Research On Vibration Characteristics Of Fiber Optic Gyroscope Strap-down System

Nowadays, fiber optic gyroscope (FOG) which develops from the low and medium precision application fields to high precision application fields, trends to replace electromechanical gyroscope and laser gyroscope. It has become the main instrument applied in inertial navigation and strategy fields. Currently, FOG is widely applied in military and civilian fields abroad, and it's vibration characteristics has also been solved successfully. The research on FOG starts relatively late in our country. Though great achievement has been made, but in certain key technology areas (such as vibration characteristics) it remains to be improved further. In this paper, interferometric fiber optic gyroscope has been regarded as the object of study to research the vibration characteristics of FOG with its maximum reduction to the impact on the output accuracy of FOG under vibration, so as to enhance the accuracy of fiber optic gyro strapdown system.In this paper, firstly, a brief introduction to the basic principles of fiber optic gyroscope has been made. Then, the mathematical model of the closed-loop fiber optic gyroscope has been established to analyze the fiber optic gyroscope system in time domain and frequency domain. The response curves of non-vibration and vibration conditions are simulated based on the getting of the transfer function of FOG.. It can be seen from the response curves that the fiber optic gyroscope system is a first-order system, and it is still a first-order system to restore to stability state under vibration.Secondly, the influence of fiber coil winding to the performance of FOG is analyzed. The phase shift equation of the influence of external pressure on fiber coil and the phase difference equation of the influence of vibration in ideal circumstances are brought out. The influence of fiber coil windings to vibration phase error is analyzed, and the vibrant error equations of different windings are brought out. The analysis of the influence of quadrupole winding on phase-shifting because of vibration is regarded as the focus. Combined with elastomer fluctuation equation, the drift error equation of FOG is brought out. The factors which influence the drift of FOG under vibration are simulated.Finally, FOG Inertial Measurement Unit (IMU) and the components of FOG are tested under vibration. The light source, coupler, Y waveguide and fiber-optic rings are tested respectively for their output power, extinction ratio and spectral wavelength, then the conclusion is reached that the influences of vibration on fiber coil and the tail fiber of Y waveguide are greater than other components. The vibration error compensation model which can predict vibration error, is established with the use of Elman neural network. To compensate the error of FOG Strap-down Inertial Navigation System in initial alignment, good compensation effect is got.