Design Of Resonant Fiber Optic Gyro Digital Signal Detection System

Fiber optic gyro is a high precision inertial angular velocity sensor based on optical Sagnac effect,it plays an important role in navigation and guidance.Compared with an interferometric fiber optic gyroscope that is the first generation of fiber optic gyroscopes,the fiber length needed for resonant fiber optic gyroscopes(RFOG)to achieve the same accuracy is much shorter.Therefore,the advantage of high precision and miniaturization is obvious,research RFOG is more meaningful.RFOG measures the rotational angular velocity of an object by measuring the resonant frequency difference of two light waves traveling opposite to each other in the fiber optic ring resonator of its sensitive component.Since the Sagnac effect is a very weak effect,the signal detection system occupies a very important position in the RFOG,the accuracy of the detection system will directly affect the final accuracy of the gyro.RFOG signal detection methods are mainly divided into analog and digital,because the digital circuit has good stability,anti-interference ability,high processing speed and other advantages,so the digital signal detection system is the best choice for RFOG.The main research contents and achievement of this paper are as follows:(1)Design modulation modules based on triangle waves and sine waves.Analyze the modulation principle of triangle wave and sine wave,and implement the production of triangular wave and sine wave modulation signal on FPGA.Starting from improving the performance of the demodulation curve,the frequency and peak-to-peak parameters of the two modulated signals were optimized and selected.(2)Design demodulation module based on triangle waves and sine waves.Triangular wave demodulation module is designed according to the principle of triangle wave demodulation,when the triangle wave is modulated,the up-down jump-distorted signal appears,and the signal filtering processing technology is proposed to improve the performance of the demodulation curve.Sine wave demodulation module was designed based on the digital phase-locked demodulation principle and the CORDIC algorithm,and achieved synchronous demodulation of sine wave signal.(3)Design resonant frequency locking module based on PI controller.According to the characteristics of the resonance curve after the modulation and the resonance point,the resonant frequency locking module was designed by using the Into Valley Criterion algorithm and PI controller,and achieved the locking of one resonant frequency,the locking time is1.56 ms.(4)Design communication module based on serial communication.Establish communication system between the FPGA and PC,which can achieve real-time modification of module parameters in FPGA and high-speed sampling of signal data in FPGA.Through the work above,established the RFOG experimental system.Tested resonant curves and demodulation curves under the triangle wave modulation and sine wave modulation,and get the characteristic parameters of the curve.Tested the locking time of the system,and it was proved that the system can well achieve the tracking and locking of one resonant frequency.Tested the actual rotation signal and gyro bias of the system,get the gyro bias is 0.279°/s,the bias stability is 474.31°/h,and the scale factor is 0.00759V(°/s).