Positioning method for laser welding systems based on side-axis vision

In response to the suboptimal calibration results in laser welding, as well as significant discrepancies between the positioning accuracy and pixel equivalence, a camera calibration method and positioning approach based on side-axis vision were proposed on the basis of a self-developed laser welding system in the laboratory. The method involved the calibration of intrinsic parameters to correct lens distortion and the calibration of extrinsic parameters to establish the transformation relationship between the pixel coordinate system and the machine tool coordinate system. Additionally, a locally optimized algorithm for binary thresholding was designed to ensure accurate edge fitting of workpieces. The placement position and orientation of the workpiece in the system were determined through the identification of workpiece corner and the angle of one side, with the algorithm achieving a stable accuracy within 1 pixel, equivalent to a theoretical precision of 0.017 mm. Experimental testing of positioning accuracy involved the correction of recognized workpiece rotation angles. Prior to correction, the average errors in the x and y directions were 0.050 mm and 0.137 mm, respectively. After correction, the average errors were reduced to 0.029 mm in the x direction and 0.026 mm in the y direction, corresponding to multiples of pixel equivalence of 2.12 and 1.53, respectively. The actual errors exhibited minimal differences in multiples with pixel equivalence. The results indicated that this positioning method, while fully leveraging the camera's performance, demonstrated high algorithmic and positioning accuracy, enhancing processing efficiency and meeting practical production requirements.