CN115112112A - Resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation and closed-loop control method thereof - Google Patents
Resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation and closed-loop control method thereof Download PDFInfo
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Abstract
The invention relates to the field of resonant fiber optic gyroscopes, in particular to a resonant fiber optic gyroscope based on optical rotation coil frequency compensation and a closed-loop control method thereof. The laser is respectively connected with a 50% 1 × 2 coupler I and a digital-analog interface, the 50% 1 × 2 coupler I is respectively connected with a phase modulator PM I and a phase modulator PM II, the phase modulator PM I is respectively connected with a circulator I, a photoelectric detector PD I and the digital-analog interface, and the phase modulator PM II is respectively connected with a circulator II, a photoelectric detector PD2 and the digital-analog interface; the circulator I is respectively connected with the input end 95% 2X2 coupler II and the photoelectric detector PD I, the circulator II, the input end 95% 2X2 coupler II and the photoelectric detector PD2 are connected, the input end 95% 2X2 coupler II is connected with the Faraday coil, and the photoelectric detector PD I, the photoelectric detector PD2 and the Faraday coil are both connected with the analog-digital interface. The method aims at the contradiction between the linearity and the measurement range of the traditional single closed loop and the defect that the traditional double closed loop is limited by the linearity and the control range of a control system.
Description
Technical Field
The invention relates to the field of resonant fiber optic gyroscopes, in particular to a resonant fiber optic gyroscope based on optical rotation coil frequency compensation and a closed-loop control method thereof.
Background
A Resonant Fiber Optic Gyroscope (RFOG) is an angular rate sensor that uses the Sagnac effect to generate a multi-beam interference resonance phenomenon in a ring resonator, and is used to measure the rotational speed of a carrier. Compared with the first generation (interference type) fiber-optic gyroscope, the resonance type fiber-optic gyroscope has more theoretical prospect and advantages in the application of a plurality of fields such as spaceflight, aviation, navigation and the like, uses shorter optical fibers under the condition of achieving the same precision with the interference type fiber-optic gyroscope, can reduce the cost by the shorter optical fiber length, reduces the sensitivity degree of the gyroscope to temperature and pressure, and has obvious advantages in the aspect of miniaturization and integration of the gyroscope.
Common resonant fiber optic gyroscopes can be divided into single closed loop systems and double closed loop systems, wherein in the single closed loop systems, along with the increase of the rotating speed, the working point can linearly move on a demodulation curve, the adjustment trends of two quantities, namely linearity and measurement range, are opposite, the two quantities cannot simultaneously reach the optimum, and the linearity error can be compensated only through calibration, table lookup and interpolation; in a double closed-loop system, because the working point is theoretically fixed at the zero point, the control signal is the output signal to be obtained, and theoretically, the limiting factors of the linearity and the measurement range are not the demodulation curve any more, but the linearity and the control range of the control system. However, because a differential control quantity needs to be introduced into the control system, the performance and the precision of the system are directly influenced by the system type, the tracking speed, the control precision and the like of the controller, under some special rotating speed conditions, tiny noise and steady-state errors generated by the controller are mixed in an output signal and cannot be eliminated, and even the gyroscope is separated from a working area and is unlocked, so that a large amount of burrs are generated in data.
Disclosure of Invention
The invention provides a resonant fiber-optic gyroscope based on optical rotation coil frequency compensation and a closed-loop control method thereof, aiming at the contradiction between the linearity and the measurement range of the traditional single closed loop and the defect that the traditional double closed loop is limited by the linearity and the control range of a control system.
The invention is realized by the following technical scheme:
a resonant fiber optic gyroscope based on optical rotation coil frequency compensation comprises a laser 1, a 50% 1 x2 coupler I2, a phase modulator PM I3, a phase modulator PM II 4, a circulator I5, a circulator II 6, an input end 95% 2x2 coupler II 7, a Faraday coil 8, a photoelectric detector PD I9, a photoelectric detector PD210, a digital-analog interface, a digital system and an analog-digital interface;
the laser 1 is respectively connected with a 50% 1 × 2 coupler I2 and a digital-analog interface, the 50% 1 × 2 coupler I2 is respectively connected with a phase modulator PM I3 and a phase modulator PM II 4, the phase modulator PM I3 is respectively connected with a circulator I5, a photoelectric detector PD I9 and the digital-analog interface, and the phase modulator PM II 4 is respectively connected with a circulator II 6, a photoelectric detector PD210 and the digital-analog interface;
the circulator I5 is respectively connected with an input end 95% 2X2 coupler II 7 and a photoelectric detector PD I9, the circulator II 6, the input end 95% 2X2 coupler II 7 and the photoelectric detector PD210 are connected, the input end 95% 2X2 coupler II 7 is connected with a Faraday coil 8, and the photoelectric detector PD I9, the photoelectric detector PD210 and the Faraday coil 8 are both connected with a modulus interface;
the digital-analog interface is connected with the analog-digital interface through a digital system.
A resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation is disclosed, wherein a digital-to-analog interface comprises a digital-to-analog converter ADC II 16, a digital-to-analog converter ADC III 17 and a digital-to-analog converter ADC IV 18;
the digital-to-analog converter ADC II 16 is connected with the phase modulator PM II 4,
the digital-to-analog converter ADC iii 17 is connected to the phase modulator PM i 3,
the digital-to-analog converter ADC IV 18 is connected with the laser 1.
A resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation is disclosed, wherein the digital system comprises a demodulation module I19, a demodulation module II 20, a modulation signal generation module 21 and a laser frequency locking control module 22;
the modulation signal generation module 21 is respectively connected with the digital-to-analog converter ADC II 16 and the digital-to-analog converter ADC III 17,
adding and subtracting the demodulation signals output by the demodulation module I19 and the demodulation module II 20 respectively to obtain two paths of signals;
the laser frequency locking control module 22 receives a signal obtained by adding the demodulation module I19 and the demodulation module II 20;
and the signal obtained by subtracting the demodulation module I19 and the demodulation module II 20 is transmitted to a digital-to-analog converter ADC I15 of the analog-to-digital interface and is compared with the output signal of the gyroscope.
A resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation is disclosed, wherein an analog-digital interface comprises an analog-digital interface low-pass filter I11, a low-pass filter II 12, an analog-digital converter ADC I13, an analog-digital converter ADC II 14, a digital-analog converter ADC I15 and a voltage-controlled current source 23;
the analog-to-digital interface low-pass filter I11 is respectively connected with the photoelectric detector PD210 and the analog-to-digital converter ADC I13,
the voltage-controlled current source 23 is respectively connected with the Faraday coil 8 and the digital-to-analog converter ADC I15,
the low-pass filter II 12 is respectively connected with the photoelectric detector PD I9 and the analog-to-digital converter ADC II 14, and the analog-to-digital converter ADC II 14 is connected with the demodulation module II 20.
A resonant fiber-optic gyroscope based on optical rotation coil frequency compensation is characterized in that a tunable laser is connected with a 50% coupler, two outputs of the 50% coupler are respectively connected with a first path phase modulator and a second path phase modulator, the first path phase modulator is connected with a circulator, the same second path phase modulator is connected with a circulator, the output ends of the No. 2 first path circulator and the second path circulator and a 95% coupler enter a circular polarization fiber ring resonant cavity, the output ends of the No. 3 first path circulator and the second path circulator are connected with photoelectric detectors PM1 and PM2, and output signals of the photoelectric detectors PM1 and PM2 are respectively connected with low- pass filters 1 and 2 so as to enter a digital system.
A resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation is disclosed, wherein a modulation signal generation module in a digital system generates two paths of sine electrical signals to be sent to phase modulators PM1 and PM2, a voltage signal from a low-pass filter is sent to a demodulation module through an ADC (analog-to-digital converter), the output sum generated by the demodulation module is sent to a laser tuning end, and the generated output difference is used as the differential output of the gyroscope on one hand and is sent to a voltage-controlled current source to control the current in a Faraday coil on the other hand; the Faraday coil is sleeved on the optical fiber ring, and two ends of the Faraday coil are connected with the output end of the voltage-controlled current source.
A closed-loop control method of a resonant fiber-optic gyroscope based on optical rotation coil frequency compensation is characterized in that an output signal is determined by the difference of two paths of demodulation values and the state of a Faraday coil, so that the gyroscope output value is the sum of a rotating speed value equivalent to the current introduced into the Faraday coil and a rotating speed value corresponding to the demodulation output; dividing two thresholds in the linear area of the demodulation curve, when the demodulation signal exceeds one of the left or right thresholds, the controller generates a constant control quantity corresponding to the opposite direction of the direction;
the Faraday coil control signal is step-shaped;
the demodulated output signal appears as a saw-tooth shaped periodic signal.
The closed-loop control method for the resonant fiber-optic gyroscope based on the optical rotation coil frequency compensation divides two thresholds in a linear region of a demodulation curve, and particularly, when the linearity does not become greater in an equal proportion along with the frequency difference of a horizontal axis on an output curve graph, output values corresponding to the vertical axis at two end points of the linear region are obtained.
A closed-loop control method of a resonant fiber-optic gyroscope based on optical rotation coil frequency compensation is characterized in that linearly polarized light emitted by a fiber laser is divided into two beams after passing through a 1:1 beam splitter, the frequencies of the two beams of light are modulated into a sine signal form after passing through a lithium niobate phase modulator, the two beams of light pass through a circulator and enter a circular polarization resonant cavity through a 2x2 fiber coupler, the polarization state of the laser is converted into circularly polarized light by the linearly polarized light under the action of two wave plates and then converted into linearly polarized light to be changed periodically, light with different cycle turns in clockwise and anticlockwise directions forms multi-beam interference at the coupler, and a light intensity signal formed by the interference is received by a photoelectric detector through the circulator and is collected by an analog-to-digital converter to be converted into a digital electric signal to enter a digital processing system in an FPGA.
A closed-loop control method of a resonant fiber-optic gyroscope based on optical rotation coil frequency compensation is characterized in that two paths of signals are processed in a completely symmetrical manner and time, two clockwise and anticlockwise demodulation quantities in direct proportion to frequency can be obtained through modulation and demodulation of the signals, the difference between the sum of the two demodulation quantities and a set target value taking a resonance valley bottom as a center is used as an error signal, and closed-loop locking control is realized on laser frequency through a tuning end of a laser after the error signal passes through a closed-loop controller so as to enable the laser frequency to be locked at the middle position of two resonance frequencies in the clockwise and anticlockwise directions; the difference between the two demodulation amounts is used as a control signal of the other loop of the gyroscope, the Faraday rotation controller firstly judges whether the output value exceeds a set linear region threshold value, if not, the Faraday rotation controller does not act, and only the difference between the two demodulation amounts is used as the output of the gyroscope; if the quantity exceeds the threshold value of the linear region, the output signal is formed by adding the difference value of two demodulation values and the equivalent output generated by the optical rotation effect.
The invention has the beneficial effects that:
the invention further reduces the short-term fluctuation, steady-state error and the like of the control system on the basis of keeping the advantages of high linearity, large dynamic range and the like of the double closed loop, and can better work under various complex rotating speed conditions.
Drawings
FIG. 1 is a schematic diagram of a resonant gyroscopic system of the present invention.
Fig. 2 is a schematic diagram of the demodulation curve threshold of the present invention.
Fig. 3 is a graph of the variation of the control signal and the demodulation signal with the rotation speed according to the present invention, wherein fig. 3- (a) is a graph of the variation of the control signal with the rotation speed, and fig. 3- (b) is a graph of the variation of the demodulation signal with the rotation speed.
FIG. 4 is a graph of the control signal and the demodulation signal of the present invention as a function of the rotation speed, wherein FIG. 4- (a) is a demodulation graph, and FIG. 4- (b) is a system output graph after calculation.
FIG. 5 is a graph comparing the results of the Allen variance test of the present invention (blue curve) with a typical double closed loop scheme.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A resonant fiber optic gyroscope based on optical rotation coil frequency compensation comprises a laser 1, a 50% 1 x2 coupler I2, a phase modulator PM I3, a phase modulator PM II 4, a circulator I5, a circulator II 6, an input end 95% 2x2 coupler II 7, a Faraday coil 8, a photoelectric detector PD I9, a photoelectric detector PD210, a digital-analog interface, a digital system and an analog-digital interface;
the laser 1 is respectively connected with a 50% 1 × 2 coupler I2 and a digital-to-analog interface, the 50% 1 × 2 coupler I2 is respectively connected with a phase modulator PM I3 and a phase modulator PM II 4, the phase modulator PM I3 is respectively connected with a circulator I5, a photoelectric detector PD I9 and the digital-to-analog interface, and the phase modulator PM II 4 is respectively connected with a circulator II 6, a photoelectric detector PD II 10 and the digital-to-analog interface;
the circulator I5 is respectively connected with an input end 95% 2X2 coupler II 7 and a photoelectric detector PD I9, the circulator II 6, the input end 95% 2X2 coupler II 7 and a photoelectric detector PD II 10 are connected, the input end 95% 2X2 coupler II 7 is connected with a Faraday coil 8, and the photoelectric detector PD I9 and the photoelectric detector PD II 10 and the Faraday coil 8 are both connected with a modulus interface;
the digital-analog interface is connected with the analog-digital interface through a digital system.
A resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation is disclosed, wherein a digital-to-analog interface comprises a digital-to-analog converter ADC II 16, a digital-to-analog converter ADC III 17 and a digital-to-analog converter ADC IV 18;
the digital-to-analog converter ADC II 16 is connected with the phase modulator PM II 4,
the digital-to-analog converter ADC iii 17 is connected to the phase modulator PM i 3,
the digital-to-analog converter ADC IV 18 is connected with the laser 1.
A resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation is disclosed, wherein the digital system comprises a demodulation module I19, a demodulation module II 20, a modulation signal generation module 21 and a laser frequency locking control module 22;
the modulation signal generation module 21 is respectively connected with the digital-to-analog converter ADC II 16 and the digital-to-analog converter ADC III 17,
adding and subtracting the demodulation signals output by the demodulation module I19 and the demodulation module II 20 respectively to obtain two paths of signals; wherein
The added signals are used for realizing laser frequency locking; -the subtracted signal as a gyro system output.
The laser frequency locking control module 22 receives a signal obtained by adding the demodulation module I19 and the demodulation module II 20;
and the signal obtained by subtracting the demodulation module I19 and the demodulation module II 20 is transmitted to a digital-to-analog converter ADC I15 of the analog-to-digital interface and is compared with the output signal of the gyroscope.
A resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation is disclosed, wherein an analog-digital interface comprises an analog-digital interface low-pass filter I11, a low-pass filter II 12, an analog-digital converter ADC I13, an analog-digital converter ADC II 14, a digital-analog converter ADC I15 and a voltage-controlled current source 23;
the analog-to-digital interface low-pass filter I11 is respectively connected with the photoelectric detector PD210 and the analog-to-digital converter ADC I13,
the voltage-controlled current source 23 is respectively connected with the Faraday coil 8 and the digital-to-analog converter ADC I15,
the low-pass filter II 12 is respectively connected with the photoelectric detector PD I9 and the analog-to-digital converter ADC II 14, and the analog-to-digital converter ADC II 14 is connected with the demodulation module II 20.
A resonant fiber-optic gyroscope based on optical rotation coil frequency compensation is characterized in that a tunable laser is connected with a 50% coupler, two outputs of the 50% coupler are respectively connected with a first path phase modulator and a second path phase modulator, the first path phase modulator is connected with a circulator, the same second path phase modulator is connected with a circulator, the output ends of the No. 2 first path circulator and the second path circulator and a 95% coupler enter a circular polarization fiber ring resonant cavity, the output ends of the No. 3 first path circulator and the second path circulator are connected with photoelectric detectors PM1 and PM2, and output signals of the photoelectric detectors PM1 and PM2 are respectively connected with low- pass filters 1 and 2 so as to enter a digital system.
A resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation is disclosed, wherein a modulation signal generation module in a digital system generates two paths of sine electrical signals to be sent to phase modulators PM1 and PM2, a voltage signal from a low-pass filter is sent to a demodulation module through an ADC (analog-to-digital converter), the output sum generated by the demodulation module is sent to a laser tuning end, and the generated output difference is used as the differential output of the gyroscope on one hand and is sent to a voltage-controlled current source to control the current in a Faraday coil on the other hand; the Faraday coil is sleeved on the optical fiber ring, and two ends of the Faraday coil are connected with the output end of the voltage-controlled current source.
A closed-loop control method of a resonant fiber-optic gyroscope based on optical rotation coil frequency compensation is characterized in that an output signal is determined by the difference of two paths of demodulation values and the state of a Faraday coil, so that the gyroscope output value is the sum of a rotating speed value equivalent to the current introduced into the Faraday coil and a rotating speed value corresponding to the demodulation output; dividing two thresholds in the linear region of the demodulation curve, and generating a constant control quantity corresponding to the opposite direction of the direction by the controller when the demodulation signal exceeds one of the left or right thresholds; the threshold diagram is shown in fig. 2. The vertical line in the figure is the calibrated threshold. As shown in figure 3 of the drawings,
a is a curve of the Faraday coil control signal changing along with the rotating speed, the horizontal axis of the curve is the rotating speed, the vertical axis of the curve is the size of the demodulation output equivalent to the control quantity, and as the demodulation output linearly increases along with the increase of the rotating speed each time, the controller is triggered to act each time the demodulation output reaches a threshold value, so that the control signal is in a step shape;
b is the curve of the demodulation output signal changing with the rotating speed, and due to the action of the control signal, the demodulation output value which should increase linearly with the rotating speed appears as a sawtooth-shaped periodic signal in the process of being continuously pulled back to a linear area.
The closed-loop control method for the resonant fiber-optic gyroscope based on the optical rotation coil frequency compensation divides two thresholds in a linear region of a demodulation curve, and particularly, when the linearity does not become greater in an equal proportion along with the frequency difference of a horizontal axis on an output curve graph, output values corresponding to the vertical axis at two end points of the linear region are obtained.
A closed-loop control method of a resonant fiber-optic gyroscope based on optical rotation coil frequency compensation is characterized in that linearly polarized light emitted by a fiber laser is divided into two beams after passing through a 1:1 beam splitter, the frequencies of the two beams are modulated into a sine signal form after passing through a lithium niobate phase modulator, the two beams pass through a circulator and enter a circular polarization resonant cavity through a 2x2 fiber coupler, under the action of the two wave plates, the polarization state of the laser is converted from linearly polarized light to circularly polarized light and then converted into linearly polarized light to be periodically changed, the yellow part and the orange part are respectively transmitted along the clockwise direction and the anticlockwise direction in the resonant cavity, and at the coupler, light with different cycle turns in clockwise and anticlockwise directions forms multi-beam interference, the light intensity signal formed by interference is received by the photoelectric detector through the circulator and is collected by the analog-to-digital converter to be converted into a digital electric signal, and the digital electric signal enters a digital processing system in the FPGA.
A closed-loop control method of a resonant fiber-optic gyroscope based on optical rotation coil frequency compensation is characterized in that two paths of signals are processed in a completely symmetrical manner and time, two clockwise and anticlockwise demodulation quantities in direct proportion to frequency can be obtained through modulation and demodulation of the signals, the difference between the sum of the two demodulation quantities and a set target value taking a resonance valley bottom as a center is used as an error signal, and closed-loop locking control is realized on laser frequency through a tuning end of a laser after the error signal passes through a closed-loop controller so as to enable the laser frequency to be locked at the middle position of two resonance frequencies in the clockwise and anticlockwise directions; the difference between the two demodulation amounts is used as a control signal of the other loop of the gyroscope, the Faraday rotation controller firstly judges whether the output value exceeds a set linear region threshold value, if not, the Faraday rotation controller does not act, and only the difference between the two demodulation amounts is used as the output of the gyroscope; if the quantity exceeds the threshold value of the linear area, the controller provides a constant current for the Faraday coil, the Sagnac effect is counteracted through the optical rotation effect, the demodulation signal is pulled back to the linear area again, and the output signal is formed by the sum of the difference value of two demodulation values and the equivalent output generated by the optical rotation effect.
The following is an embodiment of the resonant fiber-optic gyroscope with frequency compensation for the optical rotation coil according to the present invention, in which fig. 4(a) is the system demodulation output, and fig. 4(b) is the system output after calculation, and it can be seen from the figure that no oscillation occurs near the threshold, the data is well linked before and after the controller action, and the system works stably.
To evaluate system performance, a turret test was performed on the scheme of the present invention and a typical double closed loop scheme under the same conditions to obtain the Allen variance curves of the two, as shown in FIG. 5. It can be seen from the figure that compared with the typical double closed loop scheme, the angular random walk coefficient of the scheme of the invention is reduced from 3.67 °/√ h to 2.52 °/√ h, the zero offset stability is reduced from 37 °/h to 18 °/h, and the system performance is greatly improved.
Claims (10)
1. A resonance type fiber-optic gyroscope based on optical rotation coil frequency compensation is characterized by comprising a laser (1), a 50% 1 x2 coupler I (2), a phase modulator PM I (3), a phase modulator PM II (4), a circulator I (5), a circulator II (6), an input end 95% 2x2 coupler II (7), a Faraday coil (8), a photoelectric detector PD I (9), a photoelectric detector PD2(10), a digital-analog interface, a digital system and an analog-digital interface;
the laser (1) is respectively connected with a 50% 1 × 2 coupler I (2) and a digital-analog interface, the 50% 1 × 2 coupler I (2) is respectively connected with a phase modulator PM I (3) and a phase modulator PM II (4), the phase modulator PM I (3) is respectively connected with a circulator I (5), a photoelectric detector PD I (9) and the digital-analog interface, and the phase modulator PM II (4) is respectively connected with a circulator II (6), a photoelectric detector PD2(10) and the digital-analog interface;
the circulator I (5) is respectively connected with an input end 95% 2X2 coupler II (7) and a photoelectric detector PD I (9), the circulator II (6), the input end 95% 2X2 coupler II (7) and the photoelectric detector PD2(10) are connected, the input end 95% 2X2 coupler II (7) is connected with a Faraday coil (8), and the photoelectric detector PD I (9) and the photoelectric detector PD2(10) are both connected with the Faraday coil (8) and an analog-digital interface;
the digital-analog interface is connected with the analog-digital interface through a digital system.
2. The resonant fiber-optic gyroscope of claim 1, wherein the digital-to-analog interface comprises a digital-to-analog converter ADC ii (16), a digital-to-analog converter ADC iii (17), and a digital-to-analog converter ADC iv (18);
the digital-to-analog converter ADC II (16) is connected with the phase modulator PM II (4),
the digital-to-analog converter ADC III (17) is connected with the phase modulator PM I (3),
the digital-to-analog converter ADC IV (18) is connected with the laser (1).
3. The resonant fiber optic gyroscope according to claim 1, wherein the digital system comprises a demodulation module I (19), a demodulation module II (20), a modulation signal generation module (21) and a laser frequency locking control module (22);
the modulation signal generation module (21) is respectively connected with a digital-to-analog converter ADC II (16) and a digital-to-analog converter ADC III (17),
adding and subtracting the demodulation signals output by the demodulation module I (19) and the demodulation module II (20) respectively to obtain two paths of signals;
the laser frequency locking control module (22) receives a signal obtained by adding the demodulation module I (19) and the demodulation module II (20);
and the signal obtained by subtracting the demodulation module I (19) and the demodulation module II (20) is transmitted to a digital-to-analog converter ADC I (15) of the analog-to-digital interface and is compared with the output signal of the gyroscope.
4. The resonant fiber optic gyroscope of claim 3, wherein the analog-to-digital interface comprises an analog-to-digital interface low-pass filter I (11), a low-pass filter II (12), an analog-to-digital converter ADC I (13), an analog-to-digital converter ADC II (14), a digital-to-analog converter ADC I (15) and a voltage-controlled current source (23);
the analog-digital interface low-pass filter I (11) is respectively connected with the photoelectric detector PD2(10) and the analog-digital converter ADC I (13),
the voltage-controlled current source (23) is respectively connected with the Faraday coil (8) and the digital-to-analog converter ADC I (15),
the low-pass filter II (12) is respectively connected with the photoelectric detector PD I (9) and the analog-to-digital converter ADC II (14), and the analog-to-digital converter ADC II (14) is connected with the demodulation module II (20).
5. The resonant fiber-optic gyroscope of claim 1, wherein the transmission of the photoelectric signal of the resonant fiber-optic gyroscope is specifically that the tunable laser is connected to a 50% coupler, two outputs of the 50% coupler are respectively connected to a first phase modulator and a second phase modulator, the first phase modulator is connected to the circulator, the same second phase modulator is connected to the circulator, output terminals No. 2 of the first circulator and the second circulator are connected to a 95% coupler, the output terminals No. 3 of the first circulator and the second circulator are connected to the photodetectors PM1 and PM2, and output signals of the photodetectors PM1 and PM2 are respectively connected to the low-pass filters 1 and 2, so as to enter the digital system.
6. The resonant fiber optic gyroscope of claim 5, wherein the modulation signal generation module in the digital system generates two sinusoidal electrical signals to the phase modulators PM1, PM2, the voltage signal from the low pass filter is sent to the demodulation module via the ADC, the output sum generated by the demodulation module is sent to the tuning end of the laser, and the generated output difference is used as the differential output of the gyroscope on one hand and is sent to the voltage-controlled current source to control the current in the faraday coil on the other hand; the Faraday coil is sleeved on the optical fiber ring, and two ends of the Faraday coil are connected with the output end of the voltage-controlled current source.
7. The method according to claim 1, wherein the closed-loop control method of the resonant fiber-optic gyroscope based on the optical rotation coil frequency compensation is characterized in that the closed-loop control method is that, since the output signal is determined by the difference between the two demodulated values and the state of the faraday coil, the gyroscope output value is the sum of the equivalent rotation speed value of the current passed through the faraday coil and the rotation speed value corresponding to the demodulated output; dividing two thresholds in the linear region of the demodulation curve, and generating a constant control quantity corresponding to the opposite direction of the direction by the controller when the demodulation signal exceeds one of the left or right thresholds;
the Faraday coil control signal is step-shaped;
the demodulated output signal appears as a saw-tooth shaped periodic signal.
8. The closed-loop control method of the resonant fiber-optic gyroscope of claim 7, wherein the dividing of the two thresholds in the linear region of the demodulation curve is specifically that, on the output graph, when linearity does not become proportionally greater as the frequency difference of the horizontal axis becomes greater, output values corresponding to the vertical axis at two end points of the linear region are obtained.
9. The closed-loop control method of the resonant fiber-optic gyroscope of claim 7, wherein linearly polarized light emitted by the fiber laser is split into two beams after passing through a 1:1 beam splitter, the two beams of light are respectively modulated into a sinusoidal signal form after passing through a lithium niobate phase modulator, then pass through a circulator, enter a circular polarization resonant cavity through a 2x2 fiber coupler, the polarization state of the laser is converted from the linearly polarized light into circularly polarized light under the action of two wave plates and then converted into linearly polarized light to be changed periodically, and light with different cycle turns in clockwise and counterclockwise directions forms multi-beam interference at the coupler, and a light intensity signal formed by the interference is received by a photodetector through the circulator and is collected by an analog-to-digital converter to be converted into a digital electrical signal to enter a digital processing system in the FPGA.
10. The closed-loop control method of the resonant fiber-optic gyroscope according to claim 7, characterized in that the two signal processing paths are completely symmetrical in form and time, two clockwise and counterclockwise demodulation amounts proportional to the frequency can be obtained by modulating and demodulating the signals, the difference between the sum of the two demodulation amounts and a set target value centered on a resonance valley is taken as an error signal, and after passing through a closed-loop controller, the laser frequency is subjected to closed-loop locking control by a tuning end of a laser to be locked at the middle position of the two resonant frequencies in the clockwise and counterclockwise directions; the difference between the two demodulation amounts is used as a control signal of the other loop of the gyroscope, the Faraday rotation controller firstly judges whether the output value exceeds a set linear region threshold value, if not, the Faraday rotation controller does not act, and only the difference between the two demodulation amounts is used as the output of the gyroscope; if the quantity exceeds the threshold value of the linear region, the output signal is formed by adding the difference value of two demodulation values and the equivalent output generated by the optical rotation effect.
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