Research On Calibrate And Compensate Technology Of Strapdown Inertial Navigation System

Strapdown inertial navigation system has become one of the most widely used inertial navigation means.The inertial sensors which loaded on inertial navigation system are used to measure the acceleration and angular velocity of the carrier relative to the inertial space,and the navigation information of the carrier such as speed,attitude and position are calculated through the navigation computer.Inertial navigation has been widely used in military field because of its unique concealment and autonomy compared with other navigation modes.As a precision instrument,navigation accuracy of strapdown inertial navigation system is affected by various types of errors,the characteristics of these errors are also different from platform inertial navigation.Various types of errors which affecting navigation accuracy are analyzed and studied in this paper,The main errors are summarized as inertial sensor errors,IMU(inertial measurement unit)misalignment angle errors and initial condition errors.Aiming at these three kinds of errors,the corresponding system-level calibration compensation methods are proposed.The main work is as follows:1.The sensors studied in this paper are FOG(fiber optic gyroscope)and quartz flexible accelerometer.Fiber optic gyroscope and quartz flexible accelerometer are susceptible to temperature because of their working principle.The method of modelling to compensate the temperature effect is adopted in this paper.For the temperature drift of FOG,the least square method,BP(back propagation)neural network and particle swarm optimization BP neural network model are used to compensate,and the compensation effect of particle swarm optimization BP neural network is the best.The least square method is used to compensate the scale factor of FOG and the temperature drift of quartz flexible accelerometer.2.Under ideal conditions,the sensitive axis of the IMU composed of gyroscope and accelerometer is required to coincide with the carrier coordinate system.In practice,there is a deflection between the actual direction of IMU sensitive axis and carrier coordinate system,which is called misalignment angle.For the processing of misalignment angle error,the sixposition calibration method is adopted.The local earth rotation component and gravity acceleration are taken as standard input,and the direction cosine matrix and other IMU parameters of the misalignment angle are calculated according to the actual output of the inertial measurement module,and the misalignment angle is compensated according to the matrix.The experimental results show that the method can effectively reduce the misalignment error.3.For the initial condition error of strapdown inertial navigation system,transfer alignment with attitude and velocity as matching parameter is adopted.The transfer alignment adopted in this paper is using the aligned high precision main inertial navigation system and the misaligned sub-inertial navigation system to estimate the deviation of attitude and velocity measurements of the carrier.The Kalman filter is used to estimate the relevant error parameters of the sub-inertial navigation system,and these error parameters are used to align the sub-inertial navigation system.The alignment method is simulated in matlab,and the results show that the relevant error parameters can converge quickly.