LAUSR

Seam detecting and micro weld tracking are difficult in the laser welding process. In this paper, a micro gap weld with a width of not more than 0.05 mm is detected and identified by magneto-optical (MO) imaging technology. The MO imaging law of the micro gap weld under direct-current (DC) magnetic field excitation is studied, and the relationship between the gray-scale characteristics of the weld’s MO image and the leakage magnetic field strength is analyzed based on the MO effect law. A finite element (FE) model of the micro gap weld is set up, and the leakage magnetic field distributions of different lift-off heights and different excitation voltages are analyzed, which is helpful in improving the detection accuracy of the center position of the micro gap weld. A MO imaging inspection system for micro gap weld excited by a DC magnetic field is established. According to the finite element simulation results and the MO imaging experiments, the optimal excitation voltage of the MO imaging device is 15 V, and the optimal lift-off height is 1.0 mm. To reduce the influence of noise coupled with the laser welding process, the measurement precision of the micro gap weld center was improved by the Kalman filtering (KF) method. The experimental results at different welding speeds indicated that MO imaging can be used for high-precision micro gap weld center identification under optimal detection parameters.