Design And Optimization Of Signal Detection System In Resonant Fiber Optic Gyro

Fiber Optic Gyro(FOG)is a high-precision inertial angular velocity sensor based on optical Sagnac effect.It plays an important role in inertial navigation systems.Its accuracy directly affects the performance of inertial navigation systems.In recent years,resonant fiber optic gyro(RFOG)is currently a hot topic in the world.RFOG measures the angular velocity of the system relative to the inertial space by measuring the resonant frequency difference of the two waves propagating in opposite directions in the fiber resonant ring(FRR).However,since the Sagnac effect is rather weak,the design of the signal detection system in RFOG is also very significant,and the accuracy and optimization of the detection system directly determine the measurement precision of the gyro.RFOG's signal detection system is divided into analog and digital.Because the digital system is stable,anti-interference ability is strong,and the running speed is fast,thus,this topic uses digital signal detection system.The relevant signals are detected and processed using a field programmable gate array(FPGA)chip.The main research contents and results of this paper are as follows:Analyzing the optical Sagnac effect,the relation between the measured physical quantity and angular velocity of the both interferometric FOG and resonant FOG,and the output spectrum of the FRR and its characteristics.And introducing the optical path structure,circuit structure and program modules within the FPGA chip of the RFOG in the subject.Studying the implementation of some related basic algorithm programs in the FPGA chip.Analyzing the conversion of digital and analog quantities,and optimizing the algorithm,including the trigger delay method to implement the double-edge triggering of the clock and the arbitrary frequency division.Using the phase accumulation method and the recursive formula method for generating digital waves.And optimizing digital waves such as glitch cancellation techniques,solutions to wave voltages beyond the output range,and the like.Designing and optimizing the signal detection system.Firstly,analyzing the output characteristics of the FRR after the phase modulation of the light wave.And then,formulating the demodulation algorithm based on the analysis result.In the demodulation algorithm of subtracting samples,the method of real-time subtraction in the sampling process is proposed,which doubles the update frequency of the demodulated value,and the optimal modulation parameters is obtained through theoretical simulation.Formulating the control scheme of the frequency-locked feedback loop.Clarifying that the PID control process is essentially a onetime integration(summation)control process with a window function.A method of subtracting demodulation values is proposed to cancel the synchronous fluctuation of the demodulation values of the two optical waves,thereby improving the measurement accuracy of the gyro system.The serial communication system is adopted to directly send the output information of the gyro to the host computer,which avoids the second noise addition of the DA converter and the amplifier,and improves the accuracy of the test.Finally,the simulation and experimental results are compared and analyzed,including resonance curve and demodulation curve,the performance test of the frequency-locked feedback loop,the calibration,the fitting and the accuracy test of the output signal.