【作者】 林放；

【导师】 郑时雄； 薛家祥；

【作者基本信息】 华南理工大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 本文针对脉冲MIG焊电源在峰值阶段恒流+基值阶段恒流(I-I)控制方式下存在电弧自调节能力差的问题,展开对脉冲MIG焊电弧调节机理、脉频调制(PFM)电弧控制方法和均匀调节电弧控制方法研究。通过对目前国内外脉冲MIG焊电弧控制方面研究成果分析,发现在脉冲MIG焊电弧控制领域中存在着电弧调节机理的基础理论不完善,从电弧调节机理层面对各种弧长控制方法的原理和性能分析比较缺失,尤其是对不同种类焊丝在脉冲MIG焊电弧控制中所表现出的差异性研究极少。因此,本文首先推导并建立了熔化极焊丝干伸长在电弧热和电阻热共同作用下的温度场数学模型,通过对温度场分析,可以得出电阻热和电弧热对不同种类焊丝的熔化作用差异,进而根据焊丝物理特性和熔化特性,将其划分为阻性焊丝和非阻性焊丝两大类,分别对这两类焊丝在脉冲MIG焊各种条件下的电弧调节机理进行分析研究。在考虑干伸长电阻热对阻性焊丝熔化速度的影响下,利用弧长数学模型和原有的阻性焊丝熔化特性,从理论上推导出新的阻性焊丝熔化特性及相应的等熔化速度曲线,并且,通过试验验证了新的阻性焊丝等熔化速度曲线的正确性。根据新的阻性焊丝熔化特性,通过对恒流脉冲MIG焊在等速送丝条件下的电弧调节机理分析,得出新的论点:对于阻性焊丝在等速送丝条件下适合采用恒流脉冲MIG焊电源,该焊接方法的电弧自我调节能力强,焊接过程易于稳定。根据新的阻性焊丝熔化特性,从电弧调节机理上进行了证明,阻性焊丝在导电嘴到工件距离(CTWD)发生改变时,采用PFM电弧调节方法无法将焊接电压调整回初始值,并且电弧工作点会在初始值附近进行小幅振荡;在均匀调节弧压控制下,当CTWD发生改变时,虽然可以将焊接电压调节回初始值,但同时引起焊丝熔化速度的变化,以及弧长的相反方向变化,通过电弧的阶跃试验逐一验证了这些问题。针对不同的工艺要求和应用场合,设计了两种不同的脉冲MIG焊电源硬件实施方案。一种是MCU(微控制单元)+硬件驱动的方案,该方案系统响应速度快,性能稳定;另一种是ARM+DSP(数字信号处理器)集成控制方案,该方案性能先进但可靠性还有待提高。针对阻性焊丝在电弧控制中存在的问题,提出了基于亚射流过渡的区间弧压控制方法,并在本试验平台上进行实现,通过试验验证了该优化控制方案的可行性,对电弧控制中存在的问题可以进行改善,同时,该方法也适用于非阻性焊丝脉冲MIG焊弧压控制,使电弧调节更加平稳。在基于亚射流过渡的区间弧压控制方法实施中,采用了带有死区的双模数字PID控制方法,在起弧初始阶段和稳定燃弧阶段分别采用两套PID控制参数分别进行控制,以满足不同阶段电弧调节特性的需要。针对均匀调节系统在采用区间弧压控制方法时会对系统稳定性带来不良影响这一问题,提出了自适应模糊PID控制方法,并通过MATLAB仿真验证了采用自适应模糊PID控制方法可以有效解决这一问题。利用设计的阶跃装置对钢焊丝和铝焊丝分别进行无弧压控制、均匀调节弧压控制方式和PFM弧压控制方式下的电弧阶跃试验,对试验结果进行了对比分析,逐一验证了各章节中提出的论点。更多还原

【Abstract】 Because of the weak arc auto-adjusting capacity of Pulsed-MIG Welding in peak phase constant current + base phase constant current (I-I) control, the arc adjusting principles of Pulsed-MIG Welding, PFM arc control method and uniform adjusting arc control method are researched in this paper.Through analysis of the research of Pulsed-MIG Welding arc control in domestic and abroad, the imperfect of arc adjusting basic principles in Pulsed-MIG Welding is discovered. There are few analysis on the principles and performance of all sorts of arc control method from the view of arc adjusting principles. Especially, the diversity research on Pulsed-MIG Welding arc control of different wires is in extremely deficiency.Therefore, temperature field mathematical model of consumable electrode Through-the-Wire under both arc thermal and resistive thermal effect is firstly deduced and established. Through the analysis on temperature field, the melting diversity of different wires under the resistive thermal and arc thermal effects can be found out. Further, according to the physical characteristics and melting characteristics of wires, wires can be divided into two kinds, the resistive-wire and the non-resistive wire. Individual analysis on arc adjusting principles of different wires under different conditions are carried out.Under the influence on melting speed of resistive welding wire that the Elongation heat of the resistance brings , using arc length mathematical model and the nature pre-arcing characteristics of resistive welding wire , pre-arcing characteristics of new resistive welding wire and corresponding curve of the constant speed melting can be devised theoretically. And through experiment , the validity of the constant speed melting curve is confirmed .According to the pre-arcing characteristics of the new resistive welding wire ,it is concluded that the new thesis by analyzing the arc regulating mechanism of Constant current pulse MIG welding at the same speed. It is described in the thesis that it is proper to use Constant current pulse MIG welding power when the feed speed of welding wire is constant , the arc of this welding can be adjusted by itself which can provide a more stable welding process.According to the pre-arcing characteristics of the new resistive welding wire, the theory of arc adjustment proves that when the distance between contact tub and the workpiece varies, welding voltage can not be adjusted to the original value by using the PFM arc adjustment method. In addition, the operating point of the arc will oscillate slightly nearby the original value; Step experiments of arc verify that when the CTWD varies, welding voltage can be adjusted to the original value by uniformly adjusting the arc voltage. But melting rate of the welding wire will be changed and the variation direction of arc length is opposite at the same time.Two deferent designs of the control core,“MCU + hardware driver”and“DSP integrated control”, are designed for different applications. The former design has fast response and stable performance, while the latter design is advanced but astable.The method that base on section arc voltage control of meso-spray transfer is proposed aiming at the problems that exist in the control of resistive wire, and is accomplished in the experiment platform we set, This experiment proves that the optimal control method is feasibility and get a better result in arc control, it also can be applied to non-resistive wire pulsed MIG welding arc voltage control and make arc adjustment more stable.The control method of double-mode digital PID with deadbeat is used in the application of method based on sub-shot stream section arc voltage control of meso-spray transfer, Different PID control parameters is selected in the stage of arcing and the stage of arc burning to meet the needs of different characteristics at different stage of arc adjustmentAdaptive fuzzy PID control method is proposed aiming at the problem of adverse effects to system stability in uniform conditioning system using section arc voltage control, and use MATLAB simulation to prove that the adaptive fuzzy PID control method can effectively solve this problem.With the use of step equipment that design, do the arc step experiments with non-arc voltage control, uniform conditioning arc voltage control and PFM arc voltage control in the condition of using steel welding wires and the condition of using aluminum welding wires, The results of experiments were analyzed and compared, which one by one proved the arguments that each chapter proposed.更多还原