A miniaturized three-axis integrated fiber optic gyroscope

Abstract

The present invention discloses a micro-miniature three-axis integrated fiber optic gyroscope, which includes a housing, an optical path component and a circuit component. The above components are fixed in the housing through a heat-conducting mounting seat; the optical path component includes a light source, an X-axis fiber optic ring component, a Y-axis fiber optic ring component and a Z-axis fiber optic ring component, and the circuit component includes a modulation / demodulation SOC microcircuit and a light source drive SOC microcircuit; with the design concept of functional modularization, the modulation / demodulation circuit of the fiber optic gyroscope, the information processing with FPGA software, the communication interface circuit and the power management circuit are encapsulated and integrated into a modulation / demodulation SOC microcircuit, and the light source drive circuit and the temperature control circuit are encapsulated into a light source drive SOC microcircuit, realizing all functions such as light source drive, fiber optic gyroscope modulation / demodulation, temperature acquisition, error compensation, and external data communication. Without reducing the product performance, the working temperature range is broadened, well meeting the application requirements of "light and small" weapon systems.

Description

Technical Field

[0001] The present invention relates to a fiber optic gyroscope, and particularly to a micro-miniature three-axis integrated fiber optic gyroscope. Background Art

[0002] With the continuous deepening of globalization and the increasingly fierce competition among major powers, the security environment faced by countries has become more complex and intricate. As important components of the national system's combat power, new types of weapon systems such as the new generation of "intelligent" medium- and long-range air defense and anti-missile missiles, the new generation of "smart" precision-guided munitions, and long-endurance "reconnaissance-strike integrated" unmanned vehicles have more and more internal payloads, leaving extremely limited space for the inertial measurement and navigation system. Therefore, more stringent volume and weight requirements are imposed on the inertial measurement and navigation system while ensuring measurement accuracy. The miniaturization of the gyroscope is the basis and prerequisite for the lightweight and miniaturization of the inertial system.

[0003] Currently, the common gyroscopes applied to various tactical weapon systems mainly include liquid floated gyroscopes, flexible gyroscopes, ring laser gyroscopes, fiber optic gyroscopes, and microelectromechanical system (MEMS) gyroscopes, etc. Liquid floated gyroscopes and flexible gyroscopes have complex manufacturing processes, large volumes, and low accuracies, and have gradually withdrawn from the historical stage; ring laser gyroscopes have discrete optical devices inside, with complex implementation processes, difficulties in miniaturization, and require high-voltage startup, making applications inconvenient; although MEMS gyroscopes have the natural advantage of small volume, due to the domestic technical level, there is still a large gap between their measurement accuracy, stability, and reliability and the current requirements. As a new type of all-solid-state gyroscope, fiber optic gyroscopes have outstanding advantages such as all-solid state, digitalization, strong environmental adaptability, and simple application, and are increasingly widely used. However, with the continuous improvement of the requirements of weapon systems, existing fiber optic gyroscopes have gradually been unable to meet the "lightweight and miniaturized" application requirements of the new generation of weapon systems.

[0004] The technical disadvantages of existing fiber optic gyroscopes are mainly manifested in the following aspects:

[0005] 1. Some optical devices (light sources, couplers, detectors) of existing three-axis fiber optic gyroscopes borrow fiber optic communication products, and their input and output pigtails are single-mode fibers with a 125-μm cladding diameter, which are incompatible with the polarization-maintaining fibers with an 80-μm cladding diameter used in the fiber optic ring. This problem was originally solved by coupling fibers with different cladding diameters at the input and output ends of the Y waveguide, that is, coupling 125-μm polarization-maintaining fibers at the input and 80-μm polarization-maintaining fibers at the output to respectively match the different optical paths at the front and rear ends, but there is a problem of mode field mismatch;

[0006] 2. The multi-layer printed circuit boards used in the circuit part have large volumes and weights, and cannot meet the strict requirements of lightweight and miniaturized weapon systems for the volume and weight of internal components. Moreover, since there are corresponding software for both the information processing circuit and the interface circuit, the project management workload is greatly increased;

[0007] 3. The operating temperature range of existing three-axis fiber optic gyroscopes is -40°C to +60°C. However, with the inevitable trend of increasing the range of future tactical weapons, this operating temperature range may not be able to adapt to future potential operating environments.

[0008] 4. Existing three-axis fiber optic gyroscopes suppress shot noise and various polarization errors by ensuring the minimum reciprocal structure of the optical path. There are basically no effective measures to suppress the relative intensity noise of the light source. With the gradual increase in the power of the light source, the relative intensity noise of the light source has limited the measurement accuracy of fiber optic gyroscopes to a certain extent. Summary of the Invention

[0009] The purpose of the present invention is to provide a micro-miniature three-axis integrated fiber optic gyroscope with reasonable design, which solves the problems of large volume, large weight, poor stability, and low flexibility of the flexible exoskeleton micro-miniature three-axis integrated fiber optic gyroscope, and realizes the miniaturization and lightweight of the micro-miniature three-axis integrated fiber optic gyroscope.

[0010] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0011] The present invention is a micro-miniature three-axis integrated fiber optic gyroscope, which is characterized in that it includes a housing, an optical path component and a circuit component. A heat-conducting mounting seat for fixing the optical path component and the circuit component is provided inside the housing.

[0012] The optical path component includes a light source, a coupler, an X-axis fiber loop component, a Y-axis fiber loop component and a Z-axis fiber loop component. The X-axis fiber loop component, the Y-axis fiber loop component and the Z-axis fiber loop component are sequentially connected by a fiber loop, a waveguide and a coupling module. The coupling module is connected to the light source through the coupler. The fiber loops on different fiber loop components are separately installed at different positions on the heat-conducting mounting seat.

[0013] The circuit component includes a modulation and demodulation SOC microcircuit corresponding to each axis inside the gyroscope and a light source drive SOC microcircuit for controlling the light source. The modulation and demodulation SOC microcircuit is provided with an information processing module with an embedded FPGA chip. The information processing modules between different modulation and demodulation SOC microcircuits are communicatively connected and also connected to the waveguide of the corresponding fiber loop component. An optical sensing module for realizing optical signal connection with the coupling module of the fiber loop component is also provided on the information processing module; the light source drive SOC microcircuit is encapsulated by a light source drive circuit for controlling the light source and a temperature control circuit for monitoring the temperature of the light source and inside the housing. The temperature control circuit is connected to the light source drive circuit.

[0014] Preferably, a heat source placement area away from the fiber loop is provided inside the housing, and the light source and the circuit component are arranged in the heat source placement area.

[0015] Preferably, the light source is directly mounted on the heat-conducting mounting seat, and a heat-conducting silicone grease layer is coated on the light source contact surface connected to the heat-conducting mounting seat.

[0016] Preferably, the circuit component is mounted on the heat-conducting mounting base through heat-conducting struts.

[0017] Preferably, a ceramic fiber paper with a relatively low thermal conductivity is provided between the above-mentioned optical fiber loop component and the heat-conducting mounting base.

[0018] Preferably, a black magneto-anodic treatment layer is provided on the surfaces of both the optical fiber loop and the heat-conducting mounting base.

[0019] Preferably, a fiber coiling board for winding the optical fiber is fixed on the heat-conducting mounting base.

[0020] Preferably, the light source adopts an SLD light source, the optical sensing module adopts a photodetector, the light source driving circuit adopts a constant current source driving circuit, and the temperature control circuit adopts an intelligent temperature control circuit.

[0021] Preferably, the length of the optical fiber loop is 220 mm, and the diameter of the optical fiber loop is 32 mm; the optical fiber loop adopts a skeleton-free optical fiber loop based on 80-um polarization-maintaining optical fiber; the coupler adopts a 1×3 coupler, and the coupling module adopts a 2×2 coupler.

[0022] Compared with the prior art, with the design concept of functional modularization and aiming at high precision, small size and low power consumption, the modulation and demodulation circuit of the fiber optic gyroscope, the information processing module with FPGA software, the communication interface circuit, the power management circuit and other systems are encapsulated and integrated into a modulation and demodulation SOC microcircuit, and the light source driving circuit and the temperature control circuit are encapsulated into a light source driving SOC microcircuit, which cooperates with the FPGA software and the optical sensing module to realize all functions such as light source driving, fiber optic gyroscope modulation and demodulation, temperature acquisition, error compensation, external data communication, etc., and finally realizes the measurement of the carrier's three-axis angular velocity information and external output. Compared with the prior art, without reducing the product performance, the volume and weight of the present invention are reduced by more than 60% compared with the existing products, and the working temperature range is broadened, which can well meet the application requirements of "light and small" weapon systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the present invention, and constitute a part of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0024] Figure 1 is the principle block diagram of the micro-miniature three-axis integrated fiber optic gyroscope described in the present invention;

[0025] Figure 2 is the three-dimensional structure diagram of the micro-miniature three-axis integrated fiber optic gyroscope described in the present invention;

[0026] Figure 3 This is the optical path diagram of the micro-miniature three-axis integrated fiber optic gyroscope according to the present invention;

[0027] Figure 4 This is the principle block diagram of the modulation and demodulation SOC microcircuit;

[0028] Figure 5 This is the principle block diagram of the constant current source drive circuit;

[0029] Figure 6 This is the schematic diagram of the relative intensity noise cancellation principle;

[0030] Figure 7 This is the general software principle block diagram of the modulation and demodulation circuit;

[0031] Figure 8 This is the schematic diagram of the principle of the software interface;

[0032] Figure 9 This is the connection relationship of the modulation and demodulation circuit;

[0033] Figure 10 This is the principle block diagram of the intelligent temperature control of the light source;

[0034] Reference numerals:

[0035] 1 - Heat-conducting mounting base, 2 - X-axis fiber optic ring assembly, 3 - Y-axis fiber optic ring assembly, 4 - Z-axis fiber optic ring assembly, 5 - Fiber optic winding board, 6 - Light source, 7 - Information processing module, 8 - Heat-conducting support pillar. Detailed implementation manners

[0036] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] Refer to Figure 1-3 , the present invention provides a micro-miniature three-axis integrated fiber optic gyroscope, including a housing, an optical path component and a circuit component. A heat-conducting mounting base 1 for fixing the optical path component and the circuit component is provided inside the housing;

[0038] The optical path component includes a light source 6, a coupler, an X-axis fiber optic ring assembly 2, a Y-axis fiber optic ring assembly 3 and a Z-axis fiber optic ring assembly 4. The X-axis fiber optic ring assembly 2, the Y-axis fiber optic ring assembly 3 and the Z-axis fiber optic ring assembly 4 are all sequentially connected by a fiber optic ring, a waveguide and a coupling module. The coupling module is connected to the light source through the coupler. The fiber optic rings on different fiber optic ring assemblies are separately installed at different positions on the heat-conducting mounting base. A fiber optic winding board 5 for winding the fiber optic is fixed on the heat-conducting mounting base 1;

[0039] The described circuit components include a modulation and demodulation SOC microcircuit corresponding to each axis inside the gyroscope and a light source driving SOC microcircuit for controlling the light source. The modulation and demodulation SOC microcircuit has an information processing module with an embedded FPGA chip. The information processing modules between different modulation and demodulation SOC microcircuits are communicatively connected and are also connected to the waveguide of the corresponding fiber optic ring assembly. An optical sensing module for realizing optical signal connection with the coupling module of the fiber optic ring assembly is also provided on the information processing module 7; The light source driving SOC microcircuit is encapsulated by a light source driving circuit for controlling the light source and a temperature control circuit for monitoring the temperature of the light source and inside the housing. The temperature control circuit is connected to the light source driving circuit;

[0040] During operation, the light source is transported to the fiber optic ring through the coupler, coupling module, and waveguide; The optical sensing module obtains the optical signal from the coupling module, transports it to the modulation and demodulation SOC circuit of the fiber optic gyroscope, and after being processed by the modulation and demodulation SOC circuit, it is transported to the information processing module. At the same time, the temperature condition of the SLD light source is obtained through the temperature control circuit and fed back to the information processing module, and the information processing module controls the operation of the light source driving circuit.

[0041] A heat source placement area away from the fiber optic ring is provided inside the housing, and the light source and circuit components are arranged in the heat source placement area. The light source is directly installed on a heat-conducting mounting seat, and a heat-conducting silicone grease layer is coated on the light source contact surface connected to the heat-conducting mounting seat 1. The circuit components are installed on the heat-conducting mounting seat 1 through heat-conducting struts 8.

[0042] A ceramic fiber paper with a lower thermal conductivity is provided between the above-mentioned fiber optic ring assembly and the heat-conducting mounting seat 1.

[0043] Black magneto-anodic oxidation treatment layers are provided on the surfaces of the fiber optic ring and the heat-conducting mounting seat 1.

[0044] The described modulation and demodulation circuit is a digital-analog hybrid module integrating functions of FPGA, preamplification, A / D conversion, D / A conversion, and post-amplification. Each modulation and demodulation circuit corresponds to one axis for sampling, and three FPGA chips are used independently for modulation and demodulation for each axis of the gyroscope.

[0045] The length of the fiber optic ring is 220 mm, and the diameter of the fiber optic ring is 32 mm; The fiber optic ring uses a frameless fiber optic ring based on 80um polarization-maintaining fiber; The coupler uses a 1×3 coupler, and the coupling module uses a 2×2 coupler.

[0046] The light source uses an SLD light source, the optical sensing module uses a photodetector, the light source driving circuit uses a constant current source driving circuit, and the temperature control circuit uses an intelligent temperature control circuit. The constant current source driving circuit and the intelligent temperature control circuit can use any circuit system disclosed in the prior art that can achieve the corresponding functions, and the connection structure of each circuit will not be specifically described.

[0047] The design process of the micro - miniaturized three - axis integrated fiber optic gyroscope described in the present invention is as follows. The index requirements of the micro - miniaturized three - axis integrated fiber optic gyroscope are extremely demanding. It is necessary to integrate a three - axis fiber optic gyroscope with a performance better than 0.5 <°> / h within an extremely limited space (not greater than 60mm×60mm×48mm). It is extremely difficult to achieve according to the existing conventional technical level. The design of the present invention adopts advanced system structure design technology, establishes a digital three - dimensional model of the whole machine and a system layout and wiring simulation model, and conducts simulation analysis and optimization on thermal design to obtain the best structural design layout.

[0048] For a fiber optic gyroscope, a good system structure design can suppress its magnetic field sensitivity and improve its temperature stability. The miniaturized structure design is the premise for the miniaturization and low cost of this product. When conducting the structure design, in accordance with the design requirements of separating optoelectronics for installation and isolating heat and cold, the optical devices and circuit components are reasonably arranged. Based on reasonable heat dissipation, the light source and detector components share the height and width space. On the premise of ensuring the convenience of assembly, debugging, maintainability, and that the bending radius of the optical fiber pigtail of the optical device meets the requirements, the system layout of the product is realized with the smallest space. The three - dimensional layout of the system simulation of the micro - miniaturized three - axis integrated fiber optic gyroscope is as Figure 2 shown.

[0049] The design key points of the micro - miniaturized three - axis integrated fiber optic gyroscope described in the present invention are as follows:

[0050] 1) Optoelectronic separation

[0051] The fiber optic ring assembly of the fiber optic gyroscope prototype is far from the heat - generating parts such as the circuit module and the light source, reducing the startup time of the gyroscope prototype.

[0052] 2) Thermal design

[0053] The main heat - generating device, the SLD light source, is in direct contact with the base. When assembling, thermal conductive silicone grease is added to the contact surface, so that the heat generated by the SLD light source is quickly conducted to the housing through the base; the heat generated by the micro - circuit module is conducted to the base through the support columns, and then the heat is quickly conducted to the housing through the base; thermal isolation is achieved by adding ceramic fiber paper with a lower thermal conductivity between the fiber optic ring assembly and the mounting base; the area of the mounting contact surface is increased, and the inner and outer surfaces are subjected to black magneto - anodic oxidation treatment to increase the thermal conductivity. All the above thermal control measures can avoid the influence of system heat on the fiber optic ring assembly.

[0054] To verify the reliability and correctness of the above - mentioned system model, the structure as Figure 2 shown was subjected to simulation analysis, including modal analysis and thermal analysis. Through repeated iteration, an optimal system structure design scheme was obtained until.

[0055] a) Modal analysis

[0056] The modal analysis results show that the first resonant frequency of the fiber optic gyroscope is 2045 Hz. The parts with larger structural deformation are on the outer shield, while the fiber optic ring assembly of the optical sensitive module basically has no deformation. The simulation results indicate that the structural scheme of the micro-miniature three-axis integrated fiber optic gyroscope system has extremely little impact on the performance of the fiber optic gyroscope, and the scheme is feasible.

[0057] b) Thermal analysis

[0058] Using the digital system simulation three-dimensional structure model of the micro-miniature three-axis integrated fiber optic gyroscope, a thermal simulation model is established. The analysis results show that the heat sources of the micro-miniature three-axis integrated fiber optic gyroscope are concentrated in the constant current source drive module, modulation and demodulation module, light source, etc., and there are fast leakage channels, all of which are far from the fiber optic ring, and have little impact on the performance indicators of the fiber optic gyroscope.

[0059] For the micro-miniature optical path design, for the fiber optic gyroscope, its measurement accuracy is jointly determined by the optical path and the circuit. Currently, the modulation and demodulation circuit technology of the digital closed-loop fiber optic gyroscope has been very mature. Regardless of the gyroscope accuracy, the principles of its modulation and demodulation circuits and the adopted circuit principles are basically the same. Therefore, to not reduce the measurement accuracy of the fiber optic gyroscope after significantly reducing the equivalent area of the fiber optic ring, only the optical path design can be started.

[0060] The ultimate accuracy of the fiber optic gyroscope is mainly determined by shot noise and relative intensity noise of the light source. The specific relationship is shown in the following formula:

[0061]

[0062] In the formula: e is the electron charge, RD is the detector responsivity, P is the optical power, φ0 is the bias phase, c is the speed of light in vacuum, λ is the average optical wavelength, f is the light source bandwidth, L is the fiber length, and D is the fiber optic ring diameter.

[0063] Shot noise and relative intensity noise of the light source, as the inherent noise in the optoelectronic detection process, are difficult to be completely eliminated and can only be suppressed. From the above formula, after taking measures such as broadband light source and phase overmodulation, increasing the equivalent area of the fiber optic ring (LD) becomes the most fundamental and effective measure to improve the gyroscope accuracy. However, simply increasing the equivalent area of the fiber optic ring (fiber length or fiber optic ring diameter) is a contradiction with the micro-miniature requirements and cannot be taken into account simultaneously. The outer dimensions of the micro-miniature three-axis integrated fiber optic gyroscope are only 60 mm × 60 mm × 48 mm, such as Figure 3As shown in the figure, it adopts a one-to-three closed-loop fiber optic gyroscope solution based on conventional 80 / 135um polarization-maintaining fiber. The length of the fiber optic loop is 220, and the diameter of the fiber optic loop is 32mm. Its measurement accuracy limit can only reach about 0.3° / h. After considering the influence of various noise disturbances, it cannot reach the expected measurement accuracy. Therefore, based on the technology of this micro-miniature three-axis fiber optic gyroscope, this project intends to conduct targeted research on various technical solutions to improve the measurement accuracy. Without increasing the external dimensions of the fiber optic loop, it focuses on taking measures such as a frameless fiber optic loop based on 80um polarization-maintaining fiber and a double optical path interference optical path to significantly increase the equivalent area of the fiber optic loop and suppress the optical path noise, ultimately achieving a measurement accuracy requirement better than 0.5° / h.

[0064] 3. High-integration and low-power SOC circuit design

[0065] The circuit components of the micro-miniature three-axis integrated fiber optic gyro mainly consist of a modulation and demodulation SOC microcircuit and a light source drive SOC microcircuit. The modulation and demodulation SOC microcircuit has an information processing module with an embedded FPGA chip. The information processing modules between different modulation and demodulation SOC microcircuits are connected for communication and are also connected to the waveguide of the corresponding fiber optic loop component. An optical sensing module for realizing optical signal connection with the coupling module of the fiber optic loop component is also provided on the information processing module; the light source drive SOC microcircuit is encapsulated by a light source drive circuit for controlling the light source and a temperature control circuit for monitoring the temperature of the light source and the inside of the housing. The temperature control circuit is connected to the light source drive circuit.

[0066] 1) Modulation and demodulation SOC microcircuit

[0067] The modulation and demodulation SOC microcircuit of the micro-miniature three-axis integrated fiber optic gyro is a digital-analog hybrid circuit integrating functions such as FPGA, pre-amplification, A / D conversion, D / A conversion, and post-amplification. It processes weak signals at the microvolt level. The performance of the modulation and demodulation circuit restricts technical parameters such as gyro noise, threshold, and resolution. At the same time, it is a high-speed digital signal processing circuit designed based on FPGA technology. Its information processing cycle is about 5ns. A tiny change in the internal circuit delay time when the temperature changes may also cause catastrophic consequences. Therefore, in order to reduce the system design risk and reduce the crosstalk between axes, one modulation and demodulation circuit corresponds to one axis for internal sampling in the gyro. Each axis of the gyro uses three FPGA chips to independently perform modulation and demodulation. The principle block diagram is shown in Figure 4 .

[0068] This design integrates all functions such as A / D sampling demodulation, D / A output modulation, power supply circuit, communication interface, etc. into a micro-system circuit module. The overall size requirement is no more than 30mm×30mm×6mm, and the integration requirement is very high compared with traditional designs. Therefore, two miniaturization integration technologies, namely package integration (SOC) and PCB chip embedded process, are considered for comprehensive adoption. First, it is necessary to determine the functions and performance indicators required for the micro-circuit module according to the system requirements. Secondly, it is necessary to reasonably design the architecture of the micro-system module according to the characteristics of the two miniaturization technologies, merge and divide functional units, and determine the units to be implemented by package integration and the units to be implemented by PCB embedded process. Finally, it is necessary to consider the integration optimization problem of the micro-circuit design and the external structure design problem. At the same time, analyze and optimize the power consumption of the modulation and demodulation SOC micro-circuit to ensure that the static power consumption of each module is no more than 0.8W.

[0069] 2) Light source drive SOC micro-circuit

[0070] The light source used inside the fiber optic gyroscope must adopt a combined scheme of constant current drive and chip temperature control to ensure the optical power stability and average wavelength stability of the light source within the full temperature range. In this project, the constant current drive and temperature control functions are integrated into a micro-system circuit module. The overall size requirement is no more than 24mm×24mm×8mm. The principle of the constant current source drive circuit is shown in Figure 5 . It can be seen from the figure that the power consumption of the constant current source drive circuit is mainly consumed on the light source chip and the sampling resistor Rs. It is necessary to reasonably optimize the circuit principle, study the best ratio of the power distribution of the two parts, and improve the circuit drive efficiency. Analyze and optimize the power consumption of the light source drive SOC micro-circuit to ensure that the static power consumption of this module is no more than 2W. Thus, ensure that the static power consumption of the micro-miniature three-axis integrated fiber optic gyroscope is no more than 5W.

[0071] 4. Design for suppressing relative intensity noise of the light source

[0072] The relative intensity noise of the light source is one of the main noises in the fiber optic gyroscope. When the diameter of the fiber optic sensitive component - the fiber optic ring of the fiber optic gyroscope decreases, the bending loss and bending stress increase, resulting in an increase in attenuation. Therefore, only the output optical power of the light source of the fiber optic gyroscope can be increased. As the power of the light source gradually increases, the relative intensity noise of the light source has become a key factor restricting the measurement accuracy of the fiber optic gyroscope. The relative intensity noise suppression technology is one of the key technologies for the micro-miniature three-axis integrated fiber optic gyroscope to have no lower accuracy than the previous generation product. This project adopts the single detector intensity cancellation technology to control the intensity of the reference light to be the same as that of the signal light and the time difference between the reference light and the signal light reaching the detector is always one, and uses the closed-loop principle of the fiber optic gyroscope - subtracting adjacent optical signals, so as to achieve relative intensity noise cancellation. The principle of relative intensity noise cancellation is shown in Figure 6 .

[0073] 5. General Modulation and Demodulation Software Design

[0074] The modulation and demodulation software adopts an external synthesis differential modulation scheme based on a single parallel D / A converter, and optimizes and improves the feedback signal, the number of bits of the modulation signal, the superposition method, etc. to suppress the noise source as much as possible. The implementation method of the external synthesis differential modulation scheme based on a single parallel D / A converter is to set the reset of the feedback staircase wave from 16-bit automatic overflow (0 - 65535) to 15-bit automatic overflow (0 - 32767), and then digitally superimpose it with a 15-bit offset modulation signal, so as to ensure that the result after superposition does not exceed the maximum range represented by 16-bit binary data. See the software principle block diagram in Figure 7 .

[0075] The micro-miniature three-axis integrated fiber optic gyroscope includes a three-axis modulation and demodulation microcircuit module. However, when users use it, they need to externally send the data of the X, Y, and Z-axis fiber optic gyroscopes through a single serial communication interface. To synchronize the data of the three axes and make the software general, a data coordination communication module needs to be added to the modulation and demodulation software to complete the functions of synchronizing, framing, and sending the gyro data of the three axes. After considering the software generality, see the schematic diagram of the modulation and demodulation software interface in Figure 8 shown, and the hardware connection relationship of the three-axis modulation and demodulation microcircuit is as Figure 9 shown.

[0076] 6. Intelligent Temperature Control Design

[0077] The SLD light source die is usually kept at a constant temperature of +25°C, and its internal thermoelectric cooling scheme has a maximum cooling temperature difference not greater than 67°C. The test data shows that the stable operating temperature range of the light source can reach -45°C to +65°C. When the ambient temperature reaches 70°C, two situations may occur: ① The cooling capacity is sufficient, the temperature control current increases significantly, and the overall power consumption of the machine increases; ② The cooling capacity is insufficient, the temperature control system gets out of control, and constant temperature control cannot be achieved. To reduce the power consumption of the light source drive microsystem within the full temperature range to not more than 2W and ensure stable and reliable operation within the range of -45°C to +70°C, the problem of the light source operating in a wide temperature range must be solved. As Figure 10 shown, this design adopts an SLD light source intelligent temperature control system according to the characteristics of the SLD light source, and sets the constant temperature point of the light source to 20°C (when the ambient temperature is -45°C to +60°C, existing technology) and 35°C adjustable (when the ambient temperature is greater than +60°C) to ensure that the fiber optic gyroscope can work reliably within the full temperature range, reduce the temperature control temperature difference, and reduce the overall power consumption of the machine.

[0078] In summary, the present invention designs an all-80um fine-diameter optical fiber optical path, achieving the best matching characteristics, enabling the fiber optic gyroscope to use a shorter fiber optic loop (190m - 210m), realizing miniaturization while meeting the product accuracy; designs a general-purpose modulation and demodulation microcircuit, achieving the consistency of the main and slave circuit boards and reducing the types of internal circuit boards of the product; designs a general-purpose FPGA software, implementing the interface circuit of the traditional solution with SPI communication, creating conditions for the miniaturization of the fiber optic gyroscope; the light source adopts an intelligent temperature control design, broadening the working temperature range of the fiber optic gyroscope and enabling it to adapt to a more severe working environment.

[0079] As described above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A miniature three-axis integrated fiber optic gyroscope, characterized by: It includes a housing, an optical path component and a circuit component, wherein a heat-conducting mounting seat for fixing the optical path component and the circuit component is provided in the housing; The optical path assembly includes a light source, a coupler, an X-axis fiber optic ring assembly, a Y-axis fiber optic ring assembly, and a Z-axis fiber optic ring assembly. The X-axis fiber optic ring assembly, the Y-axis fiber optic ring assembly, and the Z-axis fiber optic ring assembly are all formed by sequentially connecting a fiber optic ring, a waveguide, and a coupling module. The coupling module is connected to the light source through a coupler. The fiber optic rings on different fiber optic ring assemblies are separately installed at different positions on the heat-conducting mounting base. The circuit assembly includes a modulation and demodulation SOC microcircuit corresponding to each axis inside the gyroscope and a light source driving SOC microcircuit for controlling the light source. The modulation and demodulation SOC microcircuit is provided with an information processing module embedded with an FPGA chip. The information processing modules of different modulation and demodulation SOC microcircuits are communicatively connected and are also connected to the waveguide of the corresponding optical fiber ring assembly. The information processing module is also provided with an optical sensing module that connects to the coupling module of the optical fiber ring assembly to achieve optical signal connection. The light source driving SOC microcircuit is encapsulated by a light source driving circuit for controlling the light source and a temperature control circuit for monitoring the temperature of the light source and the interior of the housing. The temperature control circuit is connected to the light source driving circuit. in, The modulation and demodulation software of the modulation and demodulation SOC microcircuit sets the reset of the feedback step wave from 16-bit automatic overflow to 15-bit automatic overflow, and then digitally superimposes it with the 15-bit bias modulation signal.

2. The miniature three-axis integrated fiber optic gyroscope according to claim 1, characterized in that: The light source is directly mounted on the heat-conducting mounting seat, and a heat-conducting silicone grease layer is coated on the contact surface of the light source connected to the heat-conducting mounting seat.

3. The miniature three-axis integrated fiber optic gyroscope according to claim 1, characterized in that: The circuit assembly is mounted on the heat-conducting mounting seat via heat-conducting pillars.

4. The miniature three-axis integrated fiber optic gyroscope according to claim 1, characterized in that: Ceramic fiber paper with low thermal conductivity is provided between the optical fiber ring assembly and the heat-conducting mounting seat.

5. The miniature three-axis integrated fiber optic gyroscope according to claim 1, characterized in that: A black magnetic anodizing layer is provided on the surfaces of the optical fiber ring and the heat-conducting mounting seat.

6. The miniature three-axis integrated fiber optic gyroscope according to claim 1, characterized in that: A fiber plate wound with optical fibers is fixed on the heat-conducting mounting seat.

7. The miniature three-axis integrated fiber optic gyroscope according to claim 1, characterized in that: The light source adopts an SLD light source, and the optical sensing module adopts a photodetector.

8. The miniature three-axis integrated fiber optic gyroscope according to claim 1, characterized in that: The light source driving circuit adopts a constant current source driving circuit, and the temperature control circuit adopts an intelligent temperature control circuit.

9. The miniature three-axis integrated fiber optic gyroscope according to claim 1, characterized in that: The length of the optical fiber ring is 220 mm, and the diameter of the optical fiber ring is 32 mm. The optical fiber ring is a skeleton-free optical fiber ring based on 80 μm polarization-maintaining optical fiber.

10. The miniature three-axis integrated fiber optic gyroscope according to claim 1, characterized in that: The coupler is a 1×3 coupler, and the coupling module is a 2×2 coupler.

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