Ship Dynamic Positioning Control Based on Sliding Mode Observer

A dynamic positioning control system based on sliding mode observer is designed for ships with three degrees of freedom. Firstly, based on the linear superposition of Low-frequency and Wave-frequency models of ships, a sliding mode observer is proposed to estimate the state of ships. Secondly, the error characteristics of the sliding mode observer are analyzed, the stability of the observer is analyzed and proved by using the passivity theory and Lyapunov stability criterion. Furthermore, the gain matrix of the observer is determined based on the frequency domain analysis method. Finally, taking a supply ship as an example, the PID algorithm is used to control the system, and the dynamic positioning control system based on sliding mode observer is simulated under changing sea conditions. The simulation results verify the validity and reliability of the proposed control scheme.