Combined Depth Control Strategy for Low-Speed and Long-Range Autonomous Underwater Vehicles

Abstract

Autonomous underwater vehicles (AUVs) are increasingly being applied to highly detailed survey and inspection tasks over large ocean regions. These vehicles are required to have underwater hovering and low-speed cruising capabilities, and energy-saving property to enable long-range missions. To this end, a combined depth control strategy is proposed in which an on-off type variable ballast system (VBS) is adopted for satisfactory hovering or fast descending/ascending without propulsion to reach the designated cruising depth, whereas the bow and stern fins act as the actuator to maintain the cruising depth for more energy saving. A hierarchical architecture-based VBS controller, which comprises a ballast water mass planner and an on-off mass flowrate controller, is developed to assure good hovering performance of the on-off type VBS. Both numerical studies and basin tests are conducted on a middle-sized AUV to verify the feasibility and validity of this depth control strategy.

Depth Control of an Underwater Sensor Platform: Comparison between Variable Buoyancy and Propeller Actuated Devices

“…While the study indicates some advantages of hybrid strategies, uncertainties remain regarding the generalizability of results to different depth steps and the absence of experiments including VBM deactivation or buoyancy disturbances. Bi et al [18] proposed a hybrid depth control strategy integrating an on-off hydraulic VBM for swift depth adjustments and fin control for energy conservation during cruising with propellers. The strategy enables efficient diving and surfacing without propeller usage and effective hovering control with low power consumption.…”

Dynamic Neural Network-Based Adaptive Tracking Control for an Autonomous Underwater Vehicle Subject to Modeling and Parametric Uncertainties

“…Motivated by the great challenges associated with the problem of AUV control subject to uncertainties, the research community has increased its efforts to find new strategies to achieve solutions for different control objectives related to underwater robots such depth control, station-keeping, trajectory tracking, path-following, fault tolerant control, or docking operations [15][16][17][18]. Research studies have demonstrated that intelligent control techniques ( [19,20]) are highly effective to deal with this type of problem because of their adaptive and robustness nature.…”