Weld line detection algorithm for radiography test of welding beads in a ship piping system

Inspection of welding beads is important to achieve reliability of welding condition. Radiography testing is a widely used method in ship piping systems to verify welding quality. In our industry problem, a mobile robot was utilized to radiate X-ray outwards from inside of a pipe. Because small amount of radiation is allowed by the legal regulation, precise localization of a weld line is required. This paper proposes a robot vision algorithm to precisely localize the position of a weld line in a piping system. The proposed algorithm detects a weld line and loosely localizes the position by using a difference of Gaussian. For a sub-region that contains the loosely localized weld line, morphological operations are applied to precisely localize the position of the weld line. Experiments were conducted on real industry data to demonstrate the effectiveness of the proposed algorithm.