Dynamics and adaptive fuzzy turning control of an underwater glider

Underwater gliders are high efficiency underwater vehicles without propeller systems. The glider is capable of sawtooth motion in the vertical plane and spiral motion along a circular helix which is aligned with gravity. Both of the two types of motion are stable and have been observed on most commercially gliders. An underwater glider is able to turn head if the two types of motion are cooperated, which is significantly important in path planning. However, the switch stage between the two motions is unstable since the glider dynamic model is highly nonlinear, highly coupled, and under-actuated. This paper presents a thorough analysis of characterizing the turning of underwater gliders. The nonlinear multi-body dynamic model of an underwater glider actuated by a single internal movable and rotatable mass is established. An adaptive fuzzy control algorism based on closed-loop proportion control method is applied to the control of course angle. Finally, the simulation results of the adaptive fuzzy control algorism are proved with good performance by comparing with conventional feedback control method.