Research On The Error Model Of Spaceborne Fiber Optic Gyro Strapdown System

Because the satellite will be smaller, so it is impossible to equip complex navigation system, and spaceborne FOG SINS has become a trend. The precision of this system is mainly effected by two facters: the random drift of FOG increasing with time, and the precision of the satellite attitude determination.Now, the precision of FOG made in our country is low, and to improve it costs high and is difficulty. So this paper improves the system precision by software, and mainly deals with the effect analysis and simulation validation of the software in the error modeling,filtering of the FOG random drift, and the satellite attitude determination.The main methods to minish the FOG random drift are Kalman filter and Wavelet filter. To gain the better filter method, the FOG drift data are processed respectively by Kalman filter and Wavelet filter, and the effect of filtering is analyzed and compared by Allan variance and frequency spectrum method. The simulation results show that Wavelet filter can minish the FOG random drift more simply and more efficiently.Because the Kalman filter is based on the steady time series model of FOG random drift, so the unsteady sample of FOG drift needs statistical test and corresponding pretreatment using stochastic signal processing methods, and then the mathematic model is established by time series analysis theory.To satisfy the require of the sattllite attitude control, and investigate the change of attitude estimate precision after filtering the FOG random drift, this paper aiming at the Earth-oriented three-axis stabilized sattllite, based on quternion, designs in detail an attitude determination system of"FOG+Earth sensor+ Sun sensors"using extended kalman filter. The simulation results show that the system can obtain a high precision of attitude estimate, which is feasible, and that the improve of FOG random drift is useful for the precision of attitude estimate, and then the meaning of the filter of FOG random drift to improve the system precision is affirmed father.