Observer-based asynchronous self-triggered control for a dynamic positioning ship with the hysteresis input

This paper focuses on the asynchronous self-triggered control scheme for a dynamic positioning ship considering the hysteresis input. A novel self-triggered mechanism is designed to relax the limitation of the continuous monitoring required for the triggered condition, and the next triggered instant depends on the information at the current instant. In particular, multiple controller-thruster channels are asynchronously self-triggered; i.e., the self-triggered mechanism for each thruster is independent and noninteracting. A neural network observer is constructed to estimate the unavailable velocities for the control design. Meanwhile, unknown backlash-like hysteresis inputs are considered in this scheme through the fusion of the adaptive backstepping recursive design technique. Furthermore, the explosion of complexity existing in conventional backstepping design is avoided on the basis of the dynamic surface technique. Through the Lyapunov theory, considerable effort is made to guarantee semi-global uniform ultimate bounded stability. Finally, numerical simulations are provided to validate the feasibility of the proposed scheme.