Research On Magnetic Shielding Technology Of Fiber Optic Gyroscopes

With its non-moving parts,large dynamic range,flexible design and long life,the fiber optic gyroscope has occupied a dominant position in many navigation fields such as land,sea and air.With the continuous improvement of the precision of fiber optic gyro,the precision of fiber optic gyro is restricted.Many factors have gradually emerged,including temperature,magnetic field,vibration and so on.The influence mechanism of the magnetic field on the accuracy of the fiber optic gyroscope mainly includes the magneto-optical Faraday effect and the Faraday non-reciprocal phase shift caused by the geometric torsion of the fiber.There are many kinds of suppression schemes for the fiber optic gyroscope magnetic error,among which the easiest and most popular to implement is the magnetic shielding method.The so-called magnetic shielding method is to use a magnetic shield to isolate the fiber ring from the external magnetic field.However,there is currently no systematic guidance theory in the design of the fiber optic gyro magnetic shield,which makes the design scheme often not optimal.In view of the above problems,this paper studies the factors affecting the magnetic shielding effectiveness of the magnetic shield,and finds the correlation between it and the shielding effectiveness,in order to provide corresponding theoretical support for the next magnetic shield design work.The significance of fiber optic gyro magnetic shielding technology for the development of high-precision fiber optic gyroscopes is introduced.Then the recent developments of fiber optic gyroscope magnetic shielding technology at home and abroad are briefly introduced.Then the problems and shortcomings of fiber optic gyroscope magnetic shielding cover design are analyzed.Furthermore,the paper briefly introduces the mechanism of the magnetic error of fiber optic gyro,which is divided into two parts: radial magnetic field error and axial magnetic field error.Then the basic theoretical basis of fiber optic gyro magnetic shielding cover design is carried out.Furthermore,the finite element simulation software COMSOL Multiphysics used in the design of fiber optic gyro magnetic shield is introduced,and the feasibility of the application of finite element simulation software in magnetic shield design is demonstrated by the method of physical entity experiment.The results show that the application of finite element simulation software in the design of magnetic shield is reasonable and feasible.Then,based on the finite element method,the magnetic permeability of the material used in the fiber optic gyro magnetic shield,the thickness of the magnetic shield,the number of layers of the magnetic shield,the layer spacing,the size of the vias on the magnetic shield and its distance from the fiber,the size of the gap on the magnetic shield,seven factors affecting the shielding effectiveness of the magnetic shield were studied and useful conclusions were obtained.Finally,according to the conclusions obtained by the above research,a new type of annular cavity magnetic shield is designed by selecting the optimal scheme.The new magnetic shield not only saves the materials and space used,but also proves through simulation experiments.The magnetic shield has better shielding performance indicators and fully meets the requirements of the attenuation level of the external interference magnetic field of the navigation-grade fiber optic gyroscope.