Method for reducing scale factor error of fiber optic gyroscope, processing circuit and fiber optic gyroscope

Abstract

This invention relates to fiber optic gyroscopes, specifically to a method, processing circuit, and fiber optic gyroscope for reducing scaling factor error. It addresses the shortcomings of fiber optic gyroscopes, such as fiber ring aging during prolonged operation, which alters the scaling factor compensation model across the entire temperature range, leading to decreased long-term scaling factor stability and limiting gyroscope applications. The method for reducing scaling factor error involves using a pulse detection circuit between the PIN-FET photodetector output and the FPGA input to measure transit time error. This error is then used to correct the modulation time, ensuring the fiber ring length is under closed-loop control.

Description

Technical Field

[0001] This invention relates to fiber optic gyroscopes, and more specifically to a method, processing circuit, and fiber optic gyroscope for reducing the scaling factor error of a fiber optic gyroscope. Background Technology

[0002] Reference Figure 1 The digital closed-loop interferometric fiber optic gyroscope consists of a light source 011, an optical path, and a processing circuit. The light source 011 primarily provides the fiber optic gyroscope with the appropriate optical signal required to generate the Sagnac effect, as well as high stable output optical power, enabling the acquisition of an interference signal with a high signal-to-noise ratio. The optical path includes a coupler 08, a Y-waveguide 09, and a fiber optic loop 010. Its main function is to obtain the phase difference of the interference signal through the Sagnac effect in the closed optical path. The processing circuit primarily handles weak signal conditioning, the implementation of the closed-loop algorithm and corresponding modulation of the Y-waveguide 09, and the calculation and output of the angular rate.

[0003] The processing circuit of the fiber optic gyroscope includes a signal demodulation unit, a core control unit, a signal modulation and feedback unit, and a serial communication interface. The signal demodulation unit includes a preamplifier filter 01 and an analog-to-digital converter 02 connected in sequence between their output and input. The core control unit includes an FPGA 03. The signal modulation and feedback unit includes a digital-to-analog converter 04 and a post-amplifier 05 connected in sequence between their output and input.

[0004] When an angular rate is input to the sensitive direction of the fiber optic gyroscope, error information related to the angular rate is superimposed on the output optical signal of the fiber optic gyroscope. The output optical signal of the fiber optic gyroscope is converted into a voltage signal by the PIN-FET photodetector 07, conditioned by the preamplifier filter 01, and then converted into a digital signal by the analog-to-digital converter 02 before being sent to the FPGA 03. On one hand, the FPGA 03 acquires the digital signal and calculates the digital quantity of the input angular rate error signal. After digitally modulating the angular rate information, the feedback control quantity is output to the digital-to-analog converter 04 through the first output terminal of the FPGA 03. After passing through the post-amplifier 05, it is output to the Y-waveguide 09 of the fiber optic gyroscope, adjusting the phase error signal generated by the input angular rate to the original operating point to form a closed-loop feedback. On the other hand, the FPGA 03 digitally demodulates the input error signal to obtain the gyroscope-sensitive angular rate output data. The gyroscope data is output through the serial communication circuit 06 via the second output terminal of the FPGA 03 according to the protocol.

[0005] Based on the fundamental principles of fiber optic gyroscopes, the scaling factor K of a fiber optic gyroscope is as follows:

[0006]

[0007] In the formula, L is the length of the fiber optic loop 010, D is the equivalent diameter of the fiber optic loop 010, λ is the wavelength of the fiber optic gyroscope, and c is the speed of light in the fiber optic cable.

[0008] As can be seen from the above formula, changes in the fiber optic loop length lead to changes in the scaling factor of the fiber optic gyroscope. Across the entire temperature range, changes in the fiber optic loop length cause the scaling factor error to exceed 1000 ppm. In engineering practice, the scaling factor of the fiber optic gyroscope is typically collected across the entire temperature range. A compensation model is established by comparing the measured values ​​from temperature sensors with the changes in the scaling factor over the entire temperature range to reduce the full-temperature scaling factor error. However, with prolonged operation, the fiber optic loop ages, inevitably altering the scaling factor compensation model and leading to decreased long-term stability of the scaling factor, thus limiting the application of fiber optic gyroscopes. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of fiber optic gyroscopes, such as the aging of the fiber optic ring and changes in the compensation model of the scaling factor across the entire temperature range, which leads to a decrease in the long-term stability of the scaling factor and further limits the application of fiber optic gyroscopes. The invention provides a method, processing circuit, and fiber optic gyroscope for reducing the scaling factor error of fiber optic gyroscopes.

[0010] To address the shortcomings of the existing technology, the present invention provides the following technical solution:

[0011] A method for reducing the scaling factor error of a fiber optic gyroscope, characterized by the following steps:

[0012] Step 1: Optical signal modulation;

[0013] Modulation time T of FPGA m Adjustments are made to minimize the pulse width time A of the voltage signal output by the PIN-FET photodetector, thus obtaining the modulation time T. m (a);

[0014] Step 2: Measure the transit time error;

[0015] Step 2.1: Set up a pulse detection circuit between the output of the PIN-FET photodetector and the input of FPGA 03, set up interconnected direction-locked chips at the ports of FPGA (03), and set the modulation time of FPGA to T. m (a); a represents the number of measurements, a = 0;

[0016] Step 2.2: Input the voltage signal output by the PIN-FET photodetector into the pulse detection circuit to obtain the detection pulse width; measure the detection pulse width time A(a) and the interval time L(a) between the falling edge and rising edge of adjacent pulses through FPGA, where the detection pulse width time A(a) is the transit time error;

[0017] Step 3: Correct the modulation time;

[0018] By comparing T m The modulation time T of the FPGA is updated based on the magnitude of (a) and L(a) and whether A(a) is greater than 0. m (a) Correction of modulation time.

[0019] Furthermore, step 3 specifically includes:

[0020] Step 3.1, Compare T m The magnitudes of (a) and L(a);

[0021] If T m If (a) > L(a), then the modulation time is considered to be greater than the transit time. Let a = a + 1, and let T... m (a)=T m (a)-A(a);

[0022] If T m When (a) = L(a) and A(a) = 0, the modulation time is considered to be equal to the transit time. After setting a = a + 1, the modulation time T is maintained. m (a) Unchanged;

[0023] If T m If (a) = L(a) and A(b) > 0, then the modulation time is considered to be less than the transit time. Let a = a + 1, and let T... m (a) = T m (a)+A(a);

[0024] Step 3.2: Determine if 'a' is less than the preset number of measurements X. If yes, return to step 2.2; otherwise, proceed to step 3.3.

[0025] Step 3.3: Calculate T m (a) average T is calculated using FPGA (03) m The average value of (a) is used to update the modulation time of the FPGA to T. m (a) = AVG, return to step 2.2.

[0026] Furthermore, in step 1, the modulation time T of the FPGA m Before making adjustments, the following also applies:

[0027] Set the ambient temperature ET of the fiber optic gyroscope to ET. min And ET = kt + ET min Where k is the heating rate, t is time, and ET is the time interval. min Let ET be the minimum ambient temperature, where ET ∈ [-50, +85].

[0028] Furthermore, step 3 specifically includes:

[0029] Step 3.1, Compare T m The magnitudes of (a) and L(a) and whether A(a) is greater than 0;

[0030] If T m If (a) > L(a), then the modulation time is considered to be greater than the transit time. Let a = a + 1, and let T... m (a) = T m (a)-A(a);

[0031] If T m When (a) = L(a) and A(a) = 0, the modulation time is considered to be equal to the transit time. After setting a = a + 1, the modulation time T is maintained. m (a) Unchanged;

[0032] If T m If (a) = L(a) and A(a) > 0, then the modulation time is considered to be less than the transit time. Let a = a + 1, and let T... m (a) = T m (a)+A(a);

[0033] Step 3.2: Determine the real-time temperature ET real Is it less than +85? If yes, proceed to step 3.3; otherwise, proceed to step 3.5.

[0034] Step 3.3: Determine if 'a' is less than the preset number of measurements X. If yes, return to step 2.2; otherwise, proceed to step 3.4.

[0035] Step 3.4: Calculate T m (a) average ET real This is the real-time value of the ambient temperature ET of the fiber optic gyroscope;

[0036] T is calculated using FPGA. m The average value of (a) is used to control the PLL chip to update the modulation time of the FPGA by T. m (a) = AVG(ET) real ), and record AVG(ET) real ), return to step 2.2;

[0037] Step 3.5: Establish K(ET) based on the existing scaling factor K for different fiber optic gyroscopes at ambient temperatures ET. real ), and then combined with the AVG (ET) recorded in step 3.3 real The scaling factor error compensation model is established as follows:

[0038] K′=(A′*AVG(ET real )+B)×K(ET real )

[0039] A′ and B are both coefficients, determined by the least squares algorithm.

[0040] Meanwhile, the present invention also provides a processing circuit for reducing the scaling factor error of a fiber optic gyroscope, used to implement the above-mentioned method for reducing the scaling factor error of a fiber optic gyroscope, including an FPGA, a signal demodulation unit disposed at a first input terminal of the FPGA, a signal modulation and feedback unit disposed at a first output terminal of the FPGA, and a serial communication interface disposed at a second output terminal of the FPGA; the signal demodulation unit includes a preamplifier filter and an analog-to-digital converter connected in sequence to the output and input, and the signal modulation and feedback unit includes a digital-to-analog converter and a post-amplifier connected in sequence to the output and input;

[0041] Its special feature is that it also includes a pulse detection circuit located between the output of the PIN-FET photodetector of the fiber optic gyroscope and the input of the FPGA, as well as a phase-locked loop chip interconnected with the FPGA.

[0042] The present invention also provides a fiber optic gyroscope, which is characterized by employing the above-mentioned processing circuit for reducing the scaling factor error of the fiber optic gyroscope.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] (1) The present invention provides a method for reducing the scaling factor error of a fiber optic gyroscope. By setting a pulse detection circuit between the output end of the PIN-FET photodetector and the input end of the FPGA to measure the transit time error, and correcting the modulation time based on this, the fiber optic ring length is in a closed-loop control process, thereby eliminating the scaling factor error caused by the change in the length of the fiber optic ring under high and low temperature conditions, as well as the scaling factor error caused by the aging of the fiber optic ring, and further improving the long-term stability of the scaling factor.

[0045] (2) The present invention provides a method for reducing the scaling factor error of fiber optic gyroscopes by measuring the AVG (ET) over the entire temperature range. real ), and combined with K(ET) realA scaling factor error compensation model was established to address the issue that the scaling factor compensation model changes across the entire temperature range as the fiber optic ring ages due to prolonged operation of the fiber optic gyroscope. Attached Figure Description

[0046] Figure 1 A schematic diagram of a digital closed-loop interferometric fiber optic gyroscope;

[0047] Figure 2 The modulation time T of the fiber optic gyroscope m transit time T of the fiber optic gyroscope s Relationship diagram;

[0048] Figure 3 This is a flowchart of a first embodiment of a method for reducing the scaling factor error of a fiber optic gyroscope according to the present invention;

[0049] Figure 4 The diagram shows the structure of the processing circuit for reducing the scaling factor error of a fiber optic gyroscope according to Embodiment 1 and Embodiment 2 of the present invention applied to a fiber optic gyroscope.

[0050] The annotations in the attached figures are explained as follows:

[0051] 01-Preamplifier and filter; 02-Analog-to-digital converter; 03-FPGA; 04-Digital-to-analog converter; 05-Post-amplifier; 06-Serial communication circuit; 07-PIN-FET photodetector; 08-Coupled; 09-Y-waveguide; 010-Fiber optic ring; 011-Light source; 1-Pulse detection circuit; 2-Phase-locked loop chip. Detailed Implementation

[0052] The present invention will be further described below with reference to the accompanying drawings and exemplary embodiments.

[0053] Reference Figure 2 Modulation time T m transit time T of the fiber optic gyroscope s The relationship is as follows:

[0054]

[0055] L is the time interval between the falling edge and rising edge of an adjacent pulse.

[0056] Example 1

[0057] Reference Figure 3 A method for reducing the scaling factor error of a fiber optic gyroscope includes the following steps:

[0058] Step 1: Optical signal modulation;

[0059] Set the ambient temperature ET of the fiber optic gyroscope to ET. minAnd ET = kt + ET min Where k is the heating rate, t is time, and ET is the time interval. min The minimum ambient temperature ET, where ET∈[-50,+85];

[0060] Modulation time T of FPGA 03 m Adjustments are made to minimize the pulse width time A of the voltage signal output by the PIN-FET photodetector 07, thus obtaining the modulation time T. m (a);

[0061] Step 2: Measure the transit time error;

[0062] Step 2.1: Set up a pulse detection circuit 1 between the output of the PIN-FET photodetector 07 and the input of the FPGA 03. Set up an interconnected direction-locked chip 2 at the port of the FPGA 03, and set the modulation time of the FPGA 03 to T. m (a); a represents the number of measurements, a = 0;

[0063] Step 2.2: Input the voltage signal output by the PIN-FET photodetector 07 into the pulse detection circuit 1 to obtain the detection pulse width; measure the detection pulse width time A(a) and the interval time L(a) between the falling edge and rising edge of adjacent pulses through FPGA 03. The detection pulse width time A(a) is the transit time error.

[0064] The transit time is the time it takes for the optical signal to travel one revolution in the optical fiber loop 010.

[0065] Step 3: By comparing T m Based on the magnitudes of (a) and L(a) and whether A(a) is greater than 0, update the modulation time T of FPGA 03. m (a) Correction of modulation time is completed;

[0066] Step 3.1, Compare T m The magnitudes of (a) and L(a) and whether A(a) is greater than 0;

[0067] If T m If (a) > L(a), then the modulation time is considered to be greater than the transit time. Let a = a + 1, and let T... m (a) = T m (a)-A(a);

[0068] If T m When (a) = L(a) and A(a) = 0, the modulation time is considered to be equal to the transit time. After setting a = a + 1, maintain T m (a) Unchanged;

[0069] If T m If (a) = L(a) and A(a) > 0, then the modulation time is considered to be less than the transit time. Let a = a + 1, and let T... m (a) = T m (a)+A(a);

[0070] Step 3.2: Determine the real-time temperature ET real Is it less than +85? If yes, proceed to step 3.3; otherwise, proceed to step 3.5.

[0071] Step 3.3: Determine if 'a' is less than the preset number of measurements X. If yes, return to step 2.2; otherwise, proceed to step 3.4.

[0072] Step 3.4: Calculate T m (a) average ET real This is the real-time value of the ambient temperature ET of the fiber optic gyroscope;

[0073] T is calculated using FPGA 03 m The average value of (a) is used to control the PLL chip 2 to update the modulation time of FPGA 03 for T. m (a) = AVG(ET) real ), and record AVG(ET) real ), return to step 2.2;

[0074] Step 3.5: Establish K(ET) based on the existing scaling factor K for different fiber optic gyroscopes at ambient temperatures ET. real ), and then combined with the AVG (ET) recorded in step 3.3 real The scaling factor error compensation model is established as follows:

[0075] K′=(A′*AVG(ET real )+B)×K(ET real )

[0076] A′ and B are both coefficients, determined by the least squares algorithm.

[0077] Reference Figure 4 The present invention also discloses a processing circuit for reducing the scaling factor error of a fiber optic gyroscope, used to implement the above-mentioned method for reducing the scaling factor error of a fiber optic gyroscope; the fiber optic gyroscope processing circuit includes an FPGA 03, a signal demodulation unit disposed at the first input terminal of the FPGA 03, a signal modulation and feedback unit disposed at the first output terminal of the FPGA 03, a serial communication interface disposed at the second output terminal of the FPGA 03, as well as a pulse detection circuit and a phase-locked loop chip 2.

[0078] The signal demodulation unit includes a preamplifier filter 01 and an analog-to-digital converter 02 connected in sequence to the output and input. The input terminal of the preamplifier filter 01 is used to connect to the PIN-FET photodetector 07. The signal modulation and feedback unit includes a digital-to-analog converter 04 and a postamplifier 05 connected in sequence to the output and input. The output terminal of the postamplifier 05 is used to connect to the Y-waveguide 09.

[0079] In the fiber optic gyroscope processing circuit, the pulse detection circuit 1 is located between the output terminal of the PIN-FET photodetector 07 of the fiber optic gyroscope and the input terminal of the FPGA 03. The phase-locked chip 2 is interconnected with the FPGA 03 and is used to provide a clock signal for the FPGA 03.

[0080] Based on the above processing circuit, the present invention also discloses an optical fiber gyroscope employing the above-described processing circuit for reducing the scaling factor error of the optical fiber gyroscope.

[0081] Example 2

[0082] A method for reducing the scaling factor error of a fiber optic gyroscope includes the following steps:

[0083] Step 1: Optical signal modulation;

[0084] Modulation time T of FPGA 03 m Adjustments are made to minimize the pulse width time A of the voltage signal output by the PIN-FET photodetector 07, thus obtaining the modulation time T. m (a);

[0085] Step 2: Measure the transit time error;

[0086] Step 2.1: Set up a pulse detection circuit 1 between the output of the PIN-FET photodetector 07 and the input of the FPGA 03. Set up an interconnected direction-locked chip 2 at the port of the FPGA 03, and set the modulation time of the FPGA 03 to T. m (a); a represents the number of measurements, a = 0;

[0087] Step 2.2: Input the voltage signal output by the PIN-FET photodetector 07 into the pulse detection circuit 1 to obtain the detection pulse width; measure the detection pulse width time A(a) and the interval time L(a) between the falling edge and rising edge of adjacent pulses through FPGA 03. The detection pulse width time A(a) is the transit time error.

[0088] The transit time is the time it takes for the optical signal to travel one revolution in the optical fiber loop 010.

[0089] Step 3: By comparing T mBased on the magnitudes of (a) and L(a) and whether A(a) is greater than 0, update the modulation time T of FPGA 03. m (a) Correction of modulation time is completed;

[0090] Step 3.1, Compare T m The magnitudes of (a) and L(a) and whether A(a) is greater than 0;

[0091] If T m If (a) > L(a), then the modulation time is considered to be greater than the transit time. Let a = a + 1, and let T... m (a) = T m (a)-A(a);

[0092] If T m When (a) = L(a) and A(a) = 0, the modulation time is considered to be equal to the transit time. After setting a = a + 1, maintain T m (a) Unchanged;

[0093] If T m If (a) = L(a) and A(a) > 0, then the modulation time is considered to be less than the transit time. Let a = a + 1, and let T... m (a) = T m (a)+A(a);

[0094] Step 3.2: Determine if 'a' is less than the preset number of measurements X. If yes, return to step 2.2; otherwise, proceed to step 3.3.

[0095] Step 3.3: Calculate T m (a) average T is calculated using FPGA (03) m The average value of (a) is used to update the modulation time of FPGA(03) to T. m (a) = AVG, return to step 2.2.

Claims

1. A method for reducing the scaling factor error of a fiber optic gyroscope, characterized in that, Includes the following steps: Step 1: Optical signal modulation; Set the ambient temperature for the fiber optic gyroscope for ,and ;in For the heating rate, For time, For ambient temperature Minimum value, ; Modulation time of FPGA(03) Adjustments are made to change the pulse width time of the voltage signal output by the PIN-FET photodetector (07). Minimum, to obtain the modulation time ; Step 2: Measure the transit time error; Step 2.1: Set up a pulse detection circuit (1) between the output of the PIN-FET photodetector (07) and the input of the FPGA (03), set up interconnected direction-locked chips (2) at the ports of the FPGA (03), and set the modulation time of the FPGA (03) to be [value missing]. ; To measure the number of times, ; Step 2.2: Input the voltage signal output by the PIN-FET photodetector (07) into the pulse detection circuit (1) to obtain the detection pulse width; The detection pulse width time was obtained by FPGA (03). The time interval between the falling edge and rising edge of adjacent pulses The detection pulse width time This is for transit time error; Step 3: Correct the modulation time; By comparison and Size and If the value is greater than 0, update the modulation time of FPGA(03). This completes the correction of the modulation time; Step 3.1, Comparison and Size and Is it greater than 0? if Then it is assumed that the modulation time is greater than the transit time, let Afterwards, order ; if ,and Then, it is assumed that the modulation time equals the transit time, and let Then, maintain modulation time constant; if ,and If the modulation time is less than the transit time, then let Afterwards, order ; Step 3.2: Determine the real-time temperature Is it less than +85? If so, proceed to step 3.

3. Otherwise, proceed to step 3.5; Step 3.3, Judgment Is the number of measurements less than the preset number? If so, return to step 2.2; Otherwise, proceed to step 3.4; Step 3.4, calculate average ; The ambient temperature of the fiber optic gyroscope The real-time value; Calculated using FPGA (03) The average value is used to control the phase-locked loop chip (2) to update the modulation time of the FPGA (03). and record Return to step 2.2; Step 3.5: Based on the existing ambient temperature of different fiber optic gyroscopes Scale factor below Establish Combined with the records from step 3.4 The scaling factor error compensation model is established as follows: ； , All are coefficients, determined using the least squares algorithm.

2. A processing circuit for reducing the scaling factor error of a fiber optic gyroscope, used to implement the method for reducing the scaling factor error of a fiber optic gyroscope as described in claim 1, comprising an FPGA (03), a signal demodulation unit disposed at a first input terminal of the FPGA (03), a signal modulation and feedback unit disposed at a first output terminal of the FPGA (03), and a serial communication interface disposed at a second output terminal of the FPGA (03); the signal demodulation unit comprises a preamplifier filter (01) and an analog-to-digital converter (02) connected in sequence to the output and input, the input terminal of the preamplifier filter (01) being used to connect to a PIN-FET photodetector (07), the signal modulation and feedback unit comprising a digital-to-analog converter (04) and a post-amplifier (05) connected in sequence to the output and input, the output terminal of the post-amplifier (05) being used to connect to a Y-waveguide (09); Its features are: It also includes a pulse detection circuit (1) disposed between the output of the PIN-FET photodetector (07) of the fiber optic gyroscope and the second input of the FPGA (03), and a phase-locked loop chip (2) interconnected with the FPGA (03).

3. A fiber optic gyroscope, characterized in that: The processing circuit for reducing the scaling factor error of fiber optic gyroscopes as described in claim 2 is used.

Images