Method for improving zero-bias stability of three-axis integrated fiber-optic gyroscope

Abstract

The invention relates to a zero-bias stability improving method of a three-axis integrated fiber-optic gyroscope. The method comprises the following steps: step 1, designing a three-point trapezoidal net edge boss structural body; step 2, based on the three-point trapezoidal net edge boss structural body designed in the step 1, reversely positioning and mounting an interferometer on a trapezoidal net edge boss; 3, broadband sweep frequency vibration aging treatment is conducted, and structure and installation residual stress is removed; and 4, carrying out local destressing treatment to improve the zero-bias stability of the three-axis integrated fiber-optic gyroscope. According to the method, the influence of temperature-stress errors on the stability of the gyroscope can be inhibited.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic gyroscope technology and relates to a method for improving the zero-bias stability of a fiber optic gyroscope, particularly a method for improving the zero-bias stability of a three-axis integrated fiber optic gyroscope. Background Technology

[0002] Fiber optic gyroscopes utilize an interferometer as the sensing element to measure angular rate based on the Sagnac effect. The interferometer, as the sensing element directly sensing the Sagnac phase shift in the gyroscope, is also highly sensitive to various related physical quantities, such as temperature and stress. The non-reciprocal phase difference generated by the interferometer due to temperature or stress changes is called Shupe error. Shupe error is the main error source of fiber optic gyroscopes and directly affects the gyroscope's zero-bias stability.

[0003] A three-axis integrated fiber optic gyroscope typically integrates three interferometers inward into a single compact structure. However, the interferometers, composed of fiber optic loops and Y-waveguides, are susceptible to the combined effects of thermal fields, mechanical stress, and vibrations within a limited space. Specifically:

[0004] First, there is the superposition of temperature fields. Insufficient spacing between the rings and Y-waveguides of adjacent interferometers leads to intersecting heat conduction paths and an asymmetric thermal gradient. Second, there is stress sensitivity. In traditional processes, the bonded ends of the rings are exposed, with the axial direction at the farthest point. When subjected to vibration, significant local stress is generated at the bonded joints, causing dynamic fluctuations in the fiber refractive index. Third, there is Shupe error degradation. Dynamic changes in temperature and stress cause fluctuations in the fiber refractive index within the interferometer, leading to increased phase noise and degrading zero-bias stability to 0.025° / h.

[0005] Existing designs struggle to achieve temperature field decoupling and stress equalization within a compact space, and the exposed bonding end face of the ring will further exacerbate gyroscope stability errors when subjected to vibration. Therefore, how to achieve temperature field decoupling and stress equalization within a compact space and reduce gyroscope stability errors is a pressing technical challenge in this field.

[0006] A search revealed no publicly available literature of the same or similar prior art as this invention. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for improving the zero-bias stability of a three-axis integrated fiber optic gyroscope, thereby suppressing the influence of temperature-stress error on the stability of the gyroscope.

[0008] The present invention solves its practical problem by adopting the following technical solution:

[0009] A method for improving the zero-bias stability of a triaxial integrated fiber optic gyroscope includes the following steps:

[0010] Step 1: Design a three-point trapezoidal mesh boss structure;

[0011] Step 2: Based on the three-point trapezoidal mesh protrusion structure designed in Step 1, the interferometer is reverse-positioned and installed on the trapezoidal mesh protrusion.

[0012] Step 3: Perform broadband frequency sweep vibration aging treatment to remove residual stress in the structure and installation.

[0013] Step 4: Perform local stress relief treatment to improve the zero-bias stability of the triaxial integrated fiber optic gyroscope.

[0014] Furthermore, the three-point trapezoidal mesh protrusion structure in step 1 includes: three trapezoidal mesh protrusions designed on the end faces of the structure in the X-axis, Y-axis and Z-axis directions respectively; the trapezoidal mesh protrusions are flat circular cones; the three trapezoidal mesh protrusions are evenly distributed at 120° on the structure, and three interferometers are installed on the three trapezoidal mesh protrusions respectively.

[0015] Furthermore, the specific method for step 2 is as follows:

[0016] The three interferometers are installed in axially symmetrical and opposite positions. The interferometers are reversed so that the Y-waveguide end faces inside the three interferometers extend outward into space along the X, Y, and Z axes respectively and are orthogonally distributed. The inner ring bonding end face of the interferometer faces the three-point trapezoidal mesh protrusion structure and is closest to the corresponding trapezoidal mesh protrusion.

[0017] Furthermore, the specific method for step 3 is as follows:

[0018] After installing three interferometers on the three-point trapezoidal mesh protrusion structure, the whole structure is subjected to broadband sweep vibration aging treatment of 10-2000Hz, 10g, 60min.

[0019] Furthermore, the specific method for step 4 is as follows:

[0020] To address the issues of distortion and large jumps in the zero-bias stability of a single-axis interferometer, a stress-relief treatment was implemented using local (2-20) μm amplitude variation, (20-60) kHz frequency variation, and (3-15) min multi-segment ultrasonic vibration, which precisely improved the zero-bias stability of the triaxial integrated fiber optic gyroscope.

[0021] Advantages and beneficial effects of the present invention:

[0022] 1. This invention proposes a method to improve the zero-bias stability of a triaxial integrated fiber optic gyroscope. By using an outward orthogonal three-point suspended layout for thermal-stress isolation and a scheme of overall vibration aging plus local ultrasonic vibration stress relief, the influence of temperature and stress on the stability of the gyroscope is significantly suppressed. Actual measurement data shows that after taking the measures, the zero-bias stability of the gyroscope is improved from 0.025° / h to 0.008° / h (an improvement of 68%).

[0023] 2. This invention has strong versatility and high engineering application value. It has been adapted and verified in sizes of 40, 75, and 200 mm, and can be widely applied in (40-200) mm three-axis integrated fiber optic gyroscopes, providing an innovative solution for compact, high-precision inertial navigation systems.

[0024] 3. This invention employs an outward-oriented orthogonal three-point supported suspended positioning interferometer layout. After layout, the ring bonding end faces the mounting structure, and the Y-waveguide is located at the outermost end of the three-axis structure. The mounting interferometer structure adopts, but is not limited to, a three-point trapezoidal mesh protrusion structure design, with the three mesh protrusions evenly distributed at 120°. Furthermore, the three-axis integrated fiber optic gyroscope undergoes overall vibration aging treatment at (10-2000) Hz, 10g, and 60min, but is not limited to. For individual issues such as stability distortion or large jumps in a certain axis of the three-axis integrated fiber optic gyroscope, a variable frequency and amplitude multi-segment ultrasonic vibration stress relief treatment scheme is adopted, thereby suppressing the influence of temperature and stress on the stability of the gyroscope. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the trapezoidal mesh protrusion structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the spatial layout structure of the outward orthogonal three-point suspended positioning interferometer of the present invention;

[0027] Figure 3(a) is a graph of the measured data before the improvement of the present invention;

[0028] Figure 3(b) is a graph of the measured data after the improvement of the present invention;

[0029] Explanation of reference numerals in the attached figures:

[0030] 1-Three-point trapezoidal mesh protrusion structure; 2-Interferometer; 3-Y-waveguide end face; 4-Trapezoidal mesh protrusion; 5-Ring bonding end face; Detailed Implementation

[0031] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings:

[0032] A method for improving the zero-bias stability of a triaxial integrated fiber optic gyroscope includes the following steps:

[0033] Step 1: Design a three-point trapezoidal mesh boss structure to reduce heat conduction and increase heat dissipation area;

[0034] The three-point trapezoidal mesh protrusion structure in step 1 includes: three trapezoidal mesh protrusions designed on the end faces of the structure in the X-axis, Y-axis, and Z-axis directions respectively; such as Figure 1As shown, the trapezoidal mesh protrusion is a flat circular cone; the three trapezoidal mesh protrusions are evenly distributed at 120° on the structure, blocking the heat conduction path, increasing the heat dissipation area, and reducing the cross-influence of temperature; three interferometers are installed on the three trapezoidal mesh protrusions respectively.

[0035] Step 2: Based on the three-point trapezoidal mesh protrusion structure designed in Step 1, the interferometer is reverse-positioned and installed on the trapezoidal mesh protrusion, which effectively reduces thermal superposition and crosstalk between interferometers and improves the stress field of the interferometer.

[0036] The specific method for step 2 is as follows:

[0037] The three interferometers are installed in axially symmetrical and opposite positions. The interferometers are reversed so that the Y-waveguide end faces inside the three interferometers extend outward into space along the X, Y, and Z axes respectively and are orthogonally distributed. The inner ring bonding end face of the interferometer faces the mesh protrusion structure and is closest to the corresponding trapezoidal mesh protrusion.

[0038] Step 3: Perform broadband frequency sweep vibration aging treatment to remove residual stress in the structure and installation.

[0039] The specific method for step 3 is as follows:

[0040] After installing three interferometers on the three-point trapezoidal mesh protrusion structure, the whole structure is subjected to broadband sweep vibration aging treatment of 10-2000Hz, 10g, 60min.

[0041] Step 4: Perform local stress relief treatment to improve the zero-bias stability of the triaxial integrated fiber optic gyroscope.

[0042] The specific method for step 4 is as follows:

[0043] To address the issues of distortion and large jumps in the zero-bias stability of a single-axis interferometer, a stress-relief treatment was implemented using local (2-20) μm amplitude variation, (20-60) kHz frequency variation, and (3-15) min multi-segment ultrasonic vibration, which precisely improved the zero-bias stability of the triaxial integrated fiber optic gyroscope.

[0044] The specific implementation method of the present invention is as follows:

[0045] Step 1: Design a new three-point trapezoidal mesh protrusion structure on the structure on which the interferometer is installed. The three mesh protrusions are evenly distributed at 120° and are then machined into shape.

[0046] Step 2: Install the three interferometers equipped with rings and Y-waveguides outwardly and orthogonally onto the X, Y, and Z axes of the three-point mesh prism structure, connect the optical path and circuitry, and form a three-axis integrated gyroscope.

[0047] Step 3: Set up a precision temperature-measuring platinum resistance thermometer and an FBG strain sensor on the interferometer;

[0048] Step 4: After installing three interferometers on the three-point mesh prism protrusion structure, perform broadband sweep vibration aging treatment on the whole structure at (10-2000) Hz, 10g, and 60min.

[0049] Step 5: For interferometers exhibiting distortion or large jumps in single-axis zero-bias stability, connect the ultrasonic vibration probe securely to the interferometer. Use a low frequency of (20-30) kHz, a large amplitude of (10-20) μm, a power of (100-150) W, and vibrate for (2-8) min. Then use a high frequency of (30-60) kHz, a small amplitude of (2-7) μm, a power of (30-75) W, and vibrate for (2-8) min. The total duration should not exceed 15 minutes.

[0050] The innovation of this invention lies in:

[0051] (1) Innovative design of three-point trapezoidal mesh protrusion structure, the three-point trapezoidal mesh protrusion is evenly distributed at 120° on the structure, which improves the cross influence of temperature field;

[0052] (2) Install the three interferometers in axially symmetrical, opposite positions. Reverse the interferometers so that the Y-waveguides within the three interferometers extend outward along the X, Y, and Z axes respectively, and are orthogonally distributed. The bonding end face of the inner ring of the interferometer faces the three-point trapezoidal mesh protrusion structure, and is closest to the corresponding trapezoidal mesh protrusion. See Figure 2 After the interferometers are installed in a three-point outward orthogonal distribution, the heat conduction path extends outward along the supporting bosses, dissipating 67.3% of the conducted heat at the grid edge. With outward installation, the most sensitive Y-waveguide ends of the three interferometers are located at the farthest points of their respective axes, away from heat sources within the structure, minimizing heat radiation within the confined space and effectively reducing thermal superposition and crosstalk between the interferometers. With the outward layout, the bonding end face of the ring assembly is located inside the structural platform but does not contact it, remaining in a suspended structure. The heat conduction path of the end face is U-shaped and located at the farthest point; its position is at the orthogonal apex of the structure, at the position of minimum lever arm within the confined space. Under dynamic excitations such as vibration, the stress at the bonding position of the ring assembly is minimal, which is beneficial for maintaining the misalignment angle and zero-bias stability.

[0053] (3) After installing three interferometers on the three-point mesh protrusion structure, the whole structure was subjected to (10-2000)Hz, 10g, 60min broadband sweep frequency vibration aging treatment to remove residual stress, stabilize installation stress, reduce residual stress on the ring bonding end face to below 10MPa, attenuation of 28.6%, and test showed that the standard deviation of gyroscope zero bias fluctuation decreased by 35.3%.

[0054] (4) To address the problems of distortion and large jump in the zero-bias stability of a single-axis interferometer, a stress relief treatment scheme of local (2-20) μm amplitude variation, (20-60) kHz frequency variation, and (3-15) min multi-segment ultrasonic vibration is adopted. Local ultrasonic vibration can effectively eliminate or reduce the distortion or large jump amplitude by 65%.

[0055] The invention will be further illustrated below with specific examples:

[0056] Experimental testing and verification:

[0057] Step 1: Temperature change test. Test the changes in zero-bias stability of each axis of the gyroscope before and after the improvement of the three-point orthogonal installation in reverse at a temperature change rate of (0.1-5)℃.

[0058] Step 2: Strain test. The stress change at the bonding end of the ring is tested before and after vibration aging and local ultrasonic vibration, and the zero-bias stability of each axis of the gyroscope is tested.

[0059] Step 3: Assemble the newly designed gyroscope and inertial navigation system together to form a three-axis integrated fiber optic gyroscope inertial navigation system. Perform system-level gyroscope zero-bias stability test according to the actual engineering application environment. The measured data is 0.008° / h.

[0060] The working principle of the present invention is:

[0061] This invention primarily aims to reduce the non-reciprocity error of an interferometer integrated into a single compact structure due to temperature or stress variations, thereby improving the zero-bias stability of the fiber optic gyroscope. It improves the heat conduction path within a limited space for the interferometer, which consists of fiber optic loops and a Y-waveguide, in a three-axis integrated fiber optic gyroscope by increasing the heat dissipation area and reducing the thermal impact of temperature changes on the interferometer; it reduces the lever arm of the bonding surface of the inner loop of the interferometer, improving vibration resistance, and employs overall vibration aging treatment to stabilize stress; and it utilizes local ultrasonic stress relief treatment to address stress instability in a single interferometer.

[0062] Therefore, this invention proposes a method to improve the zero-bias stability of a triaxial integrated fiber optic gyroscope. By using an outward orthogonal three-point suspended layout for thermal-stress isolation and a scheme of overall vibration aging plus local ultrasonic vibration stress relief, the influence of temperature-stress on the stability of the gyroscope is significantly suppressed. The measured data shows that after taking the measures, the zero-bias stability of the gyroscope is improved from 0.025° / h to 0.008° / h (an improvement of 68%), as shown in Figures 3(a) and 3(b).

[0063] A method for improving the zero-bias stability of a three-axis integrated fiber optic gyroscope involves an outward-oriented orthogonal three-point support suspended positioning interferometer layout, with the ring bonding end face facing the mounting structure after layout, and the Y-waveguide located at the outermost end of the three-axis structure.

[0064] The structure for mounting the interferometer adopts, but is not limited to, a three-point trapezoidal grid protrusion structure design, with the three grid protrusions evenly distributed at 120°.

[0065] The triaxial integrated fiber optic gyroscope is subjected to overall vibration aging treatment at (10-2000) Hz, 10g, and 60min, but not limited to.

[0066] For individual problems such as stability distortion or large jumps in a single axis of a three-axis integrated fiber optic gyroscope, a stress relief solution using variable frequency and amplitude multi-segment ultrasonic vibration is adopted.

[0067] It should be emphasized that the embodiments described in this invention are illustrative rather than limiting. Therefore, this invention includes, but is not limited to, the embodiments described in the specific implementation. Any other implementations derived by those skilled in the art based on the technical solutions of this invention are also within the scope of protection of this invention.

Claims

1. A method for improving the zero-bias stability of a triaxial integrated fiber optic gyroscope, characterized in that: Includes the following steps: Step 1: Design a three-point trapezoidal mesh boss structure; Step 2: Based on the three-point trapezoidal mesh protrusion structure designed in Step 1, the interferometer is reverse-positioned and installed on the trapezoidal mesh protrusion. Step 3: Perform broadband frequency sweep vibration aging treatment to remove residual stress in the structure and installation. Step 4: Perform local stress relief treatment to improve the zero-bias stability of the triaxial integrated fiber optic gyroscope.

2. The method for improving the zero-bias stability of a triaxial integrated fiber optic gyroscope according to claim 1, characterized in that: The three-point trapezoidal mesh protrusion structure in step 1 includes: three trapezoidal mesh protrusions designed on the end faces of the structure in the X-axis, Y-axis and Z-axis directions respectively; the trapezoidal mesh protrusions are flat circular cones; the three trapezoidal mesh protrusions are evenly distributed at 120° on the structure, and three interferometers are installed on the three trapezoidal mesh protrusions respectively.

3. The method for improving the zero-bias stability of a triaxial integrated fiber optic gyroscope according to claim 1, characterized in that: The specific method for step 2 is as follows: The three interferometers are installed in axially symmetrical and opposite positions. The interferometers are reversed so that the Y-waveguide end faces inside the three interferometers extend outward into space along the X, Y, and Z axes respectively and are orthogonally distributed. The inner ring bonding end face of the interferometer faces the three-point trapezoidal mesh protrusion structure and is closest to the corresponding trapezoidal mesh protrusion.

4. The method for improving the zero-bias stability of a triaxial integrated fiber optic gyroscope according to claim 1, characterized in that: The specific method for step 3 is as follows: After installing three interferometers on the three-point trapezoidal mesh protrusion structure, the whole structure was subjected to broadband sweep frequency vibration aging treatment at 10-2000Hz, 10g, and 60min.

5. The method for improving the zero-bias stability of a triaxial integrated fiber optic gyroscope according to claim 1, characterized in that: The specific method for step 4 is as follows: To address the issues of distortion and large jumps in the zero-bias stability of a single-axis interferometer, a stress-relief treatment was implemented using local (2-20) μm amplitude variation, (20-60) kHz frequency variation, and (3-15) min multi-segment ultrasonic vibration, which precisely improved the zero-bias stability of the triaxial integrated fiber optic gyroscope.

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