Method for optimizing distance between double-layer magnetic shielding structures in fiber-optic gyroscope

Abstract

The invention discloses a method for optimizing the distance between double layers of magnetic shielding structures in a fiber-optic gyroscope, and solves the problems that the existing double-layer magnetic shielding fiber-optic gyroscope cannot accurately determine the gap between the double layers of magnetic shielding structures, so that materials are wasted, the weight of the fiber-optic gyroscope is increased, or the anti-magnetic interference capability is poor, and the fiber-optic gyroscope cannot accurately determine the gap between the double layers of magnetic shielding structures. The method comprises the following steps: step 1, building a three-dimensional model; 2, the three-dimensional model is placed in a radial magnetic field and an axial magnetic field for finite element simulation, and the magnetic field intensity average value of the optical fiber ring in the radial magnetic field and the axial magnetic field is obtained; 3, calculating to obtain the maximum output error of the fiber-optic gyroscope in the radial and axial magnetic fields; 4, judging whether the maximum output error of the fiber-optic gyroscope meets the technical index or not; and step 5, outputting the spacing of the double-layer shielding structure.

Description

TECHNICAL FIELD

[0001] The present application relates to a double-layer magnetic shielding fiber-optic gyroscope, and in particular to a method for optimizing the distance between double-layer magnetic shielding structures in a fiber-optic gyroscope. BACKGROUND

[0002] A fiber-optic gyroscope is a full solid-state photoelectric inertial instrument, which is widely used in inertial navigation systems due to its advantages of no moving parts, low cost, impact resistance, high sensitivity, long service life, large dynamic range, short start-up time, and wide precision coverage.

[0003] The working principle of a fiber-optic gyroscope is to detect the rotation angular velocity by using the Sagnac effect, and the detection of the Sagnac effect is based on the fact that the interference phase between two counter-propagating light waves in a fiber ring is completely caused by rotation. However, a fiber-optic gyroscope is easily affected by a magnetic field, resulting in a non-reciprocal phase difference, which affects the measurement accuracy of the fiber-optic gyroscope. In order to ensure the measurement accuracy of the fiber-optic gyroscope, the fiber ring usually needs to be subjected to magnetic shielding treatment.

[0004] When the fiber ring is subjected to magnetic shielding treatment, a single-layer or multi-layer magnetic shielding material is usually used to shield the fiber ring to reduce the influence of the external magnetic field.

[0005] Among them, a single-layer magnetic shielding structure can generally reduce the interference of the magnetic field to a certain extent, but in a complex or high-intensity magnetic field environment, the shielding effect may be insufficient.

[0006] A double-layer magnetic shielding structure not only can compensate and weaken the magnetic leakage between layers, but also has flexibility in material selection, thickness, and structural arrangement. Moreover, the layer spacing of the double-layer magnetic shielding will affect the output of the fiber-optic gyroscope, and the size parameters of the inner diameter, outer diameter, width, thickness, and height of the fiber ring used by different fiber-optic gyroscopes, as well as the material properties of the fiber itself, will have different sensitivities to external magnetic fields. However, how to determine the optimal distance between the double-layer shielding structures is still a problem that needs to be solved in the related field. On the one hand, too small layer spacing may cause strong coupling effect between the shielding materials, resulting in waste of material resources or poor actual shielding effect; on the other hand, too large layer spacing not only may cause the increase of the volume and weight of the entire fiber-optic gyroscope, making the assembly difficult, but also may affect the mechanical strength and installation reliability of the overall structure.

[0007] In the prior art, the gap between the double-layer magnetic shielding shells is generally adjusted mainly according to the installation space of the fiber optic gyroscope. If the installation space is sufficient, the gap between the double-layer magnetic shielding shells is increased as much as possible to meet the magnetic interference resistance of the fiber optic gyroscope, but such a processing method will cause waste of production materials and increase the weight of the fiber optic gyroscope. If the installation space is limited, the gap between the double-layer magnetic shielding shells is reduced as much as possible to meet the installation requirements, but such a processing method will cause poor magnetic interference resistance and reduce the precision of the fiber optic gyroscope.

[0008] Therefore, under the requirements of the magnetic shielding material, the space arrangement and the assembly process, accurately and specifically determining the distance between the double-layer magnetic shielding shells has important engineering application value for improving the magnetic interference resistance of the fiber coil and improving the precision of the fiber optic gyroscope. SUMMARY

[0009] The purpose of the present application is to solve the technical problems that the existing double-layer magnetic shielding fiber optic gyroscope cannot accurately determine the gap between the double-layer magnetic shielding shells, which either causes waste of materials and increases the weight of the fiber optic gyroscope, or causes poor magnetic interference resistance and reduces the precision of the fiber optic gyroscope, and to provide a method for optimizing the distance between the double-layer magnetic shielding structures in a fiber optic gyroscope.

[0010] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0011] A method for optimizing the distance between the double-layer magnetic shielding structures in a fiber optic gyroscope, characterized by comprising the following steps:

[0012] Step 1: Obtain a fiber coil assembly to be applied to a fiber optic gyroscope, the fiber coil assembly comprising a fiber coil, an outer shielding structure and an inner shielding structure, build a three-dimensional model of the fiber coil assembly by simulation, and set the distance between the outer shielding structure and the inner shielding structure to a preset distance d during the building of the three-dimensional model to obtain the three-dimensional model of the fiber coil assembly.

[0013] Step 2: Obtain a finite element simulation software, import the three-dimensional model of the fiber coil assembly obtained in step 1 into the finite element simulation software, set the magnetic property attributes of the materials of all components in the fiber coil assembly in the finite element simulation software, and then apply a preset magnetic field strength of a radial magnetic field and an axial magnetic field to the three-dimensional model of the fiber coil assembly according to the magnetic field environment applied to the fiber optic gyroscope to be applied, and simulate to obtain the average value B R of the radial magnetic field strength of the fiber coil and the average value B A of the axial magnetic field strength of the fiber coil.

[0014] Step 3: According to the average value B R of the radial magnetic field strength of the fiber coil and the average value B ABased on the wavelength and propagation speed of the incident light from the fiber optic gyroscope, the maximum output error Ω of the fiber optic gyroscope in the radial magnetic field is calculated. R The maximum output error Ω of the fiber optic gyroscope in the axial magnetic field. A ;

[0015] Step 4: Determine the maximum output error Ω of the fiber optic gyroscope in the radial magnetic field obtained in Step 3. R The maximum output error Ω of a fiber optic gyroscope in an axial magnetic field A Does it meet the technical specifications of fiber optic gyroscopes?

[0016] If Ω R ≤ Zero bias stability of fiber optic gyroscope, and Ω A If the zero-bias stability of the fiber optic gyroscope is less than or equal to that of the fiber optic gyroscope, then proceed to step 5.

[0017] If Ω R and Ω A If at least one of the components has a zero-bias stability greater than that of the fiber optic gyroscope, then return to step 1 and increase the spacing between the outer and inner shielding structures to d + Δd, until Ω R and Ω A All are less than or equal to the zero-bias stability of fiber optic gyroscopes;

[0018] Step 5: Output the Ω R and Ω A Correspondingly, the spacing between the outer and inner shielding structures optimizes the distance between the double-layer magnetic shielding structures of the fiber optic gyroscope.

[0019] Furthermore, 0.25mm≤d≤1.5mm, 0.05mm≤Δd≤0.1mm.

[0020] Furthermore, step 3 specifically involves:

[0021] Step 3.1: Based on the average value B of the radial magnetic field strength of the fiber optic ring obtained in Step 2... R The maximum output error Ω of the fiber optic gyroscope in the radial magnetic field was calculated and obtained. R The calculation formula is as follows:

[0022]

[0023] Among them, Ω R This represents the maximum output error of the fiber optic gyroscope in a radial magnetic field, expressed in ° / h.

[0024] R is the equivalent radius of the fiber optic ring, where R = (inner diameter of the fiber optic ring + outer diameter of the fiber optic ring) / 2, in meters; Δβ is the linear birefringence of the fiber itself in the fiber optic ring, in rad / m.

[0025] λ is the wavelength of the incident light of the fiber optic gyroscope, in units of nm;

[0026] c is the propagation speed of the incident light of the fiber optic gyroscope, in units of m / s;

[0027] V is the Verdet constant, in units of rad / m / mT;

[0028] B R is the average value of the radial magnetic field strength of the fiber coil, in units of mT;

[0029] t0 is the fiber torsion coefficient in the fiber coil, in units of rad / m;

[0030] Step 3.2 calculates and obtains the maximum output error of the fiber optic gyroscope in the axial magnetic field according to the average value B A of the axial magnetic field strength of the fiber coil obtained in step 2.

[0031] Further, step 3.2 is specifically:

[0032] Step 3.2 calculates and obtains the maximum output error of the fiber optic gyroscope in the axial magnetic field according to the average value B A of the axial magnetic field strength of the fiber coil obtained in step 2, and the calculation formula is as follows:

[0033]

[0034] Wherein, Ω A is the maximum output error of the fiber optic gyroscope in the axial magnetic field, in units of ° / h;

[0035] B A is the average value of the axial magnetic field strength of the fiber coil, in units of mT;

[0036] D is the diameter of the fiber in the fiber coil, in units of μm.

[0037] Further, the magnetic properties in step 2 include relative linear permeability and relative nonlinear permeability.

[0038] Further, the fiber coil assembly in step 1 includes a fiber coil, an inner shielding structure, a backing plate, an outer shielding structure, and a screw;

[0039] The inner shielding structure includes an inner upper cover and a base, the base is provided with the fiber coil, and the bottom surface of the fiber coil is connected with the bottom surface of the inner shielding structure;

[0040] The backing plate is located in the inner circle of the inner shielding structure, and the inner shielding structure and the outer shielding structure are fixed on the backing plate by the screw;

[0041] The outer shielding structure includes an outer upper cover and an outer lower cover, the outer upper cover and the outer lower cover form a containing cavity, the inner shielding structure is arranged in the containing cavity, and the two have a common center.

[0042] Furthermore, in step 2, the permeability input to the finite element simulation software includes the relative linear permeability of the fiber ring, the liner, and the screw, as well as the relative nonlinear permeability of the inner shielding structure and the outer shielding structure.

[0043] Compared with the prior art, the present invention has the following beneficial technical effects:

[0044] 1. This invention provides a method for optimizing the distance between double-layer magnetic shielding structures in a fiber optic gyroscope, utilizing the average radial magnetic field strength B of the fiber optic ring obtained through simulation. R and the average value of the axial magnetic field strength of the fiber optic ring B A Based on the basic parameters of the fiber optic gyroscope design, the maximum output error of the fiber optic gyroscope in the axial magnetic field and the maximum output error of the fiber optic gyroscope in the radial magnetic field are calculated. By judging whether the maximum output error of the fiber optic gyroscope in the axial magnetic field and the maximum output error of the fiber optic gyroscope in the radial magnetic field meet the technical specifications of the fiber optic gyroscope, the spacing between the inner shielding structure and the outer shielding structure can be adjusted or output in a timely manner to improve the double-layer magnetic shielding performance of the fiber optic gyroscope.

[0045] 2. This invention provides a method for optimizing the distance between double-layer magnetic shielding structures in a fiber optic gyroscope. It proposes a specific structure for the double-layer magnetic shielding design of the fiber optic gyroscope. By establishing a simulation model and substituting the magnetic field strength data obtained from the simulation into the formula, the maximum output error of the gyroscope in the magnetic field is obtained, thereby achieving a quantitative evaluation of the gyroscope output.

[0046] 3. The present invention provides a method for optimizing the distance between double-layer magnetic shielding structures in a fiber optic gyroscope. This method is highly applicable, accurate in calculation, and can meet the technical requirements of high-precision fiber optic gyroscopes in complex structural designs.

[0047] 4. The present invention provides a method for optimizing the distance between double-layer magnetic shielding structures in a fiber optic gyroscope. Based on the selection and determination of the spacing between the double-layer magnetic shielding structures using this method, not only can production costs be significantly reduced, but also the size and weight of the fiber optic gyroscope product can be reduced as much as possible while ensuring magnetic shielding performance, thereby effectively improving the double-layer magnetic shielding performance of the fiber optic gyroscope. Attached Figure Description

[0048] Figure 1 This is a flowchart of a method for optimizing the distance between double-layer magnetic shielding structures in a fiber optic gyroscope according to the present invention;

[0049] Figure 2 This is a partial cross-sectional view of the three-dimensional model of the fiber optic ring assembly used in an embodiment of the method for optimizing the distance between double-layer magnetic shielding structures in a fiber optic gyroscope according to the present invention.

[0050] Figure 3 for Figure 2Front view of the cross-section at point A;

[0051] Figure 4 This is an exploded view of an optical fiber ring assembly in an embodiment of a method for optimizing the distance between double-layer magnetic shielding structures in an optical fiber gyroscope and improving the performance of double-layer magnetic shielding in an optical fiber gyroscope according to the present invention.

[0052] Figure 5 This is a simulation of the magnetic field distribution of a double-layer magnetically shielded fiber optic ring in a radial magnetic field, representing an embodiment of the distance optimization method between double-layer magnetically shielded structures in a fiber optic gyroscope according to the present invention.

[0053] Figure 6 This is a simulation of the magnetic field distribution of a double-layer magnetically shielded fiber optic ring in an axial magnetic field, representing an embodiment of the distance optimization method between double-layer magnetically shielded structures in a fiber optic gyroscope according to the present invention.

[0054] Figure 7 This is a schematic diagram of the magneto-optical Faraday effect in existing technology.

[0055] Figure 8 The geometric relationship of the fiber optic ring in the radial magnetic field in the formula derivation of the distance optimization method between the double-layer magnetic shielding structures in the fiber optic gyroscope of the present invention;

[0056] Figure 9 The geometric relationship of the fiber optic ring in the axial magnetic field is shown in the formula derivation of the distance optimization method between the double-layer magnetic shielding structures in the fiber optic gyroscope of the present invention.

[0057] The annotations in the attached figures are explained as follows:

[0058] 1. Fiber optic ring; 2. Inner shielding structure; 21. Inner top cover; 22. Base; 3. Outer shielding structure; 31. Outer top cover; 32. Outer bottom cover; 4. Liner plate; 5. Screws. Detailed Implementation

[0059] To make the objectives, advantages, and features of this invention clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for optimizing the distance between double-layer magnetic shielding structures in a fiber optic gyroscope. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this invention and are not intended to limit the scope of protection of this invention.

[0060] like Figures 1-9 As shown, a method for optimizing the distance between double-layer magnetic shielding structures in a fiber optic gyroscope includes the following steps:

[0061] Step 1, obtain the optical fiber ring assembly to be applied to the optical fiber gyroscope, the optical fiber ring assembly includes an optical fiber ring 1, an outer shielding structure 3 (material is 1J79 high magnetic permeability alloy), an inner shielding structure 2 (material is 1J79 high magnetic permeability alloy), a backing plate 4 (material is hard aluminum alloy), and a screw 5 (material is zinc alloy); the inner shielding structure 2 includes an inner upper cover 22 and a base 21, the base 21 is provided with the optical fiber ring 1, and the optical fiber ring 1 is located in the base 21, and the bottom surface of the optical fiber ring 1 is connected with the bottom surface of the base 21; the outer shielding structure 3 includes an outer upper cover 32 and an outer lower cover 31, the outer upper cover 32 and the outer lower cover 31 form a containing cavity by being combined, the containing cavity is provided with the inner shielding structure 2, and both have a common center; the backing plate 4 is located in the inner circle of the inner shielding structure 2, the inner shielding structure 2 and the outer shielding structure 3 are fixed on the backing plate 4 through the screw 5, a three-dimensional model of the optical fiber ring assembly is built by simulation, and in the process of building the three-dimensional model, the distance between the outer shielding structure and the inner shielding structure is set as a preset distance d = 1 mm, and the three-dimensional model of the optical fiber ring assembly is obtained;

[0062] Step 2, obtain a finite element simulation software, import the three-dimensional model of the optical fiber ring assembly obtained in step 1 into the finite element simulation software, set the relative linear magnetic permeability of the optical fiber ring 1 as 1, the relative nonlinear magnetic permeability of the outer shielding structure 2 as the B-H curve parameters in the following table, the relative nonlinear magnetic permeability of the inner shielding structure 3 as the B-H curve parameters in the following table, the relative linear magnetic permeability of the backing plate 4 as 1, and the relative linear magnetic permeability of the screw 5 as 1, then, respectively, the three-dimensional model of the optical fiber ring assembly is subjected to a radial magnetic field strength and an axial magnetic field strength, both of which are 0.055 mT (taking the natural earth magnetic field as an example), twice simulation is performed, the average value of the magnetic field strength on the optical fiber ring is taken as the simulation result, the average value of the optical fiber ring radial magnetic field strength B R = 4.3 x 10 -7 mT and the average value of the optical fiber ring axial magnetic field strength B A = 1.14 x 10 -5 mT are obtained;

[0063] Table B-H curve

[0064] H (A / m) B (T) 0.8 0.1000 1.2 0.1750 1.8 0.2750 4.2 0.5334 8 0.5800 9 0.6000 16 0.6500 39.7 0.7561 399.8 0.8002 796.3 0.8013 1200 0.8013 1600 0.8013 2000 0.8013 2400 0.8013 2800 0.8013

[0065] Step 3, according to the average value of the optical fiber ring radial magnetic field strength B R and the average value of the optical fiber ring axial magnetic field strength B A obtained in step 2, the maximum output error of the optical fiber gyroscope in the radial magnetic field Ω R = 1.49 x 10 -5 ° / h and the maximum output error of the optical fiber gyroscope in the axial magnetic field Ω A = 3.16 x 10 -7 ° / h are calculated and obtained; the specific calculation method is as follows:

[0066] Step 3.1, according to the average value of the radial magnetic field strength of the fiber coil B obtained in step 2 R , the equivalent radius of the fiber coil and the average value of the radial magnetic field strength of the fiber coil B R Substitute the calculation formula to calculate and obtain the maximum output error of the fiber optic gyroscope in the radial magnetic field Ω R , the calculation formula is as follows:

[0067]

[0068] Where, Ω R is the maximum output error of the fiber optic gyroscope in the radial magnetic field, with unit of ° / h;

[0069] In this embodiment, R is the equivalent radius of the fiber coil, wherein R=(fiber coil inner diameter+fiber coil outer diameter) / 2, with unit of m;

[0070] △β is the linear birefringence of the fiber in the fiber coil, with unit of rad / m;

[0071] λ is the wavelength of the incident light of the fiber optic gyroscope, with unit of nm;

[0072] c is the propagation speed of the incident light of the fiber optic gyroscope, with unit of m / s;

[0073] V is the Verdet constant, with unit of rad / m / mT;

[0074] B R is the average value of the radial magnetic field strength of the fiber coil, with unit of mT;

[0075] t0 is the fiber torsion coefficient in the fiber coil, with unit of rad / m;

[0076] Step 3.2, according to the average value of the axial magnetic field strength of the fiber coil B obtained in step 2 A , the equivalent radius of the fiber coil and the average value of the axial magnetic field strength of the fiber coil B A Substitute the calculation formula to calculate and obtain the maximum output error of the fiber optic gyroscope in the axial magnetic field, the calculation formula is as follows:

[0077]

[0078] Where, Ω A is the maximum output error of the fiber optic gyroscope in the axial magnetic field, with unit of ° / h;

[0079] B A is the average value of the axial magnetic field strength of the fiber coil, with unit of mT;

[0080] D is the diameter of the optical fiber in the fiber ring, in units of pm.

[0081] Table 1 General physical parameters related to fiber-optic gyroscope

[0082] Parameter Value △β 2200 rad / m λ 1550 nm c 3 x 10 8 m / s V 6 x 10 -4 rad / m / mT [t0] 0.5 rad / m D 150 μm R 0.06m

[0083] The derivation process of formula (one) and formula (two) is as follows:

[0084] The basic principle of fiber-optic gyroscope is Sagnac effect, that is, the interference phase difference of two beams of light in the closed loop is used to sense the external angular rate, and the expression of the interference phase difference is as follows:

[0085]

[0086] Where, λ is the wavelength of the incident light of the fiber-optic gyroscope; c is the propagation speed of the incident light of the fiber-optic gyroscope; R is the equivalent radius of the fiber ring; L=N-2πR is the path length of the light wave propagating N turns in the fiber ring; Ω is the rotation angular rate.

[0087] The British scholar Michael Faraday first discovered and proposed the magneto-optical Faraday effect in experiments. When the light wave is transmitted in the optical fiber, if the optical fiber is in the magnetic field, the polarization plane of the light wave will rotate, as shown in Figure 7 .

[0088] The relationship formula of Faraday effect: the magnetic rotation angle θ of the polarization plane of the light wave is proportional to the path length L of the light wave in the fiber ring and the component B of the external magnetic field intensity in the direction of light propagation, that is: / /

[0089] θ=VB / / L (2)

[0090] Where, V is the Verdet constant, in units of (rad / m / mT).

[0091] The rotation of the polarization plane of the light wave means that the phase shift of the polarized light changes, thereby affecting the interference effect of the whole gyroscope, resulting in errors of the gyroscope.

[0092] Through the analysis of the polarization state change of the light wave in the fiber ring, it can be obtained that the phase difference Φ produced by the clockwise and counterclockwise light waves of the fiber ring after converging due to the influence of the magnetic field is:

[0093]

[0094] Where, z is the length of the differential fiber, in units of m; η + is the birefringence of the clockwise light wave fiber segment; η - ​ξ represents the birefringence of the fiber segment containing the counterclockwise light wave; Δβ represents the linear birefringence of the fiber itself, measured in rad / m; i Circular birefringence caused by the Faraday effect, unit: rad / m; t i represents the circular birefringence caused by fiber twisting, in rad / m; n represents the total number of i, the total number of infinitesimal elements.

[0095] The fiber optic ring is affected by a radially uniform magnetic field, such as Figure 8 As shown, B R Let N represent the intensity of the radial magnetic field, and let θ be the angle between it and the X-axis. Let z be the distance between any point A on the fiber optic ring and the starting point of the fiber optic ring. Let L be the total length of the fiber in the fiber optic ring, and let L = 2πNR, where N is the total number of turns of the fiber and R is the radius of the fiber optic ring.

[0096] For any point A on the fiber optic loop, the radial magnetic field B R At point A, the component of light propagating in the direction parallel to its path is B. R∥ The vertical component is B R⊥ According to the Faraday effect, the parallel component B of the radial magnetic field... R∥ This will induce the magneto-optical Faraday effect, causing magnetic field errors in the fiber optic gyroscope; while the radial magnetic field perpendicular component B R⊥ It will not cause the magneto-optical Faraday effect.

[0097] according to Figure 8 From the geometric relationships, the distribution of circular birefringence caused by the Faraday effect on the optical fiber is as follows:

[0098] ξ(z)=VB R / / =VB R sin(z / R+θ) (4)

[0099] Substituting equation (4) into equation (3) and simplifying, we can obtain the phase difference generated by the radial magnetic field affecting the fiber optic ring as follows:

[0100]

[0101] Where t(z) represents the distribution of circular birefringence caused by fiber twisting on the fiber, with units of rad / m.

[0102] Substituting equation (1) into equation (5), we can obtain the following angular velocity error caused by the radial magnetic field affecting the fiber optic ring:

[0103]

[0104] If the distribution of the fiber twist along the fiber length is uniform, i.e. t(z) is a constant, the integral part in equation (6) is zero, and the fiber ring angular velocity error is zero. If the distribution of the fiber twist along the fiber length is periodic and the period is the same as that of sin(z / R+θ), then There will be a maximum value, i.e. the angular velocity error of the fiber ring affected by the radial magnetic field is the largest.

[0105] When t(z) = t0sin(z / R), the maximum angular velocity error is:

[0106]

[0107] Convert the unit rad / s of (7) into ° / h, and the maximum output error of the fiber optic gyroscope Ω R is as follows:

[0108]

[0109] The fiber ring is affected by an axial uniform magnetic field as shown in Figure 9 , B A represents the strength of the axial magnetic field. Figure 9 The right side is a partial view of the fiber in the fiber ring at the splicing position. In the past research, the axial magnetic field error model of the fiber optic gyroscope is modeled with the spiral wound fiber, but with the development of the precise winding technology of the fiber optic gyroscope, the precise winding methods such as the eight-pole symmetric winding method and the sixteen-pole symmetric winding method are widely used in recent years. These precise symmetric winding methods adopt the parallel winding method, and only the bending at the fixed position of each fiber turn is performed to complete the splicing.

[0110] The angle between the fiber splicing bending part and the plane of the fiber ring is α, and for any point A on the fiber splicing bending part, the axial magnetic field B A has a component along the direction of light propagation parallel to B A / / , and a vertical component B A⊥ .

[0111] According to the geometric relationship in Figure 9 , the distribution of the circular birefringence caused by the Faraday effect on the fiber is:

[0112]

[0113] where p is the number of layers of the fiber ring; D(p) is a function of the number of layers of the fiber ring, representing the bending direction of the fiber splicing part on each layer, and the upward bending and downward bending are positive and negative respectively.

[0114] Substituting equation (8) into equation (3), the phase difference of the fiber ring affected by the axial magnetic field is as follows:

[0115]

[0116] where q is the number of turns of each layer of the fiber coil, and p·q=N, j represents the ordinal number of the turn-changing bending part of the fiber coil, L j and L j +s is the start and end positions of the turn-changing position in the fiber coil, and s is the length of the turn-changing part.

[0117] Substituting formula (1) into formula (9), the angular velocity error of the fiber coil caused by the axial magnetic field can be obtained as follows:

[0118]

[0119] If the fiber twist distribution in the fiber length direction is uniform, i.e., t(z) is a constant value. Because whether it is octupole, hexadecapole or other multipole winding, the total number of upward and downward layers of the fiber turn-changing part in the fiber coil is the same, the summation part in formula (25) is zero. If the fiber twist distribution t(z) in the fiber length direction is periodic distribution and the period is the same as that of D(p), formula (10) will have a maximum value, i.e., the angular velocity error of the fiber coil caused by the axial magnetic field is maximum.

[0120] When t(z)=t0D(p), the maximum angular velocity error is:

[0121]

[0122] Converting the unit rad / s of (11) into ° / h, the formula of the maximum output error Ω A of the fiber optic gyroscope is as follows:

[0123]

[0124] Step 4, judging whether the maximum output error Ω R of the fiber optic gyroscope in the radial magnetic field and the maximum output error Ω A of the fiber optic gyroscope in the axial magnetic field obtained in step 3 meet the technical index requirements of the fiber optic gyroscope (i.e., the bias stability of the fiber optic gyroscope is 1×10-3);

[0125] Ω R ≤1×10-3, and Ω A ≤1×10-3;

[0126] Step 5, outputting the corresponding distance between the outer shielding structure and the inner shielding structure corresponding to the Ω R and Ω A , and completing the optimization of the distance between the double-layer magnetic shielding structures of the fiber optic gyroscope.

[0127] In the description of the application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, can be fixedly connected, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium; can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0128] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A method for optimizing the distance between double-layer magnetic shielding structures in a fiber-optic gyroscope, characterized in that, The method comprises the following steps: Step 1, obtaining a fiber ring assembly to be applied to a fiber optic gyroscope, the fiber ring assembly comprising a fiber ring (1), an outer shielding structure (3) and an inner shielding structure (2), a three-dimensional model of the fiber ring assembly is built by simulation, and during the building of the three-dimensional model, the distance between the outer shielding structure (3) and the inner shielding structure (2) is set as a preset distance d, and a three-dimensional model of the fiber ring assembly is obtained; Step 2, obtaining a finite element simulation software, importing the three-dimensional model of the fiber coil assembly obtained in step 1 into the finite element simulation software, setting the magnetic property attributes of the materials of all components in the fiber coil assembly in the finite element simulation software, and then respectively applying a preset magnetic field strength radial magnetic field and an axial magnetic field to the three-dimensional model of the fiber coil assembly according to the magnetic field environment applied by the fiber optic gyroscope to be applied, and simulating to obtain the average value B R of the radial magnetic field strength of the fiber coil A and the average value B A of the axial magnetic field strength of the fiber coil. Step 3, the radial magnetic field strength average value B of the optical fiber ring obtained according to step 2 R and the axial magnetic field strength average value B of the optical fiber ring A and the wavelength and propagation speed of the incident light of the fiber optic gyroscope, the maximum output error Ω of the fiber optic gyroscope in the radial magnetic field is calculated R , and the maximum output error Ω of the fiber optic gyroscope in the axial magnetic field A ; Step 4, judging whether the maximum output error Ω of the fiber optic gyroscope in the radial magnetic field obtained in step 3 and the maximum output error Ω of the fiber optic gyroscope in the axial magnetic field satisfy the technical index requirements of the fiber optic gyroscope R and the maximum output error Ω of the fiber optic gyroscope in the axial magnetic field A ​ If Ω R ≤ the fiber-optic gyroscope's zero-bias stability, and Ω A ≤ the fiber-optic gyroscope's zero-bias stability, then step 5 is performed. If at least one of Ω R and Ω A is greater than the bias stability of the fiber optic gyroscope, return to step 1 and increase the spacing between the outer shield and the inner shield to d+Δd until both Ω R and Ω A are less than or equal to the bias stability of the fiber optic gyroscope. Step 5, output the Ω R And Ω A Corresponding to the spacing between the outer shielding structure and the inner shielding structure, the distance between the double-layer magnetic shielding structures of the fiber optic gyroscope is optimized.

2. The method according to claim 1, wherein the distance between the two layers of the magnetic shielding structure is optimized. 0.25mm≤d≤1.5mm, 0.05mm≤Δd≤0.1mm.

3. The method according to claim 1, wherein the distance between the two layers of the magnetic shielding structure is optimized. Step 3 is specifically: Step 3.1, the average value of the radial magnetic field strength B of the optical fiber loop obtained in step 2 R , the maximum output error Ω of the fiber optic gyroscope in the radial magnetic field is calculated and obtained R , the calculation formula is as follows: wherein Ω R is the maximum output error of the fiber-optic gyroscope in a radial magnetic field, in ° / h; R is the equivalent radius of the fiber ring, wherein R=(fiber ring inner diameter+fiber ring outer diameter) / 2, unit: m; Δβ is the linear birefringence of the fiber in the fiber ring, unit: rad / m; λ is the wavelength of the incident light of the fiber optic gyroscope, unit: nm; c is the propagation speed of the incident light of the fiber optic gyroscope, unit: m / s; V is the Verdet constant, unit: rad / m / mT; B R B is the average value of the radial magnetic field strength of the fiber loop in mT; t0 is the torsion coefficient of the fiber in the fiber ring, unit: rad / m; Step 3.2 The average value of the axial magnetic field strength B of the fiber coil is calculated according to the fiber coil obtained in step 2 A The maximum output error of the fiber optic gyroscope in the axial magnetic field is calculated and obtained.

4. The method according to claim 3, wherein the distance between the two layers of the magnetic shielding structure is optimized. Step 3.2 is specifically: The average value of the axial magnetic field strength B of the fiber coil obtained according to step 2 A The maximum output error of the fiber optic gyroscope in the axial magnetic field is calculated and obtained, and the calculation formula is as follows: wherein Ω A is the maximum output error of the fiber-optic gyroscope in an axial magnetic field, in ° / h; B A B is the average axial magnetic field strength of the fiber loop, in mT. D is the diameter of the fiber in the fiber ring, unit: μm.

5. The method of claim 1, wherein the distance between the two layers of the magnetic shielding structure is optimized. The magnetic property attributes in step 2 include relative linear permeability and relative nonlinear permeability.

6. The method of claim 1, wherein the distance between the two layers of the magnetic shielding structure is optimized. The fiber ring assembly in step 1 comprises a fiber ring (1), an inner shielding structure (2), a backing plate (4), an outer shielding structure (3) and a screw (5); The inner shielding structure (2) comprises an inner upper cover (22) and a base (21), the base (21) is provided with the fiber ring (1), and the bottom surface of the fiber ring (1) is connected with the bottom surface of the inner shielding structure (2); The backing plate (4) is located in the inner circle of the inner shielding structure (2), and the inner shielding structure (2) and the outer shielding structure (3) are fixed on the backing plate (4) through the screw (5); The outer shielding structure (3) comprises an outer upper cover (32) and an outer lower cover (31), the outer upper cover (32) and the outer lower cover (31) form a containing cavity, the inner shielding structure (2) is arranged in the containing cavity, and the two have a common center.

7. The method of claim 6, wherein the distance between the two layers of the magnetic shielding structure is optimized. In step 2, the permeability input to the finite element simulation software comprises the relative linear permeability of the fiber ring (1), the backing plate (4) and the screw (5), and the relative nonlinear permeability of the inner shielding structure (2) and the outer shielding structure (3).

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