Optimal Control Design for Automatic Ship Berthing by Using Bow and Stern Thrusters

J. Ocean Eng. Technol. 2010;24(2):10-17.

Bui Van Phuoc,Jeong Jeong-Soon,Kim Young-Bok,Kim Dong-Wook

Department of Mechanical and Control Engineering Graduate School of Pukyong National University,Department of Mechanical and Control Engineering Graduate School of Pukyong National University,Department of Mechanical System Engineering Pukyong National

Keywords: Berthing, Ship motion model, System identification, Optimal control, Tunnel thruster, 2DOF servosystem

Abstract

Conventionally, because it is difficult to control a ship in shallow water and because attempting to do so creates unwanted environmental effects, maneuvering ships in the harbor area for berthing is usually done with the assistance of tugboats. In this paper, we propose a new method for berthing ships automatically by using bow and stern thrusters. Specifically, a steering motion model of a ship is considered, and parameters in the equation are evaluated by the system identification technique. An optimal controller based on observations was designed from the linearization of the non-linear ship motion in the horizontal plane. It is used to reduce the uncertainty about the ship's dynamics and reduce measurement requirements. The performance of the controller was also analyzed for its robustness relative to avoiding disturbing the environment due to winds, currents, and wave-drift forces. Experiments were conducted to estimate the potential for identifying result and the design of the controller. Specifically, in this paper, the system modeling and tracking control approach are discussed based on a two-degree-of-freedom (2DOF) servo-system design.