld area and computing the error of the welding conditions;
• correcting the welding conditions on the basis of said detected and computed error of the welding conditions, to change said weld factor to its desired value while said arc welding step is still being performed on the molten pool being detected, said controlled welding conditions including at least one of the welding current, the arc voltage, the weld speed, the horizontal (Y-axis) position of the weld torch, and the vertical axis (Z-axis) position of the weld torch;
• and
• said pieces of optical information being provided at least by a first wavelength range of 0.5 .mu.m to 0.6 .mu.m and a second wavelength range higher than 1.0 .mu.m.