A closed-loop control method for fiber optic gyroscope based on segmented sampling filtering

Abstract

This paper proposes a closed-loop control method for a fiber optic gyroscope (FOG) based on segmented sampling filtering, which can reduce the noise of the FOG system and improve the system's signal-to-noise ratio. By focusing on internal closed-loop control within the gyro, the present invention can reduce the noise when the FOG measures angular motion and improve the signal-to-noise ratio of the output signal. This helps enhance the FOG's measurement accuracy and improves the closed-loop system's tracking and dynamic performance.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber optic gyroscopes, and in particular to a fiber optic gyroscope closed-loop control method based on segmented sampling filtering. Background Art

[0002] The control performance of a closed-loop fiber optic gyroscope system is an important parameter reflecting its dynamic characteristics. It not only reflects the system's tracking ability for angular velocity signals, angular acceleration signals, or complex mixed input signals, but can also be used to measure whether the control scheme of the designed fiber optic gyroscope system meets the requirements.

[0003] Currently, the digital closed-loop control scheme for fiber optic gyroscopes commercialized both domestically and internationally primarily utilizes proportional-integral control. A closed-loop fiber optic gyroscope system employing proportional-integral control is an absolutely stable system, but steady-state errors can occur when tracking ramped angular velocity signals, angular acceleration signals, or complex mixed input signals.

[0004] From an automatic control perspective, many control schemes offer far superior performance to proportional-integral control. However, because closed-loop fiber optic gyroscopes (FOGs) are weak signal detection systems, the Sagnac phase difference signal to be detected is very weak, resulting in a low signal-to-noise ratio (SNR). This signal is easily overwhelmed by optical and circuit noise, and the digital-to-analog conversion of the Sagnac phase difference signal suffers from dead-zone nonlinearity. Existing techniques involve adding filters to the gyroscope output to filter the output signal, but this approach suffers from poor real-time performance and filtering effectiveness, high production costs, and bulky gyroscopes. Summary of the Invention

[0005] In view of this, the present invention proposes a fiber optic gyroscope closed-loop control method based on segmented sampling filtering, which can reduce the noise of the fiber optic gyroscope system and improve the signal-to-noise ratio of the system.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] The present invention provides a closed-loop control method for a fiber optic gyroscope based on segmented sampling filtering, comprising the following steps:

[0008] The fiber optic gyroscope detects angular motion and outputs an optical phase signal; bias modulates and phase modulates the optical phase signal to obtain a modulated signal; performs photoelectric conversion on the modulated signal to obtain a photocurrent signal; amplifies the photocurrent signal to obtain an amplified voltage signal V0; performs A / D conversion on the voltage signal V0 to obtain a digital voltage signal D0; takes the high N bits of the digital voltage signal D0 and saves it as a signal Dh, and performs high-end filtering on the signal Dh; converts the signal Dh into a signal Vh through D / A conversion and outputs it, takes the difference between the voltage signal V0 and the signal Vh, amplifies the difference, and then performs A / D conversion to obtain DL, truncates the low N bits of DL, and right-shifts the truncated DL by N bits to obtain Dl; combines Dl and the high-end filtered Dh to obtain a filtered sampling signal Dc.

[0009] Among them, N is 8.

[0010] The voltage signal V0 is subtracted from the signal Vh, the difference is amplified 256 times, and then A / D conversion is performed to obtain DL.

[0011] When the signal Dh is subjected to high-band filtering, a low-pass filter having a frequency equal to the bandwidth of the fiber optic gyroscope is directly used to filter out the noise.

[0012] The photocurrent signal is pre-amplified to obtain an amplified voltage signal V0.

[0013] Beneficial effects:

[0014] 1. The present invention starts with the closed-loop control inside the gyroscope, which can reduce the noise when the fiber optic gyroscope measures angular motion and improve the signal-to-noise ratio of the output signal, which is beneficial to improving the measurement accuracy of the fiber optic gyroscope and the tracking performance and dynamic performance of the closed-loop system.

[0015] 2. In the present invention, the amplified voltage signal V0 is compared with the analog signal Vh converted from the digital signal and the difference is taken, which can filter out the temperature drift generated by some circuit components and the power supply noise, further reduce the noise when the fiber optic gyroscope measures angular motion, improve the signal-to-noise ratio of the output signal, and help improve the measurement accuracy of the fiber optic gyroscope.

[0016] 3. The present invention directly uses a low-pass filter with a frequency equal to the bandwidth of the fiber optic gyroscope to filter out noise. For DL, after the useful signal is amplified 256 times, it exists in the upper N bits. Therefore, the lower N bits of DL can be directly truncated to remove A / D conversion noise. The truncated DL is then right-shifted N bits to obtain D1. This has higher real-time performance and better filtering effect, reducing both production costs and the size of the gyroscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of the segmented sampling and filtering process of the present invention. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0019] The present invention provides a closed-loop control method for a fiber optic gyroscope based on segmented sampling filtering. The segmented sampling filtering consists of high-segment filtering and low-segment filtering, that is, segment processing is performed on the original data. The flow chart is as follows: Figure 1 As shown, the following steps are included:

[0020] Step 1: The fiber optic gyroscope detects angular motion and outputs an optical phase signal;

[0021] Step 2: Perform bias modulation and phase modulation on the optical phase signal to obtain a modulated signal;

[0022] Step 3: Perform photoelectric conversion on the modulated signal to obtain a photocurrent signal;

[0023] Step 4: Pre-amplify the photocurrent signal to obtain the amplified voltage signal V0;

[0024] Step 5: Perform A / D conversion on the voltage signal V0 to obtain a digital voltage signal D0;

[0025] Step 6: Take the high N bits of the digital voltage signal D0 and save them as signal Dh, and convert the high N bits of the digital signal Dh into signal Vh through D / A and output it; where N is a set value, which is 8 in this embodiment.

[0026] Step 7: Subtract the voltage signal V0 from the signal Vh, amplify the difference by 256 times, and then perform A / D conversion to obtain DL; wherein, the difference between V0 and Vh can filter out the temperature drift generated by some circuit components and power supply noise.

[0027] Step 8: Perform high-band filtering on the high-N-bit digital signal Dh. According to the physical motion characteristics, the useful signal with high amplitude must be low-frequency. The noise can be directly filtered out by using a low-pass filter with a frequency equal to the bandwidth of the fiber optic gyroscope.

[0028] Step 9: For DL, after being amplified 256 times, the useful signal is present in the upper N bits. Therefore, the lower N bits of DL can be directly truncated, that is, low-end filtering can be performed on DL to remove A / D conversion noise. The truncated DL is right-shifted N bits to obtain Dl.

[0029] Step 10: Combine D1 and the high-band filtered Dh to obtain the filtered sampling signal Dc.

[0030] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fiber optic gyroscope closed-loop control method based on segmented sampling filtering, characterized in that: The steps include: The fiber optic gyroscope detects angular motion and outputs an optical phase signal; bias modulates and phase modulates the optical phase signal to obtain a modulated signal; performs photoelectric conversion on the modulated signal to obtain a photocurrent signal; amplifies the photocurrent signal to obtain an amplified voltage signal V0; performs A / D conversion on the voltage signal V0 to obtain a digital voltage signal D0; takes the high N bits of the digital voltage signal D0 and saves it as a signal Dh, and performs high-end filtering on the signal Dh; converts the signal Dh into a signal Vh through D / A conversion and outputs it, takes the difference between the voltage signal V0 and the signal Vh, amplifies the difference, and then performs A / D conversion to obtain DL, truncates the low N bits of DL, and right-shifts the truncated DL by N bits to obtain Dl; combines Dl and the high-end filtered Dh to obtain a filtered sampling signal Dc.

2. The method according to claim 1, wherein N is 8.

3. The method according to claim 1 or 2, wherein: The voltage signal V0 is subtracted from the signal Vh, the difference is amplified 256 times, and then A / D conversion is performed to obtain DL.

4. The method according to claim 1, wherein When performing high-band filtering on the signal Dh, a low-pass filter with a frequency equal to the bandwidth of the fiber optic gyroscope is directly used to filter out the noise.

5. The method according to claim 1, 2 or 4, characterized in that The photocurrent signal is pre-amplified to obtain an amplified voltage signal V0.

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