Energy Saving of Course Keeping for Ships Using CGSA and Nonlinear Decoration

In order to further reduce the rudder angle and the steering frequency on the premise of achieving good course-keeping control effect for ships, a concise robust control algorithm is proposed in this paper. The second order closed-loop gain shaping algorithm is employed to design the linear controller first. Then the final control law is achieved by using the nonlinear decoration technique. The stability of the closed-loop system is proved by the Nyquist criterion. Taking training vessel Yukun as a test plant, the simulation experiments under normal sea state and heavy sea state are carried out respectively to verify the effectiveness of the proposed scheme. The results indicate that compared with the existing methods, the proposed control algorithm not only has obvious advantages in energy-saving effect and smoothness, but also has stronger anti-interference ability under heavy sea state. The second-order closed-loop gain shaping controller decorated by bipolar sigmoid function has better robustness and a concise form. Meanwhile its remarkable energy-saving effect and smoothness make steering condition meet the requirements of navigation practice, which is of great significance for ships to realize safe and efficient navigation.