Anti-disturbance leader–follower synchronization control of marine vessels for underway replenishment based on robust exact differentiators

Abstract

This paper considers the leader–follower synchronization control of under-actuated marine vessels for underway replenishment. An integrated guidance and control method is presented to achieve the underway replenishment operations despite of unknown model uncertainties, external disturbances, and unknown velocities of the leader vessel. Specifically, a velocity observer based on a robust exact differentiator (RED) is firstly designed to estimate the unknown velocity of the leader vessel. Next, a finite-time light-of-sight guidance law based on the velocity observer is developed to synchronize the follower vessels with the leader vessel. Then, two disturbance observers based on REDs are designed to estimate the total disturbances composed of model uncertainties and external disturbances at the kinetic level. With the aid of the RED-based disturbance observers, an anti-disturbance nonlinear control law is presented to track the desired guidance signals in finite time. The tracking errors of the closed-loop system are proved to be ultimately uniformly bounded via Lyapunov stability theory. Finally, an example is utilized to illustrate the effectiveness of the proposed anti-disturbance synchronization control method for multiple under-actuated marine vessels.