A real-time monitoring system for the posture correction and ultrasonic probe coupling state of a subsea pipeline internal detector

Abstract

The application discloses a real-time monitoring system for the posture deviation correction of a submarine pipeline internal detector and the coupling state of an ultrasonic probe, and belongs to the technical field of submarine pipeline nondestructive testing. The system comprises a detector body, circumferentially arranged ultrasonic probe units, an IMU posture sensing module, an electric-acoustic integrated acquisition board, a central edge calculation processing unit and a deviation correction execution mechanism. The acquisition board injects a sweep signal into the probe and extracts a complex impedance spectrum in an acoustic dead time slot, and inverts the acoustic impedance and thickness of the coupling medium. The processing unit fuses the acoustic impedance deviation, the posture deviation angle and the echo amplitude decoupling real defect signal, generates a feedforward amount according to the circumferential acoustic load distribution prediction posture deviation trend, and superimposes the feedforward amount and a feedback amount to drive the execution mechanism to correct the deviation. The application realizes non-acoustic quantization of the coupling state and feedforward active deviation correction, and reduces the missed detection rate and the false alarm rate.

Description

Technical Field

[0001] This invention relates to the field of non-destructive testing technology for subsea pipelines, specifically to a real-time monitoring system and method for the attitude correction of detectors and the coupling status of ultrasonic probes inside subsea pipelines. It belongs to the technical field of intersecting measurement technologies for actual or complex electrical parameters such as resistance, reactance, and impedance, piezoelectric material property measurement technology, ultrasonic non-destructive testing technology, and position feedback control technology. It can be applied to industries such as non-destructive testing of oil and gas storage and transportation, marine engineering equipment manufacturing, and intelligent instruments and sensor networks. Background Technology

[0002] Subsea pipelines are vital channels for transporting oil and gas from offshore oil and gas fields, often referred to as the lifeline of these fields. Pipeline detectors, equipped with ultrasonic probe arrays, autonomously travel along the inner wall of the pipeline, providing an effective means of detecting corrosion and cracks in the pipeline wall without interrupting production. However, ultrasonic testing relies on a coupling medium to effectively transmit sound waves to the pipe wall. Subsea pipelines operate in complex environments, including wax buildup, multiphase flow, and debris. Furthermore, after long-distance operation, the pipelines contain numerous bends, tees, and locally deformed sections.

[0003] As the core sensing element of ultrasonic probes, piezoelectric ceramics possess a bidirectional electromechanical coupling effect: on the one hand, they can convert electrical excitation signals into mechanical vibrations that radiate sound waves outwards; on the other hand, the change in acoustic impedance of the external mechanical load, i.e., the coupling medium, will react on the piezoelectric oscillator, changing the impedance characteristics of its electrical ports. This electromechanical coupling relationship has been demonstrated in piezoelectric physics through an equivalent circuit model. In addition, direct digital frequency synthesis technology, phase-locked demodulation technology, high-speed signal processing technology, and inertial attitude measurement technology have all been applied in the field of industrial inspection, providing a foundation for the realization of related hardware platforms.

[0004] The structure of the ultrasonic internal detector commonly used in the industry for subsea pipelines is as follows: the detector body is cylindrical, with cups or spring support wheels at both ends for passive centering. Several sets of ultrasonic probes are evenly arranged in the middle of the body. The probes are pressed against the inner side of the pipe wall by elastic support arms or floating brackets. The back of the probe is connected to an ultrasonic pulse transmission and reception circuit. The collected echo signals are converted from analog to digital and stored in an onboard storage module. After the detection is completed, the data is collected and analyzed offline. The detection process is usually as follows: the ultrasonic probe periodically emits pulse sound wave signals and couples them into the pipe wall. It receives the reflected echoes from the inner and outer surfaces of the pipe wall and the possible multiple reflected echoes. By calculating the time difference between the multiple echoes between transmission and reception and combining it with the known sound velocity, the pipe wall thickness and coupling layer thickness are estimated. The calculated thickness data is compared with a preset threshold to determine whether there is corrosion or crack defects. The detector relies on the passive elastic force of the cups or spring wheels to maintain the movement of the body near the center line of the pipeline and does not have the ability to actively adjust its attitude.

[0005] The aforementioned existing technologies have the following shortcomings: First, when wax blocks adhere to the probe surface or when passing through a gas-liquid mixed-phase section, coupling degradation leads to a sharp attenuation of the ultrasonic echo. Existing systems rely solely on the single acoustic dimension of multiple echo time difference for judgment, lacking independent measurement methods for the physical state of the coupling medium itself. This makes it impossible to distinguish whether the attenuation is caused by a real defect in the pipe or by the degradation of the coupling medium, leading to potential misjudgments in data analysis. Second, traditional detectors rely on the passive mechanical force of a cup or spring wheel to maintain their position in the center of the pipe. This passive support structure can only generate a reaction force for the displacement that has already occurred, which is a reactive response. At high speeds, high pressures, and when passing through welds or diameter changes, the detector is prone to severe vibrations and tilting, causing the probe's acoustic beam to fail to penetrate the pipe wall perpendicularly, resulting in echo loss. Third, most existing in-pipe detection equipment is an open-loop system, lacking a mechanism for fusing and processing three types of heterogeneous data: electrical characteristics, acoustic characteristics, and attitude characteristics. The various sensor information is isolated from each other, making it impossible to form a joint judgment and proactive decision-making capability for the overall motion and coupling state of the detector. Even if an attitude deviation is detected, it is impossible to drive the correction mechanism in advance. Summary of the Invention

[0006] The technical problem this invention aims to solve is that existing ultrasonic internal inspection systems for subsea pipelines cannot distinguish whether the attenuation of ultrasonic echo signals is caused by actual defects in the pipeline or by the deterioration of the coupling medium between the probe and the pipe wall or by detector attitude deviation, resulting in distorted detection data and high rates of missed detections and false alarms. At the same time, existing detector attitude adjustment mechanisms are passive or hysteresis feedback, which cannot intervene to correct deviations in advance before the detector experiences severe attitude shifts, easily causing the probe's acoustic beam to deviate from the pipe wall normal direction, further exacerbating coupling failure and reducing detection accuracy.

[0007] This invention is implemented as follows: a real-time monitoring system for the attitude correction and ultrasonic probe coupling status of a detector inside a subsea pipeline, comprising a detector body, multiple ultrasonic probe units arranged circumferentially within the detector body, an attitude sensing module disposed inside the detector body, and correction execution mechanisms distributed circumferentially along the detector body; the system further includes an electro-acoustic integrated acquisition board connected to the multiple ultrasonic probe units, comprising a direct digital frequency synthesis sweep excitation module, an ultrasonic pulse transmission and reception circuit, and a phase-locked demodulation unit. The direct digital frequency synthesis sweep excitation module and the ultrasonic pulse transmission and reception circuit share the same probe port via time-division multiplexing, used to inject [something] into the piezoelectric ceramic probe during the idle time window from after the ultrasonic probe completes one transmission pulse until a valid echo signal is received. The system receives a wideband sweep excitation signal and synchronously demodulates the probe response signal to obtain complex impedance spectrum data. The system also includes a central edge computing processing unit connected to the electro-acoustic integrated acquisition board and the attitude sensing module. This unit includes a coupling layer inversion algorithm module, an electro-acoustic-attitude decoupling algorithm module, and a feedforward adaptive correction control algorithm module. These modules are used to invert the acoustic impedance and thickness of the coupling medium based on the complex impedance spectrum data; to subtract the coupling attenuation component and attitude attenuation component in the ultrasonic echo amplitude based on the acoustic impedance deviation and attitude deflection angle to restore the true defect echo amplitude; and to predict the attitude offset trend based on the circumferential acoustic load distribution and generate control commands obtained by superimposing feedforward and feedback control quantities. The system also includes a drive circuit used to drive the correction actuator to adjust its radial extension length according to the control commands.

[0008] The present invention also provides a method for real-time monitoring of the attitude correction of a detector and the coupling status of an ultrasonic probe in a subsea pipeline, corresponding to the above system.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0010] By injecting a wideband sweep frequency micro-excitation signal into the piezoelectric probe within the acoustic dead time slot and extracting the complex impedance spectrum, and combining it with the equivalent circuit model to perform in-situ electrical inversion of the acoustic impedance and thickness of the coupling medium, independent quantitative measurement of the coupling state can be achieved without adding additional sensors. This enables the system to distinguish between coupling attenuation and the attenuation caused by actual defects, thereby reducing the false judgment rate. By constructing an attenuation compensation decoupling model for electro-acoustic-attitude three-source data, the acoustic impedance deviation of the coupling layer and the probe attitude angle are used as decoupling variables. The coupling attenuation component and attitude attenuation component are deducted from the original ultrasonic echo amplitude, improving the authenticity and reliability of the detection data. By using the circumferential acoustic load distribution data acquired in real time by the circumferentially arranged probe array to predict the detector attitude deviation trend in advance, an active correction control strategy with the superposition of feedforward and feedback quantities is constructed. This strategy can complete the attitude correction action before the detector experiences severe eccentricity or vibration, reducing echo loss caused by attitude deviation. Fourth, by correcting the feedforward gain coefficient online based on the comparison between the actual displacement of the actuator and the predicted offset, the correction system has the ability to continuously self-calibrate as the pipeline operating conditions change. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the overall system architecture of the present invention;

[0012] Figure 2 This is a block diagram of the hardware principle for probe electrical parameter extraction and coupling layer inversion.

[0013] Figure 3 This is a diagram of the equivalent circuit model of a piezoelectric probe.

[0014] Figure 4 Flowchart for decoupling multi-source electro-acoustic-attitude data;

[0015] Figure 5 A map showing the circumferential acoustic load distribution of the array probe;

[0016] Figure 6 This is a block diagram of the feedforward active correction control principle.

[0017] Figure 7 This is a cross-sectional view of the detector's mechanical structure.

[0018] Figure 8 This is a flowchart of the overall system workflow. Detailed Implementation

[0019] To further understand the invention's content, features, and effects, the following embodiments are provided, and detailed descriptions are given in conjunction with the accompanying drawings.

[0020] I. System Overall Architecture

[0021] The real-time monitoring system for attitude correction and ultrasonic probe coupling status of a detector inside a subsea pipeline provided in this embodiment includes a detector body. The detector body is arranged along the axis of the subsea pipeline, and multiple sets of ultrasonic probe units are evenly distributed around the body. Each set of ultrasonic probe units is connected to the same electro-acoustic integrated acquisition board. The acquisition board integrates a direct digital frequency synthesis wideband sweep excitation module, an ultrasonic pulse transmission and reception circuit, a high-speed analog-to-digital conversion acquisition channel, and a phase-locked demodulation unit. The aforementioned sweep excitation module and ultrasonic pulse transmission and reception circuit share the same probe port through time-division multiplexing. A separate attitude correction and ultrasonic probe coupling status monitoring system is also arranged inside the detector body. The attitude sensing module, implemented using an inertial measurement unit, outputs real-time information on the detector's pitch, yaw, and roll angles. Data from the acquisition board and attitude sensing module are fed into the central edge computing processing unit, which sequentially runs the coupling layer inversion algorithm module, the electro-acoustic-attitude decoupling algorithm module, and the feedforward adaptive correction control algorithm module. Control commands output by the processing unit are sent to multiple sets of correction actuators distributed along the circumference of the detector via drive circuits. The actuators are mechanically connected to the detector body via elastic linkages, forming a closed-loop link that connects probe electrical sensing, multi-source data decoupling, feedforward control decision-making, and actuator actions.

[0022] II. In-situ Inversion Module of Physical State of Coupled Layer Based on Wideband Electrical Parameters of Piezoelectric Oscillator

[0023] The electrical detection path of a single ultrasonic probe unit is as follows: the two electrodes of the piezoelectric ceramic probe are respectively connected to a bidirectional switching switch, which is controlled by a timing controller. During the transmit-receive time slot, the probe is connected to the ultrasonic pulse transmit-receive circuit, and during the acoustic dead time slot, the probe is switched to the direct digital frequency synthesis sweep frequency excitation circuit. The sweep frequency excitation module generates a wideband sweep frequency sinusoidal signal with a frequency in the megahertz range and an amplitude in the millivolt range. After passing through a power matching network, it is applied to the probe electrodes. The probe response current is converted into a voltage signal by a transimpedance amplifier and then sent to a lock-in amplifier for synchronous demodulation along with the excitation signal. The amplitude ratio and phase difference information corresponding to each sweep frequency point are obtained, and the complex impedance value at that sweep frequency point is calculated. The above process is repeated until all preset frequency points are scanned to obtain complete complex impedance spectrum data.

[0024] The piezoelectric probe under coupled load can be equivalent to the following circuit structure: The overall circuit presents a parallel connection of a static capacitance branch and a dynamic resonant branch. The static capacitance branch represents the inherent capacitance characteristics of the piezoelectric ceramic itself; the dynamic resonant branch is composed of three components connected in series: a dynamic resistor, a dynamic inductor, and a dynamic capacitor. The value of the dynamic resistor changes dynamically due to the acoustic impedance of the coupling medium, which is an external acoustic load on the probe end face. The dynamic inductance and dynamic capacitance are mainly determined by the mechanical properties of the piezoelectric material itself and remain basically constant. The total admittance of the probe's electrical port under swept frequency excitation can be expressed as:

[0025]

[0026] In the formula, Indicates the excitation frequency as Total admittance of the electrical port of the time probe; This represents the inherent static capacitance of piezoelectric ceramics; Indicates the acoustic impedance of the coupling medium with the external medium. The relevant dynamic resistances exhibit a monotonic mapping relationship, which is obtained through factory calibration. It represents dynamic inductance, reflecting the mechanical equivalent mass of the piezoelectric oscillator; This represents dynamic capacitance, reflecting the mechanical equivalent compliance of the piezoelectric oscillator. It is the imaginary unit.

[0027] Substituting the measured complex impedance spectrum data into the above equivalent circuit model, the dynamic resistance is solved using a fitting method. The estimated value is obtained, and based on the mapping relationship table between dynamic resistance and acoustic impedance obtained from factory calibration, the equivalent acoustic impedance value of the coupling medium at the current probe end face is obtained by inversion. The thickness of the coupling layer can be estimated based on the slope of the phase change of the complex impedance spectrum with the excitation frequency in the preset frequency band and combined with the acoustic velocity data of the coupling medium from factory calibration. The two have a corresponding relationship that the larger the phase change slope, the smaller the coupling layer thickness. The acoustic impedance value and thickness estimate of the coupling medium obtained by inversion in this cycle are synchronously output to the electro-acoustic-attitude decoupling algorithm module, and simultaneously updated to the historical coupling state cache queue of the probe channel for subsequent trend judgment.

[0028] III. Defect Signal Attenuation Dynamic Decoupling Module for Electro-Acoustic-Attitude Multidimensional Data Linkage

[0029] The probe complex impedance spectrum data, attitude data and ultrasonic echo amplitude data acquired within the same sampling period are aligned with a unified timestamp to eliminate the time sequence deviation caused by the different acquisition rates of the three types of sensor data. The output results of the coupling layer inversion algorithm module are called to calculate the current coupling layer acoustic impedance deviation, that is, the difference between the current inverted acoustic impedance value and the calibration baseline acoustic impedance value of the probe channel. Based on the relationship between the attitude angle data output by the attitude sensing module and the installation angle of the probe on the detector body, the actual angle between the probe beam direction and the tube wall normal is calculated through coordinate transformation.

[0030] The compensation relationship between the actual defect echo amplitude and the measured amplitude can be expressed as:

[0031]

[0032] In the formula, This represents the true defect echo amplitude after deducting coupling and attitude interference; This represents the original echo amplitude value obtained by the ultrasonic receiving circuit. This indicates the deviation of the current coupling layer acoustic impedance from the calibrated baseline acoustic impedance, which is provided in real time by the coupling layer inversion algorithm module; This represents the angle between the probe's acoustic beam direction and the tube wall normal, calculated from attitude data combined with the probe's installation angle. , These are the coupling attenuation compensation coefficient and the attitude attenuation compensation coefficient, respectively. They were obtained offline through support vector regression training in multi-condition calibration experiments at the factory, and can be slightly corrected online during operation using Kalman filtering.

[0033] The restored actual defect echo amplitude is compared with the preset defect judgment threshold, and the judgment result of corrosion defect or crack defect in the pipe wall area corresponding to the probe channel is output. The judgment result along with the location information is stored in the detection data recording module.

[0034] IV. Feedforward Active Adaptive Correction Architecture Based on Spatial Distribution Sensing of Array Acoustic Load

[0035] The central edge computing processing unit collects the coupling layer acoustic impedance inversion values ​​of all circumferential probe channels at fixed intervals to construct the circumferential acoustic load distribution data at the current moment. This distribution data can reflect whether there are obvious non-uniform regions of acoustic impedance in the circumferential direction. For example, a significantly higher acoustic impedance on one side may indicate that there may be scale accumulation or insufficient probe clamping force on that side. The gradient of the circumferential acoustic load distribution data is calculated along the circumferential angle, and the angle interval where the absolute value of the gradient exceeds a preset threshold is identified. This interval is marked as a potential force imbalance warning zone. The larger the gradient value, the more unbalanced the force on the detector in that circumferential direction, and the more obvious the trend of attitude deviation in the future. Combining the known elbow, diameter change and scale distribution information of this pipe section in the historical flow database of the pipeline, the attitude deviation trend of the warning zone in the next few sampling periods is predicted to obtain the predicted offset. The feedforward control quantity is calculated based on the acoustic impedance gradient value corresponding to the predicted offset.

[0036] The composite calculation relationship of control commands is as follows:

[0037]

[0038] In the formula, express Control commands are constantly output to the correction actuator; express The deviation between the actual attitude of the time detector and the target attitude; , , These are the proportional, integral, and derivative gain coefficients in the feedback control law; This represents the feedforward control quantity obtained from the prediction of the circumferential acoustic load distribution. The feedforward gain coefficient is obtained through experimental calibration.

[0039] After the actuator completes its action, its actual displacement is fed back to the control system via a position sensor and compared with the predicted offset. This is used to correct the feedforward gain coefficient online and achieve continuous adaptive optimization of the feedforward control model.

[0040] V. Detector Mechanical Structure Implementation

[0041] The detector body is a cylindrical shell with several mounting slots evenly spaced around its center. Each slot houses a set of floating ultrasonic probe brackets, which are pre-tensioned against the tube wall by springs. The ultrasonic probe unit is mounted on the floating probe bracket. A correction mechanism is located beside each set of floating probe brackets. This correction mechanism includes a support arm, one end of which is hinged to the detector body frame, and the other end contacts the inner surface of the tube wall. A drive mechanism is located inside the support arm, allowing adjustment of its radial extension length under control commands. In one embodiment, the drive mechanism is an electromagnetic damping follower wheel drive mechanism driven by an electromagnet; in another embodiment, the drive mechanism is a hydraulic fine-tuning support arm drive mechanism driven by a miniature solenoid valve. An electro-acoustic integrated acquisition board, an attitude sensing module, and a central edge computing processing unit are installed in the sealed chamber inside the detector body.

[0042] VI. Overall System Workflow

[0043] As the detector travels along the pipeline, it enters the acoustic dead zone time slot to trigger complex impedance spectrum acquisition and coupling layer inversion. Subsequently, it enters the electro-acoustic-attitude multi-source data decoupling to obtain the real defect echo amplitude and output the defect judgment result. At the same time, it executes circumferential acoustic load distribution construction, attitude trend prediction and feedforward correction control command generation and execution in parallel. The two processing branches are coupled to each other and executed cyclically until the detector completes the entire pipeline inspection task.

[0044] VII. Other Alternative Implementation Methods

[0045] In the coupling layer inversion stage, instead of using a lock-in amplifier for synchronous demodulation, a high-speed analog-to-digital converter can be used to sample the full waveform of the probe response signal. The sampled data is then analyzed in the frequency domain by the fast Fourier transform module embedded in the field-programmable gate array, and the amplitude and phase information of each swept frequency point can be directly extracted. Complex impedance spectrum data can also be obtained. This scheme can eliminate the need for a separate lock-in amplifier hardware module and is suitable for application scenarios with high requirements for system size and cost.

[0046] Regarding the feedforward correction actuator, instead of using an electromagnetic damping follower wheel or a hydraulic fine-tuning support arm, a micro-displacement actuator based on piezoelectric ceramic stacks or shape memory alloys can be used. The fast response speed and compact structure of the actuator can be used to adjust the radial extension of the support arm. The control algorithm can still use the aforementioned feedforward and feedback composite control strategy. Only the driving mode of the actuator changes, and the same active correction effect can be achieved.

Claims

1. A real-time monitoring system for the attitude correction of a detector and the coupling status of an ultrasonic probe inside a subsea pipeline, comprising a detector body arranged along the axis of the subsea pipeline; Multiple ultrasonic probe units are evenly distributed circumferentially on the detector body; An attitude perception module, located inside the detector body, is used to acquire pitch angle, yaw angle and roll angle information of the detector body; A correction actuator is distributed circumferentially along the detector body and is used to adjust the radial support state of the detector body in the pipeline; characterized in that it further includes: an electro-acoustic integrated acquisition board connected to the multiple ultrasonic probe units, including a direct digital frequency synthesis sweep excitation module, an ultrasonic pulse transmission and reception circuit and a phase-locked demodulation operation unit, wherein the direct digital frequency synthesis sweep excitation module and the ultrasonic pulse transmission and reception circuit share the same probe port through time-division multiplexing; The direct digital frequency synthesis sweep excitation module is used to inject a wideband sweep excitation signal into the piezoelectric ceramic probe during the idle time window from when the ultrasonic probe completes one transmission pulse until it receives a valid echo signal. The phase-locked demodulation unit is used to synchronously demodulate the probe response signal to obtain complex impedance spectrum data; The central edge computing processing unit is connected to the electro-acoustic integrated acquisition board and the attitude perception module, and includes a coupling layer inversion algorithm module, an electro-acoustic-attitude decoupling algorithm module and a feedforward adaptive correction control algorithm module. The coupling layer inversion algorithm module is used to invert the acoustic impedance value and coupling layer thickness value of the coupling medium at the probe end face based on the complex impedance spectrum data. The electro-acoustic-attitude decoupling algorithm module is used to calculate the defect echo amplitude after deducting the coupling attenuation component and the attitude attenuation component based on the acoustic impedance value, the attitude data output by the attitude sensing module, and the ultrasonic echo amplitude. The feedforward adaptive correction control algorithm module is used to predict the attitude offset trend of the detector body based on the circumferential acoustic load distribution data composed of the acoustic impedance values ​​of multiple ultrasonic probe units arranged in a ring, generate a feedforward control quantity, and add the feedforward control quantity to the feedback control quantity obtained based on the real-time attitude deviation output by the attitude perception module to obtain a control command for driving the correction actuator. A drive circuit, connected to the central edge computing processing unit and the correction actuator, is used to drive the correction actuator to adjust the radial extension length according to the control command.

2. The system according to claim 1, characterized in that, The coupling layer inversion algorithm module is configured to: substitute the complex impedance spectrum data into the equivalent circuit model of the piezoelectric probe for fitting, and solve for the estimated value of the dynamic resistance. The equivalent circuit model includes a static capacitor branch and a dynamic resonant branch. The static capacitor branch and the dynamic resonant branch are connected in parallel. The dynamic resonant branch is composed of a dynamic resistor, a dynamic inductor, and a dynamic capacitor connected in series. The value of the dynamic resistance is affected by the acoustic impedance of the external coupling medium of the probe end face. Based on the mapping relationship between the dynamic resistance and the acoustic impedance obtained from the factory calibration, the acoustic impedance value is inverted. Based on the slope of the phase change of the complex impedance spectrum with frequency in the preset frequency band, combined with the sound velocity data of the coupling medium, the thickness value of the coupling layer is calculated.

3. The system according to claim 1, characterized in that, The electro-acoustic-attitude decoupling algorithm module is configured to: obtain the deviation of the acoustic impedance value relative to the calibrated baseline acoustic impedance value; calculate the angle between the acoustic beam direction of the ultrasonic probe unit and the normal of the tube wall based on the attitude data and the installation angle of the corresponding ultrasonic probe unit on the detector body; and, based on the deviation and the angle, subtract the coupling attenuation component and the attitude attenuation component from the original ultrasonic echo amplitude according to the pre-calibrated coupling attenuation compensation coefficient and attitude attenuation compensation coefficient to obtain the defect echo amplitude.

4. The system according to claim 1, characterized in that, The feedforward adaptive correction control algorithm module is configured to: collect the acoustic impedance values ​​of all ultrasonic probe units arranged in a circumferential manner at fixed intervals, construct the circumferential acoustic load distribution data, calculate the gradient value of the circumferential acoustic load distribution data along the circumferential angle of the detector, mark the angle interval where the absolute value of the gradient exceeds a preset threshold as the stress imbalance warning interval, combine the known elbow, diameter change and scaling distribution information in the pipeline historical flow data, predict the attitude offset trend of the stress imbalance warning interval in the next few sampling periods, obtain the predicted offset, and calculate the feedforward control quantity based on the gradient value corresponding to the predicted offset.

5. The system according to claim 4, characterized in that, The feedforward adaptive correction control algorithm module is also used to obtain the actual displacement amount fed back by the position sensor after the correction actuator moves, compare the actual displacement amount with the predicted offset amount, and correct the feedforward gain coefficient used to calculate the feedforward control amount based on the comparison result.

6. The system according to claim 1, characterized in that, The detector body is a cylindrical shell with multiple mounting slots circumferentially formed in the middle of the shell. A set of probe floating brackets is installed in each mounting slot. The probe floating brackets are pre-tightened against the pipe wall by springs. The ultrasonic probe unit is disposed on the probe floating bracket. The correction actuator includes a support arm. One end of the support arm is hinged to the detector body, and the other end contacts the inner surface of the pipe. A drive mechanism is provided inside the support arm to adjust the radial extension length of the support arm under the action of the control command.

7. A method for real-time monitoring of the coupling status between the attitude correction of a detector and an ultrasonic probe inside a subsea pipeline, characterized in that, include: During the idle time window between the completion of one transmission pulse by the ultrasonic probe and the receipt of a valid echo signal, a broadband sweep excitation signal is injected into the ultrasonic probe. The response signal of the ultrasonic probe is acquired and synchronously demodulated to obtain complex impedance spectrum data. Based on the complex impedance spectrum data, the acoustic impedance value and coupling layer thickness of the coupling medium at the probe end face are obtained. The attitude data and ultrasonic echo amplitude of the detector body are acquired. Based on the acoustic impedance value, the attitude data, and the ultrasonic echo amplitude, the defect echo amplitude after deducting the coupling attenuation component and the attitude attenuation component is calculated. The defect judgment result is output based on the defect echo amplitude. The acoustic impedance values ​​corresponding to multiple sets of ultrasonic probe units arranged in a ring are acquired. The circumferential acoustic load distribution data is constructed. Based on the circumferential acoustic load distribution data, the attitude offset trend of the detector body is predicted to obtain the feedforward control quantity. Based on the real-time attitude deviation of the detector body, the feedback control quantity is obtained. The feedforward control quantity and the feedback control quantity are added to obtain the control command. Based on the control command, the correction actuator is driven to adjust the radial extension length to adjust the attitude of the detector body.

8. The method according to claim 7, characterized in that, The acoustic impedance value and coupling layer thickness value of the probe end face coupling medium are obtained by inverting the complex impedance spectrum data, including: substituting the complex impedance spectrum data into the equivalent circuit model of the piezoelectric probe for fitting, solving for the estimated value of dynamic resistance, inverting the acoustic impedance value according to the mapping relationship between dynamic resistance and acoustic impedance obtained by factory calibration, and calculating the coupling layer thickness value according to the slope of the phase change of the complex impedance spectrum with frequency in a preset frequency band, combined with the sound velocity data of the coupling medium.

9. The method according to claim 7, characterized in that, The calculation of the defect echo amplitude after deducting the coupling attenuation component and the attitude attenuation component includes: obtaining the deviation of the acoustic impedance value from the calibrated baseline acoustic impedance value; calculating the angle between the sound beam direction of the ultrasonic probe unit and the normal of the pipe wall based on the attitude data and the installation angle of the corresponding ultrasonic probe unit; and deducting the coupling attenuation component and the attitude attenuation component from the original ultrasonic echo amplitude based on the deviation and the angle, according to the pre-calibrated coupling attenuation compensation coefficient and attitude attenuation compensation coefficient.

10. The method according to claim 7, characterized in that, Also includes: The actual displacement after the correction actuator is activated is obtained, and the actual displacement is compared with the predicted offset. Based on the comparison result, the feedforward gain coefficient used to calculate the feedforward control quantity is corrected.

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