Submarine pipeline offset positioning method and adaptive sound source frequency adjustment module

Abstract

The present invention relates to ocean detection and positioning technology, in particular to a method for locating submarine pipeline offsets and an adaptive sound source frequency adjustment module. The method comprises the following steps: S1, installing a combined intelligent pig group at the entrance of a submarine pipeline, wherein the sound source transmitting device on the combined intelligent pig group adaptively adjusts the frequency of the sound wave signal generated by the combined intelligent pig group according to the different media in the submarine pipeline through an adaptive sound wave frequency selection method; S2, an AUV moves following the combined intelligent pig group, receiving the signal emitted by the combined intelligent pig group in real time, and determining the signal propagation distance #imgabs0# between the AUV and the combined intelligent pig group through a weighted fusion algorithm; S3, updating the AUV's own position estimate #imgabs1# through a Kalman filter algorithm, thereby determining the position of the submarine pipeline where the combined intelligent pig is located. This method achieves real-time positioning of the submarine offset track to meet the requirements for high-precision, low-error real-time positioning in a complex submarine environment.

Description

Technical Field

[0001] The present invention relates to ocean detection and positioning technology, in particular to a submarine pipeline offset positioning method and an adaptive sound source frequency adjustment module. Background Art

[0002] Submarine pipelines, which continuously transport large quantities of oil and gas through sealed channels on the seabed, are a key component of offshore oil and gas field development and production systems and the fastest, safest, most economical, and reliable method of offshore oil and gas transportation. Due to the complex ocean geography and hydrodynamics, submarine pipelines can shift to varying degrees. Locating shifted pipelines is crucial to ensure proper transportation and regular inspection.

[0003] To locate submarine pipelines, two commonly used methods are external detection and internal detection. External detection typically utilizes acoustic detection, using acoustic wave detection technology, side-scan sonar, shallow subsurface profiling, and synthetic aperture sonar to locate the pipeline. However, external detection is significantly affected by the topography of the ocean environment, making it particularly effective for pipelines buried on the seabed. Internal detection primarily utilizes intelligent pigs equipped with signal transmitters, which emit low-frequency electromagnetic waves or ultrasonic waves for pipeline detection.

[0004] Magnetic flux leakage (MFL) technology is a relatively mature detection method in China. It receives signals through submarine pipe beacons and then feeds the signals back to communication buoys. However, this method has great limitations: (1) Since electromagnetic signals are easily affected by the seawater environment and pipe wall thickness, the signal attenuates quickly, the detection distance is short, and the application scenario requirements are high; (2) This technology requires coupling agents during operation, the positioning efficiency is not high, and the real-time performance is poor. The emergency real-time processing capability in the face of emergencies is not strong. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and propose a submarine pipeline offset positioning method and an adaptive sound source frequency adjustment module, which can adaptively select the frequency of the sound wave signal of the sound source transmitting device according to the medium, and realize the real-time positioning of the AUV through multi-source information fusion and joint optimization of time delay and intensity, thereby realizing real-time positioning of the submarine offset track to meet the real-time positioning requirements of high precision and low error in complex submarine environments.

[0006] The technical solution of the present invention is: a method for locating the offset of a submarine pipeline, which includes the following steps:

[0007] S1. Installing a combined intelligent pig assembly at the inlet of a submarine pipeline. The sound source emission device on the combined intelligent pig assembly adaptively adjusts the sound wave emission frequency according to different media in the submarine pipeline using an adaptive sound wave frequency selection method.

[0008] S2, the AUV follows the combined intelligent pig group and receives the signal from the combined intelligent pig group in real time. The signal propagation distance between the AUV and the combined intelligent pig group is determined by the weighted fusion algorithm. ;

[0009] S3, update the AUV's own position estimate through the Kalman filter algorithm , thereby determining the location of the submarine pipeline where the combined intelligent pig is located.

[0010] In the present invention, the specific implementation process of the frequency optimization algorithm in step S1 is as follows:

[0011] S1.1, Collection and real-time feedback of environmental data;

[0012] S1.2. Based on the monitored environmental data, use the frequency optimization algorithm to select the optimal frequency and adjust the sound wave emission frequency of the sound source emission device;

[0013] S1.3. Use an iterative method to dynamically find the optimal frequency in real time.

[0014] In step S1.2, determine the optimal sound wave emission frequency range f opt ∈[300Hz,7kHz];

[0015] The propagation speed of sound waves in the pipeline medium V signal The calculation formula is:

[0016] ,

[0017] in, Indicates the medium temperature value collected in real time; Indicates the medium pressure value collected in real time; Indicates the medium correction item, its value is:

[0018] ,

[0019] The attenuation formula of sound wave intensity with distance d is:

[0020] ,

[0021] in, d Indicates the distance between the actual measurement point and the sound source, in meters; Indicates the initial signal strength, that is, the signal strength at the sound source, in dB; represents the reference distance, which is the reference standard for normalization; n(f) represents the attenuation factor, and its formula is:

[0022] n(f)=af+b ,

[0023] When the medium is oil, a=0.02, b=1.1; when the medium is natural gas, a=0.05, b=1.6;

[0024] α(f) represents the absorption coefficient of the medium to the sound wave signal, the unit is db / m, and its calculation formula is:

[0025] ;

[0026] Define the comprehensive performance index J(f) to maximize the signal-to-noise ratio And minimize the falloff:

[0027] ,

[0028] Among them, d max Indicates the maximum detection distance of the pipeline; λ indicates the weight coefficient, which is 0.5;

[0029] The calculation formula of signal-to-noise ratio SNR(f) is:

[0030] ,

[0031] in, Indicates the ambient noise power in dB.

[0032] The optimal frequency is solved in real time by the gradient ascent method:

[0033] ,

[0034] The optimal frequency is solved dynamically in real time using an iterative method.

[0035] ,

[0036] in, Represents the frequency update value after the k+1th iteration; Indicates the frequency value at the current k-th iteration; To indicate the frequency adjustment step; Indicates comprehensive performance indicators In frequency The gradient at

[0037] Set the stop condition to:

[0038] ;

[0039] in, Indicates the frequency corresponding to the kth iteration When , the comprehensive performance index is calculated; Indicates the frequency after the next iteration The corresponding performance indicator value.

[0040] The acoustic signal emitted by the combined intelligent pig group generates echo signals due to the multipath effect during the propagation process. , calculate the distance between the AUV and the combined intelligent pig group based on the propagation time delay estimation :

[0041] ,

[0042] Reversely infer the propagation distance based on the received signal strength The formula is:

[0043] ,

[0044] in, Indicates the correction factor of flow velocity on signal attenuation; V flow Indicates the current medium flow rate in m / s;

[0045] Define the time delay weight factor as :

[0046] ,

[0047] Define the signal strength weight factor as :

[0048] ,

[0049] The final signal propagation distance is calculated using the weighted fusion method :

[0050] ,

[0051] Among them, I max Indicates the maximum signal strength received in the environment.

[0052] In step S3, when determining the position of the combined intelligent pig and the submarine pipeline where it is located, the position of the AUV itself is estimated. As a benchmark, the d obtained in step S2 total With direction vector , calculate the position of the pig in the three-dimensional space on the seabed (xp ,y p ,z p ):

[0053] .

[0054] In step S3, the AUV's own position estimate is updated using the Kalman filter algorithm. The specific process is as follows:

[0055] Get the current state vector of the AUV based on the sensors on the AUV , where x, y, z represent the position coordinates of the AUV in three-dimensional space. represents the velocity component;

[0056] The state prediction and covariance update formula is:

[0057] ,

[0058] ,

[0059] in, Indicates the status of the prediction; represents the control input; represents the predicted covariance matrix; A represents the system state transfer matrix; B represents the control input matrix; u k Indicates the control input; P k represents the state estimation covariance matrix; Q represents the process noise covariance matrix;

[0060] According to the motion state of the AUV and the environmental changes of the AUV, the process noise matrix Q is dynamically adjusted:

[0061] .

[0062] in, Indicates the adjustment coefficient; V fIow Indicates the current medium flow rate; V max represents the preset maximum flow rate value; Q0 represents the static reference process noise covariance matrix;

[0063] Kalman gain K k+1 The calculation formula is:

[0064] ,

[0065] The updated state estimate is calculated as:

[0066] ,

[0067] Among them, Z K+1represents the measurement value, which is provided by the USBL system, depth meter, and acoustic reflection positioning system; H represents the observation matrix, and R represents the observation noise covariance matrix;

[0068] By extracting the first three components in the updated state vector, we can obtain the current real-time 3D position estimate of the AUV:

[0069] ;

[0070] in, is the first element of the updated state vector, representing the x-coordinate of the AUV at the current moment; The second element of the updated state vector represents the y coordinate of the AUV at the current moment; The third element of the updated state vector represents the z coordinate of the AUV at the current moment.

[0071] The present application also discloses an adaptive sound source frequency adjustment module, comprising:

[0072] The control module is used to configure the phase register of the DDS signal generation module according to the frequency of the sound source; it communicates with other modules to perform signal control and real-time feedback;

[0073] The DDS signal generation module adjusts the frequency to meet the transmission frequency requirements of different submarine pipeline media, generating adjustable frequency signals between 300 Hz and 7 kHz. The DDS frequency register is set via the SPI interface to generate the target frequency. The phase accumulator is used to control the frequency of the output signal. The frequency is accurately controlled by updating the phase register. A low-frequency signal is selected as the reference signal, and the frequency modulation function of the DDS is used to generate other frequencies.

[0074] The signal filtering and amplification module is used to filter and adjust the gain of the signal generated by the DDS signal generation module, remove high-order harmonics and enhance the signal amplitude; remove unnecessary high-frequency harmonics; and amplify the signal to the required amplitude;

[0075] A power amplifier module is used to increase the signal power so that it can drive the acoustic transducer;

[0076] The output module is used to drive the emission of the acoustic wave signal, and uses an acoustic transducer to convert the electrical signal into an acoustic wave;

[0077] Environmental adaptability module; used to ensure reliability for subsea use.

[0078] The beneficial effects of the present invention are:

[0079] (1) The combined intelligent pig group carries a sound source transmitter and adaptively adjusts the sound source frequency of the sound source transmitter according to the medium in different submarine pipelines, so that the sound source frequency can be adaptively adjusted according to different flow media in the pipeline without switching the sound source, saving costs and having strong adaptability;

[0080] (2) By dynamically adjusting the sound wave frequency in a complex submarine environment, the positioning error problem caused by improper frequency setting in traditional methods is solved, ensuring the effectiveness and accuracy of signal propagation. This not only effectively improves positioning accuracy, but also significantly enhances the adaptability and real-time performance of submarine pipeline positioning.

[0081] (3) The present invention combines the echo delay and signal strength information to calculate the precise position through a weighted fusion algorithm: during the echo signal transmission process, the delay information and strength information are combined to assign different weights to signals of different paths, thereby eliminating the errors caused by multipath propagation and ensuring positioning accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 It is a structural diagram of a positioning system for realizing a submarine pipeline offset positioning method;

[0083] Figure 2 This is a flowchart of the first step of this application for adaptively adjusting the sound wave emission frequency using the adaptive sound source frequency adjustment module.

[0084] In the figure: 1 submarine pipeline; 2 combined intelligent pig group; 3 sound source launch device; 4 AUV; 5 surface work vessel; 6 sea surface communication buoy; 7 satellite. DETAILED DESCRIPTION

[0085] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0086] The following description sets forth specific details to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in a variety of other ways than those described herein, and those skilled in the art will be able to make similar generalizations without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0087] The submarine pipeline offset positioning method described in the present application specifically includes the following steps.

[0088] The first step is preparation. Before locating the offset of the submarine pipeline, the combined intelligent pig group is installed.

[0089] The frequency of the acoustic emission is adjusted according to the medium in the pipeline. A modular intelligent pig assembly 2 is placed at the entrance of the submarine pipeline 1. The modular intelligent pig assembly 2 comprises several pigs, including a rigid foam pig at the front end, which performs preliminary pipeline cleaning to prevent blockages. The rear pig is equipped with a sound source transmitter 3, which emits a uniform and continuous medium-frequency acoustic signal within the pipeline. The flow velocity of the medium in the submarine pipeline is measured, and the flow velocity of the pig in the pipeline is inferred.

[0090] The medium in submarine pipeline 1 is either oil or natural gas. An appropriate acoustic frequency is selected based on the medium in the pipeline. The combined intelligent pig assembly 2 propels itself through the pipeline, driven by the flow of the medium or pressure differential. A sound source transmitter 3 is mounted on top of the pig. As the combined intelligent pig assembly 2 moves, it continuously emits intermediate-frequency acoustic signals into the pipeline 1. The echo signals from the pipeline are used to record information about the pipeline. This information includes its location, intentional leaks, blockages, and material properties.

[0091] The present application can adaptively adjust the sound source frequency of the sound wave signal generated by the sound source emitting device 3 according to different media in the submarine pipeline, so that the sound wave frequency adapts to the medium in the submarine pipeline.

[0092] This application proposes an adaptive sound source frequency adjustment module, which is used to find the mid-range sound wave frequency suitable for the oil / gas medium in the pipeline. The module includes a control module, a DDS (direct digital synthesis) signal generation module, a signal filtering and amplification module, a power amplification module, an output module, and an environmental adaptability module.

[0093] The control module is used to configure the phase register of the DDS signal generation module according to the frequency of the sound source, and can also communicate with other modules to perform signal control and real-time feedback. The control module in this embodiment can adopt an STM32 microcontroller.

[0094] The DDS signal generation module adjusts the frequency to meet the transmission frequency requirements of different submarine pipeline media, generating adjustable frequency signals between 300 Hz and 7 kHz. The DDS frequency register is set via the SPI interface to generate the target frequency. The phase accumulator controls the output signal frequency, and accurate frequency control is achieved by updating the phase register. A low-frequency signal is selected as the reference signal, and the DDS frequency modulation function is used to generate other frequencies.

[0095] The signal filtering and amplification module filters and adjusts the gain of the signal generated by the DDS signal generation module, removing high-order harmonics and enhancing the signal amplitude to ensure signal quality suitable for driving the power amplifier and acoustic transducer. A low-pass filter removes unnecessary high-frequency harmonics, ensuring a smooth output signal and avoiding interference. An operational amplifier amplifies the signal to the required amplitude, ensuring the signal strength is sufficient to drive the downstream power amplifier.

[0096] The power amplifier module is used to increase the signal power so that it can drive the acoustic transducer. The power amplifier module in this embodiment can be a Class D amplifier. The high efficiency of Class D amplifiers makes them suitable for applications that require high power but low heat dissipation. The Class D amplifier is used to amplify the signal and convert it into power suitable for driving the acoustic transducer.

[0097] The output module drives the transmission of acoustic signals. In this embodiment, the output module uses an acoustic transducer. The acoustic transducer converts electrical signals into acoustic waves. The acoustic transducer used in this application uses a medium-frequency acoustic wave frequency of 300 Hz to 7 kHz, which is resistant to the pressure and corrosion of the submarine environment.

[0098] The environmental adaptability module is used to ensure reliability for submarine use, such as waterproofing and corrosion resistance, and to ensure that the system has protection functions such as overheating and overcurrent to ensure safe and stable operation.

[0099] This application also proposes an adaptive sound wave frequency selection method, through which the optimal frequency range can be provided for each medium such as natural gas, oil, etc., to ensure that the signal propagation loss is minimized.

[0100] In practical applications, environmental factors such as seawater temperature, flow rate, and pressure have a direct impact on the propagation speed and attenuation of sound waves. Therefore, traditional frequency selection methods often fail to meet the needs of dynamically changing environments. This application dynamically adjusts the frequency settings on the intelligent pipe cleaner based on real-time collected environmental data such as seawater temperature and flow rate, and can also dynamically adjust the frequency according to changes in the actual environment.

[0101] The adaptive sound source frequency adjustment module can accurately select the optimal frequency between 300Hz and 7kHz based on real-time environmental changes. Specifically, the adaptive sound source frequency adjustment module on the modular intelligent pig group selects the most appropriate sound wave frequency in real time based on collected environmental data and a preset frequency optimization range. The frequency range is adjusted to adapt to environmental changes: in warmer waters, the frequency may be higher to accommodate faster sound wave propagation; in colder waters or environments with higher flow rates, the frequency is lowered to reduce attenuation and maintain good signal strength.

[0102] The above-mentioned adaptive sound wave frequency selection method includes the following specific steps: Figure 2 shown.

[0103] First, environmental data collection and real-time feedback: intelligent sensors are used to monitor seawater temperature, flow rate and other environmental parameters in real time, and the data is fed back to the control module.

[0104] Then, frequency optimization algorithm: The control module uses the frequency optimization algorithm to select the optimal frequency according to the monitored environmental data and adjust the output frequency of the DDS signal generation module.

[0105] In complex seabed environments, based on real-time collected medium temperature values , Real-time collected medium pressure value , medium type, and pipeline geometric parameters, dynamically select the optimal sound wave emission frequency range f opt ∈[300Hz,7kHz] to minimize signal attenuation and maximize the signal-to-noise ratio (SNR). Within the above acoustic wave transmission frequency range, in warmer water baths, the acoustic wave transmission frequency may be higher to accommodate faster sound wave propagation; in colder water baths or environments with higher flow rates, the acoustic wave transmission frequency is automatically lowered to reduce attenuation and maintain good signal strength.

[0106] Based on the optimization of UNESCO sound velocity formula, the medium correction term is introduced, and the propagation speed of sound waves in the pipeline medium V signal The calculation formula is:

[0107] ,

[0108] in, Indicates the medium correction item, its value is:

[0109] ,

[0110] The attenuation formula of sound wave intensity with distance d is:

[0111] .

[0112] in, d Indicates the distance between the actual measurement point and the sound source, in meters; Indicates the initial signal strength, that is, the signal strength at the sound source, in dB; represents the reference distance, which is used as a reference standard for normalization and is usually selected as 1 meter; n(f) represents the attenuation factor, which is related to the acoustic wave emission frequency f emitted by the pig and the absorption characteristics of the medium. Its formula is:

[0113] n(f)=af+b ,

[0114] When the medium is petroleum, a=0.02, b=1.1; when the medium is natural gas, a=0.05, b=1.6.

[0115] α(f) represents the absorption coefficient of the medium to the sound wave signal, the unit is db / m, and its calculation formula is:

[0116] 。

[0117] Define the comprehensive performance index J(f) to maximize the signal-to-noise ratio And minimize the falloff:

[0118] ,

[0119] Among them, d max represents the maximum detection distance of the pipeline, and its value is 100m; λ represents the weight coefficient, and its value is 0.5 through simulation calibration.

[0120] The calculation formula for the signal-to-noise ratio SNR(f) is:

[0121] ;

[0122] in, Indicates the ambient noise power in dB.

[0123] The optimal frequency is solved in real time by the gradient ascent method: ,

[0124] Because environmental factors such as temperature, pressure, flow rate, and medium vary over time and location, it's difficult to determine the optimal frequency through a single calculation. By using an iterative approach, we can dynamically find the frequency that optimizes the overall performance indicator J(f). Therefore, this application uses an iterative approach to dynamically find the optimal acoustic emission frequency in real time, improving the effectiveness and accuracy of signal propagation.

[0125] ,

[0126] in, Represents the frequency update value after the k+1th iteration; Indicates the frequency value at the current k-th iteration; To represent the frequency adjustment step size, in this embodiment, the value is set to 10 Hz, which is used to control the frequency adjustment amplitude of each step update; Indicates comprehensive performance indicators In frequency The gradient at , which expresses the trend of performance index changing with frequency.

[0127] When the performance index improvement caused by the frequency change is not obvious, stop the iteration and set the stopping condition as:

[0128] ;

[0129] in, Indicates the convergence threshold, with a value of 0.1; Indicates the frequency corresponding to the kth iteration When , the comprehensive performance index is calculated; Indicates the frequency after the next iteration The corresponding performance indicator value.

[0130] When the above conditions are met, it indicates that the optimal sound wave emission frequency is approaching.

[0131] Based on feedback from environmental changes, the combined intelligent pipe cleaning device group automatically adjusts the sound wave emission frequency according to the above method to ensure the best signal propagation effect during each positioning, avoiding the accuracy problems caused by the selection of a fixed sound wave emission frequency.

[0132] In the second step, the AUV4 follows the combined intelligent pig group 2 and receives the signal sent by the combined intelligent pig group 2 in real time.

[0133] At the same time, AUV4 transmits the pipeline's location information to surface vessel 5 via an ultra-short baseline. Surface vessel 5 and AUV4 utilize an ultra-short baseline positioning system for two-way communication. This system excels at locating mobile targets and offers rapid and flexible deployment. Staff on the surface vessel can monitor the status of the collaborative operation between the pig and AUV in real time.

[0134] The ultra-short baseline positioning system transmits acoustic signals from a surface work vessel and receives response signals from the AUV to calculate the target's position. The ultra-short baseline positioning system includes acoustic transponders installed on the bottom of the surface work vessel and the underwater target device AUV.

[0135] In the process of calculating the precise distance and orientation between the combined intelligent pig group and the AUV, the present application assumes that the acoustic wave signal emitted by the combined intelligent pig group will generate an echo signal due to the multipath effect during the propagation process. After the AUV receives the echo signal, the distance between the AUV and the combined intelligent pig group is calculated by measuring the time delay and signal strength of the echo signal.

[0136] Assume the time delay of the echo signal is , according to the time delay of the echo signal , calculate the distance d between the AUV and the combined intelligent pig group t .

[0137] ,

[0138] in, It represents the distance value estimated based on the propagation time delay, in meters; Δt is the propagation time delay of the acoustic wave signal from the pig to the AUV.

[0139] In order to further improve the accuracy, a joint time delay and signal strength optimization strategy is adopted. The propagation distance is inferred based on the received signal strength. The formula is:

[0140] ;

[0141] in, It represents the correction coefficient of flow velocity on signal attenuation, reflecting the influence of flow velocity on signal propagation; V flow Indicates the current medium flow rate in m / s.

[0142] In order to overcome the instability of a single estimation method in a multipath or signal attenuation strong environment, the present invention adopts a weighted fusion method to calculate the final propagation distance .

[0143] First, define the time delay weight factor and signal strength ,

[0144] ,

[0145] ,

[0146] ,

[0147] in, The weight factor of the time delay. The shorter the delay time, the higher the weight. The weight factor representing the signal strength. The stronger the signal, the higher the credibility. max Indicates the maximum signal strength received in the environment and is used for normalization.

[0148] Through the above-mentioned weighted fusion method, the influence of time delay and signal strength can be comprehensively considered to obtain a more accurate positioning result, especially in environments with multipath effects and strong noise, which enhances the robustness of the algorithm.

[0149] In order to further improve the positioning accuracy, the Kalman filter algorithm is used to fuse the data of multiple sensors of the AUV. In addition to the time delay and intensity information of the echo signal, the accelerometer, gyroscope and magnetometer of the AUV also provide position information. The state vector of the AUV is , where x, y, z are the position coordinates of the AUV in three-dimensional space, in meters (m); is the velocity component in meters per second (m / s).

[0150] The basic process of Kalman filtering is to use the current measurement value and the system's state transition matrix A to update the AUV's own position estimate :

[0151] The state prediction and covariance update formula is:

[0152] ,

[0153] ;

[0154] in, Indicates the status of the prediction; represents the control input; represents the predicted covariance matrix; A represents the system state transfer matrix; B represents the control input matrix; u k Indicates the control input; P k represents the state estimation covariance matrix; Q represents the process noise covariance matrix.

[0155] According to the motion state of the AUV, such as speed and acceleration, and the environmental changes of the AUV, such as flow rate and pressure difference, the process noise matrix Q is dynamically adjusted:

[0156] ;

[0157] in, Represents the adjustment coefficient, which can dynamically adjust the noise according to factors such as flow rate and signal quality to ensure the accuracy of Kalman filtering; V fIow Indicates the current medium flow rate; V max represents the preset maximum flow rate value, which is used for normalization processing; Q0 represents the static reference process noise covariance matrix.

[0158] Kalman gain K k+1 The calculation formula is:

[0159] ,

[0160] The updated state estimate is calculated as:

[0161] ,

[0162] Among them, Z K+1 Represents the measurement value, which is provided by the USBL system, depth meter, and acoustic reflection positioning system; H represents the observation matrix, and R represents the observation noise covariance matrix.

[0163] By extracting the first three components in the updated state vector, we can obtain the current real-time 3D position estimate of the AUV:

[0164] ;

[0165] in, is the first element of the updated state vector, representing the x-coordinate of the AUV at the current moment; The second element of the updated state vector represents the y coordinate of the AUV at the current moment; The third element of the updated state vector represents the z coordinate of the AUV at the current moment.

[0166] The three-dimensional coordinates of the combined intelligent pig group are calculated based on the current spatial coordinates of the AUV, and the known relative distance d total With direction vector , calculate the position of the combined intelligent pig group and the submarine pipeline where it is located in the three-dimensional space of the seabed (x p ,y p ,z p ):

[0167] ;

[0168] Where: (x, y, z) AUV Indicates the current real-time position of the AUV; Represents a unit direction vector.

[0169] Through the above fusion algorithm, acoustic positioning, sensor data and multipath effects can be considered simultaneously when determining the real-time position of the AUV, providing more accurate positioning results.

[0170] like Figure 1 As shown, the AUV 4 can also be equipped with a sea surface communication buoy 6. When the submarine pipeline 1 is blocked or leaking, the signal emitted by the combined intelligent pig group 2 will generate an echo signal when the sound source contacts the inner wall of the submarine pipeline 1. The echo signal not only provides information on the location of the sound source, but can also be used to detect potential pipeline leaks. By analyzing the echo signal strength Time delay with echo signal The control module can determine whether the echo signal is abnormally strong or has an abnormal time delay, thereby identifying possible leaks. Leaks can cause abnormal echo signal reflection intensity, and the echo intensity is related to factors such as signal attenuation and the nature of the obstacle.

[0171] By setting a threshold I, when the echo intensity exceeds this threshold, the control system can mark the point as a potential leak location, record and store it, and then record the location information on the surface buoy. At this time, AUV 4 releases the surface communication buoy 6. After the surface communication buoy 6 surfaces, the location of the pipeline leak or blockage can be located using a surface workboat 6 or satellite 7.

[0172] After the surface communication buoy 6 carried by the AUV4 surfaces, it transmits continuous electromagnetic signals to the satellite 7 and the surface work ship 6. The satellite 7 and the surface work ship 6 can locate the location of pipeline leakage or blockage based on the electromagnetic signal, thus realizing comprehensive communication between the air, the sea surface and the seabed. Figure 1 shown.

[0173] The above is a detailed introduction to the submarine pipeline offset positioning method and the adaptive sound source frequency adjustment module provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The above description of the disclosed embodiments enables professionals in this field to implement or use the present invention. Various modifications to these embodiments will be obvious to professionals in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for locating submarine pipeline offset, characterized in that: The following steps are involved: S1. Installing a combined intelligent pig assembly at the inlet of a submarine pipeline. The sound source emission device on the combined intelligent pig assembly adaptively adjusts the sound wave emission frequency according to different media in the submarine pipeline using an adaptive sound wave frequency selection method. S2, the AUV follows the combined intelligent pig group and receives the signal from the combined intelligent pig group in real time. The signal propagation distance between the AUV and the combined intelligent pig group is determined by the weighted fusion algorithm. ; S3, update the AUV's own position estimate through the Kalman filter algorithm , thereby determining the position of the submarine pipeline where the combined intelligent pig is located; The specific implementation process of the frequency optimization algorithm in step S1 is as follows: S1.1, Collection and real-time feedback of environmental data; S1.

2. Based on the monitored environmental data, use the frequency optimization algorithm to select the optimal frequency and adjust the sound wave emission frequency of the sound source emission device; S1.3, using an iterative approach to dynamically find the optimal frequency in real time; In step S1.2, determine the optimal sound wave emission frequency range f opt ∈[300Hz,7kHz]; The propagation speed of sound waves in the pipeline medium V signal The calculation formula is: ， in, Indicates the medium temperature value collected in real time; Indicates the medium pressure value collected in real time; Indicates the medium correction item, its value is: ， The attenuation formula of sound wave intensity with distance d is: ， in, d Indicates the distance between the actual measurement point and the sound source, in meters; Indicates the initial signal strength, that is, the signal strength at the sound source, in dB; represents the reference distance, which is the reference standard for normalization; n(f) represents the attenuation factor, and its formula is: n(f)=af+b ， When the medium is oil, a=0.02, b=1.1; when the medium is natural gas, a=0.05, b=1.6; α(f) represents the absorption coefficient of the medium to the sound wave signal, the unit is db / m, and its calculation formula is: ； Define the comprehensive performance index J(f) to maximize the signal-to-noise ratio And minimize the falloff: , Among them, d max Indicates the maximum detection distance of the pipeline; λ indicates the weight coefficient, which is 0.5; The calculation formula of signal-to-noise ratio SNR(f) is: ， in, Indicates the ambient noise power in dB; In step S1.3, the optimal frequency is solved in real time by the gradient ascent method: ， The optimal frequency is solved dynamically in real time using an iterative method. ， in, Represents the frequency update value after the k+1th iteration; Indicates the frequency value at the current k-th iteration; To indicate the frequency adjustment step; Indicates comprehensive performance indicators In frequency The gradient at Set the stop condition to: ； in, Indicates the frequency corresponding to the kth iteration When , the comprehensive performance index is calculated; Indicates the frequency after the next iteration The corresponding performance indicator value.

2. The method for locating submarine pipeline offset according to claim 1, characterized in that: In step S2, the acoustic wave signal emitted by the combined intelligent pig group generates an echo signal due to the multipath effect during the propagation process. , calculate the distance between the AUV and the combined intelligent pig group based on the propagation time delay estimation : , Reversely infer the propagation distance based on the received signal strength The formula is: ， in, Indicates the correction factor of flow velocity on signal attenuation; V flow Indicates the current medium flow rate in m / s; Define the time delay weight factor as : ， Define the signal strength weight factor as : , The final signal propagation distance is calculated using the weighted fusion method : , Among them, I max Indicates the maximum signal strength received in the environment.

3. The method for locating submarine pipeline offset according to claim 1, characterized in that: In step S3, when determining the position of the combined intelligent pig and the submarine pipeline where it is located, the position of the AUV itself is estimated. As a benchmark, the d obtained in step S2 total With direction vector , calculate the position of the pig in the three-dimensional space on the seabed (x p ,y p ,z p ): 。 4. The method for locating submarine pipeline offset according to claim 1, characterized in that: In step S3, the AUV's own position estimate is updated using the Kalman filter algorithm. The specific process is as follows: Get the current state vector of the AUV based on the sensors on the AUV , where x, y, z represent the position coordinates of the AUV in three-dimensional space. represents the velocity component; The state prediction and covariance update formula is: ， ， in, Indicates the status of the prediction; represents the control input; represents the predicted covariance matrix; A represents the system state transfer matrix; B represents the control input matrix; u k Indicates the control input; P k represents the state estimation covariance matrix; Q represents the process noise covariance matrix; According to the motion state of the AUV and the environmental changes of the AUV, the process noise matrix Q is dynamically adjusted: ， in, Indicates the adjustment coefficient; V fIow Indicates the current medium flow rate; V max represents the preset maximum flow rate value; Q0 represents the static reference process noise covariance matrix; Kalman gain K k+1 The calculation formula is: ， The updated state estimate is calculated as: ， Among them, Z K+1 represents the measurement value, which is provided by the USBL system, depth meter, and acoustic reflection positioning system; H represents the observation matrix, and R represents the observation noise covariance matrix; By extracting the first three components in the updated state vector, we can obtain the current real-time 3D position estimate of the AUV: ， in, is the first element of the updated state vector, representing the x-coordinate of the AUV at the current moment; The second element of the updated state vector represents the y coordinate of the AUV at the current moment; The third element of the updated state vector represents the z coordinate of the AUV at the current moment.

5. An adaptive sound source frequency adjustment module, characterized in that: This module includes: The control module is used to configure the phase register of the DDS signal generation module according to the sound source emission frequency; communicate with other modules to perform signal control and real-time feedback; The DDS signal generation module adjusts the frequency to meet the transmission frequency requirements of different submarine pipeline media, generating adjustable frequency signals between 300 Hz and 7 kHz. The DDS frequency register is set via the SPI interface to generate the target frequency. The phase accumulator is used to control the frequency of the output signal. The frequency is accurately controlled by updating the phase register. A low-frequency signal is selected as the reference signal, and the frequency modulation function of the DDS is used to generate other frequencies. The signal filtering and amplification module is used to filter and adjust the gain of the signal generated by the DDS signal generation module, remove high-order harmonics and enhance the signal amplitude; remove unnecessary high-frequency harmonics; and amplify the signal to the required amplitude; A power amplifier module is used to increase the signal power so that it can drive the acoustic transducer; The output module is used to drive the emission of the acoustic wave signal, and uses an acoustic transducer to convert the electrical signal into an acoustic wave; Environmental adaptability module; used to ensure reliability for submarine use; The adaptive sound source frequency adjustment module can accurately select the optimal frequency between 300Hz and 7kHz according to real-time changes in the environment. The propagation speed of sound waves in the pipeline medium is V signal The calculation formula is: ， in, Indicates the medium temperature value collected in real time; Indicates the medium pressure value collected in real time; Indicates the medium correction item, its value is: ， The attenuation formula of sound wave intensity with distance d is: ， in, d Indicates the distance between the actual measurement point and the sound source, in meters; Indicates the initial signal strength, that is, the signal strength at the sound source, in dB; represents the reference distance, which is the reference standard for normalization; n(f) represents the attenuation factor, and its formula is: n(f)=af+b ， When the medium is oil, a=0.02, b=1.1; when the medium is natural gas, a=0.05, b=1.6; α(f) represents the absorption coefficient of the medium to the sound wave signal, the unit is db / m, and its calculation formula is: ； Define the comprehensive performance index J(f) to maximize the signal-to-noise ratio And minimize the falloff: , Among them, d max Indicates the maximum detection distance of the pipeline; λ indicates the weight coefficient, which is 0.5; The calculation formula of signal-to-noise ratio SNR(f) is: ， in, Indicates the ambient noise power in dB; The optimal frequency is solved in real time by the gradient ascent method: ， The optimal frequency is solved dynamically in real time using an iterative method. ， in, Represents the frequency update value after the k+1th iteration; Indicates the frequency value at the current k-th iteration; To indicate the frequency adjustment step; Indicates comprehensive performance indicators In frequency The gradient at Set the stop condition to: ； in, Indicates the frequency corresponding to the kth iteration When , the comprehensive performance index is calculated; Indicates the frequency after the next iteration The corresponding performance indicator value.

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