Optical fiber gyroscope impact resistance method for judging and adjusting integrator based on demodulation value

Abstract

The invention relates to the technical field of fiber-optic gyroscopes, in particular to a fiber-optic gyroscope impact resistance method for judging and adjusting an integrator based on a demodulation value, which is used for improving the impact resistance of a high-precision interference type fiber-optic gyroscope. According to the anti-impact method disclosed by the invention, the generation of the residual speed error is judged according to the output voltage demodulation value of the photoelectric detector acquired by the forward channel analog-to-digital converter of the optical fiber gyroscope, and the integrator is further subjected to zero clearing adjustment, so that the offset of a closed-loop working point of the optical fiber gyroscope is avoided, namely, the cross-stripe phenomenon is avoided, and the anti-impact performance of the optical fiber gyroscope is improved. The impact resistance of the interference type optical fiber gyroscope is improved.

Description

Technical Field

[0001] This invention relates to the field of fiber optic gyroscope technology, and specifically to a shock-resistant method for fiber optic gyroscopes based on demodulation value judgment and adjustment of the integrator. Background Technology

[0002] With the rapid development of modern optical technology, interferometric fiber optic gyroscopes have gradually matured. Fiber optic gyroscopes that have been engineered and commercialized have reached a strategic level and have become the preferred solution for angular rate measurement devices in many fields.

[0003] However, with the continuous expansion of application scenarios, researchers have found that vibration and shock pose new challenges to the measurement accuracy of fiber optic gyroscopes. When the device is subjected to severe vibration, a radial impact component exists on the fiber optic loop, causing abnormal changes in the measurement signal. This interference can sometimes exceed the normal measurement range of the fiber optic gyroscope, thus affecting the final measurement results. Overcoming the errors caused by vibration and shock has become one of the key research areas for improving the performance of fiber optic gyroscopes.

[0004] Traditional typical interferometric fiber optic gyroscope structure, such as Figure 2 As shown, a closed-loop feedback method is used to achieve angular rate measurement with a large dynamic range. When the phase difference caused by the angular rate after feedback within one closed-loop cycle satisfies... At that time, according to the principle of digital closed-loop systems, the closed-loop feedback phase The closed-loop controller can be adjusted until the closed-loop error demodulated by the closed-loop system is 0. At this point, the Sagnac phase shift caused by the angular rate will be reduced. The gyroscope's operating point is confined to its original operating point, corresponding to the zero-order fringe of the interference pattern. The fiber optic gyroscope operates normally and does not affect subsequent measurements. However, when the phase difference caused by the feedback angular rate within a closed-loop cycle satisfies... or Due to the periodicity of cosine interference fringes and the working principle of the closed-loop system, interferometric fiber optic gyroscopes will exhibit fringe-crossing phenomena, meaning that fringe-crossing always exists. This ensures that the closed-loop error of the closed-loop system is zero. The angular rate output by the fiber optic gyroscope originates from closed-loop feedback. In this case, the output angular rate cannot reflect the phase difference caused by the actual angular rate. When the fiber optic gyroscope outputs an error, closed-loop misalignment occurs, causing a shift in the closed-loop operating point that cannot be recovered from. This is especially problematic for high-precision fiber optic gyroscopes, where vibration and shock can easily cause cross-friction phenomena. The radial impact component on the fiber loop introduces significant angular acceleration, generating a large instantaneous angular velocity within a single closed-loop feedback cycle, leading to gyroscope malfunction and a shift in the closed-loop operating point. At this point, the gyroscope's operating state corresponds to the [number missing]. n Within the stripe area, the gyroscope cannot function properly.

[0005] Essentially, the cross-striping phenomenon occurs because the closed-loop tracking rate of the fiber optic gyroscope differs from the actual rotational speed. Phase shift means the output cannot reflect the actual rotational speed. For fiber optic gyroscopes, the closed-loop period is often on the order of microseconds, reaching... The angular acceleration of phase shift is often very large, making it difficult to occur in real-world conditions. Therefore, in the actual operation of a fiber optic gyroscope, the fringe crossing phenomenon mainly occurs due to the accumulated velocity error and actual rotational speed over multiple closed-loop cycles. Phase shift occurs, at which point the gyroscope output cannot be displayed correctly. The biggest reason for the accumulation of speed errors comes from the limitations of the actual circuit. Due to the amplitude limitation of the input voltage of the analog-to-digital converter (ADC) in the forward circuit of the fiber optic gyroscope, the maximum angular rate that the fiber optic gyroscope can track is much lower than the actual angular rate. The angular rate value corresponding to the phase shift means that the angular rate input can easily exceed the maximum tracking angular rate value, causing a continuous accumulation of residual velocity error. Vibration and shock can cause a short-term increase in angular rate, which often leads to accumulated error and further results in cross-striping.

[0006] Currently, high-precision fiber optic gyroscopes have largely met the stringent requirements of various fields for high-precision navigation equipment, providing solid support for the vigorous development of high-precision navigation systems. With the continuous advancement of interferometric fiber optic gyroscope research, shock resistance has become one of the crucial performance indicators that fiber optic gyroscopes must meet, especially under harsh mechanical environments such as rocket launches, high-speed maneuvering aircraft, airborne weapon deployment, or vehicle travel on complex road surfaces. Therefore, research on cross-fringe problems caused by shock and vibration is particularly important. Summary of the Invention

[0007] In light of the above background, this invention proposes a shock resistance method for fiber optic gyroscopes based on demodulation value judgment and integrator adjustment, to improve the shock resistance performance of high-precision interferometric fiber optic gyroscopes. The shock resistance method of this invention uses the demodulated value of the photodetector output voltage acquired by the analog-to-digital converter in the forward channel of the fiber optic gyroscope to determine the generation of residual velocity error, and further zeroes and adjusts the integrator, thereby preventing the closed-loop operating point of the fiber optic gyroscope from shifting, i.e., avoiding the occurrence of cross-fringe phenomenon, and improving the shock resistance performance of the interferometric fiber optic gyroscope.

[0008] This invention provides a method for shock resistance of fiber optic gyroscopes based on demodulation value judgment and adjustment of the integrator. The specific steps are as follows: Step S1: Set the judgment threshold for the output voltage demodulation value in the logic processing circuit, which is used as the adjustment threshold for the integrator value to be cleared to zero after the interferometric fiber optic gyroscope is subjected to an impact. Step S2: Using the intrinsic frequency of the fiber optic gyroscope as the monitoring and calculation frequency, the output demodulation value of the interferometric fiber optic gyroscope in operation is acquired in real time. Step S3: Compare the acquired fiber optic gyroscope output demodulated value with the judgment threshold set in the logic processing circuit to obtain the adjusted integral value; Step S4: Use the integrated value after judgment and adjustment as the sensitive angular velocity output of the interferometric fiber optic gyroscope; Step S5: Repeat steps S2-S4 to continuously monitor, judge, and adjust the integrator of the impacted interferometric fiber optic gyroscope.

[0009] Optionally, the voltage demodulation value is: positive when the interferometric fiber optic gyroscope rotates in the positive direction; and negative when the interferometric fiber optic gyroscope rotates in the negative direction.

[0010] Optionally, the lower limit of the positive judgment threshold is set to ,in, U This represents the maximum permissible unidirectional input voltage value for the analog-to-digital converter saturation. K This is the scaling factor between the input voltage and the output digital value of the analog-to-digital converter. M This represents the number of sampling points of the interferometric fiber optic gyroscope within the modulation period; the upper limit of the negative judgment threshold is set to... .

[0011] Optionally, the upper limit of the positive judgment threshold is set to Digital quantity corresponding to phase shift The lower limit of the negative judgment threshold is set to Digital quantity corresponding to phase shift .

[0012] Optionally, for the modulation phase of square wave modulation and The output voltages of the photodetector after modulation are respectively and Then in Within a given time period, the demodulated output value of the interferometric fiber optic gyroscope .

[0013] Optionally, for the modulation phase of four-state modulation , , and The output voltages of the photodetector after modulation are respectively , , and Then in Within a given time period, the demodulated output value of the interferometric fiber optic gyroscope .

[0014] Optionally, if the demodulated output value of the fiber optic gyroscope is within the judgment threshold range, the integrator of the forward channel demodulation error in the logic processing circuit is cleared; if the demodulated output value of the fiber optic gyroscope is not within the judgment threshold range, the integrator performs integration.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: The beneficial effects of this invention are as follows: 1. The fiber optic gyroscope shock resistance method based on demodulation value judgment and integrator adjustment of the present invention addresses the problem of π phase shift between the accumulated velocity error and the actual rotational speed in multiple closed-loop cycles of an interferometric fiber optic gyroscope under shock conditions. That is, in practical applications, the fiber optic gyroscope still experiences fringe crossing phenomenon under low angular acceleration conditions. By monitoring the demodulation value of the forward channel, it is determined whether residual velocity error occurs, and the integrator is adjusted accordingly to ensure that the closed-loop operating point is always within the zero-order fringe of the interference fringes. This avoids the occurrence of fringe crossing phenomenon caused by low angular acceleration due to circuit limitations in practical applications, prevents continuous erroneous output of the gyroscope under shock conditions, and significantly improves the applicability and robustness of the fiber optic gyroscope in complex dynamic environments.

[0016] 2. The shock-resistant method for fiber optic gyroscopes based on demodulation value judgment and integrator adjustment of the present invention directly utilizes the demodulation value of the forward channel without changing the original optical path and circuit structure of the interferometric fiber optic gyroscope. This aligns with the core requirements of low cost and miniaturization of interferometric fiber optic gyroscopes and is suitable for various application scenarios. Furthermore, this solution is simple to implement and easy to operate. Attached Figure Description

[0017] Figure 1 This is a flowchart of the fiber optic gyroscope anti-shock method based on demodulation value judgment and adjustment of the integrator according to the present invention.

[0018] Figure 2 This is a schematic diagram of a typical interferometric fiber optic gyroscope.

[0019] Figure 3 This is a schematic diagram of the four-state modulation of a fiber optic gyroscope at different angular rates and the corresponding detector output results.

[0020] Figure 4 This is a comparison chart of the sensitive signal power of the photodetector at different angular velocities.

[0021] Figure 5 This is a comparison chart of signal output after photoelectric conversion and DC blocking at different angular velocities. Figure 6 This is a schematic diagram of the closed-loop feedback process of the interferometric fiber optic gyroscope in this invention. Detailed Implementation

[0022] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0023] This invention provides a shock-resistant method for fiber optic gyroscopes based on demodulation value judgment and integrator adjustment. It adds signal demodulation value judgment and angular rate demodulation error integrator zeroing adjustment operations to the traditional fiber optic gyroscope closed-loop feedback system, preventing the closed-loop operating point of the fiber optic gyroscope from shifting, thereby improving the shock resistance of the interferometric fiber optic gyroscope. The method provided by this invention is implemented in a logic processing circuit FPGA, such as... Figure 1 An interferometric fiber optic gyroscope comprises a light source, several passive optical devices, a photodetector, an integrated phase modulator, an optical fiber loop, and a signal processing circuit. Its structural diagram is shown below. Figure 2 As shown, the light emitted from the light source first passes through a polarization-maintaining coupler and is injected into the input port of the integrated phase modulator. It is then split into two beams, which are simultaneously injected from both ends of the fiber loop, propagating towards each other in clockwise and counterclockwise directions. After circling the loop once, the two beams return to the integrated phase modulator and interfere. The resulting interference signal is guided to the aforementioned polarization-maintaining coupler and finally transmitted to a photodetector, where it is converted into an electrical signal. This electrical signal is amplified and filtered before being sent to a logic processing unit for demodulation and processing. The generated feedback control signal is then loaded back onto the electrodes of the integrated phase modulator via a drive circuit, forming a precise closed-loop control system.

[0024] Preferably, the signal processing circuit includes a preamplifier, an analog-to-digital converter, a logic processing unit, a digital-to-analog converter, and an amplifier. The electrical signal after photoelectric conversion is blocked by DC and then amplified by the preamplifier. It is then converted into a digital signal by the analog-to-digital converter. This digital signal undergoes correlation processing by the logic processing unit to generate a feedback digital signal. This feedback digital signal is then converted into an analog signal by the digital-to-analog converter, amplified, and applied to the electrodes of the integrated phase modulator.

[0025] The specific implementation includes the following steps: Step S1: Set the judgment threshold for the output voltage demodulation value in the logic processing circuit. This threshold is used to adjust the integrator value to zero after the interferometric fiber optic gyroscope is subjected to an impact.

[0026] Preferably, when the interferometric fiber optic gyroscope rotates in the forward direction, the voltage demodulation value is positive, and the lower limit of the forward judgment threshold is set to... ,in, U This represents the maximum permissible unidirectional input voltage value for the analog-to-digital converter saturation. K This is the scaling factor between the input voltage and the output digital value of the analog-to-digital converter. M This represents the number of sampling points of the interferometric fiber optic gyroscope within the modulation period. When the interferometric fiber optic gyroscope rotates in the negative direction, the demodulated value is negative, so the upper limit of the negative judgment threshold is set to... .

[0027] It is understandable that the output digital value will vary for different gyroscope parameters. This parameter depends on the conversion factor of the analog-to-digital converter of the fiber optic gyroscope, and is related to the number of bits of the analog-to-digital converter, the operating mode selection, etc.

[0028] Furthermore, the upper limit of the positive judgment threshold is set as follows: Digital quantity corresponding to phase shift The lower limit of the negative judgment threshold is set to Digital quantity corresponding to phase shift .

[0029] Step S2: Using the intrinsic frequency of the fiber optic gyroscope as the monitoring and calculation frequency, the output demodulation value of the interferometric fiber optic gyroscope in operation is acquired in real time.

[0030] Preferably, the intrinsic frequency of the fiber optic gyroscope is twice the fiber loop transit time. ).

[0031] Furthermore, regarding the modulation phase of square wave modulation and The output voltages of the photodetector after modulation are respectively and Then in Within a given time period, the demodulated output value of the interferometric fiber optic gyroscope .

[0032] Furthermore, regarding the modulation phase of four-state modulation... , , and The output voltages of the photodetector after modulation are respectively , , and Then in Within a given time period, the demodulated output value of the interferometric fiber optic gyroscope .

[0033] Understandable, , , and The modulation voltage is a four-state modulation, corresponding to Figure 3 The four modulation phases of the modulated signal. Figure 3 Taking China as an example, it satisfies . Figure 3 This diagram illustrates the four-state modulation of a fiber optic gyroscope at different angular rates and the corresponding detector output results. I represents the interference intensity. This represents the phase difference of the gyroscope's sensitive rotational speed input. (A)-(F) represent interference phase differences of 0, 0, 0, and 0 respectively. , , , , This corresponds to the detector's output signal. In this paper, the modulation signal contains six modulation phases, denoted as 1-6, covering one four-state modulation cycle. The intensity changes of these output signals are compared to... Figure 4 As shown. When the phase of the input angular rate exceeds... At that time, due to the periodicity of the cosine function, the output angular rate will be unable to distinguish the actual input angular rate, for example... The corresponding demodulation value will be with The demodulation values ​​are consistent. Figure 4 The signal in the image undergoes photoelectric conversion, DC blocking, filtering, and amplification before being acquired by an analog-to-digital converter. The acquired signal is, for example... Figure 5 As shown. By Figure 5 As can be seen, the saturation voltage of the analog-to-digital converter (ADC) limits the acquisition of the input signal, with the maximum acquisition signal shown by the dashed line in the figure. When the amplitude of the input signal is large, the ADC can only sense a portion of the input angular velocity. This portion of the signal is demodulated, integrated, and then used as the sensitive angular velocity output and closed-loop feedback value. This portion cannot fully reflect the actual angular velocity input, and the residual amplitude will accumulate. After several closed-loop cycles, the accumulated residual velocity error may exceed [a certain value] within a certain closed-loop cycle. Phase causes the closed-loop tracking rate of the fiber optic gyroscope to differ from the actual rotational speed. Phase shift causes the output to fail to reflect the actual rotational speed, resulting in stripe crossing. Therefore, it is necessary to determine the demodulated value corresponding to the saturation voltage of the analog-to-digital converter to avoid stripe crossing.

[0034] Step S3: Compare the acquired fiber optic gyroscope output demodulated value with the judgment threshold set in the logic processing circuit to obtain the adjusted integral value; Specifically, if the demodulated output value of the fiber optic gyroscope is within the judgment threshold range, the integrator of the forward channel demodulation error in the logic processing circuit is cleared; if the demodulated output value of the fiber optic gyroscope is not within the judgment threshold range, the integrator performs normal integration.

[0035] Understandably, this invention judges and adjusts the integrator based on the demodulated value. The integrator continuously integrates the demodulated value. If the output demodulated value is outside the judgment threshold range, it indicates that the gyroscope will not experience fringe crossing. In this case, the demodulated value is integrated normally, and the integrated value, after appropriate processing, is output as the angular velocity that the fiber optic gyroscope is sensitive to. If the demodulated value is within the judgment threshold range, it indicates that the gyroscope's forward channel input is saturated. This situation easily leads to fringe crossing, meaning the integrator value cannot continuously reflect the actual gyroscope output, and this state is irreversible. Even if the output demodulated value is subsequently outside the judgment threshold range, the fiber optic gyroscope output will still be incorrect. Therefore, the integrator is reset to zero to avoid tracking the actual angular velocity.

[0036] Optionally, in step S3, each The time interval is used to determine the demodulated output value of the acquired fiber optic gyroscope. or Is it in [ , ]or[ , Within the interval. If or If the signal is within this range, the analog-to-digital converter in the forward channel cannot be sensitive to the full amplitude of the optical signal, resulting in a residual speed error. Therefore, the integrator for the forward channel demodulation error in the logic processing circuit is cleared. or If the error is not within this range, the integrator of the forward channel demodulation error in the logic processing circuit performs normal integration.

[0037] Step S4: The integral value after judgment and adjustment is used as the sensitive angular velocity output of the interferometric fiber optic gyroscope.

[0038] Preferably, in step S4, after judging the demodulated value, the integrator of the forward channel demodulation error in the logic processing circuit outputs the adjusted integral value as the output value of the angular velocity and the closed-loop feedback value. When the integral value of the integrator is cleared to zero, the interferometric fiber optic gyroscope no longer tracks the actual input angular velocity, that is, the closed-loop operating point of the interferometric fiber optic gyroscope is always within the zero-order fringe of the interference fringes.

[0039] Step S5: Repeat steps S2-S4 to continuously monitor, judge, and adjust the integrator of the impacted interferometric fiber optic gyroscope.

[0040] This invention adjusts the integrator of the fiber optic gyroscope so that it does not track the actual rotational speed when crossing a fringe, thereby preventing the gyroscope's operating point from stably operating on other fringes and ensuring that it remains within the first fringe at any given time. This method can prevent continuous erroneous output caused by shocks.

[0041] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0043] In this invention, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for judging and adjusting the impact resistance of a fiber-optic gyroscope based on demodulation values, characterized in that, The specific steps are as follows: Step S1: setting a judgment threshold of output voltage demodulation value in the logic processing circuit, which is used as a regulation threshold of the integrator value zeroing after the interferometric fiber-optic gyroscope is impacted; Step S2: taking the eigenfrequency of the fiber-optic gyroscope as a monitoring and calculation frequency, and collecting the output demodulation value of the interferometric fiber-optic gyroscope in operation in real time; Step S3: comparing the collected output demodulation value of the fiber-optic gyroscope with the judgment threshold set in the logic processing circuit, and obtaining an adjusted integrator value; Step S4: taking the adjusted integrator value after judgment as an angular velocity output sensitive to the interferometric fiber-optic gyroscope; Step S5: cyclically executing steps S2-S4 to continuously monitor and judge the interferometric fiber-optic gyroscope impacted and adjust the integrator.

2. The optical fiber gyroscope shock resistance method according to claim 1, characterized in that, The voltage demodulation value is positive when the interferometric fiber-optic gyroscope rotates in a positive direction, and is negative when the interferometric fiber-optic gyroscope rotates in a negative direction.

3. The optical fiber gyroscope shock resistance method according to claim 2, characterized in that, The lower limit of the positive determination threshold is set as wherein, U is the maximum allowed unidirectional input voltage value for the ADC saturation; K is the proportional coefficient between the input voltage of the ADC and the output digital quantity; M is the number of sampling points of the interferometric fiber-optic gyroscope in a modulation period; and the upper limit of the negative determination threshold is set as .

4. The fiber optic gyroscope shock resistance method of claim 3, wherein, The upper limit of the positive determination threshold is set to a digital quantity corresponding to the phase shift The lower limit of the negative determination threshold is set to a digital quantity corresponding to the phase shift .

5. The optical fiber gyroscope shock resistance method according to claim 4, characterized in that, For square wave modulation, the modulation phase and The photoelectric detector detects the output voltage after modulation respectively and Then, in time, the output demodulation value of the interferometric fiber-optic gyroscope is .

6. The optical fiber gyroscope shock resistance method of claim 4, wherein, For the modulation phases of the four states , , and , the photoelectric detector detects the output voltages after modulation as , , and , then the demodulation value of the interferometric fiber-optic gyroscope output is in time.

7. The optical fiber gyroscope shock resistance method according to any one of claims 1-6, characterized in that, If the collected output demodulation value of the fiber-optic gyroscope is within the range of the judgment threshold, the integrator of the forward channel demodulation error in the logic processing circuit is executed to zero, and if the collected output demodulation value of the fiber-optic gyroscope is not within the range of the judgment threshold, the integrator is integrated.

Images