设计了一套厚板窄间隙磁控电弧惰性气体保护( TIG) 焊接自动控制系统，介绍了通过交变磁场控制电弧周期性左右偏转以消除侧壁未熔合缺陷的原理． 以可编程控制器
( PLC) 作为控制核心，根据该工艺的特点对控制系统进行了总体设计． 设置两套独立的电弧长度控制系统，分别用于控制钨极处于间隙的居中位置和处于相对稳定的高度; 设计并建立了一套运动控制系统; 利用高精度气体传感器检测和控制各路保护气的实际流量，同时对保护气拖罩与工件表面之间的距离进行实时检测和控制，实现对厚板焊接过程的有效保护; 对焊接电源进行选型及改造以实现数字化控制; 搭建适用于工业化生产的视频监控系统． 针对大厚板钛合金的焊接试验表明，该系统运行稳定可靠，具备在工业领域进行推广的潜力．

In the investigation,first,an automatic control system of narrow-gap magnetic controlled tungsten inert gas ( TIG) arc welding for thick plates is designed,and the principle of avoiding the defect of incomplete penetration on side walls by adopting an alternatively-changed magnetic field to deflect welding arc towards left or right periodically is introduced.Next,by taking a programmable logic controller ( PLC) as the core and based on its characteristic,a control system is overall designed,and two independent arc length control systems are designed to keep the tungsten electrode exactly in the middle of the gap and at a relatively constant height.Then,a sensing and motion control system is designed and established,and effective protection of weld seam is realized by employing high-precision gas sensors to detect and control the actual flow rate of shielding gas and by implementing the realtime measurment and control of the distance between the shielding covering and the substrate.Finally,a suitable welding power source is selected and modified to realize a digital control,and a vision monitoring system for industry is set up.The results of welding experiments on thick titanium plates demonstrate that the designed automatic control system is reliable and stable,and it has the potentiality to be promoted in industry.