中文摘要：

研制基于单片机控制的具有高低频调制脉冲功能的双逆变变极性等离子弧（Variable polarity plasma arc，VPPA）焊接系统，检测并分析叠加不同高低频脉冲参数条件下该焊接系统输出信号的特征，并对系统进行实际焊接试验，结果表明系统运行良好。从特征信号的时域及频域分析发现，当高频脉冲频率提高到2 kHz时，与1 kHz相比较，脉冲上下降沿斜率降低1.2倍，高次谐波量增加1.4倍。由焊接试验结果得出，当高频脉冲频率及正反极性电流等工艺参数选择合适时，可以得到比典型VPPA焊接更加优越的焊缝成形，获得具有均匀鱼鳞纹的理想焊缝。从焊缝显微组织的分析发现，脉冲VPPA焊接工艺得到的焊缝晶粒比典型VPPA焊缝晶粒细小，因此该焊接工艺对进一步提高航空航天高强铝合金焊接质量具有重要意义。

英文摘要：

A double-inverter variable polarity plasma arc（VPPA） welding system with high-low frequency modulation, controlled by single chip microcomputer is introduced and its characteristics of output signal with different conditions of adding high-low frequency pulse are tested and analyzed. Its welding test is performed and the results show the system runs well. It is analyzed from the time and frequency domain of the characteristic signals that compare with 1 kHz, when pulse frequency increases to 2 kHz the slope of pulse reduces 1.2 times and higher harmonic increases 1.4 times. The welding experiment results show that it can get better welding gap than typical VPPA welding and obtain uniform ripple welding line when process parameters including high frequency pulse, positive and negative polarity currents etc. are chosen appropriately. After examination of the weld microstructure, it is found that the pulse VPPA could obtain finer weld grains than typical VPPA. Because of improving quality of welding, the welding procedure is significant for high-intensity Al-alloy welding in aerospace.