Research On Flight Alignment Method Of GPS/SINS Intergrated Navigation For Gliding Extended Range Projectile

The precision guided projectile plays a more and more important role in the modern war.At present,gliding extended range technology is widely used to improve the range of guided projectiles,and GPS/SINS integrated navigation technology is used to achieve precise guidance.However,the initial alignment problem of SINS(Strapdown Inertial Navigation System)has always been a key and difficult point that severely limits the accuracy of its crackdown.Due to the high rotation speed of the guided projectile when it is just out of the chamber,the working conditions of the contained inertial device are relatively poor,which leads to the failure of the traditional way of launching after static alignment.Based on the above research background,this project designs an air-alignment scheme of GPS/SINS integrated navigation system for gliding extended range projectile,and the three aspects of misalignment model,observability analysis and nonlinear filter designing are discussed in detail respectively.In the environment where measurement noise statistics are uncertain,non-linear filters that can measure noise are studied to achieve their air alignment.The equation of SINS large misalignment error model is established.The traditional Euler angle error models are mostly deduced based on the hypothesis of small attitude error angles.However,due to the uncertainty of the attitude error angle from the time shell launches from chamber until the INS module starts working,the initial value of the misalignment angle will be very large,which makes it difficult to apply the conventional Euler angle error model.In order to improve the above modeling problem,this paper establishes an additive quaternion error model,which can be applied to the establishment of a system model with any initial attitude error angle.The observability of GPS/SINS integrated navigation system is analyzed.Using GPS(Global Positioning System)to measure speed and position information as measurement information,an observation model of the integrated navigation system is established.Considering that the observable degree is related to the maneuvering method,the maneuvering method of the guided projectile is generally fixed and invariable.Therefore,only the observability of the conventional maneuvering method of guided projectiles is discussed.The PWCS observa bility analysis theory and the observable degree analysis method based on singular value decomposition are used to realize the observability analysis of the GPS/SINS model.Based on the EKF(Extended Kalman Filter)algorithm,the misalignment angle is estimated.Before the INS module is working,coarse alignment is performed to correct the misalignment angle,and the revised result is used as the initial value for the navigation of the SINS system.On this basis,due to the nonlinearity of the quaternion error model,the information measured by GPS is used as the quantity measurement,and the SINS update is implemented by the double sub-sample algorithm,then the misalignment angle is estimated by the EKF algorithm.Several nonlinear filtering algorithms suitable for strong nonlinear systems are studied.EKF has the advantages of simple algorithm and easy implementation,so it is widely used in engineering.However,the guided projectile is in a highly dynamic and high-speed rotating state.The error model of the inertial navigation system is strongly nonlinear.At this time,the accuracy of the EKF algorithm is seriously reduced and even diverged,and the calculation of the Jacobi matrix is more complicated.In view of this situation,several filtering algorit hms suitable for strong nonlinear models are studied,including UKF(Unscented Kalman Filter)based on UT transform and CKF(Cubature Kalman Filter)based on spherical-radial cubature criterion and ACKF(Adaptive Cubature Kalman Filter)based on Sage-Husa maximum posterior estimator.Finally,several filtering methods are applied to the GPS/SINS integrated system alignment model,and numerical simulations are carried out.Through the analysis and comparison of the simulation results,the validity of the algori thm is verified.Therefore,the research in this paper has a certain guiding role in engineering practice.