Interferometric integrated optic gyroscope usually applies a square wave phase modulation signal, namely two state modulation or four state modulation, between two back-propagation light waves. The amplitude of square wave phase modulation is π/2, and the modulation frequency is the intrinsic frequency of the sensitive loop. Based on this unique demodulation method, it is inevitable to generate a spike pulse signal at the output signal end of the detector. This spike pulse signal can cause transient saturation in the front or rear amplifier of the detector, and signal distortion will occur when the detector recovers from this overload state; The asymmetry of peak pulses can generate odd harmonic interference coupled into useful signals, resulting in errors during demodulation and increasing the output noise of the gyroscope. Therefore, it is necessary to process the spike pulse. This article theoretically analyzes the reasons for the output noise of the gyroscope caused by spike pulses, and adopts a method to avoid the impact of spike pulses. Simulation shows that this method not only eliminates spike pulses, but also eliminates odd harmonic interference induced by spike pulses. The experimental comparison shows that this method significantly improves the accuracy of the gyroscope.
During the vibration process, the output of the gyroscope will add a non-zero offset small amount based on the Earth's rotational speed component, which is the output error term of the gyroscope vibration. When the gyroscope adopts two different closed-loop models, the error magnitude of the same gyroscope is different. Therefore, selecting an optimal closed-loop model while adjusting appropriate closed-loop parameters is crucial for solving the vibration problem of gyroscopes. Firstly, compare the differences and stability conditions between the two closed-loop models; Secondly, analyze the reasons for the error terms generated during the vibration process of the gyroscope and the reasons for the different sizes of error terms generated by different models; Then simulate and analyze the output of gyroscope vibration under different closed-loop models. The simulation and specific experimental results indicate that selecting an optimal closed-loop model shortens the closed-loop integration delay time of the model, and maximizes the closed-loop gain as much as possible while ensuring that there are no resonance peaks in the closed-loop amplitude frequency characteristic curve. This can reduce the output error term of the gyroscope and improve its dynamic performance.
Process initial alignment and azimuth estimation algorithm is an important technology of the land vehicle Strapdown Optical Fiber Positioning and Orientation System (SOFPOS). The initial alignment of the vehicle is easily affected by the maneuvering environment such as turning and the noise of the odometer, especially when turning sharply, the alignment accuracy of the optical fiber system will be reduced. Firstly, this paper analyzes the principle of odometer lever arm error and the measurement compensation method in the SOFPOS. A comprehensive physical model based on the longitudinal lever arm and the left and right lateral lever arms is proposed, and the odometer lever arm error model is also simulated. Then, the lever arm error is estimated by Kalman filter, and the odometer lever arm error is compensated. Finally, the compensation is applied to the initial alignment and azimuth estimation algorithm during the journey, and the experimental verification is completed by combining the hardware-in-the-loop simulation. The test results show that the alignment accuracy and positioning accuracy of the positioning and orientation system can be effectively improved by estimating and compensating the error of the odometer lever arm, and the environmental applicability of the land vehicle optical fiber positioning and orientation system can be improved.
With the rapid growth of the demand for various unmanned platforms, such as small Unmanned Aerial Vehicles (UAVs), small Autonomous Underwater Vehicles (AUVs), Unmanned Underwater Vehicles (UUVs), and driverless vehicles, the miniaturized, integrated, and large-scale production of interferometric Fiber Optic Gyroscopes (FOGs) and the fiber-optic inertial navigation have become an important research field. This paper first introduces the research status of integrated chip gyroscope, and then designs a miniaturized interferometric integrated optical gyroscope based on silicon lithium niobate thin waveguide, focusing on the structural design of silicon lithium niobate thin waveguide. The high efficiency microwave/light wave interaction problem of silicon lithium niobate thin waveguide electro-optical modulation is solved, the volume of optical modulator is significantly reduced, and the half wave voltage of optical modulator is reduced. Polarized waveguide is added to realize the function of traditional lithium niobate waveguide modulator. Finally, due to the stable chemical properties and high hardness of lithium niobate material, it is difficult to process it with conventional silicon waveguide etching process. This paper has conducted a preliminary study on its low loss processing technology. Although the silicon lithium niobate thin waveguide can significantly reduce the volume of the FOG and improve the integration of the FOG, due to the large gap between the size of the thin waveguide and the single-mode fiber core, if the direct alignment coupling is inevitable, a large coupling loss will be introduced. It is necessary to further study the low loss optical coupling technology of silicon lithium niobate to meet the requirements of miniaturized and integrated FOG.
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