Research On Scalar Deeply-coupled Global Navigation Satellite System And Inertial Navigation System

GNSS/INS deeply-coupled navigation system integrates the information of GNSS and INS in deep level.It can be divided into two parts:scalar deeply-coupled system and vector deeply-coupled system.Because the robust performance of scalar deeply-coupled system is perfect and the realization is simple.Moreover,it is not necessary to make great changes to each signal processing channel,so it is popular.Therefore,this paper studies the GNSS/INS scalar deeply-coupled navigation system.The research includes error modeling,sensor selection and parameter optimization.The main work in this paper includes:1.The analysis of tracking loop in the GNSS/INS scalar deeply-coupled system lacks the detailed error model theory.Aiming at the problem that the tracking performance of the tracking loop cannot be analyzed quantitatively,several Laplace domain models are carried out including acceleration zero deviation,gyro drift and scale factor error,which are used to evaluate the performance of INS devices commonly.And the auxiliary delay is also taken into account.The performance of INS-assisted PLL is quantitatively analyzed and verified by simulation.Theoretical analysis and simulation results show that the auxiliary delay error is the main factor affecting the transient characteristic of the tracking error,but it will eventually converge to zero.The gyro drift error will accumulate over time,so it will affect the steady state performance of the tracking loop.Moreover,the influence of scale factor error is related to the dynamic of receiver.Through the modeling method,the transient characteristics and steady-state characteristics of the tracking loop are quantitatively analyzed,which can provide a theoretical basis for the sensor selection and parameter optimization.2.The lack of device selection theory and the rule of error calibration on GNSS/INS deeply-coupled navigation system results in a large difference between the choice of equipment and the actual needs.Aiming at this problem,an INS device selection strategy and INS error correction time interval setting method for GNSS/INS deeply-coupled navigation system are proposed based on the modeling and quantitative analysis.The strategy indicates that the low level INS can be used to assist the GNSS tracking loop when the noise bandwidth is greater than 3.08 Hz and the INS error calibration time interval is 1 s.Medium level INS can hold the tracking error of INS aided PLL below threshold in the 581 s calibration interval when the bandwidth is 5Hz.High level INS can achieve longer auxiliary for the GNSS tracking loop without calibration.When the bandwidth is 5Hz,the auxiliary time can be 5 hours.Similarly,when INS is selected,the calibration time parameter can be set based on the theory.This theory can be directly applied to the selection and error calibration of INS devices in engineering,guiding the system to reduce the cost and power consumption.3.Aiming at the problem that the loop parameter cannot obtain the optimal value caused by the imperfect error modeling of the INS auxiliary branch,this paper presents an adaptive optimal bandwidth adjustment algorithm for GNSS/INS scalar deeply-coupled navigation system based on the detailed error modeling and analysis.Theoretical analysis and simulation results show that the adaptive optimal bandwidth can effectively suppress the influence of the error accumulation of INS on the tracking characteristics of the loop and can improve the performance of the tracking loop in the complex environment(mainly the change of the dynamic and the carrier noise ratio of received signal).Specifically,when low level INS is used to aid PLL in 5 s,the algorithm can ensure the tracking error below 1°.Compared with fixed bandwidth method,the error is reduced by about 10 times.When the acceleration varies from-40~120m/s~2 and carrier-to-noise density ratio to varies from 36~50 dB?Hz,this algorithm can diminish the tracking error and make the tracking error below the threshold.Therefore,it can provide theoretical basis for the parameter setting and performance optimization in engineering.To sum up,the tracking loop of GNSS/INS scalar deeply-coupled navigation system is studied in this paper.Several error sources of INS are molded and analyzed.On the basis of this error modeling,an INS device selection strategy and an adaptive optimal bandwidth adjustment algorithm are proposed,which provide theoretical basis for engineering implementation of GNSS/INS deeply-coupled navigation system.