In-flight Alignment Technique For Guided Projectile Using IMU/fluxgate/satellite Integrated Navigation System

Guided projectile needs to withstand harsh environments such as high overload and high rotating speed when launched.Therefore,the inertial navigation system on the guided projectiles should be re-aligned in the air,in order to provide accurate initial attitude and other information for the navigation system.In this paper,with the current advantages of geomagnetic navigation,the magnetic sensor is introduced into the MEMS inertial navigation / satellite combination system to re-aligned in the air after the launch of the guided projectiles.Based on the study of the MEMS-based initial alignment and satellite navigation principle,the paper also studies the magnetic sensor attitude measurement model.Besides,this paper also simulates the trajectory of the guided projectiles in the air after launched,then analyzes the effect of alignment in the air through the MEMS inertial navigation/magnetic navigation/satellite integrated systems.Unlike common MEMS inertial navigation /satellite combination systems,the guided projectiles combination systems in the air alignment introduce magnetic sensor navigation subsystems.Therefore,this paper starts with the selection of guided munitions magnetic sensors,analyzes the selected fluxgate sensor and field calibration.Then,the error analysis and modeling are carried out for the systematic errors of the guided magnetic sensors and the background magnetic field errors.The influence of system error on the magnetic data are analyzed by simulation.Finally,the manufacturing error in the system error of the magnetic sensor and background magnetic field error are simulated by ellipsoid fitting.This paper researches the air alignment stage of the guided projectile,the magnetic sensor offers the additional roll angle and pitch angle,which could be introduced into MEMS inertial navigation/satellite combination system via Kalman filter.The paper researches the measurement principle of magnetic sensor,and designs magnetic sensor attitude measurement algorithm based on successive approximation method.Based on the trajectory simulation,the paper also analyzed the influence of three error sources on attitude estimation accuracy.Finally,the static experiments and dynamic tests of unilateral rotation and circumferential rotation based on single-axis turntable are designed which are used to test the magnetic sensor attitude measurement algorithm.On the basis of the attitude measurement algorithm of magnetic sensor,and in order to verify that MEMS inertial navigation/magnetic navigation/satellite combination system could well correct the pose information of MEMS inertial navigation.This paper simulates the guided projectiles’ alignment in the air and establishes a 15-dimensional mathematical model,then by using the standard Kalman filter,the MEMS inertial navigation/satellite combination system and MEMS inertial navigation/magnetic navigation/satellite combination system are simulated respectively.The results show that the extra roll angle and pitch angle provided by the magnetic sensor make a significant improvement in the accuracy of attitude angle estimation.