Optimal Universal Controllers for Roll Stabilization

TL;DR

This paper introduces a novel universal control approach for ship roll stabilization that effectively handles unknown wave disturbances by approximating them with polyharmonic signals, outperforming classical methods in simulations.

Contribution

It develops a universal controller framework based on polyharmonic disturbance approximation, enabling optimal roll stabilization without precise disturbance spectral knowledge.

Findings

OUC stabilizes roll motion more efficiently than classical methods.

The approach handles uncertain amplitudes and phases of disturbances.

Simulation results demonstrate improved stabilization performance.

Abstract

Roll stabilization is an important problem of ship motion control. This problem becomes especially difficult if the same set of actuators (e.g. a single rudder) has to be used for roll stabilization and heading control of the vessel, so that the roll stabilizing system interferes with the ship autopilot. Finding the "trade-off" between the concurrent goals of accurate vessel steering and roll stabilization usually reduces to an optimization problem, which has to be solved in presence of an unknown wave disturbance. Standard approaches to this problem (loop-shaping, LQG, $H_{\infty}$-control etc.) require to know the spectral density of the disturbance, considered to be a \colored noise". In this paper, we propose a novel approach to optimal roll stabilization, approximating the disturbance by a polyharmonic signal with known frequencies yet uncertain amplitudes and phase shifts. Linear quadratic optimization problems in presence of polyharmonic disturbances can be solved by means of the theory of universal controllers developed by V.A. Yakubovich. An optimal universal controller delivers the optimal solution for any uncertain amplitudes and phases. Using Marine Systems Simulator (MSS) Toolbox that provides a realistic vessel's model, we compare our design method with classical approaches to optimal roll stabilization. Among three controllers providing the same quality of yaw steering, OUC stabilizes the roll motion most efficiently.