Method for improving scale performance of ultrahigh-precision fiber-optic gyroscope based on frequency compensation

Abstract

The invention belongs to the field of application of ultrahigh-precision optical gyroscopes, and particularly relates to a method for improving the scale performance of an ultrahigh-precision optical fiber gyroscope based on frequency compensation, which comprises the following steps of: setting a frequency compensation counter in a digital processing unit: in a system synchronization signal period, calculating the data acquisition number in the period; compensating the change of the number between the gyroscope data output number and the optical fiber inertial navigation data receiving frequency and between the resolving frequency and the optical fiber inertial navigation data receiving frequency; the method is realized through a frequency compensation counter: calculating the frequency change between the data output and calculation frequency of the fiber-optic gyroscope and the data receiving frequency of the fiber-optic inertial navigation system, and adding and designing the frequency compensation counter in a digital modulation-demodulation algorithm of the fiber-optic gyroscope. And the change between the gyroscope data output and resolving frequency and the optical fiber inertial navigation data receiving frequency is compensated.

Description

Technical Field

[0001] The present invention belongs to the field of ultra-high precision optical gyroscope applications, and in particular relates to a method for improving the scaling performance of an ultra-high precision optical fiber gyroscope based on frequency compensation. Background Art

[0002] Inertial technology is the core technology for inertial navigation, guidance and control, positioning and orientation, attitude stabilization and control, and overload sensing of various types of motion carriers. The gyroscope is the core component of the inertial system, which is used to sense the angular motion of the carrier relative to the inertial space and measure the angular displacement and angular velocity of the carrier.

[0003] As a high-precision angular rate sensor based on the Sagnac effect and without rotating parts, the fiber optic gyroscope has the advantages of high accuracy, long life, flexible structural design, fast startup time, and small size. At present, the accuracy of fiber optic gyroscopes has leaped from tactical and navigation levels to strategic levels. In particular, the accuracy index of ultra-high-precision fiber optic gyroscopes is required to be better than 0.0001° / h, and the scale factor accuracy is required to be better than 1ppm.

[0004] As the accuracy requirements of fiber optic gyroscopes continue to increase, the navigation and positioning accuracy of long-flight and high-precision fiber optic inertial navigation systems, which use ultra-high-precision fiber optic gyroscopes as core components, is also continuously improving.

[0005] Generally, the relationship between the Sagnac phase shift ɸs detected by the fiber optic gyroscope and the input rotation speed Ω can be expressed as: in, is the average wavelength, L is the length of the fiber ring, D is the diameter of the fiber ring, c is the speed of light in a vacuum, and K is the scale factor of the fiber gyroscope, which is the core indicator of the fiber gyroscope.

[0006] In the application of long-duration fiber-optic inertial navigation positioning, the gyroscope scale factor error can be coupled with the earth's rotation, which is equivalent to introducing an equivalent drift in the direction of the earth's rotation. According to the relationship between gyroscope drift and positioning error, the errors in the north and celestial components will cause the longitude error to diverge. Within a re-adjustment cycle, the positioning error caused by the 0.5ppm long-term scale factor error of the high-precision fiber-optic gyroscope after 90 days of autonomous navigation can be: Among them, the maximum positioning error is , is the angular velocity of the Earth's rotation, 60 is the conversion ratio of degrees to minutes, 90 represents 90 days, and 1 minute is The maximum positioning error is Approximately Therefore, the ultra-high precision fiber optic gyro scale factor performance is 0.5ppm. If other influences are not considered, the fiber optic inertial navigation positioning accuracy can achieve 1nmile / 2160h, and 2160h is 90 days. However, at present, when the ultra-high precision fiber optic gyro is self-tested, the scale factor performance is better than 0.5ppm, but the fiber optic inertial navigation positioning accuracy is far lower than the 1nmile / 2160h indicator. For example, the existing public fiber inertial navigation system can achieve a maximum of 1nmile / 360h, which is six times different from the fiber optic gyro scale factor performance of 0.5ppm of 1nmile / 2160h.

[0007] In order to effectively improve the scaling performance of the gyro when it is used in the system, a solution is urgently needed to compensate for the deterioration of the scaling performance of the gyro in the system to improve the scaling performance. Summary of the invention

[0008] The purpose of the present invention is to make corresponding improvements to the deterioration and shortcomings of the system scaling performance of the prior art. In order to effectively improve the scaling performance of the gyro when the system is used, the present invention proposes a method for improving the scaling performance of an ultra-high precision fiber optic gyroscope based on frequency compensation. The outstanding contribution of the present invention is to provide a solution for compensating for the deterioration of the gyro's system scaling performance to improve the scaling performance.

[0009] A method for improving the scaling performance of an ultra-high precision fiber optic gyroscope based on frequency compensation comprises the following steps: S1. Setting a frequency compensation counter in the digital processing unit: Under the system synchronization signal cycle, the number of data collection within the cycle is calculated; S2. Compensate for the change in the number of gyro data outputs and the number of solution frequencies and the number of fiber-optic inertial navigation data receiving frequencies; S3. Use the compensated data as the output data of the gyroscope.

[0010] Further, step S2 is a method for compensating for the change in the number of gyro data outputs and the number of solution frequencies and the number of fiber optic inertial navigation data receiving frequencies: Sending the number of data collected from the gyro output in each synchronization signal cycle to the system; The system receives the actual data collected and accumulates it to get the angular increment data output by the gyro. ; Calculate the gyro angle increment data according to the actual data collection number. , in is the apparent scale of the fiber optic gyroscope on the fiber optic system, is the gyro bias, is the angular increment of rotation, t is the time, The number of data collected in step S1.

[0011] Further, step S2 is a method for compensating for the change in the number of gyro data outputs and the number of solution frequencies and the number of fiber optic inertial navigation data receiving frequencies: The accumulated data sent to the inertial navigation system within a fixed period under the system synchronization signal cycle: if the number of data collected during the synchronization signal cycle increases, the excess data will be removed to ensure the consistency of the data number; if the number of data collected during the synchronization signal cycle decreases, the last collected data will be used to make up for the less collected data to ensure the consistency of the data number.

[0012] Furthermore, if the number of data collected during the synchronization signal period decreases, the method of using the last collected data to make up for the less collected data to ensure the consistency of the number of data is: According to the reduced number of data, take out the last collected data and calculate its average value; The system is compensated for the corresponding decrease in the number of data according to the obtained average value.

[0013] Furthermore, the frequency compensation counter is arranged in the FPGA modulation and demodulation unit of the fiber optic gyroscope.

[0014] Furthermore, the frequency compensation counter is arranged after the AD converter of the fiber optic gyroscope and receives the digital signal of the AD converter.

[0015] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: The present invention is realized by a frequency compensation counter: calculating the frequency change between the fiber optic gyroscope data output and solution frequency and the fiber optic inertial navigation system data receiving frequency, adding a designed frequency compensation counter in the fiber optic gyroscope digital modulation and demodulation algorithm, and compensating for the change between the gyroscope data output and solution frequency and the fiber optic inertial navigation data receiving frequency.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is a timing control diagram of the ultra-high precision fiber optic gyroscope provided by the present invention.

[0019] Figure 2It is a sampling diagram of the system synchronous square wave frequency provided by the present invention.

[0020] Figure 3 It is a connection diagram of the frequency compensation counter provided by the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0022] Combine the following Figures 1 to 3 The present invention describes a method for improving the scaling performance of an ultra-high precision fiber optic gyroscope based on frequency compensation.

[0023] The fiber optic inertial navigation system and the ultra-high precision fiber optic gyroscope generally use synchronous signals for data communication, that is, the fiber optic inertial navigation system sends a data receiving synchronous square wave signal, and the fiber optic gyroscope transmits the angle increment data pulse output by the gyroscope under the control frequency of the square wave signal. The fiber optic gyroscope with the angle increment data pulse output can be expressed as: Where: is the apparent scale of the fiber optic gyroscope on the fiber optic system, is the gyro output, is the angular increment data output by the gyroscope, is the gyro bias, is the angular increment of rotation and t is the time.

[0024] The fiber optic gyro scale can be expressed as: (1) Since the eigenfrequency of the fiber optic gyroscope It can be expressed as: (2) Where: is the transit time of light in the fiber ring, and n is the refractive index of the fiber.

[0025] Combining equation (1) and equation (2), we can get: (3) The ultra-high precision fiber optic gyroscope adopts a digital closed-loop solution, and each control signal is controlled by the crystal oscillator. Figure 1As shown in the figure: a is the bias square wave generated after the crystal oscillator clock is divided, b is the bias square wave, and c is the interferometer output signal.

[0026] Since the frequency of the crystal oscillator will change after being affected by temperature, generally, the temperature coefficient of ordinary crystal oscillators is generally 3×10 -5 about.

[0027] At the same time, the eigenfrequency of the fiber gyro Determined by formula (2), it is only related to the fiber length and fiber refractive index, and has nothing to do with the crystal oscillator clock. When the crystal oscillator clock frequency changes, the eigenfrequency constant.

[0028] The change of crystal frequency causes the change of bias square wave frequency, which in turn causes the number of sampling points in each interferometer output signal cycle to change. When the fiber optic inertial navigation system sends a data receiving synchronous square wave signal, the fiber optic gyroscope transmits the angle increment data pulse output by the gyroscope under the control frequency of the square wave signal. Due to the change of the number of points, the number of accumulated data pulses changes, that is, the accumulated value of the gyroscope in the synchronous square wave cycle time t changes, resulting in the fiber optic gyroscope The change in apparent scale of the gyroscope leads to the deterioration of the accuracy of the fiber-optic inertial navigation system.

[0029] Assume that the fiber length of the ultra-high precision fiber optic gyroscope is L =10000m, fiber refractive index n =1.5, then the eigenfrequency of the fiber ring is calculated f =1 / 2 τ =10kHz, Figure 1 The interval between the two interference signals in c is 100μs.

[0030] Assuming the frequency of the system synchronization square wave signal is 1000Hz, the frequency of the gyro output data is Hz, the period of output data ms, collected in each cycle f / 10 data, such as Figure 2 As shown. Due to the eigenfrequency of the gyroscope f remains unchanged, the cycle of the output data It will change with the crystal oscillator frequency, and the number of sampling points in each cycle will change.

[0031] Assume the temperature coefficient of the crystal is 3×10 -5 , then in the range of -40℃~+60℃, the crystal oscillator changes to 0.003 Hz. Assuming that the crystal oscillator frequency changes to 0.003 Hz faster, the frequency of the gyro output data is Hz becomes Hz, that is, after 1000 data output cycles, it can change by 3Hz.

[0032] Therefore, when the frequency of the system synchronous square wave signal is 1000Hz, 10 data are collected in each cycle when the crystal oscillator remains unchanged, that is, If the crystal oscillator speeds up by 3Hz after 1000 data output cycles, 0.03 more points of data are collected. That is, when 3 more points are collected, a total of 10×1000×100 data points are collected, and the change in the number of sampling points is 3×10 -6 The change of can bring about a change of 3ppm in the apparent scale of the system.

[0033] Therefore, even if the gyro's self-test calibration performance is 0.5ppm, theoretically 1nmile / 2160h can be achieved. However, due to the changes in the crystal oscillator frequency mentioned above, the apparent scale of the gyro when used in the system is on the order of 3ppm, and the system navigation accuracy will deteriorate by 6 times, that is, 1nmile / 360h.

[0034] In order to improve the ultra-high precision fiber optic gyroscope scaling performance, the present invention designs a frequency compensation counter in the digital processing unit to compensate for the change between the gyroscope data output and solution frequency and the fiber optic inertial navigation data receiving frequency. Figure 3 The frequency compensation counter is arranged in the FPGA modulation and demodulation unit of the fiber optic gyroscope, and is arranged after the AD converter of the fiber optic gyroscope, and receives the digital signal of the AD converter.

[0035] Frequency compensation counter compensation algorithm implementation: S1. Under the system synchronization signal cycle, calculate the number of data collection within the cycle; Through the frequency compensation algorithm: Method 1 The system receives the actual data collected and accumulates it to obtain the angular increment data output by the gyro ; Calculate the gyro angle increment data according to the actual data collection number. , in is the apparent scale of the fiber optic gyroscope on the fiber optic system, is the gyro bias, is the angular increment of rotation, t is the time, The number of data collected in step S1. Method 1 Eliminate The change in the number of data leads to the change in the accumulation of incremental data, which improves the gyroscope .

[0036] Method 2: The number of accumulated data sent to the inertial navigation system within a fixed period under the system synchronization signal cycle: If the crystal oscillator frequency becomes faster, resulting in more data collected under the synchronization signal cycle, the excess data will be removed to ensure the consistency of the data number, thereby ensuring The amount of accumulated data is consistent, ensuring that there is no excessive accumulation of data that will cause the gyroscope to If the crystal frequency is slow, resulting in a decrease in the number of data collected during the synchronization signal cycle, the last collected data will be used to make up for the less collected data to ensure the consistency of the number of data. The less data will be taken from the last collected data and the average value will be calculated. The corresponding less data will be compensated for according to the average value. This ensures The accumulated data volume is consistent, ensuring that there will be no gyroscope failure due to insufficient accumulated data. Become smaller.

[0037] Using the algorithm in method 1, the gyroscope self-test scale is 0.5ppm and the gyroscope apparent scale is 0.68ppm. The apparent scale performance has been improved by more than 4 times from the 3ppm apparent scale in the original test process.

[0038] Using the algorithm in method 2, the apparent scale of the gyroscope is about 1ppm, which is a 3-fold increase.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the scaling performance of an ultra-high precision fiber optic gyroscope based on frequency compensation, characterized in that: The following steps are involved: S1. Setting a frequency compensation counter in the digital processing unit: Under the system synchronization signal cycle, the number of data collection within the cycle is calculated; S2. Compensate for the change in the number of gyro data outputs and the number of solution frequencies and the number of fiber-optic inertial navigation data receiving frequencies; S3. Use the compensated data as the output data of the gyroscope.

2. The method for improving the scaling performance of an ultra-high precision fiber optic gyroscope based on frequency compensation according to claim 1, characterized in that: Step S2: Compensation for the change in the number of gyro data outputs and the number of solution frequencies and the number of fiber optic inertial navigation data receiving frequencies: Sending the number of data collected from the gyro output in each synchronization signal cycle to the system; The system receives the actual data collected and accumulates it to get the angular increment data output by the gyro. ; Calculate the gyro angle increment data according to the actual data collection number. ， in is the apparent scale of the fiber optic gyroscope on the fiber optic system, is the gyro bias, is the angular increment of rotation, t is the time, The number of data collected in step S1.

3. The method for improving the scaling performance of an ultra-high precision fiber optic gyroscope based on frequency compensation according to claim 1, characterized in that: Step S2: Compensation for the change in the number of gyro data outputs and the number of solution frequencies and the number of fiber optic inertial navigation data receiving frequencies: The accumulated data sent to the inertial navigation system within a fixed period under the system synchronization signal cycle: if the number of data collected during the synchronization signal cycle increases, the excess data will be removed to ensure the consistency of the data number; if the number of data collected during the synchronization signal cycle decreases, the last collected data will be used to make up for the less collected data to ensure the consistency of the data number.

4. The method for improving the scaling performance of an ultra-high precision fiber optic gyroscope based on frequency compensation according to claim 3, characterized in that: If the number of data collected during the synchronization signal cycle decreases, the method of using the last collected data to make up for the less collected data to ensure the consistency of the number of data is as follows: Take the reduced number of data from the last collected data and calculate their average value; The system is compensated for the corresponding decrease in the number of data according to the obtained average value.

5. The method for improving the scaling performance of an ultra-high precision fiber optic gyroscope based on frequency compensation according to claim 1, characterized in that: The frequency compensation counter is arranged in the FPGA modulation and demodulation unit of the fiber optic gyroscope.

6. A method for improving the scaling performance of an ultra-high precision fiber optic gyroscope based on frequency compensation according to any one of claims 1 to 5, characterized in that: The frequency compensation counter is arranged after the AD converter of the fiber optic gyroscope and receives the digital signal of the AD converter.

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