Underwater robot for pipeline defect detection, and pipeline defect detection method

Abstract

An underwater robot for pipeline defect detection, and a pipeline defect detection method. Several ultrasonic radars (2.2) are arranged at the front end of the underwater robot, a Doppler velocimeter and an inertial navigation system (2.5) are arranged in the middle of the underwater robot, and the ultrasonic radars (2.2) and the Doppler velocimeter are all connected to the inertial navigation system. The Doppler velocimeter is used for: acquiring the actual speed of the underwater robot; and on the basis of the actual speed of the underwater robot, updating the position of the underwater robot. The ultrasonic radars (2.5) are used for acquiring the distance from the underwater robot to the inner wall of a pipeline. The inertial navigation system is used for: on the basis of the actual speed of the underwater robot and the position of the underwater robot, constructing the motion state of the underwater robot; on the basis of the motion state of the underwater robot and observation noise, constructing an observed quantity; on the basis of the observed quantity, obtaining position information of the underwater robot; and on the basis of the distance, determining whether the pipeline has a defect. By means of the method, a three-dimensional stereogram of a pipeline can be quickly and accurately constructed.

Description

An underwater robot for pipeline defect detection and pipeline defect detection method

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This invention claims priority to Chinese patent application No. 202410353577.4 filed with the State Intellectual Property Office of China on March 27, 2024, entitled “AN UNDERWATER ROBOT FOR PIPELINE DEFECT DETECTION AND A METHOD FOR PIPELINE DEFECT DETECTION”, the entire contents of which are incorporated by reference into this invention and constitute a part of this invention for all purposes. Technical Field

[0003] The present invention relates to the field of underwater pipeline robots, and in particular to an underwater robot for pipeline defect detection and a pipeline defect detection method. Background Art

[0004] The statements in this section merely provide background art related to the present invention and do not necessarily constitute prior art.

[0005] Pipeline transportation is the most common method of energy transportation today, particularly for transporting water, oil, and natural gas. Water pipelines are prone to various issues such as wall peeling and corrosion during long-term water transportation. These issues can compromise pipeline safety if not promptly inspected. Therefore, regular inspection and assessment of corrosion and damage to water pipelines is essential.

[0006] Due to the complexity of pipeline engineering, in existing technologies, workers generally enter the pipeline to inspect the inner wall for various problems such as peeling and corrosion. Manual inspection methods are time-consuming and labor-intensive, cannot construct a three-dimensional stereoscopic image of the pipeline, and pose great potential risks to inspectors.

[0007] Summary of the Invention

[0008] In order to address the shortcomings of the existing technology, the present invention provides an underwater robot and a pipeline defect detection method for pipeline defect detection. An underwater robot equipped with a Doppler velocimeter and an ultrasonic radar is used to enter the pipeline for detection. The Doppler velocimeter is used to construct the underwater robot position update equation, and the Kalman filter algorithm is used to estimate the motion state of the underwater robot. The speed data output by the Doppler velocimeter is used as the system observation quantity to observe and correct the system state estimation. The output result after observation and update is used to obtain the precise position information of the underwater robot in the pipeline; the ultrasonic radar obtains the distance from the underwater robot to the inner wall of the pipeline, and the distance information is converted into a spatial coordinate system. The underwater robot position information is integrated to calculate the three-dimensional coordinate points of the inner wall of the pipeline, and the surface reconstruction method is used to construct a three-dimensional stereo image, and defect detection is performed on the inner wall of the pipeline.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A first aspect of the present invention provides an underwater robot for pipeline defect detection.

[0011] An underwater robot for pipeline defect detection, wherein the front end of the underwater robot is provided with several ultrasonic radars, the middle part of the underwater robot is provided with a Doppler velocimeter and an inertial navigation system, and the ultrasonic radars and Doppler velocimeters are both connected to the inertial navigation system;

[0012] The Doppler velocimeter is used to obtain the actual speed of the underwater robot, update the position of the underwater robot according to the actual speed of the underwater robot, and send the actual speed and position of the underwater robot to the inertial navigation system;

[0013] The ultrasonic radar is used to obtain the distance between the underwater robot and the inner wall of the pipe, and send the distance to the inertial navigation system;

[0014] The inertial navigation system is used to construct the motion state of the underwater robot based on the actual speed and position of the underwater robot; construct an observation quantity based on the motion state of the underwater robot and the observed noise; obtain the position information of the underwater robot based on the observation quantity; and determine whether there is a defect in the pipeline based on the distance.

[0015] Furthermore, before obtaining the actual speed of the underwater robot, it also includes taking the headquarters of the underwater robot body as the coordinate origin, the forward direction of the underwater robot as the y-axis, the vertical upward direction perpendicular to the underwater robot body as the z-axis, and determining the horizontal rightward direction perpendicular to the underwater robot body as the x-axis according to the right-handed coordinate system to construct a spatial coordinate system.

[0016] Furthermore, after obtaining the actual speed of the underwater robot, the method further includes: performing coordinate transformation on the actual speed of the underwater robot to obtain the actual speed of the underwater robot in a space coordinate system.

[0017] Furthermore, based on the actual speed of the underwater robot in the space coordinate system, time accumulation is performed to obtain the first position of the underwater robot.

[0018] Furthermore, after obtaining the first position, the Kalman filter algorithm is used to estimate the motion state of the underwater robot, and the speed output by the Doppler tester is used as the system observation quantity to perform observation correction on the system state estimation to obtain the second position of the underwater robot.

[0019] Furthermore, the process of adopting the Kalman filter algorithm includes:

[0020] constructing a motion state of the underwater robot according to the first position of the underwater robot and the actual speed of the underwater robot in the spatial coordinate system;

[0021] Based on the motion state of the underwater robot and combined with the state transfer matrix of the system, the motion state of the underwater robot is updated;

[0022] Construct observations based on the updated underwater robot motion state and measurement noise;

[0023] Determine the system uncertainty covariance matrix, the system state noise covariance matrix, and the noise covariance matrix of the system observations;

[0024] Based on the system uncertainty covariance matrix, the system state noise covariance matrix, the system observation noise covariance matrix and the observation quantity, the underwater robot state is predicted and the second position information of the underwater robot is updated.

[0025] Furthermore, the inertial navigation system is also used to integrate the distance into the position information of the underwater robot to obtain the precise position information of the underwater robot; and construct a three-dimensional stereogram of the pipeline based on the precise position information of the underwater robot.

[0026] Furthermore, after obtaining the distance from the underwater robot to the inner wall of the pipe, the distance is converted into the x-axis and z-axis of the spatial coordinate system, and a coordinate matrix is ​​constructed in combination with the distance from the underwater robot to the inner wall of the pipe; based on the coordinate matrix, the position information of the underwater robot is integrated to obtain the precise position information of the underwater robot.

[0027] Furthermore, the process of determining whether a pipeline has a defect adopts the following formula:

[0028] Among them, L m represents the distance from the underwater robot to the inner wall of the pipe, R represents the diameter of the inner wall of the pipe, and E represents the allowable size of the inner wall peeling or bulging of the pipe; formula (1) indicates the existence of inner wall peeling and corrosion; formula (2) indicates the existence of pipe bulging.

[0029] A second aspect of the present invention provides a pipeline defect detection method.

[0030] A pipeline defect detection method, comprising:

[0031] The Doppler velocimeter is used to obtain the actual speed of the underwater robot, and the position of the underwater robot is updated according to the actual speed of the underwater robot;

[0032] Ultrasonic radar is used to obtain the distance between the underwater robot and the inner wall of the pipe;

[0033] An inertial navigation system is used to construct the motion state of the underwater robot based on the actual speed and position of the underwater robot; an observation quantity is constructed based on the motion state of the underwater robot and the observed noise; based on the observation quantity, the position information of the underwater robot is obtained; and based on the distance, it is determined whether there is a defect in the pipeline.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention equips an underwater pipeline robot with a Doppler velocimeter and an ultrasonic radar to enter the pipeline for inspection, complete defect detection in the pipeline, and construct a three-dimensional stereogram of the pipeline, thereby improving the efficiency and accuracy of pipeline inspection and saving labor costs.

[0036] The present invention combines three technologies: Doppler velocimeter, Kalman filter and ultrasonic radar, which improves the accuracy of constructing pipeline three-dimensional stereograms and speeds up the mapping speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0038] FIG1 is a structural diagram of a pipeline in the present invention;

[0039] FIG2 is a structural diagram of the underwater robot of the present invention;

[0040] Figure 3 is a schematic diagram of the installation of the ultrasonic radar in the xoz plane along the negative direction of the y-axis;

[0041] FIG4 is a flow chart of constructing a three-dimensional pipeline diagram in the present invention;

[0042] In the figure, 1.1 is the entrance for the underwater robot, 1.2 is the pipe, 1.3 is the inner diameter of the pipe, 2.1 is the shell of the underwater robot, 2.2 is the ultrasonic radar, 2.3 is the auxiliary lighting, 2.4 is the snorkeling propulsion system, 2.5 is the Doppler speed meter and inertial navigation system, 2.6 is the moving propulsion system, and α is the angle between the ultrasonic radar and the z-axis. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0044] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0045] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0046] In the present invention, the directions or positional relationships indicated by terms such as "front", "middle", and "tail" are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention. They do not specifically refer to any part or element in the present invention and cannot be understood as limitations on the present invention.

[0047] In the present invention, terms such as "connected" and "connected" should be interpreted broadly, meaning that they can be directly connected or indirectly connected through an intermediary. Relevant researchers or technicians in this field can determine the specific meanings of these terms in the present invention based on specific circumstances, and they should not be construed as limitations on the present invention.

[0048] In the absence of conflict, the embodiments of the present invention and the features thereof may be combined with each other.

[0049] Example 1

[0050] Embodiment 1 of the present invention provides an underwater robot for pipeline defect detection, wherein the front end of the underwater robot is provided with several ultrasonic radars, the middle portion of the underwater robot is provided with a Doppler velocimeter and an inertial navigation system, and the ultrasonic radars and Doppler velocimeters are both connected to the inertial navigation system;

[0051] The Doppler velocimeter is used to obtain the actual speed of the underwater robot, update the position of the underwater robot according to the actual speed of the underwater robot, and send the actual speed and position of the underwater robot to the inertial navigation system;

[0052] The ultrasonic radar is used to obtain the distance between the underwater robot and the inner wall of the pipe, and send the distance to the inertial navigation system;

[0053] The inertial navigation system is used to construct the motion state of the underwater robot based on the actual speed and position of the underwater robot; construct an observation quantity based on the motion state of the underwater robot and the observed noise; obtain the position information of the underwater robot based on the observation quantity; and determine whether there is a defect in the pipeline based on the distance.

[0054] As shown in FIG1 and FIG2, in this embodiment, the radius of the inner wall of the pipeline is selected to be 2000 mm, and the underwater robot is placed into the pipeline 1.2 through the underwater robot introduction port 1.1, so that the ultrasonic radar 2.2 is facing the pipeline 1.2.

[0055] As shown in Figure 2, the underwater robot includes an underwater robot shell 2.1, a number of ultrasonic radars 2.2 are installed in front of the underwater robot shell 2.1, a number of auxiliary lighting lamps 2.3 are provided on the outer peripheral surface of the underwater robot shell 2.1, two snorkeling thrusters 2.4 are also provided in the middle of the underwater robot shell 2.1, a Doppler speed meter and an inertial navigation system 2.5 are installed below the middle end of the underwater robot shell 2.1, and a moving thruster 2.6 is provided at the tail end of the underwater robot.

[0056] Specifically, as shown in FIG3 , the ultrasonic radar on the z-axis is marked as ultrasonic radar No. 1 3.1 , and an ultrasonic radar is installed every 10 degrees α in the counterclockwise direction around the y-axis, with the detection direction perpendicular to the direction of the robot body.

[0057] As shown in FIG4 , the technical solution of this embodiment may include two parts:

[0058] Part 1: Construct the Doppler velocimeter output velocity equation and the underwater robot position update equation, including the Kalman filter algorithm for underwater robot motion state prediction and correction;

[0059] Part 2: Ultrasonic radar obtains the distance between the underwater robot and the inner wall of the pipeline to determine whether there is a problem with the pipeline. The distance data is further processed to obtain three-dimensional spatial coordinate points, and the surface reconstruction method is used to construct a three-dimensional stereogram of the pipeline.

[0060] The first part of obtaining the precise location information of the underwater robot includes the following steps:

[0061] Step 1: Establish the Doppler velocity model in the spatial coordinate system. Define the Doppler velocity meter output value as v DVL .

[0062] Specifically, in step 1, a spatial coordinate system is established, with the middle of the underwater robot body as the coordinate origin, the forward direction of the underwater robot as the y-axis, the vertical upward direction of the vertical robot body as the z-axis, and the horizontal rightward direction of the vertical robot body as the x-axis according to the right-handed coordinate system.

[0063] An ultrasonic radar is installed in front of the robot body. The installation direction of the ultrasonic radar is perpendicular to the pipe surface, so that when it detects the inner wall of the pipe, the ultrasonic radar is detecting the inner wall of the pipe; a Doppler velocimeter is installed below the middle end of the robot body.

[0064] Step 2: The actual speed of the underwater robot can be calculated from the Doppler velocimeter measurement value obtained in step 1: v = (1 + δKDVK )v DVL

[0065] Among them, δK DVL is the Doppler velocimeter scale factor error.

[0066] Step 3: The speed update is completed by step 2, and the actual speed of the underwater robot along the y-axis in the spatial coordinate system can be obtained. The position update can be obtained by accumulating the y-axis speed time in the spatial coordinate system. The position update equation can be expressed as p k =p k-1 +v k *Δt

[0067] Among them, p k is the position of the underwater robot at time k; p k-1 is the position of the underwater robot at time k-1; v k is the actual speed of the underwater robot at time k, obtained from the formula in step 2; Δt = t k -t k-1 is the time interval from time k-1 to time k.

[0068] Step 4: Use the Kalman filter algorithm to estimate the motion state of the underwater robot, and use the speed data output by the Doppler velocimeter as the system observation quantity z k , the system state estimate is observed and corrected, and the output result after observation update is the optimal estimate of the underwater robot's position.

[0069] Specifically, in step 4, the steps of Kalman filter position estimation are as follows:

[0070] Step 41: Initialize parameters of the Kalman filter position estimation system

[0071] Since the observed data is the motion state of the underwater robot in the pipeline, the system state vector at the kth moment is Select the motion state of the underwater robot p k The position of the underwater robot at time k is calculated by the underwater robot position update equation in step 3, v k is the speed of the underwater robot at time k, and the state vector The dimension is 2*1.

[0072] Establish the state equation of the system and determine the state transfer matrix of the system

[0073] in, is the motion state of the underwater robot at the k-1th moment, w k-1is the process noise of the system at time k-1, P(w)~N(0,Q).

[0074] This system has an observation z k , is the real-time speed of the underwater robot output by the Doppler velocimeter;

[0075] Where H is the observation matrix, H = [0 1]; y k The velocity data output by the Doppler velocimeter is used as the system observation z k The measurement noise at time k is P(y)~N(0,R).

[0076] Initialize system status Initialize the system uncertainty covariance matrix P0, the system state noise covariance matrix Q and the system observation z k The noise covariance matrix R of

[0077] Step 42: Estimate the motion state of the underwater robot at time k based on the motion state of the underwater robot at time k-1

[0078] Step 43: Determine a priori estimate of the system uncertainty covariance matrix

[0079] Step 44: Calculate the Kalman gain K based on the data of the observation matrix H k :

[0080] Step 45: Update the posterior uncertainty covariance matrix of the calculation system

[0081] Step 46: The velocity data output by the Doppler velocimeter is used as the system observation quantity z k Observation correction is performed on the state estimate of the system, z k represents the value of observation z at the kth moment,

[0082] Get updated underwater robot state estimate in p k The element is the precise location information of the underwater robot.

[0083] Step 5: Iterate steps 3 and 4 to continuously estimate the underwater robot state to obtain accurate underwater robot position information.

[0084] The second part of building a 3D pipeline diagram includes the following steps:

[0085] Step 6: Ultrasonic radar ranging is calculated as follows: L = CT

[0086] Where L is the measured distance; C is the propagation speed of ultrasound in water; and T is half the time from the ultrasound being emitted to being received.

[0087] Step 7: Mark the ultrasonic radar on the z-axis as ultrasonic radar No. 1. Install an ultrasonic radar every α degrees counterclockwise around the y-axis. The value of α must be a factor of 360. A total of 360 / α ultrasonic radars are installed. The range of the mth ultrasonic radar is: L m =CT

[0088] Convert the measured distance to the x-axis and z-axis of the spatial coordinate system:

[0089] Among them, x m The distance measurement of the mth ultrasonic radar is converted to the x-axis coordinate point in the spatial coordinate system; z m is the z-axis coordinate point converted from the m-th ultrasonic radar’s ranging value to the spatial coordinate system; mα is the angle between the m-th ultrasonic radar and the z-axis.

[0090] Optionally, an ultrasonic radar is installed every 10 degrees counterclockwise around the y-axis, and a total of 36 ultrasonic radars are installed.

[0091] Specifically, in step 7, assuming that the inner wall diameter of the pipe is 1.3 and is R, and the allowable size of the inner wall peeling or bulging is E, the relationship between the distance measured by all ultrasonic radars and the inner wall diameter is detected in sequence during the underwater robot's forward movement:

[0092] Among them, formula (1) indicates that the inner wall of the pipeline is peeling and corroded; formula (2) indicates that the pipeline is bulging.

[0093] Step 8: Add the y-axis position information to the above steps to form the following matrix:

[0094] Among them, y m The precise position of the underwater robot when the mth ultrasonic radar measures the distance is converted to the y-axis coordinate point in the spatial coordinate system.

[0095] As the underwater robot continues to move forward, the spatial coordinate point at time k can be measured as:

[0096] Among them, x k The distance measured by all ultrasonic radars at time k is converted to the x-axis coordinate point in the spatial coordinate system; y kis the y-axis coordinate point of the underwater robot's precise position at time k converted to the spatial coordinate system; z k Convert the distances measured by all ultrasonic radars at time k to the z-axis coordinate points in the spatial coordinate system.

[0097] The obtained spatial coordinate points are used to reconstruct the surface through a rendering-based voxelization method to obtain a complete visible image of the inner wall of the pipeline.

[0098] Example 2

[0099] This embodiment provides a pipeline defect detection method, including:

[0100] The Doppler velocimeter is used to obtain the actual speed of the underwater robot, and the position of the underwater robot is updated according to the actual speed of the underwater robot;

[0101] Ultrasonic radar is used to obtain the distance between the underwater robot and the inner wall of the pipe;

[0102] An inertial navigation system is used to construct the motion state of the underwater robot based on the actual speed and position of the underwater robot; an observation quantity is constructed based on the motion state of the underwater robot and the observed noise; based on the observation quantity, the position information of the underwater robot is obtained; and based on the distance, it is determined whether there is a defect in the pipeline.

[0103] In addition, this embodiment also includes integrating the distance into the underwater robot position information to obtain the precise position information of the underwater robot; and constructing a three-dimensional stereogram of the pipeline based on the precise position information of the underwater robot.

[0104] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An underwater robot for pipeline defect detection, wherein the front end of the underwater robot is provided with several ultrasonic radars, characterized in that: A Doppler velocimeter and an inertial navigation system are provided in the middle of the underwater robot, and the ultrasonic radar and the Doppler velocimeter are both connected to the inertial navigation system; The Doppler velocimeter is used to obtain the actual speed of the underwater robot, update the position of the underwater robot according to the actual speed of the underwater robot, and send the actual speed and position of the underwater robot to the inertial navigation system; The ultrasonic radar is used to obtain the distance between the underwater robot and the inner wall of the pipe, and send the distance to the inertial navigation system; The inertial navigation system is used to construct the motion state of the underwater robot based on the actual speed and position of the underwater robot; construct an observation quantity based on the motion state of the underwater robot and the observed noise; obtain the position information of the underwater robot based on the observation quantity; and determine whether there is a defect in the pipeline based on the distance.

2. The underwater robot for pipeline defect detection according to claim 1, characterized in that: Before obtaining the actual speed of the underwater robot, the method also includes taking the headquarters of the underwater robot body as the coordinate origin, the forward direction of the underwater robot as the y-axis, the vertical upward direction perpendicular to the underwater robot body as the z-axis, and the horizontal rightward direction perpendicular to the underwater robot body as the x-axis according to the right-handed coordinate system to construct a spatial coordinate system.

3. The underwater robot for pipeline defect detection according to claim 1, characterized in that: After obtaining the actual speed of the underwater robot, the method further includes: performing coordinate transformation on the actual speed of the underwater robot to obtain the actual speed of the underwater robot in a space coordinate system.

4. The underwater robot for pipeline defect detection according to claim 3, characterized in that: Based on the actual speed of the underwater robot in the spatial coordinate system, time accumulation is performed to obtain the first position of the underwater robot.

5. The underwater robot for pipeline defect detection according to claim 4, characterized in that: After obtaining the first position, the Kalman filter algorithm is used to estimate the motion state of the underwater robot. The speed output by the Doppler tester is used as the system observation quantity, and the system state estimation is observed and corrected to obtain the second position of the underwater robot.

6. The underwater robot for pipeline defect detection according to claim 5, characterized in that: The process of adopting the Kalman filter algorithm includes: constructing a motion state of the underwater robot according to the first position of the underwater robot and the actual speed of the underwater robot in the spatial coordinate system; Based on the motion state of the underwater robot and combined with the state transfer matrix of the system, the motion state of the underwater robot is updated; Construct observations based on the updated underwater robot motion state and measurement noise; Determine the system uncertainty covariance matrix, the system state noise covariance matrix, and the noise covariance matrix of the system observations; Based on the system uncertainty covariance matrix, the system state noise covariance matrix, the system observation noise covariance matrix and the observation quantity, the underwater robot state is predicted and the second position information of the underwater robot is updated.

7. The underwater robot for pipeline defect detection according to claim 1, characterized in that: The inertial navigation system is further used to integrate the distance into the position information of the underwater robot to obtain the precise position information of the underwater robot; and to construct a three-dimensional stereogram of the pipeline based on the precise position information of the underwater robot.

8. The underwater robot for pipeline defect detection according to claim 7, characterized in that: After obtaining the distance from the underwater robot to the inner wall of the pipe, the distance is converted to the x-axis and z-axis of the spatial coordinate system, and a coordinate matrix is ​​constructed based on the distance from the underwater robot to the inner wall of the pipe. Based on the coordinate matrix, the underwater robot position information is integrated to obtain the underwater robot's precise position information.

9. The underwater robot for pipeline defect detection according to claim 1, characterized in that: The process of determining whether a pipeline has defects uses the following formula: Among them, L m represents the distance from the underwater robot to the inner wall of the pipe, R represents the diameter of the inner wall of the pipe, and E represents the allowable size of the inner wall peeling or bulging of the pipe; formula (1) indicates the existence of inner wall peeling and corrosion; formula (2) indicates the existence of pipe bulging.

10. A pipeline defect detection method, characterized in that: include: The Doppler velocimeter is used to obtain the actual speed of the underwater robot, and the position of the underwater robot is updated according to the actual speed of the underwater robot; Ultrasonic radar is used to obtain the distance between the underwater robot and the inner wall of the pipe; An inertial navigation system is used to construct the motion state of the underwater robot based on the actual speed and position of the underwater robot; an observation quantity is constructed based on the motion state of the underwater robot and the observed noise; based on the observation quantity, the position information of the underwater robot is obtained; and based on the distance, it is determined whether there is a defect in the pipeline.

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