CN113188050A - Pipeline cleaner positioning method based on linear Sagnac distributed optical fiber vibration sensing - Google Patents
Pipeline cleaner positioning method based on linear Sagnac distributed optical fiber vibration sensing Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D5/00—Protection or supervision of installations
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
- G01H9/006—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors the vibrations causing a variation in the relative position of the end of a fibre and another element
Abstract
The invention discloses a pipeline cleaner positioning method based on linear type Sagnac distributed optical fiber vibration sensing in the technical field of distributed optical fiber vibration sensing, which specifically comprises the following steps of S1: selecting a core of the long-distance pipeline accompanied with the communication optical fiber as a sensing optical fiber; s2: the selected sensing optical fiber is connected into a tube cleaner tracking and positioning system according to the technical scheme; s3: the signal analysis upper computer system controls the data acquisition card to acquire interference signal data at the 3 x 3 coupler in real time; s4: the signal analysis upper computer system carries out Fourier transformation on the acquired interference signal data in real time; s5: analyzing the obtained frequency domain spectrum data, and searching a plurality of zero frequency points in the spectrum; s6: every obtained zero frequency point can be analyzed to obtain a distance value between a vibration position and the tail end of the sensing optical fiber, and the average value of n distance values is obtained to obtain H which is used as the distance between the current vibration position and the tail end of the sensing optical fiber; the method for tracking and positioning the pipe cleaner of the long-distance pipeline has the characteristics of strong real-time performance, capability of continuously acquiring data, stability, reliability and low operation and maintenance cost.
Description
Technical Field
The invention relates to the technical field of distributed optical fiber vibration sensing, in particular to a pipeline cleaner positioning method based on linear Sagnac distributed optical fiber vibration sensing.
Background
In the process of production and service operation of long-distance natural gas pipelines, pipeline cleaning operation on the pipelines is a very important business content. Before newly-built pipeline is put into production, leave over the thing in the pipeline and suppress experimental leaving over water more, the inside water of pipeline and construction leave over thing can effectively be clear away in the dredging pipe operation. In the pipeline service operation process, sundries, accumulated liquid and accumulated dirt in the long-distance natural gas pipeline can be cleaned through pipe cleaning operation, the pipeline conveying efficiency is improved, the friction loss is reduced, the corrosion of the inner wall of the pipeline is reduced, online internal detection is realized, and the service life of the pipeline is prolonged. However, in the process of cleaning the long-distance natural gas pipeline, the blockage phenomenon of the pipe cleaner is always troubling engineering technicians, particularly the long-distance natural gas pipeline is long, the environmental conditions of the peripheral area of the pipeline are poor, the pipe cleaner cannot be accurately positioned after the blockage phenomenon occurs, the problem that the pipeline conveying is stopped occurs sometimes, and the safety of the pipeline is endangered under severe conditions, so that the accurate tracking and positioning of the pipe cleaner is a powerful measure for guaranteeing the smooth operation of the cleaning operation, and the method is very important for guaranteeing the normal stable operation of the long-distance natural gas pipeline, improving the conveying efficiency and guaranteeing the safe production.
The conventional common tube cleaner tracking and positioning method can be roughly divided into a radioactive isotope method, a mechanical method, an acoustic method, a pressure method and an electromagnetic method according to the working principle, and can be particularly divided into a plurality of positioning methods. In the tracking and positioning methods of the pipe cleaners, due to the existence of the pipe, soil and other external interference factors, various difficulties exist in the tracking and positioning of the pipe cleaners. Therefore, the traditional common tracking method has advantages and limitations, such as complex tracking method, poor anti-interference capability, incapability of continuously tracking in the whole process, requirement of a large amount of manpower and material resources, and the like.
Based on the analysis results, a tube cleaner tracking and positioning method which has the advantages of real-time performance, continuous data acquisition, stability, reliability, simple use and low operation and maintenance cost is needed to be invented. During the pipe cleaning operation, the pipe cleaner rubs the inner wall of the pipeline and collides with a welding seam at the interface of the pipeline when running in the pipeline to generate a vibration signal, the vibration signal acts on the communication optical fiber laid in the same ditch along the long-distance natural gas pipeline, the phase and other parameters of the optical fiber at the vibration position can be changed by the vibration signal according to the strain effect, the photoelastic effect and the Poisson effect, and according to the principle, the linear Sagnac distributed optical fiber vibration sensing system is built by utilizing the communication optical cable laid along with the same ditch of the long-distance pipeline, so that the real-time online accurate tracking and positioning of the pipe cleaner running in the pipeline can be realized, and the problem that the pipe cleaner cannot be accurately positioned after being blocked in the long-distance pipeline cleaning operation process is effectively solved; therefore, a pipeline cleaner positioning method based on linear Sagnac distributed optical fiber vibration sensing is provided.
Disclosure of Invention
The invention aims to provide a pipeline cleaner positioning method based on a linear Sagnac distributed optical fiber vibration sensing pipeline, and aims to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme: a pipeline cleaner positioning method based on a linear Sagnac distributed optical fiber vibration sensing pipeline comprises the following steps,
s1: selecting a core of the long-distance pipeline accompanied with the communication optical fiber as a sensing optical fiber;
s2: the selected sensing optical fiber is connected into a tube cleaner tracking and positioning system according to the technical scheme;
s3: the signal analysis upper computer system controls the data acquisition card to acquire interference signal data at the 3 x 3 coupler in real time;
s4: the signal analysis upper computer system carries out Fourier transform on the acquired interference signal data in real time to obtain frequency domain spectrum data of the signal;
s5: analyzing the obtained frequency domain spectrum data, and searching a plurality of zero frequency points in the spectrum;
s6: every time a zero frequency point is obtained, the distance H from the vibration position to the tail end of the sensing optical fiber is analyzednThus, H can be obtained1，H2，……，HnAnd totaling n distance values, and averaging the n distance values to obtain H as the distance between the current vibration position and the tail end of the sensing optical fiber.
Furthermore, the positioning method comprises a system structure, wherein the system structure comprises a light source, a 3 × 3 coupler, a delay optical fiber, a 2 × 1 coupler, a sensing optical fiber, a 1 × 2 coupler, a photoelectric detector, a data acquisition card and a signal analysis upper computer system.
Further, the light source is a broadband light source with a specific wavelength; the 3 × 3 coupler is respectively in physical optical connection with the light source, the delay optical fiber, the photoelectric detector and the 2 × 1 coupler, and the medium is an optical fiber.
Furthermore, the 2 x 1 coupler is respectively in physical optical connection with the 3 x 3 coupler, the delay optical fiber and the sensing optical fiber, and the medium is an optical fiber; the photoelectric detector is a balance detector, converts the detected optical signal change into the change of an electric signal, is physically and electrically connected with the data acquisition card and is physically and optically connected with the 3-x-3 coupler, and the medium is an optical fiber.
Further, the data acquisition card performs analog-to-digital conversion on the changed analog electric signals, acquires the analog electric signals at a high speed, and transmits the acquired data to a signal analysis upper computer system; the signal analysis upper computer system can be a local PC and can also be a cloud service computing system of a data center.
Furthermore, data transmission between the data acquisition card and the signal analysis upper computer system is wireless transmission or wired transmission, and the signal analysis upper computer system performs Fourier transformation on the acquired real-time data and converts time domain data to obtain frequency spectrum data of a frequency domain of the data.
Further, the signal analysis upper computer system analyzes the obtained frequency domain spectrum data to obtain a limited number of zero frequency points; the zero-frequency point information contains the position information of the pipe cleaner.
Further, the signal analysis upper computer system analyzes the real-time position of the pipe cleaner by using the obtained limited number of zero-frequency points; the sensing optical fiber is a core in an accompanying communication optical fiber laid in the same ditch as the oil and gas long-distance pipeline.
Compared with the prior art, the invention has the beneficial effects that: the invention utilizes the accompanying optical fiber laid in the same ditch of the long-distance oil and gas pipeline to build the linear Sagnac distributed optical fiber vibration sensing system, realizes real-time online accurate tracking and positioning of the pipe cleaner operating in the pipeline, and effectively solves the problem that the pipe cleaner cannot be accurately positioned after being blocked in the pipe cleaning operation process of the long-distance pipeline. The method for tracking and positioning the long-distance pipeline cleaner has the characteristics of strong real-time performance, capability of continuously acquiring data, stability, reliability, simplicity and convenience in use and low operation and maintenance cost.
Drawings
FIG. 1 is a schematic flow chart of a positioning method according to the present invention;
FIG. 2 is a schematic diagram of the system of the present invention;
fig. 3 is a graphical representation of pig position information in accordance with the present invention.
The drawings are for illustrative purposes only and are not to be construed as limiting the patent; for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, the present invention provides a method for positioning a pipeline pig based on linear Sagnac distributed optical fiber vibration sensing, which specifically includes the following steps,
s1: selecting a core of the long-distance pipeline accompanied with the communication optical fiber as a sensing optical fiber;
s2: the selected sensing optical fiber is connected into a tube cleaner tracking and positioning system according to the technical scheme;
s3: the signal analysis upper computer system controls the data acquisition card to acquire interference signal data at the 3 x 3 coupler in real time;
s4: the signal analysis upper computer system carries out Fourier transform on the acquired interference signal data in real time to obtain frequency domain spectrum data of the signal;
s5: analyzing the obtained frequency domain spectrum data, and searching a plurality of zero frequency points in the spectrum;
s6: every time a zero frequency point is obtained, the distance H from the vibration position to the tail end of the sensing optical fiber is analyzednThus, H can be obtained1，H2，……，HnAnd totaling n distance values, and averaging the n distance values to obtain H as the distance between the current vibration position and the tail end of the sensing optical fiber.
Referring to fig. 2 and fig. 3, the positioning method includes a system structure, and the system structure includes a light source, a 3 × 3 coupler, a delay fiber, a 2 × 1 coupler, a sensing fiber, a 1 × 2 coupler, a photodetector, a data acquisition card, and a signal analysis upper computer system.
The light source is a broadband light source with a specific wavelength; the 3 × 3 coupler is respectively connected with the light source, the delay optical fiber, the photoelectric detector and the 2 × 1 coupler physically and optically, and the medium is an optical fiber.
The 2 x 1 coupler is respectively in physical optical connection with the 3 x 3 coupler, the delay optical fiber and the sensing optical fiber, and the medium is an optical fiber; the photoelectric detector is a balance detector, converts the detected optical signal change into the change of an electric signal, is physically and electrically connected with the data acquisition card and is physically and optically connected with the 3-to-3 coupler, and the medium is an optical fiber.
The data acquisition card performs analog-to-digital conversion on the changed analog electric signal, acquires the analog electric signal at a high speed, and transmits the acquired data to a signal analysis upper computer system; the signal analysis upper computer system can be a local PC and can also be a cloud service computing system of a data center.
The data transmission between the data acquisition card and the signal analysis upper computer system is wireless transmission or wired transmission, the signal analysis upper computer system performs Fourier transformation on the acquired real-time data, and the time domain data is converted to obtain frequency spectrum data of the frequency domain.
The signal analysis upper computer system analyzes the obtained frequency domain spectrum data to obtain a limited number of zero frequency points; the zero-frequency point information contains the position information of the pipe cleaner.
The signal analysis upper computer system analyzes the real-time position of the pipe cleaner by using the obtained limited number of zero-frequency points; the sensing optical fiber is a core in an accompanying communication optical fiber laid in the same ditch as the oil and gas long-distance transmission pipeline.
The tube cleaner tracking and positioning method comprises the following steps: the light source emits continuous light, which enters from the 1 port of the 3-by-3 coupler and is output from the 4 port and the 6 port of the coupler respectively. Then, light output from the 6 ports of the 3 x 3 coupler enters the 2 x 1 coupler and needs to pass through a section of delay optical fiber, while light output from the 4 ports of the 3 x 3 coupler does not need to pass through the delay optical fiber and directly enters the 2 x 1 coupler, passes through the optical fiber arms with different lengths and then enters the 2 x 1 coupler, and light at two ends is converged into a beam of light and enters the sensing optical fiber. The end of the sensing optical fiber is provided with an optical path returning device, the returned light also passes through the 2 x 1 coupler and returns along the original optical path, interference occurs at the 3 x 3 coupler finally, and the photoelectric detector can detect the change result of the optical signal after the interference at the 3 ports of the 3 x 3 coupler. The photoelectric detector converts detected optical signal changes into changes of electric signals, the data acquisition card performs A/D conversion, changes analog electric signals into digital signals, the digital signals are acquired at high speed, the acquired signal data are transmitted to a signal analysis upper computer system, frequency domain spectrum data are obtained through real-time Fourier transform, the spectrum data are analyzed to find zero frequency points, then the real-time positions of vibration signals are analyzed by using a limited number of zero frequency points, and the real-time positions are real-time positions of the pipe cleaner.
The specific principle is as follows:
a linear Sagnac distributed optical fiber vibration sensing system is shown in fig. 1, in which there are 4 optical paths, which are as follows:
a first optical path: 6 → delay fiber → 2X 1 coupler → 1X 2 coupler → 2X 1 coupler → delay fiber → 6
And a second light path: 6 → delay fiber → 2X 1 coupler → 1X 2 coupler → 2X 1 coupler → 4
And (3) an optical path III: 4 → 2X 1 coupler → 1X 2 coupler → 2X 1 coupler → delay fiber → 6
And (4) an optical path is four: 4 → 2X 1 coupler → 1X 2 coupler → 2X 1 coupler → 4
In the above 4 optical paths, the first optical path has the longest length, the second optical path has the same length as the third optical path, and the fourth optical path has the shortest length.
In the 4 optical paths, only the second optical path and the third optical path meet the interference condition, and interference can occur at the 3 × 3 coupler;
the optical signal change detected by the photoelectric detector is the optical signal change after the interference of the second optical path and the third optical path at the 3-to-3 coupler;
in the second optical path and the third optical path, when no vibration signal acts on the sensing optical fiber, the phase difference of the transmission light is a fixed value, and the optical signal is kept unchanged as a result of interference;
in the second optical path and the third optical path, when a vibration signal acts on the sensing optical fiber, the vibration signal can cause the phase of the optical signal at the vibration position to change, and the change information of the optical signal and the change information of the optical phase thereof contain vibration position information.
The optical phase change caused by the vibration is subjected to harmonic analysis, and Fourier series expansion is carried out to obtain a plurality of combinations of sine waves with different amplitudes, different frequencies and different phases, and a sine function is used for representing any sine wave in the combinations, wherein the formula is as follows:
in the above formula, f (t) is the optical phase change caused by the vibration signal, AxAmplitude, omega, of the x-th sine wave after Fourier expansion for optical phase changexAfter Fourier series expansion for optical phase changeOf the x-th sine wave of (a),
the phase of the x-th sine wave after the optical phase change is subjected to Fourier series expansion, t is the duration of the vibration signal on the sensing optical fiber, and N is a positive integer and the quantity of the sine waves obtained after the optical phase change is subjected to Fourier series expansion.
In the technical scheme, the length of the delay optical fiber is S, the distance from the vibration signal generation position to the head end of the sensing optical fiber is L, the distance from the vibration signal generation position to the tail end of the sensing optical fiber is H, and the total length of the sensing optical fiber is L + H.
The propagation speed in the known quantity optical vacuum is c, and the refractive index of the optical fiber used in the technical scheme is n;
in the second technical scheme, the vibration position is taken as a division point, and the propagation time of light in the first half-way optical path (6 → delay optical fiber → 2 x 1 coupler → vibration position) is
In the second technical scheme, the vibration position is taken as a division point, and the propagation time of light in the second half-way optical path (vibration position → 1: 2 coupler → 2: 1 coupler → 4) is taken as
In the third technical scheme, the vibration position is taken as a division point, and the propagation time of light in the first half-way light path (4 → 2 x 1 coupler → vibration position) is taken as
In the third technical scheme, the vibration position is taken as a division point, and the propagation time of light in the second half path (vibration position → 1: 2 coupler → 2: 1 coupler → delay optical fiber → 6) is
The Fourier expansion result f (t) of the optical phase change caused by the vibration in the technical scheme, and the propagation time t of the light in the first half optical path in the second optical path1And the propagation time t of light in the second half-way and the second half-way optical paths of the optical path2The three expressions can obtain the phase change expression in the optical path II caused by the vibration signal as
The Fourier expansion result f (t) of the optical phase change caused by vibration in the technical scheme, and the propagation time t of light in the first half optical path in the third optical path3And the propagation time t of light in the second half-way light path in the third light path4The three expressions can obtain the phase change expression in the optical path III caused by the vibration signal as
From f1(t) and f2In the available technical scheme, the expression of the phase difference delta f (t) between the second optical path and the third optical path is
Δf(t)＝f1(t)-f2(t)
Using trigonometric function and difference product formula, and dividing t1、t2、t3、t4Substituting the expression into the expression of delta f (t), and finally obtaining the expression of the phase difference delta f (t) between the light path two and the light path three
The length of the delay fiber is S is a known quantity, the total length L + H of the sensing fiber is a known quantity when vibratingThe distance H between the position where the moving signal occurs and the tail end of the sensing optical fiber meets the requirement
When the light intensity is 0, the point is called a zero-frequency point, and the vibration signal frequency f is the required zero-frequency point frequency, and the condition meets the relational expression
In the above formula, k is a positive integer, pi is a circumferential rate, and f is a required zero frequency point frequency, so that the relation between the vibration signal frequency f and the distance H between the vibration position and the tail end of the sensing optical fiber is obtained
Therefore, when the frequency of the vibration signal meets the condition of a zero frequency point, a detected signal has a minimum value, the minimum value appears periodically, and the frequency value corresponding to the zero frequency point is found, so that the vibration position can be demodulated, and the positioning of the vibration signal is realized.
And (3) theoretical derivation process: the method comprises the following steps of carrying out harmonic analysis on optical phase change caused by vibration signals generated by friction, collision and the like between a pipe cleaner and the inner wall of a pipeline, a welding seam and the like, carrying out Fourier series expansion to obtain a plurality of combinations of sine waves with different amplitudes, different frequencies and different phases, and expressing any sine wave in the combinations by a sine function, wherein the formula is as follows:
in the above formula, f (t) is the optical phase change caused by vibration, AxAmplitude, omega, of the x-th sine wave after Fourier expansion for optical phase changexFor the frequency of the x-th sine wave after the optical phase change is subjected to Fourier series expansion,
the phase of the x-th sine wave after the optical phase change is subjected to Fourier series expansion, t is the duration of the vibration signal on the sensing optical fiber, and N is a positive integer and the quantity of the sine waves obtained after the optical phase change is subjected to Fourier series expansion.
In the technical scheme, the length of the delay optical fiber is S, the distance from the vibration signal generation position to the head end of the sensing optical fiber is L, the distance from the vibration signal generation position to the tail end of the sensing optical fiber is H, and the total length of the sensing optical fiber is L + H.
The propagation speed in the known quantity optical vacuum is c, and the refractive index of the optical fiber used in the technical scheme is n;
in the second technical scheme, the vibration position is taken as a division point, and the propagation time of light in the first half-way optical path (6 → delay optical fiber → 2 x 1 coupler → vibration position) is
In the second technical scheme, the vibration position is taken as a division point, and the propagation time of light in the second half-way optical path (vibration position → 1: 2 coupler → 2: 1 coupler → 4) is taken as
In the third technical scheme, the vibration position is taken as a division point, and the propagation time of light in the first half-way light path (4 → 2 x 1 coupler → vibration position) is taken as
In the third technical scheme, the vibration position is taken as a division point, and the propagation time of light in the second half path (vibration position → 1: 2 coupler → 2: 1 coupler → delay optical fiber → 6) is
The Fourier expansion result f (t) of the optical phase change caused by the vibration in the technical scheme, and the propagation time t of the light in the first half optical path in the second optical path1And the propagation time t of light in the second half-way and the second half-way optical paths of the optical path2The three expressions can obtain the phase change expression in the optical path II caused by the vibration signal as
Wherein, will
The method is developed by using a trigonometric function and a difference product formula:
and also
Therefore, the method comprises the following steps:
f is then1(t) is expressed as follows:
the Fourier expansion result f (t) of the optical phase change caused by vibration in the technical scheme, and the propagation time t of light in the first half optical path in the third optical path3And the propagation time t of light in the second half-way light path in the third light path4The three expressions can obtain the phase change expression in the optical path III caused by the vibration signal as
In the same way, will t3、t4Substitution of expression into f2(t) and developing by using a trigonometric function and a difference product formula to obtain:
from f1(t) and f2In the available technical scheme, the expression of the phase difference delta f (t) between the second optical path and the third optical path is
Δf(t)＝f1(t)-f2(t)
Wherein, will
Spread out with trigonometric functions and difference products to obtain:
the finally obtained expression of the phase difference delta f (t) between the second optical path and the third optical path is
Namely have
The length S of the delay optical fiber is a known quantity, the total length L + H of the sensing optical fiber is a known quantity, and when the vibration signal occurs the position distanceThe distance H of the tail end of the sensing optical fiber satisfies
The point is called zero frequency point, at this moment, the vibration signal frequency f is the required zero frequency point frequency, and the condition satisfies the relational expression
In the above formula, k is a positive integer, pi is a circumferential rate, and f is a required zero frequency point frequency, so that the relation between the vibration signal frequency f and the distance H between the vibration position and the tail end of the sensing optical fiber is obtained
Therefore, when the vibration signal frequency meets the zero frequency point condition, the detected optical signal has a minimum value, the minimum value appears periodically, and the frequency value corresponding to the zero frequency point is found, so that the vibration position can be demodulated, and the positioning of the vibration signal is realized.
The standard parts used in the invention can be purchased from the market, the special-shaped parts can be customized according to the description of the specification and the accompanying drawings, the specific connection mode of each part adopts conventional means such as bolts, rivets, welding and the like mature in the prior art, the machines, the parts and equipment adopt conventional models in the prior art, and the circuit connection adopts the conventional connection mode in the prior art, so that the detailed description is omitted.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (8)
1. A pipeline cleaner positioning method based on linear Sagnac distributed optical fiber vibration sensing is characterized in that: the method specifically comprises the following steps of,
s1: selecting a core of the long-distance pipeline accompanied with the communication optical fiber as a sensing optical fiber;
s2: the selected sensing optical fiber is connected into a tube cleaner tracking and positioning system according to the technical scheme;
s3: the signal analysis upper computer system controls the data acquisition card to acquire interference signal data at the 3 x 3 coupler in real time;
s4: the signal analysis upper computer system carries out Fourier transform on the acquired interference signal data in real time to obtain frequency domain spectrum data of the signal;
s5: analyzing the obtained frequency domain spectrum data, and searching a plurality of zero frequency points in the spectrum;
s6: every time a zero frequency point is obtained, the distance H from the vibration position to the tail end of the sensing optical fiber is analyzednThus, H can be obtained1，H2，……，HnAnd totaling n distance values, and averaging the n distance values to obtain H as the distance between the current vibration position and the tail end of the sensing optical fiber.
2. The positioning method for the pipeline pig based on the linear Sagnac distributed optical fiber vibration sensing is characterized in that: the positioning method comprises a system structure, wherein the system structure comprises a light source, a 3 × 3 coupler, a delay optical fiber, a 2 × 1 coupler, a sensing optical fiber, a 1 × 2 coupler, a photoelectric detector, a data acquisition card and a signal analysis upper computer system.
3. The positioning method for the pipeline cleaner based on the linear Sagnac distributed optical fiber vibration sensing pipeline as claimed in claim 2, wherein the positioning method comprises the following steps: the light source is a broadband light source with a specific wavelength; the 3 × 3 coupler is respectively in physical optical connection with the light source, the delay optical fiber, the photoelectric detector and the 2 × 1 coupler, and the medium is an optical fiber.
4. The positioning method for the pipeline pig based on the linear Sagnac distributed optical fiber vibration sensing is characterized in that: the 2 x 1 coupler is respectively in physical optical connection with the 3 x 3 coupler, the delay optical fiber and the sensing optical fiber, and the medium is an optical fiber; the photoelectric detector is a balance detector, converts the detected optical signal change into the change of an electric signal, is physically and electrically connected with the data acquisition card and is physically and optically connected with the 3-x-3 coupler, and the medium is an optical fiber.
5. The positioning method for the pipeline pig based on the linear Sagnac distributed optical fiber vibration sensing is characterized in that: the data acquisition card performs analog-to-digital conversion on the changed analog electric signals, acquires the analog electric signals at a high speed, and transmits the acquired data to a signal analysis upper computer system; the signal analysis upper computer system can be a local PC and can also be a cloud service computing system of a data center.
6. The positioning method for the pipeline pig based on the linear Sagnac distributed optical fiber vibration sensing is characterized in that: the data transmission between the data acquisition card and the signal analysis upper computer system is wireless transmission or wired transmission, and the signal analysis upper computer system performs Fourier transformation on the acquired real-time data and converts time domain data to obtain frequency spectrum data of a frequency domain of the data.
7. The positioning method for the pipeline pig based on the linear Sagnac distributed optical fiber vibration sensing is characterized in that: the signal analysis upper computer system analyzes the obtained frequency domain spectrum data to obtain a limited number of zero frequency points; the zero-frequency point information contains the position information of the pipe cleaner.
8. The positioning method for the pipeline pig based on the linear Sagnac distributed optical fiber vibration sensing is characterized in that: the signal analysis upper computer system analyzes the real-time position of the pipe cleaner by using the obtained limited number of zero-frequency points; the sensing optical fiber is a core in an accompanying communication optical fiber laid in the same ditch as the oil and gas long-distance pipeline.
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