Research On Signal Detection And Control Technology Of Resonant Fiber Optic Gyro

Gyroscope is a kind of inertial sensor used for measuring angular motion state.It is the main sensitive device of inertial navigation system and widely used in aerospace and other fields.Resonant fiber optic gyro(RFOG)is an optical gyro based on Sagnac effect,the core sensing element of RFOG is Fiber Ring Resonator(FRR),which generates resonant phenomenon through the transmission of light wave in the FRR.At work,two light waves exist simultaneously in the FRR,along the clockwise and counterclockwise transfer respectively.When the gyro angular motion as the carrier,two beams of light waves in optical transmission distance difference resonance frequency difference,under the influence of angular velocity difference and the resonance frequency is proportional to vehicle movement,so as long as the measured resonance frequency difference can get accurate angular motion information.This paper starts from the measurement principle of RFOG,combines the optical principle and the sensitive process of the FRR,determines the basic structure of the RFOG,and designs a signal detection and control system according to its signal characteristics.This paper mainly carries out the following research work:Based on the Sagnac effect,the optical principle of the RFOG and the principle of the FRR sensitive angular velocity were deeply analyzed to determine the structure of the reflective FRR and design the basic optical path of the RFOG.Furthermore,the transmission model of optical signal in the FRR is established.This paper enumerates several main noises in the RFOG system and their effects on the system signals.Finally,based on the above analysis,the optical path construction of the RFOG is completed.Based on the analysis of the basic principle of RFOG,establishes the signal detection and control system of RFOG,which includes digital sine wave modulation module,synchronous demodulation module and laser frequency locking module.The digital sine wave modulation module is used to generate sinusoidal signals loaded in the phase modulator to modulate the light wave,and the synchronous demodulation module is used to detect the weak signals representing the resonant frequency of the photodetector output.The laser frequency lock module is used to adjust the center frequency of the laser output light wave.The designed signal detection and control system is realized by hardware,and the FPGA chip is designed as the core of the detection system circuit board.In addition to the minimum FPGA system,it also includes A/D module,D/A module,communication module and power module,etc.,and selects appropriate chips according to the work requirements of the system.The above modules were integrated into a PCB,which served as RFOG system board after debugging and testing,and undertook the tasks of signal input,modulation waveform output and gyro data output.After the design of RFOG optical circuit and circuit,a prototype of RFOG system was built on a simple platform.The results of modulation and demodulation test show that the basic work of gyro can be preliminarily realized,and the feasibility of RFOG detection system design in this paper is verified.The preliminary design of RFOG system is realized,which lays a hardware foundation and experimental platform for the follow-up measurement of rotation signal,signal noise research and system optimization design.