CN118089816A - PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation method and device - Google Patents
PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation method and device Download PDFInfo
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Abstract
The invention provides a closed loop amplitude comparison fiber bragg grating measurement demodulation method and device based on a PID algorithm, wherein the method comprises the following steps: scanning reflection and transmission spectrums of the fiber bragg grating sensors in advance, determining working point wavelengths of different sensors, and acquiring initial A C values of each FBG spectrum by adopting A C＝10·lg(IR/IT); splicing the time sequence of the current or voltage corresponding to the wavelength of any working point to form a tunable light source initial modulation signal; the tunable light source sequentially outputs different working point wavelengths according to the initial modulation signal of the tunable light source; performing spectrum detection on each FBG sensor, and adjusting the output wavelength of the tunable light source by using a PID control algorithm until the monitored A C value is restored to the initial A C value; and demodulating according to the change of the output wavelength of the tunable light source to obtain the change of the temperature strain of the FBG sensor, thereby realizing the high-speed measurement and demodulation of the closed-loop FBG. The invention can solve the problem that the measurement and demodulation precision of the closed loop slope auxiliary FBG based on the PID control algorithm is influenced by the change of output optical power or transmission loss.
Description
Technical Field
The invention relates to the technical field of optics, in particular to a closed-loop amplitude comparison fiber bragg grating measurement demodulation method and device based on a PID algorithm.
Background
Fiber Bragg Gratings (FBGs) are fiber sensors with fiber core refractive index periodically modulated, have the advantages of small volume, high sensitivity, multiple parameters and quasi-distributed multi-point measurement, and have been successfully applied to a plurality of fields such as optical communication, fiber lasers, fiber sensing and the like. Since 1998, the united states applied fiber bragg grating to monitoring of spaceflight aircraft, the development of fiber bragg grating sensing technology in the aerospace field has exceeded 20 years, and related researches on health monitoring of fiber bragg grating sensors in the aerospace field are carried out by space institutions such as NASA, ESA and JAXA in the united states, and mainly comprise response characteristics of the FBG sensors in space environment, packaging design of the FBG sensors, an airborne demodulation system, application verification tests and the like. Research in the aerospace field is relatively late, and is mainly focused on aspects of high-temperature-resistant FBG sensor development, FBG sensor sensitization packaging, feasibility verification and the like, and system consideration guided by practical application needs to be enhanced.
The fiber bragg grating sensor demodulation system is an important ring of on-line monitoring of FBG sensors in the aerospace field, and limited resources and severe working environments of an aircraft bring higher requirements on the volume, the quality, the power consumption and the environmental adaptability of the aircraft. Currently, the commonly used FBG sensor demodulation schemes comprise a spectrum imaging demodulation method, a tunable light source demodulation method, a filtering demodulation method, an interferometer demodulation method and the like, and the tunable light source based scheme is one of the main schemes applied in the aerospace field due to the good channel expansibility, high device stability, high integration and high precision. The tunable semiconductor laser scheme adopted by the European space agency is verified in satellite experiments, the output wavelength of the tunable semiconductor laser is controlled by adjusting the current of the tunable semiconductor laser, the reflected light intensity of the FBG sensor is recorded, then the reflected wavelength of the sensor is calculated by utilizing a peak detection algorithm, and finally the temperature and the strain value are obtained. The national Tianjin university proposes a fiber bragg grating demodulation system of a tunable FP scanning light source method, realizes the control of output wavelength by controlling FP voltage, realizes the spectral measurement of an FBG sensor to be measured, adopts an F-P etalon and acetylene gas for wavelength calibration, and enhances the environmental adaptability and demodulation precision of the demodulation system.
However, in order to acquire the FBG grating spectrum, the demodulation scheme based on the tunable light source scheme needs to perform finer spectrum scanning within the full spectrum range, and faces the contradiction that three indexes of spectrum measurement range, scanning precision and measurement time are mutually restricted, so that the performance of the fiber grating demodulation prototype is limited.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art.
According to one aspect of the invention, there is provided a closed-loop amplitude comparison fiber bragg grating measurement demodulation method based on a PID algorithm, the closed-loop amplitude comparison fiber bragg grating measurement demodulation method based on the PID algorithm comprising: scanning reflection and transmission spectrums of the fiber bragg grating sensors in advance, determining working point wavelengths of different sensors, and obtaining initial A C values of each FBG spectrum by adopting A C＝10·lg(IR/IT) according to the working point wavelengths, wherein I R and I T are respectively reflection light intensity and transmission light intensity corresponding to the working point wavelength lambda of the FBG spectrum; according to the determined working point wavelengths of different sensors, splicing the time sequence of current or voltage corresponding to any working point wavelength to form a tunable light source initial modulation signal; the tunable light source sequentially outputs different working point wavelengths according to the initial modulation signal of the tunable light source; performing spectrum detection on each FBG sensor, and adjusting the output wavelength of the tunable light source by using a PID control algorithm until the monitored A C value is restored to the initial A C value; and demodulating according to the change of the output wavelength of the tunable light source to obtain the change of the temperature strain of the FBG sensor, thereby realizing the high-speed measurement and demodulation of the closed-loop FBG.
Further according toRealizing PID control, wherein u (k) is the control quantity output by the PID controller; e (i) is a deviation value of the a C value from the initial a C value at the i-th calculation from the start of control; e (k) is the deviation value of the actual A C value and the initial A C value; e (k-1) is the deviation value of the last actual A C value and the initial A C value; k p is a proportionality coefficient; k i is an integral coefficient; k d is the differential coefficient.
According to another aspect of the invention, a closed-loop amplitude comparison fiber bragg grating measurement demodulation device based on a PID algorithm is provided, and the closed-loop amplitude comparison fiber bragg grating measurement demodulation device based on the PID algorithm realizes the closed-loop amplitude comparison fiber bragg grating measurement demodulation by adopting the closed-loop amplitude comparison fiber bragg grating measurement demodulation method based on the PID algorithm.
Further, the closed loop amplitude comparison fiber bragg grating measurement demodulation device based on the PID algorithm comprises: the optical signal output by the tunable light source module enters the optical coupler to realize multiplexing after passing through the optical isolator; the optical coupler is connected with a first port of the circulator, the FBG sensors are connected in series and then are respectively connected with a second port of the circulator and the photoelectric detection module, the photoelectric detection module is connected with a third port of the circulator, reflected light signals of the FBG sensors enter the photoelectric detection module after passing through the circulator, the transmitted light signals directly enter the photoelectric detection module, the photoelectric detection module is used for photoelectric conversion of the light signals, the data processing and PID control module is respectively connected with the photoelectric detection module and the wavelength tuning control module, the data processing and PID control module is used for acquiring a real-time A C value, a PID control algorithm is adopted for updating the output wavelength of the tunable light source module, meanwhile, parameters to be detected are acquired according to wavelength change, the wavelength tuning control module is connected with the tunable light source module, and the wavelength tuning control module is used for controlling and adjusting the tunable light source module according to the updated output wavelength of the tunable light source module to form a closed-loop FBG sensing system.
Further, the closed-loop amplitude comparison fiber bragg grating measurement demodulation device based on the PID algorithm further comprises a real-time display module, and the real-time display module is connected with the data processing and PID control module to output parameters to be measured.
Further, the tunable light source module realizes light source wavelength modulation through DBR, DFB, external cavity tunable laser or broadband light source+tunable narrow-band filter.
Further, the data processing and PID control module adopts a computer or an independent FPGA development board.
The technical scheme of the invention provides a PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation method and device, wherein the PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation method utilizes the logarithm of the corresponding power ratio of the FBG reflection spectrum and the transmission spectrum, namely the A C value, as a monitoring parameter, avoids demodulation errors caused by the change of the output power of a laser and the transmission loss of a system, improves the measurement accuracy of an FBG sensor, and simultaneously provides technical support for airborne high-performance FBG sensing monitoring compared with a double-slope auxiliary scheme without increasing measurement time. Compared with the prior art, the method can solve the problem that the existing closed loop slope auxiliary FBG measurement and demodulation accuracy based on the PID control algorithm is influenced by output optical power or transmission loss change.
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The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. It is evident that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
Fig. 1 is a schematic diagram of the working principle of a closed-loop amplitude comparison fiber grating measurement demodulation method based on a PID algorithm according to a specific embodiment of the present invention; wherein, fig. 1 (a) and fig. 1 (b) are respectively an initial reflection spectrum diagram, a transmission spectrum diagram and an a C value diagram of the fiber grating, fig. 1 (c) and fig. 1 (d) are respectively a reflection spectrum diagram, a transmission spectrum diagram and an a C value diagram of the fiber grating when the fiber grating is subjected to external strain or temperature change, and fig. 1 (e) and fig. 1 (f) are respectively a reflection spectrum diagram, a transmission spectrum diagram and an a C value diagram of the fiber grating after the demodulation method of the invention is adopted to control and recover;
FIG. 2 is a schematic diagram of the working principle of a closed-loop amplitude comparison fiber grating measurement demodulation device based on PID algorithm according to the embodiment of the invention;
FIG. 3 shows a schematic diagram of magnitude comparison FBG measurements based on a PID control algorithm provided in accordance with a specific embodiment of the invention.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the application, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective parts shown in the drawings are not drawn in actual scale for convenience of description. Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.
According to a specific embodiment of the present invention, there is provided a closed-loop amplitude comparison fiber bragg grating measurement demodulation method based on a PID algorithm, including: scanning reflection and transmission spectrums of the fiber bragg grating sensors in advance, determining working point wavelengths of different sensors, and obtaining initial A C values of each FBG spectrum by adopting A C＝10·lg(IR/IT) according to the working point wavelengths, wherein I R and I T are respectively reflection light intensity and transmission light intensity corresponding to the working point wavelength lambda of the FBG spectrum; according to the determined working point wavelengths of different sensors, splicing the time sequence of current or voltage corresponding to any working point wavelength to form a tunable light source initial modulation signal; the tunable light source sequentially outputs different working point wavelengths according to the initial modulation signal of the tunable light source; performing spectrum detection on each FBG sensor, and adjusting the output wavelength of the tunable light source by using a PID control algorithm until the monitored A C value is restored to the initial A C value; and demodulating according to the change of the output wavelength of the tunable light source to obtain the change of the temperature strain of the FBG sensor, thereby realizing the high-speed measurement and demodulation of the closed-loop FBG.
By applying the configuration mode, the PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation method is provided, the logarithm of the corresponding power ratio of the FBG reflection spectrum and the transmission spectrum, namely the A C value, is used as a monitoring parameter, demodulation errors caused by the change of the output power of a laser and the transmission loss of a system due to single-wavelength reflected power are avoided, the measurement precision of an FBG sensor is improved, and meanwhile, compared with a double-slope auxiliary scheme, the measurement time is not increased, and technical support is provided for airborne high-performance FBG sensing monitoring. Compared with the prior art, the method can solve the problem that the existing closed loop slope auxiliary FBG measurement and demodulation accuracy based on the PID control algorithm is influenced by output optical power or transmission loss change.
For the reflection spectrum curve of FBG, the maximum of intensity is theoretically located at the center wavelength, and the reflection spectrum can be expressed approximately as a Gaussian functionWhere λ is the reflection wavelength of the FBG, and λ B is the center wavelength of the reflection peak of the FBG. Δλ B is the full width at half maximum of the FBG reflection spectrum, and I 0 is the peak light intensity of the FBG reflection spectrum. The reflection spectrum and the transmission spectrum of the fiber bragg grating sensor can be obtained by two ends (a reflection end and a transmission end) of the sensor at the same time, the signal transmitted in the optical wave band with strong reflection signal is weak, the transmission signal in the wave band with weak reflection is strong, and therefore the transmission spectrum is complementary with the reflection spectrum in intensity.
Compared with the dual-slope reflected power monitoring, the FBG transmission spectrum is introduced to provide amplitude comparison power, as shown in fig. 1 (a) and fig. 1 (b), the output wavelength of the laser is firstly set at lambda 1, the reflected light intensity I R and the transmitted light intensity I T of the laser are simultaneously obtained by utilizing two photodetectors, the monitoring value a C of the PID is denoted as a C＝10·lg(IR/IT), the working wavelength is selected as long as the primary seat is positioned on one side of the FBG spectrum, and when lambda 1 is positioned at the full width at half maximum, the reflected power is equal to the value of the transmitted power a C and is 0; if the selected initial lambda 1 reflected power is not equal to the transmitted power, the value A C is not equal to 0, and only the initial A C value of the FBG sensor is needed to be recorded as the PID tracking value. The full width half maximum of the FBG spectrum can be selected with a single maximum dynamic tracking range.
When the fiber bragg grating is subjected to external strain or temperature change, the reflection spectrum and the transmission spectrum of the fiber are moved, and the A C value obtained by a monitoring point at the lambda 1 is changed; as shown in fig. 1 (c) and 1 (d), if the FBG spectrum shifts to a low wavelength, a 'C＞AC, and if the FBG reflection and transmission spectra shift to a high wavelength, a' C＜AC. Then, the output wavelength lambda '1 of the laser is regulated by a PID control algorithm, so that the value A C returns to the initial value again, as shown in fig. 1 (e) and fig. 1 (f), and at this time, the variation lambda' 1-λ1 of the output wavelength of the laser is the shift amount of the optical fiber FBG spectrum after the change, thereby realizing the rapid on-line wavelength demodulation of the optical fiber grating and forming a closed-loop FBG sensing system.
According to the analysis, in order to realize the closed-loop amplitude comparison fiber bragg grating measurement demodulation based on the PID algorithm, the reflection and transmission spectrums of the fiber bragg grating sensors are scanned in advance, the working point wavelengths of different sensors are determined, and an initial A C value of each FBG spectrum is obtained by adopting A C＝10·lg(IR/IT) according to the working point wavelengths, wherein I R and I T are respectively the reflection light intensity and the transmission light intensity corresponding to the working point wavelength lambda of the FBG spectrum; and according to the determined working point wavelengths of different sensors, splicing the time sequence of the current or voltage corresponding to any working point wavelength to form a tunable light source initial modulation signal.
Further, in the invention, the tunable light source sequentially outputs different working point wavelengths according to the initial modulation signal of the tunable light source; and performing spectrum detection on each FBG sensor, and adjusting the output wavelength of the tunable light source by using a PID control algorithm until the monitored A C value is restored to the initial A C value.
The PID control algorithm is used for obtaining the change of the A C value according to the output wavelength of the laser, and the adjustment quantity of the output wavelength of the laser is obtained by calculation in a PID control mode. As a specific embodiment of the present invention, according toRealizing PID control, wherein u (k) is the control quantity output by the PID controller, namely the output wavelength adjustment quantity of the tunable laser; e (i) is a deviation value of the a C value from the initial a C value at the i-th calculation from the start of control; e (k) is the deviation value of the actual A C value and the initial A C value; e (k-1) is the deviation value of the last actual A C value and the initial A C value; k p is a proportionality coefficient; k i is an integral coefficient; k d is the differential coefficient.
Further, in the invention, the change of the temperature strain of the FBG sensor is obtained by demodulation according to the change of the output wavelength of the tunable light source, so that the high-speed measurement and demodulation of the closed-loop FBG are realized.
The amplitude comparison fiber bragg grating measurement demodulation method based on the PID control algorithm utilizes the ratio of the reflected light power and the transmitted light power of the fiber bragg grating sensor at the detection wavelength to obtain an A C value as a monitoring parameter. The value of the FBG sensor A C is used for monitoring, the temperature/strain is used for causing the value of A C to change, the PID is used for controlling the output wavelength of the tunable light source, and the value of the FBG sensor A C is used for recovering the initial value, so that a closed loop is formed by the amplitude comparison fiber grating measuring system, and the temperature/strain can be measured and demodulated at high speed. Compared with the prior tunable light source FBG demodulation scheme, the full spectrum high-precision scanning and fiber grating spectrum fitting process of each measurement are avoided; compared with the existing closed-loop FBG demodulation scheme, the system is not influenced by system power fluctuation, the measurement time is not increased, and the performance and engineering practicability of the tunable light source FBG demodulation system are greatly improved on the basis of inheriting the high signal-to-noise ratio, miniaturization and low cost of the tunable light source demodulation scheme.
As shown in fig. 2, according to another aspect of the present invention, there is provided a closed-loop amplitude comparison fiber bragg grating measurement demodulation apparatus based on a PID algorithm, which implements closed-loop amplitude comparison fiber bragg grating measurement demodulation by using the closed-loop amplitude comparison fiber bragg grating measurement demodulation method based on the PID algorithm as described above; the PID algorithm-based closed loop amplitude comparison fiber bragg grating measurement demodulation device comprises: the optical signal output by the tunable light source module enters the optical coupler to realize multiplexing after passing through the optical isolator; the optical coupler is connected with a first port of the circulator, the FBG sensors are connected in series and then are respectively connected with a second port of the circulator and the photoelectric detection module, the photoelectric detection module is connected with a third port of the circulator, reflected light signals of the FBG sensors enter the photoelectric detection module after passing through the circulator, the transmitted light signals directly enter the photoelectric detection module, the photoelectric detection module is used for photoelectric conversion of the light signals, the data processing and PID control module is respectively connected with the photoelectric detection module and the wavelength tuning control module, the data processing and PID control module is used for acquiring a real-time A C value, a PID control algorithm is adopted for updating the output wavelength of the tunable light source module, meanwhile, parameters to be detected are acquired according to wavelength change, the wavelength tuning control module is connected with the tunable light source module, and the wavelength tuning control module is used for controlling and adjusting the tunable light source module according to the updated output wavelength of the tunable light source module to form a closed-loop FBG sensing system.
With the adoption of the configuration mode, as shown in fig. 3, the working wavelength lambda 1,λ2,…λN of different FBG sensors and the corresponding initial A C value A C_FBG1,AC_FBG2,…AC_FBGN thereof are obtained by scanning the full spectrum in advance, the wavelength tuning control module sequentially outputs control currents or voltage sequences of N sensor wavelengths at the beginning of measurement, the laser can be tuned in time to sequentially output the wavelengths of the N sensors, the N FBG sensors are detected, when the spectrum of one FBG sensor moves, the corresponding wavelength control parameters are adjusted, and the real-time A C value is tracked to the initial A C value to complete the on-line demodulation of the FBG sensors.
Further, in the invention, the closed-loop double-slope auxiliary fiber bragg grating measurement demodulation device based on the PID control algorithm further comprises a real-time display module, wherein the real-time display module is connected with the data processing and PID control module to output parameters to be measured, such as temperature or strain and the like.
As a specific embodiment of the present invention, the tunable light source module is used as an FBG spectrum detection light source, and the tunable light source module can realize light source wavelength modulation through DBR, DFB, external cavity tunable laser or broadband light source+tunable narrow band filter; different wavelength tuning control, such as current, voltage, etc., is adopted according to different light source modules; the data processing and PID control module can be realized by a computer or by an independent FPGA development board.
The invention provides a high-speed measuring and demodulating scheme for the tunable light source FBG measuring system, does not need the time-consuming full-spectrum high-precision scanning and FBG spectrum fitting process, and compared with the double-slope scheme, the method has the advantages that the measuring time is not additionally increased on the basis of avoiding the measuring error caused by system power fluctuation, and the method has the following advantages:
1) The system can realize high-speed measurement and online demodulation of the FBG sensor, and real-time tracking of the value of the reflection and transmission spectrum A C of the FBG is realized through closed-loop feedback control, so that the processes of full-spectrum high-precision scanning and FBG spectrum fitting of the existing FBG measurement are avoided, the reflection peak value movement of the FBG sensor can be determined according to the output wavelength of the adjustable light source, and the high-speed measurement and online demodulation of data are realized;
2) The system can have the measuring capability of multiple channels, multiple measuring points and large dynamic range, can inherit the advantages of low cost, miniaturization, high signal-to-noise ratio and the like of a tunable laser scheme, and provides a brand new high-performance solution for high-performance fiber bragg grating measurement and demodulation; the multichannel monitoring can be realized through the optical fiber beam splitters and the multichannel detectors; the method comprises the steps of acquiring measurement spectrums of fiber bragg grating sensors of a channel to be detected in advance, and sequentially acquiring the change of values of different sensors A C according to the number of spectrums and corresponding wavelengths of the spectrums, so that multi-measuring-point quasi-distributed detection can be realized; the PID parameters are regulated, so that the value of the FBG sensor A C can be tracked quickly, and the large-scale measurement is realized;
3) The system has higher anti-interference capability, the PID control algorithm has good adaptability and stronger robustness, meanwhile, the A C value is obtained by the ratio of the reflected light to the transmitted light monitoring power, the demodulation error caused by the change of the laser output power and the transmission loss of the demodulation system is avoided, compared with the double-slope closed-loop monitoring scheme, the system measurement time is not increased, and the FBG sensing system has higher performance and engineering practicability.
In summary, the invention provides a method and a device for measuring and demodulating a closed-loop amplitude comparison fiber bragg grating based on a PID algorithm, which utilize the logarithm of the corresponding power ratio of the FBG reflection spectrum and the transmission spectrum, namely the A C value, as a monitoring parameter, avoid demodulation errors caused by the change of the output power of a laser and the transmission loss of a system when single-wavelength reflected power is changed, improve the measuring precision of an FBG sensor, and simultaneously provide technical support for airborne high-performance FBG sensing and monitoring compared with a double-slope auxiliary scheme without increasing measuring time. Compared with the prior art, the method can solve the problem that the existing closed loop slope auxiliary FBG measurement and demodulation accuracy based on the PID control algorithm is influenced by output optical power or transmission loss change.
In addition, the terms "first", "second", etc. are used to define the components, and are only for convenience of distinguishing the corresponding components, and the terms have no special meaning unless otherwise stated, and therefore should not be construed as limiting the scope of the present invention.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. The PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation method is characterized by comprising the following steps of:
Scanning reflection and transmission spectrums of the fiber bragg grating sensors in advance, determining working point wavelengths of different sensors, and obtaining initial A C values of each FBG spectrum by adopting A C＝10·lg(IR/IT) according to the working point wavelengths, wherein I R and I T are respectively reflection light intensity and transmission light intensity corresponding to the working point wavelength lambda of the FBG spectrum;
According to the determined working point wavelengths of different sensors, splicing the time sequence of current or voltage corresponding to any working point wavelength to form a tunable light source initial modulation signal;
The tunable light source sequentially outputs different working point wavelengths according to the initial modulation signal of the tunable light source;
Performing spectrum detection on each FBG sensor, and adjusting the output wavelength of the tunable light source by using a PID control algorithm until the monitored A C value is restored to the initial A C value;
and demodulating according to the change of the output wavelength of the tunable light source to obtain the change of the temperature strain of the FBG sensor, thereby realizing the high-speed measurement and demodulation of the closed-loop FBG.
2. The PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation method as claimed in claim 1, wherein the method is based on the following steps ofRealizing PID control, wherein u (k) is the control quantity output by the PID controller; e (i) is a deviation value of the a C value from the initial a C value at the i-th calculation from the start of control; e (k) is the deviation value of the actual A C value and the initial A C value; e (k-1) is the deviation value of the last actual A C value and the initial A C value; k p is a proportionality coefficient; k i is an integral coefficient; k d is the differential coefficient.
3. The PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation device is characterized in that the PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation device adopts the PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation method to realize closed-loop amplitude comparison fiber bragg grating measurement demodulation.
4. The PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation apparatus according to claim 3, wherein the PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation apparatus comprises: the optical fiber coupler comprises a tunable light source module, an optical isolator, an optical coupler, a circulator, a plurality of FBG sensors, a photoelectric detection module, a data processing and PID control module and a wavelength tuning control module, wherein an optical signal output by the tunable light source module enters the optical coupler after passing through the optical isolator to realize multiplexing; the optical coupler is connected with a first port of the circulator, the FBG sensors are connected in series and then are respectively connected with a second port of the circulator and the photoelectric detection module, the photoelectric detection module is connected with a third port of the circulator, reflected light signals of the FBG sensors enter the photoelectric detection module after passing through the circulator, transmitted light signals directly enter the photoelectric detection module, the photoelectric detection module is used for photoelectric conversion of the light signals, the data processing and PID control module is respectively connected with the photoelectric detection module and the wavelength tuning control module, the data processing and PID control module is used for acquiring a real-time A C value, a tunable light source module output wavelength is updated by adopting a PID control algorithm, meanwhile, parameters to be detected are acquired according to wavelength change, the wavelength tuning control module is connected with the tunable light source module, and the wavelength tuning control module is used for controlling and adjusting the tunable light source module according to the updated output wavelength of the tunable light source module to form a closed loop sensing system.
5. The PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation apparatus according to claim 4, further comprising a real-time display module, wherein the real-time display module is connected with the data processing and PID control module to output parameters to be measured.
6. The PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation apparatus according to claim 4, wherein the tunable light source module implements light source wavelength modulation through DBR, DFB, external cavity tunable laser, or broadband light source+tunable narrowband filter.
7. The PID algorithm-based closed-loop amplitude comparison fiber bragg grating measurement demodulation device of claim 4,
The data processing and PID control system is characterized in that the data processing and PID control module adopts a computer or an independent FPGA development board.
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