【作者】 葛卫清；

【导师】 黄石生；

【作者基本信息】 华南理工大学 ， 材料加工工程， 2012， 博士

【摘要】 提高焊接效率最基本的方式之一是采用多丝焊。双丝焊是多丝焊中最基本的焊接方式，研究双丝高速焊具有代表意义。双丝焊的熔滴过渡过程及其控制的研究吸引了国内外许多研究者的关注。已有研究表明：控制熔滴过渡行为也就控制了焊接质量。进一步开展双丝脉冲焊的控制方法研究以及熔池过渡与焊缝成形的应用研究，可以为研发新的控制技术、改善和提高焊接系统的性能提供理论依据。双丝脉冲MIG焊是一种高效的焊接方法，在实际应用中非常广泛，研究双丝脉冲MIG焊具有理论和实际意义。论文从脉冲焊的机理出发，指出峰值电流Ip、峰值时间Tp、基值电流Ib、基值时间Tb是脉冲焊中最基本的4个参数，也是影响熔滴过渡的最重要参数。这些参数都与占空比有关，因而可以通过控制占空比来控制这些参数。采用状态空间变量法分析了逆变弧焊系统的混沌特性，指出弧焊系统的焊接规范参数需要非常配合的根本原因是由其混沌特性决定的。分析了自行研制的软开关逆变电源的前馈-反馈的控制原理和方式，并采用三端开关器件建模法，得到了有5个变量的非线性模型，从理论上证明了控制系统是一个非线性系统。通过线性化，得到一个简化的小信号数学模型。论文将当前控制领域研究的热点——分数阶理论——首次引入到弧焊控制，提出在弧焊控制系统中使用分数阶PID控制器，对分数阶理论在弧焊控制领域中的应用作了探讨，提出了一种设计分数阶控制器的新方法——值域图解法。采用值域图解法，针对建立的弧焊系统的数学模型设计了一类比例积分型的分数阶控制器(PIλ)，并与传统整数阶控制器(PI)进行了仿真比较。仿真结果表明，分数阶控制器的调节动态性能比整数阶控制器要好，超调量少5%，提高了双丝MIG焊技术的动态性能。采用所设计的分数阶控制器进行了单丝焊试验，并与传统整数阶控制器的作了对比，结果分数阶控制器的效果更好。构建了双丝高速MIG焊及其高速摄影试验平台。双丝高速MIG焊平台由2台专用弧焊逆变电源(1250A+1000A)、水冷方式的“一炬双丝”焊炬等构成，焊接电流可达千安以上。高速摄影系统由功率40mW的半导体激光光源、每秒可拍摄10000张相片的彩色数字高速摄影机等组成，完全满足实验的要求。为了去除弧光，光路采用背光阴影法来拍摄熔滴过渡行为，图片更清晰。采用高速摄影，可以方便对焊接的熔滴过渡过程的观察与分析。论文对双丝大电流高速焊进行了工艺试验，研究了在一定的焊接规范下，双丝脉冲MIG焊接中主机与从机脉冲电流相位关系、脉冲电流频率等对熔滴过渡以及焊缝成形的影响。研究结果表明：脉冲电流相位为交替时，前丝、后丝电弧形态与单丝焊时一样，电弧为锥状。脉冲电流为同步相位时，前、后焊丝的电弧会相互吸引，引起电弧合并，电弧呈蟠桃状。脉冲电流为随机相位时，两电弧时而独立，时而吸引，电弧形状不断变化。脉冲电流频率的变化会改变前丝与后丝的熔滴过渡方式。在电流交替相位的焊接规范下，脉冲电流频率较高时，前丝熔滴过渡方式为射滴过渡，后丝熔滴过渡方式为射流过渡；在脉冲电流频率较低时，前丝、后丝熔滴过渡方式均为射滴过渡模式；而当脉冲电流频率中等时，前丝、后丝熔滴过渡方式均为射流过渡方式。当电流脉冲频率变化时，焊缝成形质量会发生变化。脉冲电流频率较高，焊缝成形较好；而脉冲频率较低时，焊缝成形较差。频率越低，成形越差，并出现驼峰焊。当脉冲电流频率在50-100Hz时，前丝、后丝在熔滴过渡时基本表现为一脉一滴形式，焊缝成形较好。更多还原

【Abstract】 One of the most basic methods to improve welding efficiency is the multi-wire welding.Twin-wire welding is the basic way of multi-wire welding. So research on twin-wire weldingis of great significance. Many domestic and abroad researchers focused their study on doublewire welding droplet transfer process and the formation of weld pool. The existing resultshave demonstrated that the control of droplet transfer behavior will control the weldingquality. It is certain that in-depth study to double wire pulse welding control method andwelding droplet transfer process as well as the weld pool taking shape will provide the theoryfor new control technology and improve welding performance.Twin-wire pulsed MIG welding is a high efficient welding method which has a widerange of practical applications.Thus the study of double wire pulsed MIG welding hastheoretical and practical significance. On the basis of the mechanism of pulsed welding,wepointed out the most basic as well as the most important parameters which affect the droplettransfer in pulsed welding are the peak current Ip, peak time Tp, base current Iband basic timeTb. These parameters are associated with the duty cycle, thus to control these parameters canbe achieved by controlling the duty cycle. By using the state space variable method to analysethe chaotic characteristics of inverter arc welding system,we noted that the root cause for theneeds of the specification parameters match in arc welding system is determined by its chaoticnature of the tie. Also the feed-forward&feedback control principle of the self-developedsoft-switching inverter is analysised. Then a small signal model of the welding system isestablished based on the method of three-terminal-switching device modeling.This article first introduced the hot spot in control field---fractional theory into the arccontrol and pointed out using the fractional-order PID controller in the control system of arcwelding.Then the application of the fractional theory in arc welding control field is discussed,and a range-graphic method of design on fractional order controller is put forward. A kind ofintegral type of fractional order controller (PIλ) is designed depend of the model, andcompared with the traditional integer order controller (PI) in simulation. The simulationresults show that the fractional order controller is better than the integer order controller in theregulation of dynamic performance, less overshoot5%. It improves the double wire weldingtechnology dynamic performance. The single wire welding test using the fractional ordercontroller is done, the test effect is better than the integer order controller.A high-speed dual-wire pulse welding system and high-speed photography experimentplatform are built. The double wire welding experiment platform is composed of a two-wire torch with water cooling system, of two inverter power supplies1250A and1000A. Thebacklight shadow method is used to photograph the droplet transfer behavior in the high speedphotography system. The backlight light comes from a high power semiconductor laser. Thecamera’s type is FASTCAM Super-10KC color digital high speed camera, which can take10,000pictures per second. That can fully meet the experimental requirements. By high speedphotograph system, the welding droplet transfer process can easily be observed and analyzed.Large-current high-speed welding process of twin-wire test is studied. Under somewelding conditions, it is studied that the current phase relationships between the host andslave in double wire pulsed MIG welding, and the influences of droplet transfer and weldformation when pulse current frequency changes. The research results are:(1) the arc shape offormer and rear wire is not effect and is showing cone shape while their pulse current phaseschange by turn;(2) the arc shape is showing peach-shaped while their pulse current phaseschange synchronously, and the reason is the appeal caused by the same direction weldingcurrent of two wires;(3) the weld quality while their pulse current phases change random isbetween that in synchronization and by turn.The pulse current frequency will change the droplet transfer method of the former wireand the rear wire. With the welding specification of current phase changing by turn, thedroplet transfer manner of former wire is shot drops, and that of rear wire is jet transition withhigher frequency. The droplet transfer manners of former wire and rear wire are shot dropstransition with lower frequency. The droplet transfer manners of former wire and rear wire arejet transition with medium frequency. The droplets behave almost one-pulse-one-drop whilepulse current frequency changes around middle frequency. The welded shape is good whenthe pulse current frequency changes between50Hz and100Hz, and the welded shape qualitywill change depend on the pulse frequency.更多还原