Objective  In complex marine environments, the vertical movement of ships often has a significant impact on the safety of offshore engineering operations. Active heave compensation devices can counteract the vertical movement of ships, with all compensation commands relying on the vertical vessel attitude motions (roll, pitch, and heave) as inputs. Therefore, a ship attitude prediction method based on low-cost inertial measurement unit is proposed.

Method Based on the mathematical model relating quaternions to ship rotational motion, the linear acceleration of the ship in dynamic states is considered. A virtual yaw measurement value is introduced, and a ship attitude observer is designed. The extended Kalman filter algorithm is used to predict the ship's attitude.

Results Simulation analysis and six-DOF platform experiments show that the prediction errors for the ship's roll and pitch angles are within 5%, comparable to those of commonly used motion reference units. In addition, the method can predict the relative change in the yaw angle with a prediction error of no more than 8%. Experiments conducted under different sea conditions confirmed the accuracy and effectiveness of the ship attitude prediction method.

Conclusion The research results provide high-precision ship attitude data for wave compensation equipment, enhancing the safety and efficiency of marine engineering operations.