Design Of Signal Detection And Control System For Resonator Optic Gyro

Gyroscope is the key sensor of inertial guidance and navigation,which is used to measure the angular velocity of the motion carrier.Optic gyro is a kind of angular velocity sensor based on optical Sagnac effect,w hich has the characteristics of short start-up time,long life and high reliability.The key component of the resonator optic gyro(ROG)is the optical resonator,which can obtain a higher resolution with a short fiber and integrated waveguide.Therefore the ROG can be easily integrated and has a strong ability of anti-electromagnetic and large dynamic range,which possess great research value.The principle of ROG is detecting the resonator frequency difference signal to get the rotation angular signal.However,the resonator frequency difference signal is extremely weak,and easily affected by such environment factors such as vibration,temperature drift,optic noise.Therefore,it's severe hard to directly measure the frequency difference signal of the two oppositely propagating beams in the resonator.The study of the signal detection and control system for ROG is of great significance for improve the gyro system signal-to-noise ratio and the precision of gyro output rotation signal.Aiming at the technical problem above,several aspects of research were carried out as in the following:(I)First,the principle of ROG is introduced,and the transfer function of optical ring resonator is derived.Though changing the parameter of the ring resonator,the resonant characteristics of the ring resonator is studied,which lays the basis for establishing the detection system.(2)According to the feature of the weak signal of the output of resonator fiber optic gyro,in this paper.the closed loop frequency-locking scheme is adopted.By the means of modulation and demodulation of sine wave and correlative detection,a high signal-to-ratio gyro output signal is obtained.The output frequency of the laser is tuned though the feedback signal,which make the operating point located in the resonant frequency of the resonant characteristic curve and solve the problem of the measurement sensitivity brought by small frequency difference caused by the Sagnac effect.(3)Choose the digital sinusoidal modulation technology based on Field-Programmable Gate Array(FPGA)as the ROG signal detection scheme.solve the problem of traditional analogy circuit with the characteristics of poor stability and ease to be jammed.In the aspect of signal modulation method,a wave modulation signal with higher frequency sine is adopted and a high signal-to-noise ratio signal is obtained..(4)The designed digital modulation system is realized by using digital circuit method and integrated into the FPGA,which is beneficial to the miniaturization and integration of the gyro system.The system mainly includes three modules,the generation of modulation signal,and sy nchronization demodulation.PI feedback control.Considering the fact that there is a initial phase difference between the measure signal and the modulation signal,we designed the digital dual-phase lock-in amplifier(LIA),which can achieve the amplitude detection of the weak measured signal.Though the comparison between the designed LIA and the analogy LIA,the result shows that the linearity of 0.99977 of the demodulation curve is obtained,which is increased by 20%than the analogy LIA.Though the design above,finally the feedback control of the closed loop and the tracking and locking of the resonant frequency of the fiber resonator is realized.