Development, optimization, and evaluation of a hybrid passive buoyancy compensation system for underwater gliders

Abstract

Underwater glider (UG) is one of the most promising devices for ocean sampling. However, when the UG is operating in a vast ocean space, its performance in terms of motion stability, energy efficiency and endurance is affected due to the buoyancy variation caused by the change of displacement and seawater density. It is essential to compensate for the buoyancy variation for performance improvement of the UG. This paper proposes a hybrid passive buoyancy compensation system (HPBCS), integrating three standalone buoyancy compensation devices of spring accumulator, inflatable accumulator, and silicon oil bladder, to compensate for the buoyancy variation. The mathematic compensation model of this system is established and an effective optimization algorithm hybridizing genetic algorithm and tabu search method is adopted to optimize the design parameters. The case study of a Petrel-II underwater glider shows that the optimal HPBCS can significantly improve the buoyancy compensation. Then the motion stability, energy efficiency and endurance of the UG with HPBCS are evaluated and compared with those of other UGs. Results indicate that the UG with HPBCS has a more superior performance in motion stability and energy efficiency, but its endurance is affected by the mass brought by HPBCS.