Event-triggered disturbance rejection tracking for surface ships under stochastic disturbances and actuator saturation

This paper focuses on the problem of the event-triggered disturbance rejection tracking control for marine surface ships with ocean stochastic disturbances under actuator saturation effects. The ocean stochastic disturbances are described by the first-order Markov stochastic process. The event-triggered disturbance rejection tracking control is built through incorporating a stochastic disturbance observer and an auxiliary dynamic filter with the event-triggered vectorial backstepping framework. A stochastic disturbance observer is established to provide stochastic disturbance estimations on-line. Then, an auxiliary dynamic filter employs the commanded control derivation vector to modify the feedback control errors on-line so as to preserve the disturbance rejection tracking control performance under adverse saturation effects. The event-triggered control protocol involving tracking errors and commanded control derivations is designed to reduce the excessive wear and tear of propellers and thrusters in the presence of ocean stochastic disturbances. Illustrative simulations on a 1:70 model ship demonstrate the effectiveness of the proposed control scheme.