A method and apparatus for determining the modulation depth of a fiber optic gyroscope.

Abstract

This invention provides a method and apparatus for determining the modulation depth of a fiber optic gyroscope. The method includes the following steps: Step A: Constructing a test waveform; Step B: A signal processor outputs the test waveform, which serves as the modulation waveform. The operating temperature of the fiber optic gyroscope is set to P preset temperature values. When the operating temperature is set to the p-th preset temperature value, a p-th static test is performed on the fiber optic gyroscope; Step C: Based on the zero-bias stability value obtained from the p-th static test, the modulation depth parameter β_p corresponding to the minimum zero-bias stability value is determined when the operating temperature of the fiber optic gyroscope is set to the p-th preset temperature value; Step D: The modulation depth β is calculated using the modulation depth parameter and the digital quantity of the D / A converter corresponding to the 2π phase of the modulation waveform; The P preset temperature values ​​include at least the room temperature operating temperature, the minimum operating temperature, and the maximum operating temperature of the fiber optic gyroscope.

Description

Technical Field

[0001] This invention relates to the software design and debugging of a fiber optic gyroscope, and in particular to a method for determining the modulation depth of a fiber optic gyroscope. Background Technology

[0002] The modulation depth of a fiber optic gyroscope is one of the key parameters affecting its performance, mainly involving the parameter settings of the phase modulator and its impact on system sensitivity and signal-to-noise ratio.

[0003] Fiber optic gyroscopes are based on the Sagnac effect, measuring rotational angular velocity by detecting the phase difference between two counter-propagating light waves. A phase modulator (Y-waveguide or piezoelectric ceramic) is typically used to introduce a periodic modulation signal to demodulate the phase difference caused by rotation. Common modulation waveforms include square waves, sine waves, sawtooth waves, four-state waves, or random waves. In a fiber optic gyroscope, the signal emitted by the light source is split into two optical signals by a coupler and a Y-waveguide. These signals then pass through a fiber optic loop, then sequentially through the Y-waveguide and another coupler before being detected by a photodetector. An A / D converter receives the signal from the photodetector, processes it in a signal processing unit, and then a D / A converter outputs the modulated signal to the modulation electrode of the Y-waveguide.

[0004] Modulation depth is defined as the maximum phase shift (Δφ) caused by the phase change amplitude signal applied by the phase modulator, usually expressed in radians. For example, modulation depth can be expressed as π / 2.

[0005] Modulation depth parameter definition: The modulation depth parameter is an indicator in the software design of a fiber optic gyroscope. Whether open-loop or closed-loop, fiber optic gyroscopes typically use a DSP or FPGA as the signal processor. The signal processor generates a modulation waveform according to the modulation depth requirements. The digital quantity corresponding to the amplitude of the modulation waveform is the modulation depth parameter. The modulation waveform acts on a D / A converter, which converts the digital quantity into an analog voltage. This analog voltage acts on the electrodes of the phase modulator, which modulates the phase of the optical signal passing through it based on the photoelectric effect. In a fiber optic gyroscope, the phase modulator (Y-waveguide or piezoelectric modulator) is the actuator that performs phase modulation. The modulation depth parameter is a parameter written in the signal processor (e.g., FPGA or DSP) program. The modulation depth parameter is directly proportional to the modulation depth. Changes in the modulation depth parameter result in changes in the voltage acting on the electrodes of the phase modulator (Y-waveguide or piezoelectric modulator), and consequently, changes in the modulation depth produced by the phase modulator (Y-waveguide or piezoelectric modulator). By adjusting the modulation depth parameter value, different modulation depth designs can be achieved.

[0006] The modulation depth of a fiber optic gyroscope is a quantitative indicator of the phase modulation amplitude, directly affecting the system's sensitivity and accuracy. Appropriately selecting the modulation depth and optimizing it in conjunction with the modulation method is one of the core technologies for improving fiber optic gyroscope performance. Therefore, obtaining the modulation depth of a fiber optic gyroscope is an important aspect of its design.

[0007] Determining the modulation depth of a fiber optic gyroscope is a core step in system design and optimization, typically involving theoretical analysis, experimental calibration, and closed-loop feedback control. The following are the commonly used methods and steps:

[0008] 1. Theoretical calculation method

[0009] The modulation depth β is estimated by using the formula β=(π×V_d) / V_π.

[0010] Where V_π is the half-wave voltage and V_d is the driving voltage. The half-wave voltage V_π is determined by the material and structure of the phase modulator and needs to be measured experimentally (e.g., by applying a voltage scan and measuring the periodic changes in the output light intensity).

[0011] This method is suitable for estimating the modulation depth when the modulator parameters are known, but it cannot obtain the optimal modulation depth.

[0012] 2. Experimental calibration method

[0013] The modulation depth is obtained by following these steps:

[0014] 1) Set up the test system:

[0015] The fiber optic gyroscope operates in open-loop mode with the rotational angular velocity input removed, and static testing is employed. The output optical signal is monitored using a photodetector (PD) and an oscilloscope / spectrum analyzer.

[0016] 2) Apply a modulation signal:

[0017] Input a sinusoidal or square wave modulated signal and gradually increase the driving voltage V_d. Record the amplitude and harmonic components (such as the fundamental and second harmonic amplitudes) of the output signal.

[0018] 3) Analyze signal characteristics:

[0019] When using sinusoidal modulation: observe the change of the fundamental amplitude with V_d. When the fundamental amplitude is at its maximum, it corresponds to β=π / 2 (Bessel function characteristics).

[0020] When using square wave modulation (±π / 2 phase step): Observe the light intensity waveform with an oscilloscope and adjust V_d to make the phase step amplitude π / 2. At this time, the modulation depth is optimal.

[0021] 4) Determine the optimal operating point: Estimate the modulation depth based on the fundamental amplitude and harmonic component magnitude.

[0022] Experimental calibration is suitable for estimating modulation depth, but it cannot obtain the optimal modulation depth.

[0023] 3. Square wave phase modulation method

[0024] A ±π / 2 phase step modulation is applied, and the phase difference between the two optical waves is directly adjusted to a non-reciprocal phase by adjusting the driving voltage. The slope of the demodulated output signal is measured, and the optimal modulation depth is found when the slope is maximum and the noise is minimum.

[0025] 4. Sawtooth wave modulation method

[0026] The modulation depth needs to cover the entire dynamic range to avoid jump errors during phase reset. The smoothness of the reset point is observed to determine if the modulation depth is appropriate.

[0027] Of the modulation depth determination methods described above, theoretical calculation and experimental calibration are indirect methods, not directly linked to the gyroscope's operating process. Beyond existing fiber optic gyroscope equipment, theoretical calculation requires experimental measurement of the half-wave voltage of the phase modulator, while experimental calibration requires additional experimental steps and observation using an oscilloscope. Square wave phase modulation and sawtooth wave modulation are related to the gyroscope's modulation process, but determining the modulation depth relies on measurement tools such as oscilloscopes. The accuracy of the modulation depth is significantly affected by the measurement tools, essentially making them also indirect methods for determining modulation depth. Summary of the Invention

[0028] The problem this invention aims to solve is that existing methods for determining modulation depth require experimental measurements and oscilloscopes, which are not available with existing fiber optic gyroscopes, to determine the modulation depth. This invention provides a method for determining the modulation depth of a fiber optic gyroscope.

[0029] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for determining the modulation depth of a fiber optic gyroscope, wherein the fiber optic gyroscope includes a signal processor for outputting a modulation waveform, a D / A converter for receiving the modulation waveform, and a phase modulator, wherein the signal processor, the D / A converter, and the phase modulator are electrically connected in sequence, and the determination method includes the following steps:

[0030] Step A: Construct a test waveform, wherein the modulation depth parameter corresponding to the start time of the test waveform is a preset initial value β_0 of the modulation depth parameter, the modulation depth parameter corresponding to the test waveform increases stepwise with time, and the increment of the modulation depth parameter is a preset step size value β_b;

[0031] Step B: The signal processor outputs the test waveform, which is used as the modulation waveform. The operating temperature of the fiber optic gyroscope is set to P preset temperature values. When the p-th preset temperature value is set, the p-th static test is performed on the fiber optic gyroscope.

[0032] Step C: Based on the zero-bias stability value obtained from the p-th static test, determine the modulation depth parameter β_p corresponding to the minimum zero-bias stability value when the operating temperature of the fiber optic gyroscope is set to the p-th preset temperature value;

[0033] Step D: Calculate the modulation depth β using the P modulation depth parameters β_1, ..., β_P obtained from the calculation, as well as the digital quantity of the D / A converter corresponding to the 2π phase of the modulation waveform;

[0034] Wherein, 1≤p≤P; P≥1; among the P preset temperature values, at least the room temperature operating temperature of the fiber optic gyroscope is included.

[0035] According to the above-described technical solution of this invention, it is only necessary to utilize existing equipment in the fiber optic gyroscope (e.g., signal processor, D / A converter, phase modulator), and obtain the zero-bias stability value by measuring the output of the fiber optic gyroscope, without the need for other experiments or oscilloscope measurement tools outside of the existing equipment. The method proposed in this invention is a direct modulation depth determination method, which is closely related to the zero-bias stability index of the fiber optic gyroscope, using the zero-bias stability of the fiber optic gyroscope as the evaluation standard for judging whether the modulation depth is appropriate. When P=1, the optimal modulation depth parameter is determined only based on the minimum zero-bias stability value corresponding to the room temperature operating temperature. When more preset temperature values ​​are used, the corresponding optimal modulation depth parameter is obtained for each preset temperature value. The modulation depth β determined by the modulation depth parameter obtained by combining multiple preset temperature values ​​can be applied to a temperature range larger than the room temperature operating temperature. In this invention, the phase modulator can be a Y-waveguide or a piezoelectric ceramic.

[0036] In the above technical solution:

[0037] In step A, when the time ranges are [0, β_t), [β_t, 2×β_t), ..., [N×β_t-β_t, N×β_t), the modulation depth parameters of the test waveform are β_0, β_0+β_b, ..., β_0+N×β_b-β_b, respectively; the value range of β_b is [20, 100].

[0038] In step B, when performing the p-th static test on the fiber optic gyroscope, the test duration is N×β_t.

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

[0040] Step C1: In the p-th static test, calculate the zero-bias stability values ​​of the 1st time period, the 2nd time period, ..., the Nth time period, and arrange them in chronological order to form the first data sequence, where N is the number of preset time periods, each time period constitutes the test duration, and the duration of each time period is the preset duration β_t.

[0041] Step C2: Fit the zero-bias stability values ​​of the N time periods obtained in Step C1 to obtain the fitting results representing the relationship between the modulation depth parameter and the zero-bias stability values;

[0042] Step C3: Based on the fitting results obtained in step C2, determine the modulation depth parameter β_p corresponding to the minimum zero bias stability value.

[0043] Preferably, in step C2, the fitting is a polynomial fitting.

[0044] In the above technical solution: In one embodiment, step C3 specifically involves: based on the relationship curve between the modulation depth parameter and the zero-bias stability value corresponding to the fitting result, taking the modulation depth parameter corresponding to the minimum zero-bias stability value in the relationship curve as β_p. In another embodiment, step C3 specifically includes the following steps C31, C32, and C33.

[0045] Step C31: Perform interpolation based on the fitting results obtained in step C2, thereby expanding the first data sequence containing N data points into a second data sequence containing N×β_b data points. The number of interpolated data points between two adjacent data points in the first data sequence and the number of interpolated data points after the Nth data point in the first data sequence are both β_b-1.

[0046] Step C32: For the second data sequence obtained in step C31, take the index corresponding to the minimum value (i.e. the minimum zero-bias stability value) in the second data sequence as the value of Num_p;

[0047] Step C33: Calculate β_p using β_p = β_0 + Num_p.

[0048] The applicant's research revealed that when searching for the optimal modulation depth parameter corresponding to a preset temperature value with the goal of minimizing the zero-bias stability value, it is necessary to gradually increase the modulation depth parameter with a certain preset step size. The optimal modulation depth parameter is determined by comparing the zero-bias stability values ​​corresponding to each modulation depth parameter. However, this approach has several problems: if the preset step size is set too small (e.g., the modulation depth parameter increases by 1 each time), a certain amount of time is required to collect data after each adjustment to ensure the calculated zero-bias stability of the modulation depth parameter. This results in a significant computational burden and requires a substantial amount of time to obtain the zero-bias stability values ​​for each modulation depth parameter. Conversely, if the preset step size is set too large, the distance between two adjacent modulation depth parameters becomes too large, significantly affecting the accuracy of determining the optimal modulation depth parameter.

[0049] To address the aforementioned issues, in the technical solution of this application, the value range of β_b is [20, 100]. This setting avoids the problems of long testing time and large computational load caused by excessively small step sizes. After fitting the zero-bias stability values ​​of N modulation depth parameters β_0, β_0+β_b, ..., β_0+N×β_b-β_b corresponding to N time periods, the difference is calculated based on the fitting results. The resulting second data sequence containing N×β_b data points reflects the change in the zero-bias stability value corresponding to the modulation depth parameter that gradually changes from the initial value β_0. The index of the minimum value in the second data sequence is taken as the value of Num_p, and added to the initial value β_0, the optimal modulation depth parameter β_p is obtained. Compared with the scheme with excessively small step sizes, the method of this application significantly reduces testing time and computational load, and compared with the scheme with excessively large step sizes, it can achieve better accuracy in determining the optimal modulation depth parameter.

[0050] In the above technical solution, in step C2, the fitting is a polynomial fitting.

[0051] In the above technical solution, the specific method for calculating the modulation depth β in step D is as follows:

[0052] β=2×π×(β_1+β_2+……+β_P) / (P×M);

[0053] M is the digital value of the D / A converter corresponding to the 2π phase of the modulation waveform.

[0054] In the above technical solution, the value range of β_0 is |β_0-M / 4|≤5%; the value range of β_0+N×β_b is β_0+N×β_b≤M / 2; M is the digital quantity of the D / A converter corresponding to the 2π phase of the modulation waveform. In this solution, the absolute value of the difference between β_0 and M / 4 is set to be no greater than 5%.

[0055] During their research, the applicant discovered that the range of values ​​for the modulation depth parameter corresponds to the range of digital values ​​within the modulation depth range [π / 2, π]. Through the aforementioned settings, the modulation depth parameter can be adjusted within the corresponding digital value range.

[0056] In the above technical solution, M=32768, the value range of β_0 is [7000, 9000], the value range of N is [100, 200], and the value range of β_0+N×β_b is [14000, 16384]. Through these settings, the modulation depth parameter can be adjusted within the corresponding digital range.

[0057] In the above technical solution, the modulation waveform is a square wave.

[0058] In the above technical solution, the value range of β_t is [300s, 800s].

[0059] In the above technical solution, P≥3; among the P preset temperature values, at least the room temperature operating temperature, minimum operating temperature, and maximum operating temperature of the fiber optic gyroscope are included.

[0060] With the above settings, the minimum operating temperature, normal operating temperature, and maximum operating temperature are used as three different preset temperature values. Compared with the scheme that only considers the normal operating temperature, the modulation depth β determined by the modulation depth parameter obtained by combining multiple preset temperature values ​​can be applied to a wider temperature range than the normal operating temperature.

[0061] According to the same inventive concept, the present invention also provides an estimation apparatus for the modulation depth of a fiber optic gyroscope, including a computer device or processor; said computer device or processor is configured or programmed to perform the steps of the determination method described above.

[0062] The advantages and positive effects of this invention are: This invention is based on existing fiber optic gyroscope products themselves, without the need for other external experimental conditions. The modulation depth can be directly obtained through the modulation depth parameter in the gyroscope software, and it is suitable for open-loop or closed-loop fiber optic gyroscopes with DSP or FPGA as the processing core. Attached Figure Description

[0063] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0064] Figure 1 This is a schematic diagram of the steps in the method for determining the modulation depth of an optical fiber gyroscope in Embodiment 1 of the present invention.

[0065] Figure 2 This is a schematic diagram showing the change of modulation depth parameter over time in Embodiment 1 of the present invention. Detailed Implementation

[0066] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0067] In view of the limitations of current modulation depth determination methods, this invention proposes a direct method for determining modulation depth that is closely related to the zero-bias stability index of fiber optic gyroscopes.

[0068] This invention is a software implementation method based on gyroscope signal processing software, applicable to open-loop or closed-loop fiber optic gyroscopes using DSP or FPGA as the processing core. This invention is based on the fiber optic gyroscope product itself, without requiring external experimental conditions; the modulation depth can be directly obtained from the modulation depth parameter in the gyroscope software. The modulation depth parameter is obtained through piecewise calculation of zero-bias stability, polynomial fitting, interpolation, and determination of the position of the minimum zero-bias stability value in the sequence. This invention obtains the modulation depth parameters at the product's operating points of normal temperature, low temperature, and high temperature, and uses the average of the three modulation parameters as the final determined modulation depth parameter.

[0069] Example 1

[0070] like Figure 1 As shown, the method for determining the modulation depth of an optical fiber gyroscope in Embodiment 1 of the present invention includes the following steps:

[0071] a. Determine the digital quantity M corresponding to the 2π phase in the digital signal processing process based on the D / A bit depth used by the gyroscope.

[0072] b. The modulation depth parameter has a corresponding relationship with the digital quantity corresponding to the 2π phase, and is represented by digital quantity.

[0073] c. During the modulation depth determination process, the initial value of the modulation depth parameter β_0 is set, the modulation depth increment step value (i.e., the preset step value β_b) is set, and the modulation depth increment time length β_t is set.

[0074] d. Design the gyroscope signal processing software. The difference from the conventional design is that the modulation depth parameter is not set to a fixed value, but rather the initial value of the modulation depth parameter is set to β_0. At the same time, two parameters, β_b and β_t, are added so that β_0 increases by β_b every β_t (unit of seconds).

[0075] e. Download the completed gyroscope signal processing software into the gyroscope.

[0076] f. Perform a static test on the gyroscope at room temperature.

[0077] g. The test duration is N×β_t, with one test data point per second, for a total of N×β_t test data points.

[0078] h. Divide the test data into segments according to the time length β_t, and calculate the zero-bias stability (in ° / h) for each segment, obtaining N zero-bias stability values, which are arranged in sequence according to the test time. The zero-bias stability values ​​of the first time segment, the second time segment, ..., the Nth time segment are B_(p,1), B_(p,2), ..., B_(p,N), respectively.

[0079] i. Perform polynomial fitting and interpolation on the N zero-biased stability values ​​to expand them into a data sequence of length N×β_b, i.e., {B_(p,1), ..., B_(p,2), ..., B_(p,N), ...}, where the number of data between B_(p,1) and B_(p,2), the number of data between B_(p,2) and B_(p,3), ..., the number of data between B_(p,N-2) and B_(p,N-1), and the number of data after B_(p,N) are all β_b-1.

[0080] j. Select the sequence number Num_p corresponding to the minimum value of the zero-bias stability of the N×β_b length. Num_p is the Num_pth data in the corresponding N×β_b data sequence.

[0081] k. Calculate the modulation depth parameter in the gyroscope software using the formula β_chang=β_0+Num_p, denoted as β_chang.

[0082] l. Under the product's lowest operating temperature T_di, the gyroscope is subjected to static testing using the same method as steps g to k to obtain the modulation depth parameter β_di under low-temperature operating conditions.

[0083] m. Under the product's highest operating temperature T_gao, the gyroscope undergoes static testing using the same method as steps g to k to obtain the modulation depth parameter β_gao under low-temperature operating conditions. Steps l and m are not sequential and can be performed simultaneously.

[0084] n. Calculate the average value of the three obtained modulation depth parameters β_chang, β_di, and β_gao. The average value is rounded down to obtain the modulation depth parameter, denoted as β. The modulation depth value is obtained by calculating the value using the formula 2×π×β / M.

[0085] This invention is based on digital processing software for fiber optic gyroscopes, unifying the modulation depth determination method with the fiber optic gyroscope's operating process. It uses the zero-bias stability of the fiber optic gyroscope as the evaluation criterion for judging the appropriateness of the modulation depth, providing a direct method for obtaining the modulation depth. The obtained modulation depth value can be directly embedded into the gyroscope parameters. The performance of the fiber optic gyroscope and phase modulator is related to the operating temperature; the modulation depth of the gyroscope varies slightly under different operating temperature environments. The optimal modulation depth parameter is not entirely the same at different operating temperatures. This solution calculates the average modulation depth at different temperatures to ensure that the gyroscope's modulation depth parameters can better adapt to the entire operating range, thereby improving the gyroscope's zero-bias stability across the entire operating temperature range. Furthermore, the applicant found that the variation in the modulation depth parameter corresponding to the minimum zero-bias stability of the same gyroscope product is not significant under high temperature, low temperature, and normal temperature environments. Therefore, averaging the values ​​can take into account the entire operating temperature range of the gyroscope.

[0086] The invention is illustrated below with an example. The gyroscope uses an FPGA as the signal processing core, and the digital-to-analog converter (D / A) has 16 bits. The digital quantity corresponding to the 2π phase is M=32768. The modulation wave uses square wave modulation. Based on the above conditions, the gyroscope digital processing software is designed. The initial value of the modulation depth parameter is set to β_0=8000, the modulation depth increment step value is β_b=50, and the modulation depth increment time length is β_t=500s. During software operation, the modulation depth starts from the initial value of 8000, and increases by 50 every 500s, as follows. Figure 2 As shown. Download the designed software into the gyroscope.

[0087] The digital values ​​corresponding to phases π / 4, π / 2, 3π / 4, 7π / 8, π, and 2π are 4096, 8192, 12288, 14336, 16384, and 32768, respectively.

[0088] In this embodiment 1, P=3, and the first, second, and third preset temperature values ​​are the room temperature operating temperature β_chang, the minimum operating temperature β_di, and the maximum operating temperature β_gao of the fiber optic gyroscope, respectively. N=140. In this embodiment, the room temperature operating temperature of the gyroscope is 25°C. In practice, the room temperature operating temperature of the gyroscope may vary depending on the working environment, and those skilled in the art understand how to determine the room temperature operating temperature of the gyroscope.

[0089] In this embodiment, when performing a room-temperature static test on the gyroscope, one gyroscope output data point is tested per second, with a test duration of 140 × β_t = 70000 s, resulting in a total of 70000 test data points. The test data is divided into 140 segments according to β_t = 500 s, and the zero-bias stability (unit: ° / h) is calculated for each segment, yielding 140 zero-bias stability values. Polynomial fitting and interpolation are performed on the obtained 140 zero-bias stability values ​​(interpolation coefficient is 50, i.e., the number of interpolated data is 50 times the number of original data), resulting in 7000 zero-bias stability values. The position number Num_1 of the minimum zero-bias stability value in the sequence is determined (assuming the first number at the beginning is 1, and so on, with the last test data point being 7000). The position number corresponding to the minimum value of zero bias stability is 6543; the modulation depth parameter is calculated using the formula β_1=β_0+Num_1=8000+6543=14543, and the modulation depth parameter β_chang=14543 is obtained. Here, β_chang is β_1.

[0090] In calculating the zero-bias stability of 500 data points for each segment, the data is smoothed every 10 seconds, that is, the mean is calculated for every 10 data points to obtain 50 data points for that segment, and then the zero-bias stability of that segment is calculated using the 50 data points.

[0091] The gyroscope's minimum operating temperature is -40℃. Static testing was conducted at -40℃, with one data point per second for a duration of 140 × β_t = 70000 seconds, resulting in 70000 data points. The test data was divided into 140 segments at β_t = 500 seconds. Zero-bias stability (unit: ° / h (10s smoothing)) was calculated for each segment, yielding 140 zero-bias stability values. Polynomial fitting and interpolation were then performed on these 140 zero-bias stability values. With a coefficient of 50, 7000 zero-bias stability values ​​are obtained; the position number Num_2 of the minimum zero-bias stability value in the sequence is determined (assuming the first number at the beginning is 1, and so on, with the last test data being 7000); the position number corresponding to the minimum zero-bias stability value is 6530; the modulation depth parameter is calculated using the formula β_2=β_0+Num_2=8000+6530=14530, and the modulation depth parameter β_di=14530 is obtained, where β_di is β_2.

[0092] The gyroscope's maximum operating temperature is 60℃. Static testing was conducted at 60℃, with one data point per second for a duration of 140 × β_t = 70000 seconds, resulting in 70000 data points. The data points were divided into 140 segments with β_t = 500 seconds. The zero-bias stability (unit: ° / h (10s smoothing)) was calculated for each segment, yielding 140 zero-bias stability values. Polynomial fitting and interpolation (interpolation coefficient 50) were applied to these 140 values, resulting in 7000 zero-bias stability values. The position number Num_3 of the minimum zero-bias stability value in the sequence was determined (starting with the first data point as 1, and so on, with the last data point being 7000). The position number corresponding to the minimum zero-bias stability value is 6555. The modulation depth parameter is calculated using the formula β_3=β_0+Num_p=8000+6555=14555, and the modulation depth parameter β_gao=14555 is obtained. Here, β_gao is β_3.

[0093] The three modulation depth parameters 14543, 14530, and 14555 are obtained from the normal temperature operating point, low temperature operating point, and high temperature operating point. The average value and rounding result is 14542. Combining this with the digital quantity M corresponding to the 2π phase being 32768, the corresponding modulation depth is β = 2 × π × (β_1 + β_2 + ... + β_P) / (P × M) = (14542 / 32768) × 2π = 0.88757π.

[0094] Example 2

[0095] The main difference between Example 2 and Example 1 is that P=1, meaning that only the room temperature operating temperature of the fiber optic gyroscope is used as the preset temperature value. The modulation depth parameter corresponding to the minimum zero-bias stability value at the calculated room temperature is the optimal modulation depth parameter (i.e., β_p).

[0096] Example 3

[0097] The main difference between Example 3 and Example 1 is that steps i, j, and k are replaced by: taking the modulation depth parameter corresponding to the minimum zero-bias stability value in the curve of the relationship between the modulation depth parameter and the zero-bias stability value corresponding to the fitting result as β_p.

[0098] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0099] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention should still fall within the scope of the present invention. After reading this invention, those skilled in the art will understand that various equivalent modifications to the present invention fall within the scope defined by the appended claims. Unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

Claims

1. A method for determining the modulation depth of a fiber optic gyroscope, the fiber optic gyroscope comprising a signal processor for outputting a modulated waveform, a D / A converter for receiving the modulated waveform, and a phase modulator, wherein the signal processor, the D / A converter, and the phase modulator are electrically connected in sequence, characterized in that, The determination method includes the following steps: Step A: Construct a test waveform, wherein the modulation depth parameter corresponding to the start time of the test waveform is a preset initial value β_0 of the modulation depth parameter, the modulation depth parameter corresponding to the test waveform increases stepwise with time, and the increment of the modulation depth parameter is a preset step size value β_b; Step B: The signal processor outputs the test waveform, which is used as the modulation waveform. The operating temperature of the fiber optic gyroscope is set to P preset temperature values. When the p-th preset temperature value is set, the p-th static test is performed on the fiber optic gyroscope. Step C: Based on the zero-bias stability value obtained from the p-th static test, determine the modulation depth parameter β_p corresponding to the minimum zero-bias stability value when the operating temperature of the fiber optic gyroscope is set to the p-th preset temperature value; Step D: Calculate the modulation depth β using the P modulation depth parameters β_1, ..., β_P obtained from the calculation, as well as the digital quantity of the D / A converter corresponding to the 2π phase of the modulation waveform; Wherein, 1≤p≤P; P≥1; among the P preset temperature values, at least the room temperature operating temperature of the fiber optic gyroscope is included; In step D, the specific method for calculating the modulation depth β is as follows: β=2×π×(β_1+β_2+……+β_P) / (P×M); M is the digital value of the D / A converter corresponding to the 2π phase of the modulation waveform.

2. The determination method according to claim 1, characterized in that, In step A, when the time ranges are [0, β_t), [β_t, 2×β_t), ..., [N×β_t-β_t, N×β_t), the modulation depth parameters of the test waveform are β_0, β_0+β_b, ..., β_0+N×β_b-β_b, respectively; the value range of β_b is [20, 100]. In step B, when performing the p-th static test on the fiber optic gyroscope, the test duration is N×β_t. The specific method for step C is as follows: Step C1: In the p-th static test, calculate the zero-bias stability values ​​of the 1st time period, the 2nd time period, ..., the Nth time period, and arrange them in chronological order to form the first data sequence, where N is the number of preset time periods, each time period constitutes the test duration, and the duration of each time period is the preset duration β_t. Step C2: Fit the zero-bias stability values ​​of the N time periods obtained in Step C1 to obtain the fitting results representing the relationship between the modulation depth parameter and the zero-bias stability values; Step C3: Based on the fitting results obtained in step C2, determine the modulation depth parameter β_p corresponding to the minimum zero bias stability value.

3. The determination method according to claim 2, characterized in that, In step C2, the fitting is a polynomial fitting.

4. The determination method according to claim 2, characterized in that, Step C3 specifically involves: based on the relationship curve between the modulation depth parameter and the zero-bias stability value corresponding to the fitting result, taking the modulation depth parameter corresponding to the minimum zero-bias stability value in the relationship curve as β_p; or Step C3 specifically includes the following steps: C31, C32, and C33. Step C31: Perform interpolation based on the fitting results obtained in step C2, thereby expanding the first data sequence containing N data points into a second data sequence containing N×β_b data points. The number of interpolated data points between two adjacent data points in the first data sequence and the number of interpolated data points after the Nth data point in the first data sequence are both β_b-1. Step C32: For the second data sequence obtained in step C31, take the index corresponding to the minimum value in the second data sequence as the value of Num_p; Step C33: Calculate β_p using β_p = β_0 + Num_p.

5. The determining method according to any one of claims 1-4, characterized in that, P≥3; among the P preset temperature values, at least the room temperature operating temperature, minimum operating temperature, and maximum operating temperature of the fiber optic gyroscope are included.

6. The determining method according to any one of claims 1-4, characterized in that, The modulation waveform is a square wave.

7. The determining method according to any one of claims 1-4, characterized in that, The range of values ​​for β_0 is |β_0-M / 4|≤5%; The value range of β_0+N×β_b is β_0+N×β_b≤M / 2; M is the digital quantity of the D / A converter corresponding to the 2π phase of the modulation waveform.

8. The determining method according to any one of claims 1-4, characterized in that, M=32768, the value range of β_0 is [7000, 9000], the value range of N is [100, 200], and the value range of β_0+N×β_b is [14000, 16384].

9. The determining method according to any one of claims 1-4, characterized in that, The value range of β_t is [300s, 800s].

10. A device for estimating the modulation depth of a fiber optic gyroscope, characterized in that, Includes computer equipment or processors; The computer device or processor is configured or programmed to perform the steps of the determining method according to any one of claims 1-9.

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