Research On Inertial Aided Acquisition Technique

GNSS acquisition loop aided by the Inertial information can effectively improve the performance of GNSS receivers, i.e. it is able to overcome the effects of environmental factors on GNSS and ensure acquisition performance of GNSS acquisition loop in the high dynamic and strong interference environment. The inertial aided acquisition loop is one of the most important part of ultra-tight GNSS/SINS integrated navigation system. It can help the integrated system achieve stability, real-time, continuous, high-precision navigation.In this paper, there are theoretical study and experimental verifications on inertial aided GNSS acquisition. Position, velocity, attitude and other navigation information of carrier are calculated by means of the strapdown inertial navigation algorithm which need the information transmitted from strapdown inertial sensor. The Doppler frequency shift of the GNSS signal is estimated by the inertial navigation results and satellite ephemeris. The Doppler shift estimation errors are analyzd by HMDAR model estimation based on time series. In-depth analysis and simulation of the basic performance parameters of the GNSS receivers’ acquisition technique is done. Based on the above,Inertial aided acquisition method is designed and the performance of aided loop are simulated. Actual experiment data are bring in to validate the acquisition performance.The basic principle of GNSS and SINS system are described separately and RF signal of GNSS satellite are analyzed. Meanwhile, the basic theory on signal acquisition and tracking is researched and simulated. Mathematical derivation and simulation of Strapdown inertial solution algorithm based on quaternion count are conducted. Then the basic framework of ultra-tight integrated navigation is analyzed. Based on the above , the data processing system verification platform based on DSP and FPGA is designed according to the actual application requirements finally.The causes of the Doppler frequency shift of the GNSS are analyzed and the range of Doppler frequency shift is estimated in theory. The influence of Doppler shift on acquisition and tracking of GNSS signal is studied. The Doppler shift error model is established and corresponding Nonlinear time series modeling method HMDAR modeling method are used to estimate Doppler shift error model and to compensate the error.Traditional acquisition algorithm, coherent integration acquisition algorithm, is analyzed and simulated and the parameters that affect the acquisition performance are analyzed one by one. According to the analysis results, the method of GNSS signal acquisition aided by inertial information including inertial navigation speed, position, posture, are intuoduced. The performance of acquisition where the cold start and hot start are bring in are analyzed in the auxiliary receiverExperimental platform is designed with Data processing platform designed by ourselves ,laboratory existing experimental platform, and commercial receiver which is used as contrast.;GNSS intermediate frequency data and the SINS of the original information are acquired in the actual movement environment. The experiment results show signal capture performance is significantly improved, to be able to capture time reduced by more than 30% with the introduction of inertial information to estimate doppler frequency shift.In this paper, the SINS estimates GNSS signal Doppler information to assist signal capture process. The theoretical simulation and actual experiment verified that the introduction of auxiliary information improve the performance of the signal acquisition. That provides basis of theory and practice to introducing inertia auxiliary information to an actual receiver in the future.