Research On Initial Alignment Of Fiber-Optic Gyroscope Inertial Navigation System

With respect to the theoretical and technical issues existing in the initial alignment of strapdown inertial navigation system (SINS) with fiber-optic gyroscope (FOG) as inertial sensor, FOG error analysis and research on the initial alignment technology of FOG SINS are conducted. A set of approaches and methods are presented for solving certain theoretical and technical issues in applying FOG in SINS and for realizing the initial alignment of FOG SINS. The main research contents are given as follows:(1) The modeling and filtering method of high precise FOG stochastic error are researched. Based on FOG noise analysis, Allan variance analytical method and time sequence method are studied. The stochastic error model of high precise FOG is built by the consistency of these two analytical methods aforementioned; an improved two-order self-regress AR(2) model is put forward and on-line modeling of high precise FOG stochastic error is realized in the process of initial alignment and static navigation in the inertial system. Real-time filtering of high precise FOG stochastic error is realized by the Kalman filter algorithm.(2) The causes for the FOG angle random walk (ARW) are analyzed; the research methods are presented aiming to solve the problem of FOG's ARW having effect on initial alignment in the inertial system; the influence of FOG's ARW on static alignment and navigation in FOG inertial system is analyzed quantitatively; multiple influences of ARW on FOG inertial system are analyzed and its features are given, which offers the academic guidance for optimizing design of FOG inertial system.(3) The magnetic characteristics of FOG are studied and the methods that improve the FOG's resistance to magnetic field are presented. On the basis of characteristics of the vehicle strapdown gyroscope north-seeking system, the de-biasing FOG which is cost-effective and high-precision has been used in realizing "two position and one surface" north-seeking rotatable mechanism which can be stabilized in a short time. Its anti-magnetic technology is also studied. FOG north-seeking and its FOG's error model are built. Causes of the FOG north-seeking producing multi-position north-seeking error are analyzed and the measures which eliminate or reduce these errors are ascertained.(4) The interference characteristics of army combat vehicle swing are analyzed and a compensating method of swing error is put forward in the coarse alignment of FOG SINS. By means of theoretical analysis and simulation, FOG error models of initial alignment and integrated emendation are established respectively in the FOG SINS. By the "loose coupling" between the fiber-optic inertial measuring unit and speedometer, the integrated calibration method is designed in the FOG SINS.(5) The fitness function is designed regarding the initial alignment of SINS. The genetic algorithm is applied in the coarse alignment and precise alignment, and its feasibility is discussed. Based on the analysis of the characteristics of single genetic arithmetic, genetic simulated annealing algorithm is applied in the initial alignment and results are validated by simulation.(6) Based on theoretical and technical research results mentioned above, from applying theoretical research in practical engineering and scientific research projects, FOG error model, initial alignment algorithm, filtering algorithm, navigation and integrated calibration algorithm are validated in systems. "FOG strapdown attitude and heading reference system" has been developed and passed technical evaluation.