A DAS Leakage Monitoring Method for Water Supply Pipelines Based on Hydraulic Traction and Attitude Control

Abstract

This invention discloses a DAS (Digital Optical Array) leak monitoring method for water supply pipelines based on hydraulic traction and attitude control, belonging to the field of municipal engineering pipeline safety monitoring technology. Existing fiber optic monitoring methods for pipelines suffer from low deployment success rates, random cable attitude, large positioning errors, and difficulty in identifying minute leaks. This invention uses hydraulic traction to send a sensing optical cable into the pipeline. During the traction process, the DAS device collects backscattered Rayleigh signals in real time, demodulates phase information, and calculates the strain rate. Based on the strain rate characteristics, the real-time state of the optical cable is determined to adjust the valve opening and cable delivery speed. After deployment, historical strain rate data is used to infer the attitude of each section of the optical cable within the pipeline and establish a segmented mapping relationship between the cable length coordinates and the actual spatial coordinates of the pipeline. During the monitoring phase, the solid-borne acoustic signals from the pipe wall and the acoustic signals from the water body coupled with the optical cable are extracted to construct a multi-dimensional feature vector, which is input into a classifier to output the leakage probability. The leak location is then determined based on the segmented mapping relationship.

Description

Technical Field

[0001] This invention belongs to the field of municipal engineering pipeline safety monitoring technology, and particularly relates to a DAS leakage monitoring method for water supply pipelines based on hydraulic traction and attitude control. Background Technology

[0002] As a vital component of urban lifeline engineering, the safe operation of water supply pipelines directly impacts the city's water supply security. Traditional manual inspection methods for monitoring leaks in water supply pipelines rely on inspectors listening for unusual sounds from the ground or observing signs of water seepage along the pipeline. This approach is inefficient and heavily influenced by environmental noise. Monitoring methods based on flow meters and pressure gauges are point-based, only reflecting operating parameters at the instrument's installation location. They cannot effectively detect minor leaks along the pipeline or leaks located in blind spots between instruments, failing to meet the full-range coverage requirements for long-distance water transmission pipelines.

[0003] Distributed acoustic sensing fiber optic technology overcomes the difficulty of long-distance continuous monitoring using traditional point-based monitoring methods, achieving distributed sensing of vibration signals along the pipeline by deploying sensing optical cables. However, this technology has four significant drawbacks in practical applications of water supply pipeline leak monitoring. First, existing research and engineering practices mostly focus on deploying optical fibers externally to the pipe wall. This requires excavation of existing buried pipelines to expose the pipe wall, resulting in long construction periods and high costs. Furthermore, the leakage acoustic signal undergoes significant attenuation after passing through the pipe wall and surrounding soil, leading to a reduced signal-to-noise ratio and affecting the accuracy of subsequent leak identification. Second, some solutions attempt to use water flow dynamics to send the optical cable into the pipeline, but relying solely on simple hydraulic traction without process control means the final posture of the optical cable inside the pipeline is randomly distributed, failing to guarantee the consistency of acoustic coupling between the optical cable and the pipe wall, resulting in significant differences in signal quality at different locations. Third, since the actual deployment of the optical cable inside the pipeline is unknown, it is impossible to establish a correspondence between the cable's length coordinates and the pipeline's actual spatial coordinates. Directly using the cable length coordinates for leak location will introduce systematic errors. Fourth, under actual operating conditions of water supply pipelines, the water flow velocity and pressure inside the pipe are high, and the background noise energy is strong. Conventional filtering and frequency domain analysis methods are difficult to effectively identify the weak acoustic signals caused by minute leaks in complex noise environments.

[0004] The aforementioned problems limit the large-scale engineering application of distributed acoustic sensing fiber optic technology in the field of water supply pipeline leakage monitoring. There is an urgent need for a technical solution that can achieve controllable deployment of optical cables without interrupting water supply, ensure stable posture after deployment, establish a spatial mapping relationship between optical cables and pipelines, and accurately identify minute leakage signals under high background noise. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a DAS leakage monitoring method for water supply pipelines based on hydraulic traction and attitude control, thereby resolving the issues present in the prior art.

[0006] In a first aspect, to achieve the above objectives, the present invention provides a DAS leakage monitoring method for water supply pipelines based on hydraulic traction and attitude control, comprising the following steps: The sensing optical cable is sent into the water supply pipeline by hydraulic traction through the delivery cabin. During the transmission of the optical cable, the back Rayleigh scattering signal is collected in real time by distributed acoustic sensing equipment and demodulated to obtain phase information. The strain rate along the length of the optical cable is calculated based on the phase information. The real-time state of the optical cable in the pipeline is determined based on the strain rate characteristics. The valve opening and the optical cable feeding speed are adjusted to control the deployment process. After the optical cable reaches the recovery cabin and is deployed, the historical data of strain rate change recorded during the traction process is used to infer the attitude of each section of the optical cable inside the pipe, and a segmented mapping relationship between the optical cable length coordinates and the actual spatial coordinates of the pipe is established accordingly. During the pipeline leak monitoring phase, the solid-borne acoustic signal from the pipe wall and the acoustic signal from the water body simultaneously coupled by the optical cable are extracted. A multi-dimensional feature vector is constructed and input into a trained classifier, which outputs the leak probability and determines the leak location based on the segmented mapping relationship.

[0007] Optionally, the process of sending the sensing optical cable into the pipeline includes: fixing the optical cable inlet using the delivery chamber, controlling the optical cable delivery rate using a manual cable feeder, and collecting the end of the optical cable downstream of the pipeline using a recovery chamber, with the water flow in the pipeline regulated by valves.

[0008] Optionally, the process of judging and adjusting the real-time status of the optical cable includes: when the absolute value of the strain rate is lower than the first threshold, the optical cable is determined to be stuck, the valve opening is increased and the cable feeding speed is reduced; when the rate of change of the strain rate exceeds the second threshold, the optical cable is determined to be bent, and the cable feeding speed is reduced; when the rate of change of the strain rate exceeds the second threshold and the strain rate increases, the optical cable is determined to be overstretched, and the valve opening is reduced.

[0009] Optionally, the process of reverse-engineering the intra-pipe attitude of each section of the optical cable and establishing a mapping relationship includes: identifying the bottom section, suspended section, bending section and stacked section by the strain rate change characteristics recorded during the traction process along the length of the optical cable, dividing the optical cable into several sections with the attitude change point as the boundary, assigning a corresponding spatial transformation coefficient to each section, and establishing a segmented mapping table from the optical cable length coordinates to the actual spatial coordinates of the pipeline.

[0010] Optionally, the process of constructing a multidimensional feature vector includes: separating the solid acoustic signal from the pipe wall and the water acoustic signal through digital bandpass filtering, calculating the ratio of the energy of the pipe wall acoustic signal to the energy of the water acoustic signal, the arrival time difference between the pipe wall acoustic signal and the water acoustic signal, and the dominant frequency of the pipe wall acoustic signal, thus forming a three-dimensional feature vector.

[0011] Optionally, the process of outputting the leakage probability includes: inputting the multidimensional feature vector into a support vector machine classifier, converting the classifier's output decision value into a leakage probability value through a sigmoid function, and determining that a leakage event has occurred when the probability value is greater than a set threshold.

[0012] Optionally, the process of determining the leak location includes: when a leak event is determined to have occurred, using the segmented mapping relationship to convert the optical cable length coordinates of the detected leak signal into the actual spatial coordinates of the pipeline to obtain the location of the leak point.

[0013] Secondly, the present invention also provides a computer terminal device, comprising: One or more processors; A memory, coupled to the processor, for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the steps of the DAS leakage monitoring method for water supply pipelines based on hydraulic traction and attitude control in the first aspect described above.

[0014] Thirdly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, it implements the steps of the water supply pipeline DAS leakage monitoring method based on hydraulic traction and attitude control described in the first aspect above.

[0015] Fourthly, the present invention also provides a computer program product, including a computer program, characterized in that, when the computer program is executed by a processor, it implements the steps of the water supply pipeline DAS leakage monitoring method based on hydraulic traction and attitude control in the first aspect described above.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: This invention provides a DAS (Digital Angle and Sensor) leakage monitoring method for water supply pipelines based on hydraulic traction and attitude control. By monitoring the strain rate of the optical cable in real time during hydraulic traction and dynamically adjusting the traction parameters, controllable deployment and attitude management of the optical cable within the pipeline are achieved without interrupting water supply. The actual spatial distribution of the optical cable is reconstructed using historical strain data recorded during the traction process, establishing a segmented mapping relationship between the cable length coordinates and the pipeline spatial coordinates, eliminating positioning errors caused by cable bending or suspension. During the monitoring phase, multi-dimensional feature vectors are constructed by extracting the solid-state acoustic signals from the pipe wall and the acoustic signals from the water body simultaneously coupled to the optical cable. These vectors are then used by a classifier to output the leakage probability, improving the ability to identify minute leakage signals in high background noise environments. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart illustrating a DAS leakage monitoring method for water supply pipelines based on hydraulic traction and attitude control, according to an embodiment of the present invention. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0020] Example 1 like Figure 1 As shown, this embodiment provides a DAS leakage monitoring method for water supply pipelines based on hydraulic traction and attitude control, including: The sensing optical cable is sent into the water supply pipeline by hydraulic traction through the delivery cabin. During the transmission of the optical cable, the back Rayleigh scattering signal is collected in real time by distributed acoustic sensing equipment and demodulated to obtain phase information. The strain rate along the length of the optical cable is calculated based on the phase information. The real-time state of the optical cable in the pipeline is determined based on the strain rate characteristics. The valve opening and the optical cable feeding speed are adjusted to control the deployment process. After the optical cable reaches the recovery cabin and is deployed, the historical data of strain rate change recorded during the traction process is used to infer the attitude of each section of the optical cable inside the pipe, and a segmented mapping relationship between the optical cable length coordinates and the actual spatial coordinates of the pipe is established accordingly. During the pipeline leak monitoring phase, the solid-borne acoustic signal from the pipe wall and the acoustic signal from the water body simultaneously coupled by the optical cable are extracted. A multi-dimensional feature vector is constructed and input into a trained classifier, which outputs the leak probability and determines the leak location based on the segmented mapping relationship.

[0021] Furthermore, the process of sending the sensing optical cable into the pipeline includes: fixing the optical cable inlet using the delivery chamber, controlling the optical cable delivery rate using a manual cable feeder, collecting the end of the optical cable downstream of the pipeline using the recovery chamber, and regulating the water flow in the pipeline using valves.

[0022] Specifically, the implementation process of this embodiment includes: One end of the sensing optical cable is connected to the DAS device via a jumper and sent into the pipeline through the delivery compartment. The feeding rate of the optical cable is controlled by a manual cable feeder.

[0023] The sensing optical cable module consists of an optical fiber core unit, a coating layer unit, an armor layer unit, and an outer protective sleeve unit.

[0024] Overall parameters of the sensing optical cable: specific gravity of 1.05~1.15g / cm³, outer diameter of 2.5~4.0mm.

[0025] From the inside out, they are: fiber core, coating layer, armor layer, and outer protective sleeve.

[0026] The hydraulic traction module consists of a drop chamber, a manual cable feeder, a recovery chamber, and manual valves.

[0027] The specific implementation process includes: As the optical fiber moves inside the pipe, the water flow generates friction, causing a change in refractive index and producing a raw signal. This signal is received and demodulated into phase data by the DAS device. The phase data is then input into a laptop connected via Ethernet, which calculates the real-time strain rate.

[0028] DAS Acquisition Module: Connects the DAS to the sensing optical cable via a jumper cable. The DAS device emits coherent light pulses, which enter the optical cable. Due to the movement of the optical cable inside the pipe, the refractive index changes, generating backscattered Rayleigh light, which is received by the DAS device and demodulated to output phase data.

[0029] Strain rate calculation module: ; Where wavelength λ = 1550 nm, refractive index n = 1.468, z is the coordinate along the length of the optical cable (unit: m), t is time (unit: s), and ε is strain rate (unit: μɛ).

[0030] Furthermore, the process of judging and adjusting the real-time status of the optical cable includes: when the absolute value of the strain rate is lower than the first threshold, it is determined that the optical cable is stopped, the valve opening is increased and the cable feeding speed is reduced; when the rate of change of the strain rate exceeds the second threshold, it is determined that the optical cable is bent, and the cable feeding speed is reduced; when the rate of change of the strain rate exceeds the second threshold and the strain rate increases, it is determined that the optical cable is overstretched, and the valve opening is reduced.

[0031] Specifically, the implementation process of this embodiment includes: To ensure the pipeline reaches the recovery chamber smoothly, the condition of the optical cable inside the pipeline is determined based on the strain rate, and the hydraulic traction module is adjusted accordingly.

[0032] Module for determining the status of optical cables within the conduit and adjusting optical cables: ① When |ε| < 10μɛ, the optical cable is stationary. At this time, the valve is opened wider to increase the water pressure and slow down the cable feeding speed.

[0033] ②When |∂ε / ∂t|>100μɛ / s, the optical cable is going around a bend, so slow down the cable feeding speed at this time.

[0034] ③ When |∂ε / ∂t|>100μɛ / s, the optical cable is overstretched, so close the valve to reduce water pressure and flow rate.

[0035] ④ When ε shows periodic fluctuations and is between 0.5 and 5 Hz, the optical cable is in a state of random shaking inside the tube, so finely adjust the valve opening.

[0036] ⑤ All other cases were judged as normal.

[0037] Furthermore, the process of reverse-engineering the intra-pipe attitude of each section of the optical cable and establishing a mapping relationship includes: identifying the bottom-attached section, suspended section, bending section and stacked section by the strain rate change characteristics recorded during the traction process along the length of the optical cable, dividing the optical cable into several sections with the attitude change point as the boundary, assigning a corresponding spatial transformation coefficient to each section, and establishing a segmented mapping table from the optical cable length coordinates to the actual spatial coordinates of the pipeline.

[0038] Specifically, the implementation process of this embodiment includes: Based on the strain rate-cable state recorded during transportation, the specific state distribution of the optical cable after arriving at the recovery capsule is deduced. Points of state change are considered as segmentation points, and a segmented mapping table M between optical cable coordinates and pipeline coordinates is established.

[0039] In-duct optical cable distribution status reverse estimation module: ①Bottom: The strain value is relatively stable, with fluctuations of less than 50 μɛ; ②Suspension: The strain value shows periodic fluctuations, with a frequency of less than 5 Hz and an amplitude of less than 200 μɛ; ③ Bending: The strain value suddenly reaches a peak; ④ Accumulation: The strain value is relatively small; Segmented mapping table M module: ; in, For the first The starting length coordinates of a segment of optical cable are obtained by recording the strain rate distribution along the cable length. When the cable changes from being close to the ground to being suspended, the strain changes from stable to low-frequency oscillation, and the starting point of the oscillation is considered the break point; when the cable changes from being suspended to bending, the strain changes from low-frequency oscillation to a sharp peak, and the starting point of the peak is considered the break point; when the cable changes from bending to being close to the ground, the strain peak ends and returns to stability, and the ending point of the peak is considered the break point. For the first The actual starting length coordinates of the pipe corresponding to the starting point of the optical cable segment are obtained by the DAS signal generated by tapping the pipe. The conversion factor is 1, since the bottom section is almost parallel to the pipe and the length is basically the same; based on experience, it is 0.95 and 1.1 when the optical cable is in a floating state and a bent state, respectively.

[0040] Furthermore, the process of constructing a multidimensional feature vector includes: separating the solid acoustic signal from the pipe wall and the water acoustic signal through digital bandpass filtering, calculating the ratio of the energy of the pipe wall acoustic signal to the energy of the water acoustic signal, the arrival time difference between the pipe wall acoustic signal and the water acoustic signal, and the dominant frequency of the pipe wall acoustic signal, thus forming a three-dimensional feature vector.

[0041] Specifically, the implementation process of this embodiment includes: After the fiber optic cable laying and mapping table M are completed, monitoring of pipeline leakage signals begins. When the acoustic vibration signal generated by the leak couples through the pipe wall and water to the sensing fiber optic cable, the fiber optic cable transmits the back Rayleigh scattering light signal carrying the vibration information to the DAS. The DAS outputs the raw phase and calculates the eigenvector using a laptop computer. .

[0042] Feature vector Creating a module: ① A digital bandpass filter is used to extract the effective signals related to the leak, separating the pipe wall noise and the water noise.

[0043] ② It consists of energy ratio, time difference of arrival, and dominant frequency, and the formula is as follows: ; in, This represents the energy ratio of the optical cable at point z. and The noise signals of the pipe wall and the water body are obtained after digital bandpass filtering; t0 is the start time of the analysis window; T is the length of the analysis window, which is 0.5s in this embodiment.

[0044] ; Where Δt is the time difference between the water noise signal and the pipe wall noise signal being received; and This represents the peak time of the pipe wall noise signal and water noise at point Z, within the analysis window length. The peak time is found within [t0, t0+T]. ; in, The dominant frequency of the pipe wall noise of the optical cable at point Z, which is within the analysis window; For Fourier transform operators; The calculation is as follows: .

[0045] Furthermore, the process of outputting the leakage probability includes: inputting the multidimensional feature vector into a support vector machine classifier, and converting the classifier's output decision value into a leakage probability value through a sigmoid function. When the probability value is greater than a set threshold, a leakage event is determined to have occurred.

[0046] Furthermore, the process of determining the leak location includes: when a leak event is determined to have occurred, using the segmented mapping relationship to convert the optical cable length coordinates of the detected leak signal into the actual spatial coordinates of the pipeline, thereby obtaining the location of the leak point.

[0047] Specifically, the implementation process of this embodiment includes: The calculated feature vectors Input a well-trained SVM classifier. The decision value output by the classifier is converted into a probability through the Sigmoid function. When the leakage probability is greater than a set threshold, the location of the leakage point is obtained through a coordinate transformation formula.

[0048] Leakage detection module: Sigmoid function: ; like A value >0.6 indicates a leak; at this point, the leak point is located using a segmented mapping table M and a coordinate transformation formula. ; in, These are the actual coordinates of the pipeline; It is an indicator function, when Falling in the range If the value is 1, then the value is 0; otherwise, the value is 0.

[0049] If 0.4 < ≤0.6 is marked as suspicious and requires manual review; like ≤0.4: Determined as no leakage.

[0050] Example 2 In this embodiment, a computer terminal device is provided, including: One or more processors; A memory, coupled to the processor, for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the steps of the above-described method for monitoring leaks in water supply pipelines using a DAS based on hydraulic traction and attitude control.

[0051] In this embodiment, a computer-readable storage medium is also provided, on which a computer program is stored. When the computer program is executed by a processor, it implements the steps of the above-described method for monitoring leaks in a water supply pipeline based on hydraulic traction and attitude control.

[0052] In this embodiment, a computer program product is also provided, including a computer program, characterized in that, when the computer program is executed by a processor, it implements the steps of the above-described method for monitoring leaks in water supply pipelines based on hydraulic traction and attitude control.

[0053] This invention provides a DAS (Digital Angle and Sensor) leakage monitoring method for water supply pipelines based on hydraulic traction and attitude control. By monitoring the strain rate of the optical cable in real time during hydraulic traction and dynamically adjusting the traction parameters, controllable deployment and attitude management of the optical cable within the pipeline are achieved without interrupting water supply. The actual spatial distribution of the optical cable is reconstructed using historical strain data recorded during the traction process, establishing a segmented mapping relationship between the cable length coordinates and the pipeline spatial coordinates, eliminating positioning errors caused by cable bending or suspension. During the monitoring phase, multi-dimensional feature vectors are constructed by extracting the solid-state acoustic signals from the pipe wall and the acoustic signals from the water body simultaneously coupled to the optical cable. These vectors are then used by a classifier to output the leakage probability, improving the ability to identify minute leakage signals in high background noise environments.

[0054] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for DAS leakage monitoring of water supply pipelines based on hydraulic traction and attitude control, characterized in that, Includes the following steps: The sensing optical cable is sent into the water supply pipeline by hydraulic traction through the delivery cabin. During the transmission of the optical cable, the back Rayleigh scattering signal is collected in real time by distributed acoustic sensing equipment and demodulated to obtain phase information. The strain rate along the length of the optical cable is calculated based on the phase information. The real-time state of the optical cable in the pipeline is determined based on the strain rate characteristics. The valve opening and the optical cable feeding speed are adjusted to control the deployment process. After the optical cable reaches the recovery cabin and is deployed, the historical data of strain rate change recorded during the traction process is used to infer the attitude of each section of the optical cable inside the pipe, and a segmented mapping relationship between the optical cable length coordinates and the actual spatial coordinates of the pipe is established accordingly. During the pipeline leak monitoring phase, the solid-borne acoustic signal from the pipe wall and the acoustic signal from the water body simultaneously coupled by the optical cable are extracted. A multi-dimensional feature vector is constructed and input into a trained classifier, which outputs the leak probability and determines the leak location based on the segmented mapping relationship.

2. The method according to claim 1, characterized in that, The process of sending the sensing optical cable into the pipeline includes: fixing the optical cable inlet using the delivery chamber, controlling the optical cable delivery rate using a manual cable feeder, collecting the end of the optical cable downstream of the pipeline using the recovery chamber, and regulating the water flow in the pipeline using valves.

3. The method according to claim 1, characterized in that, The process of judging and adjusting the real-time status of the optical cable includes: when the absolute value of the strain rate is lower than the first threshold, the optical cable is determined to be stuck, the valve opening is increased and the cable feeding speed is reduced; when the rate of change of the strain rate exceeds the second threshold, the optical cable is determined to be bent, and the cable feeding speed is reduced; when the rate of change of the strain rate exceeds the second threshold and the strain rate increases, the optical cable is determined to be overstretched, and the valve opening is reduced.

4. The method according to claim 1, characterized in that, The process of reverse-engineering the intra-pipe attitude of each section of the optical cable and establishing a mapping relationship includes: identifying the bottom section, suspended section, bending section and stacked section by the strain rate change characteristics along the length of the optical cable recorded during the traction process, dividing the optical cable into several sections with the attitude change point as the boundary, assigning corresponding spatial transformation coefficients to each section, and establishing a segmented mapping table from the optical cable length coordinates to the actual spatial coordinates of the pipeline.

5. The method according to claim 1, characterized in that, The process of constructing a multidimensional feature vector includes: separating the solid acoustic signal from the pipe wall and the water acoustic signal through digital bandpass filtering, calculating the ratio of the energy of the pipe wall acoustic signal to the energy of the water acoustic signal, the arrival time difference between the pipe wall acoustic signal and the water acoustic signal, and the dominant frequency of the pipe wall acoustic signal, thus forming a three-dimensional feature vector.

6. The method according to claim 1, characterized in that, The process of outputting the leakage probability includes: inputting the multidimensional feature vector into a support vector machine classifier, converting the classifier's output decision value into a leakage probability value through a sigmoid function, and determining that a leakage event has occurred when the probability value is greater than a set threshold.

7. The method according to claim 6, characterized in that, The process of determining the location of a leak includes: when a leak event is determined to have occurred, the optical cable length coordinates that detected the leak signal are converted into the actual spatial coordinates of the pipeline using the segmented mapping relationship to obtain the location of the leak point.

8. A computer terminal device, characterized in that, include: One or more processors; A memory, coupled to the processor, for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors perform the steps of the method as described in any one of claims 1-7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1-7.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1-7.

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