Fig. 1. Laser-MIG hybrid welding process detection system

Fig. 2. Weld forming width extraction with second-order difference method

Fig. 3. Laser-MIG hybrid welding process image captured by high-speed camera

Fig. 4. Three-dimensional grayscale image of welding process

Fig. 5. Processing of laser -MIG hybrid welding molten pool image. (a) Extraction of region of interest (ROI); (b) mark of a molten pool; (c) image segmentation with watershed algorithm; (d) morphological processing

Fig. 6. Comparison of measured and true weld widths

Fig. 7. Comparison of BP neural network compensation Kalman filter (BP-KF) and Kalman filter (KF) values

Fig. 8. Absolute error values between true weld widths and the estimated value of BP-KF and KF