Abstract
The formation of hybrid underwater gliders has advantages in sustained ocean observation with high resolution and more adaptation for complicated ocean tasks. However, the current work mostly focused on the traditional gliders and AUVs. The research on control strategy and energy consumption minimization for the hybrid gliders is necessary both in methodology and experiment. A multi-layer coordinate control strategy is developed for the fleet of hybrid underwater gliders to control the gliders’ motion and formation geometry with optimized energy consumption. The inner layer integrated in the onboard controller and the outer layer integrated in the ground control center or the deck controller are designed. A coordinate control model is proposed based on multibody theory through adoption of artificial potential fields. Considering the existence of ocean flow, a hybrid motion energy consumption model is constructed and an optimization method is designed to obtain the heading angle, net buoyancy, gliding angle and the rotate speed of screw propeller to minimize the motion energy with consideration of the ocean flow. The feasibility of the coordinate control system and motion optimization method has been verified both by simulation and sea trials. Simulation results show the regularity of energy consumption with the control variables. The fleet of three Petrel-II gliders developed by Tianjin University is deployed in the South China Sea. The trajectory error of each glider is less than 2.5 km, the formation shape error between each glider is less than 2 km, and the difference between actual energy consumption and the simulated energy consumption is less than 24% actual energy. The results of simulation and the sea trial prove the feasibility of the proposed coordinate control strategy and energy optimization method. In conclusion, a coordinate control system and a motion optimization method is studied, which can be used for reference in theoretical research and practical fleet operation for both the traditional gliders and hybrid gliders.
Highlights
Nowadays, deployment of autonomous mobile vehicles or platforms has become the mainstream method in ocean observation
Autonomous underwater glider [1,2,3] (AUG) is a type of autonomous underwater vehicle (AUV), which is distinguished from scientists by its unique gliding mode
It is necessary to make efforts on the coordinate control of hybrid underwater glider (HUG) formation for its superiority in operation and control, while most researches on coordinate control strategy of fleet focused on the traditional gliders and AUVs
Summary
Deployment of autonomous mobile vehicles or platforms has become the mainstream method in ocean observation. It is necessary to make efforts on the coordinate control of HUG formation for its superiority in operation and control, while most researches on coordinate control strategy of fleet focused on the traditional gliders and AUVs. Energy saving, utilization and recycling are always concerned in practical engineering technology, especially in remoted mobile vehicles [25, 26]. 2.1 Structure and Main Parameters of Petrel‐II Petrel-II glider, shown, is a hybrid underwater glider (HUG) developed by Tianjin University, China [10, 11] It expands the capability of traditional underwater glider by the combination of gliding mode and screw propeller driven mode, which is more adaptive in harsh ocean environment and more suitable for complex task. Petrel-II glider is constructed by the following main parts: the buoyancy driven part (regulating the net buoyancy to control glider’s diving or rising), attitude adjusting and battery package
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