Wave-filtering Observer Design in Station-Keeping Control for Dynamic Positioning Ships

The surface motion of a dynamic positioning ship is typically affected by ocean waves, which can introduce high-frequency (HF) wave motion in their position measurements. The HF wave motions may increase the ship’s energy consumption and accelerate the wear and tear on its actuators. To address this problem, this paper proposes the design of a wave-filtering observer that can effectively filter out the HF wave motion from position measurements, avoiding HF responses in control outputs. In comparison to the Kalman-filtering-based approach, the proposed observer offers several advantages, including independence from the ship’s dynamic model, a simple structure, a robust performance, and a user-friendly implementation. The simulation results have confirmed the effectiveness of the proposed observer in the task of station-keeping control to filter out the HF wave motion.