Design Practice of Ship Fin Stabilizers and Applying Techniques of Ship Motion Control

Abstract

Nowadays more and more ship motion control systems are applied in various ships. Among ship motions, roll motion causes serious damages to the equipments of ship and its performance, many efforts have been made to invent or create some equipment to weaken these bad effects. However, few types of equipment have had the same impact on roll stabilization as the active fin stabilizers. In recent years much research has been conducted to improve the fin stabilization systems. Some results on fin stabilizers have been obtained by analyzing the classical roll motion model. In particular, based on this classic motion model, recently we have investigated issues of dynamics lift of ship fin stabilizers by using towing tank test results of fin model. As ship roll parameters have heavy uncertainties, we must deal with them in fin stabilizer designs. In fact the biggest difficulty in the design is how to deal with the uncertainties. Some control theories, such as adaptive control and robust control, are used to solve the problem and achieved success in some control systems. But they can not deal with uncertainties of ship stabilizer control well. The difficulty of uncertainties existed in fin stabilizer design also happed in other ship motion control system designs. Some new opinions about design methods of fin stabilizer and ship motion control are proposed. To improve the performance of the fin stabilizers, lift feedback fin stabilizers are then designed.