Seam tracking and visual control for robotic arc welding based on structured light stereovision

A real-time arc welding robot visual control system based on a local network with a multi-level hierarchy is developed in this paper. It consists of an intelligence and human-machine interface level, a motion planning level, a motion control level and a servo control level. The last three levels form a local real-time open robot controller, which realizes motion planning and motion control of a robot. A camera calibration method based on the relative movement of the end-effector connected to a robot is proposed and a method for tracking weld seam based on the structured light stereovision is provided. Combining the parameters of the cameras and laser plane, three groups of position values in Cartesian space are obtained for each feature point in a stripe projected on the weld seam. The accurate three-dimensional position of the edge points in the weld seam can be calculated from the obtained parameters with an information fusion algorithm. By calculating the weld seam parameter from position and image data, the movement parameters of the robot used for tracking can be determined. A swing welding experiment of type V groove weld is successfully conducted, the results of which show that the system has high resolution seam tracking in real-time, and works stably and efficiently. This work was supported by the National High Technology Research and Development Program of China under Grant 2002AA422160, and by the National Key Fundamental Research and the Development Project of China (973) under Grant 2002CB312200. De Xu graduated from Shandong University of Technology (SUT), China, in 1985. He received a Masters degree from SUT in 1990 and a Ph.D. degree from Zhejiang University, China, in 2001. He has been with Institute of Automation, Chinese Academy of Sciences (IACAS) since 2001. He is an associate professor with the Laboratory of Complex Systems and Intelligence Science, IACAS. His research interests include robotics and automation, especially the control of robots such as visual control and intelligent control. Min Tan graduated from Tsing Hua University, China, in 1986. He received a Ph.D. degree in 1990 from IACAS. He has been with IACAS since then. He is a professor with the Laboratory of Complex Systems and Intelligence Science, IACAS. His research interests include robotics and complex system theory. Xiaoguang Zhao graduated from Shenyang University of Technology, China, in 1992. She received a Masters degree and Ph.D. degree from Shenyang Institute of Automation, Chinese Academy of Sciences in 1998 and 2001 respectively. She is a post doctoral fellow with IACAS. Her research interests include robot control and machine vision. Zhiguo Tu graduated from Central South University, China, in 2000. He is a postgraduate with IACAS. His research interests include robot control and remote control.