Deformation Mechanism Of Fiber Ring Of Fiber Optic Gyroscope In Accelerating Field

Fiber optic gyroscope is a sensor based on inertial space to measure the angular velocity of object motion,which is used in inertial navigation system and attitude positioning.Due to the advantages of good stability,high reliability,and long service life,gyroscopes are widely used in the field of inertial navigation.In the actual operation process,the gyroscope is often fixed with the spacecraft carrier and plays the role of inertial navigation.Because the carrier movement will produce large maneuvering and high vibration load,which will cause the fiber optic gyroscope to suffer a great impact and produce large maneuvering load.As the core component of the optical part of the gyroscope,the fiber-optical ring is an optical component that is sensitive to the angular rate in the gyroscope.It is made of optical fiber wound in a certain winding method,and different winding methods will affect the performance of the fiber coil under temperature or stress.Under the action of the large maneuvering load of the spacecraft,the fiber-optical ring will undergo structural deformation,which will directly affect the test accuracy of the gyroscope.Based on the theoretical basis of anisotropic composite materials,this paper carried out the finite element analysis of the representative volume element(RVE)of composite micromechanics on the fiber-optical ring to obtain its equivalent material parameters.Then the spatial finite element model of the fiber-optical ring assembly of the gyroscope was established under different acceleration fields.The structural deformation of the fiber-optical ring was analyzed under different acceleration fields,and the factors that affect the structural deformation of the fiber-optical ring was researched.According to the arrangement plan of the adhesive in the gyro,the optimal structural deformation scheme was obtained through simulation analysis.The dynamic response of the fiber-optical ring of the fiber-optical ring gyroscope was carried out to analyze the calculation results of the large maneuver load.The main research contents are as follows:(1)Based on the theoretical knowledge of anisotropic materials,The elastic parameters of the fiber-optical ring were calculated by the meso-mechanical finite element method.According to the geometrical distribution of the cross section of the fiber-optical ring,the RVE elements of the fiber-optical ring meso-structure were determined,and the periodic boundary conditions were applied to achieve the stress continuity and displacement continuity between different RVEs The periodic boundary conditions include rigid body displacement constraints,in-plane node constraints,edge node constraints and vertex constraints.Six groups of linearly uncorrelated macroscopic stress fields were applied to the RVE model,which were converted into a method of applying a vertex concentrated force.The elastic material parameters of the equivalent fiber-optical ring were calculated by the equivalent constitutive equation of orthotropic composite.(2)The parameters of the top cover,the parameters of the U-groove and the equivalent material parameters of the fiber-optical ring were used to establish the finite element model of the fiber-optical ring assembly.Under different acceleration fields,the calculation results of the fiber-optical ring assembly were analyzed to get the mechanism of the fiber-optical ring change.It was found that the influencing factors of the structural deformation of the fiber-optical ring include the contact coupling effect of the fiber-optical ring with the U-shaped groove and the top cover,the structural deformation of the U-shaped groove and the top cover,and the deformation caused by the structure of the fiber-optical ring body.The former two have a greater influence and the contact coupling effect causes nonlinear deformation of the fiber-optical ring,which would affect the precision of the measurement of the misalignment Angle of the fiberoptical gyroscope.(3)In view of the deformation and nonlinear deformation of fiber-optical ring under the high acceleration field of large maneuvering,the optimization schemes of the deformation of fiber-optical ring were designed.Because the fiber-optical ring is bonded in the fiber ring assembly by curing adhesive,different arrangement will produce different deformation of the fiber-optical ring under the acceleration field.Therefore,four kinds of adhesives were selected in the layout of fiber ring assembly.The fiber-optical ring of the gyro was placed under different acceleration fields.And the simulation analysis was carried out to get the optimal adhesive layout scheme with the smallest deformation.(4)In order to study the deformation of the fiber-optical ring of the gyroscope during the large-scale maneuvering process of the spacecraft,the transient response analysis of the fiberoptical ring assembly was carried out by applying acceleration excitation,and the key nodes of each part of the fiber-optical ring assembly were selected,and the calculation results were obtained.The dynamic response curve of nodal displacement,velocity,acceleration and stress shows that the fiber-optical ring is prone to high-frequency and small-amplitude oscillations during large maneuvers,which has a significant impact on its measurement accuracy.