Nonlinear Adaptive Observer Design for Tracking Control of AUVs in Wave Disturbance Condition

An adaptive observer for tracking control of autonomous underwater vehicles (AUVs) operating in shallow water area is designed. In shallow water environment, significant disturbance due to wave motion is present which affects the position of a marine vehicle. Since it is not energy efficient to counteract the oscillatory disturbance due to waves, it is critical to estimate such wave disturbances and to remove it from the feedback loop so that wear and tear on thrusters are minimized. In this paper, an adaptive observer is designed to estimate shallow water wave motion and low frequency motion by using position and heading measurement concerning unknown wave frequency and damping ratio. The global asymptotical stability (GAS) of the observer is proved by Lyapunov stability theory. A set of simulation results is presented to show the performance of the proposed observer for high speed maneuvering control of AUVs.