Adaptive Control of Back Bead and Bead Height under Gap Variation in Narrow Gap Robotic Welding

如果在窄间隙中沉积的金属量变大，则焊头高度变高。在这种情况下，电弧热是在熔池上，而不是在根边。熔合不足导致了机械强度方面的问题。因此，一般来说，沉积金属的量是确定的，使珠高度小于4mm。当金属板的厚度超过12mm时，从焊接线的开始到结束需要三倍以上的火炬移动。此外，电弧行为还取决于焊接电源的特性；焊条送丝速度和焊枪运动。短弧长是保证焊接质量的必要条件。为了控制焊头高度和后焊头，提出了一种利用计算机网络对电源、焊条送丝器和焊接机器人等焊接设备进行协同控制的方法。作者不仅在焊槽上以10hz的频率摆动焊枪，而且还可以像开关一样沿编织中心来回移动，即提出了开关回焊方法。首先，作者将编织中心向前移动，通过弧线预热母材的根部边缘。稳定的后头形成而不缺乏熔合。上述焊接工艺称为正向工艺。接下来，作者将织造中心向后移动，使液滴沉积到根部边缘和凹槽表面，从而获得所需的编织高度。这被称为逆向过程。如果弧长变长，则很难将热量传递到根边，并且在接合部分发生熔合不足。为了观察熔池，使用CCD相机是有用的。但是，针对薄板焊接提出的焊池观测方法很难应用，即CCD相机的快门必须与焊枪振荡同步。在本文中，当火炬经过织布中心时，CCD相机的快门打开。在开关背焊中，有许多焊接条件的参数，如焊枪的行进速度、电流、送丝速度等。为了找到焊接条件的最佳参数，用热传导方程描述了焊池的数值模型。在数值分析中，采用有限差分法求解数值模型耗时较长。为了节省计算时间，采用模糊熔池模型代替数值模型。利用数值结果对模型进行了调整。估计最佳行程长度为4至6mm间隙。为了验证模糊模型和所提出的焊接方法的有效性，在间隙变化的情况下进行了实验。焊接效果良好，焊头表面光滑，后焊头宽。少

If the amount of the deposited metal becomes big in the narrow gap, the bead height becomes high. In this case, the arc heat is given on the weld pool and is not given to the root edge. Lack of fusion takes place and cause the problem concerning the mechanical strength. Therefore, in general, the amount of the deposited metal is determined so that the bead height is less than 4mm. It takes more than three times of the torch traveling from the beginning to the end of the welding line, when the thickness of the metal plates is over 12mm. Moreover, the arc behavior depends on the welding power source characteristic ; the electrode wire feed rate and the welding torch motion. The short arc length is necessary to get a high quality of the welding.In order to control the bead height and the back bead, authors propose a cooperative control method of the welding equipments including the power source, the electrode wire feeder and the welding robot by using the computer network.Authors try to n … More ot only oscillate the welding torch on the groove at 10 Hz, but also move along the weaving centre back and forth like switch back, i.e., authors propose the switch back welding method.First, the authors move the weaving centre forward, to pre-heat the root edges of the base metal by the arc. The stable back bead is formed without the lack of fusion. The mentioned welding process is called forward process. Next, the authors move weaving centre backward to deposit droplets to the root edges and to the groove surface, so that the desired bead height is obtained. This is called backward process. If the arc length becomes long, it is difficult to give the heat to the root edge and a lack of fusion in the joint part takes place. In order to observe the weld pool, it is useful to use a CCD camera. But, it is difficult to apply the observation method of the weld pool, which is proposed for thin plate welding, i.e., it is important that the shutter of the CCD camera is synchronized with torch oscillating. In this paper, the shutter of the CCD camera is opened when the torch passes on the centre of the weaving. In the switch back welding, there are many parameters of welding conditions, such as traveling speed of the torch, the current, the wire feed rate and so on. To find the optimum parameters of the welding conditions, the numerical model of the weld pool is described by using an equation of heat conduction. It takes long time to solve the numerical model by applying the finite difference in a numerical analysis. In stead of the numerical model, the fuzzy model of the weld pool is proposed to save the calculation time. Its model is adjusted by using the numerical results. The optimum stroke length is estimated from 4 to 6mm gap. In order to verify the validity of the fuzzy model and the proposed welding method, the experiment is carried out under the variation of the gap. A good result of the welding can be obtained, i.e., the smooth surface bead and wide back bead are obtained. Less