Research On Double Closed-Loop Detection Technology Of Resonant Optic Gyro

Resonant optic gyro(ROG)is an angular velocity sensor based on Sagnac effect witch has a wide application prospect in the field of inertia.In order to realize high precision and miniaturization of gyro system,it is necessary to design a closed-loop detection system.In this paper,a double closed-loop ROG based on FPGA is designed and implemented,and the performance of each component of the detection system and the whole gyro system is tested.This paper mainly carries out the following work:(1)The optical Sagnac effect and the sinusoidal phase modulation technology of ROG system are introduced,the formula of sinusoidal phase modulation and demodulation technology is derived,used to theoretically calculate the optimal wave amplitude and optimal frequency of modulation signal,and the optimal wave amplitude and frequency are verified by experiment.The laser's resonant frequency servo loop and the resonant frequency servo loop based on phase modulation(PM)of the double closed-loop ROG system are introduced,and the optimal amplitude and step duration of the digital sawtooth signal are analyzed.(2)The circuits of each double closed-loop ROG system's module are designed,including the signal output module(digital to analog converter,signal amplification module and signal generation module),the signal acquisition module(signal amplification module,switch module,lock-in amplifier and analog to digital converter),servo loop module;The demodulation output which is modulated by square wave with different duty cycle and modulation coefficients is theoretically analyzed.The output has a peak value at resonant frequency,which can be used to suppress carrier,calculate angular velocity and lock resonant frequency.The method of resonant frequency locking is optimized,which uses frequency sweep based on sawtooth wave and two-stage DAC to control the laser frequency to realize fast and accurate resonant frequency locking.(3)A ROG system composed of the double closed-loop detection system is built,and the resonance curve of resonator,demodulation curve,accuracy of the resonant frequency servo loop,gyro bias stability and linearity are tested.With integration time of 1 s and test time of100 s,the locking precision of the laser's resonant frequency servo loop is 0.278 °/s which is improved by a factor of 4.14.The gyro bias stability is 39.4355 °/s with integration time of 1 s and test time of 1 h.