Error Mitigation Technology For Strapdown Inertial Navigation System

Development of fiber optic gyro inertial navigation system(FINS)depends not only on high-precision inertial measurement unit(IMU),also depends on an effective system error suppression technique.Rotating modulation technique is one of the most effective methods for inhibiting FINS errors.It can modulate the system errors which diverged over time in the form of periodic oscillations.This paper aims at the biaxial and triaxial rotating modulation techniques of the IMU composed by fiber optic gyroscopes(FOGs)which developed in the laboratory.The main works are as follows:Firstly,the propagation characteristics of the device error in FINS were analyzed.In the IMU coordinate,the mathematical models of FOGs' and accelerometers' input and output signals were established.Combined these models with FINS' error propagation equations,this paper quantitatively analyzed the impact of inertial devices' constant error,scale factor error and installation error on the positioning error in FINS as the ship keeps stationary.As there is no rotation mechanism in FINS,the system errors would continue to accumulate over time.Therefore,the rotating modulation technique is the key to improve the accuracy of FINS.Second,exploring the biaxial rotation scheme and discussing the impact of vector's attitude motion on the system.This research started from the attitude error and velocity error propagation equation of rotation modulation FINS.Then summing up the system's "residual error" distribution and counteract law to get the design principles for biaxial rotation scheme.On the basis of this principle,a novel biaxial rotation scheme was put forward.By compared the device errors' modulating effect from the proposed scheme with original biaxial rotation scheme,the correctness of the theory analyzed previous can be proved.In addition,the impact of attitude motion for SINS was discussed in this paper.The relationship between the coordinates consisted by rotation axis and virtual rotation axis is the key point to isolation attitude movement for SINS on time.Third,a three-axis continuous rotation modulation scheme and the key technologies in this system were researched.Combining the characteristics of FOG and electrostatic gyro inertial navigation system which currently applied in strategic nuclear submarines,to develop high-precision FINS and replace the electrostatic gyro inertial navigation system.The modulation effects of three-axis continuous rotation scheme can be indicated by frequency domain characteristics of the devices errors.In three-axis continuous rotation modulation system,attitude motion should be isolated as previous.The azimuth rotating axis is stabilized in a geographic coordinate orientation axis,and the rate of latitude and longitude is used to construct the filtering function,thereby improving the accuracy of the system.The last chapter of this paper mainly introduced the simulation and experimental results of rotation modulation FINS.The results include: simulation results of the novel scheme and original scheme without attitude motion,simulation results of two schemes in a variety of carrier attitude motion,theoretical simulation results for three-axis continuous rotation scheme under laboratory conditions,and groups of experimental results of these two biaxial rotation schemes.According to the simulation and experimental results,the theoretical analysis can be further verified,which could be prepared for the development of prototype systems.