Research On Self Alignment Technology Of Strapdown Inertial Navigation System

Because of its advantages of good concealment and strong autonomy,inertial navigation technology has been continuously applied in various weapons and equipment of sea,land and air.Strapdown inertial navigation system(SINS)is a hot research direction of inertial navigation because of its advantages of low cost and small size.Before the navigation solution,it is necessary to obtain the velocity,position and attitude information of the carrier at the initial moment.Initial alignment technology emerges as the times require.Although all kinds of navigation methods and integrated navigation have been developed rapidly,but in the case that the reference information can not be provided by other navigation methods,the self alignment technology of strapdown inertial navigation system has important engineering significance because of its strong autonomy and good concealment.1.In this paper,the basic equation of SINS is established based on its working principle,then deduce the error model which corresponded.2.In this paper,the strapdown loop is aligned with the principle of the platform,and the principle of the gyrocompass is aligned with the platform.Before fine alignment,coarse alignment is usually needed to obtain the coarse attitude matrix.In this paper,three coarse alignment methods are analyzed and verified by simulation.Then,the simulation verification of the precise alignment of the compass under the static base is carried out.In engineering application,the azimuth accuracy of coarse alignment is often reduced due to the interference of various environmental factors.For the compass alignment with large azimuth misalignment angle,the time-varying compass parameter method is adopted,and the precise alignment of compass is completed through the gradual change of damping oscillation period.The simulation results of the two methods under different misalignment angles verify the effectiveness of the time-varying compass parameter method.3.Based on the optimum estimation of the initial Alignment of Kalman Filter,this paper developed from the basic principle of Kalman filter,combined with the error model of SINS,the Kalman filter model suitable for sins is derived.According to the corresponding state variables and observation measurements,the state equation and measurement equation are constructed,and the Kalman filter simulation under static base is completed.When the misalignment angle is not small,the Kalman filter is not applicable due to the nonlinearity of the model.In this paper,the unscented Kalman filter is used for the initial alignment of sins with large misalignment angle.The effectiveness of UKF is verified by simulation.4.After discussing the two self alignment methods,this paper adds the reverse navigation algorithm to the two methods.The core idea of the reverse navigation algorithm is to "virtual extend" the sampled IMU data,which can increase the accuracy,meanwhile speed up the reaction rate.In this paper,the backward navigation algorithm is derived from the basic equation of forward navigation.It is applied to the precise alignment of Strapdown compass and Kalman filter respectively,and the algorithm is verified by simulation.The results show that the reverse navigation algorithm can significantly improve the reaction rate in static base alignment,and the number of reverse iterations is analyzed and studied.