Event-triggered Synchronization Anti-disturbance Control for Ship Replenishment

Objectives This paper investigates the synchronization navigation problem between supply and supplied ships in constantly time-varying ocean environment. The ocean environmental disturbances induced by wind, waves and currents, the interaction effect between ships and interaction of soft connections between ships are considered. An event-triggered synchronization anti-disturbance control based on disturbance estimation and compensation is proposed. Methods The disturbances acting on supply ships are modelled by the first-order Markov process which describes the ocean environmental disturbances induced by waves, wind and currents as well as the unmodeled dynamics. The interaction effect and interaction of soft connections between ships are lumped as unmodeled dynamics. The disturbances observer on-line estimates time-varying unknown bounded disturbances and the disturbances are compensated in the control design by using disturbance estimates. The auxiliary dynamic system helps to reduce control saturation effects on anti-disturbance control. The event-triggered mechanism reduces execution frequencies of commanded control signals to avoid the excessive wear of thrusters. Results The event-triggered control method indicates that the existence of a minimum sampling interval greater than 0 and the inability to trigger infinitely in a finite time. The controller can achieve synchronous navigation between supply and supplied ships, while ensuring the global uniform ultimate boundedness of all the closed-loop control signals. Conclusions Simulation results on a supply ship validate the event-triggered disturbance estimation and compensation control.