自适应恒频短路过渡焊接过程的控制系统

Adaptive Control System for Short-circuiting Arc Welding with Fixed-frequency Metal Transfer

短路过渡焊接时，熔滴过渡频率通常被作为评价焊接过程稳定性及焊接质量的重要指标。本文首先根据短路阶段电源输出电阻的变化曲线，确定了有利于消除瞬时短路及提高熔滴过渡规则性的短路过渡焊接控制电流波形。其次鉴于干伸长电阻热对过渡频率的影响，提出了通过短路过渡中期电源输出阻抗实时检测焊丝干伸长，采用干伸长变化前馈补偿干伸长电阻热对过渡频率影响的方法。最后利用ＭＣ６８ＨＣ１１Ａ１ 单片机建立了焊丝干伸长变化前馈—过渡周期负反馈恒频短路过渡控制系统。试验表明，恒定频率的短路过渡焊接飞溅小，焊接过程稳定，焊缝质量良好，且改变目标过渡频率可以控制熔滴尺寸及焊缝成形。

Metal transfer frequency are usually taken as the criteria to evaluate the process stability of short-circuiting arc welding. In this paper, the time dependency of the output impedance of the power source during the short-circuit period is analyzed at first, afterwards a current waveform for short-circuiting arc welding was proposed with the aim of eliminating instantaneous short circuit and improving the process regularity. Considering that the Ohm heat on electrode wire extension (EE) plays an important role in the wire fusion, a new method of EE real-time detection and EE variation feedfoward is developed. Finally, the paper presents a fixed-frequency short-circuiting metal transfer control system based on microprocessor MC68HC11A1, which incorporates EE variation feedfoward and transfer frequency feedback. Practice welding shows that the expected transfer frequency and the resultant process characteristics are achieved successfully.