Course keeping control strategy for large oil tankers based on nonlinear feedback of swish function

In order to solve the problem of the course instability and massive energy consumption of large oil tankers in navigation, a simple control strategy is proposed. Regard the large oil tanker as an unstable plant with zero points and poles in the right half plane, map its Nomoto model into the corresponding minimum phase system,then the final control law can be derived based on the closed-loop gain shaping algorithm. In this paper, to realize the purpose of energy saving, a nonlinear feedback link of swish function is applied in the system. According to the theoretical analysis above, take the large oil tanker KARASEA as a test plant, the simulation experiments are carried out in both the general sea conditions and severe sea conditions to verify if the controller is effective. Furthermore, for further test of the robustness of the controller, the Norrbin model of ship motion is also used to carry out the simulation experiments. According to the simulation results, it can be known that the control effect is satisfactory and has great ability in anti-interference. After adding the nonlinear feedback link, the average rudder angle decreases by 15%-20%,the change range of rudder angle decreases by 19%-30%, which means the decrease of the wear and energy consumption of steering engine, so the control strategy proposed in this paper has certain engineering practical significance.