Abstract: Aiming at the application demand in precise measurement of heave motion during ship movement, a heave motion measurement scheme based on inertial navigation system is proposed. In view of the poor adaptability of the traditional filtering method and the problem of phase shift and amplitude error, a new design of adaptive digital high-pass filter based on complementary method is proposed according to the prior knowledge and real-time sea condition monitoring results, which monitors the sea condition through a sliding monitoring window and adapts the filter parameters in real time. Twice integrations and three times of adaptive high-pass filtering experiments are carried out on the measured acceleration values, which can filter out the low-frequency system errors and retain the useful high-frequency heave motion. Simulations and experiments under different sea conditions verify the feasibility of the measurement scheme and the new filtering method. The test results show that, compared with the traditional method, the new filtering method can adjust the filter parameters adaptively according to the sea condition, and reduce the phase error and amplitude error of the heave motion, in which the amplitude error is reduced at least 10 times, the amplitude error is reduced at least 2 times, and the measurement precision reaches centimeter level.

Key words: adaptive filter, heave motion, inertial measurement, high-pass filter