Abstract The change of the surface curvature during the line heating forming process of ship outer plates changes the spatial position of frame lines on the surface, which makes it challenging to locate the position of frame lines during the digital plate-forming inspection. It is necessary to establish the mapping between the frame line data of complex surface shape and the corresponding data in the two-dimensional flattening state with the help of surface flattening algorithms, so as to obtain the spatial position of the frame line data of outer plates in the actual forming state. A Dijkstra-compass intersection-solving algorithm is proposed to achieve surface flattening of ship outer plates. Firstly, the point cloud data of the outer plate shape surface is interpolated and fitted by NURBS to obtain the surface data of the outer plate. Then, the Dijkstra search algorithm is used to find the geodesic, and the frame line curvature is calculated according to the triangular similarity law. Finally, the geodesic line and the middle frame line are expanded, and the surface flattening data is obtained by further expanding the mesh points. This method is used to flatten the cylindrical and circular table surfaces, and the flattening error is less than 3mm compared with theoretical values. The test results show that the proposed method can effectively flatten the three-dimensional surface of the ship’s outer plates, and the deployment accuracy meets the actual use requirements.
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