Research On Heave Algorithm Of SISN Based On Fiber Optic Gyroscope

In the process of Marine navigation,heave movement in the vertical axial will appear as affected by factors such as wind and waves.So,real-time and effective heave motion measurement can provide reference for the operator in many sea-works,such as the launch of ship-borne weapons and aircraft take-off and landing,the drilling platform heave compensation device and the pipe laying vessel stable structure and so on.With accurate heave information,the driving safety and reliability in marine navigation will be greatly improved.It is of great significance for the development of ocean engineering and the modern navigation technology.Firstly,this paper proposes a heave measurement scheme based on phase compensation method.To solve the phase error caused by traditional IIR high-pass filter used in heave measurement,a phase compensation algorithm based on linear frequency modulation Z transform is proposed,and an adaptive all-pass filter is designed to compensate the phase of the output signal of high-pass filter.This method can output real-time and high-precision heave displacement information,but as the frequency information obtained by spectral analysis has hysteresis characteristics,this method has some limitations.In order to avoid the hysteresis characteristics above,a kind of heave measurement scheme is based on adaptive frequency estimation was proposed,in this scheme,a real-time estimation method of frequency based on weighted linear combination of Fourier was used to estimate the real-time frequency of the heave acceleration signal.In this way,the adaptive phase compensation filter could be design to achieve high precision heave displacement output.Nevertheless,the precision was influenced by frequency estimation.In view of the defects of the algorithms above,this paper finally puts forward the heave measurement scheme based on multiple LPF unit,the scheme has used reverse thinking,considering the signal superposition principle and the characteristics of the low frequency error term slow change,the phase error of low-pass filter on the impact of slow change items was ignored.In addition,the selection of the filter order number,weight number also have been analyzed scrupulously.The scheme has the advantages of simple structure,not influenced by frequency estimation,high efficiency,small computation and high precision heave displacement information.In this paper,a heave table experiment was designed,and two different types of strap-down inertial navigation system(SINS)were selected for testing to provide data support for the algorithm proposed in this paper.The heave table data are used to verify the feasibility of the three algorithms.The experimental results show that the heave displacement accuracy of SINS1 can reach within 0.01 m and that of SINS2 within 0.02 m.Based on the detailed analysis and comparison of the algorithms,this paper proposes to adopt the heave measurement scheme based on multiple LPF units in the actual changeable Marine environment.