Research progress on positioning methods of submersibles for underwater detection of dams in the deepwater environment

Abstract

<p indent="0mm">China has the largest number of high dams and large reservoirs and the fastest dam construction rate in the world. Many countries in Europe and America have experienced high dam and large reservoir collapse accidents or disasters caused by hidden dangers of underwater structures. Relevant experience and lessons have shown that deepwater detection, repair and reinforcement technologies, and equipment are vital for the long-term safe operation of high dams and large reservoirs. Traditional underwater detection in deepwater environments is mainly implemented by underwater unmanned submersibles equipped with optical or acoustic equipment because of the complexity of high dam structures and the particularity of reservoir environments. During the 13th Five-Year Plan period, the National Key R&amp;D Program approved and developed a manned submersible that is suitable for the deepwater environment of dams and capable of carrying experts in the dam engineering field to the deepwater environment for on-site inspection. These two underwater detection technologies and equipment are effective technologies in detecting, repairing, and reinforcing dam structures in deepwater environments, and underwater precise positioning technology is required for unmanned and manned submersibles to complete various complex underwater tasks in deepwater. First, this paper summarizes existing underwater positioning technologies and methods of unmanned submersibles. According to the principle, underwater positioning methods are divided into four categories: inertial navigation, optics, acoustics, and other methods, and the advantages and disadvantages of the various positioning methods are analyzed. Furthermore, the adaptability of different underwater positioning technologies, in addition to the complexity of the deepwater environment of high dams, is analyzed from the perspectives of safety guarantee, equipment research and development, economic benefits, etc. The use of acoustic ultra-short baseline devices, buoys, inertial positioning, and physical calibration for underwater positioning is proposed as a development trend for improving the positioning accuracy of the underwater operation of dam detection submersibles in deepwater environments. Various underwater positioning and navigation modes were rationally combined and supplemented to improve the accuracy and reliability of underwater positioning.