Design, Implementation, and Characterization of a Novel Positive Buoyancy Autonomous Vehicle

The unmanned surface vessel (USV) and the autonomous underwater vehicle (AUV) have become important means of ocean observation. In this paper, we have combined the characteristics of USV and AUV to design a hybrid energy positive buoyancy autonomous vehicle that satisfies requirements for water surface and underwater operations. The vehicle maintains positive buoyancy and underwater motion is achieved through thruster propulsion, inverted V rudder adjustment attitude, and using the lift generated by its wing to counteract the buoyancy force. Therefore, the vehicle does not need to carry a complicated variable buoyancy device, and the space saved can carry more energy or payload. The hybrid energy technology of solar batteries and lithium batteries will also be used to improve the endurance of the positive buoyancy autonomous vehicle. The main contributions of this article are new solutions to the challenges of combined water surface and underwater motions, the optimization design of the vehicle, the development of the required control algorithms, and the demonstration of the vehicle successfully surface sailing, entering, diving, underwater sailing, and exiting the water. The results of the lake test demonstrate that the positive buoyancy autonomous vehicle has desired motion performance, high safety, and strong adaptability to the environment.