Accurate and Reliable Sealant Inspection for Aircraft Fuel Tank Based on 3-D Point Cloud

As an important force-bearing component, aircraft fuel tank is localized at wings, fuselage, and empennage of an aircraft. To prevent the leakage or potential hazard of an aircraft fuel tank, the seal quality of fasteners on the fuel tank skin must be carefully inspected. Due to the limited space during inspection and its complex internal structures, it is challenging for current techniques to effectively inspect aircraft fuel tank. In this article, we introduce an aircraft sealant inspection system (ASInspS) to achieve accurate and reliable internal inspection for fuel tanks. For the hardware part, we utilize a high-precision 3-D scanner and a visual–inertial odometry (VIO) to acquire point clouds and poses, simultaneously. We then design three key modules to achieve the sealant inspection with high accuracy and reliability. First, the scanner positioning module aims to acquire the 6-D poses of the 3-D scanner, in which we propose two key improvements, that is, event-based mask (EvMask) and adaptive keyframe selection, to improve the robustness of feature tracking. Second, the seal area reconstruction module follows a coarse-to-fine strategy to achieve the accurate registration and then to create high-quality point cloud models of fuel tanks. Meanwhile, the results of fine alignment will be used to correct the accumulated drift error in the first module, which allows the system to ensure the high accuracy under complex scenes. Third, the sealant inspection module is built to conduct the accurate and reliable sealant measurement. The quantitative results demonstrate that our sealant inspection system can guarantee the precision (on different scales) at whatever the stage of the positioning, registration, or index measurement. The results also indicate that our ASInspS performs with high reliability even under a complex and closed aircraft fuel tank.