Intelligent Adaptive Control for Weld Penetration by Monitoring Shape and Oscillation of Molten Pool

在钢板焊接中，坡口形状、板厚、焊接速度等焊接参数随时间变化。因此，根据焊接工艺参数的变化进行控制，选择最优的焊接工艺条件是非常重要的。为了实现焊接条件的自适应控制，构建了新的控制系统。第一个系统采用安装在焊枪背面的CCD摄像机，对熔池状况进行监测。特别是，在焊接过程中测量了熔池的形状和尺寸，并进行了过程控制以保持形状和尺寸。当熔池宽度等熔池尺寸增大时，控制系统减小焊接电流，保持熔池尺寸不变。为了构造一个鲁棒的控制系统，将人工神经网络应用到该系统中。并将该系统应用于固定管道的焊接，验证了系统的有效性。第二个系统具有熔池振荡监测系统。众所周知，熔池的振荡频率随熔深的变化而变化。本研究提出了辅助气体振荡法、脉冲屏蔽气体振荡法和脉冲反辅助气体振荡法等新的振荡方法，并对这些振荡方法的特性进行了研究。结果表明，气体振荡法可以对较小尺寸的熔池进行振荡。这是传统的脉冲电流振荡方法难以振荡的。利用所构建的系统进行了焊接控制实验，验证了该系统在熔透控制中的有效性。

In welding of steel plates, the welding parameters including groove shape, plate thickness, welding speed and so on change with elapse time. Accordingly, it is very important to select the optimum welding conditions by controlling them according to change of welding parameters. In order to realize the adaptive control of welding conditions, new control systems were constructed.The first system used a CCD camera which was fixed at back side of welding torch, and it monitored the condition of the molten pool. In particular, the shape and dimension of the molten pool were measured during welding, and in-process control was performed to keep the shape and dimension. When the dimension of molten pool, such as pool width, increased, the control system decreased the welding current and keep the dimension of molten pool constant. In order to construct a robust control system, artificial neural network was applied to it. Furthermore, the system was applied to welding of fixed pipes, and effectiveness of the system was confirmed.The second system has a monitoring system of oscillation of molten pool. Already, it is well known that the oscillation frequency of the molten pool changes with penetration. In this research, new oscillating processes including assist gas oscillating method, pulse shielding gas oscillating method and pulse back assist gas oscillating method were proposed, and characteristics of these oscillating methods were investigated. As a result, it is confirmed that the gas oscillating method can oscillate a molten pool with relatively small size. which is difficult to be oscillated by the conventional pulse current oscillating method. Furthermore, welding control experiments were performed using the system constructed in this study, and the effectiveness of the system in penetration control was verified.