受控脉冲穿孔等离子弧焊接背面小孔动态行为的视觉检测与控制
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摘要
受控脉冲穿孔等离子弧焊工艺对传统工艺做出了新颖改进,具备获得优质接头并拓宽焊接工艺参数裕度的潜力。但是,原有系统通过检测等离子弧尾焰电压信号来间接反映小孔状态,不足以充分描述小孔动态变化过程的细节。本研究采用视觉传感方法获取工件背面的小孔图像,能够直观清晰地表现小孔特征参数随脉冲电流的瞬时演变过程。本文研究结果为深入理解小孔与熔池热状态的变化规律奠定基础,具有重要的理论意义和实际应用价值。
构建了以普通工业CCD摄像机为核心的视觉传感系统,不仅可以测量背面小孔出口的长度和宽度等尺寸参数,而且可以测量背面小孔中心与正面焊枪中心轴线之间的偏移距离(即小孔中心偏移量)。在恒定参数穿孔焊接过程中,通过使用不同的焊接电流、焊接速度和离子气流量调节电弧穿透能力,观察背面小孔参数的变化。发现背面小孔中心偏移量对电弧穿透能力的变化更为敏感。电弧热输入变化时,小孔周围热状态发生变化；这不仅可以影响焊缝熔宽,而且可以显著地改变小孔前壁的倾斜程度。小孔前壁的倾斜程度决定了背面小孔中心偏移量的大小。因此,小孔中心偏移量可以很好地反映小孔前壁熔化状态。小孔热状态发生变化时,背面小孔中心偏移量可以比小孔尺寸更好地反映小孔的动态特性。
背面小孔中心偏移量的大小,代表了小孔孔道的弯曲程度,是影响焊缝缺陷形成的关键因素之一。实验结果表明,如果小孔中心偏移量过大,焊缝中容易形成气孔,且焊缝表面成形质量差；如果小孔中心偏移量过小,熔池体积过度长大后,容易出现焊缝塌陷甚至烧穿。根据背面小孔中心偏移量可以预测焊缝成形不佳、焊缝气孔、焊缝塌陷和烧穿四种缺陷。
研究发现,受控脉冲穿孔焊接过程中,每一个脉冲周期内,在穿透小孔形成瞬间,背面小孔中心偏移量最大；随后,小孔中心偏移量迅速降低。在闭合小孔阶段终了或者穿透小孔建立之初,小孔前壁倾斜程度最大。穿透小孔维持阶段越长,小孔前壁曲面倾斜程度越小,则背面小孔中心偏移量越小。通过调节脉冲电流后沿的下降斜率,可以控制穿透小孔维持阶段的时长,从而控制背面小孔中心偏移量。
基于合适的预测控制算法,建立了以实时检测的背面小孔中心偏移量为被控制量、脉冲电流下降时间(表征脉冲电流后沿的下降斜率)为控制量的受控脉冲穿孔等离子弧焊控制系统。9.5mm厚度不锈钢板穿孔等离子弧焊接控制实验表明,控制过程稳定,每个脉冲内小孔可靠地穿透和闭合,焊缝成形和接头质量良好。
The controlled-pulse keyhole plasma arc welding (PAW) is a novel improvement on the traditional pulse PAW. It has potential to produce high quality joints under wider range of process parameters. However, the developed system used the efflux plasma voltage to reflect the keyhole state indirectly, such a voltage signal can only describe whether the keyhole is fully-penetrated or not, but can not give more comprehensive information of the keyhole dynamic behaviors. In this study, vision sensing technology is employed to capture the keyhole image from backside of the test pieces, and the keyhole image sequence directly shows the keyhole evolution process at different instants on the welding current pulse waveform. The research results lay foundation for deeply understanding the thermal behaviors of both the keyhole and weld pool during the keyhole PAW process, and hence have important theoretical significance and will promote the practical applications of the controlled-pulse keyhole PAW process.
The vision sensing system is constructed based on a common industrial CCD camera. It can measure not only the length and width of the backside keyhole exit, but also the deviation distance from backside keyhole exit center point to the welding torch axis. Different levels of welding current, welding speed and plasma gas flow rate have been selected in series of constant-parameter keyhole PAW processes. From these tests, it is observed that keyhole parameters, including the keyhole size and keyhole deviation distance, vary as the plasma arc penetration ability changes, but the keyhole deviation distance experiences much larger variation than the keyhole size does when a welding parameter has the same varying amplitude. Changing of the heat input alters the thermal state in the keyhole and weld pool and will induce the variation of the melting condition around the keyhole, so that the weld width and the front keyhole wall inclination will be both changed. The inclined degree of the front keyhole wall directly determines how far is the backside keyhole exit deviated away from the torch axis (deviation distance). Thus, the keyhole deviation distance is a very useful parameter to reflect the keyhole front wall melting state and its thermal condition. As the thermal state changes in the fully-penetrated keyhole process, the backside keyhole deviation distance varies with much larger scope and faster speed than the keyhole size parameters do. The deviation distance hence is a better variable to describe the keyhole dynamic characteristics.
The quantity of the backside keyhole deviation distance, i.e. the inclined degree of the keyhole channel, is one of the critical factors to affect the weld defects formation. If the keyhole deviation distance is too large, porosity will easily occur with a bad front weld surface. If the deviation value reduces to nearly zero, the high level heat energy in the keyhole will speed up the melting process of the solid metal around the keyhole, and the weld pool will over-grow so that it is easy to collapse or even burn-through. Hence, the backside keyhole deviation distance can be used to predict the formation of four kinds of weld defects:low quality front weld surface, porosity, weld pool collapse and burn-through.
In each pulse cycle of the controlled-pulse keyhole PAW process, backside keyhole deviation distance reaches its peak value when the fully-penetrated keyhole firstly forms; then, it decreases fast during the keyhole open period. It indicates that the keyhole front wall is inclined most severely at the instant of the fully-penetrated keyhole just forms or the closed keyhole period ends. Increasing of the keyhole open period decreases the keyhole front wall inclined degree and hence decreases the backside keyhole deviation distance. Adjusting of the current falling rate at the trailing edge of the welding current pulse will control the duration of the keyhole open period, hence control the level of the backside keyhole deviation distance.
Taking the backside keyhole deviation distance as the controlled variable and current falling rate at trailing edge of the welding current pulse as the controlling variable, a modified controlled-pulse keyhole PAW system has been developed based on the predictive control algorithm. The welding tests have been carried out on stainless steel plates of thickness up to9.5mm. It demonstrates that the control process is stable, keyhole opens and closes smoothly in every pulse, and high quality welds have been obtained.
构建了以普通工业CCD摄像机为核心的视觉传感系统,不仅可以测量背面小孔出口的长度和宽度等尺寸参数,而且可以测量背面小孔中心与正面焊枪中心轴线之间的偏移距离(即小孔中心偏移量)。在恒定参数穿孔焊接过程中,通过使用不同的焊接电流、焊接速度和离子气流量调节电弧穿透能力,观察背面小孔参数的变化。发现背面小孔中心偏移量对电弧穿透能力的变化更为敏感。电弧热输入变化时,小孔周围热状态发生变化；这不仅可以影响焊缝熔宽,而且可以显著地改变小孔前壁的倾斜程度。小孔前壁的倾斜程度决定了背面小孔中心偏移量的大小。因此,小孔中心偏移量可以很好地反映小孔前壁熔化状态。小孔热状态发生变化时,背面小孔中心偏移量可以比小孔尺寸更好地反映小孔的动态特性。
背面小孔中心偏移量的大小,代表了小孔孔道的弯曲程度,是影响焊缝缺陷形成的关键因素之一。实验结果表明,如果小孔中心偏移量过大,焊缝中容易形成气孔,且焊缝表面成形质量差；如果小孔中心偏移量过小,熔池体积过度长大后,容易出现焊缝塌陷甚至烧穿。根据背面小孔中心偏移量可以预测焊缝成形不佳、焊缝气孔、焊缝塌陷和烧穿四种缺陷。
研究发现,受控脉冲穿孔焊接过程中,每一个脉冲周期内,在穿透小孔形成瞬间,背面小孔中心偏移量最大；随后,小孔中心偏移量迅速降低。在闭合小孔阶段终了或者穿透小孔建立之初,小孔前壁倾斜程度最大。穿透小孔维持阶段越长,小孔前壁曲面倾斜程度越小,则背面小孔中心偏移量越小。通过调节脉冲电流后沿的下降斜率,可以控制穿透小孔维持阶段的时长,从而控制背面小孔中心偏移量。
基于合适的预测控制算法,建立了以实时检测的背面小孔中心偏移量为被控制量、脉冲电流下降时间(表征脉冲电流后沿的下降斜率)为控制量的受控脉冲穿孔等离子弧焊控制系统。9.5mm厚度不锈钢板穿孔等离子弧焊接控制实验表明,控制过程稳定,每个脉冲内小孔可靠地穿透和闭合,焊缝成形和接头质量良好。
The controlled-pulse keyhole plasma arc welding (PAW) is a novel improvement on the traditional pulse PAW. It has potential to produce high quality joints under wider range of process parameters. However, the developed system used the efflux plasma voltage to reflect the keyhole state indirectly, such a voltage signal can only describe whether the keyhole is fully-penetrated or not, but can not give more comprehensive information of the keyhole dynamic behaviors. In this study, vision sensing technology is employed to capture the keyhole image from backside of the test pieces, and the keyhole image sequence directly shows the keyhole evolution process at different instants on the welding current pulse waveform. The research results lay foundation for deeply understanding the thermal behaviors of both the keyhole and weld pool during the keyhole PAW process, and hence have important theoretical significance and will promote the practical applications of the controlled-pulse keyhole PAW process.
The vision sensing system is constructed based on a common industrial CCD camera. It can measure not only the length and width of the backside keyhole exit, but also the deviation distance from backside keyhole exit center point to the welding torch axis. Different levels of welding current, welding speed and plasma gas flow rate have been selected in series of constant-parameter keyhole PAW processes. From these tests, it is observed that keyhole parameters, including the keyhole size and keyhole deviation distance, vary as the plasma arc penetration ability changes, but the keyhole deviation distance experiences much larger variation than the keyhole size does when a welding parameter has the same varying amplitude. Changing of the heat input alters the thermal state in the keyhole and weld pool and will induce the variation of the melting condition around the keyhole, so that the weld width and the front keyhole wall inclination will be both changed. The inclined degree of the front keyhole wall directly determines how far is the backside keyhole exit deviated away from the torch axis (deviation distance). Thus, the keyhole deviation distance is a very useful parameter to reflect the keyhole front wall melting state and its thermal condition. As the thermal state changes in the fully-penetrated keyhole process, the backside keyhole deviation distance varies with much larger scope and faster speed than the keyhole size parameters do. The deviation distance hence is a better variable to describe the keyhole dynamic characteristics.
The quantity of the backside keyhole deviation distance, i.e. the inclined degree of the keyhole channel, is one of the critical factors to affect the weld defects formation. If the keyhole deviation distance is too large, porosity will easily occur with a bad front weld surface. If the deviation value reduces to nearly zero, the high level heat energy in the keyhole will speed up the melting process of the solid metal around the keyhole, and the weld pool will over-grow so that it is easy to collapse or even burn-through. Hence, the backside keyhole deviation distance can be used to predict the formation of four kinds of weld defects:low quality front weld surface, porosity, weld pool collapse and burn-through.
In each pulse cycle of the controlled-pulse keyhole PAW process, backside keyhole deviation distance reaches its peak value when the fully-penetrated keyhole firstly forms; then, it decreases fast during the keyhole open period. It indicates that the keyhole front wall is inclined most severely at the instant of the fully-penetrated keyhole just forms or the closed keyhole period ends. Increasing of the keyhole open period decreases the keyhole front wall inclined degree and hence decreases the backside keyhole deviation distance. Adjusting of the current falling rate at the trailing edge of the welding current pulse will control the duration of the keyhole open period, hence control the level of the backside keyhole deviation distance.
Taking the backside keyhole deviation distance as the controlled variable and current falling rate at trailing edge of the welding current pulse as the controlling variable, a modified controlled-pulse keyhole PAW system has been developed based on the predictive control algorithm. The welding tests have been carried out on stainless steel plates of thickness up to9.5mm. It demonstrates that the control process is stable, keyhole opens and closes smoothly in every pulse, and high quality welds have been obtained.
引文
[1]B.E. Paton.世纪之交论焊接[J].航空工艺技术,1999(2)：13-17.
[2]潘际銮.二十一世纪焊接科学研究的展望[C].第九次全国焊接技术会议论文集,第一册,天津,1999年11月：D001-017.
[3]T.W. Eagar. Welding and joining:moving from art to science [J]. Welding Journal,1995,74(6):49-55.
[4]S.A. David and T. DebRoy. Current issues and problems in welding science [J]. Science,1992,257 (24):497-502.
[5]K.A. Persson. Welding and cutting beyond the year 2000 [J]. Svetsaren,1999, 54(1):74-76.
[6]戴为志.从“鸟巢”钢结构焊接工程看钢结构焊接技术发展趋势[J].现代焊接,2007(9)：J-1-J-8.
[7]Bob Turpin, Dan Danks, John Callahjan and William Wood. Narrow gap electro slag is process of choice for welding San Francisco Oakland Bay bridge[J]. Welding Journal,2012(6):24-31.
[8]何庆中,袁宏远.多层包扎压力容器包扎焊接制造工艺改进[J].压力容器,2008(10)：44-48.
[9]B. Irving. Why aren't airplane welded [J]. Welding Journal,1997,76(1):34-41.
[10]P.F. Mendez. New trends in welding in the aeronautic industry [C]. New Trends for the manufacturing in the Aeronautic Industry. San Sebatian, Spain, May 24-25,2000:21-38.
[11]关桥.我国现代运载工具制造工程中的特种焊接技术[A].与时俱进、追求卓越-中国机械工程学会焊接学会四十周年、中国焊接协会十五周年纪念文集[C].2002.
[12]陈家本,郑惠锦,朱若凡,顾长石.中国船舶焊接技术进展[J].焊接,2007(5)：1-6.
[13]李轶非,王梁等.NiCrMoV耐热钢贝氏体焊缝韧性薄弱区的确定[J].机械工程学报,2013,49(4)：83-88.
[14]杨广臣,薛忠明,张彦华.厚板多层多道焊角变形分析方法[J].焊接学报,2004(1)：114-118.
[15]J.F. Lancaster. High power density welding. The physics of welding, chpt.8 [M]. 1984, Perganon Press, Oxford.
[16]C.M. Banas. Electron beam, laser beam and plasma arc welding studies[R]. NASA Contractor Report (NASA CR-132386), March 1974.
[17]E. Craig. The plasma arc process-A review [J]. Welding Journal,1988,67(2): 19-25.
[18]B.B. Nefedov and V.P. Lyalyalein. Development of plasma welding and surfacing abroad [J]. Welding International,1998,77 (9):54-57.
[19]T. Raymond and E. Slater. The Plasma Advantage in Automated Welding [J]. Welding Journal.1998,77 (9):54-57.
[20]E. Halmoy, H. Fostervoll and A. R. Ramsland. New Applications of Plasma Keyhole Welding [J]. Welding in the World.1994,34:284-291.
[21]D.S. Howse. Keyhole Plasma Welding of Carbon Steel Sheet [R]. TWI Research Report.1997,608.
[22]L.S. Smith and P.L. Threadgill. Keyhole Plasma Welding of a Cast Gamma Titanium Aluminium Alloy [R]. TWI Research Report.1998,659.
[23]L.S. Smith and M.F. Gittos. Formation of 'Tramlines' on Arc Welds and Back Face Oxidation of Keyhole Plasma Welds in Titanium and Its Alloys [R]. TWI Research Report.1998,661.
[24]E. Kirenskii, etal. Selecting the Optimum Parameters of Welding Plasma Torches [J]. Welding International.1995,9(7):581-582.
[25]R.M. Gage, Arc Torch and Process [P]. United States Patent Office, No. 2806124, Sept.10,1957.
[26]中国机械工程学会焊接学会,焊接手册(第二版)第1卷焊接方法及设备[M].北京：机械工程出版社,2001.
[27]S.P. Filipski. Plasma arc welding [J]. Welding Journal,1964,43(11):937-943.
[28]J.C. Metcalfe and M.B.C. Quiley. Heat transfer in plasma-arc welding [J]. Welding Journal,1975,54(3):99-s-103-s.
[29]N.J. Woodward, I.M. Richardson and A. Thomas. Variable polarity plasma arc welding of 6.35mm Aluminium alloys:parameter development and preliminary analysis [J]. Science and Technology of Welding and Joining,2000,5(1):21-25.
[30]A.C. Nunes. Variable polarity plasma arc welding on the space shuttle external tank [J]. Welding Journal,1984,63(9):27-35.
[31]M. Tomsic and S. Barhorst. Keyhole plasma arc welding of aluminum with variable polarity power [J]. Welding Journal,1984(2):24-32.
[32]Md. lbrahim Khan. Welding Science and technology [M]. New Delhi:New Age International Publishers,2007.
[33]A.C. Nunes. Welding as science:Applying basic engineering principles to the discipline [R].NASA/TM-2010-216449:ppl4-17.
[34]J.K. Martikainen and T.J.I. Moisio. Investigation of the effect of welding parameters on weld quality of plasma arc keyhole welding of structural steels [J]. Welding Journal,1993(7):329s-340s.
[35]周大中.强压缩无双弧等离子焊接的可行性[J].焊接,1980(3)：12-14.
[36]周大中等.等离子弧焊接双弧的形成过程[J].焊接,1979(2)：2-5.
[37]Kunio Narita. Plasma arc welding of pipelines:A study to optimize welding conditions for horizontal fixed joints of mild steel pipes [J]. International Journal of Pressure Vessels and Piping,1975(3):233-266.
[38]T. Ishida. Interfacial phenomena of plasma arc welding of mild steel and aluminum [J]. Journal of Material Science,1987,22:1061-1066.
[39]A. Short, D.G. McCartney, P. Webb and E. Preston. Parametric envelopes for keyhole plasma arc welding of a titanium alloy [C]. Proceedings of the 8th International Conference on Trends in Welding Research, Pine Mountain, Georgia USA, June 2-6,2008, pp 690-696.
[40]YAMAGUCHI, Yoshihiro Ishikawa Ken, Alvin Kenneth Farmington. Plasma arc spot welding of car body [P]. EUROPEAN PATENT SPECIFICATION: 98929578.7.
[41]Alvin Kenneth Oros ect. Plasma arc spot welding of car body steels containing vaporizable ingredients [P]. United States Patent Office, No. US5938948, Jul.21, 1997.
[42]Yoshitaka Niigaki, Toshiya Shintani, ect. Development of One-side Plasma Arc Spot Welding System [R]. KOMATSU Technical report,2001,47(148):16-24.
[43]R.P. Walduck. Development of a Robo tic Plasma Arc Spot Welding Technique for Jaguar Cars [J]. Welding & Metal Fabricat ion,1994,62(2):51-54.
[44]刘希贤.铝合金薄板等离子弧点焊设备[J].焊接技术,1992(01)：48.
[45]周大中,曲晨.镀锌钢板等离子弧点焊[J].焊接,1986(01)：12-17.
[46]W.F. McGee, D.J. Rybicki, D.J. Waldron. Ternary Gas Plasma Welding Torch [P]. United States Patent:No.5399831.
[47]K. Tsuchiya, K. Kishimoto, T. Matsunaga and E. Nakano. Plasma arc welding for thick plate (Part 1) [J]. Japan welding society,1973:554-566.
[48]G. Aston and M.B. Aston. Electrodeless Plasma Welding [C]. Proceedings of the 5th International Conference on Trends in Welding Research, Georgia, USA, June,1-5,1998:265-270.
[49]康健,吴永泰.真空磁压缩等离子弧焊接方法的研究[J].焊接学报,1987,8(1)：17-21.
[50]Y.M. Zhang and S.B. Zhang. Double sided arc welding increases weld joint penetration [J]. Welding Journal,1998(6):57-61.
[51]Y. M. Zhang, S. B. Zhang and M. Jiang. Keyhole double-sided arc welding process [J]. Welding Journal,2002(11):249-s-254-s.
[52]Y.M. Zhang, S.B. Zhang and M. Jia. Sensing and control of double-side arc welding [J]. Journal of Manufacturing Science and Engineering,2002,124:694-701.
[53]K. Qian and Y.M. Zhang. Optimal model predictive control of plasma pipe welding process[C],4th IEEE Conference on Automation Science and Engineering,2008:Key Bridge Marriott, Washington DC, USA.
[54]Kun Qian. Real-time model predictive control of quasi-keyhole pipe welding [D]. Kentucky:University of Kentucky Doctoral Dissertations,2010.
[55]A. Mahrle, M. Schnick, S. Rose, C. Demuth, E. Beyer and U. Fussel. Process characteristics of fibre-laser-assisted plasma arc welding [J]. Journal of Physics D:Applied Physics,2011,44:345502(12pp).
[56]Achim Mahrle, Sascha Rose, Michael Schnick, Eckhard Beyer and Uwe Fussel. Laser-assisted plasma arc welding of stainless steel [J]. Journal of Laser Applications,2013,25(3):032006 (8pp).
[57]X.R. Li, J. Heusman, L. Kvidahl, P. Hoyt and Y.M. Zhang. Manual keyhole plasma arc welding with application [J]. Welding Journal,2011,90:258-s-264-s.
[58]X.R. Li, Z. Shao and Y.M. Zhang. Double stage plasma arc pipe welding process [J]. Welding Journal,2012,91:346-s-353-s.
[59]Jukka Martikainen. On the effects of welding parameters on weld quality of plasma arc keyhole welding of structural steels [D]. Lappeenranta:Thesis for the degree of Doctor of Technology in Lappeenranta University of Technology, 1989,11.
[60]J.K. Martikainen. Investigation of the effect of welding parameters on weld quality of plasma arc keyhole welding of structural steels [J]. Welding Journal, 1993,72(7):329-s-340-s.
[61]Petteri Jernstrom. The effects of real-time control of welding parameters on weld quality in plasma arc keyhole welding [D]. Lappeenranta:Thesis for the degree of Doctor of Technology in Lappeenranta University of Technology,2000,11.
[62]Emad Saad, Huijun Wang and Radovan Kovacevic. Classification of molten pool modes in variable polarity plasma arc welding based on acoustic signature[J]. Journal of Materials Processing Technology,2006,174:127-136.
[63]H. Wang and R. Kovacevic. Feasibility study of acoustic sensing for the welding pool mode in variable-polarity plasma arc welding [J]. Proceedings of the Institution of Mechanical Engineers, Part B:Journal of Engineering Manufacture, 2002,216(10):1354-1366.
[64]王耀文,陈强,孙振国,孙久文,王海燕.等离子弧焊接穿孔行为的声信号传感[J].机械工程学报,2001,37(1)：53-56.
[65]Yaowen Wang, Qiang Chen. Relationship between sound signal and weld pool status in plasma arc welding [J]. Transactions of Nonferrous Metals Society of China,2001, 11(1):54-57.
[66]黄从达,胡百僖,陶爱龙等.锅炉蛇型管等离子弧声控焊的微型计算机控制[J].电焊机,1984(3)：10-14.
[67]胡百僖,黄从达等.利用声音信号进行脉冲等离子弧全位置焊接质量控制系统的研究[J].焊接,1980(5)：17-20.
[68]Check PA-welding penetration [J]. Welding Design & Fabrication.1991,(7):14.
[69]代大山,宋永伦,张慧,朱轶峰.等离子电弧力的研究[J].焊接学报,2002,23(2)：51-54.
[70]贾昌申,肖克民,殷咸青.焊接电弧的等离子流力[J].焊接学报,1994,15(2)：101-106.
[71]姜炜,徐滨士,吕耀辉,刘存龙.变极性等离子电弧压力的径向分布[J].焊接学报,2010,31(11)：17-20.
[72]L.F. Martinez. Front Side Keyhole Detection in Aluminum Alloys [J]. Welding Journal,1992,71(5):49-52.
[73]董春林,吴林等.不锈钢等离子弧焊熔池小孔行为的弧光传感研究[J].机械工程学报,1999,35(6)：48-51.
[74]Chunlin Dong, Lin Wu. Front side keyhole detection in plasma arc welding of stainless steel [J]. China Welding,1999,8(2):102-110.
[75]董春林,朱轶峰等.穿孔等离子弧焊正面弧光传感技术研究[J].机械工程学报,2001,37(3)：30-33.
[76]Defu He and I. Katsunori. Penetration-self-adaptive free-frequency pulsed plasma arc welding process controlled with photocell sensor [J]. Transactions of JWRI,1984,13(1):7-11.
[77]Masao Ushio. Arc discharge and electrode phenomena [J]. Pure and Applied Chemistry,1988,60(5):809-914.
[78]ChuanBao Jia, ChuanSong Wu and YuMing Zhang. Sensing controlled pulse key-holing condition in plasma arc welding [J]. Transactions of Nonferrous Metals Society of China,2009,19:341-346.
[79]H.D. Steffens and H. Kayer. Automatic control for plasma arc welding with constant keyhole diameter [J]. Welding Journal,1972,51(6):408-418.
[80]S.B. Zhang and Y.M. Zhang. Efflux plasma charge-based sensing and control of joint penetration during keyhole plasma arc welding [J]. Welding Journal,2001, 80(2):157-162.
[81]J.C. Metalfe. An initial assessment of an efflux plasma control system for plasma arc welding [C]. IIW Doc.212-397-77.
[82]林谦生.大电流等离子弧焊电流自适应控制的研究[J].焊接,1986(6)：4-7.
[83]C.S. Wu, C.B. Jia, and M.A. Chen. A control system for keyhole plasma arc welding of stainless steel plates with medium thickness [J]. Welding Journal, 2010,89(11):224-s-231-s.
[84]Y.M. Zhang, S.B. Zhang and Y.C. Liu. A plasma cloud charge sensor for pulse keyhole process control [J]. Measurement Science and Technology,2001(12): 1365-1370.
[85]马立,胡绳荪,朱玉欣,殷凤良.脉冲等离子弧焊穿孔熔池的等离子云传感[J].焊接学报,2006,27(2)：73-76.
[86]单平,易小林,胡绳荪,罗震.穿孔等离子弧焊接中等离子云的检测[J].2003,24(2)：19-26.
[87]易小林,单平,胡绳荪.等离子弧焊中小孔检测的研究[J].焊接技术,2003,32(1)：12-14.
[88]宋东风,胡绳荪,孔祥芬.等离子弧焊小孔行为的反翘电压检测[J].焊接学报,2005,26(3)：67-69.
[89]孔祥芬.等离子弧焊接熔透控制信息检测与分析[D].天津：天津大学硕士学位论文,2004.
[90]柴国明,朱轶峰.穿孔等离子弧焊接中等离子云电流的产生机制及简化模型[J].机械工程学报,2006,42(1)：178-180.
[91]王海燕,陈强,孙振国,王耀文.等离子焊接熔池小孔尺寸的电弧信号检测[J].焊接学报,2000,21(3)：24-26.
[92]Qiang Chen, Zhenguo Sun, Jiuwen Sun, Yaowen Wang. Closed-loop control of welding penetration in keyhole plasma arc welding [J]. Transactions of Nonferrous Metals Society of China,2004,14(1):116-120.
[93]T. Hoffman. Real-time imaging for process control [J]. Advanced Material & Processes 1991(3):37-43.
[94]B. Zhang, H.J. Wang, Q.L. Wang and R. Kovacevic. Control for weld penetration in VPPAW of aluminum alloys using the front weld pool imaging signal[J]. Welding Journal,2000(12):363-s-371-s.
[95]B. Zhang, H.J. Wang, Q.L. Wang and R. Kovacevic. Imaging the Keyhole in PAW of Aluminum Alloys [J]. Transactions of the ASME,1999,121(8):372-377.
[96]H. Wang and R. Kovacevic. On-line monitoring of the keyhole welding pool in variable polarity plasma arc welding [J]. Proceedings of the Institution of Mechanical Engineers, Part B:Journal of Engineering Manufacture,2002,216: 1264-1276.
[97]Y.M. Zhang and S.B. Zhang. Observation of the keyhole during plasma arc welding [J]. Welding Journal,1999,78:53-s-58-s.
[98]S.B. Zhang and Y.M. Zhang. Stability of keyhole in plasma arc welding [J]. Proceedings of the Institution of Mechanical Engineers, Part B:Journal of Engineering Manufacture,2000,214:401-405.
[99]R.C. Ashauerand S. Goodman. Automatic plasma arc welding of square butt pipe joints [J]. Welding Journal,1967,46(5):404-415.
[100]F. Rienke and R.C. Ashauer. Development and evaluation of modulated power control for fusion welding [R]. General Dynamic Electric Boat Division, Groton, Connecticut.
[101]A.V. Petrov and G.A. Slavin. An investigation into the technological possibilities of the pulsed arc[J]. Svarochnoye Priozvodstvo,1966,13(2).
[102]C.D. Lundin and W.J. Ruprecht. Pulsed current plasma arc welding [J]. Welding Journal,1974,53(1):11-19.
[103]朱轶峰,张慧,邵亦陈,董春林.脉冲等离子弧焊接工艺研究[J].等离子加工技术,1999增刊：44-48.
[104]Y.M. Zhang and Y.C. Liu. Modeling and control of quasi-keyhole arc welding process [J]. Control Engineering Practice,2003(11):1401-1411.
[105]W. Lu, Y.M. Zhang and W.Y. Lin. Nonlinear interval model control of quasi-keyhole arc welding process [J]. Automatic,2004,40:804-813.
[106]Y.M. Zhang and Y.C. Liu. Control of dynamic keyhole welding process [J]. Automatic,2007,43:876-884.
[107]C.S. Wu, C.B. Jia and M.A. Chen. Effects of controlled pulse current waveform on key-holing condition in plasma arc welding [J]. China Welding, 2010(2):12-16.
[108]C.B. Jia, C.S. Wu and Y.M. Zhang. Sensing controlled pulse key-holing condition in plasma arc welding [J]. Transactions of Nonferrous Metals Society of China,2009,19:341-346.
[109]刘祖明,武传松,陈茂爱.受控脉冲穿孔PAW对接焊过程控制的试验研究[J].机械工程学报,2011,47(3)：44-50.
[110]Y.M. Zhang and Y. Ma. Stochastic modeling of plasma reflection during keyhole arc welding [J]. Measurement Science and Technology,2001(12):1964-1975.
[111]G.J. Zhang. Machine vision [M]. Beijing:Science Press.2005.
[112]Z. Wang, Y.M. Zhang and L. Wu. Measurement and estimation of weld pool surface depth and weld penetration in pulsed gas metal arc welding [J]. Welding Journal,2010,89:117-126-s.
[113]J.C. Metcalfe and M.B.C. Quiley. Keyhole stability in plasma arc welding. Welding Journal,1975,54(11):401-s-404-s.
[114]J. Kroos, U. Gratzke and G. Simon. Towards a self-consistent model of the keyhole in penetration laser beam welding [J]. Journal of Physics D:Applied Physics,1993,26:474-480.
[115]J. Dowden, P. Kapadia and B. Fenn. Space charge in plasma arc welding and cutting [J]. Journal of Physics D:Applied Physics,1993,26:1214-1223.
[116]M.J. Tomsic and C.E. Jackson. Energy distribution in keyhole mode plasma arc welds [J]. Welding Journal,1974,53(3):109-s-114-s.
[117]R.G. Keanini and B. Rubinsky. Plasma arc welding under normal and zero gravity [J]. Welding Journal,1990,69(6):41-50.
[118]Charn-Jung Kim, Sangken Kauh, Sung Tack Ro and Joon Sik Lee. Parametric study of the two-dimensional keyhole model for high power density welding processes [J]. Journal of Heat Transfer,1994,116(1):208-214.
[119]P.S. Wei and W.H. Giedt. Surface tension gradient-driven flow around an electron beam welding cavity [J]. Welding Journal,1985,61(6):1754-1815.
[120]Y.K. Liu and Y.M. Zhang. Model-based Predictive Control of Weld Penetration in Gas Tungsten Arc Welding[J]. IEEE Transactions on Control Systems Technology, in press,2013.
[121]Zhijiang Wang, YuMing Zhang, Lin Wu. Adaptive interval model control of weld pool surface in pulsed gas metal gas welding [J]. Automatica,2012,48: 233-238.
[2]潘际銮.二十一世纪焊接科学研究的展望[C].第九次全国焊接技术会议论文集,第一册,天津,1999年11月：D001-017.
[3]T.W. Eagar. Welding and joining:moving from art to science [J]. Welding Journal,1995,74(6):49-55.
[4]S.A. David and T. DebRoy. Current issues and problems in welding science [J]. Science,1992,257 (24):497-502.
[5]K.A. Persson. Welding and cutting beyond the year 2000 [J]. Svetsaren,1999, 54(1):74-76.
[6]戴为志.从“鸟巢”钢结构焊接工程看钢结构焊接技术发展趋势[J].现代焊接,2007(9)：J-1-J-8.
[7]Bob Turpin, Dan Danks, John Callahjan and William Wood. Narrow gap electro slag is process of choice for welding San Francisco Oakland Bay bridge[J]. Welding Journal,2012(6):24-31.
[8]何庆中,袁宏远.多层包扎压力容器包扎焊接制造工艺改进[J].压力容器,2008(10)：44-48.
[9]B. Irving. Why aren't airplane welded [J]. Welding Journal,1997,76(1):34-41.
[10]P.F. Mendez. New trends in welding in the aeronautic industry [C]. New Trends for the manufacturing in the Aeronautic Industry. San Sebatian, Spain, May 24-25,2000:21-38.
[11]关桥.我国现代运载工具制造工程中的特种焊接技术[A].与时俱进、追求卓越-中国机械工程学会焊接学会四十周年、中国焊接协会十五周年纪念文集[C].2002.
[12]陈家本,郑惠锦,朱若凡,顾长石.中国船舶焊接技术进展[J].焊接,2007(5)：1-6.
[13]李轶非,王梁等.NiCrMoV耐热钢贝氏体焊缝韧性薄弱区的确定[J].机械工程学报,2013,49(4)：83-88.
[14]杨广臣,薛忠明,张彦华.厚板多层多道焊角变形分析方法[J].焊接学报,2004(1)：114-118.
[15]J.F. Lancaster. High power density welding. The physics of welding, chpt.8 [M]. 1984, Perganon Press, Oxford.
[16]C.M. Banas. Electron beam, laser beam and plasma arc welding studies[R]. NASA Contractor Report (NASA CR-132386), March 1974.
[17]E. Craig. The plasma arc process-A review [J]. Welding Journal,1988,67(2): 19-25.
[18]B.B. Nefedov and V.P. Lyalyalein. Development of plasma welding and surfacing abroad [J]. Welding International,1998,77 (9):54-57.
[19]T. Raymond and E. Slater. The Plasma Advantage in Automated Welding [J]. Welding Journal.1998,77 (9):54-57.
[20]E. Halmoy, H. Fostervoll and A. R. Ramsland. New Applications of Plasma Keyhole Welding [J]. Welding in the World.1994,34:284-291.
[21]D.S. Howse. Keyhole Plasma Welding of Carbon Steel Sheet [R]. TWI Research Report.1997,608.
[22]L.S. Smith and P.L. Threadgill. Keyhole Plasma Welding of a Cast Gamma Titanium Aluminium Alloy [R]. TWI Research Report.1998,659.
[23]L.S. Smith and M.F. Gittos. Formation of 'Tramlines' on Arc Welds and Back Face Oxidation of Keyhole Plasma Welds in Titanium and Its Alloys [R]. TWI Research Report.1998,661.
[24]E. Kirenskii, etal. Selecting the Optimum Parameters of Welding Plasma Torches [J]. Welding International.1995,9(7):581-582.
[25]R.M. Gage, Arc Torch and Process [P]. United States Patent Office, No. 2806124, Sept.10,1957.
[26]中国机械工程学会焊接学会,焊接手册(第二版)第1卷焊接方法及设备[M].北京：机械工程出版社,2001.
[27]S.P. Filipski. Plasma arc welding [J]. Welding Journal,1964,43(11):937-943.
[28]J.C. Metcalfe and M.B.C. Quiley. Heat transfer in plasma-arc welding [J]. Welding Journal,1975,54(3):99-s-103-s.
[29]N.J. Woodward, I.M. Richardson and A. Thomas. Variable polarity plasma arc welding of 6.35mm Aluminium alloys:parameter development and preliminary analysis [J]. Science and Technology of Welding and Joining,2000,5(1):21-25.
[30]A.C. Nunes. Variable polarity plasma arc welding on the space shuttle external tank [J]. Welding Journal,1984,63(9):27-35.
[31]M. Tomsic and S. Barhorst. Keyhole plasma arc welding of aluminum with variable polarity power [J]. Welding Journal,1984(2):24-32.
[32]Md. lbrahim Khan. Welding Science and technology [M]. New Delhi:New Age International Publishers,2007.
[33]A.C. Nunes. Welding as science:Applying basic engineering principles to the discipline [R].NASA/TM-2010-216449:ppl4-17.
[34]J.K. Martikainen and T.J.I. Moisio. Investigation of the effect of welding parameters on weld quality of plasma arc keyhole welding of structural steels [J]. Welding Journal,1993(7):329s-340s.
[35]周大中.强压缩无双弧等离子焊接的可行性[J].焊接,1980(3)：12-14.
[36]周大中等.等离子弧焊接双弧的形成过程[J].焊接,1979(2)：2-5.
[37]Kunio Narita. Plasma arc welding of pipelines:A study to optimize welding conditions for horizontal fixed joints of mild steel pipes [J]. International Journal of Pressure Vessels and Piping,1975(3):233-266.
[38]T. Ishida. Interfacial phenomena of plasma arc welding of mild steel and aluminum [J]. Journal of Material Science,1987,22:1061-1066.
[39]A. Short, D.G. McCartney, P. Webb and E. Preston. Parametric envelopes for keyhole plasma arc welding of a titanium alloy [C]. Proceedings of the 8th International Conference on Trends in Welding Research, Pine Mountain, Georgia USA, June 2-6,2008, pp 690-696.
[40]YAMAGUCHI, Yoshihiro Ishikawa Ken, Alvin Kenneth Farmington. Plasma arc spot welding of car body [P]. EUROPEAN PATENT SPECIFICATION: 98929578.7.
[41]Alvin Kenneth Oros ect. Plasma arc spot welding of car body steels containing vaporizable ingredients [P]. United States Patent Office, No. US5938948, Jul.21, 1997.
[42]Yoshitaka Niigaki, Toshiya Shintani, ect. Development of One-side Plasma Arc Spot Welding System [R]. KOMATSU Technical report,2001,47(148):16-24.
[43]R.P. Walduck. Development of a Robo tic Plasma Arc Spot Welding Technique for Jaguar Cars [J]. Welding & Metal Fabricat ion,1994,62(2):51-54.
[44]刘希贤.铝合金薄板等离子弧点焊设备[J].焊接技术,1992(01)：48.
[45]周大中,曲晨.镀锌钢板等离子弧点焊[J].焊接,1986(01)：12-17.
[46]W.F. McGee, D.J. Rybicki, D.J. Waldron. Ternary Gas Plasma Welding Torch [P]. United States Patent:No.5399831.
[47]K. Tsuchiya, K. Kishimoto, T. Matsunaga and E. Nakano. Plasma arc welding for thick plate (Part 1) [J]. Japan welding society,1973:554-566.
[48]G. Aston and M.B. Aston. Electrodeless Plasma Welding [C]. Proceedings of the 5th International Conference on Trends in Welding Research, Georgia, USA, June,1-5,1998:265-270.
[49]康健,吴永泰.真空磁压缩等离子弧焊接方法的研究[J].焊接学报,1987,8(1)：17-21.
[50]Y.M. Zhang and S.B. Zhang. Double sided arc welding increases weld joint penetration [J]. Welding Journal,1998(6):57-61.
[51]Y. M. Zhang, S. B. Zhang and M. Jiang. Keyhole double-sided arc welding process [J]. Welding Journal,2002(11):249-s-254-s.
[52]Y.M. Zhang, S.B. Zhang and M. Jia. Sensing and control of double-side arc welding [J]. Journal of Manufacturing Science and Engineering,2002,124:694-701.
[53]K. Qian and Y.M. Zhang. Optimal model predictive control of plasma pipe welding process[C],4th IEEE Conference on Automation Science and Engineering,2008:Key Bridge Marriott, Washington DC, USA.
[54]Kun Qian. Real-time model predictive control of quasi-keyhole pipe welding [D]. Kentucky:University of Kentucky Doctoral Dissertations,2010.
[55]A. Mahrle, M. Schnick, S. Rose, C. Demuth, E. Beyer and U. Fussel. Process characteristics of fibre-laser-assisted plasma arc welding [J]. Journal of Physics D:Applied Physics,2011,44:345502(12pp).
[56]Achim Mahrle, Sascha Rose, Michael Schnick, Eckhard Beyer and Uwe Fussel. Laser-assisted plasma arc welding of stainless steel [J]. Journal of Laser Applications,2013,25(3):032006 (8pp).
[57]X.R. Li, J. Heusman, L. Kvidahl, P. Hoyt and Y.M. Zhang. Manual keyhole plasma arc welding with application [J]. Welding Journal,2011,90:258-s-264-s.
[58]X.R. Li, Z. Shao and Y.M. Zhang. Double stage plasma arc pipe welding process [J]. Welding Journal,2012,91:346-s-353-s.
[59]Jukka Martikainen. On the effects of welding parameters on weld quality of plasma arc keyhole welding of structural steels [D]. Lappeenranta:Thesis for the degree of Doctor of Technology in Lappeenranta University of Technology, 1989,11.
[60]J.K. Martikainen. Investigation of the effect of welding parameters on weld quality of plasma arc keyhole welding of structural steels [J]. Welding Journal, 1993,72(7):329-s-340-s.
[61]Petteri Jernstrom. The effects of real-time control of welding parameters on weld quality in plasma arc keyhole welding [D]. Lappeenranta:Thesis for the degree of Doctor of Technology in Lappeenranta University of Technology,2000,11.
[62]Emad Saad, Huijun Wang and Radovan Kovacevic. Classification of molten pool modes in variable polarity plasma arc welding based on acoustic signature[J]. Journal of Materials Processing Technology,2006,174:127-136.
[63]H. Wang and R. Kovacevic. Feasibility study of acoustic sensing for the welding pool mode in variable-polarity plasma arc welding [J]. Proceedings of the Institution of Mechanical Engineers, Part B:Journal of Engineering Manufacture, 2002,216(10):1354-1366.
[64]王耀文,陈强,孙振国,孙久文,王海燕.等离子弧焊接穿孔行为的声信号传感[J].机械工程学报,2001,37(1)：53-56.
[65]Yaowen Wang, Qiang Chen. Relationship between sound signal and weld pool status in plasma arc welding [J]. Transactions of Nonferrous Metals Society of China,2001, 11(1):54-57.
[66]黄从达,胡百僖,陶爱龙等.锅炉蛇型管等离子弧声控焊的微型计算机控制[J].电焊机,1984(3)：10-14.
[67]胡百僖,黄从达等.利用声音信号进行脉冲等离子弧全位置焊接质量控制系统的研究[J].焊接,1980(5)：17-20.
[68]Check PA-welding penetration [J]. Welding Design & Fabrication.1991,(7):14.
[69]代大山,宋永伦,张慧,朱轶峰.等离子电弧力的研究[J].焊接学报,2002,23(2)：51-54.
[70]贾昌申,肖克民,殷咸青.焊接电弧的等离子流力[J].焊接学报,1994,15(2)：101-106.
[71]姜炜,徐滨士,吕耀辉,刘存龙.变极性等离子电弧压力的径向分布[J].焊接学报,2010,31(11)：17-20.
[72]L.F. Martinez. Front Side Keyhole Detection in Aluminum Alloys [J]. Welding Journal,1992,71(5):49-52.
[73]董春林,吴林等.不锈钢等离子弧焊熔池小孔行为的弧光传感研究[J].机械工程学报,1999,35(6)：48-51.
[74]Chunlin Dong, Lin Wu. Front side keyhole detection in plasma arc welding of stainless steel [J]. China Welding,1999,8(2):102-110.
[75]董春林,朱轶峰等.穿孔等离子弧焊正面弧光传感技术研究[J].机械工程学报,2001,37(3)：30-33.
[76]Defu He and I. Katsunori. Penetration-self-adaptive free-frequency pulsed plasma arc welding process controlled with photocell sensor [J]. Transactions of JWRI,1984,13(1):7-11.
[77]Masao Ushio. Arc discharge and electrode phenomena [J]. Pure and Applied Chemistry,1988,60(5):809-914.
[78]ChuanBao Jia, ChuanSong Wu and YuMing Zhang. Sensing controlled pulse key-holing condition in plasma arc welding [J]. Transactions of Nonferrous Metals Society of China,2009,19:341-346.
[79]H.D. Steffens and H. Kayer. Automatic control for plasma arc welding with constant keyhole diameter [J]. Welding Journal,1972,51(6):408-418.
[80]S.B. Zhang and Y.M. Zhang. Efflux plasma charge-based sensing and control of joint penetration during keyhole plasma arc welding [J]. Welding Journal,2001, 80(2):157-162.
[81]J.C. Metalfe. An initial assessment of an efflux plasma control system for plasma arc welding [C]. IIW Doc.212-397-77.
[82]林谦生.大电流等离子弧焊电流自适应控制的研究[J].焊接,1986(6)：4-7.
[83]C.S. Wu, C.B. Jia, and M.A. Chen. A control system for keyhole plasma arc welding of stainless steel plates with medium thickness [J]. Welding Journal, 2010,89(11):224-s-231-s.
[84]Y.M. Zhang, S.B. Zhang and Y.C. Liu. A plasma cloud charge sensor for pulse keyhole process control [J]. Measurement Science and Technology,2001(12): 1365-1370.
[85]马立,胡绳荪,朱玉欣,殷凤良.脉冲等离子弧焊穿孔熔池的等离子云传感[J].焊接学报,2006,27(2)：73-76.
[86]单平,易小林,胡绳荪,罗震.穿孔等离子弧焊接中等离子云的检测[J].2003,24(2)：19-26.
[87]易小林,单平,胡绳荪.等离子弧焊中小孔检测的研究[J].焊接技术,2003,32(1)：12-14.
[88]宋东风,胡绳荪,孔祥芬.等离子弧焊小孔行为的反翘电压检测[J].焊接学报,2005,26(3)：67-69.
[89]孔祥芬.等离子弧焊接熔透控制信息检测与分析[D].天津：天津大学硕士学位论文,2004.
[90]柴国明,朱轶峰.穿孔等离子弧焊接中等离子云电流的产生机制及简化模型[J].机械工程学报,2006,42(1)：178-180.
[91]王海燕,陈强,孙振国,王耀文.等离子焊接熔池小孔尺寸的电弧信号检测[J].焊接学报,2000,21(3)：24-26.
[92]Qiang Chen, Zhenguo Sun, Jiuwen Sun, Yaowen Wang. Closed-loop control of welding penetration in keyhole plasma arc welding [J]. Transactions of Nonferrous Metals Society of China,2004,14(1):116-120.
[93]T. Hoffman. Real-time imaging for process control [J]. Advanced Material & Processes 1991(3):37-43.
[94]B. Zhang, H.J. Wang, Q.L. Wang and R. Kovacevic. Control for weld penetration in VPPAW of aluminum alloys using the front weld pool imaging signal[J]. Welding Journal,2000(12):363-s-371-s.
[95]B. Zhang, H.J. Wang, Q.L. Wang and R. Kovacevic. Imaging the Keyhole in PAW of Aluminum Alloys [J]. Transactions of the ASME,1999,121(8):372-377.
[96]H. Wang and R. Kovacevic. On-line monitoring of the keyhole welding pool in variable polarity plasma arc welding [J]. Proceedings of the Institution of Mechanical Engineers, Part B:Journal of Engineering Manufacture,2002,216: 1264-1276.
[97]Y.M. Zhang and S.B. Zhang. Observation of the keyhole during plasma arc welding [J]. Welding Journal,1999,78:53-s-58-s.
[98]S.B. Zhang and Y.M. Zhang. Stability of keyhole in plasma arc welding [J]. Proceedings of the Institution of Mechanical Engineers, Part B:Journal of Engineering Manufacture,2000,214:401-405.
[99]R.C. Ashauerand S. Goodman. Automatic plasma arc welding of square butt pipe joints [J]. Welding Journal,1967,46(5):404-415.
[100]F. Rienke and R.C. Ashauer. Development and evaluation of modulated power control for fusion welding [R]. General Dynamic Electric Boat Division, Groton, Connecticut.
[101]A.V. Petrov and G.A. Slavin. An investigation into the technological possibilities of the pulsed arc[J]. Svarochnoye Priozvodstvo,1966,13(2).
[102]C.D. Lundin and W.J. Ruprecht. Pulsed current plasma arc welding [J]. Welding Journal,1974,53(1):11-19.
[103]朱轶峰,张慧,邵亦陈,董春林.脉冲等离子弧焊接工艺研究[J].等离子加工技术,1999增刊：44-48.
[104]Y.M. Zhang and Y.C. Liu. Modeling and control of quasi-keyhole arc welding process [J]. Control Engineering Practice,2003(11):1401-1411.
[105]W. Lu, Y.M. Zhang and W.Y. Lin. Nonlinear interval model control of quasi-keyhole arc welding process [J]. Automatic,2004,40:804-813.
[106]Y.M. Zhang and Y.C. Liu. Control of dynamic keyhole welding process [J]. Automatic,2007,43:876-884.
[107]C.S. Wu, C.B. Jia and M.A. Chen. Effects of controlled pulse current waveform on key-holing condition in plasma arc welding [J]. China Welding, 2010(2):12-16.
[108]C.B. Jia, C.S. Wu and Y.M. Zhang. Sensing controlled pulse key-holing condition in plasma arc welding [J]. Transactions of Nonferrous Metals Society of China,2009,19:341-346.
[109]刘祖明,武传松,陈茂爱.受控脉冲穿孔PAW对接焊过程控制的试验研究[J].机械工程学报,2011,47(3)：44-50.
[110]Y.M. Zhang and Y. Ma. Stochastic modeling of plasma reflection during keyhole arc welding [J]. Measurement Science and Technology,2001(12):1964-1975.
[111]G.J. Zhang. Machine vision [M]. Beijing:Science Press.2005.
[112]Z. Wang, Y.M. Zhang and L. Wu. Measurement and estimation of weld pool surface depth and weld penetration in pulsed gas metal arc welding [J]. Welding Journal,2010,89:117-126-s.
[113]J.C. Metcalfe and M.B.C. Quiley. Keyhole stability in plasma arc welding. Welding Journal,1975,54(11):401-s-404-s.
[114]J. Kroos, U. Gratzke and G. Simon. Towards a self-consistent model of the keyhole in penetration laser beam welding [J]. Journal of Physics D:Applied Physics,1993,26:474-480.
[115]J. Dowden, P. Kapadia and B. Fenn. Space charge in plasma arc welding and cutting [J]. Journal of Physics D:Applied Physics,1993,26:1214-1223.
[116]M.J. Tomsic and C.E. Jackson. Energy distribution in keyhole mode plasma arc welds [J]. Welding Journal,1974,53(3):109-s-114-s.
[117]R.G. Keanini and B. Rubinsky. Plasma arc welding under normal and zero gravity [J]. Welding Journal,1990,69(6):41-50.
[118]Charn-Jung Kim, Sangken Kauh, Sung Tack Ro and Joon Sik Lee. Parametric study of the two-dimensional keyhole model for high power density welding processes [J]. Journal of Heat Transfer,1994,116(1):208-214.
[119]P.S. Wei and W.H. Giedt. Surface tension gradient-driven flow around an electron beam welding cavity [J]. Welding Journal,1985,61(6):1754-1815.
[120]Y.K. Liu and Y.M. Zhang. Model-based Predictive Control of Weld Penetration in Gas Tungsten Arc Welding[J]. IEEE Transactions on Control Systems Technology, in press,2013.
[121]Zhijiang Wang, YuMing Zhang, Lin Wu. Adaptive interval model control of weld pool surface in pulsed gas metal gas welding [J]. Automatica,2012,48: 233-238.