1987 Volume 5 Issue 3 Pages 304-311
It is important as a basis of research in automatic arc welding to control the weld pool shape against the disturbance and the variation of system parameters. For this purpose it is useful to control the weld pool width. A basic visual robot is proposed for observing and controlling the weld pool shape by using the pulsed current.
It has been difficult to observe the weld pool with a TV camera, since the arc light is too strong to watch the molten metal under the arc. The authors tried to make periodically the current low enough to watch clearly the weld pool with CCD (Charge coupled device) camera without after image.
The weld pool is recognized by taking advantage of the feature on the brightness of the weld pool and its outskirts. A personal computer calculates the weld pool width and area in real time. The authors study the transient response of the weld pool width and area.
The welding current is determined to get a desired response of the weld pool. It is shown how to determine the digital controller characteristic. Small variations of system parameter during operation caused by the change in the base metal thickness, heat conductivity, temperature rise are allowed while the prescribed control performance is maintained.
Experiments demonstrate the good controllability of the adjustable weld pool formation with the digital controller.