Method and system for positioning blockage of detector in pipeline based on array sound wave layered inversion

Abstract

The invention discloses a method and a system for positioning blockage of a detector in a pipeline based on array sound wave layered inversion, and belongs to the technical field of buried pipeline detection. The method comprises the following steps: performing high-precision global synchronization on an internal detector clock; the blocking state is intelligently judged, and sound wave emission is triggered; the comprehensive sound velocity of an axial pipe soil medium is inversed by using a ground axial double-point receiving signal, and coarse positioning of a blocking axial interval is realized; searching and determining a ground projection center through an energy peak value of a mobile probe; a linear receiving array perpendicular to the pipeline is arranged, and sound wave travel time data propagating in the radial direction is collected; and finally, through a linearized hyperbolic travel time equation and by utilizing least square parameter estimation, the local soil sound velocity above the blockage point and the buried depth of the inner detector are subjected to combined inversion, so that accurate three-dimensional space coordinates are obtained. According to the method, through physical layering and parameter joint inversion, the influence of nonuniform soil sound velocity uncertainty is eliminated, and sub-meter-level precision blocking positioning of the detector in the pipeline is achieved in a complex geological environment.

Description

Technical Field

[0001] This application relates to the field of buried pipeline inspection technology, specifically to a method and system for high-precision three-dimensional spatial positioning of an internal detector stuck inside a pipeline by using an active sound source and a ground linear sensor array for signal acquisition and data processing. Background Technology

[0002] In the process of developing this application, the inventors discovered at least the following problems in the prior art: During operation, pressure pipelines such as long-distance oil and gas pipelines typically employ internal detectors (commonly known as "pipelines" or "pigs") to enter the pipeline interior and conduct online detection of defects such as corrosion and cracks in the pipe wall. However, due to pipeline deformation, sediment accumulation, or mechanical failure, internal detectors are at risk of becoming stuck. Once a blockage occurs, it not only interrupts the detection process but may also lead to pipeline shutdown or even safety accidents. Therefore, it is necessary to quickly and accurately determine the location of the blockage in order to carry out excavation and rescue operations.

[0003] Traditional methods for locating internal detectors primarily rely on their onboard electromagnetic transmitters and AboveGround Markers (AGMs). This method is a "through-and-go" approach, only confirming that the detector has passed a marker point. If the detector gets stuck between two marker points (typically 1-3 kilometers apart), its exact location cannot be determined. Another method is portable tracking and positioning based on ultra-low frequency electromagnetic waves. This method can track the detector even if it gets stuck, but it is affected by signal shielding from pipelines and external electromagnetic interference. The electromagnetic signal strength decreases sharply with increasing distance, resulting in a very short effective detection range, typically only a few meters.

[0004] Acoustic positioning methods offer a new approach to locating pipe blockages. However, existing acoustic positioning methods typically assume that sound waves propagate at a fixed speed in the soil medium (e.g., 340 m / s or 1500 m / s) and calculate the distance accordingly. In reality, the path of sound waves from the blocked internal detector to the surface involves multiple heterogeneous media, including the pipe medium, pipe wall, anti-corrosion layer, and soil. The sound speed in the soil is significantly affected by factors such as moisture content, compaction, and soil type, varying from 300 m / s to 2000 m / s. Using a fixed empirical sound speed value would lead to positioning errors of tens or even hundreds of meters, causing excavation operations to fail. Therefore, in non-uniform soil media, how to eliminate the systematic errors caused by the uncertainty of sound speed and achieve sub-meter level three-dimensional positioning accuracy is a pressing technical challenge in the field of pipe blockage rescue using internal detectors. Summary of the Invention

[0005] To address the technical problem of low positioning accuracy of pipe detector jamming due to uncertain soil sound velocity in the aforementioned background technology, this application provides a pipe detector jamming positioning method and system based on array acoustic wave layered inversion.

[0006] The technical solution adopted by this application to solve its technical problem is: On the one hand, a method for locating blocked detectors in pipes using array acoustic wave layered inversion is provided, including the following steps: S1, before the internal detector runs, uses an external standard time source to synchronize and calibrate the local clock of the acoustic emission control unit on the internal detector to establish a global absolute time coordinate system. S2, the internal detector monitors its movement status in real time, and when it determines that it has entered a jammed state, it triggers the subsequent acoustic signal transmission process; S3, when it is determined that the pipe is stuck, the internal detector emits an acoustic signal to the pipe medium at a preset absolute time based on the calibrated local clock. S4. Arrange at least two receiving points along the estimated axial direction of the ground pipeline to collect sound wave signals. Estimate the comprehensive sound velocity of the pipe-soil medium as the sound wave propagates along the axial direction through signal processing. Combine the absolute flight time of the signal to calculate the approximate axial distance range of the blockage point. S5. Within the defined axial distance range, move the ground receiving probe along the axial and vertical directions of the pipeline, and determine the vertical projection center position of the blockage point on the ground based on the point with the maximum received signal amplitude. S6. Using the above-mentioned projection center position as a reference, arrange a linear receiving array perpendicular to the pipe direction, collect acoustic signals, and obtain the absolute travel time vector of the received signals of each array element. S7. Construct a radial propagation model of sound waves from the inner detector to the ground array element, linearize the nonlinear travel time equation, and use the absolute travel time vector and the spatial coordinates of the array element to simultaneously infer the local soil sound velocity above the blockage point and the burial depth of the inner detector through a parameter estimation algorithm. Combined with the determined planar coordinates, the three-dimensional spatial position of the inner detector is accurately determined.

[0007] On the other hand, a pipe detector jamming location system based on array acoustic wave layered inversion is provided, comprising: The acoustic emission subsystem of the internal detector, integrated within the internal detector cabin, includes a main control unit, a high-precision clock module, a motion status monitoring module, a power amplifier module, and an acoustic transducer. The main control unit is used to perform jamming state determination and control the acoustic transducer to emit acoustic signals at a specific time after jamming. The high-precision clock module is synchronized with an external standard time source. The motion status monitoring module includes a mileage wheel module and an inertial measurement unit (IMU). The mileage wheel module is used to count the distance traveled by the internal detector, and the IMU measures the acceleration of the internal detector. The ground receiving and processing subsystem includes a GPS timing module, a multi-channel data acquisition unit, a linear sensor array, and a portable computing terminal. The GPS timing module provides a time reference synchronized with the transmitter. The linear sensor array is used to acquire surface acoustic signals. The portable computing terminal is used to receive data and execute the comprehensive sound velocity estimation of the axial soil-conduit medium, the ground center point calibration, and the joint inversion algorithm of radial stratification parameters, outputting the three-dimensional coordinates of the internal detector and the local soil sound velocity.

[0008] One of the above technical solutions has the following advantages or beneficial effects: 1. By using high-precision clock synchronization, acoustic positioning is upgraded from passive detection to active collaborative detection, which can accurately calculate the flight time using the absolute transmission time of the signal, providing an absolute time reference for positioning.

[0009] 2. A three-stage strategy of "coarse axial positioning, fine axial and radial positioning, and finally depth positioning" is adopted, and a ground-based linear sensor array is innovatively introduced in the depth positioning stage. By constructing a hyperbolic travel-time equation and linearizing it using its mathematical properties, the two strongly coupled unknown parameters of non-uniform soil sound velocity and internal detector depth are decoupled, realizing joint in-situ inversion of the two, fundamentally eliminating the systematic error caused by assuming a fixed sound velocity.

[0010] 3. Drawing on the concept of dynamic correction (NMO) velocity analysis in seismic exploration, and utilizing the redundancy of array data, a stable solution is obtained through optimization algorithms such as least squares. This enables sub-meter-level positioning accuracy even in complex and variable geological environments, greatly improving the success rate and efficiency of blockade rescue.

[0011] 4. The system is clearly structured, with the internal detector and the ground unit working together. It has a high degree of automation and intelligence, making it easy to deploy and apply quickly in the field. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating a pipe detector jamming location method based on array acoustic wave layered inversion according to an exemplary embodiment; Figure 2This is a hardware architecture block diagram of an internal detector acoustic emission subsystem according to an exemplary embodiment; Figure 3 This is a schematic diagram illustrating the principle of in-situ calibration and coarse axial positioning of ground sound velocity according to an exemplary embodiment. Detailed Implementation

[0013] To more clearly illustrate the technical features of this application, the following detailed description, in conjunction with the accompanying drawings, provides specific embodiments and examples to implement different structures of this application. To simplify the disclosure, the components and arrangements of specific examples are described below. Of course, these are merely examples and are not intended to limit the scope of this application.

[0014] like Figure 1 As shown in the figure, the pipeline detector jamming location method based on array acoustic wave layered inversion provided in this application includes the following steps: S1, before the internal detector runs, uses an external standard time source to synchronize and calibrate the local clock of the acoustic emission control unit on the internal detector, and establishes a global absolute time coordinate system.

[0015] Specifically, the synchronization calibration of the local clock of the acoustic emission control unit mounted on the internal detector using an external standard time source includes the following steps: S11, obtains PPS second pulse signal through GPS receiver module; S12, the rising edge of the PPS second pulse signal is used to trigger the clearing and resetting of the internal counter of the acoustic emission control unit to achieve phase synchronization with Coordinated Universal Time (UTC), with the synchronization error controlled within 0.5 microseconds; S13, a high-stability clock source, either a temperature-controlled crystal oscillator (OCXO) or a temperature-compensated crystal oscillator (TCXO), is used as the oscillation source for the local clock. The frequency stability of the OCXO is better than 0.05 ppm. The OCXO employs a double-layer temperature-controlled bath and maintains a frequency accuracy better than ±1 × 10⁻⁶ within its operating temperature range of 0°C to 60°C. -8 ; S14 records the time span from the synchronization completion time to the jamming time, and performs linear compensation correction on the absolute time T0 of the sound wave emission based on the nominal drift rate of the crystal oscillator.

[0016] S2, the internal detector monitors its movement status in real time, and when it determines that it has entered a jammed state, it triggers the subsequent acoustic signal transmission process.

[0017] Specifically, the internal detector monitors its motion state in real time, including the following steps: S21, the odometer data and inertial measurement unit (IMU) data are fused using the Kalman filter algorithm to estimate the motion state of the internal detector in real time. The inertial measurement unit (IMU) includes a triaxial accelerometer with a range of ±2g. S22, the internal detector is determined to be in a jammed state if and only if the mileage wheel stops counting for a period of time exceeding a preset threshold and the axial acceleration remains below the static threshold. The specific conditions for determining the jammed state are: the mileage wheel stops counting for a period of time Tstop > 30 minutes and the triaxial composite acceleration anet < 0.02g.

[0018] S3, when it is determined that the pipe is blocked, the internal detector emits an acoustic signal to the pipe medium at a preset absolute time based on the calibrated local clock.

[0019] Specifically, the internal detector emits an acoustic signal to the pipeline medium at a preset absolute time based on a calibrated local clock, including the following steps: S31, the preset time point T0 is the 5th or 10th minute of UTC time; S32, emits an acoustic signal with high autocorrelation characteristics, wherein the signal is a single-frequency signal, a linear frequency modulated (LFM) signal, or a Barker code modulated pulse signal; S33, the frequency range of the acoustic signal is selected as a predetermined frequency band from 100Hz to 800Hz; S34, each transmission lasts for Tdur, with a pause interval of TER periodic signals, until the transmission continues until the jamming is released or the internal detector is removed.

[0020] S4. Arrange at least two receiving points along the estimated axial direction of the ground pipeline to collect sound wave signals. Estimate the comprehensive sound velocity of the pipe-soil medium as the sound wave propagates along the axial direction through signal processing. Combine the absolute flight time of the signal to calculate the approximate axial distance range of the blockage point.

[0021] In this embodiment, the "comprehensive sound velocity of the pipe-soil medium" (also known as the axial equivalent sound velocity of the pipe-soil medium) is a core parameter. Its physical essence is the equivalent average group velocity of the sound wave along the path from the blocked internal detector to the axially arranged receiving point on the ground. It is important to clarify that the actual path of sound waves propagating from inside the pipe to the surface is extremely complex: it first propagates within the pipe medium (gas or liquid) and along the pipe wall, then penetrates the pipe wall and the anti-corrosion layer, and finally reaches the surface through upper layers of soil with different properties. This series of media constitutes a multi-layered, non-uniform "pipe-soil" composite waveguide structure.

[0022] This application embodiment does not require measuring the precise sound velocity of each layer of medium separately. Instead, it obtains an equivalent velocity value that comprehensively reflects the axial acoustic characteristics of the entire waveguide structure through an innovative in-situ measurement method. Specifically, by arranging two known-spaced ( The receiving point accurately measures the time difference (delay) between the arrival points of the same transmitted acoustic signal at two points. ), and use the formula The combined speed of sound can be obtained by direct calculation. .

[0023] Should Its engineering significance lies in the fact that it represents the overall average velocity of sound waves propagating along this specific axial path from the sound source to the ground surface. It is an equivalent parameter obtained directly through field measurements and applicable to the local environment of the current blockage point. Substituting it into the formula... The axial distance of the blockage point can then be calculated. By using this in-situ measurement of the comprehensive sound velocity, the embodiments of this application fundamentally avoid the positioning errors of tens or even hundreds of meters caused by traditional methods that assume a fixed empirical sound velocity (such as 340m / s or 1500m / s), thus laying a reliable benchmark for subsequent accurate positioning.

[0024] Specifically, the step of arranging at least two receiving points along the estimated axial direction of the ground pipeline to collect sound wave signals and estimating the combined sound velocity of the pipe-soil medium along the axial direction of the sound waves through signal processing includes the following steps: S41: Two known-distance... are arranged on the ground along the pipe axis. The probes, serving as both the first and second receiving points, are each equipped with an independent GPS timing module to accurately timestamp the received signals using UTC. The first receiving point receives... Second receiving point ; S42: Estimating the time delay between two received signals based on a time delay estimation algorithm (Generalized Cross-Correlation-Phase Transformation GCC-PHAT algorithm). Specifically: calculate the cross-power spectrum of the two received signals, perform phase weighting on the cross-power spectrum, obtain the generalized cross-correlation function through inverse Fourier transform, and extract the time delay corresponding to the peak value of the generalized cross-correlation function. ,or ; S43, Calculate the estimated comprehensive sound velocity of the axially oriented pipe-soil medium: ; S44, Calculate the axial distance from the blockage point to the proximal probe: ,in The absolute moment when the sound wave arrives at the near-end probe. The launch time after drift compensation. This is due to system hardware response delay.

[0025] The method described in S42 can also be used to estimate the time delay between the known transmitter signal and the near-end probe. ,but .

[0026] S5. Within the defined axial distance range, move the ground receiving probe along the axial and vertical directions of the pipeline, and determine the vertical projection center position of the blockage point on the ground based on the point with the maximum received signal amplitude.

[0027] Specifically, step S5 includes the following steps: S51, within the axial distance range, move the ground receiving probe along the pipeline axis with a first preset step size, record the amplitude of the acoustic signal received at each point, mark the point with the maximum amplitude as the axial center position, the first preset step size is 5 meters, the acoustic signal amplitude is the normalized voltage value, and is represented by the peak value or root mean square value of the detector output voltage. S52, at the axial center position, the ground receiving probe is moved perpendicular to the pipe axis with a second preset step length, and the amplitude of the acoustic signal received at each point is recorded. The point with the maximum amplitude is determined as the vertical projection center position of the blockage point on the ground. The second preset step length is 0.1 meters.

[0028] S6. Using the aforementioned projection center position as a reference, arrange a linear receiving array perpendicular to the pipe direction to collect acoustic signals and obtain the absolute travel time vector of the received signals of each array element.

[0029] Specifically, the arrangement of a linear receiving array perpendicular to the pipe direction, based on the aforementioned projection center position, includes the following steps: S61, with the center of the vertical projection of the blockage point on the ground as the reference point, a linear receiving array is arranged in a direction perpendicular to the pipeline. S62, the linear receiving array consists of at least 3 vertical component detectors, each detector is arranged in a straight line at a preset interval, and the vertical component detector adopts a high-power piezoelectric ceramic stack structure, the piezoelectric ceramic model is PZT-4 or PZT-8. S63 synchronously acquires the acoustic signals of each array element through a multi-channel data acquisition unit. The acquired acoustic signals are processed by a low-pass filter to remove high-frequency noise interference.

[0030] S7. Construct a radial propagation model of sound waves from the inner detector to the ground array element, linearize the nonlinear travel time equation, and use the absolute travel time vector and the spatial coordinates of the array element to simultaneously infer the local soil sound velocity above the blockage point and the burial depth of the inner detector through a parameter estimation algorithm. Combined with the determined planar coordinates, the three-dimensional spatial position of the inner detector is accurately determined.

[0031] Specifically, step S7 includes the following steps: S71, a radial propagation forward model is constructed based on ray theory, and the travel time of the i-th array element satisfies the hyperbolic equation: ,in Let be the absolute observation time of the i-th array element. H is the horizontal distance of the i-th array element relative to the axial center, and H is the burial depth of the inner detector. This refers to the local soil sound velocity; S72, Squaring and rearranging both sides of the hyperbola equation, we obtain the linearized observation equation: ,in The gradient parameter is related to the square of the medium's slowness. The intercept parameter is related to the square of the equivalent depth; S73, construct the design matrix H and the observation vector Y, where H is derived from... The value is composed of Y. Value composition; S74, Solving for the parameter vector using least squares estimation. and : , in, It is a special case of the Vandermonde matrix; S75, based on the inversion-obtained parameters α and β, solve the physical model: Local soil sound velocity estimation: ; Internal detector burial depth estimation: .

[0032] In step S75, the precise three-dimensional spatial position of the internal detector is determined by combining the planar coordinates determined in step S5. Specifically, the planar coordinates of the vertical projection center of the blocking point on the ground determined in step S5 are (O... x O y If the internal detector's three-dimensional spatial coordinates are (O), then the internal detector's three-dimensional spatial coordinates are (O). x O y ,- ).

[0033] It should be noted that the hyperbolic equation in step S71 is a simplified model based on the ray theory of sound waves propagating in a straight line in a homogeneous, isotropic medium. In actual pipeline installation environments, the soil medium above the blockage point may exhibit certain non-uniformity and stratification characteristics. This application equates the actual complex multi-layered waveguide structure of 'pipe medium-pipe wall-corrosion protection layer-soil' and the non-uniformity of the soil to a homogeneous medium layer from the sound source (internal detector) to the surface receiving point, and uses a local average sound velocity v soil This simplification is used to characterize the acoustic properties of the equivalent medium. This simplification is reasonable and practical in engineering because: firstly, for a localized area centered directly above the blockage point with a limited horizontal expansion range (usually several times the burial depth H), the changes in soil properties are relatively gradual and can be approximated as uniform; secondly, the core of this method lies in utilizing the travel time data t observed by a ground linear array. i Horizontal distance x i The mathematical relationship between them (i.e., the hyperbolic law) is used to simultaneously solve for the equivalent average speed of sound v using an inversion algorithm. soil The essence of this simplified model, along with the burial depth H, is to find an optimal homogeneous medium model to fit the actual observation data. Therefore, this simplified model does not require the soil to be strictly homogeneous, but rather relies on the inverted v... soil This serves as the equivalent sound velocity for the local area, effectively eliminating the influence of sound velocity uncertainty and achieving high-precision positioning. This positioning concept draws on the dynamic correction (NMO) velocity analysis technique in seismic exploration and has proven effective in the specific scenario described in this application.

[0034] As one possible implementation of this embodiment, the pipeline detector blockage localization method based on array acoustic wave layer inversion further includes step S8: The inversion results are output in real time through a portable edge computing terminal, which has a built-in floating-point unit (FPU) configured to perform Fast Fourier Transform (FFT), generalized cross-correlation operations, and nonlinear least squares regression algorithms.

[0035] This application also provides a pipe detector jamming location system based on array acoustic wave layered inversion, including: The acoustic emission subsystem of the internal detector is integrated into the internal detector cabin; such as Figure 2As shown, the acoustic emission subsystem of the internal detector includes a main control unit, a high-precision clock module, a motion state monitoring module, a power amplification module, and an acoustic transducer. The main control unit is used to perform jamming state judgment and control the acoustic transducer to emit acoustic signals at a specific time after jamming. The high-precision clock module is synchronized with an external standard time source. The motion state monitoring module includes a mileage wheel module and an inertial measurement unit (IMU). The mileage wheel module is used to count the running distance of the internal detector, and the IMU measures the running acceleration of the internal detector. The acoustic transducer is fastened to the metal frame of the internal detector through rigid mechanical connectors, so as to utilize the metal frame and pipe wall of the internal detector as acoustic waveguides. The ground receiving and processing subsystem includes a GPS timing module, a multi-channel data acquisition unit, a linear sensor array, and a portable computing terminal. The GPS timing module provides a time reference synchronized with the transmitter. The linear sensor array is used to acquire surface acoustic signals. The portable computing terminal is used to receive data and execute the comprehensive sound velocity estimation of the axial soil-conduit medium, the ground center point calibration, and the joint inversion algorithm of radial stratification parameters, outputting the three-dimensional coordinates of the internal detector and the local soil sound velocity.

[0036] The motion state monitoring module in the acoustic emission subsystem of the internal detector includes a mileage wheel encoder interface and a triaxial accelerometer. The linear sensor array in the ground receiving and processing subsystem consists of at least three vertical component detectors. The algorithms built into the portable computing terminal include a generalized cross-correlation time delay estimation algorithm and a t-based algorithm. 2 -x 2 Parameter inversion algorithm for domain linear regression.

[0037] The key to this application lies in two points: first, high-precision time synchronization ensures the accuracy of absolute time-of-flight measurement; second, by utilizing observation data from a ground-based linear array, and through mathematical transformation and inversion algorithms, the unknown local medium sound source and its depth are simultaneously determined. The technical solution will be described in detail below with reference to specific embodiments.

[0038] I. Detailed Implementation of the Method Described in this Application: Regarding S1 (clock synchronization calibration): This is fundamental for achieving absolute time-of-flight (TOF) measurements. In this embodiment, a GPS / BeiDou timing module can be connected via an external interface before the internal detector launches. The rising edge of the 1PPS (pulse per second) signal output by the timing module triggers the clearing and resetting of the internal clock counter, synchronizing its local clock phase with Coordinated Universal Time (UTC). The local clock oscillation source can be a high-stability clock source such as an oven-controlled crystal oscillator (OCXO) or a temperature-compensated crystal oscillator (TCXO), with a frequency stability better than 0.05ppm. Since a considerable time may occur between synchronization completion and jamming, the subsequent launch time T0 needs to be linearly compensated and corrected according to the nominal drift rate of the crystal oscillator to ensure the accuracy of the launch time. The synchronization error should be controlled within the microsecond range, for example, less than 0.5μs.

[0039] Regarding S2 (Stuck State Determination): The internal detector needs to autonomously determine whether a stuck state has occurred. In the embodiment, the motion state monitoring module may include an odometer wheel encoder and an inertial measurement unit (IMU, including a triaxial accelerometer). The main control unit (such as an ARM Cortex-M4 processor) fuses the odometer pulse signal and acceleration data using a Kalman filter algorithm to estimate the speed and acceleration of the internal detector in real time. A stuck state is determined when the following conditions are met simultaneously: 1) The duration of the odometer wheel pulse counting stop exceeds a preset threshold (e.g., 30 minutes); 2) The triaxial composite acceleration measured by the IMU remains below a threshold representing stillness (e.g., 0.02g, to exclude instantaneous signals generated by minor impacts). After a stuck state is determined, the system can enter a low-power standby state, waiting for the preset hourly launch time.

[0040] Regarding S3 (Active Sound Source Excitation): After the blockage is detected, the internal detector activates the acoustic transducer at the compensated and corrected absolute UTC hour (e.g., every 5 or 10 minutes). The emitted acoustic signal must have high autocorrelation characteristics to facilitate subsequent time delay estimation. In this embodiment, the signal can be a single-frequency signal, a linear frequency modulated (Chirp) signal, or a Barker code modulated pulse signal. The frequency range is preferably in the low-frequency band of 100Hz to 800Hz to enhance penetration in the soil medium and resistance to multipath interference. The acoustic transducer is rigidly fastened to the metal frame of the internal detector via a rigid connector, utilizing the metal frame and pipe wall as acoustic waveguides to improve energy transmission efficiency.

[0041] Regarding S4 (coarse axial positioning): The purpose of this step is to quickly locate the pipe section where the blockage point is located. Based on the internal detector's operation record, the operator places two known-spaced markers L on the ground above the potentially blocked pipe section, along the pipe's axial direction. axial (For example, 100 meters) receiving probes (probes A and B). The two probes synchronously acquire the acoustic signal s. A (t) and sB (t). The ground receiver obtains the precise UTC time through its own GPS module and records the signal arrival time t. A and t B The two signals are processed using the Generalized Cross-Correlation-Phase Transform (GCC-PHAT) algorithm, and the cross-correlation function R is calculated. AB (τ), the peak value corresponds to the time delay τ peak This is the time difference between the sound wave traveling from probe A to probe B. From this, the combined sound velocity of the axially equivalent pipe-soil medium can be estimated: Subsequently, the absolute arrival time t of the proximal probe (such as probe A) is used. A and the known absolute launch time T emission Calculate the absolute flight time Δt = t A - T emission Subtract the known system hardware latency δ tsys Ultimately, the axial distance from the jamming point to probe A is... Based on the D value and the geographic coordinates of probe A, a coarse location point P and a confidence interval (e.g., 50 meters before and after point P) can be marked on the map.

[0042] Regarding S5 (Preliminary Ground Position Calibration): A more refined ground search is performed within the confidence interval near the coarse positioning point P. First, along the pipe axis, a single high-sensitivity receiving probe is moved in small steps (e.g., 5 meters) to measure the amplitude of the received acoustic signal at each point (e.g., the peak or root mean square value of the detector output voltage). The point X with the largest amplitude is recorded. max This point is considered to be directly above the blockage point along the pipe's axial direction. Then, at X... max At a location perpendicular to the pipe's direction, move the probe laterally in smaller increments (e.g., 0.1 meters), recording the signal amplitude as well, and find the point Y with the largest amplitude. max Point (X) max Y max The position O is the center of the vertical projection of the internal detector onto the ground. This method is based on the physical principle that sound wave energy is strongest when it propagates to the Earth's surface directly above it.

[0043] Regarding S6 (radial array observation): Using the ground center point O determined in the previous step as a reference, a linear receiving array is arranged. This array consists of at least three (preferably five or more) vertical component geophones or high-sensitivity piezoelectric sensors, arranged at equal or non-equal intervals along a straight line perpendicular to the pipe direction. The center of the array should coincide with or be as close as possible to point O. Each array element (sensor) synchronously records the acoustic signal through a multi-channel data acquisition unit, and a GPS timing module adds a precise UTC timestamp to each sampling point. The accurate arrival time t of the first arrival wave of the acoustic signal on each array element channel is extracted.i (i=1,2,...,N), forming the absolute travel time vector T obs = [t1, t2, ..., t N At the same time, the horizontal offset distance xi of each array element relative to the center point O is precisely measured.

[0044] Regarding S7 (layered parameter joint inversion): This is the core step in achieving high-precision positioning. Assuming the sound wave propagates directly from the point source (the blocked internal detector) to each array element on the ground surface in the form of a volume wave, and the propagation path is a straight line, then the travel time of the i-th array element satisfies the hyperbolic equation: , where H is the burial depth of the internal detector (to be determined). Let be the average sound velocity of the local soil above the blockage point (to be determined). To solve simultaneously... And H, square both sides of the equation and rearrange: Let Y i = , X i = , ,β = Then we obtain the linear observation equation: Y i = Based on the observation data of all array elements (X) i Y i By using linear regression with the least squares (LS) or weighted least squares (WLS) method, the parameters α and β can be robustly estimated. Then, physical parameters are inverted: local soil sound velocity... ; Burial depth of internal detector At this point, combining the ground center point plane coordinates (O) obtained in step S5... x O y By combining the depth H obtained from the inversion in this step, the complete three-dimensional spatial coordinates (O) of the internal detector are obtained. x, O y This method essentially applies the dynamic correction (NMO) velocity analysis technique from seismic exploration to the specific scenario described in this application, cleverly decoupling sound velocity and depth by utilizing the redundancy of array data.

[0045] II. System Hardware Configuration Example Example of an internal detector acoustic emission subsystem: The main control unit uses a low-power microprocessor, such as an ARM Cortex-M4; the high-precision clock module uses an OCXO, model DOIFI-KR2-10M, with a frequency of 10MHz and a temperature drift of 0.01ppm. Its frequency accuracy is better than ±1×10⁻⁶ within an operating temperature range of 0℃ to 60℃. -8The motion monitoring module includes an interface for receiving odometer pulses and a triaxial MEMS accelerometer with a measurement range of ±2g. The power amplification module amplifies the weak digital signal to drive the acoustic transducer. The acoustic transducer can be made of piezoelectric ceramic or magnetostrictive material, with an operating frequency band covering 100-800Hz. The entire subsystem is sealed within the internal detector chamber, providing excellent pressure resistance and waterproofing.

[0046] Ground Reception and Processing Subsystem Implementation Example: The GPS timing module provides 1PPS and UTC time information. The linear sensor array consists of five vertical component moving-coil detectors with a natural frequency of 10Hz, spaced 2 meters apart. The detectors employ a high-power piezoelectric ceramic (PZT-4 or PZT-8) stacked structure. The multi-channel data acquisition unit has a 24-bit ADC and a dynamic range greater than 80dB, with a sampling rate no less than 2kHz. The portable computing terminal can be a ruggedized industrial tablet PC with built-in specially developed positioning software. This software integrates the following algorithm modules: data synchronization and preprocessing module, GCC-PHAT delay estimation module, axial distance calculation module, energy peak search module, and least squares-based t... 2 -x 2 The linear inversion module can display the inverted soil sound velocity, internal detector depth, and three-dimensional coordinates in real time on site.

[0047] III. Example Data from the Implementation Plan The following is a data example from a specific embodiment to illustrate the implementation process and effects of this application: 1. Clock Synchronization and Blockage Detection: The internal detector synchronizes its clock via GPS at 8:00 AM with a synchronization error of 0.3 μs. During operation, the internal detector detects at 10:15 AM that the odometer wheel has stopped counting and the triaxial composite acceleration remains below 0.02g, indicating a blockage.

[0048] 2. Acoustic wave emission: After the blockage, the internal detector waits until the hour 10:20:00.000000 (UTC) and emits a linear frequency modulated acoustic wave signal with a frequency range of 200-600Hz for 1 second.

[0049] 3. Axial coarse positioning: such as Figure 3 As shown, ground operators deployed two axial probes in the anticipated blockage area, spaced L=100m apart. Probe A recorded the arrival time of the sound wave at 10:20:01.250000, and probe B recorded the arrival time at 10:20:01.330000. The time delay τ=0.080000s was calculated using the GCC-PHAT algorithm, and the combined sound velocity v of the axial pipe-soil medium was... group=1250m / s. The calculated distance D from the blocking point to probe A is 1250×(1.250000-0.000200)=1562.25 meters (after deducting system delay of 0.2ms).

[0050] 4. Ground projection center calibration: At approximately 1562 meters along the pipeline axis, move the probe in 5-meter increments. The point of maximum signal amplitude is measured at 1564 meters. At this point, move the probe perpendicular to the pipeline in 0.1-meter increments. The point of maximum signal amplitude is measured 0.3 meters to the left of the pipeline centerline. Determine the ground projection center position O.

[0051] 5. Array observation data: A linear array of 5 detectors centered at point O, spaced 2 meters apart. The measured absolute travel time vector (unit: ms) is: t=[8.94, 6.32, 5.00, 6.32, 8.94].

[0052] 6. Joint parameter inversion: Transforming the data to t 2 -x 2 The domain, obtained using the least squares method, yields α = 4.0 × 10⁻⁶. -6 s 2 / m 2 β = 25.0 × 10 -6 s 2 The inversion yielded a local soil sound velocity v = 500 m / s and an internal detector burial depth H = 2.5 m. Combined with the ground projection center coordinates, the precise three-dimensional position of the internal detector was obtained.

[0053] IV. Explanation of Proper Nouns Generalized Cross-Correlation-Phase Transform (GCC-PHAT): An algorithm for estimating the time delay between two signals. It performs phase-weighted summation of the cross-power spectrum in the frequency domain (i.e., retaining only phase information), then inversely transforms it back to the time domain to obtain the generalized cross-correlation function. The peak position of this function is the estimated time delay. It exhibits good robustness to reverberation environments.

[0054] Dynamic time-of-arrival correction (NMO): A processing technique in seismic exploration used to correct for differences in seismic wave arrival times caused by varying shot-receiver offsets. Its core equation is the hyperbolic time-distance equation. This application draws upon its mathematical form and data inversion concept.

[0055] Oven-controlled crystal oscillator (OCXO): An oscillator that is placed in a constant temperature bath to keep its operating temperature constant, thereby obtaining an oscillator with extremely high frequency stability.

[0056] Temperature-compensated crystal oscillator (TCXO): An oscillator that uses a temperature compensation circuit to reduce the impact of temperature changes on the frequency of the crystal oscillator.

[0057] It should be noted that the specific parameters, models, and algorithm details (such as least squares can be replaced by robust regression) in the above embodiments can be varied and adjusted without departing from the core concept of this application. For example, the number and spacing of the linear array elements can be adjusted according to accuracy requirements and field conditions; the acoustic signal can also adopt other encoding forms. These variations and adjustments should all be included within the protection scope of this application.

[0058] Compared with the prior art, this application has the following significant advantages: 1. High positioning accuracy: By jointly inverting the local soil sound velocity and the depth of the internal detector, the systematic error caused by the uncertainty of sound velocity is eliminated, achieving sub-meter level positioning accuracy, which is far superior to traditional acoustic positioning methods (the error is usually tens of meters).

[0059] 2. High adaptability: It can adapt to various complex geological conditions and is not affected by factors such as soil type, moisture content, and compaction degree, making it widely applicable.

[0060] 3. High degree of automation: From automatic identification of blockages to final three-dimensional coordinate output, the entire process is automated, reducing human intervention and improving rescue efficiency.

[0061] 4. Cost-effectiveness: Compared with traditional electromagnetic marker box systems, this application does not require the deployment of a large number of marker boxes along the entire pipeline. Only ground receiving equipment needs to be temporarily deployed after a blockage occurs, which greatly reduces construction and maintenance costs.

[0062] 5. Excellent real-time performance: The ground processing terminal has built-in high-performance algorithms that can output inversion results in real time on site, providing support for rapid rescue decision-making.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation methods of this application. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this application should be covered within the protection scope of the claims of this application.

Claims

1. A method for locating a stuck detector in a pipe using array acoustic wave layered inversion, characterized in that, Includes the following steps: S1, before the internal detector runs, uses an external standard time source to synchronize and calibrate the local clock of the acoustic emission control unit on the internal detector to establish a global absolute time coordinate system. S2, the internal detector monitors its movement status in real time, and when it determines that it has entered a jammed state, it triggers the subsequent acoustic signal transmission process; S3, when it is determined that the pipe is stuck, the internal detector emits an acoustic signal to the pipe medium at a preset absolute time based on the calibrated local clock. S4. Arrange at least two receiving points along the estimated axial direction of the ground pipeline to collect sound wave signals. Estimate the comprehensive sound velocity of the pipe-soil medium as the sound wave propagates along the axial direction through signal processing. Combine the absolute flight time of the signal to calculate the approximate axial distance range of the blockage point. S5. Within the defined axial distance range, move the ground receiving probe along the axial and vertical directions of the pipeline, and determine the vertical projection center position of the blockage point on the ground based on the point with the maximum received signal amplitude. S6. Using the above-mentioned projection center position as a reference, arrange a linear receiving array perpendicular to the pipe direction, collect acoustic signals, and obtain the absolute travel time vector of the received signals of each array element. S7. Construct a radial propagation model of sound waves from the inner detector to the ground array element, linearize the nonlinear travel time equation, and use the absolute travel time vector and the spatial coordinates of the array element to simultaneously infer the local soil sound velocity above the blockage point and the burial depth of the inner detector through a parameter estimation algorithm. Combined with the determined planar coordinates, the three-dimensional spatial position of the inner detector is accurately determined.

2. The method for locating a blocked detector in a pipe using array acoustic wave layered inversion according to claim 1, characterized in that, The method of synchronizing and calibrating the local clock of the acoustic emission control unit mounted on the internal detector using an external standard time source includes the following steps: S11, obtains PPS second pulse signal through GPS receiver module; S12, the rising edge of the PPS second pulse signal is used to trigger the clearing and resetting of the internal counter of the acoustic emission control unit to achieve phase synchronization with Coordinated Universal Time (UTC). S13, a high-stability clock source is used as the oscillation source of the local clock, and the high-stability clock source includes a temperature-compensated crystal oscillator (OCXO) or a temperature-compensated crystal oscillator (TCXO). S14 records the time span from the synchronization completion time to the jamming time, and performs linear compensation correction on the absolute time T0 of the sound wave emission based on the nominal drift rate of the crystal oscillator.

3. The method for locating a blocked detector in a pipe using array acoustic wave layered inversion according to claim 1, characterized in that, The internal detector monitors its motion state in real time, including the following steps: S21, using the Kalman filter algorithm to fuse odometer data and inertial measurement unit (IMU) data, to estimate the motion state of the internal detector in real time; S22, if and only if the mileage wheel stops counting for a period of time exceeding a preset threshold and the axial acceleration remains below the static threshold, the internal detector is determined to be in a jammed state.

4. The method for locating a blocked detector in a pipe using array acoustic wave layered inversion according to claim 1, characterized in that, The internal detector emits an acoustic signal to the pipeline medium at a preset absolute time based on a calibrated local clock, including the following steps: S31, using a preset timing point as the launch start point T0; S32, emits an acoustic signal with high autocorrelation characteristics, wherein the signal is a single-frequency signal, a linear frequency modulated (LFM) signal, or a Barker code modulated pulse signal; S33, the frequency range of the acoustic signal is selected as a predetermined frequency band; S34, each transmission lasts for Tdur, with a pause interval of TER periodic signals, until the transmission continues until the jamming is released or the internal detector is removed.

5. The method for locating a blocked detector in a pipe using array acoustic wave layered inversion according to claim 1, characterized in that, The method of arranging at least two receiving points along the estimated axial direction of the ground pipeline to collect sound wave signals and estimating the combined sound velocity of the pipe-soil medium along the axial direction of the sound waves through signal processing includes the following steps: S41: Two known-distance... are arranged on the ground along the pipe axis. The probes serve as the first and second receiving points, and each probe is equipped with an independent GPS timing module to accurately timestamp the received signals using UTC. S42: Estimate the time delay between the two received signals based on a time delay estimation algorithm. ; S43, Calculate the estimated comprehensive sound velocity of the axially oriented pipe-soil medium: ; S44, Calculate the axial distance from the blockage point to the proximal probe: ,in The absolute moment when the sound wave arrives at the near-end probe. The launch time after drift compensation. This is due to system hardware response delay.

6. The method for locating a blocked detector in a pipe using array acoustic wave layered inversion according to claim 1, characterized in that, Step S5 includes the following steps: S51, within the axial distance range, move the ground receiving probe along the pipeline axis with a first preset step size, record the amplitude of the acoustic signal received at each point, and mark the point with the maximum amplitude as the axial center position. S52, at the axial center position, the ground receiving probe is moved perpendicular to the pipe axis with a second preset step size, the amplitude of the acoustic signal received at each point is recorded, and the point with the maximum amplitude is determined as the vertical projection center position of the blockage point on the ground.

7. The method for locating a blocked detector in a pipe using array acoustic wave layered inversion according to claim 1, characterized in that, The method of arranging a linear receiving array perpendicular to the pipe direction, based on the aforementioned projection center position, includes the following steps: S61, with the center of the vertical projection of the blockage point on the ground as the reference point, a linear receiving array is arranged in a direction perpendicular to the pipeline. S62, the linear receiving array consists of at least 3 vertical component detectors, and each detector is arranged in a straight line at a preset interval; S63 synchronously acquires the acoustic signals of each array element through a multi-channel data acquisition unit.

8. The method for locating a blocked detector in a pipe using array acoustic wave layered inversion according to claim 1, characterized in that, Step S7 includes the following steps: S71, a radial propagation forward model is constructed based on ray theory, and the travel time of the i-th array element satisfies the hyperbolic equation: ,in Let be the absolute observation time of the i-th array element. H is the horizontal distance of the i-th array element relative to the axial center, and H is the burial depth of the inner detector. This refers to the local soil sound velocity; S72, Squaring and rearranging both sides of the hyperbola equation, we obtain the linearized observation equation: ,in The gradient parameter is related to the square of the medium's slowness. The intercept parameter is related to the square of the equivalent depth; S73, construct the design matrix H and the observation vector Y, where H is derived from... The value is composed of Y. Value composition; S74, Solving for the parameter vector using least squares estimation. and : ， in, This is a special case of the Vandermonde matrix; S75, based on the inversion-obtained parameters α and β, solve the physical model: Local soil sound velocity estimation: ; Internal detector burial depth estimation: .

9. The method for locating a stuck detector in a pipe using array acoustic wave layered inversion according to any one of claims 1-8, characterized in that, It also includes step S8: The inversion results are output in real time through a portable edge computing terminal, which has a built-in floating-point unit (FPU) configured to perform Fast Fourier Transform (FFT), generalized cross-correlation operations, and nonlinear least squares regression algorithms.

10. A pipe detector jamming location system based on array acoustic wave layered inversion, characterized in that, include: The acoustic emission subsystem of the internal detector, integrated within the internal detector cabin, includes a main control unit, a high-precision clock module, a motion status monitoring module, a power amplifier module, and an acoustic transducer. The main control unit is used to perform jamming state determination and control the acoustic transducer to emit acoustic signals at a specific time after jamming. The high-precision clock module is synchronized with an external standard time source. The motion status monitoring module includes a mileage wheel module and an inertial measurement unit (IMU). The mileage wheel module is used to count the distance traveled by the internal detector, and the IMU measures the acceleration of the internal detector. The ground receiving and processing subsystem includes a GPS timing module, a multi-channel data acquisition unit, a linear sensor array, and a portable computing terminal. The GPS timing module provides a time reference synchronized with the transmitter. The linear sensor array is used to acquire surface acoustic signals. The portable computing terminal is used to receive data and execute the comprehensive sound velocity estimation of the axial soil-conduit medium, the ground center point calibration, and the joint inversion algorithm of radial stratification parameters, outputting the three-dimensional coordinates of the internal detector and the local soil sound velocity.

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