Study On Modeling And Signal Processing Technology Of High Precision Fiber Optic Gyroscope

Over the past 30 years, as a new type of inertial-sensitive sensor, fiber-optic gyro (FOG)is widely used in the field of national defense. Abroad, with the arts of optical components and key technology of FOG were broken through, high-precision FOG has entered a stage of use. In China, as a result of the processing technology of optical components and some of the key technology is not yet broken through, high-precision FOG remains in the laboratory stage. Especially modeling techniques and signal processing technology of high-precision FOG, are still in the initial stages of exploration. In this article, based on the work of our predecessors, double closed-loop modem technology based on four-state is brought forward, the optical models and mathematical modeling on the closed-loop control circuit are in-depth research, and the signal processing technology of fiber-optic gyro is deeply studied.First of all, optical structure of three-axis integration fiber optic gyroscope is designed, and mathematical models of optical components in the optical circuit are modeled based on the Jones matrix, according to the theory of optical interference and polarization, the whole mathematical optical Model of FOG is established. On the basis of optical model, the effect of the integrated optical modulator extinction ratio,split ratio and the length of pigtail on the interferometer.Secondly, the modulation demodulation principle of digital closed-loop with the square-wave bias and the causation of gain error of feedback loop are detailed analysis, the advantage and disadvantage of digital double closed-loop modulation demodulation method are studied deeply. On this basis, the scheme of digital double closed-loop modulation demodulation with four-state-bias was brought forward, and the process of modulation demodulation under some different conditions were studied, and gave the modulate-demodulate equations. Finally, the realization of digital double-closed-loop with four-state bias was brought forward detailedly.Thirdly, in order to be able to meet the needs of different applications of fiber-optic gyro,and realize optimal design of parameters of fiber-optic gyro system,as well as master the relationship between the system parameters of FOG and performance parameters, established and simulated the digital double-closed-loop model of FOG. Comparison of two different modulate-demodulate scheme was made, and advantage of digital double closed-loop with four-state bias was proved effectively, and an effective route was brought forward to improve the accuracy of the FOG.Finally, in order to alleviate the pressure on the modulate-demodulate circuit, and improve the accuracy of FOG, noise reduction method of forward linear prediction filter (FLP) based on normalized least mean algorithm (NLMS). Firstly,all noise sources of FOG system was analysed, and their characteristics were described using the Allan variance, then made research deeply on the FLP and NLMS theories. At last, noise reduction was dealt with the real-time data of FOG, and the effectiveness of the FLP noise reduction based on FLP was proved, this provides another effective way to improve the accuracy of fiber optic gyroscope.