【作者】 曾军辉；

【导师】 卢振洋； 黄鹏飞；

【作者基本信息】 北京工业大学 ， 机械电子工程， 2008， 硕士

【摘要】 变极性PMIG(简称VP PMIG)焊是一种交流脉冲熔化极焊接方法,可用于焊接铝合金、低碳钢以及不锈钢,它的优势是可以通过调整EN极性占整个变极性脉冲电流周期的比例(简称EN比率),实现对焊接电弧能量的控制,从而达到对焊缝熔深、送丝速度的控制,非常适合于薄板铝和金焊接,并且可以获得很高的焊接效率。根据薄板铝合金焊接工艺要求,在基于DSP控制的VP PMIG焊接设备结构的基础上,设计了逆变焊接电源数字化控制系统,完善了该焊接设备,系统工作过程稳定、控制精度高。焊接电源主电路采用IGBT二次逆变技术实现变极性焊接电流的输出,内环电流反馈实现焊接电流的恒流控制,外环电压反馈通过控制电弧电压实现电弧弧长的调节。针对铝合金VP PMIG焊接电流过零后存在电弧再引燃问题,采用单电源供电方式,设计了一种全桥式高压脉冲稳弧电路,可实现小基值电流过零时的双向稳弧,保证了焊接电流过零时电弧燃烧的稳定性。采用DSP(TMS320F2812)作为控制系统核心,用软件编程实现复杂焊接过程的控制,减少了较多硬件控制电路,使焊接设备向柔性化控制方向发展。对于焊接过程的控制,采用数字化PI算法,实现了闭环的恒流控制。采用CPLD(EPM7128STC100)作为数字化PWM控制系统核心,完成数字化PWM控制,避开了模拟PWM控制的种种缺陷,使PWM控制更灵活,更可靠,成本更低廉。应用了CPLD灵活的逻辑可编程能力,把保护电路融入其中,达到对PWM输出信号的控制作用。本文把完成所设计的数字化控制系统应用与焊机主电源上,编写软件实现了电源的恒流控制,并研究了该电源的电流、电压的响应性能。结果表明,所研制的数字化控制系统能实现精确的恒流控制,达到了最初的设定研究目标。更多还原

【Abstract】 Variable Polarity Pulsed MIG (VP PMIG)is a consumable electrode AC pulse weldingprocess, it can used to weld aluminum alloy, mild steel and stainless steel. The advantages such aswelding arc energy, wire melting rate and penetration of weld can be controlled by regulate theratio of EN time to the period of varied polarity pulse current. VP PMIG is appropriate to weldthin plate of aluminum alloy and efficiency is great.A digital control system of VP PMIG arc welding power source is developed based on DSP,the topology and the output current waveform designed can meet the requirement of thin platewelding. Waveform of Varied polarity current is realized by using IGBT as switches of secondaryinverter, constant welding current is realized by inside loop of feedback of current, regulate of arclength can be realized by outside loop of feedback of arc voltage. A full bridge high voltage pulsedarc stabilizing circuit which was powered by single power source is designed to avoid ofextinguishing of cross zero welding arc. This circuit can maintain the stable of arc di-directionallywhen small background current cross zero, ensure the stable burning of welding arc when weldingcurrent cross zero.DSP (TMS320F2812) is the control kernel of VP PMIG power source. Hardware circuit issimplified by using software to control complicated welding process.As to control of weldingprocess,a way of digitital PI arithmetic is used for closed loop of constant-current.CPLD(EPM7128STC100) is the PWM kernel of digital control system.The digital control ofPWM is developed,without the fault of former ananlog control of PWM,the new control of PWMis much more convenient,dependable and cheaper.With the ability of logic programed as toCPLD,the protect circuit is designed to control the signal of PWM.The digital controlling system is used in welding power source .we program constant-currentcontrol software and research respectively the current and voltage step response of power source.The experiment proved that the welding inverter can control the constant-current waveformsprecisely and meet the design requirements.更多还原