Fig. 1. Laser fringe of a typical V-shaped weld

Fig. 2. Laser stripe image of weld with interference

Fig. 3. Hog characteristics of weld flex point area without interference

Fig. 4. Hog characteristics of weld flex point area with strong interference

Fig. 5. Flow chart of seam tracking algorithm based on particle filter with histogram of oriented gradient

Fig. 6. Experimental device of autonomous mobile welding robot and actual autonomous welding process, and schematic of seam tracking area. (a) Experimental device and actual autonomous welding process; (b) schematic of seam tracking area

Fig. 7. Schematics of point sets and flex points. (a) Divide the center point into four point sets; (b) left flex point of weld; (b) right flex point of weld

Fig. 8. Particle distribution map during tracking

Fig. 9. Schematics of seam tracking results

Fig. 10. Variation of tracking error with number of particles

Fig. 11. Variation of processing time of each frame image with the number of particles

Fig. 12. Diagram of seam tracking error curve

Fig. 13. Comparison charts of seam tracking

Fig. 14. Contrast of seam tracking error