Research On The Physical Field Analysis And Coupling Characteristics Of Marine Fiber Optic Gyroscope

The fiber optic gyroscope(FOG)is the core component of the third generation inertial measurement combination and also a kind of angular velocity sensor based on the Sagnac effect.With the advantages of full solid state,high dynamic state,low cost,light weight,long life and large dynamic range,the fiber optic gyroscope has been widely applied to ships,submarines and various Marine carriers.After years of development,China’s fiber optic gyroscope technology has become more and more mature,especially the breakthroughs in optical fiber coil winding and other key technologies which makes it possible to further develop highprecision fiber optic gyroscopes.For meeting the requirements of high accuracy and long endurance of Marine fiber optic gyroscope navigation equipment,the fiber coils with large diameter and long distance are often selected.With the increase of optical fiber length,the difficulty of fiber coil winding is increasing,and its sensitivity to temperature and stress and other environmental physical fields will also increase significantly.Therefore,the study of environmental adaptability in the case of complex physical field is an important part of Marine fiber optic gyroscope engineering application research.In this context,this paper has further studies the influence of the fiber optic gyroscope temperature-stress crosslinking coupling effect on optical fiber transmission characteristics,set up fiber optic gyroscope drift error model considering temperature field,stress field and other conditions,revealed the relationship among the gyroscope drift with the physical field and various parameters of the fiber coil,and looking for means to suppress drift error.The research work of this paper mainly includes the following aspects:Firstly,analyzing the effect of the temperature field and stress field on the fiber refractive index and length variation,and the expression of non-reciprocal phase difference of fiber coil is deduced.And the factors that are ignored in previous analyses such as the fiber coil equivalent radius,length variation,fiber tail asymmetry and cross layer leaping are added to the error model on the basis of the further non-reciprocal phase difference expression and the Sagnac effect.It has respectively defined the fiber coil weight matrix and physical field matrix,and then the original gyroscope drift error with summation form is deduced to the form with four pairs of matrix according to the inner product theorem of the matrix space.It is not only makes the error model more concise and understandable,but also improves the operation efficiency.In the end,the formula of the standard quadrupolar fiber coil weight matrix is derived,and the establishment of the inner-product fiber optic gyroscope drift error model with temperature field,stress field and multi-factor conditions is completed.Secondly,the boundary conditions of the fiber coil are determined by the simulation analysis of fiber optic gyroscope finite element model,and the three-dimensional physical model of fiber coil containing fiber core layer,coating layer,adhesive,packing paper and various materials is further established.The internal temperature and stress distribution of the fiber coil(X direction stress,Y direction stress and Z direction stress)are analyzed in detail.Combined with the error model of the fiber optic gyroscope,the calculation of gyroscope drift error is accomplished under the temperature field with the stress field coupling.,and analyzing the importance of symmetry of physical field distribution in fiber coil to the suppression of gyroscope drift error.Finally,using the stress analyzer and the high and low temperature test chamber to respectively measure the gyroscope output by the internal stress distribution and the temperature changing environment of the fiber coil under constant temperature condition,and it verified the correctness of the gyroscope drift error model based on temperature field,stress field and multiple error factors in this paper and also the fiber coil physical model with considering multiple material parameters.Further,based on the proposed fiber optic gyroscope drift error model and the fiber coil physical model,the influence of the number of fiber coil layers,the number of loops,the inner diameter,the cross section ratio and other dimension parameters,the fiber diameter and coating material,the adhesive material and the uniformity and other parameters on the gyroscope drift error are quantitatively analyzed,and it provides guiding principles for the design of fiber coil dimension parameters,optical fiber and adhesive material selection,also it is helpful to improve the adaptability of the fiber optic gyroscope and improve the precision of the gyroscope.Finally,aiming at the defects of the standard quadrupolar winding fiber coil,and starting from the two aspects of reducing the physical field change rate of fiber coil and improving the quality of fiber coil winding,the method of adding buffer layer,layer by layer leaping and eliminating the packing paper dependence and other methods are used,and an improved quadrupolar winding pattern is proposed.The mathematical model and the physical model of the improved quadrupolar winding fiber coil are established and the numerical calculation of the distribution of the inner physical field of the fiber coil is completed.The simulation proves that the improved fiber coil is better than the standard fiber coil,which can reduce the gyroscope drift error and improve the environmental adaptability.Finally the experimental results show that the improved quadrupolar winding fiber coil is good for the control of gyroscope drift error.