(A) study on the vision sensor for automatic welding of height-varying weldments

Abstract

Among various types of sensors used in welding automation, the arc and vision sensors are widely used for automatic seam tracking and quality control of arc welding processes. The development of a vision sensor which can provide 3D geometry information is needed especially for robot guidance in automatic welding of thin plates, because it is difficult to apply an arc sensor to the welding of thin plates. Vision sensors using optical triangulation have been widely used in various ways for automatic welding systems. The separation angle between the camera and the laser axis has been mainly considered in previous studies of the vision sensor with structured light. Their measuring efficiency is, however, considerably influenced by the different arrangements of the weldment, the CCD camera, and a diode laser of a vision sensor in three-dimensional space. Therefore to enhance the effectiveness of a vision sensor for height-varying workpieces, other geometrical parameters such as diagonal and tilt angles should also be investigated. In the present study, the data deficiency in the vision sensor fell into two classifications: the shadow effect and the missing field of view (FOV), and a mathematical model was proposed to estimate the occurrence of data deficiency. Many efforts have been made to develop an automatic welding system in order to improve the quality and productivity in welding shipping containers and LNG(Liquefied Natural Gas) storage tanks which consist of many sheet metals having linear weldments with height variation. However it is difficult to determine the proper configuration of sensory system including a CCD camera and diode laser to specific weldments because of the interference and relative motion among vision sensor, welding torch and weldment. Therefore, to develop a vision sensor with high performance for a specific workpiece, the sensory system should be analyzed for various configurations of sensors and weldment shapes by using a mathematical ...