Adaptive synchronization for surface vessels with disturbances and saturated thruster dynamics

This work investigates the adaptive synchronization for the surface vessels with disturbances and saturated thruster dynamics. The vessel movement model becomes the three-order equation with mismatched disturbances due to the inclusion of saturated thruster dynamics. The marine disturbances are described as the multiple harmonic disturbances with unknown frequencies, unknown amplitudes and unknown phases. By fusions of the nonlinear observer and the adaptive technique, the marine disturbance estimation and rejection are transformed into the adaptive problem. The auxiliary dynamic filter generates the state vectors to represent the filtered versions of the non-achievable portions of the vessel's positions and velocities. The state vectors on-line correct the control errors for avoiding disturbance rejection performance compromise under thruster saturation. The synchronization controller is derived via the adaptive command filtered backstepping. The surface vessel closed-loop control system is guaranteed stable. The adaptive synchronization scheme is validated by simulations with comparisons in different cases.