基于混合信号FPGA的脉冲MIG焊接电源控制器的设计
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摘要
焊接作为制造业的基础工艺与技术,在20世纪为工业经济的发展做出了重要的贡献。随着对焊接工艺的不断深入研究,各种复杂的焊接工艺算法被不断地提出,这也对焊接方法以及焊机的控制提出了更高的要求。脉冲MIG焊具有焊接质量稳定可靠、焊接参数的调节范围大、有利于实现全位置焊接等优点,在焊接领域得到了广泛的应用。目前,脉冲MIG焊接技术,综合了人工智能技术、数字化信息处理技术、计算机技术等,正朝着焊接高速高效化、全数字化、智能化的方向发展。
本文通过对IGBT弧焊逆变器的电路结构和工作原理进行分析,并结合脉冲MIG焊的工艺特点以及每个工艺参数的作用,设计了基于弧长同步脉冲法的焊接电弧控制策略和基于模糊自适应PID控制器的焊接电流控制策略,其中弧长控制策略,通过调节基值电流时间使电弧输出的平均电压能够跟随给定平均电压输入,保证了弧长的稳定性；电流控制策略,满足了不同的输入电流值对PID控制参数的需要,实现了脉冲MIG焊所要求的一脉一滴的熔滴过渡形式,同时,这种双闭环控制策略能有效的抑制扰动,与传统的开环控制相比,优势很明显。
根据所要驱动的功率器件IGBT的开关特性,并结合电流型PWM的突出优点,本文设计了数字PWM驱动电路,利用给定信号、反馈信号与锯齿波共同产生驱动脉冲,电流波动小,控制精度高,同时为了抑制变压器偏磁引起的过流现象,设计了基于变压器原边电流反馈的保护电路。
本文结合当前FPGA技术的发展成果,选用Actel公司的一款具有模拟功能的Flash架构的混合信号FPGA作为主控芯片,该芯片的选用有效的解决了以DSP做主控芯片时CPU运算负担过重的问题,同时,该芯片与基于SRAM架构的FPGA相比具有低系统成本、高度的安全性、上电即行、高可靠性和低功耗等优势。设计时采用Verilog硬件描述语言,FPGA内部程序采用模块化设计,各个模块之间并行运行,主要实现了焊接电流电压双闭环控制、AD采样控制、双口RAM读写控制以及焊接工艺时序控制等功能,由于采用模块化设计,各个模块可以单独调用调试,改善了运行速度,提高了调试的便利性。
本文最后对所设计的控制系统进行了测试,包括弧长控制测试、电流环控制策略测试、焊接工艺处理功能测试以及整体的焊接测试,实验结果表明,所设计的系统焊接过程比较平稳,达到了控制要求。
Welding process is the basic technology of manufacturing. It has made important contributions to the development of industrial economy in the 20th century. With the deepening research of welding process, many complex algorithms of welding process have been constantly raised. It puts forward higher requirements to the welding method and control of the welding machine. Pulsed MIG welding process has the characteristics of reliable and stable quality of welding, wide adjustment of welding parameters and better achievement of all-position welding, so it is widely used in the welding field. Currently, pulsed MIG welding process makes a combination of artificial intelligence technology, digital information processing technology and computer technology. It is moving in the direction of high efficient, all-digital and intelligence.
By analyzing the circuit structure and working principle of the IGBT arc welding invert, combining the technology characteristics of pulsed MIG and the effect of every technology parameter, the paper designs welding arc length control strategy based on sync pulse method and welding current control strategy based on fuzzy-adaptive PID controller. In order to keep the arc length stable, welding arc length control adjusts the base-value current time to make sure the average voltage of the arc output following a given average voltage input. The current control strategy meets the different input current needs of different PID control parameters and achieves the required pulsed MIG welding metal transfer form:a pulse, a drop. And this two-closed loop control strategy can effectively suppress disturbance. It has obvious advantages compared with the traditional open-loop control.
According to the switching characteristics of the driving IGBT power device and combining the advantage of current-mode PWM, the paper designs digital PWM drive circuit. It uses the given signal, the feedback signal and the sawtooth wave together to generate the drive pulse. The designed PWM drive circuit has a small current fluctuation and a high control precision. Meanwhile, the paper designs a protect circuit based on the current feedback of the transformer primary side to suppress over-current phenomenon caused by transformer bias.
The paper combines the current development of the FPGA technology. And the paper selects a mixed-signal FPGA of Actel company based on flash architecture which has analog functions as the master chip. The selection of the FPGA effectively solutes the problem that the CPU has a heavy burden of computing using DSP as the master chip. Meanwhile, compared with FPGA based on SRAM architecture, the chip has a characteristics of low system cost, high security, live at Power-up, high reliability and low power consumption. The program is designed modularly in FPGA by verilog hardware description language. Every module runs in parallel. The program achieves the functions as bellow, two-closed loop control of welding current and voltage, control of AD sample, control of reading and writing dual port RAM and control of welding timing process. Because the program is designed modularly, every module can be used for debugging independently. It improves the speed and facilitates debugging.
Finally, the designed system is tested, including the control of arc test, the current loop test, welding process test and the whole welding test. It indicates that the welding process of the designed system is smooth and achieves the control requirement.
本文通过对IGBT弧焊逆变器的电路结构和工作原理进行分析,并结合脉冲MIG焊的工艺特点以及每个工艺参数的作用,设计了基于弧长同步脉冲法的焊接电弧控制策略和基于模糊自适应PID控制器的焊接电流控制策略,其中弧长控制策略,通过调节基值电流时间使电弧输出的平均电压能够跟随给定平均电压输入,保证了弧长的稳定性；电流控制策略,满足了不同的输入电流值对PID控制参数的需要,实现了脉冲MIG焊所要求的一脉一滴的熔滴过渡形式,同时,这种双闭环控制策略能有效的抑制扰动,与传统的开环控制相比,优势很明显。
根据所要驱动的功率器件IGBT的开关特性,并结合电流型PWM的突出优点,本文设计了数字PWM驱动电路,利用给定信号、反馈信号与锯齿波共同产生驱动脉冲,电流波动小,控制精度高,同时为了抑制变压器偏磁引起的过流现象,设计了基于变压器原边电流反馈的保护电路。
本文结合当前FPGA技术的发展成果,选用Actel公司的一款具有模拟功能的Flash架构的混合信号FPGA作为主控芯片,该芯片的选用有效的解决了以DSP做主控芯片时CPU运算负担过重的问题,同时,该芯片与基于SRAM架构的FPGA相比具有低系统成本、高度的安全性、上电即行、高可靠性和低功耗等优势。设计时采用Verilog硬件描述语言,FPGA内部程序采用模块化设计,各个模块之间并行运行,主要实现了焊接电流电压双闭环控制、AD采样控制、双口RAM读写控制以及焊接工艺时序控制等功能,由于采用模块化设计,各个模块可以单独调用调试,改善了运行速度,提高了调试的便利性。
本文最后对所设计的控制系统进行了测试,包括弧长控制测试、电流环控制策略测试、焊接工艺处理功能测试以及整体的焊接测试,实验结果表明,所设计的系统焊接过程比较平稳,达到了控制要求。
Welding process is the basic technology of manufacturing. It has made important contributions to the development of industrial economy in the 20th century. With the deepening research of welding process, many complex algorithms of welding process have been constantly raised. It puts forward higher requirements to the welding method and control of the welding machine. Pulsed MIG welding process has the characteristics of reliable and stable quality of welding, wide adjustment of welding parameters and better achievement of all-position welding, so it is widely used in the welding field. Currently, pulsed MIG welding process makes a combination of artificial intelligence technology, digital information processing technology and computer technology. It is moving in the direction of high efficient, all-digital and intelligence.
By analyzing the circuit structure and working principle of the IGBT arc welding invert, combining the technology characteristics of pulsed MIG and the effect of every technology parameter, the paper designs welding arc length control strategy based on sync pulse method and welding current control strategy based on fuzzy-adaptive PID controller. In order to keep the arc length stable, welding arc length control adjusts the base-value current time to make sure the average voltage of the arc output following a given average voltage input. The current control strategy meets the different input current needs of different PID control parameters and achieves the required pulsed MIG welding metal transfer form:a pulse, a drop. And this two-closed loop control strategy can effectively suppress disturbance. It has obvious advantages compared with the traditional open-loop control.
According to the switching characteristics of the driving IGBT power device and combining the advantage of current-mode PWM, the paper designs digital PWM drive circuit. It uses the given signal, the feedback signal and the sawtooth wave together to generate the drive pulse. The designed PWM drive circuit has a small current fluctuation and a high control precision. Meanwhile, the paper designs a protect circuit based on the current feedback of the transformer primary side to suppress over-current phenomenon caused by transformer bias.
The paper combines the current development of the FPGA technology. And the paper selects a mixed-signal FPGA of Actel company based on flash architecture which has analog functions as the master chip. The selection of the FPGA effectively solutes the problem that the CPU has a heavy burden of computing using DSP as the master chip. Meanwhile, compared with FPGA based on SRAM architecture, the chip has a characteristics of low system cost, high security, live at Power-up, high reliability and low power consumption. The program is designed modularly in FPGA by verilog hardware description language. Every module runs in parallel. The program achieves the functions as bellow, two-closed loop control of welding current and voltage, control of AD sample, control of reading and writing dual port RAM and control of welding timing process. Because the program is designed modularly, every module can be used for debugging independently. It improves the speed and facilitates debugging.
Finally, the designed system is tested, including the control of arc test, the current loop test, welding process test and the whole welding test. It indicates that the welding process of the designed system is smooth and achieves the control requirement.
引文
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[3]黄石生主编.弧焊电源及其数字化控制[M].北京：机械工业出版社,2007.
[4]吴开源,陆沛涛,李阳等.脉冲MIG焊控制的研究现状与展望[J].电焊机.2003,33(2)：1-4.
[5]李亚江,刘鹏,刘强等编著.气体保护焊工艺及应用[M].北京：化学工业出版社,2005.
[6]Neal Borchert. New technology and pulsed MIG welding[J]. Technology Directions,1995,55(2):45-47.
[7]http://www.fronius.com.cn/fronius_cn/equipment/mig_mag.asp.
[8]李峰,李亮玉,李香.国内全数字化焊机的研究现状[J].焊接技术,2006,35(4)：6-8.
[9]张光先.软开关逆变式低飞溅C02气体保护焊的研究[D].济南：山东大学,2004.
[10]韩永强,曾亮.数字化逆变焊机的发展和应用[J].电焊机,2009,39(2)：6-10.
[11]刘嘉.弧焊逆变电源的数字化控制[D].北京：北京工业大学,2002.
[12]黄石生.逆变理论与弧焊逆变器[M].北京：机械工业出版社,1995.
[13]郭胜强,吴曙明,杨永青等.IGBT驱动脉冲变压器工作过程分析及参数选择[J].电焊机,2001(8)：26-28.
[14]李中友.IGBT弧焊逆变器研制中的几点体会[J].电焊机,1995(4)：9-15.
[15]韩国明.焊接工艺理论与技术(第2版)[M].北京：机械工业出版社,2007.
[16]孙栋,赵举东,赵家瑞.智能控制MIG焊熔滴过渡[J].电焊机.1996(2)：11-14.
[17]Rajasekaran S. Droplet detachment and plate fusion characteristics in pulsed current gas metal arc welding[J]. Welding Journal,1996,75(6):254s-268s.
[18]栗卓新,张征,刘海云GMAW焊熔滴过渡模型的研究进展[J].中国机械 工程,2007,18(12)：1501-1504.
[19]姜伟雁,张九海.赵崇仪MIG(MAG)脉冲焊熔滴的过渡行为[J].焊接学报.1995,15(1)：50-57.
[20]M amin. Pulse current parameters for arc stability and controlled metal transfer in arc welding[J]. Metal Construction,1983, (95):272-277.
[21]姚屏,薛家祥,李晋等.三种脉冲MIG焊中值波形控制方法研究[J].焊接,2008(11)：59-63.
[22]吴开源,黄石生,蒙永民等.脉冲MIG焊熔滴过渡中值波形的控制策略[J].焊接学报,2004,25(8)：51-58.
[23]吴开源,黄石生,李星林等.脉冲MAG焊后中值脉冲工艺研究[J].中国机械工程.2007,18(20)：2468-2471.
[24]柯立涛等.中值时间对脉冲MIG焊熔滴过渡的影响[J].焊接.2006(8)：18-21.
[25]曾毅.现代运动控制系统工程[M].北京：机械工业出版社,2006.
[26]李正军.计算机控制系统[M].北京：机械工业出版社,2007.
[27]Oshima Kenji. Fuzzy Expert System for Robotic Arc Welding[J]. ASME. Production Engineering Division,1991(51):85-90.
[28]田淑杭,姜丽鹃.一种参数自整定模糊PID控制器的研究[J].电气传动自动化,2003(6)：28-30.
[29]李界家,付萍,片锦香等.参数自调整模糊控制在炉温控制中的应用[J].控制工程,2004(1)：14-16.
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