Abstract: Considering the particular feature of short circuiting CO2 arc welding process, the output current waveform of welding power source is determined based on the characteristic of the output loop resistance during the period of droplet short circuiting with weld pool. The current waveform is in favor of eliminating the instantaneous contact of droplet with weld pool and enhancing the regularity of droplet transfer. An adaptive control system with constant frequency of droplet transfer is established after the droplet transfer frequency and the wire extension being detected in the real time. The control system is aimed at improving the stability of welding process which is realized by the feedback control of transfer frequency, and restraining the disturbance inducing by the variation of wire extension which is compensated through its feedforward. The basis of the system is an inverter type are welding power source controlling by a microcomputer MC68HC11A1.

Key words: Adaptive control with constant frequency, Detect and compensate of wire extension, Short circuiting CO2 welding, Waveform control