Self-calibration method of fiber optic gyroscope and fiber optic gyroscope

Abstract

The present invention provides a self-calibration method for a fiber optic gyroscope and a fiber optic gyroscope. The self-calibration method includes applying a calibration signal to an optical phase modulator; performing time-series demodulation on a signal collected by a light detector to obtain gyro outputs in the first and second half-cycles of a calibration state; calculating a calibrated scale factor; calculating a zero-position error caused by scale factor drift and a primary calibration gyro output for scale factor calibration; calculating a secondary calibration gyro output for zero-position calibration based on the time-series demodulation result; and calculating the gyro output after the secondary calibration. A calibration state is introduced into the fiber optic gyroscope signal processing. In the calibration state, a periodic calibration signal is output and loaded onto a phase modulator to simulate the positive and negative rotational speeds of the gyroscope. The gyro zero bias and scale factor are adjusted through calibration calculations.

Description

Technical Field

[0001] The invention belongs to the technical field of optical gyroscopes, and in particular relates to a self-calibration method of a fiber optic gyroscope and the fiber optic gyroscope. Background Art

[0002] After more than 40 years of development, the performance of interferometric fiber optic gyroscopes has become increasingly mature. The measurement accuracy has increased from dozens of times the Earth's rotation rate to better than 0.0001° / h. Its application scope covers sea, land, air, and space. It has been widely used not only in high-performance navigation, guidance and control such as weapon navigation, aerospace, and radar, but also in civil aircraft, car navigation systems and camera stabilizers.

[0003] Bias stability and scale factor are key performance indicators for gyroscopes. In conventional fiber optic gyros, the temperature-induced nonreciprocal bias increases significantly with increasing fiber length. Furthermore, due to inconsistent winding and adhesive curing processes, the stress within the fiber loop is difficult to effectively control. Consequently, the gyroscope output is poorly consistent with ambient temperature variations, making it difficult to compensate for the full-temperature bias and scale factor of the gyroscope, severely limiting its yield. The "three-self" inertial navigation system significantly reduces inherent zero-position error and scale factor error at the gyro system level. However, for miniaturized, low-cost integrated fiber optic gyros, the internal space within the gyro itself is insufficient to accommodate devices such as a turntable. Furthermore, adding rotating components further degrades the gyroscope's vibration resistance and limits its environmental adaptability. Therefore, within the limited space available, there is an urgent need for a method to improve the bias and scale factor performance of integrated fiber gyros without adding a turntable. Summary of the Invention

[0004] In response to the technical problem in the prior art that the full-temperature zero bias and scale factor of a fiber optic gyroscope are difficult to compensate, the present invention provides a self-calibration method for a fiber optic gyroscope and a fiber optic gyroscope. The self-calibration method introduces a calibration state into the fiber optic gyroscope signal processing. In the calibration state, a periodic calibration signal is output and loaded onto a phase modulator to simulate the positive and negative rotation speeds of the gyroscope. The gyroscope zero bias and scale factor are adjusted through calibration calculation.

[0005] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0006] The present invention provides a self-calibration method for a fiber optic gyroscope, comprising the following steps:

[0007] applying a calibration signal to the optical phase modulator;

[0008] Performing time-series demodulation on the signal collected by the optical detector to obtain the gyro output of the first half cycle and the second half cycle of the calibration state;

[0009] Calculate the calibrated scale factor;

[0010] Calculate the zero error due to scale factor drift and the primary calibration gyro output for scale factor calibration;

[0011] Calculate the secondary calibration gyro output for zero calibration based on the timing demodulation result;

[0012] Calculate the gyro output after two calibrations.

[0013] Furthermore, the calibration signal is a square wave signal, the frequency of the square wave signal is determined according to the length of the optical fiber loop and the delay time, and the amplitude of the square wave signal is

[0014]

[0015] Among them, Ω 校准 is the calibration speed, D is the length of the fiber loop, L is the diameter of the fiber loop, V 2π is the half-wave voltage of the phase modulator, λ is the operating wavelength, and c is the speed of light.

[0016] Furthermore, the frequency of the square wave signal ranges from 100 Hz to 1 kHz.

[0017] Furthermore, the method for calculating the calibrated scale factor is:

[0018]

[0019] Among them, D1 and D2 are the gyro outputs of the first half cycle and the second half cycle of the calibration state respectively, Ω 校准 To calibrate the speed.

[0020] Furthermore, the method for calculating the zero error caused by scale factor drift is:

[0021] ΔD=(K 校准 -K0)Ω0

[0022] Where K0 is the scale factor before calibration, Ω0 is the inherent zero position of the gyro before calibration;

[0023] The calculation method of the primary calibration gyro output is:

[0024] D 校准1 =D0+ΔD

[0025] Where D0 is the inherent output of the gyroscope before calibration.

[0026] Furthermore, the secondary calibration gyro output is

[0027] D 校准2 =D2+D1

[0028] Among them, D1 and D2 are the gyro outputs in the first half cycle and the second half cycle of the calibration state respectively;

[0029] The gyro output after the two calibrations is D 校准 =D0+D 校准1 +D 校准2 .

[0030] Furthermore, the self-calibration method is used for an interferometric fiber optic gyroscope that uses polarization-maintaining fiber, photonic crystal fiber, or optical waveguide as a sensitive component, and the fiber optic gyroscope is single-axis, dual-axis, or triple-axis.

[0031] The present invention also provides a fiber optic gyroscope that adopts the aforementioned self-calibration method.

[0032] Furthermore, the fiber optic gyroscope includes an optical path unit, a digital signal processing unit and a gyroscope signal detection circuit;

[0033] The optical path unit includes an optical device, an optical modulator and an optical fiber ring, wherein the optical device is used for light emission, coupling and light detection, the optical modulator is used for polarization, coupling and phase modulation, and the optical fiber ring is used for sensitivity to the Sagnac effect under rotation conditions;

[0034] The digital signal processing unit includes

[0035] A digital filter module is used to perform digital filtering on the output signal of the light detector and output a digital signal containing gyroscope speed information;

[0036] A signal demodulation module is used to demodulate the digital signal containing the gyroscope speed information to obtain the gyroscope speed signal;

[0037] PI control module, used to generate gyro speed closed-loop signal;

[0038] A modulation signal generating module is used to generate a modulation signal for measuring the rotational speed of the gyroscope;

[0039] A calibration signal generating module, used for generating a calibration signal;

[0040] The calibration state demodulation module is used to perform time-series demodulation on the digital signal containing the gyroscope speed information and calculate the calibrated scale factor based on the calibration speed and the demodulation result;

[0041] The scale factor calibration module is used to calculate the gyro output zero position after scale factor calibration according to the calibrated scale factor.

[0042] A zero position calibration module is used to calculate the gyro output zero position after zero position calibration based on the output timing demodulation result of the calibration state demodulation module, and calculate the gyro zero position through two calibration results;

[0043] The gyro signal detection circuit is used to collect light detector signals, control the light source to maintain constant temperature and current, control the closed loop of the optical phase modulator, and apply a calibration signal to the optical phase modulator.

[0044] Furthermore, the gyro signal detection circuit includes

[0045] The signal acquisition channel is used to process the output signal of the light detector and output it to the digital signal processing unit;

[0046] Drive temperature control channel, used to process the output signal of light source control module and control constant temperature and constant current of light source;

[0047] Closed-loop feedback channel, used to process the output signals of the modulation signal generation module and the PI control module, and output them to the optical phase modulator;

[0048] The calibration feedback channel is used to process the calibration signal generated by the calibration signal module and apply it to the optical phase modulator.

[0049] The beneficial effects of the present invention compared with the prior art are as follows:

[0050] By setting a calibration state within the integrated fiber optic gyroscope's signal processing algorithm, a periodic calibration signal is output during this state and loaded onto a phase modulator to simulate the gyroscope's positive and negative rotational speeds. The gyroscope's output during this state is then processed and a calibration algorithm is set in the compensation module based on parameters to adjust the gyroscope's bias and scale factor. This invention boasts the outstanding technical advantages of a simple principle and significant results, and is expected to significantly improve the performance of integrated fiber optic gyroscopes in terms of bias and scale factor. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings are included to provide a further understanding of the embodiments of the present invention, constitute a part of the specification, illustrate the embodiments of the present invention, and together with the description, explain the principles of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0052] Figure 1 A flowchart of a self-calibration method for a fiber optic gyroscope provided in a specific embodiment of the present invention;

[0053] Figure 2 A schematic diagram of the structure of an integrated fiber optic gyroscope with output self-calibration function provided by a specific embodiment of the present invention;

[0054] Figure 3 A gyroscope signal detection circuit structure is provided in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0055] Below specific embodiments of the present invention are described in detail. In the following description, for the purpose of explanation and not limitation, specific details are set forth to help fully understand the present invention. However, it will be apparent to those skilled in the art that other embodiments that have departed from these specific details can also be used to practice the present invention.

[0056] It should be noted that, in order to avoid obscuring the present invention due to unnecessary details, the accompanying drawings only show the device structure and / or processing steps closely related to the solutions of the present invention, while omitting other details that are not closely related to the present invention.

[0057] The present invention provides a self-calibration method for a fiber optic gyroscope. Figure 1 As shown, the following steps are included:

[0058] S1, applying a calibration signal to the optical phase modulator;

[0059] The calibration signal is specifically a square wave signal with frequency f and amplitude V. The frequency f is determined according to the length of the optical fiber loop and the delay time, and is preferably set to 100Hz to 1kHz. The amplitude V is determined according to different calibration speeds Ω. 校准 , fiber loop length D, diameter L, phase modulator half-wave voltage V 2π And the working wavelength λ is set to different parameters, specifically satisfying the following relationship:

[0060]

[0061] Where c is the speed of light.

[0062] S2, performing time-series demodulation on the signal collected by the light detector to obtain the gyro outputs of the first half cycle and the second half cycle of the calibration state, which are D1 and D2 respectively;

[0063] S3. Calculate the scale factor K after calibration 校准 , which is expressed as follows:

[0064]

[0065] Calculate the zero error D due to scale factor drift as follows:

[0066] ΔD=(K 校准 -K0)Ω0(3)

[0067] Where K0 is the scale factor before calibration, Ω0 is the inherent zero position of the gyro before calibration;

[0068] The gyro output after one calibration (scale factor calibration) after eliminating the zero error D is calculated as:

[0069] D 校准1 =D0+ΔD(4)

[0070] Where D0 is the inherent output of the gyroscope before calibration.

[0071] S4. Calculate the gyro output after secondary calibration (zero calibration) according to formula (5) based on the timing demodulation result, which is expressed as follows:

[0072] D 校准2 =D2+D1(5)

[0073] S5. The gyro zero position that has undergone two calibrations is taken as the final gyro zero position, which is expressed as follows:

[0074] D 校准 =D0+D 校准1 +D 校准2 (6)

[0075] The fiber optic gyroscope self-calibration method provided by the present invention is applicable to fiber optic gyros of traditional solutions, integrated fiber optic gyros based on different component integration solutions, and interferometric fiber optic gyros using polarization-maintaining fibers, photonic crystal fibers, optical waveguides, and other sensitive components. In addition, the present invention is not limited to the number of channels of the gyroscope (single-axis / dual-axis / triple-axis solutions), and is used for gyroscope zero-position calibration to improve the zero bias and scale factor performance of the fiber optic gyroscope.

[0076] The present invention also provides a self-calibration method for a fiber optic gyroscope and a fiber optic gyroscope, which include an optical path unit and a signal processing circuit, wherein the signal processing circuit includes a digital signal processing unit and a gyroscope signal detection circuit.

[0077] like Figure 2 As shown in Figure 1, the hardware structure of the fiber optic gyroscope mainly includes an optical path unit and a signal processing circuit. The optical path unit includes a "three-in-one" integrated optical device, an integrated optical modulator, and an optical fiber ring. The "three-in-one" integrated optical device realizes the functions of light emission, coupling, and light detection, the integrated optical modulator realizes the functions of polarization, coupling, and phase modulation, and the optical fiber ring realizes the Sagnac effect sensitivity under rotation conditions. The signal processing circuit structure includes an application-specific integrated circuit (ASIC) and supporting peripheral devices. The ASIC circuit integrates functional devices such as AD, DA, operational amplifier, and digital algorithm. The miniaturization of the detection circuit is achieved through the integration of multiple devices. The functions of the signal processing circuit include: (1) providing drive control of the light source to achieve stable light output; (2) loading the modulation signal to the optical phase modulator; (3) realizing the zero bias and scale factor self-calibration function; (4) realizing the speed signal detection through signal demodulation processing; (5) realizing the gyroscope data output.

[0078] like Figure 3As shown in the figure, in addition to integrating conventional modules of a traditional fiber optic gyroscope, such as the digital filtering module, signal demodulation module, PI control module, and modulation signal generation module, the digital signal processing unit also integrates a calibration signal generation module, a calibration state demodulation module, a standard factor calibration module, and a zero bias calibration module, a total of four modules directly related to the calibration of the fiber optic gyroscope. The specific functions are as follows:

[0079] The digital filter module is used to perform digital filtering on the digital signal converted from the output of the light detector and output a smoothed digital signal containing the gyroscope speed information.

[0080] The signal demodulation module is used to demodulate the digital signal containing the rotational speed information to obtain the gyro rotational speed signal.

[0081] The PI control module is used to generate a closed-loop signal of the gyro speed to stabilize the static operating point of the gyro.

[0082] The modulation signal generating module is used to generate the modulation signal for measuring the gyroscope rotation speed.

[0083] The calibration signal generating module is used to generate a calibration signal and apply it to the optical phase modulator through a calibration feedback channel.

[0084] The calibration state demodulation module is used to perform time-series demodulation on the output signal of the light detector to which the calibration signal is applied according to the input of the signal acquisition channel, that is, to perform time-series demodulation on the digital signal containing the gyroscope speed information, and to calculate the calibrated scale factor according to the calibration speed and the demodulation result.

[0085] The scale factor calibration module is used to calculate the gyro output zero position after a calibration (scale factor calibration) based on the scale factor calibrated by the calibration state demodulation module.

[0086] The zero position calibration module is used to calculate the gyro output zero position after the secondary calibration (zero position calibration) according to the output timing demodulation result of the calibration state demodulation module, and obtain the gyro calibration output through the output after two calibrations.

[0087] In addition, the digital signal processing unit also includes a light source control module and an adder. The light source control module is mainly used for constant temperature and constant current control of the light source, and the adder is used to superimpose the modulation signal and the closed-loop feedback signal.

[0088] like Figure 3 As shown in the figure, the gyro signal detection circuit is used to collect light detector signals, control the constant temperature and current of the light source, control the closed loop of the optical phase modulator, and apply a calibration signal to the optical phase modulator. The internal structure of the gyro signal detection circuit mainly includes four channels:

[0089] (1) Signal acquisition channel, including light detector, preamplifier and AD converter, amplifies and converts the weak voltage analog signal output by the light detector and outputs it to the digital signal processing unit.

[0090] (2) Driving temperature control channel, including a first branch consisting of a DA converter 1, a voltage amplifier 1, and a voltage-controlled current source 1, and a second branch consisting of a DA converter 2, a voltage amplifier 2, and a voltage-controlled current source 2. The first branch is used to convert, amplify, and convert the temperature control digital signal output by the light source control module to a voltage-current conversion, and output it to the light source temperature control interface of the "three-in-one" integrated optical device to perform constant temperature control of the light source; the second branch is used to convert, amplify, and convert the current digital signal output by the light source control module to a voltage-current conversion, and output it to the driving current control interface of the light source to perform constant current control.

[0091] (3) A closed-loop feedback channel, comprising a DA converter 3, a voltage amplifier 3, and an optical phase modulator, for converting and voltage-amplifying the closed-loop feedback digital signal output by the modulation signal module, and outputting the signal to the optical phase modulator to realize the phase closure caused by the optical path rotation;

[0092] (4) The calibration feedback channel includes a DA converter 4, a voltage amplifier 4, and an optical phase modulator, which is used to convert and voltage-amplify the calibration signal generated by the calibration signal module and apply it to the optical phase modulator to achieve signal loading at the optical phase modulator end after the calibration signal is generated.

[0093] Features described and / or illustrated above for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or used in place of features in other embodiments.

[0094] It should be emphasized that the term "include / comprises" when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps, components or combinations thereof.

[0095] The many features and advantages of these embodiments are apparent from this detailed description, and thus, the appended claims are intended to cover all such features and advantages of these embodiments that fall within the true spirit and scope thereof. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not intended that the embodiments of the invention be limited to the exact construction and operation illustrated and described, but rather that all suitable modifications and equivalents be covered within the scope thereof.

[0096] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

[0097] Parts of the present invention that are not described in detail are well known to those skilled in the art.

Claims

1. A self-calibration method for a fiber optic gyroscope, characterized in that: Includes the following steps applying a calibration signal to the optical phase modulator; Performing time-series demodulation on the signal collected by the optical detector to obtain the gyro output of the first half cycle and the second half cycle of the calibration state; Calculate the calibrated scale factor; Calculate the zero error due to scale factor drift and the primary calibration gyro output for scale factor calibration; Calculate the secondary calibration gyro output for zero calibration based on the timing demodulation result; Calculate the gyro output after two calibrations.

2. The self-calibration method of a fiber optic gyroscope according to claim 1, characterized in that: The calibration signal is a square wave signal, the frequency of which is determined according to the length of the optical fiber loop and the delay time, and the amplitude of the square wave signal is Among them, Ω 校准 To calibrate the rotation speed, D is the fiber loop length, L is the fiber loop diameter, V2π is the half-wave voltage of the phase modulator, λ is the operating wavelength, and c is the speed of light.

3. The self-calibration method of a fiber optic gyroscope according to claim 2, characterized in that: The frequency of the square wave signal ranges from 100 Hz to 1 kHz.

4. The self-calibration method of a fiber optic gyroscope according to claim 2, characterized in that: The method for calculating the calibrated scale factor is: Among them, D1 and D2 are the gyro outputs of the first half cycle and the second half cycle of the calibration state respectively, Ω 校准 To calibrate the speed.

5. The self-calibration method of the fiber optic gyroscope according to claim 4, characterized in that: The method for calculating the zero error caused by scale factor drift is: ΔD=(K 校准 -K0)Ω0 Where K0 is the scale factor before calibration, Ω0 is the inherent zero position of the gyro before calibration; The calculation method of the primary calibration gyro output is: D 校准1 =D0+ΔD Where D0 is the inherent output of the gyroscope before calibration.

6. The self-calibration method of a fiber optic gyroscope according to claim 5, characterized in that: The secondary calibration gyro output is D 校准2 =D2+D1 Among them, D1 and D2 are the gyro outputs in the first half cycle and the second half cycle of the calibration state respectively; The gyro output after the two calibrations is D 校准 =D 校准1 +D 校准2 .

7. The self-calibration method for a fiber optic gyroscope according to any one of claims 1 to 6, characterized in that: The self-calibration method is used for an interferometric fiber optic gyroscope that uses polarization-maintaining fiber, photonic crystal fiber or optical waveguide as a sensitive component, and the fiber optic gyroscope is single-axis, dual-axis or tri-axis.

8. A fiber optic gyroscope, characterized in that: The self-calibration method according to any one of claims 1 to 7 is adopted.

9. The fiber optic gyroscope according to claim 8, wherein: It includes an optical path unit, a digital signal processing unit and a gyro signal detection circuit; The optical path unit includes an optical device, an optical modulator and an optical fiber ring, wherein the optical device is used for light emission, coupling and light detection, the optical modulator is used for polarization, coupling and phase modulation, and the optical fiber ring is used for sensitivity to the Sagnac effect under rotation conditions; The digital signal processing unit includes A digital filter module is used to perform digital filtering on the output signal of the light detector and output a digital signal containing gyroscope speed information; A signal demodulation module is used to demodulate the digital signal containing the gyroscope speed information to obtain the gyroscope speed signal; PI control module, used to generate gyro speed closed-loop signal; A modulation signal generating module is used to generate a modulation signal for measuring the rotational speed of the gyroscope; A calibration signal generating module, used for generating a calibration signal; The calibration state demodulation module is used to perform time-series demodulation on the digital signal containing the gyroscope speed information and calculate the calibrated scale factor based on the calibration speed and the demodulation result; A scale factor calibration module, for calculating a primary calibration gyro output after scale factor calibration based on the calibrated scale factor; A zero-position calibration module is used to calculate the secondary calibration gyro output after zero-position calibration according to the output timing demodulation result of the calibration state demodulation module, and calculate the gyro output based on the two calibration results; The gyro signal detection circuit is used to collect light detector signals, control the light source to maintain constant temperature and current, control the closed loop of the optical phase modulator, and apply a calibration signal to the optical phase modulator.

10. The fiber optic gyroscope according to claim 9, wherein: The gyro signal detection circuit includes The signal acquisition channel is used to process the output signal of the light detector and output it to the digital signal processing unit; Drive temperature control channel, used to process the output signal of light source control module and control constant temperature and constant current of light source; Closed-loop feedback channel, used to process the output signals of the modulation signal generation module and the PI control module, and output them to the optical phase modulator; The calibration feedback channel is used to process the calibration signal generated by the calibration signal module and apply it to the optical phase modulator.

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