Workspace optimization of azimuth thrusters applied by dynamic positioning

• Main Authors: SHANG Liubin, WANG Wei, LIU Zhihua
• Format: Article
• Language: English
• Published: Editorial Office of Chinese Journal of Ship Research 2020-04-01
• Series: Zhongguo Jianchuan Yanjiu
• Subjects: dynamic positioning; azimuth thruster; thrust distribution; optimal workspace; singularity
• Online Access: http://html.rhhz.net/ZGJCYJ/html/2020-2-104.htm

Objectives In order to make the dynamic positioning of azimuth thrusters respond to external environmental forces in time, avoid the large-scale rotation of the thrusters and achieve high precision dynamic fixed-point positioning control, research on the optimal workspace of azimuth thrusters is carried out. Methods Taking the dynamic positioning self-driven model with two azimuth thrusters and a lateral thruster as the research object, the problem of the current thrust allocation singularity optimization index is analyzed, and the thrust limits of the thrusters are further considered. The method of traversing the thrust and azimuth of the thruster to establish the axial maximum capability matrix is applied. According to the external environmental force mean and variance, the minimum axial capability requirements are calculated, the optimal workspaces of the thrusters in different external environments are determined by combining the prohibition angle, and a new thrust allocation logic framework is proposed. The fixed-point positioning experiment of a dynamic positioning ship model based on the traditional singularity index and optimal workspace is carried out. Results The experimental results show that the proposed method can overcome the shortcomings of the previous singularity index and achieve control accuracy of 0.1 m radius position and 0.5 degree direction control accuracy under the propeller azimuth within the range of fifty degrees.Conclusions This method can replace the singularity index; it also satisfies the requirements of the ship model dynamic positioning experiment and has certain practical engineering value.