Research On Calculation Method Of Ship Heave Motion Based On Inertial Measurement And Digital Filtering

The ship will generate the heave motion along the vertical axis,which is produced by the ocean environment factors such as sea waves.The heave motion has a great influence on taking off and landing of carrier-borne aircraft,launching of carrier-borne weapons,deep-sea mining operations and so on.It is very necessary to measure the heave motion of ship accurately.Firstly,the mathematical models of wave motion and heave motion are established in this paper.Secondly,the vertical velocity and displacement of inertial navigation system are set to zero in navigation solution.Aiming at the different frequency distribution characteristics of heave information with active motion and system errors in vertical acceleration of semi-fixed coordinate system,the heave motion measurement is realized by twice integrations and three times of high-pass filtering.Subsequently,in order to overcome the shortcomings of phase error and amplitude error in traditional filtering methods,a new design of digital high-pass filter based on complementary method is proposed.In order to meet the requirement of heave measurement under changing sea conditions,sliding windows are introduced to monitor and analyze the sea conditions in real time,and an adaptive high-pass filter that can follow the changes of sea conditions is realized,too.Finally,computer simulations and physical platform experiments are carried out respectively.The simulation results show that the new filtering method reduces the error of heave measurement by about 10 times compared with the traditional method and about 0.5 times compared with the fixed parameter method.Physical experiments show that the new filtering method reduces the error of heave measurement by about 2 times compared with the traditional method and improves the accuracy by 0.5 times compared with the fixed parameter method.The proposed scheme of heave motion measurement and adaptive filtering method can achieve high-precision heave measurement without time delay.The filter can adjust the filtering parameters in real time according to different sea conditions,which has good adaptive ability and can meet the requirements of ship's heave motion measurement under complex sea conditions.