Helical three-dimensional positioning method for distributed optical fiber temperature measurement in buried water pipelines

Abstract

The present invention discloses a helical three-dimensional positioning method for distributed optical fiber temperature measurement in buried tap water pipelines. The method firstly winds a sensing optical fiber in the form of a cylindrical helix around the outer wall of the pipeline; then, a distributed optical fiber Raman temperature measurement system is used to monitor the pipeline temperature in real time; when a leak in the pipeline causes a temperature anomaly, the system uses the principle of optical time domain reflection to accurately locate the abnormal point along the one-dimensional arc length of the optical fiber. L； Finally, the present invention creatively combines the geometric parameters of the cylindrical helix with the measured optical fiber arc length L , using parametric equations to calculate the coordinates of the leak point in three-dimensional space. This method successfully maps the one-dimensional temperature measurement signal into three-dimensional spatial coordinates, accurately determining both the axial position of the leak point along the pipeline and its radial orientation across the pipeline cross-section. This overcomes the existing inability to accurately locate leak points in buried pipelines in three dimensions, significantly improving inspection efficiency and reducing maintenance costs.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline safety monitoring, and in particular to a method for high-precision three-dimensional spatial positioning of a leakage point in a buried tap water pipeline by utilizing distributed optical fiber sensing technology. Background Art

[0002] Buried water pipelines are critical infrastructure for urban water supply systems, and their safe and stable operation is crucial. However, due to factors such as pipeline aging, external damage, and geological subsidence, pipeline leaks occur frequently. These not only waste water resources but can also trigger secondary disasters such as ground collapse. Therefore, timely and accurate detection and location of pipeline leaks are of great importance.

[0003] The Distributed Temperature Sensing System (DTS) is an advanced monitoring technology that uses optical fiber as a sensor and leverages the Raman scattering effect to achieve continuous, distributed temperature measurement at every point along the fiber path. DTS technology offers advantages such as long measurement distance, immunity to electromagnetic interference, intrinsic safety, and ease of deployment. It has been applied to temperature monitoring in large-scale projects such as oil and gas pipelines, high-voltage cables, and dams.

[0004] In buried water pipeline leak detection applications, when a leak occurs, the leaking water exchanges heat with the surrounding soil, causing abnormal temperature changes near the leak point. By laying sensing fiber along the pipeline, the DTS system can capture this temperature anomaly and, using the principles of optical time domain reflectometry (OTDR), determine the one-dimensional position of the anomaly point from the fiber measurement starting point, i.e., the length along the fiber path.

[0005] However, existing technologies only provide one-dimensional arc length information along the optical fiber at the leak point. For a three-dimensional pipeline system, this one-dimensional information cannot directly reveal the leak's specific location on the pipeline. In other words, it's impossible to distinguish whether the leak is at the top, bottom, or side of the pipeline (radial positioning), nor is it possible to accurately correlate it with the actual axial length of the pipeline (axial positioning). In actual repair work, inaccurate positioning often requires extensive excavation, which not only increases repair costs and time, but also creates unnecessary impacts on traffic and the environment.

[0006] Therefore, how to accurately convert the one-dimensional optical fiber position information provided by the DTS system into the three-dimensional spatial coordinates of the leakage point and achieve precise positioning of the leakage point of the buried pipeline is a technical problem that needs to be solved urgently. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of existing technologies by providing a helical three-dimensional positioning method for distributed optical fiber temperature measurement in buried water pipelines. This method accurately converts the one-dimensional arc length information detected by the DTS system into the three-dimensional spatial coordinates of the leak point, thereby achieving simultaneous and precise radial and axial positioning of the leak point.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A spiral three-dimensional positioning method for distributed optical fiber temperature measurement of buried tap water pipelines includes the following steps:

[0010] Laying steps: Select a distributed sensing optical fiber and lay it with a preset and constant radius R and constant pitch p , it is laid along the outer wall of the target buried water pipe in a cylindrical spiral shape in a tightly fitting manner. Among them, the laying radius R Approximately equal to the outer radius of the pipe, or slightly larger than the outer radius of the pipe to take into account the thickness of the optical fiber itself. Accurately record the starting point of the laying, the spiral direction (such as right-handed), and the determined radius R and pitch p parameter.

[0011] Monitoring steps: Connect the laid sensing fiber to a distributed fiber Raman temperature measurement system (DTS). This system primarily consists of a laser module, a wavelength division multiplexing module, an optoelectronic receiver and amplifier module, a data acquisition module, and a host computer. Once operational, the system continuously emits laser pulses into the sensing fiber, receives backscattered Raman light, and demodulates temperature distribution data along the entire fiber path in real time.

[0012] One-dimensional positioning steps: When a leak occurs somewhere in the pipeline, the leaking water will cause an abnormal temperature change near that point. The DTS system captures this abnormal point by analyzing the temperature distribution data. The system immediately triggers the positioning program. Based on the principle of optical time domain reflectometry (OTDR), it accurately measures the round-trip time difference between the laser pulse and the backscattered Raman scattered light signal received from the abnormal point. , combined with the speed of light in vacuum c and the effective refractive index of the fiber Calculate the exact arc length of the temperature anomaly point from the starting point of the sensor fiber optic laying L The calculation formula is:

[0013]

[0014] Step S4, 3D coordinate calculation: To describe the exact location of the leak point on the pipeline, a local 3D rectangular coordinate system is established. The coordinate system takes the central axis of the pipeline as the Z axis and the cross section of the pipeline where the laying starting point is located as the XY plane. Using the geometric parameters recorded in the laying step (radius R , pitch p ) and the arc length calculated in the one-dimensional positioning step L , perform three-dimensional coordinate mapping calculation.

[0015] First, according to the relationship between the arc length of the cylindrical helix and the rotation angle, the arc length is calculated L The corresponding total angle of spiral rotation θ , the calculation formula is:

[0016]

[0017] Then, the calculated rotation angle θ and the known radius R , pitch p Substituting the standard cylindrical helix parameter equation, the three-dimensional coordinates of the leakage point in the established local coordinate system can be obtained ( x,y,z ):

[0018]

[0019] Through the above steps, the present invention can calculate the one-dimensional leakage point optical fiber position. L Accurately converted into three-dimensional space coordinates ( x,y,z ).

[0020] In order to facilitate linkage with the Geographic Information System (GIS) and guide on-site construction, the present invention also includes a coordinate conversion step: the calculated local three-dimensional coordinates ( x,y,z ) to global geographic coordinates.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention successfully solves the limitation of DTS system that it can only locate in one dimension through the innovative cylindrical spiral laying method and coordinate conversion algorithm. The calculated three-dimensional coordinates ( x,y,z )middle, z The coordinates give the exact axial position of the leak along the length of the pipeline, and ( x,y ) coordinates clearly indicate the radial position of the leakage point on the pipe cross section, achieving true three-dimensional precise positioning.

[0023] 2. The technical solution designed in the present invention greatly improves the positioning accuracy. Repair personnel do not need to conduct large-scale speculative excavation, but can directly perform fixed-point excavation based on three-dimensional coordinates, thereby greatly shortening the repair time and reducing the impact on traffic and the environment.

[0024] 3. The present invention has the ability to quickly and accurately locate and repair, effectively reduces the waste of water resources, and reduces the high engineering costs caused by blind excavation, with significant economic benefits.

[0025] 4. The principle adopted by the present invention is clear, the calculation process is clear, and it is easy to automate through software programming. This method is not only applicable to tap water pipelines, but can also be promoted and applied to other buried pipeline systems such as oil, natural gas, and heat that require precise leak positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 Schematic diagram of the process of the spiral three-dimensional positioning method for distributed optical fiber temperature measurement of buried tap water pipelines of the present invention;

[0028] Figure 2 Schematic diagram of the connection between the distributed optical fiber temperature measurement system and the measured pipeline in the helical line three-dimensional positioning method for distributed optical fiber temperature measurement of buried tap water pipelines of the present invention;

[0029] Figure 3 for Figure 2 The internal structure diagram of the distributed optical fiber temperature measurement system;

[0030] Figure 4 Schematic diagram of laying a cylindrical spiral line of a sensing optical fiber on a buried water pipeline in the method for spiral line three-dimensional positioning of distributed optical fiber temperature measurement in the present invention;

[0031] Figure 5 This is a simulation effect diagram of the three-dimensional positioning and projection of the cylindrical spiral optical fiber path and example points in the spiral three-dimensional positioning method for distributed optical fiber temperature measurement of buried tap water pipelines of the present invention.

[0032] In the figure: 1-PC host computer; 2-DTS temperature measurement host; 21-laser module; 22-wavelength division multiplexing module; 23-photoelectric receiving and amplifying module; 24-data acquisition card; 3-three-dimensional positioning sensor fiber laying; 31-buried tap water pipeline to be measured; 32-sensing fiber. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] Example 1

[0035] See also Figure 1 As shown in the flowchart, this embodiment provides a method for three-dimensional positioning of a cylindrical spiral line for optical fiber temperature measurement on the outer wall of a buried tap water pipeline. The method includes the following core steps:

[0036] Monitoring and one-dimensional positioning: A temperature sensing optical fiber 32 is wound around the buried water pipe 31 in an equidistant spiral and connected to the DTS temperature measurement host 2. The DTS system 2 uses the optical time domain reflectometry (OTDR) principle to monitor the temperature along the optical fiber in real time. When a temperature anomaly caused by a leak is detected, the system locates the one-dimensional optical fiber arc length corresponding to the anomaly point. L .

[0037] Parameter calculation: arc length of optical time domain positioning L This is the arc length of the cylindrical helix.

[0038] Using this arc length L and preset helix geometry parameters (radius R , pitch p ), calculate the rotation angle corresponding to the expansion of the spiral θ .

[0039] Determine the three-dimensional coordinates: the known radius R , pitch p and the calculated rotation angle θ Substitute it into the parametric equation of the cylindrical helix to finally determine the three-dimensional coordinates of the leakage point in the local coordinate system based on the pipeline axis. x,y,z , completing the positioning conversion from one dimension to three dimensions.

[0040] Example 2

[0041] This embodiment combines Figure 2 、 Figure 3 、 Figure 4 and Figure 5 , the scheme of Example 1 is described in more detail.

[0042] First, site preparation and laying work are carried out.

[0043] See also Figure 4As shown, a section of buried water pipe 31 to be monitored is selected; according to the outer diameter of the pipe D , determine the laying radius of the sensing optical fiber 32 R ,generally R ≈ D / 2; then determine a suitable pitch based on the desired axial monitoring resolution and on-site construction conditions (such as the minimum bending radius allowed for the optical fiber). p。

[0044] During the laying process, the starting point position and spiral direction must be accurately recorded. In this case, it is right-handed, and the optical fiber 32 must be tightly fitted to the outer wall of the pipe 31. The starting point of the laying is defined as the origin of the local coordinate system (0,0,0), and the central axis of the pipe is defined as the positive direction of the Z axis.

[0045] Next, the laid sensing optical fiber 32 is connected to the DTS temperature measurement host 2, which is controlled and displays data through the PC host 1.

[0046] See also Figure 3 As shown, the laser module 21 in the host 2 generates laser pulses, which enter the sensing optical fiber 32 through the wavelength division multiplexing module 22.

[0047] The backscattered Raman light generated in the optical fiber is reflected back by the wavelength division multiplexing module 22 , converted into an electrical signal by the photoelectric receiving and amplifying module 23 , and finally collected and processed by the data acquisition card 24 .

[0048] The system is running continuously to monitor the temperature distribution.

[0049] Assume that at a certain moment, a pipeline leak occurs, the DTS system detects temperature anomalies and triggers the positioning program; the system uses the OTDR principle to measure the signal round trip time , calculate the fiber arc length from the abnormal point to the starting point .

[0050] Get the arc length After that, it enters the three-dimensional coordinate solution stage.

[0051] Assume that the parameters recorded in the project are: paving radius R =0.11 m, pitch p =0.4m. The optical fiber arc length corresponding to a leakage point is now measured =2.0 meters.

[0052] (1) Calculate the spiral rotation angle :

[0053] According to the formula:

[0054]

[0055] This angle is approximately equal to Circles indicate that the leak point is located around the 2.5th circle from the starting point.

[0056] (2) Calculate the three-dimensional coordinates ( , , ):

[0057] Will Substituting into the parametric equation:

[0058]

[0059]

[0060]

[0061] Therefore, the local three-dimensional coordinates of the leakage point are approximately (-0.11, 0.00, 1.00).

[0062] Interpretation of the results:

[0063] See also Figure 5 As shown in the figure, the red dot is the example point.

[0064] =1.00m, which means the leak point is located 1.00m away from the starting point of the pipeline along the pipeline axis. This achieves precise axial positioning.

[0065] ( , ) = (-0.11, 0.00), indicating that on the pipe cross section 1.00 m from the starting point, the leak point is located in the negative X-axis direction, 0.11 m from the center axis (i.e., on the pipe surface). If the positive X-axis direction is defined as directly above the pipe, then the leak point is directly below the pipe. This achieves precise radial positioning.

[0066] Figure 5 The dotted lines in FIG clearly show the projection of the three-dimensional space point onto the Z axis and onto the XY plane, that is, its axial position and its radial position.

[0067] The above embodiments clearly demonstrate how the present invention maps the one-dimensional arc length data obtained by distributed optical fiber temperature measurement to three-dimensional spatial coordinates through a mathematical model, providing a complete, reliable and effective technical solution for the precise positioning of pipeline leakage points.

[0068] In a specific application scenario, the coordinate conversion step can be implemented as follows:

[0069] 1. Obtain the three-dimensional geographic coordinates of a series of key points on the central axis of the pipeline in advance through surveying and mapping methods such as GPS-RTK to form a digital pipeline path map.

[0070] 2. The axial distance z calculated according to the present invention can be used to determine the geographical coordinates of the pipeline center point corresponding to the leakage point by interpolation or search on the digital path map.

[0071] 3. According to the tangent direction and normal direction of the center point, the local coordinates ( x,y ) is rotated and translated, and finally superimposed on the geographic coordinates of the center point to obtain the precise global three-dimensional coordinates of the leakage point, where the tangent direction of the center point is the direction of the pipeline.

[0072] In this way, the positioning results can be directly used for GIS map display and on-site precise excavation, achieving higher-level applications.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A spiral three-dimensional positioning method for distributed optical fiber temperature measurement of buried water pipelines, characterized in that: The following steps are involved: Laying steps: winding a distributed sensing optical fiber (32) in a cylindrical spiral shape along the outer wall of a buried water pipe (31) with a preset radius (R) and pitch (p); the radius (R) is approximately equal to the outer radius of the pipe (31); Monitoring step: using a distributed fiber Raman temperature measurement system (DTS) (2) to monitor the temperature of the sensing optical fiber (32) in real time, wherein the distributed fiber Raman temperature measurement system (2) includes a laser module (21), a wavelength division multiplexing module (22), a photoelectric receiving and amplifying module (23) and a data acquisition module (24); One-dimensional positioning step: When the pipeline (31) leaks, the distributed optical fiber Raman temperature measurement system (2) detects the back Raman scattered light signal generated on the sensing optical fiber (32) due to temperature anomaly based on the optical time domain reflectometry (OTDR) principle, and determines the position of the back Raman scattered light signal according to the round trip time ( ), calculate the arc length of the temperature anomaly point from the starting point of the sensing optical fiber (32) ( L ); Three-dimensional coordinate calculation steps: establish a local three-dimensional rectangular coordinate system with the central axis of the pipeline (31) as the Z axis, and according to the arc length ( L ),radius( R ) and pitch ( p ), the three-dimensional coordinates of the leakage point in the local three-dimensional rectangular coordinate system are calculated through the cylindrical helix parameter equation ( x,y,z ), thereby achieving three-dimensional spatial positioning of the leakage point.

2. The spiral three-dimensional positioning method for distributed optical fiber temperature measurement of buried tap water pipelines according to claim 1 is characterized in that: In the three-dimensional coordinate calculation step, first, according to the arc length ( L ) to calculate the rotation angle of the cylindrical helix ( θ ), the calculation formula is: 。 3. The spiral three-dimensional positioning method for distributed optical fiber temperature measurement of buried tap water pipelines according to claim 2 is characterized in that: Get the rotation angle ( θ ), the three-dimensional coordinates are calculated by the following cylindrical helix parametric equation ( x,y,z ): in,( x,y ) coordinates represent the radial position of the leak point on the pipe cross section, ( z ) coordinates represent the distance of the leakage point along the axial direction of the pipeline.

4. The spiral three-dimensional positioning method for distributed optical fiber temperature measurement of buried tap water pipelines according to claim 1 is characterized in that: In the one-dimensional positioning step, the arc length of the temperature anomaly point ( L ) is calculated using the following formula: in, is the speed of light in vacuum, is the refractive index of the sensing optical fiber (32), is the round trip time of the backscattered Raman light signal.

5. The spiral three-dimensional positioning method for distributed optical fiber temperature measurement of buried tap water pipelines according to claim 1 is characterized in that: In the laying step, the sensing optical fiber (32) is wound and laid in a right-handed or left-handed manner.

6. The spiral three-dimensional positioning method for distributed optical fiber temperature measurement of buried tap water pipelines according to claim 1 is characterized in that: The method also includes a coordinate conversion step: according to the predefined spatial direction information of the pipeline center axis, the calculated leakage point coordinates in the local three-dimensional rectangular coordinate system ( x,y,z ), converted to absolute three-dimensional coordinates in the global geographic coordinate system.

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