A unified switching dynamic modeling of multi-mode underwater vehicle

Hybrid underwater vehicles have increasingly been deployed in ocean observation and monitoring. This study presents a novel multi-mode underwater vehicle (MUV) motivated by integrating maneuvering efficiency, endurance, and vertical continuous observation capacity. It can switch freely among three operation modes, including vertical diving and floating mode (VDF mode) like the Argo profiling float (APF), steady gliding mode (SG mode) similar to the underwater glider (UG), and propeller-rudder propulsion mode (PRP mode) such as the autonomous underwater vehicle (AUV). The generalized theory of mode switching through extreme pitch angle adjustment is emphasized, mainly to achieve smooth switching between VDF mode and SG mode (or PRP mode) with the critical design principles of the attitude and buoyancy subsystems. Mathematical models describing the motion of three operation modes are developed, particularly considering the actuators' dynamic characteristics. Simulations are performed to verify the mobility performance of the vehicle, especially considering the influence of actuator dynamics on mode switching. Real-time prototype experiments demonstrate the desired performance of various modes and, in particular, confirm the necessity of the mentioned design criteria for mode switching.