Abstract
This paper describes the highly accurate and widely applicable tracking control system which guides a welding torch along the line of a joint. The control system includes a servomechanism, an optical image sensor and an image processing apparatus. The optical sensor consists of a He-Ne gas laser and a solid-state image sensor, and detects the cross section pattern of a welding groove using the Light-Sectioning Technique. The image processor is all but a micro-computer and processes the visual information obtained by the image sensor, and then estimates the position of the welding groove center using the statistical estimation method. The estimated data are the output of the processor and are used as reference of the servomechanism. The data are stored at the same time in the Memory because they may be used again as an objective value of tracking control according to demand.
This tracking control method has been applied to the penstock welding apparatus and to confirm its practical usefulness.
A summary of the results is shown below.
(1) The sensor mentioned in this paper is suitable for remote detection, and so has advantage. For example, the sensor is not consumed by contact and avoid of damage due to welding heat.
(2) The detection is made with a high accuracy using a micro-computer and relying on the method of statistical inference.
(3) The accuracy of the measurement can be determined arbitrarily by adjusting the magnification of the image sensor's optical system. For example, under the condition in which the image sensor views 50×50mm2 area on the steel surface, the maximum detection error is 0.22mm and the maximum tracking error is 0.34mm.
(4) This tracking control method is applicable for every groove shape and also applicable for the monitoring of a bead shape, and the measurement of a gap between two steel plates, the measurement of a flatness offset between two surfaces.
