Research On Heave Measurement System Based On Inertial Navigation

Due to the stimulation of waves,ships will passively heave in the process of navigation.The accurate measurement of heave information is of great significance in many aspects,such as the cargo transfer between ships,the design of heave compensation device for marine operation equipment,the take-off and landing of carrier-based aircraft and the launching of Shipborne weapons.In this paper,for the purpose of reducing the impact of the sea environment and improving the efficiency and safety of marine operation,the measurement of heave information is studied.This paper designs a method of ship heave measurement based on strapdown inertial navigation.Based on the simulation of the ship's heave trajectory,the heave information is calculated by strapdown inertial navigation,and the heave filter is designed to solve the problem of the divergence of the heave information.The heave filter causes the phase error while solving the divergence of the heave information.The phase error can be compensated by the modified model of band limited Fourier linear combination algorithm,and the high-precision heave measurement is realized.Finally,the error of lever arm effects is analyzed and compensated.The main contents are as follows:Firstly,the digital iterative algorithm of SINS is deduced,and the attitude,velocity and position error models of SINS are established.Based on the characteristics of heave motion,the principle of heave measurement based on inertia is analyzed.This paper uses the strapdown inertial navigation inversion algorithm to generate the heave motion trajectory,and then calculates the heave information based on the heave motion trajectory,analyzes the reason of the divergence of the heave information,and introduces the lever arm effects errors in the heave measurement of the ship.According to the influence factors of the heave measurement and the error model of the acceleration in the sky,a heave filter which can suppress the divergence and filter out the low frequency information is designed.The parameters that affect the performance of the heave filter and the errors caused by the heave filter while restraining the divergence are analyzed.In order to compensate the phase lead error,the basic principle of Fourier linear combination algorithm is introduced.According to the characteristics of the heave signal,the improved algorithm—band limited Fourier linear combination algorithm is used to fit the output signal of the heave filter.A modified model based on band limited Fourier linear combination is used to compensate the phase error introduced by the heave filter.This paper analyzes and compensates the lever arm effects error caused by the mismatch between the installation position of strapdown inertial navigation system and the center of gravity of the ship.The mathematical model of the lever arm error is established and analyzed.The compensation algorithm of the lever arm error is designed to get the heave information of the center of gravity position of the ship and the heave information of any monitoring point.