Method for improving repeatability of scale factor of fiber-optic gyroscope through crystal oscillator frequency compensation

Abstract

The invention discloses a method for improving repeatability of a scale factor of a fiber-optic gyroscope through crystal oscillator frequency compensation. The method comprises the following steps: S1, crystal oscillator frequency monitoring: monitoring a reference crystal oscillator frequency in a fiber-optic gyroscope system in real time by using a high-precision frequency meter; and S2, frequency drift detection: detecting the drift distance of the crystal oscillator frequency by comparing the monitoring frequency with a reference value. And S3, frequency compensation calculation: calculating a corresponding compensation coefficient according to the detected frequency drift amount. And S4, scale factor adjustment: applying the compensation coefficient to scale factor calculation of the fiber-optic gyroscope, and adjusting the scale factor in real time to improve the repeatability of the scale factor. And S5, system calibration: the system is calibrated regularly to ensure the precision and reliability of compensation. According to the method disclosed by the invention, the repeatability of the scale factor of the fiber-optic gyroscope can be remarkably improved, the measurement error caused by crystal oscillator frequency drift is reduced, and the overall precision and stability of the system are improved.

Description

Technical Field

[0001] The invention relates to the technical field of fiber optic gyroscopes, and in particular to a method for improving the repeatability of a fiber optic gyroscope scale factor through crystal oscillator frequency compensation. Background Art

[0002] As a high-precision angular velocity sensor, fiber optic gyroscopes are widely used in aviation, aerospace, and marine navigation. However, the scale factor of a fiber optic gyroscope is affected by factors such as temperature and mechanical stress, which reduces its repeatability and affects the measurement accuracy. Existing fiber optic gyroscope systems mainly use methods such as temperature compensation to improve the stability of the scale factor, but these methods cannot completely solve the problem of scale factor changes caused by crystal oscillator frequency drift.

[0003] The crystal oscillator in the fiber optic gyroscope provides the clock signal for the A / D converter and the D / A converter in the digital closed-loop circuit, and has an important influence on the frequency of the output data of the fiber optic gyroscope. According to the working principle of the digital closed-loop fiber optic gyroscope, the sampling frequency of the A / D converter, the integration period of the sampling value, the generation of the step wave, the bias modulation frequency of the square wave, and the output frequency of the D / A converter are all strictly corresponding to the intrinsic frequency of the gyroscope. Any deviation or error caused by asynchrony can seriously affect the performance of the gyroscope after a long period of accumulation, and even cause the gyroscope to fail to work normally. Therefore, a unified clock signal should be used in the logic processing part to strictly control the working timing of each logic module. This also puts forward higher requirements on the performance of the external clock. The selection of the external crystal oscillator needs to consider indicators such as frequency value, frequency stability and temperature coefficient. Studies have found that temperature is one of the important factors affecting the frequency of the crystal oscillator. When the temperature changes, the frequency characteristics of the crystal oscillator will be affected, which can affect the test of the scale factor. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a method for improving the repeatability of the scale factor of a fiber optic gyroscope by crystal oscillator frequency compensation, which effectively solves the problem of unstable scale factor caused by crystal oscillator frequency drift and is suitable for a wide range of applications of high-precision fiber optic gyroscopes.

[0005] In order to solve the above problems, the present invention provides a method for improving the repeatability of the scale factor of a fiber optic gyroscope by crystal oscillator frequency compensation, comprising the following steps:

[0006] S1. Crystal oscillator frequency monitoring: Use a high-precision frequency meter to monitor the reference crystal oscillator frequency in the fiber optic gyroscope system in real time;

[0007] S2. Frequency drift detection: Detect the drift of the crystal oscillator frequency by comparing the monitoring frequency with the reference value;

[0008] The output frequency value of the crystal oscillator in the digital closed-loop circuit at different temperature points is obtained by testing, and the frequency offset of the crystal oscillator at different temperature points is calculated;

[0009] S3. Frequency compensation calculation: Calculate the corresponding compensation coefficient according to the detected frequency drift;

[0010] S4. Scale factor adjustment: applying the compensation coefficient to the scale factor calculation of the fiber optic gyroscope, and adjusting the scale factor in real time to improve its repeatability;

[0011] S5. System calibration: Calibrate the system regularly to ensure the accuracy and reliability of compensation.

[0012] Preferably, in S1, the fiber optic gyro digital closed-loop demodulation board is placed separately in a high and low temperature box for temperature testing over the full temperature range to eliminate the influence of the light source and the fiber optic sensitive ring on the scale factor; a high-precision frequency meter is used to measure the frequency values ​​output by the crystal oscillator at different temperature points with a temperature interval of 10°C.

[0013] Preferably, S3 includes a crystal oscillator in a digital closed-loop circuit providing a common clock signal, which is not only related to the intrinsic frequency of the fiber optic gyroscope, but also can affect the frequency of the output data of the fiber optic gyroscope; when the temperature changes, the frequency of the crystal oscillator will change due to the influence of the temperature, thereby causing the frequency of the output data to change; since the internal frequency division circuit of a certain type of high-precision fiber optic gyroscope used is fixed, the crystal oscillator frequency changes after passing through the frequency division circuit, and then the frequency of the output data can be obtained by reducing it through the digital filter circuit; therefore, when the temperature changes, the ratio of the frequency of the output data to the frequency before the change can be expressed as:

[0014]

[0015] Among them, f s ′ represents the frequency value of the output data after the temperature changes; f s represents the frequency value of the output data when the temperature does not change; f represents the value of the crystal frequency after the temperature changes; f0 represents the value of the crystal frequency when the temperature does not change; the angular increment method is used to measure the scale factor of the fiber optic gyroscope; the specific implementation method is to place the fiber optic gyroscope on a turntable, and the turntable is positioned at an arbitrary angle α before the start of operation, and the positioning angle after the operation is completed is recorded as α'; then the incremental angle of the turntable ΔΩ=α′-α, and the incremental angle is an integer multiple of 360°, that is, the number of full turns of the turntable; the time taken for the turntable to rotate the ΔΩ incremental angle is t, the number of output pulses in this process is recorded as n, and the sum is recorded as F T ; Record the zero bias mean value F of the fiber optic gyroscope within t' time before sampling bT The zero bias mean value within the sampling end time t' is set to F aT; Then the zero bias value F of each pulse output by the fiber optic gyroscope is cT for:

[0016]

[0017] When calculating the scale factor, the effective pulse output of the fiber optic gyroscope is required; its effective pulse output is: the total pulse F of the turntable in time t T Subtract the zero bias value F of n pulses cT ; K0 represents the scale factor value when the input angular velocity is a fixed value Ω0, and its expression is:

[0018]

[0019] When the temperature changes, the input angular velocity is still set to Ω0, and the turntable rotation increment angle remains unchanged, still ΔΩ. At this time, the scale factor K′ is:

[0020]

[0021] According to formulas (1), (3) and (4), the proportional relationship between the temperature change and the scale factor change is:

[0022]

[0023] Formula (5) shows that when any other influencing factors do not change, the scale factor of the fiber optic gyroscope is inversely proportional to the crystal frequency in the fiber optic gyroscope; based on the frequency data table of different temperature points obtained by S2, the scale factor compensation coefficients at different temperature points are calculated.

[0024] Preferably, in S5, since the generation of high-precision oscillation frequency comes from the piezoelectric effect of the quartz crystal; changes in factors such as temperature, crystal aging, and excitation level can affect the crystal frequency; the system needs to calibrate the crystal frequency scale factor compensation coefficient after a certain period of use.

[0025] The advantages of the present invention compared with the prior art are:

[0026] The method of the present invention for improving the repeatability of the scale factor of the fiber optic gyroscope by crystal oscillator frequency compensation can significantly improve the repeatability of the scale factor of the fiber optic gyroscope, reduce the measurement error caused by the crystal oscillator frequency drift, and improve the overall accuracy and stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 : is a framework diagram of the fiber optic gyro scale factor compensation system of the present invention;

[0029] Figure 2 : is the working flow chart of the crystal oscillator frequency monitoring and compensation module in the present invention. DETAILED DESCRIPTION

[0030] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0031] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0033] In order to solve the above problems, a method for improving the repeatability of the scale factor of an optical fiber gyroscope by crystal oscillator frequency compensation of the present invention comprises the following steps:

[0034] S1. Crystal oscillator frequency monitoring: Use a high-precision frequency meter to monitor the reference crystal oscillator frequency in the fiber optic gyroscope system in real time;

[0035] S2. Frequency drift detection: Detect the drift of the crystal oscillator frequency by comparing the monitoring frequency with the reference value;

[0036] The output frequency value of the crystal oscillator in the digital closed-loop circuit at different temperature points is obtained by testing, and the frequency offset of the crystal oscillator at different temperature points is calculated;

[0037] S3. Frequency compensation calculation: Calculate the corresponding compensation coefficient according to the detected frequency drift;

[0038] S4. Scale factor adjustment: applying the compensation coefficient to the scale factor calculation of the fiber optic gyroscope, and adjusting the scale factor in real time to improve its repeatability;

[0039] S5. System calibration: Calibrate the system regularly to ensure the accuracy and reliability of compensation.

[0040] Preferably, in S1, the fiber optic gyro digital closed-loop demodulation board is placed separately in a high and low temperature box for temperature testing over the full temperature range to eliminate the influence of the light source and the fiber optic sensitive ring on the scale factor; a high-precision frequency meter is used to measure the frequency values ​​output by the crystal oscillator at different temperature points with a temperature interval of 10°C.

[0041] Preferably, S3 includes a crystal oscillator in a digital closed-loop circuit providing a common clock signal, which is not only related to the intrinsic frequency of the fiber optic gyroscope, but also can affect the frequency of the output data of the fiber optic gyroscope; when the temperature changes, the frequency of the crystal oscillator will change due to the influence of the temperature, thereby causing the frequency of the output data to change; since the internal frequency division circuit of a certain type of high-precision fiber optic gyroscope used is fixed, the crystal oscillator frequency changes after passing through the frequency division circuit, and then the frequency of the output data can be obtained by reducing it through the digital filter circuit; therefore, when the temperature changes, the ratio of the frequency of the output data to the frequency before the change can be expressed as:

[0042]

[0043] Among them, f s ′ represents the frequency value of the output data after the temperature changes; f s represents the frequency value of the output data when the temperature does not change; f represents the value of the crystal frequency after the temperature changes; f0 represents the value of the crystal frequency when the temperature does not change; the angular increment method is used to measure the scale factor of the fiber optic gyroscope; the specific implementation method is to place the fiber optic gyroscope on a turntable, and the turntable is positioned at an arbitrary angle α before the start of operation, and the positioning angle after the operation is completed is recorded as α'; then the incremental angle of the turntable ΔΩ=α′-α, and the incremental angle is an integer multiple of 360°, that is, the number of full turns of the turntable; the time taken for the turntable to rotate the ΔΩ incremental angle is t, the number of output pulses in this process is recorded as n, and the sum is recorded as F T ; Record the zero bias mean value F of the fiber optic gyroscope within t' time before sampling bT The zero bias mean value within the sampling end time t' is set to F aT ; Then the zero bias value F of each pulse output by the fiber optic gyroscope is cT for:

[0044]

[0045] When calculating the scale factor, the effective pulse output of the fiber optic gyroscope is required; its effective pulse output is: the total pulse F of the turntable in time t T Subtract the zero bias value F of n pulses cT ; K0 represents the scale factor value when the input angular velocity is a fixed value Ω0, and its expression is:

[0046]

[0047] When the temperature changes, the input angular velocity is still set to Ω0, and the turntable rotation increment angle remains unchanged, still ΔΩ. At this time, the scale factor K′ is:

[0048]

[0049] According to formulas (1), (3) and (4), the proportional relationship between the temperature change and the scale factor change is:

[0050]

[0051] Formula (5) shows that when any other influencing factors do not change, the scale factor of the fiber optic gyroscope is inversely proportional to the crystal frequency in the fiber optic gyroscope; based on the frequency data table of different temperature points obtained by S2, the scale factor compensation coefficients at different temperature points are calculated.

[0052] Preferably, in S5, since the generation of high-precision oscillation frequency comes from the piezoelectric effect of the quartz crystal; changes in factors such as temperature, crystal aging, and excitation level can affect the crystal frequency; the system needs to calibrate the crystal frequency scale factor compensation coefficient after a certain period of use.

[0053] In order to more clearly illustrate the specific embodiments of the present invention, several embodiments are provided below:

[0054] Embodiment 1:

[0055] A crystal frequency monitoring module is introduced into the fiber optic gyro system, and a high-precision frequency meter is used to monitor the crystal frequency in real time. This frequency meter has the characteristics of high precision, high stability and wide frequency range, and can accurately measure frequency signals from a few Hz to tens of GHz. The frequency data is sampled every 10 seconds and compared with the standard reference frequency. If the frequency drift is detected to exceed the set threshold, the compensation coefficient is immediately calculated and applied to the calculation of the scale factor. The adjusted scale factor is verified through the system feedback mechanism to ensure its accuracy.

[0056] Embodiment 2:

[0057] Through actual measurement, the repeatability improvement of the fiber optic gyroscope scale factor after the crystal oscillator frequency compensation method was verified. The experimental results show that in multiple ambient temperature change experiments, the repeatability of the fiber optic gyroscope scale factor after compensation is improved from ≤15ppm before compensation to ≤5ppm, proving the effectiveness of the method of the present invention.

[0058] Finally, all the parts not described in the present invention adopt mature products and mature technical means of the existing technology.

[0059] The present invention and its embodiments are described above, and such description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A method for improving the repeatability of a fiber optic gyroscope scale factor by crystal oscillator frequency compensation, characterized in that: The following steps are involved: S1. Crystal oscillator frequency monitoring: Use a high-precision frequency meter to monitor the reference crystal oscillator frequency in the fiber optic gyro system in real time; S2. Frequency drift detection: Detect the drift of the crystal oscillator frequency by comparing the monitoring frequency with the reference value; The output frequency value of the crystal oscillator in the digital closed-loop circuit at different temperature points is obtained by testing, and the frequency offset of the crystal oscillator at different temperature points is calculated; S3. Frequency compensation calculation: Calculate the corresponding compensation coefficient according to the detected frequency drift; S4. Scale factor adjustment: applying the compensation coefficient to the scale factor calculation of the fiber optic gyroscope, and adjusting the scale factor in real time to improve its repeatability; S5. System calibration: Calibrate the system regularly to ensure the accuracy and reliability of compensation.

2. The method for improving the repeatability of the scale factor of a fiber optic gyroscope by crystal oscillator frequency compensation according to claim 1, characterized in that: In S1, the fiber optic gyro digital closed-loop demodulation board is placed in a high and low temperature box alone to perform a temperature test over a full temperature range to eliminate the influence of the light source and the fiber optic sensitive ring on the scale factor; a high-precision frequency meter is used to measure the frequency values ​​output by the crystal oscillator at different temperature points under a temperature interval of 10°C.

3. The method for improving the repeatability of the scale factor of a fiber optic gyroscope by crystal oscillator frequency compensation according to claim 1, characterized in that: The S3 includes a crystal oscillator in a digital closed-loop circuit to provide a common clock signal, which is not only related to the intrinsic frequency of the fiber optic gyroscope, but also can affect the frequency of the output data of the fiber optic gyroscope; when the temperature changes, the frequency of the crystal oscillator will change due to the influence of the temperature, thereby causing the frequency of the output data to change; since the internal frequency division circuit of a certain type of high-precision fiber optic gyroscope used is fixed, the crystal oscillator frequency changes after passing through the frequency division circuit, and then the frequency of the output data can be obtained by reducing it through the digital filter circuit; therefore, when the temperature changes, the ratio of the frequency of the output data to the frequency before the change can be expressed as: Among them, f s ′ represents the frequency value of the output data after the temperature changes; f s represents the frequency value of the output data when the temperature does not change; f represents the value of the crystal frequency after the temperature changes; f0 represents the value of the crystal frequency when the temperature does not change; the angular increment method is used to measure the scale factor of the fiber optic gyroscope; the specific implementation method is to place the fiber optic gyroscope on a turntable, and the turntable is positioned at an arbitrary angle α before the start of operation, and the positioning angle after the operation is completed is recorded as α'; then the incremental angle of the turntable ΔΩ=α′-α, and the incremental angle is an integer multiple of 360°, that is, the number of full turns of the turntable; the time taken for the turntable to rotate the ΔΩ incremental angle is t, the number of output pulses in this process is recorded as n, and the sum is recorded as F T ; Record the zero bias mean value F of the fiber optic gyroscope within t' time before sampling bT The zero bias mean value within the sampling end time t' is set to F aT ; Then the zero bias value F of each pulse output by the fiber optic gyroscope is cT for: When calculating the scale factor, the effective pulse output of the fiber optic gyroscope is required; its effective pulse output is: the total pulse F of the turntable in time t T Subtract the zero bias value F of n pulses cT ; K0 represents the scale factor value when the input angular velocity is a fixed value Ω0, and its expression is: When the temperature changes, the input angular velocity is still set to Ω0, and the turntable rotation increment angle remains unchanged, still ΔΩ. At this time, the scale factor K′ is: According to formulas (1), (3) and (4), the proportional relationship between the temperature change and the scale factor change is: Formula (5) shows that when any other influencing factors do not change, the scale factor of the fiber optic gyroscope is inversely proportional to the crystal frequency in the fiber optic gyroscope; based on the frequency data table of different temperature points obtained by S2, the scale factor compensation coefficients at different temperature points are calculated.

4. The method for improving the repeatability of the scale factor of a fiber optic gyroscope by crystal oscillator frequency compensation according to claim 1, characterized in that: In S5, since the generation of high-precision oscillation frequency comes from the piezoelectric effect of the quartz crystal; changes in factors such as temperature, crystal aging, and excitation level can affect the crystal frequency; the system needs to calibrate the crystal frequency scale factor compensation coefficient after a certain period of use.

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