Disturbance observer based control for dynamically positioned ships with ocean environmental disturbances and actuator saturation

Abstract

AbstractThe antidisturbance control scheme for the dynamically positioned ships with ocean environmental disturbances and actuator saturation was presented. The ocean environmental disturbances comprises slowly varying disturbances and additional stochastic disturbances. The stochastic disturbance observer was constructed to online estimate the slowly varying disturbances. Based on estimation, a stochastic antidisturbance controller was proposed by combining the disturbance observer‐based control with the stochastic control, where the actuator saturation was dealt with by the polytopic bounding technique. Furthermore, the optimal control allocation method was introduced to distribute control commands into each actuator. Finally, the ship's position and heading are maintained at the desired values and all signals of the closed‐loop system are asymptotically mean‐square bounded. And comparative simulation under different conditions demonstrates the validity and the superiority of the proposed control scheme.