Design of UDE-based finite-time fault-tolerant control for DP vessels with complex disturbances and input constraints

Abstract

This paper presents a novel uncertainty and disturbance estimator (UDE) – based finite-time fault-tolerant control scheme, applied to the controller design of dynamic positioning (DP) vessels with environmental disturbances, model uncertainty, input saturation, and thruster failures. The proposed method employs a non-singular terminal sliding surface to achieve finite-time stability based on the vessel's position and velocity errors. A UDE is to estimate environmental disturbances and model uncertainties. The auxiliary dynamic system (ADS) and smooth switching function are adopted to compensate for input constraints and avoid singularity caused by ADS. Further, a proposed fault observer is to estimate the thruster's fault state. In partial thruster failure, the utilization of the remaining execution ability of the failed thrusters to achieve vessel control objectives. Theoretical and simulation results show that the proposed method has a fast response, high control accuracy, strong disturbance resistance, and fault tolerance, making it superior to recent and classical trajectory tracking control.