ABSTRACT

This paper attempts to apply the adaptive control theory to design of control system for the ship's rolling motion by using an activated anti-rolling tank. In this theory model parameters of the system are estimated sequentially on the basis of the least squares method. Numerical simulations based on SOLA-SURF scheme are carried out and It is confirmed that the present system can decrease rolling angle effectively over a wide frequency range and cope with change of characteristics of motion by applying the adaptive control theory to control of an activated anti-rolling tank device.

INTRODUCTION

The purpose of this paper is to propose a design concept of ship stabilizing device using an activated anti-rolling tank. Up to now, many types of stabilizer for ship, for example gyro-stabilizer, weight stabilizer, fin stabilizer, anti-rolling tank and others, were tried out, and In recent years fin stabilizer is generally used to reducing ship rolling motion. However, it could not be expected to reduce rolling motion effectively for a ship sailing at low forward speed or for a ship at anchor. On the other hand, the stabilizing performance of the anti· rolling tank doesn"t depend on the forward speed of the ship, therefore the tank stabilizing device can be fitted to any type of ship operating at any speed. The tank stabilizing devices consist of passive and activated types. The passive type is not so efficient stabilizer over a wide wave frequency range. To get useful reducing effect for ship rolling motion over wide bounds of the speed and wide wave frequency range, the authors attempt to apply the adaptive control theory to system design of ship rolling motion by using an activated anti-rolling tank. In this adaptive control system, model parameters of the plant are estimated sequentially on the basis of the least squares method, so the controller can cope with changes of plant parameters by oceanographic conditions or ship's loading conditions.

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