Research on 3-DOF stabilized control system of ship propulsion-assisting sail

Abstract

In recent years, wind-assisted ship propulsion (WASP) has become an important technology that can reduce the energy consumption of shipping. With different wind directions, a propulsion-assisting sail is rotated in azimuth to achieve maximum thrust along the ship's course. Most existing servo systems enable azimuth control of sails. However, the ship's attitude motion will affect the energy reduction of the sail. In this paper, this negative influence is described and demonstrated. The idea of three-degree-of-freedom (3-DOF) sail control is presented, and the energy reduction improved by the method is verified. Then, a 3-DOF stabilized control system of the ship propulsion-assisting sail is proposed to achieve azimuth tracking of the sail and compensate for attitude deviation caused by the ship. Considering the attitude target and the asymmetric structure of the sail, a kinematics solution and a dynamic model are established. Regarding the coupling characteristics of multivariable systems, inverse dynamics with a kernel-based multilayer extreme learning machine (ML-KELM) are designed to decouple the origin system. Finally, a numerical simulation was performed, and a principle prototype was developed. Results show that the designed control strategy eliminates the coupling of the original system, and the proposed system ensures the attitude stability of the sail.