Adaptive Control Aspects of a Rudder Roll Stabilization System

Abstract

Abstract This paper gives a survey of the design of an autopilot for rudder roll stabilization for ships which uses the rudder not only for course keeping but also for reduction of the roll. The system has a series of properties which make the controller design far from straightforward: the process has only one input (the rudder angle) and two outputs (the heading and the roll angle); the transfer from rudder to roll is nonminimum-phase; because large and high-frequency rudder motions are necessary, the nonlinearities of the steering machine cannot be disregarded; the disturbances caused by the waves vary considerably in amplitude and frequency spectrum. In order to solve these problems computer simulations, scale-model experiments and full-scale trials at sea have been carried out. Besides, a new approach to the LQG method has been developed. The results obtained so far, indicate that a rudder roll-stabilization system is able to reduce the roll as well as a conventional fin-stabilization system, while it requires less investments. Based on the results obtained in this project the Royal Netherlands Navy has decided to implement rudder roll stabilization on a series of ships under construction at this moment.