OUTPUT FEEDBACK ADAPTIVE CONTROL OF DYNAMICALLY POSITIONED SURFACE VESSELS: A DISTURBANCE OBSERVER-BASED CONTROL APPROACH

In this paper, we introduce a novel adaptive output feedback trajectory following control approach for unmanned surface vessels (USVs) exposed to external disturbance due to waves and winds. The proposed controller just requires measuring position and orientation of the ship and does not require the knowledge of ship parameters. A velocity observer is designed to estimate the ship velocity and a disturbance estimator is designed to compensate the effect of disturbance. Furthermore, an adaptive update law is designed to estimate the ship unknown parameters. It is shown that the closed-loop system formed by the adaptive controller, velocity observer, and the disturbance estimator leads to semi-global tracking and velocity/disturbance estimation error. The effectiveness of the proposed controller is examined mathematically and numerically, and the results are compared with those of previous methods.