At present, most welding robots used in industrial production are teach-and-playback robots. The torch path has to be taught manually before welding, this artificial teaching mode is time consuming and laborious especially in small batch production and complex shaped work-piece’s welding. Welding robots often lack adaptability, welding may fail when working environment changed. Therefore, to install visual sensors on welding robots to enable robots have the ability to obtain welding information and detect weld bias, which can improve the autonomous ability of welding robot as well as welding reliability. In this thesis, the visual tracking technology for space weld is studied, including visual measurement and welding robots tracking control. The paper’s main work is as follows: Firstly, a visual sensing system for planar weld under natural light is designed, and the robot visual servo control strategy based on image servo is studied. The position of welding torch can be rectified according to the image feature bias, so planar weld visual tracking can be implemented. Secondly, a V-groove space weld visual measurement system is designed, the position of space weld can be measured using the structure light vision sensing way. A method of the structure light plane parameters’ calibration is proposed based on stripe lines as primitive elements, the robot is controlled to move for one time, two non-coincident stripe lines on target plane are generated, then the structured light plane parameters’ calibration can be realized taking advantage of stripe lines. Thirdly, the ROI of the V-groove space weld image is determined, and a fast centerline extraction operator is designed to extract the stripe center line with a single pixel. By traversing along the stripe center line and comparing the slopes of stripe segments, two edge feature points are detected. Fitting the center points on stripe center line around two edge points by least squares line fitting method, the bottom feature point is determined. Fourthly, the position model of the space weld is established, a cubic parameter spline fitting method based on interpolation nodes is put forward which can eliminate the disturbance generated by spline fitting, the value of the interpolation nodes are estimated by analyzing the linearity of weld segments. The orientation model of the space weld is established, so the space weld’s orientation can be described. Fifthly, to meet the accuracy requirement of weldi...
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