Studies On The Technique Of The Fiber-optic Gyroscope For Improving Performance

A gyroscope as the core components of the inertial guidance, navigation andattitude has been developed three generations. The first generation of electromechanicalgyro due to it’s these disadvantages of performance to cost ratio, life-time and so on, isgradually being replaced by the optical gyros based on optical Sagnac effect. Thesecond generation of ring laser gyro (RLG) has made great process in the aspect ofprecision and reliability, which makes it to be widely used in the inertial navigationsystem. However, to solve “locking” phenomenon and added the mechanical jitterdevice in RLG, it makes RLG system to become very complex. This results in the thirdgeneration of gyro technology-Fiber Optic Gyroscope (FOG). FOG has theseadvantages of small size, low cost, wide range of precision, no moving part and so forth,which is widely used in the low and middle precision gyro applications currently.The interferometric FOG is a kind of FOG technology, and its fundamental theoryand technology have fully matured. But there is a huge gap compared the domestictechnology with developed countries in the developing level and precision of FOG. Dueto limitations of the production technologic level of the optical devices, the presenttechnologic measures rely mainly on the electronics and signal processing techniquesfor improving performance and enhancing the precision of FOG. So with the actualtechnical conditions the research of the relative technology about how to improve theperformance of FOG, has important theoretical significance and economic value for thetechnical development of FOG and engineering practice.In this dissertation the interferometric digital closed-loop FOG is as the object ofresearch. The research work about the improved performance-related technology ofFOG is to be carried out. The effecting factors and the improved performancetechnology of the three key indexes, Bias Stability, Angle Random Walk Coefficient andScale Factor, are researched mainly, which is employed to evaluate the performance ofFOG. In this article the main content and innovations can be summarized as follows:(1) According to the operation principle and the output signal characteristics of FOG, thedigital closed-loop fiber optic gyro’s dynamic model and random model areestablished. The main five types of random noise in FOG are simulated with themethod of digital signal simulation. The random model and the simulation methodof noise are verified by Allan variance analysis and comparison of the real gyro’soutput data. (2) To study the main factors which causes Scale Factor error and the compensationtechnologies of Scale Factor error are introduced. The effectiveness of the gain errorcompensation technology based on the four-state square-wave modulation is provedwith simulation of the model.(3) To study the main factors of impacting Angle Random Walk Coefficient and SNR ofFOG. To solve the problem of the source Relative Intensity Noise (RIN) limiting toenhance SNR of FOG, the three suppression RIN technologies and their drawbacksare studied and a kind of the adaptive noise cancellation technology based on RLSalgorithm is proposed in this paper. The simulation shows that this technology has astrong ability to meet the change of the transfer delay and amplitude of RIN and theFOG’s Bias Stability and Angle Random Walk Coefficient have been improved in acertain extent after using this technology.(4) According to the FOG’s signal characteristics of nonlinearity and nonstationarity, tostudy and compare the LMS adaptive filter algorithm at different step size and theorders of filter. The principle to determining the LMS filter’s parameters result fromthe experimental results. To avoid the drawbacks of LMS filter algorithm, thefiltering technology based on Non-parametric, Variable Step Size Normalized LMS(NVSS-NLMS) algorithm is proposed. The experiment shows that this technologycompared to LMS algorithm has a better filtering effect.(5) To avoid how to choice the appropriate reference signal for the adaptive filteringalgorithm, the Empirical mode decomposition (EMD) filtering technology isresearched, which based on different time scale of the local characteristics in signalitself inclusively. To solve how to reconstructed signal for EMD, a method based onsequence Mean Square Error (MSE) detection is proposed, which provides anobjective criterion for signal reconstruction of EMD filtering method. By filteringthe signal of FOG, the index of Bias Stability and Angle Random Walk Coefficientare enhanced in a great extent.