Small Unmanned Aerial Vehicle (sUAV) Inspections in GPS Denied Area beneath Bridges

Bridge inspections are important to proactively ensure that structures are safe for use by the traveling public. Accessibility challenges during inspections often necessitate the use of special equipment, such as under-bridge inspection vehicles, which may increase both cost and risk of inspections. Under-bridge inspection vehicles, however, cannot be used on all structures, such as load restricted structures. The objective of this research project is to develop and demonstrate a small unmanned aerial vehicle (sUAV) that can be used to perform bridge inspections that would typically require the use of under-bridge inspection vehicles. The proposed sUAV system builds off of previously conducted studies, which have faced challenges with insufficient GPS signal to fly underneath a bridge. By combining information from an optical flow sensor and a range-finding sensor, the proposed system offers a method of safely and efficiently operating underneath a bridge where a GPS signal may be denied. Additionally, the sUAV can capture images of the undersides of bridges using a top-mounted gimbal and a high-resolution camera. This paper provides an account of the methods and results of several demonstration sUAV bridge inspections. It then discusses the advantages and ongoing challenges associated with using sUAV systems to supplement bridge inspections. Finally, recommended applications for sUAV bridge inspections are provided, including periodically replacing the use of under-bridge inspection vehicles for inspections on bridges in good condition, and inspecting structures with load restrictions, especially post-impact, which may prohibit the use of under-bridge inspection vehicles.