2001 Volume 19 Issue 2 Pages 287-298
As is generally known, arc sensors do not require special sensor elements, and feature a number of practical advantages such as welding current/voltage-based detection of deviation in torch aiming from the groove center. However, conventional arc sensors suffer from erroneous detection in cases where gap width within the groove is uneven, making it impossible to detect deviation in torch aiming. This paper describes the application of a high frequency oscillation arc (developed by the authors) to the development of a new type of arc sensor capable of detecting torch aiming deviation regardless of the gap width within the groove, as well as allowing detection of gap width itself. First, based on quantitative analysis, consideration was given to the arc characteristics of the high frequency oscillation arc in comparison with conventional sin curve oscillation. Then, arc sensor principles for simultaneous detection of torch aiming deviation and gap width were elucidated. The results obtained are as follows.
1) The welding current and voltage characteristics of the high frequency oscillation arc feature the coexistence of a dynamic state in which self-regulation of the arc does not function, and a static state governed by self-regulation effects.
2) Frequency characteristics have been revealed for welding current/voltage amplitude with respect to the high frequency oscillation arc for welding in V-type joint grooves. The low frequency range of welding current amplitude tends to decline steadily with increases in the maximum frequency, and no critical frequency phenomenon is displayed in sin curve oscillation. Welding voltage amplitude is virtually constant with respect to frequency, and there is no frequency dependence.
3) Quantitative analysis illustrates arc sensor principles for the simultaneous detection of deviation in torch aiming and gap width using the high frequency oscillation arc.
4) In feedback control of an actual welding robot system equipped with the arc sensor, the gap width was successfully detected during seam tracking with a maximum gap of 3.5 mm.
