CN113804351B

CN113804351B - Detection system for pressure response and pressure distribution in spiral pipeline

Info

Publication number: CN113804351B
Application number: CN202010549144.8A
Authority: CN
Inventors: 黄爱武; 王洪涛
Original assignee: Weifang Jiateng Hydraulic Technology Co ltd
Current assignee: Weifang Jiateng Hydraulic Technology Co ltd
Priority date: 2020-06-16
Filing date: 2020-06-16
Publication date: 2024-03-22
Anticipated expiration: 2040-06-16
Also published as: CN113804351A

Abstract

The application discloses a detection system for pressure response and pressure distribution in a spiral pipeline, which is used for detecting pressure and pressure response millisecond precision. The system comprises: the light source module comprises a broadband light source and a polarized light source; the light source control module is used for controlling the light source module to periodically emit broadband light signals or emit polarized light signals with preset incidence angles; the fiber bragg grating sensing detection module comprises a fiber bragg grating pressure sensor group; the data acquisition module is used for acquiring the central wavelength fluctuation of broadband optical signals reflected by one side of the fiber bragg grating group in each grating pressure sensor or acquiring Stokes parameters of polarized optical signals transmitted by the other side of the fiber bragg grating group in the respective characteristic grating stop band wavelength range of each grating pressure sensor; the computer system is used for controlling the polarized light source in the light source module to periodically emit polarized light signals with different characteristic frequencies or controlling the broadband light source to emit periodic broadband light signals through the light source control module.

Description

Detection system for pressure response and pressure distribution in spiral pipeline

Technical Field

The application relates to the technical field of hydraulic pressure, in particular to a detection system for pressure response and pressure distribution in a spiral pipeline.

Background

Along with popularization and application of the hydraulic system, the effect of the hydraulic pipeline is gradually expanded from the multifunctional and multipurpose directions of only reliably transmitting kinetic energy, namely radiating heat to the auxiliary hydraulic system, absorbing hydraulic pulsation in an auxiliary mode, storing energy in an auxiliary mode and the like.

When the hydraulic pipeline is designed, the hydraulic pipeline can be set into a spiral pipe structure, the impact resistance of the spiral pipe to the propagation of hydraulic impact pulsation along the pipeline is better than that of a straight pipe, the hydraulic pipeline has certain energy storage effect and timely release characteristic, and the hydraulic pipeline can play a role in peak clipping and valley filling.

At present, when pressure in a spiral pipe type hydraulic pipeline is detected, a method for radially opening a pressure detection process hole in the pipeline and installing a pressure sensor probe on the radial side wall of the pipeline is generally adopted.

However, this method has a problem: first, destroy the sidewall structure of the pipeline; secondly, the radial sensor probe breaks the laminar flow form of the inner wall liquid flow, and increases the disturbance in the liquid flow; thirdly, the flow rates of the inner side and the outer side of the spiral pipeline are different, the pressure states are different, and the pressure distribution and the change rule in the pipeline are difficult to accurately measure by adopting a method of a fixed pressure sensor probe.

In addition, most of the liquid pressure measurement in the pipeline is performed by utilizing the fiber bragg grating principle, but when the fiber bragg grating pressure sensor is used for pressure measurement, the problem of small bearing and small pressure measurement range exists. For this reason, currently, the cantilever beam amplification principle is generally adopted to package the grating pressure sensor so as to solve the problem of small bearing of the sensor. But this also causes a problem of an increase in the sensor volume; and the problem that the measuring pressure range of the sensor is smaller cannot be solved by packaging the sensor, namely the measuring range of the sensor still cannot meet the actual requirement.

In the prior art, two main methods for measuring pressure by using fiber bragg gratings are: firstly, a certain approximate linear relation can be established between the wavelength of the fiber bragg grating and the physical quantity to be measured, and a corresponding pressure value is converted from a drift value of the wavelength caused by the change of the physical quantity to be measured by calibrating a linear coefficient in a linear range. For example, when the optical fiber optical shed is subjected to external fields (stress fields, temperature fields and the like), the grating period or the effective refractive index of the optical fiber optical shed can be changed to cause the drift of the reflection (or transmission) wavelength of the grating, and most of the optical fiber grating sensors in the grating sensing commonly used at present belong to the category; secondly, the polarization characteristics of the fiber bragg grating can establish a linear relation with the physical quantity to be measured, the polarization characteristics change along with the change of the physical quantity to be measured, so that the resonance wavelength of the fiber bragg grating is split under the pressure load condition, the external pressure is detected through the offset of the central wavelengths of the amplitude spectrums of the x-polarized light and the y-polarized light, but when the method encounters the condition of smaller pressure, the difference of the central wavelengths of the two eigenmodes is hardly perceived by the total amplitude spectrum, and the detection is difficult.

In summary, because the fiber bragg grating sensor has high sensitivity, no matter whether the fiber bragg grating sensor uses the grating center wavelength drift amount or uses the birefringence detection method caused by the optical fiber elliptical deformation, a low-pressure range can be detected only, and a relative high-pressure range can be detected only, so that the measuring range of the measured pressure is greatly limited, and the practical requirement of engineering hydraulic machinery cannot be met by the lower limit or the upper limit of the pressure which can be detected by the existing fiber bragg grating sensor.

With the improvement of the performance of spectrometers, for example, a novel spectrometer which is controlled by a photon detector (CCD) and a computer appears in the last decade, the spectrometer integrates information acquisition, processing and storage functions. And avoid and save darkroom processing and a series of tedious processes afterwards, measure the work, make the traditional spectroscopic technique take place radical change, has improved work efficiency greatly: the method has the advantages of accurate and rapid measurement, convenience, high sensitivity, quick response time and high spectral resolution, is widely used in almost all spectral measurement, analysis and research works, and is particularly suitable for detecting weak signals and transient signals.

Therefore, by utilizing the prior art and the nerve sensing principle of the fish 'interline' for the liquid pressure, and by virtue of the development of the current fiber grating technology, the complementarity of two outstanding characteristics of different measuring ranges of the fiber grating along the longitudinal direction and the radial direction along with the pressure change is comprehensively utilized, and according to a bionic fish-type fiber grating sensor, a pipeline nondestructive testing system capable of realizing high-precision pressure response and pressure distribution in a hydraulic pipeline is needed to be used for high-frequency response pressure detection in the pipeline with the oil pressure millisecond level and below and large-range detection of the internal oil pressure without damage of a multipoint pipeline wall so as to promote the deep research and optimization of the hydraulic pipeline.

Disclosure of Invention

The embodiment of the application provides a detection system for pressure response and pressure distribution in a spiral pipeline, which is used for realizing detection of pressure distribution in a hydraulic pipeline by a bionic fish-shaped fiber bragg grating pressure sensor group placed in series in the spiral pipeline, expanding the range of a pressure detection range of a fiber bragg grating through the difference of two sides of a fish-shaped packaging structure, and realizing detection of pressure response with accuracy of millisecond level and below through a sensor at the head end and the tail end and a computer detection system.

The embodiment of the application provides a detection system of pressure response and pressure distribution in spiral pipeline, includes:

the light source module comprises a broadband light source and a polarized light source;

the light source control module is used for controlling the light source module to periodically emit broadband light signals or emit polarized light signals with preset incidence angles;

the fiber bragg grating sensing detection module comprises a fiber bragg grating pressure sensor group; the fiber bragg grating pressure sensor group is a fiber bragg grating pressure sensor; the fiber bragg grating pressure sensor group comprises a first grating pressure sensor arranged at the inlet of the hydraulic pipeline, a second grating pressure sensor arranged at the outlet of the hydraulic pipeline and a third grating pressure sensor group arranged inside the hydraulic pipeline;

The data acquisition module is used for acquiring the preset central wavelength fluctuation of broadband optical signals reflected by one side of the fiber bragg grating group in each grating pressure sensor or acquiring Stokes parameters of polarized optical signals transmitted by the other side of the fiber bragg grating group in the respective characteristic grating stop band wavelength range of each grating pressure sensor;

the computer system is used for controlling the polarized light source in the light source module to periodically emit polarized light signals with different characteristic frequencies, or controlling the broadband light source to emit periodic broadband light signals through the light source control module, determining the pressure response time of the hydraulic pipeline according to the counting and the emitting period of the periodic light signals, and determining the pressure of a preset position in the hydraulic pipeline according to the central wavelength fluctuation of the broadband light signals reflected by one side of the fiber bragg grating groups in each grating pressure sensor or according to the Stokes parameters of the polarized light signals transmitted by the other side of the collected fiber bragg grating groups.

In one example, grating characteristic values among the grating pressure sensors in the first grating pressure sensor, the second grating pressure sensor and the third grating pressure sensor group are different, and the first grating pressure sensor, the second grating pressure sensor and the third grating pressure sensor group are arranged in a hydraulic pipeline in series;

Each grating pressure sensor is a bionic fish-shaped grating pressure sensor, each bionic fish-shaped grating pressure sensor comprises two fish-bone-shaped metal sheets which are arranged in a mutually sub-symmetrical mode, the fish-bone-shaped metal sheets which are arranged in the sub-symmetrical mode refer to the fact that the thicknesses or structures of the metal sheets near the fish-line lines on the left side and the right side of the bionic fish-shaped sensor are not identical, so that structural rigidity differences are caused, the side where the metal sheets with high structural rigidity are located is called the positive side, the side where the metal sheets are located on the other side where the metal sheets are located is called the negative side, each side wall of each metal sheet is provided with two optical fibers along the central axis, the two optical fibers are symmetrically arranged relative to the metal sheets, a grating is recorded on each optical fiber in the middle of each metal sheet, and characteristic values of the gratings in each grating pressure sensor are identical.

In one example, the system includes four optical fibers forming two sets of optical paths on both sides of each grating pressure sensor, one set of optical paths reflecting a broadband periodic optical signal; the other group of light paths transmit frequency modulation polarized light signals, wherein the polarized light signals are polarized light signals with specific frequencies corresponding to gratings of the grating pressure sensor to be detected; the frequency modulation polarized light signals are polarized light signals which are emitted by the light source periodically according to a certain preset sequence.

In one example, the light source includes a broad spectrum light source and a tunable laser; the broad spectrum light source comprises a tungsten filament lamp, a hernia lamp and the like.

In one example, the data acquisition module includes a spectrometer for accepting a broad spectrum light source signal and a polarization light analyzer for accepting polarized light emitted by a tunable laser; the spectrometer is used for analyzing the light spectrum by adopting a photon detector under the control of the computer system, and the photon detector is arranged in a detection area of the spectrometer in a linear array or an area array.

In one example, the computer system is specifically configured to determine, from a pre-stored data table, an ambient pressure value outside the grating pressure sensor corresponding to a difference Δλ (T) between two wavelength offsets of the optical signal reflected by the grating group within the same period by the grating pressure sensor; and determining the ambient pressure value outside the grating pressure sensor corresponding to the two ternary arrays from a pre-stored data table by the two ternary arrays corresponding to Stokes parameters of polarized light transmitted by the two gratings in the grating group of the grating pressure sensor Yang Ceguang;

And controlling the light source or the light source control module to periodically emit broadband light signals to the cathode-side optical grating group of the grating pressure sensor or periodically emit polarized light signals with different specific frequencies in a preset sequence to the grating pressure sensor Yang Ceguang optical grating group; the period of the negative side light signal is millisecond or less, and the period of the positive side light signal is the shortest period detected by Stokes parameters of the positive side light signal birefringent polarized light; the shortest period detected is determined by the shortest time taken for the demodulator to demodulate stokes parameters s1, s2 and s3 of the polarized light signal.

In one example, the computer system determines a pressure response time of the helical piping based on t=tsx (n 2-n 1); wherein t represents pressure response time, and the pressure response time comprises the time length when the pulsation impact sent by the hydraulic element at one end of the spiral pipeline reaches the other end of the spiral pipeline; the pulsation impact sent by the hydraulic element indicates that the hydraulic element at the pipeline end is opened or the pressure peak value of the instantaneous extrusion of the hydraulic element to the liquid in the pipeline caused by load impact exceeds the preset pressure maximum value; n1 represents periodic optical signal counting when a first grating pressure sensor at one end of the spiral pipeline detects pulse pressure or periodic optical signal counting when the first grating pressure sensor detects pulse impact sent by a hydraulic element at the pipeline end; n2 represents a periodic optical signal count when the second grating pressure sensor corresponding to n1 detects the pulse pressure, or the second fiber grating pressure sensor detects a periodic optical signal count of pulse impact sent by a hydraulic element at the pipeline end nearest to the n1 count, and T represents a transmitting period of the periodic optical signal, wherein the transmitting period is in a millisecond level or a time level below the millisecond level; the periodic optical signal count is the count of the optical signal period by a computer, and n2 and n1 count base points are uniformly determined by the computer.

In one example, the system further comprises an auxiliary pressure calibration workstation; the auxiliary pressure calibration workstation is connected with the computer system; the auxiliary pressure calibration workstation comprises a hydraulic pipeline for calibration, a hydraulic workstation and an external pressure detection system; the hydraulic pipeline for calibration is provided with an optical fiber sealing structure; the hydraulic working station controls the opening and closing of an oil way in the hydraulic pipeline for calibration or the gradual pressurization and gradual depressurization according to a control instruction from the computer system; and the external pressure detection system is used for detecting the pressure in the hydraulic pipeline for calibration, establishing a corresponding relation between the pressure and the detection signals of the calibrated fiber grating pressure sensor and the system, and obtaining the calibration of the fiber grating pressure sensor and the system.

In one example, the two periodic optical signals reflected by the negative side optical grating group are periodic broadband optical signals or polarized optical signals of the sequential characteristic spectrum group are emitted according to the period; the serial characteristic spectrum group is a polarized light signal with different corresponding grating characteristic frequencies among the serial grating pressure sensors, and the serial characteristic spectrum group is used for emitting the formed polarized light series spectrum at the same time interval period according to a preset ordering sequence of a computer system; the polarized spectrum series is circularly emitted by the computer system through controlling the light source module.

The embodiment of the application provides a detection system of pressure response and pressure distribution in a spiral pipeline, which at least comprises the following beneficial effects:

1. the sensor is used for packaging the fiber grating bionic fish type, so that the staged collection of the axial signal and the radial elliptical deformation information of the fiber grating is realized, the problem that the traditional fiber grating sensor is difficult to measure high pressure and low pressure simultaneously is solved, and the pressure detection range is enlarged;

2. the light source emits periodic light signals lower than millisecond level, and the light signal period count among the detection signals realizes the millisecond level accurate measurement of pressure response;

3. the optical signal period counting among the detection signals is not limited by the data transmission speed and is not influenced by the integral hysteresis of the acquisition signals, so that the accuracy and precision of the response detection result of the pressure of the hydraulic pipeline are improved;

4. according to streamline and floating effects of the sensor, the liquid middle part in the hydraulic pipeline can be built in to damage the pipeline wall surface, leakage points of pipeline wall process holes are reduced, and pipeline wall nondestructive detection of pressure distribution in the spiral pipe is realized;

5. the full information calibration data table which is carried out by utilizing the strong computing power of the computer solves the problem of small information collecting range of the conventional fiber bragg grating sensor line, and enlarges the collecting coverage range of the pressure signal.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation to the application. In the drawings:

FIG. 1 is a schematic diagram of a detecting system for pressure response and pressure distribution in a spiral pipeline according to an embodiment of the present application;

FIG. 2 is a schematic diagram of a cross-sectional structure of a fiber grating sensor according to an embodiment of the present disclosure;

fig. 3 is a schematic view of an expanded structure of a sensor according to an embodiment of the present disclosure, wherein the expanded structure corresponds to an angle of a metal sheet on a female side;

fig. 4 is a schematic view of an expanded structure of a sensor according to an embodiment of the present disclosure, where the expanded structure corresponds to an angle of a male side metal sheet;

fig. 5 is a schematic perspective view of a sensor skeleton portion according to an embodiment of the present application.

Reference numerals:

1 a light source module, 11 a broad spectrum light source, 12 a tunable laser,

2 a light source control module, 21 a broad spectrum light source switch module, 22 an electric polarization controller,

3 a sensor optical signal incidence module,

4 optical fibers, 41 traction ropes, 42 torsion ropes,

5 fiber grating pressure sensor group, 51 grating pressure sensor, 511 positive side metal sheet, 512 negative side metal sheet, 513 groove, 514 reinforcing rib groove, 515 air bag, 516 supporting part, 517 filler

6 hydraulic pipeline, 61 optical cable

7 auxiliary pressure calibration work stations, 71 hydraulic work stations, 72 hydraulic work stations, 73 external traditional pressure detection systems,

8 data acquisition module, 81 spectrum analyzer, 82 demodulator, 83 spectrum comparison coupler,

9 computer system.

Detailed Description

For the purposes, technical solutions and advantages of the present application, the technical solutions of the present application will be clearly and completely described below with reference to specific embodiments of the present application and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

Currently, many methods for pressure sensing are available, including piezoresistive-based sensing, fiber optic pressure-based sensing, fiber optic grating wavelength shift-based sensing, and the like. The piezoresistive sensing method generally converts pressure into resistivity or elastic device displacement by using a pressure sensitive device, and is limited by a circuit, so that the response speed is too slow to realize real-time measurement. The sensing method based on the wavelength shift of the fiber bragg grating is to perform temperature sensing and stress sensing by utilizing the wavelength shift. The measuring principle is mainly that the Bragg wavelength is shifted due to the change of the refractive index or the grating period of the fiber grating caused by the change of external parameters, and the sensing purpose is achieved by measuring the offset. This approach has obvious cross-sensitivity problems, namely: since both temperature and stress cause wavelength shift and affect the pressure detection result, a difference in wavelength change due to the reverse deformation of the diaphragm in the same temperature field is generally used as a pressure measurement signal. In this method, the pressure to be detected is generally not high, and the sensitivity of the bare grating to radial pressure is very low, so that the encapsulation of the bare grating is generally required to improve the sensitivity and the pressure detection range. However, no matter how the elastic modulus of the package is improved, the method of measuring the center wavelength shift is still difficult to adapt to the situation of measuring high voltage.

Fig. 1 is a schematic structural diagram of a pipe wall nondestructive testing system of a hydraulic pipeline, which is provided in the embodiment of the present application, and specifically includes a light source module 1, a light source control module 2, a sensor optical signal incidence module 3, an optical cable 61, a fiber bragg grating pressure sensor group 5, a hydraulic pipeline 6, an auxiliary pressure calibration workstation 7, a data acquisition module 8, and a computer system 9.

In fig. 1, the optical cable 61 is disposed in the hydraulic line 6, and the direction indicated by the arrow in the hydraulic line 6 is the conduction direction of the optical wave along the optical cable 61. The left side of the hydraulic pipeline 6 is an inlet, and the right side is an outlet.

The light source module 1 may include a broad spectrum light source 11 and a tunable laser 12, the broad spectrum light source 11 may emit a broadband light signal, and the tunable laser 12 may emit polarized light waves having different center wavelengths. The wide-spectrum light source comprises a tungsten filament lamp, a hernia lamp and the like, so that the sufficient frequency width and the light intensity are ensured, and meanwhile, the cost is low.

The light source control module 2 is connected with the light source module 1, the broad spectrum light source switch module 21 can control the broad spectrum light source 11 to emit a periodic broadband light signal with a period of microsecond or shorter, and the electric polarization controller 22 can modulate the light wave with a specific wavelength emitted by the tunable laser into a polarized light signal with a preset incident angle. The computer system forms the frequency modulation polarized light signals by controlling the tunable laser in the light source module 1 to periodically emit polarized light signal strings with different specific frequencies corresponding to the fish-shaped sensor strings.

The sensor optical signal incidence module 3 is configured to ensure an incidence angle of polarized light in the optical fiber on the sun side of the optical cable 61 by the polarized light source, or ensure synchronization of an incidence light cycle in the optical fiber on the shade side of the optical cable 61 by the broadband periodic light source.

The optical cable 61 is composed of two optical fibers on the male side and two optical fibers on the female side of the fish-shaped sensor and a traction rope 41 and a torsion-resistant rope 42 for transmitting optical signals and connecting the fish-shaped sensors in series.

For convenience of description, in this embodiment, the grating pressure sensor at the inlet of the hydraulic pipeline 6 is referred to as a first grating pressure sensor, the grating pressure sensor at the outlet of the hydraulic pipeline 6 is referred to as a second grating pressure sensor, and other grating pressure sensors except the first grating pressure sensor and the second grating pressure sensor in the fiber grating pressure sensor group 5 are collectively referred to as a third grating pressure sensor group. Wherein, grating characteristic values of each grating pressure sensor in the first grating pressure sensor, the second grating pressure sensor and the third grating pressure sensor are different, and each grating pressure sensor in the first grating pressure sensor, the second grating pressure sensor and the third grating pressure sensor group is arranged in the hydraulic pipeline 6 in series.

The auxiliary pressure calibration station 7 includes a hydraulic station 71, a hydraulic station 72, and an external conventional pressure detection system 73.

The auxiliary pressure calibration workstation 7 can control the opening and closing of the pressure in the hydraulic pipeline through the hydraulic workstation 71 and the hydraulic workstation 72, monitor the grating pressure sensor in the hydraulic pipeline through the external pressure detection system 73, establish the corresponding relation between the pressure and the calibration grating pressure sensor and the system detection signal, and complete the calibration of the fiber grating pressure sensor and the system so as to form a corresponding calibration data table and store the corresponding calibration data table, so that a subsequent computer system can determine the pressure detection value according to the pre-stored data table.

The data acquisition module 8 may include a spectrum analyzer 81, a demodulator 82, and a spectrum comparison coupler 83. The data acquisition module 8 is connected with the fiber bragg grating pressure sensor group 5 and is used for acquiring the central wavelength fluctuation of the periodic broadband optical signals reflected by each grating pressure sensor to the cathode side optical grating group or Stokes parameters s1, s2 and s3 of the transmitted polarized optical signals in the grating stop band wavelength range.

The computer system 9 is used to receive external inputs or feedback inputs from the measurement system, to control the wavelength of the tunable laser, and to adjust the motorized polarization controller 22 to linearly polarize the incident light with an azimuthal angle of 45 degrees. Also, the auxiliary pressure calibration workstation 7 may be connected to a computer system 9 to obtain uploaded calibration pressure data.

Specifically, the implementation method of the pressure detection based on the bionic fish-type grating pressure sensor is as follows:

in this embodiment of the present application, each of the first grating pressure sensor, the second grating pressure sensor, and the third fiber grating pressure sensor group is a pressure sensor. As shown in fig. 2 to 5, each grating pressure sensor 51 is a bionic fish-shaped pressure sensor, and the bionic fish-shaped pressure sensor includes two fish-bone-shaped metal sheets which are arranged in a sub-symmetrical manner, wherein the sub-symmetrically arranged fish-bone-shaped metal sheets refer to metal sheets near the line of the fish line on the left side and the right side of the bionic fish-shaped sensor, and the thicknesses or structures of the metal sheets are not identical, so that structural rigidity differences are caused, wherein the side of the metal sheet with high structural rigidity is called a male side, the corresponding other side is called a female side, and the corresponding metal sheets can be respectively called a male side metal sheet 511 and a female side metal sheet 512. The concave side metal sheet is provided with a convex or concave reinforcing rib groove 514 along the upper side and the lower side of the grating, and the thickness of the concave side metal sheet is larger than that of the concave side metal sheet, so that the deformation resistance of the concave side metal sheet is higher than that of the concave side metal sheet. The side wall of each metal sheet is provided with two optical fibers along the central axis respectively, the two optical fibers are symmetrically arranged relative to the metal sheet, and the optical fibers in the middle of the metal sheet are respectively inscribed with a grating, and the characteristic values of the gratings in the grating pressure sensors are identical.

The fiber bragg grating pressure sensor group 5 can be formed by connecting a plurality of fiber bragg grating pressure sensors in series, wherein each fiber bragg grating pressure sensor can be connected in series through a fiber bragg grating adapter, and can also be prefabricated on four fibers, a traction rope and a torsion-resistant rope in sequence.

The first grating pressure sensor is arranged at the inlet of the hydraulic pipeline 6 and is used for reflecting light waves with the characteristic wavelength of the first fiber bragg grating in the optical wave group, and the second grating pressure sensor is arranged at the outlet of the hydraulic pipeline 6 and is used for reflecting light waves with the characteristic wavelength of the second fiber bragg grating in the optical wave group. Wherein the wavelength of the light waves reflected by the first grating pressure sensor is different from the wavelength of the light waves reflected by the second grating pressure sensor.

The third grating pressure sensor group comprises a plurality of grating pressure sensors which are arranged at preset positions in the hydraulic pipeline and are connected with the computer system 9, and the computer system 9 records the central wavelength fluctuation of the periodic broadband optical signal reflected by one side of the fiber bragg grating group in each grating pressure sensor or the Stokes parameter of the polarized optical signal transmitted by the other side of the fiber bragg grating group in the respective characteristic grating stop band wavelength range of each grating pressure sensor so as to determine the pressure of the corresponding preset position in the hydraulic pipeline. The number of grating pressure sensors in the third grating pressure sensor group and the preset positions of the grating pressure sensors can be set according to needs, and the maximum number is limited by the ability of different systems to receive optical signals, for example, not more than 18, etc., which is not limited in the application.

By arranging the grating pressure sensor at a preset position in the hydraulic pipeline, pipeline pressure at the preset position can be obtained, and the pressure distribution condition in the operation process of the hydraulic pipeline can be detected. The pressure detection mode is simpler and more convenient and is easy to realize.

The hydraulic pipeline can be provided with 4 paths of optical fibers. The side wall of each metal sheet is provided with two optical fibers along the central axis respectively, and the two optical fibers are symmetrical relative to the metal sheet. Along the longitudinal direction of the pressure sensor, the inner and outer fiber gratings of the metal sheet on the female side form an inner and outer fiber grating group, and the inner and outer fiber gratings of the metal sheet on the male side form another pair of inner and outer fiber grating groups. The four optical fibers form two groups of light paths on two sides of each grating pressure sensor, wherein one group of light paths reflects a broadband periodic light signal; the other group of light paths transmit frequency modulation polarized light signals, and the polarized light signals are polarized light signals with specific frequencies corresponding to gratings of the grating pressure sensor to be detected; the frequency modulation polarized light signals are polarized light signals which are emitted by the light source according to certain preset sequence periods.

In fig. 1, the sensor optical signal incidence module 3 is configured to split a periodic broadband optical signal and a polarized optical signal into two paths, and make the two paths of the periodic broadband optical signal and the polarized optical signal respectively enter optical cables 61 corresponding to the fiber bragg grating pressure sensor group 5, so as to ensure that the periodic broadband optical signal enters an inner fiber bragg grating group and an outer fiber bragg grating group on the female side of the fiber bragg grating pressure sensor, and the polarized optical signal enters the inner and outer fiber bragg grating groups on the male side of the fiber bragg grating pressure sensor.

As shown in fig. 1, in the light source control module 2, a broad spectrum light source switching module 21 can control a broad spectrum light source 11. The broad spectrum light source switching module 21 is used for modulating the broad spectrum light signal into a broad spectrum light signal emitted in a period of millisecond or less. The electro-polarization controller 22 may modulate the polarization of the particular wavelength emitted by the tunable laser 12 as a particular polarized light as desired by the corresponding sensor. The polarized light after modulation enters the entrance end of the optical fiber, the polarization state is 45 degrees, the polarization angle of the incident linearly polarized light is 56 degrees 18 degrees, and the azimuth angle of the polarization state of the incident light is 45 degrees plus or minus 1 degrees. The wavelength of the polarized light signal is selected based on the stop band wavelength lambdap of the respective grating of each grating pressure sensor, and lambdap is in the region from the 1/2 position of the hypotenuse of the transmission spectrum of the grating to the 2/3 position of the stop band edge. The present embodiment is schematically illustrated with a second grating pressure sensor λp. The grating stop band wavelengths lambdap of the serial sensors can be periodically emitted by the tunable laser 12 in the light source module 1 according to a preset sequence by the computer system 9 to form polarized light sequence spectrums, wherein the polarized light sequence spectrums have the same time interval between every two adjacent spectrums, and the interval period between the spectrums of each specific wavelength is the same. The length of time that each grating stop band wavelength λp is emitted is the shortest time-consuming decision that can be demodulated by the demodulator for stokes parameters s1, s2, and s3 of the polarized light signal, and is defined as the shortest period that can be detected. These polarized light sequence spectra, having the shortest period, are generated by the computer system 9 by cyclical emission, ensuring that each period scans the grating of the respective serial sensor, thereby obtaining stokes parameters of the transmitted birefringent polarized light signal of the respective serial sensor.

For convenience of signal acquisition, the method for acquiring the optical signals of the first fiber grating pressure sensor and the second fiber grating pressure sensor is specifically described, and the method for acquiring the optical signals of other sensors is similar. For convenience of description, the light wave reflected by the first fiber grating pressure sensor will be referred to as a first light wave, and the light wave reflected by the second fiber grating pressure sensor will be referred to as a second light wave. The data acquisition module is connected with the first grating pressure sensor, and is used for obtaining a wavelength center drift amount difference delta lambda between the cathode-side fiber grating groups of the grating pressure sensor according to the comparison of the reflection spectrum and the emission spectrum of the first grating pressure sensor and the shift of the center wavelength of the first light wave obtained by the spectrum analyzer 81 by the spectrum comparison coupler 83 when the first light wave is reflected by the first grating pressure sensor each time. Similarly, the data acquisition module is also connected with the second grating pressure sensor, so that when the second grating pressure sensor reflects the second light wave each time, the spectrum comparison coupler 83 compares the reflection spectrum and the emission spectrum of the second grating pressure sensor, and the spectrum analyzer 81 obtains the shift of the center wavelength of the second light wave, so as to obtain the wavelength center shift delta lambda between the cathode-side fiber grating groups of the grating pressure sensor. The data acquisition module may also acquire stokes parameters s1, s2, s3 of the polarized light signal transmitted by the fiber grating of the grating pressure sensor Yang Ceguang by the demodulator 82.

The computer system 9 is connected with the data acquisition module 8 and each fiber grating pressure sensor, and the computer system 9 can determine the pressure sensed by the first fiber grating pressure sensor according to the data of the first fiber grating pressure sensor acquired by the data acquisition module 8 and the calibration data table obtained by the auxiliary pressure calibration workstation 7. Similarly, the computer system 9 can also determine the pressure sensed by the second fiber grating pressure sensor according to the data of the second fiber grating pressure sensor acquired by the data acquisition module 8 and the calibration data table obtained by the auxiliary pressure calibration workstation 7.

Specifically, the light source comprises a broad spectrum light source and a tunable laser; the broad spectrum light source comprises tungsten filament lamp, hernia lamp, etc. The spectrum analyzer 81 includes a spectrometer for receiving a broad spectrum light source signal and a polarization light analyzer for receiving polarized light emitted by a tunable laser. The spectrometer is a spectrum analysis instrument controlled by a photon detector (CCD) and a computer, and the photon detector is arranged in a detection area of the spectrometer in a linear array or an area array so as to collect data above millisecond level.

Before measuring the pressure, the computer system 9 needs to calibrate the calibration data table obtained by the auxiliary pressure calibration workstation 7, that is, the computer system 9 needs to perform pressure calibration on the bionic fish-shaped grating pressure sensor through the auxiliary pressure calibration workstation 7 through the optical path system. The specific calibration method is as follows:

The auxiliary pressure calibration station 7 can be pressurized and depressurized step by step to achieve the measurement of the limiting pressure of the fiber grating pressure sensor. When the limit pressure of the bionic fish-shaped grating pressure sensor is measured, an optical fiber grating pressure sensor can be checked, and three-wheel step-by-step pressurization and step-by-step depressurization tests and measurement are carried out by taking every 0.1MPa as a step from 0 MPa. When the numerical error of the pressurization and depressurization detection is lower than the error of 0.05MPa, the pressure is increased by 0.1MPa, and three-wheel gradual pressurization and gradual depressurization tests and determination are carried out. Repeating the steps until an error of 0.1MPa occurs, recording the measured maximum pressure value, and dividing the maximum pressure value by a preset value such as 1.33 to obtain the limit pressure value of the fiber grating pressure sensor. The error of 0.05MPa recited in this embodiment can be adjusted according to a specific accuracy. Specifically, the air bag 515 encapsulated by the bionic fish-shaped grating pressure sensor is not broken, and particularly the air bag volume ratio is more than 50%, and the elasticity of the air bag can be restored to be normal in principle, so long as the hysteresis error of the feedback signal of the sensor is ensured to be smaller than the required precision error, the hysteresis error is allowed. The following details a holographic calibration method for a data table provided in an embodiment of the present application.

The holographic calibration method of the pre-stored data table comprises three steps:

first, a maximum measurement range Pmax is determined: and (3) sampling a sensor, starting to pressurize according to the maximum pressure 5MPa which can be tolerated by 500 m deep-sea blue whales, gradually pressurizing a pressing force array { Pi } by taking preset detection precision as a step length, adding Pi to Pi+1, then reducing Pi from Pi+1 to Pi, then adding Pi+2, then reducing Pi+2 to Pi+1, then adding Pi+3, and repeating until the pressure is reduced from high pressure to low pressure. The initial pressure value and the preset detection precision can be determined according to specific conditions.

When no signal is reproduced or is still present, the pressure is the detectable limit pressure Pext of the batch of sensors and defines the maximum range pmax=pext/1.33 of the batch of sensors. Wherein, the signal is not reproduced, namely, the Stokes parameters of the gratings 3 and 4 collected from the positive side of the sensor are unchanged, or the wavelength center drift difference value of the gratings 1 and 2 collected from the negative side is unchanged or reversely changed.

Second, coding: and for the sensor for detection, taking the detection precision as a step length, and pressurizing step by step from zero until the maximum pressure Pmax to form a calibration pressure array { Pi is less than or equal to Pmax }. Correspondingly, the difference in the wavelength center shift amount acquired from the sensor's female side also forms a corresponding array { δλi }, the stokes parameters of the gratings 3,4 acquired from the sensor's male side form two 3-element arrays { s1i3, s2i3, s3i3} and { s1i4, s2i4, s3i4} (the data not acquired above is filled with 0), respectively, such that each pressure Pi corresponds to 7 parameters (δλi, s1i3, s2i3, s3i3, s1i4, s2i4, s3i 4), which 7 parameters form a set of codes, i.e., a combination code of full information.

Optimally, the detection accuracy can be divided into two stages: the vacuum degree measurement level is between 0MPa and 0.1MPa, the detection precision is not more than 0.01MPa, or the pressure rise level difference is not more than 0.01MPa when the pressure is increased step by step, and the pressure rise level difference is 0. The working pressure level is between 1MPa and the maximum pressure Pmax, and the detection precision is determined according to the working environment.

Third, tabulating: and (3) corresponding each group of codes to the corresponding pressure, and compiling a holographic calibration data table.

Specifically, the calibration data table is prepared by 3 stages:

the first stage, according to the wavelength center drift difference delta lambda i, stokes parameters s1i3, s2i3, s3i3; s1i4, s2i4, s3i4, and the parameter Xi is determined. A table is prepared with the calibration pressure Pi at the second boost and the parameter Xi as the center Ci of the hidden layer basis function in the RBF-like algorithm. The columns of the table are arranged in ascending order from Pi to Xi, the row labels are arranged in order of Xi, each column forms a coding string Xi taking Pi as a header, and the coding string Xi is similar to a cylindrical central shaft taking Pi as the top surface center;

and in the second stage, determining the circular radius of each section of the reducing cylinder marked by Pi. According to the data obtained during twice boosting or depressurization, a similar table is formulated according to the method, the table is arranged in a layered mode, the depth of each table position coordinate (Pi, xi) is the first boosting and depressurization, four groups of data of the second boosting and depressurization are layered to form a drawer-shaped three-dimensional table group, wherein the data of the second boosting is the center Ci, and the other three groups of data are compared with the center data Ci to obtain a distance hi= Xi-Ci; the maximum himax is the circular radius of a section cylinder taking Pi as the top surface center, taking the coding string Xi as the cylinder center axis and taking a certain Xi as the center; a different diameter cylindrical data set is formed with Pi as the top center, the code string Xi as the cylindrical center, and himax as the cross-sectional radius.

Third stage, simplifying the table:

(1) based on the table of the first stage, the { Pi, xi } table is reformulated in the form of the table as an empty table of the calibration data table.

(2) And (3) comparing each column of data with each other after the data radius is expanded according to Pi, intercepting Xi as the cross-section circle data of the wavelength center drift amount difference delta lambda, selecting the Pi column corresponding to the non-cross item, cutting the whole column, moving the column into the corresponding column of the calibration data table, and removing other elements to form a one-to-one corresponding algorithm relation.

For the Stokes parameters s1 of the fiber bragg grating at the outermost side of the anode with cross terms, comparing the data of each column with each other according to the rest Pi to obtain the cross overlap terms, selecting the Pi column without the cross terms, shearing the whole column, and then moving the column to the corresponding column of the calibration data table, and removing other elements to form a one-to-one corresponding algorithm relation.

The other parameters are analogized in turn, and a one-to-one corresponding algorithm relation is established in the calibration table; secondly, extracting Pi to Xi from the rest tables according to one-to-two and one-to-three as a multi-correspondence algorithm relation, respectively cutting and moving the Pi to Xi into the calibration tables, and simultaneously removing other parameters except the corresponding multi-correspondence algorithm relation.

(3) In the encoding of a pair 7, if the overlapped items still exist, a dice rolling algorithm is executed on the corresponding Pi, wherein the dice rolling algorithm is that a random algorithm is added, when 7 item weight codes exist, the pressure values are similar, and a computer can randomly select the corresponding pressure value from the corresponding Pi to display.

When the computer system measures the pressure value, the pressure corresponding to 7 parameters in the data table can be determined as the pressure value detected by the corresponding grating pressure sensor by comparing the 7 parameters acquired by the grating pressure sensor with the holographic calibration data table and using a neural network table look-up algorithm.

Specifically, the neural network table look-up algorithm adopted by the computer system 9 can scan and compare collected data from top to bottom and from left to right from the simplified calibration data table, so long as the collected data falls into a comparison interval Xi, and Pi is displayed if one of other Xi is not; if the 7 parameters of the comparison interval Xi are repeated entirely, pi is randomly selected and displayed.

Specifically, the computer system 9 is connected with the data acquisition module 8 and each fiber grating pressure sensor, and is used for the pressure response detection process of the hydraulic pipeline as follows:

First, the light source control module 2 controls the light source module 1 to emit a first light wave and a second light wave through light pulses. The first grating pressure sensor reflects only the first light wave and the second grating pressure sensor reflects only the second light wave.

Next, the light source control module 2 starts to control the light source module 1 to emit a periodic broadband light signal, and counts the number of periods of the emitted light signal. When the light source control module 2 controls the first light wave and the second light wave to emit at intervals, the first grating pressure sensor only reflects the first light wave, and the second grating pressure sensor only reflects the second light wave. Thus, if the even number of counts of the light pulses by the computer system 9 indicates a first light wave, it indicates a reflection of the first light wave by the first fiber grating pressure sensor. The odd number of counts of the light pulses by the computer system 9 then represents the second light wave, representing the reflection of the second light wave by the second fiber grating pressure sensor. And the emission synchronization error between the first light wave and the second light wave is only one preset emission period.

After that, since the initial pressure in the hydraulic pipeline is relatively stable, the center frequency of the light wave reflected by the fiber grating pressure sensor is also relatively stable. When a pulse pressure is applied to the hydraulic pipeline, the negative side optical grating group of the first fiber grating pressure sensor is influenced by the pressure when reflecting the first light wave, and the wavelength center drift difference value of the first light wave reflected by the negative side optical grating group can be shifted. Then, the computer system 9 records the corresponding number of light pulses from the beginning of counting a certain light pulse period selected by the computer system 9 to the end of changing the pressure at the inlet of the hydraulic pipeline according to the change of the wavelength center drift amount difference value between the cathode-side light gratings of the first fiber grating pressure sensor collected by the data collection module, and records n1 as the duration of detecting the pulse pressure at the inlet of the hydraulic pipeline.

When the second light wave is reflected by the second grating pressure sensor, the wavelength center drift difference value of the second light wave reflected by the second grating pressure sensor is also offset. Then, according to the change of the wavelength center drift difference value between the cathode-side optical grating groups of the second grating pressure sensor acquired by the data acquisition module, the computer system 9 starts counting a certain light pulse period, ends counting the pulse pressure at the outlet of the hydraulic pipeline, records the corresponding light pulse number, and records n2 as the duration of conducting the pulse pressure to the outlet of the hydraulic pipeline.

Specifically, the computer system 9 determines the pressure response time of the hydraulic line according to t=t×n2-n1, wherein the hydraulic line includes all lines and joints between hydraulic elements, the lines include straight pipes and bent pipes, and the bent pipes include spiral pipes or hoses with bent joints; t represents the pressure response time, wherein the pressure response time comprises the time length from the start of sending a command to the end of detecting the preset pressure at the preset position of the hydraulic pipeline by an electronic element corresponding to the first grating pressure sensor in the hydraulic system, or the time length from the impulse impact sent by the hydraulic element at one end of the hydraulic pipeline to the other end of the hydraulic pipeline. The pulsation impact sent by the hydraulic element indicates that the hydraulic element at the pipeline end is opened or the instantaneous extrusion of the hydraulic element to the liquid in the pipeline caused by load impact exceeds the preset pressure maximum value; n1 represents periodic optical signal counting from the start of an instruction sending of an electronic element on a hydraulic element corresponding to a first grating pressure sensor in the digital hydraulic system to the time when the first grating pressure sensor detects pulse pressure, or periodic optical signal counting when the first grating pressure sensor detects pulse impact sent by a hydraulic element at a pipeline end; n2 represents the periodic optical signal count from the start of the instruction sending of the electronic element on the same hydraulic element corresponding to the first grating pressure sensor corresponding to n1 to the time when the second grating pressure sensor detects the pulse pressure, or the periodic optical signal count of the pulse impact sent by the hydraulic element at the pipeline end nearest to the n1 count is detected by the second grating pressure sensor; t represents the emission period of the periodic optical signal.

It will be appreciated that from the time the computer system 9 transmits the nth 1 st pulse of light, the pressure at the inlet of the hydraulic line reaches the pulse preset pressure. After that, after a plurality of periods of light pulses are emitted, the pressure at the outlet of the hydraulic pipeline reaches the preset pressure of the pulses, and at this time, the computer system 9 emits light pulses for the nth 2 th reflection. Thus, the number of emitted light pulses through which the pulse pressure is detected from the hydraulic line inlet to the hydraulic line outlet may be n2-n1, or may be defined as the number of light pulses emitted for the shortest time in the course of the maximum pressure value detected at the hydraulic line inlet to the maximum pressure value at the hydraulic line outlet being n2-n1. Thus, the time of the pressure response can be determined by T x (n 2-n 1). The unit of the transmission period T of the periodic broadband optical signal is microsecond or ps. The pulse pressure may be set by taking the maximum value detected in the pressure range detected by the cathode-side grating group or higher than the detection range as a preset pulse pressure value.

In the prior art, even though a high-frequency response pressure sensor is arranged at the inlet and the outlet of a hydraulic pipeline, the time of pressure response between the inlet and the outlet is difficult to calculate. In the embodiment of the application, by combining the periodic light wave with the fiber grating pressure sensor, the system can determine the pressure response time by calculating the number of emitted light pulses experienced by the pressure transmission. The time calculated by the difference subtraction method is irrelevant to the speed of data transmission, so that the influence of data transmission can be eliminated, and the limitation of system lag time delay is avoided, so that the system error can be eliminated, and the reliability and the accuracy of the detection result are enhanced. And, since the preset emission period of the light pulse emission is short, even in the microsecond or ps order, even if the interval emission between the first light wave and the second light wave causes the hysteresis of the detection system, it is controllable and negligible. The fiber grating pressure sensor can timely sense the pressure change in the hydraulic pipeline in a very short time through microsecond-level emitted light waves, so that the measurement of pressure response is realized, the measurement of millisecond-level precision is also realized, and the further deepening of the hydraulic pipeline research is enhanced.

For the periodic polarized light signal of the positive side, the pressure response period can be measured by the method, but the measurement accuracy is influenced by the polarized light emission period and the shortest time for demodulating Stokes parameters s1, s2 and s3 of the polarized light signal by the demodulator, and the measurement accuracy is difficult to reach the millisecond level, so the invention is not repeated.

The specific pressure response principle is mainly expressed as follows:

1. the grating pressure sensor is of a Taiji fish structure. The concave side metal sheet is provided with grooves 513 up and down at the grating to form a movable diaphragm which is easy to respond, and the difference of the wavelength change of the reflection or transmission waves of the gratings in the grating groups inside and outside the diaphragm is used as a pressure measurement signal. The grooves 513 serve to eliminate the influence of temperature variation and improve pressure detection sensitivity. For the grating groups on the left side and the right side, a group of the metal sheets on the female side receives the periodic broadband optical signals, a group of the metal sheets on the male side receives the polarized optical signals, and two gratings are realized through two groups of different optical signals. The fish belly in the pair of the cathode and anode metal plates of the Taiji fish is encapsulated with a light inert gas air bag 515 and a nonmetallic material with low elastic modulus, which can form the ladder-shaped elastic modulus of the encapsulation matrix under different pressures, thereby increasing the high sensitivity of the sensor under low pressure and achieving the purpose of expanding the detection range of the grating. The period of the negative side light signal is millisecond or less, and the period of the positive side light signal is the shortest period which can be detected by Stokes parameters of the positive side light signal birefringent polarized light. The shortest period that can be detected is determined by the shortest time that the demodulator can demodulate stokes parameters s1, s2 and s3 of the polarized light signal.

2. When two metal sheets of the grating pressure sensor are subjected to liquid pressure which changes from small to large, the deformation characteristic of the shape of the grating pressure sensor is in a ladder shape, and the detection of the pressure is completed by the grating assembly force on two sides of the two metal sheets. The corresponding cavity parts of the metal sheet have different deformation amounts in the longitudinal direction and the transverse direction under different pressures.

Specifically, in the process of increasing the liquid pressure from small to large, the grating group relay on two sides of the two metal sheets is completed, and the steps are as follows:

in the first stage, the deformation of the two metal sheets is firstly increased to the two longitudinal sides, so that the period of the grating grids stuck on the metal sheets is increased, and the deformation of the metal sheets on the female side is larger than that of the metal sheets on the male side. In this stage, the influence of temperature on the gratings is eliminated by utilizing the principle of positive and negative deformation of the metal sheet through two fiber gratings on two sides of the metal sheet on the female side, so that the pressure detection of temperature self-compensation is realized.

In the second stage, as the liquid pressure continues to increase, the supporting portions 516 of the two metal sheets are mutually folded and abutted, the whole elastic modulus is stepwise raised, the deformation amounts of the two longitudinal ends of the metal sheets are slowed down, and the detection sensitivity of the two groups of fiber gratings on the two sides of the two metal sheets to longitudinally deform is reduced. The fiber grating arranged on the outer side of the metal sheet with strong deformation resistance is firstly subjected to elliptical deformation under the action of liquid pressure and supporting force of the metal sheet, so that resonance splitting of polarized light is caused.

In the third stage, as the liquid pressure continues to rise, the liquid pressure acts on the fiber gratings inside the metal sheet on the positive side through the metal sheet on the negative side, the air bag 515 and the elastic filler, so that the cross section of the fiber gratings inside the metal sheet on the positive side is deformed in an elliptical manner, and resonance splitting of polarized light is caused. The external pressure can be detected by collecting the central wavelength fluctuation of the x-polarized light and y-polarized light amplitude spectrum of the characteristic light signal in the grating or by collecting stokes parameters s1, s2 and s3 of the characteristic light signal in the grating.

Additionally, due to the inert gas in the package, the sensor generally floats in the middle of the pipeline, so that the accuracy of pressure measurement in the pipeline is further improved.

Still further, the computer system may determine whether a hydraulic line other than the solenoid is faulty based on pressure data detected by each fiber grating pressure sensor. For example, if the pressure value detected by the fiber grating pressure sensor is too low, the corresponding position of the hydraulic pipeline may have leakage or negative pressure conditions such as vortex; if the pressure distribution in the hydraulic pipeline detected by the fiber grating pressure sensor is uneven, throttling conditions with excessively high flow speed may exist at the corresponding position of the hydraulic pipeline; if the pressure distribution in the hydraulic pipeline detected by the fiber grating pressure sensor is abnormal, or the pressure response time is prolonged, pipeline blockage can exist, or the reversing valve is not reversed or the reversing valve is blocked; etc.

Optimally, the broadband light source can also be a light emitting diode, i.e. an LED lamp. Because the length of the hydraulic pipeline is generally shorter, the transmission distance of the built-in optical fiber is also shorter, and the attenuation of the light wave is less, so that the visible light such as an LED lamp can be used as a light source, the cost is lower, and the realization and popularization are easy.

It should be noted that, in the embodiments of the present application, the two periodic optical signals reflected by the negative side optical grating group may be periodic broadband optical signals, or polarized optical signals of the sequential characteristic spectrum group may be emitted periodically. The serial characteristic spectrum group is polarized light signals with different corresponding grating characteristic frequencies among the serial grating pressure sensors, the serial characteristic spectrum group is formed by transmitting the polarized light series spectrums according to a preset sequencing sequence of the computer system at the same time interval period, and the polarized light series is circularly transmitted by the computer system.

In the embodiments of the present application, no part is referred to as the prior art or may be implemented using the prior art.

The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and changes may be made to the present application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. which are within the spirit and principles of the present application are intended to be included within the scope of the claims of the present application.

Claims

1. A system for detecting pressure response and pressure distribution in a spiral line, comprising:

the computer system is used for controlling the polarized light source in the light source module to periodically emit polarized light signals with different characteristic frequencies, or controlling the broadband light source to emit periodic broadband light signals through the light source control module, determining the pressure response time of the hydraulic pipeline according to the counting and the emitting period of the periodic light signals, and determining the pressure of a preset position in the hydraulic pipeline according to the central wavelength fluctuation of the broadband light signals reflected by one side of the fiber bragg grating groups in each grating pressure sensor or according to the Stokes parameters of the polarized light signals transmitted by the other side of the collected fiber bragg grating groups;

The grating characteristic values among the grating pressure sensors in the first grating pressure sensor, the second grating pressure sensor and the third grating pressure sensor group are different, and the first grating pressure sensor, the second grating pressure sensor and the third grating pressure sensor group are arranged in a hydraulic pipeline in series;

each grating pressure sensor is a bionic fish-shaped grating pressure sensor, each bionic fish-shaped grating pressure sensor comprises two fish-bone-shaped metal sheets which are arranged in a mutually sub-symmetrical mode, the fish-bone-shaped metal sheets which are arranged in the sub-symmetrical mode refer to metal sheets near the fish-line on the left side and the right side of the bionic fish-shaped sensor, the thicknesses or structures of the metal sheets are not identical, so that structural rigidity differences are caused, the side of the metal sheet with high structural rigidity is called the positive side, the corresponding side of the metal sheet is called the negative side, two optical fibers are respectively arranged on the side wall of each metal sheet along the central axis, the two optical fibers are symmetrically arranged relative to the metal sheet, a grating is recorded on each optical fiber in the middle of the metal sheet, and the characteristic values of the gratings in each grating pressure sensor are identical.

2. The system of claim 1, comprising four optical fibers forming two sets of optical paths on both sides of each grating pressure sensor, wherein one set of optical paths reflects a broadband periodic optical signal; the other group of light paths transmit frequency modulation polarized light signals, wherein the polarized light signals are polarized light signals with specific frequencies corresponding to gratings of the grating pressure sensor to be detected; the frequency modulation polarized light signals are polarized light signals which are emitted by the light source periodically according to a certain preset sequence.

3. The system according to claim 2, wherein the computer system is specifically configured to determine, from a pre-stored data table, an ambient pressure value outside the grating pressure sensor corresponding to a difference Δλ (T) between two wavelength offsets of the optical signal reflected by the grating pressure sensor cathode-side optical grating group within the same period; and determining the ambient pressure value outside the grating pressure sensor corresponding to the two ternary arrays from a pre-stored data table by the two ternary arrays corresponding to Stokes parameters of polarized light transmitted by the two gratings in the grating group of the grating pressure sensor Yang Ceguang;

and controlling the light source or the light source control module to periodically emit broadband light signals to the cathode-side optical grating group of the grating pressure sensor or periodically emit polarized light signals with different specific frequencies in a preset sequence to the grating pressure sensor Yang Ceguang optical grating group;

the period of the negative side light signal is millisecond or less, and the period of the positive side light signal is the shortest period detected by Stokes parameters of the positive side light signal birefringent polarized light; the shortest period detected is determined by the shortest time taken for the demodulator to demodulate stokes parameters s1, s2 and s3 of the polarized light signal.

4. The system of claim 1, wherein the system further comprises a controller configured to control the controller,

the computer system determining a pressure response time of the helical piping based on t=t (n 2-n 1);

wherein t represents pressure response time, and the pressure response time comprises the time length when the pulsation impact sent by the hydraulic element at one end of the spiral pipeline reaches the other end of the spiral pipeline;

the pulsation impact sent by the hydraulic element indicates that the hydraulic element at the pipeline end is opened or the pressure peak value of the instantaneous extrusion of the hydraulic element to the liquid in the pipeline caused by load impact exceeds the preset pressure maximum value; n1 represents periodic optical signal counting when a first grating pressure sensor at one end of the spiral pipeline detects pulse pressure or periodic optical signal counting when the first grating pressure sensor detects pulse impact sent by a hydraulic element at the pipeline end; n2 represents a periodic optical signal count when the second grating pressure sensor corresponding to n1 detects the pulse pressure, or the second fiber grating pressure sensor detects a periodic optical signal count of pulse impact sent by a hydraulic element at the pipeline end nearest to the n1 count, and T represents a transmitting period of the periodic optical signal, wherein the transmitting period is in a millisecond level or a time level below the millisecond level; the periodic optical signal count is the count of the optical signal period by a computer, and n2 and n1 count base points are uniformly determined by the computer.

5. The system of claim 1, further comprising an auxiliary pressure calibration workstation; the auxiliary pressure calibration workstation is connected with the computer system;

the auxiliary pressure calibration workstation comprises a hydraulic pipeline for calibration, a hydraulic workstation and an external pressure detection system;

the hydraulic pipeline for calibration is provided with an optical fiber sealing structure; the hydraulic working station controls the opening and closing of an oil way in the hydraulic pipeline for calibration or the gradual pressurization and gradual depressurization according to a control instruction from the computer system;

and the external pressure detection system is used for detecting the pressure in the hydraulic pipeline for calibration, establishing a corresponding relation between the pressure and the detection signals of the calibrated fiber grating pressure sensor and the system, and obtaining the calibration of the fiber grating pressure sensor and the system.

6. The system of claim 3, wherein the two periodic optical signals reflected by the negative side optical grating group are periodic broadband optical signals or polarized optical signals of a sequential characteristic spectrum group are emitted in a periodic manner; the serial characteristic spectrum group is a polarized light signal with different corresponding grating characteristic frequencies among the serial grating pressure sensors, and the serial characteristic spectrum group is used for emitting the formed polarized light series spectrum at the same time interval period according to a preset ordering sequence of a computer system; the polarized spectrum series is circularly emitted by the computer system through controlling the light source module.