Initial Alignment Technology Of Strapdown Inertial Navigation System For Vehicle

The strapdown inertial navigation system(SINS)has been widely used in military,civilian and other fields.Initial alignment is a key step before the entire strapdown inertial navigation system works,and its accuracy determines the accuracy of the entire navigation system.The initial alignment of the vehicle-mounted strapdown inertial navigation system is divided into the initial alignment of the static base and the initial alignment of the moving base.Its technical indicators mainly include alignment accuracy and alignment time.This topic is aimed at the inertial device start-up drift that occurs in the actual working environment of the vehicle strapdown inertial navigation system,human noise interference during the initial alignment of the static base,and global positioning system(GPS)speed error during the initial alignment of the moving base,and noise mismatch problems are proposed accordingly.The specific research content is as follows:Firstly,the initial drift of the fiber-optic gyroscope and accelerometer under the initial alignment of the vehicle-mounted strapdown inertial navigation system is addressed,by collecting and analyzing the measured data of fiber optic gyroscope and accelerometer startup at different temperatures,the relationship between fiber optic gyroscope and accelerometer drift and temperature and temperature change rate was studied.By simplifying the current fiber optic gyroscope and accelerometer drift compensation model,The calculation amount is reduced,and the measured data verify that the simplified model can effectively compensate the inertial device start-up drift and shorten the initial alignment time of the system.Secondly,the problem of man-made noise interference during the initial alignment of the stationary base of the in-vehicle strapdown inertial navigation system is addressed,by collecting data output of inertial devices such as people getting on and off the vehicle,parking engine starting,etc.under the strapdown inertial navigation static base of the vehicle,the noise characteristics are analyzed,and an improved empirical mode decomposition noise reduction algorithm based on wavelet threshold strategy is proposed.The measured data verify the effectiveness of the method in reducing noise and improving the stability of the initial alignment algorithm under a static base.Then,the problem of increasing the measurement vector error caused by the GPS speed error during the initial alignment of the moving base is addressed,an inertial system initialalignment algorithm based on a robust feedback strategy is proposed.This method predicts the measurement vector of the current time based on the pose estimated at the previous time,and obtains the variance of the current time based on the measurement vector of the current time.The variance of the time is compared with the variance of the current time,and the current measurement vector is adjusted and fed back based on the strategy of robust control.Simulation and measured data verify that the method can effectively improve the alignment accuracy of the moving base.Finally,the problem of noise mismatch during the initial alignment of the moving base is addressed,by analyzing the attitude error to establish the system state space model,and introducing the idea of unbiased finite impulse response(UFIR)filtering,an initial alignment algorithm for the inertial system based on UFIR is proposed.The kalman filter(KF)also sets the Q and R arrays.It uses the limited measurement data within the observation window length to perform unbiased state estimation,which reduces the system noise and attitude estimation when the noise characteristics are unknown or changed.Impact,simulation and measured data verify the effectiveness of the method.