Reliability-based robust event-triggered anti-windup control for Arctic dynamic positioning of turret-moored vessels under ice loads

Abstract

This paper proposes a reliability-based robust dynamic positioning control method for a turret-moored vessel subject to unavailable model parameters, unknown disturbances and input saturation in ice regions. Firstly, based on the Discrete Element Method (DEM), an ice load model is established to simulate the ice loads exerted on FPSO vessels in broken ice environments. Then, the Gaussian error function is employed to approximate the input saturation nonlinearity. The unavailable model parameters, unknown disturbances, ice loads and input saturation approximation error are ingeniously transformed into a linear parametric form with only one parameter needed to be adjusted online. Further, we proposed a reliability-based robust anti-windup controller to achieve the arctic dynamic positioning of FPSO vessels, where a parametric adaptive method is designed to adjust the single unknown parameter online. Moreover, an event-triggered mechanism is integrated into the proposed controller to reduce the controller execution frequency and thruster wear, which can extend the service life of thrusters to some degree. Theoretical analysis proves that all signals in the closed-loop arctic dynamic positioning control system are globally uniformly ultimately bounded. Finally, the effectiveness of the proposed methods in arctic region dynamic positioning is validated through simulations.