BASIC THEORY AND APPLICATIONS OF WELDING ARC SPECTRAL INFORMATION

Welding arc spectral information is a rising welding information source.In some occa- sion,it can reflect many physical phenomena of welding process and solve many problems that cannot be done with arc electric information,acoustic information and other arc information.It is of important significance in developing automatic control technique of welding process and other similar process.Many years study work on welding are spectral information of thc anthor are dis- cussed from three aspects of theory,method and application.Basic theory,view and testing methods of welding arc spectral information has been put forward.In application aspects,many applied ex- amples,for example,monitoring of harmful gases in arc(such as hydrogen and nitrogen)with the method of welding arc spectral information;welding arc spectral imaging of the welding pool which is used in automatic seam tracking;controlling of welding droplet transfer with welding arc spectral information and so on,are introduced.Especially,the successful application in real time controlling of welding droplet transfer in pulsed GMAW is introduced too.These application examples show that the welding arc spectral information has great applied significance and development potentiali- ties.These content will play an important role in applying and spreading welding arc spectral infor- mation technology.     

基于电弧光谱的钢熔化极惰性气体保护焊质量判识

通过对熔化极惰性气体保护电弧焊(MIG焊)电弧光谱分布进行采集,研究其光谱分布的基本特征,并基于光谱分布的分析,通过预设干扰因素,对不同特征谱段光谱信号随焊接过程的变化进行采集,寻求MIG焊接质量在线光谱测控的理论依据和工程实现.研究结果表明,MIG焊电弧光谱在不同谱段存在金属谱线和Ar谱线聚集区.在不同弧长下的不同熔滴过渡形态,其光谱信号在特征谱段得到明显反映,电流变化引起的焊道变宽也有很好的特征信号;不同干扰因素引起的焊接缺陷,在焊接电弧光谱信号不同谱段的分布和变化规律不同,通过对特征谱段信息的采集,可以获得关于焊接过程信息的特征信号,从而实现对MIG焊接质量的分类判识.     

Three-dimensional vision-based sensing of GTAW: a review

Automated and robotic welding is now widely used in manufacturing industry. The control of the welding process plays a crucial role in producing quality welds in automated and robotic welding where the assistance from skilled welders is no longer available. In gas tungsten arc welding (GTAW) which is the primary arc welding process for precision joining of metals, the weld pool is the major source of information that can be used to assure the production of desired weld penetration which is the most critical factor determining the weld integrity. To meet this challenge, various sensing technologies have been proposed/studied to sense and obtain the feedback for the weld pool state. This paper summarizes the researches on weld pool state sensing: conventional sensing technologies, vision sensing technology, and multi-sensor information fusion technology, with emphasis on the analysis of three-dimensional vision sensing methods. And three-dimensional vision sensing, multi-sensor technology, intelligent modeling, and effective commercial product development show the future trends of GTAW penetration sensing.     

熔滴过渡光谱传感与控制的研究

焊接电弧光谱是一个丰富的信息源,电弧的各种物理过程都能在电弧光谱中体现,利用电弧光谱信息能很好地检测和控制脉冲焊熔滴过渡。对电弧光谱辐射情况和对光辐射和接收系统进行了深入的研究和分析,抛弃了一般特征光谱检测设备所必需采用的光谱仪和复杂的光路系统,选用干涉滤光片,选择光谱窗口,设计并制作小型光谱传感器。对喷射过渡过程进行了熔滴过渡检测,利用光谱信息实现了脉冲焊熔滴过渡精确控制为焊接过程精确控制提供了一种新的方法和手段。     

脉冲MIG焊熔滴过渡光谱控制法的研究

在有关电弧光谱信息研究的基础上,提出并成功地实现了脉冲MIG焊熔滴过渡的光谱控制法。它是一种物理状态控制法。试验表明：当峰值电流、基值电流、脉冲频率等焊接参数改变时,本方法均能保 持熔滴过渡为1峰0基的过渡。它具有精确控制熔滴过渡的能力,能更好地得到稳定的焊接过程和焊接质量。它还具 有抗干扰能力强、工艺适应性好、在线调节方便等一系列优点,并可期望用于2峰0基、3峰0基等的控制中,有很大的 发展潜力,为脉冲MIG焊过程和质量的自动控制提供了一个崭新的方法,是电弧光谱信息应用的新的重要发展。 试验还表明,光谱峰后切换法是实现1峰0基的最佳控制策略。论述了该方法的控制系统、原理、控制策略、焊接参数、 试验结果与分析等。     

Rough set based knowledge modeling for the aluminum alloy pulsed GTAW process

The arc welding process is so complex that the classical modeling method cannot obtain the model effectively. However, the model of the arc welding process is necessary for the intelligent control of the process. Therefore, the modeling has been the interest of many researchers. Recently, more and more researchers are attempting to obtain the model of the process by means of intelligent methods, such as the neural network method, the fuzzy set method, and so on. All these methods concentrate on simulating the intelligent behavior of human beings, namely using human experience. Many applications of these methods have proved their effectiveness under certain conditions. However, their limits are obvious and further research is needed. This paper proposes a method of rough set based knowledge modeling for the aluminum alloy pulsed gas tungsten arc welding (GTAW) process. Owing to the ability of dealing with knowledge (experience) of the rough set theory, the method can obtain the knowledge model of the aluminum alloy pulsed GTAW process. The model obtained is easily understood and revised. Experiment results indicate that the method is effective. The method can be regarded as the basis of the intelligent control of the welding process .     

Prediction of pulsed GTAW penetration status based on BP neural network and D-S evidence theory information fusion

This paper used multi-sensor information fusion technology in pulsed gas tungsten arc welding. Arc sensor, visual sensor, and sound sensor were used simultaneously to obtain weld current, voltage, weld pool image, and weld sound information about the pulsed gas tungsten arc welding process, and special algorithms were designed to extract the respective signal features of different sensors’ information. Then D-S evidence theory was used to fuse the different signal features to predict the penetration status about the welding process. Aimed at the difficulty of obtaining basic probability assignment in D-S evidence theory, back-propagation (BP) neural network was used to obtain the basic probability assignment. Experiments were done to obtain data for training the BP neural network and test the prediction reliability of D-S evidence theory information fusion, and comparison results showed that D-S evidence theory could effectively use the information obtained by different sensors and obtain better prediction result than single sensor.     

步进式电弧螺柱焊中螺柱送进深度的自动控制

在分析螺柱送进过程的基础上,对步进式电弧螺柱焊过程中螺柱送进深度的控制问题进行了研究。以焊接过程中螺柱与工件之间的相对位移为控制量,采用位移传感器检测螺柱送进过程中焊枪弹簧压缩位移,以此获知螺柱与工件之间的接触状态,实现对螺柱送进深度的控制。试验结果表明,步进式电弧螺柱可以实现螺柱送进深度的自动控制,无需在焊前预先设置螺柱送进深度;采用不同螺柱提升高度进行焊接时,控制系统可以做出相应的调整,保证合适的螺柱送进深度。将此方法用于螺柱穿透焊,能够有效减小间隙对焊接过程的影响,保证焊接过程的顺利实现。     

干扰因素下钢TIG焊电弧光谱的研究

通过对干扰因素下TIG焊电弧的光谱信息进行采集,研究了气流量变化、焊接试件表面存在锈等干扰因素对焊接过程电弧光谱分布的影响,并基于光谱分布的分析,进一步探讨了不同光谱谱段对干扰因素的反映,寻求实现焊接过程质量在线光谱测控的理论依据。研究结果表明：干扰因素在焊接电弧光谱信号不同谱段（220~300nm、300~430nm、430~520nm、530~680nm、700~900nm、900~1000nm）的分布和变化规律不同,其中 220~300nm对应谱段以FeⅡ谱线的影响为主,在700~900nm对应谱段以ArⅠ谱线的影响为主,在此两个谱段干扰因素响应较明显。历史通道采集结果表明,干扰在250~350nm、700~830nm谱段,信号特征非常明显,具有很好的信噪比,并且不同干扰因素在特征谱段的反映具有自身特点,可据此对干扰因素进行分类判识。
     

变极性等离子弧焊接熔透信息的检测与分析

通过对铝合金3003变极性等离子弧穿孔立焊熔池振荡行为的研究,发现熔池振荡频率与焊接熔透之间的内在规律。在变极性电流的作用下,焊接熔池产生振荡,可以通过对电弧电压频谱分析获得熔池固有振荡频率。分别建立变极性等离子弧穿孔立焊未熔透及完全熔透熔池模型,并分析焊接电流的变化对熔池固有振荡频率的影响,发现焊接电流大小对其影响很小,可以忽略。为了验证该模型的准确性,进行理论与实测分析,结果表明,理论值与实测值相吻合。熔池固有振荡频率主要取决于熔池宽度、深度及材料密度等参数,而其他焊接参数对其没有直接影响。因此,熔池振荡频率可间接反映焊接熔透信息,为焊接质量自动控制提供了理论支持。     

Physical characteristics of welding arc ignition process

The existing research of welding arc mainly focuses on the stable combustion state and the research on the mechanism of welding arc ignition process is quite lack.The tungsten inert gas(TIG) touch arc ignition process is observed via a high speed camera and the high time resolution spectral diagnosis system.The changing phenomenon of main ionized element provided the electrons in the arc ignition is found.The metallic element is the main contributor to provide the electrons at the beginning of the discharging,and then the excitated shielding gas element replaces the function of the metallic element.The electron density during the period of the arc ignition is calculated by the Stark-broadened lines of Hα.Through the discussion with the repeatability in relaxation phenomenon,the statistical regularity in the arc ignition process is analyzed.The similar rules as above are observed through the comparison with the laser-assisted arc ignition experiments and the metal inert gas(MIG) arc ignition experiments.This research is helpful to further understanding on the generation mechanism of welding arc ignition and also has a certain academic and practical significance on enriching the welding physical theoretical foundation and improving the precise monitoring on automatic arc welding process.     

焊接过程控制电弧传感方法的研究

根据熔化极体气保护电弧焊的电弧自身特性提出了一种电弧传感方法。它可以检测坡口或焊接接头的断面形状,进而能测量接头中心位置,从而实现了电弧传感式的焊缝跟踪控制。由于采用电弧传感,因而此方法简洁,设备简单,成本低且工作可靠,对于推广应用极为有意义。由计算机控制焊枪摆动,可实现可编程的多种摆动模式的控制。研究中还推导出电弧传感方法的数学模型,它提示了电弧传感的基本原理,也为采用此方法的控制算法的研究与应用提供了理论依据。     

Numerical analysis of weld pool for galvanized steel with lap joint in GTAW

Galvanized steel is widely used and its demand is growing in automotive industry due to high quality requirement for corrosion resistance. Although there are a lot of demands on using galvanized steel as automotive parts especially for outer body, it has a grave flaw in its welding process. The difficulty is low weldability due to various defects such as porosities and blow holes in weldment, which occurred during welding. A solution to prevent these defects is using hybrid welding process, with two more welding processes. One of the hybrid solutions is using Gas tungsten arc welding (GTAW) as leading position in order to remove the zinc (Zn) coating on the surface before the followed practical fusion welding process. In this research, a numerical analysis model which can predict the eliminated Zn coated layers and the area of Fusion zone (FZ). Developed numerical analysis model was validated through comparing experiment to simulation. Basically, arc heat flux, arc pressure, electromagnetic force and Marangoni flow were employed as the boundary conditions and body force terms. Governing equations such as the continuity, momentum, Volume of fluid (VOF) and energy equations were adopted as usual. In addition to previous model, concentrated arc heat flux and contact thermal conductance models are newly suggested and showed successful result. They are adopted to realize edge concentrated arc and interfacial thermal conductance in lap joint fillet arc welding. Developed numerical analysis model successfully simulated the weld pool and temperature profile therefore the predicted Zn removed area considerably coincided with experimental result.

     

脉冲MIG焊熔滴过渡控制的新进展

介绍脉冲MIG焊（熔化极惰性气体保护焊）熔滴过渡控制的发展现状,分析了现有控制法存在的局限性,阐述一种最新的控制法—熔滴过渡光谱控制法的原理、优越性及其进展。指出这方面的发展趋势。电弧光谱信号在反映脉冲MIG焊熔滴过渡方面有很大的优越性,其信号品质和灵敏度远胜过以往的信号。相应的光谱控制法已在实验室成功地实现了脉冲MIG焊1峰0基的精确控制,并可能推广用于2峰0基、3峰0基的控制,甚至推广用于连续电流焊条件下熔滴过渡的控制中,工艺适应性宽,前景广阔。     

短路过渡CO2焊全数字控制系统

以短路过渡CO2焊全数字控制系统设计和实现为背景,针对全数字控制设计面临的新问题,应用分级递阶智能控制理论,有机地将数字PI控制器、模糊控制器和专家系统结合起来,使控制层次清晰化,实现方案简单化。试验证明,应用该系统在短路过渡区间实现了CO2焊较为理想的波形控制,弧长控制稳定,焊丝伸出长度变化的适应性增强,焊接过程控制智能化。     

Multisensor information fusion of pulsed GTAW based on improved D-S evidence theory

The D-S evidence theory is a method widely used in information fusion technology, but it cannot solve the conflict evidence problem. This paper proposed a new method to dispose the conflict evidence problem in D-S evidence theory. The method first used evidence distance to obtain the weights of different evidences, then fuzzy inference theory was used to adjust the basic probability assignments (BPA) of every evidence according to the obtained weights, and the adjusted BPAs were fused by the D-S combine rules to obtain the fusion results in the end. The method was used in pulsed gas tungsten arc welding (GTAW) and fused the information obtained by arc, sound, and visual sensors in pulsed GTAW process. Experiment results showed that the method could effectively solve the conflict evidence problem, sufficiently fuse different sensors' information, and obtain more precise results than using a single sensor alone.     

脉冲MIG焊建模仿真分析及弧长控制

针对脉冲MIG焊过程中的电弧稳定性问题,建立基于尖端不稳定熔滴过渡理论的焊丝熔化动态电弧模型,并对焊接过程中的电弧电压、电弧长度及熔滴过渡尺寸进行仿真,得到与实际焊接相似的电弧电压波形,分析脉冲电流下熔滴过渡频率及影响电弧稳定性的因素,且进行弧长稳定控制的仿真研究,在此基础上运用快速原型技术建立铝合金脉冲MIG焊控制系统,采用电弧电压反馈对铝合金脉冲MIG焊过程进行送丝调节的弧长控制试验。研究表明:所建立的铝合金脉冲MIG焊焊丝熔化动态电弧模型很好反映了实际焊接过程,揭示出脉冲MIG焊焊接过程中熔滴过渡时间间隔具有一定的不确定性和电弧长度的不稳定性,通过电弧电压反馈控制可显著改善铝合金脉冲MIG焊过程电弧系统的稳定性。     

一种模拟控制式埋弧焊设备的数字化升级改造设计

该文设计了一套基于STM32的双单片机控制系统对模拟控制式埋弧焊设备进行数字化改造。该系统包括电源控制系统和过程控制系统,2个系统之间采用串行异步通信方式,实现命令和参数交换。可以实现焊接电源多种外特性输出,满足埋弧焊、焊条电弧焊、气体保护焊、碳弧气刨工艺需要。设计双闭环控制系统对送丝速度进行调节,设计单闭环控制对小车驱动电机进行控制。测试表明,改造后的焊机用途拓宽,人机界面丰富,引弧、焊接、收弧的稳定性和可靠性均大幅提升,具有很好的实用价值。     

Application of arc plasma spectral information in the monitor of Al–Mg alloy pulsed GTAW penetration status based on fuzzy logic system

In this paper, an intelligent fuzzy system based on arc spectral information was proposed to recognize the weld penetration status. A spectrometer and a visual sensor were used simultaneously to collect the arc spectral and visual information about the Al–Mg alloy pulsed GTAW process, respectively. Principal component analysis was utilized for spectral line identification, redundancy removal and spectral characteristic signals extraction; wavelet packet denoising technique was used to filter these signals. The relationship between the penetration status under different welding conditions and the corresponding spectral signals was discussed and clarified. Finally, a fuzzy system based on the spectral signals was developed and successfully used to estimate the percentage index of the weld penetration status. With a binary decision of penetration index, the average recognition rate for the penetration status about the specific welding conditions was no less than 82.1 %.     

某发动机动力涡轮轴承座氩弧焊工艺研究

动力涡轮轴承座是某航空发动机的重要部件,在对其上的各种安装座氩弧焊后出现了焊接裂纹,严重影响了产品质量和交付进度.本文通过荧光检查和冶金分析,确定了氩弧焊焊接裂纹的性质为结晶裂纹,并针对结晶裂纹的产生机理和预防措施,调整了焊接参数.试验验证表明,采用增设焊接接头坡口、采用分段式焊接、改进焊缝收弧方式以及控制焊接速度等工艺措施,能够有效地防止结晶裂纹的产生,提高产品的质量.