Fig. 1. Flow chart of flange inner diameter ellipse extraction method

Fig. 2. Framework of YOLOv4 network

Fig. 3. Schematic diagram of arc segmentation

Fig. 4. Model diagram of adaptive threshold for circular arcs

Fig. 5. Schematic diagram of arc extraction

Fig. 6. Effect of AAMED method for arc extraction

Fig. 7. Schematic diagram of filtering area

Fig. 8. Model diagram of light stripe noise

Fig. 9. Comparison diagram of unloading flange positioning before and after. (a) Original image; (b) YOLO positioning image

Fig. 10. Comparison results of flange contour extraction accuracy. (a) Diagram of discharge flange with presence of light strip noise; (b) local magnification effect; (c) AAMED method; (d) after a single screening; (e) after secondary screening; (f) after removing outliers and secondary screening

Fig. 11. Robustness test results for flange contour extraction. (a) Original image; (b) extract results; (c) right partial view; (d) left partial view