Research On Fiber Optic Gyroscope Demodulation Technology Based On FPGA

Fiber optic gyroscope is a kind of angular velocity sensor based on Sagnac effect.Compared with the traditional electromechanical gyroscope,it has the advantages of large measurement range,strong stability,electromagnetic interference immunity and small volume.At present,the phase modulation of fiber optic gyroscope is based on the transit time of fiber coil.The transit time will affect the size of the fiber coil,the phase modulation frequency and the sampling rate of fiber optic gyroscope.So the accuracy of the transit time will seriously affect the measurement accuracy of the fiber optic gyroscope,and the transit time will also limit the dynamic range of the measurement.In this paper,a phase modulator based on spatial phase modulation is applied to fiber optic gyroscope.A demodulation scheme based on this phase modulation method is proposed.The mathematical model of digital closed-loop fiber optic gyroscope is established and simulated.FPGA is used to realize the digital signal demodulation of fiber optic gyroscope.The main contents of this paper are as follows:Firstly,the detection principle of fiber optic gyroscope is introduced,the basic structure of fiber optic gyroscope is given,and the reason why fiber optic gyroscope needs phase modulation is explained.The structure of spatial nonreciprocal phase modulator is proposed,and the mechanism of phase modulation is analyzed based on the theory of crystal refractive index ellipsoid.Finally,a scheme of phase demodulation is proposed,which provides a theoretical basis for the following analysis.Secondly,the dynamic model of the digital closed-loop fiber optic gyroscope is analyzed,and the mathematical model is abstracted to calculate the closed-loop transfer function of the system.Then the system parameters of each part of the mathematical model are established,and the closed-loop system is simulated to obtain the output response of the system under different input conditions.The dynamic response and bandwidth of the system are calculated.Thirdly,FPGA is used to realize the signal processing of the digital closed-loop fiber optic gyroscope.According to the designed system scheme,the specific functional modules inside the FPGA chip are given.Each module is programmed by hardware description language to realize its software design.The corresponding circuit core is selected and connected to realize its hardware design.Finally,the logic simulation and simulation test of the gyro signal processing system are carried out to verify the correctness of the gyro control system,and the causes of system errors in the process of signal processing are analyzed.