Finite-time dynamic positioning control design for surface vessels with external disturbances, input saturation and error constraints

This work studies the dynamic positioning (DP) control problem of surface vessels subjected to external disturbances, input saturation and error constraints. By combining the disturbance accurate estimation method and the prescribed performance control strategy, a novel finite-time DP control law is developed to address this challenging problem. In particular, a finite-time disturbance observer (FTDO) with correction compensations by incorporating the fractional power-based control design technique is designed to accurately estimate external disturbances, which guarantees that the estimation error converges to zero within a finite-time. Subsequently, a prescribed performance control strategy is proposed to guarantee that the positioning errors of DP surface vessels with saturation constraints meet the error constraint requirements in finite-time. Significantly, an adaptive update law is designed to approximate complex nonlinear items of the DP system to simplify the complexity of the control law design and the system stability analysis. It has been proven that the proposed DP control law can achieve the finite-time control of the DP system and guarantee the uniformly ultimately boundedness of all signals in the closed-loop DP system. Finally, numerical simulations are presented to demonstrate the effectiveness of the developed DP control law.