Error Suppression Method Of Strapdown Inertial Navigation System In Grid Coordinate System

When the inertial navigation system based on conventional mechanics works in the polar region,there will be some problems,such as accuracy degradation,platform tracking North difficulty and so on.Especially near the geographical pole,due to the loss of the definition of northward,it is impossible to provide northward datum.In view of the above problems,some scholars have studied the inertial navigation system based on grid coordinate system.In order to further improve the navigation performance of grid inertial navigation system in polar region,the error characteristics of the system are analyzed in detail,and on this basis,the damping technology and comprehensive correction technology are deeply studied.The specific work of this paper is as follows:Based on the reference frame of grid coordinate system,the mechanical arrangement of grid inertial navigation system is designed.The spatial analytic geometry is used to derive the conversion relation between the velocity,position and attitude matrix of the system in the traditional northern position inertial navigation system and the grid inertial navigation system,and the free switch between the mechanical arrangement of different strapdown inertial navigation system is realized.Based on the error analysis of the grid inertial navigation system,it is determined that there are three kinds of periodic oscillations in the grid inertial navigation system,that is,schuler periodic oscillation,Foucault periodic oscillation and Earth periodic oscillation,and the error characteristics of longitude error and azimuth misalignment Angle divergence with time are found.Simulation results verify the feasibility of grid INERTIAL navigation system in polar region.For the periodic oscillation in the grid inertial navigation system,the external speed auxiliary grid inertial navigation system is obtained by using log.An adaptive feedback gain damping method is proposed to solve the complex design problem of the traditional external horizontal damping method and the damping coefficient is difficult to change.In this method,the critical stability of the closed-loop system is changed to asymptotic stability by adding adaptive feedback gain.The feedback gain can be obtained directly from the filter gain matrix in the adaptive filtering without repeated trial-and-error,which ensures that the damping ratio added to the system is optimal to some extent.This method makes the damping ratio of the system larger at the initial stage of navigation and speeds up the convergence rate of the oscillation error.Then the damping ratio decreases gradually.When the system reaches steady state,a smaller damping ratio can reduce the influence of carrier maneuver on the system output.Simulation results show that this method has good damping effect.Although the periodic oscillation error in grid inertial navigation system can be damped by using damping technology,the divergence of longitude and heading angle error can not be restrained.In order to solve the problem of longitude and heading angle error divergence of grid inertial navigation system,the comprehensive correction technology is adopted.The traditional integrated calibration method based on oepq coordinate system,when applied to SINS,requires the carrier to maintain the approximate equal latitude navigation,but this requirement can not be met in the actual navigation of the ship.In order to solve this problem,this paper studies the two-point correction,three-point correction and filtering comprehensive correction method of grid inertial navigation system in inertial coordinate system.According to the type of navigation parameters provided by external auxiliary equipment,that is,the position and heading information of discrete points or a period of continuous time,different comprehensive correction methods are selected.The simulation results show that the three integrated correction methods can restrain the divergence velocity of longitude and heading angle errors,and the two-point calibration and filtering integrated calibration of grid inertial navigation system based on inertial system can also compensate the constant error components of velocity error and latitude error.