Research On Tightly-Coupled GPS/SINS Navigation System For Highly Precise Doppler Frequency Shift Estimation

Aiming at the form of ultra-tightly coupled GPS/SINS system assisted by SINS, on the purpose of narrowing the bandwidth of GPS tracking loop and developing the ability of dynamic movement and anti-interface,this paper presented a method to estimate Doppler frequency shift precisely based on tightly coupled GPS/SINS integration system.With the improvement of the navigation system' s precision, it could calculate Doppler frequency shift with the highly precise performance of the system and create the ARMA model of stochastic errors in it, completing the precise estimation of Doppler frequency shift.The main contents are listed as follows:(1) The working principle of SINS was analyzed,and its error equations were created.SINS navigation algorithm was validated by simulation, and the initial alignment of SINS was proved based on experiment data. Besides,the principle of GPS positioning and speeding was studied. The GPS positioning and speeding experiments were completed via collecting GPS data. Both experiments validated their correctness.(2) The filtering theory of GPS/SINS integration and its algorithm were introduced and proved. According to the difference of GPS/SINS coupled depths, both the loosely and tightly coupled models were created to realize the algorithm. Besides, the half-physical stable simulated experiments were carried out to ensure them.(3) According to analyzing the reasons of Doppler frequency shift in GPS, the model of Doppler frequency shift in GPS observation was created, which led to the estimation model of tightly coupled system. Based on estimating the Doppler shift with tightly coupled GPS/SINS system, an ARMA model was created for the stochastic error in it, completing the accurate estimation of the Doppler shift.This paper validated the availability and efficiency of tightly coupled GPS/SINS algorithm via collecting data in vehicle experiment outdoor. Compared with GPS standalone,the tightly coupled system got improved at least 46.7% in positioning and 29.4% in speeding.By estimating Doppler frequency shift on this foundation, and creating the ARMA model of the stochastic errors, the frequency precision got improved by around 0.5Hz, which is significant to assisting the GPS loop.