Auv-based seabed in-situ testing and formation structure collaborative detection method and system

Abstract

The present application relates to the technical field of marine engineering geology investigation, in particular to a seabed in-situ testing and stratum structure cooperative detection method and system based on AUV, the method comprises the following steps: demarcating the cruising area of AUV on the mother ship, and then configuring the detection task of AUV; AUV performs seabed in-situ testing and stratum structure detection according to the detection task; when performing the detection task, AUV makes online intelligent decision according to the real-time detection result, dynamically adjusts the detection task when geological anomaly and meaningful stratum extension appear, and periodically generates a simplified report and transmits it to the mother ship; after AUV returns to the mother ship, the collected data is exported from AUV, and then a three-dimensional stratum model of the cruising area is constructed on the mother ship. The present application realizes the integration and cooperative operation of seabed geophysical detection and geotechnical in-situ testing, and can make intelligent online decision and adaptive task planning for seabed detection, realizing the transformation from preset exploration to adaptive detection.

Description

Technical Field

[0001] This invention relates to the field of marine engineering geological survey technology, and in particular to a method and system for collaborative detection of seabed in-situ testing and stratigraphic structure based on AUV. Background Technology

[0002] Traditional seabed geological survey methods mainly fall into two technical categories: The first is a surface vessel-based geophysical exploration method, which uses shipborne shallow seismic profilers, side-scan sonar, and other equipment to achieve large-scale, continuous seabed geological structure detection. While this method offers wide coverage and fast operation, it can only obtain geophysical parameters and cannot directly acquire the mechanical parameters of the soil, making it difficult to meet the needs of marine engineering construction for accurate assessment of foundation geotechnical properties.

[0003] The second method is to use a dedicated seabed drilling platform or a heavy static cone penetration test (CPT) device for in-situ seabed testing. Although this method can obtain accurate geomechanical parameters, it has the following significant drawbacks: (1) The equipment is large and heavy, and the deployment and retrieval operations are complex, requiring large operating vessels and dedicated hoisting equipment; (2) The cost of a single operation in deep water areas is high; (3) The operation efficiency is low, making it difficult to achieve large-scale, multi-point continuous detection; (4) The in-situ test data obtained is difficult to accurately register with the geophysical exploration data in space, which restricts the comprehensive interpretation effect of the data.

[0004] With the rapid development of Autonomous Underwater Vehicle (AUV) technology, its application in underwater exploration is becoming increasingly widespread. Integrating CPT (Cyclic Penetration Testing) technology with AUV platforms to achieve in-situ seabed geological testing and coordinated exploration of stratigraphic structures would be of great significance for the accurate interpretation of seabed geological data. However, integrating CPT technology into AUV platforms faces several technical challenges: First, CPT penetration testing requires the platform to sit on the seabed and provide sufficient reaction force, while traditional AUVs typically lack the ability to sit on the seabed and cannot provide the reaction force required for CPT penetration, thus failing to meet testing requirements. Second, in-situ seabed geological testing and coordinated exploration of stratigraphic structures require the exploration system to have real-time data processing and intelligent decision-making capabilities, thereby dynamically adjusting the operational plan based on preliminary exploration results. However, existing AUV systems lack such in-situ data processing methods and capabilities. Furthermore, the amount of raw data generated by CPT testing is enormous, and due to the low bandwidth characteristics of underwater acoustic communication, it is difficult to transmit all the data in real time. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and system for collaborative detection of seabed in-situ testing and geological structures based on AUV.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for coordinated seabed in-situ testing and geological structure detection based on an AUV. The method includes the following steps: delineating the cruising area of ​​an autonomous underwater vehicle (AUV) on a mother ship, and then configuring the AUV's detection tasks; the AUV includes a suction anchor unit, a CPT (Continuous Threat Transmission) unit, a shallow seismic profiling unit, an acoustic communication and positioning unit, and an underwater robot platform; the suction anchor unit is used to attach the AUV to the seabed; the CPT unit is used to perform in-situ CPT testing; the shallow seismic profiling unit is used to acquire acoustic profile data of shallow geological structures below the seabed; the acoustic communication and positioning unit is used to acquire the absolute position of the AUV, and to achieve communication between the mother ship and the AUV platform. The invention describes the information transmission between autonomous underwater vehicles (AUVs). The AUV platform carries the suction anchor unit, the CPT detection unit, the shallow seismic profiling unit, and the acoustic communication and positioning unit to conduct in-situ seabed testing and collaborative geological structure exploration. The AUVs perform in-situ seabed testing and geological structure exploration according to the exploration tasks. During the exploration tasks, the AUVs make online intelligent decisions based on real-time detection results, dynamically adjusting the exploration tasks when geological anomalies or significant stratigraphic extensions are observed, and periodically generating concise reports that are transmitted to the mother ship. After returning to the mother ship, the collected data is exported from the AUVs, and a three-dimensional geological model of the cruising area is constructed on the mother ship. This invention achieves integrated collaborative operation of seabed geophysical exploration and in-situ geotechnical testing, and enables intelligent online decision-making and adaptive task planning for seabed exploration, realizing a shift from pre-defined exploration to adaptive exploration.

[0007] Optionally, the underwater robot platform includes: The navigation and positioning module is used to acquire the calculated position, attitude, speed, depth and height above the bottom of the underwater robot platform in real time. An energy module, which provides electrical power to the underwater robot platform; A buoyancy adjustment module, which is used to control the diving and surfacing of the underwater robot platform; A power propulsion module, which is used to realize the six-degree-of-freedom omnidirectional drive of the underwater robot platform; The control module is used to control the autonomous underwater robot to complete the exploration task, including motion control, online intelligent decision-making, dynamic adjustment of the exploration task, and generation of simplified reports and three-dimensional stratigraphic models. The control module is also used to correct the cumulative error of the navigation and positioning module based on the absolute position provided by the acoustic communication and positioning unit.

[0008] Optionally, the step of defining the cruise area of ​​the autonomous underwater vehicle (AUV) on the mother ship and then configuring the AUV's exploration tasks includes the following steps: The autonomous underwater vehicle's cruising area is delineated on the mother ship's electronic chart, and survey lines and CPT in-situ test points are preset within the cruising area. The operating parameters of the autonomous underwater robot are set, including cruising speed, sea clearance, equipment operating parameters, and communication cycle. The cruise area, the survey line, the CPT in-situ test point, and the working parameters are encapsulated into a mission instruction package and sent to the autonomous underwater robot. The autonomous underwater robot receives and parses the mission instruction packet, thereby completing the initialization of the exploration mission.

[0009] Optionally, the autonomous underwater robot performs in-situ seabed testing and stratigraphic exploration according to the exploration mission, including the following steps: The autonomous underwater robot performs a fixed-altitude cruise along the survey line and continuously collects acoustic profile data of the shallow seabed strata structure, thereby extracting acoustic strata information. Upon reaching the CPT in-situ test point, the autonomous underwater robot sits on the seabed and performs CPT in-situ testing to obtain CPT test data, thereby acquiring measured stratigraphic information on the shallow subsurface structure below the seabed. After completing the CPT in-situ test, the autonomous underwater robot detaches from the seabed and continues to navigate along the survey line.

[0010] Optionally, the CPT test data includes the cone tip resistance, sidewall friction resistance, and excess pore water pressure when the CPT probe penetrates the seabed soil.

[0011] Optionally, when performing the exploration mission, the autonomous underwater vehicle makes online intelligent decisions based on real-time exploration results, dynamically adjusts the exploration mission when geological anomalies and significant stratigraphic extensions are detected, and periodically generates concise reports that are transmitted to the mother ship, including the following steps: If a key stratum does not end at the end of the survey line, the autonomous underwater robot extends the survey line based on the acoustic profile data and the measured stratum information. The autonomous underwater robot determines whether geological anomalies have occurred based on a preset geological model, the acoustic stratigraphic information, and the measured stratigraphic information. If no geological anomaly is found, the autonomous underwater robot will continue to perform its original exploration mission. If the geological anomaly occurs, the autonomous underwater vehicle generates an encrypted detection task based on the anomaly type and inserts the encrypted detection task into the task queue of the detection task for execution. The autonomous underwater robot generates a simplified report based on the detection results and transmits it to the mother ship according to the communication cycle.

[0012] Optionally, the autonomous underwater robot determines whether a geological anomaly has occurred based on a preset geological model, the acoustic stratigraphic information, and the measured stratigraphic information, including the following steps: The autonomous underwater robot compares the acoustic stratigraphic information with the preset geological model; When the acoustic profile data at a certain location is inconsistent with the preset geological model, it is determined that a geological anomaly has occurred at that location; The measured stratigraphic information at the CPT in-situ test point is compared with the acoustic stratigraphic information. If the deviation between the two exceeds a preset threshold, the geological anomaly at that location is determined to have occurred.

[0013] Optionally, the anomaly types include acoustic geological anomalies and measured geological anomalies; If the geological anomaly occurs, the autonomous underwater vehicle generates an encrypted detection task based on the anomaly type, inserts the encrypted detection task into the task queue of the detection tasks, and executes it, including the following steps: If the geological anomaly is an acoustic geological anomaly, then generate a densified survey line parallel to the current survey line, insert it into the task queue of the exploration task, and execute it after replanning the navigation path; If the geological anomaly is a measured geological anomaly, then encrypted measuring points are generated around the corresponding CPT in-situ test point, inserted into the task queue of the exploration mission, and the navigation path is replanned before execution.

[0014] This method has at least the following beneficial effects: 1. This method integrates the shallow seismic profiler and the CPT detection unit on the same AUV platform, and for the first time realizes the integrated collaborative operation of seabed geophysical exploration and in-situ rock and soil mechanics testing, ensuring the spatiotemporal synchronization and deep fusion of multi-source data. 2. Based on the high mobility of AUVs, this method can autonomously complete movement, positioning, bottoming test and rapid disengagement in a single dive mission, realizing continuous, multi-point and efficient in-situ exploration, which completely changes the traditional CPT single-point static operation mode. 3. The design of the flat underwater robot platform is combined with negative buoyancy bottoming and suction anchor adsorption technology. While maintaining good underwater maneuverability, it can provide a stable and reliable reaction force foundation for CPT penetration and adapt to complex seabed topography. 4. The AUV has intelligent online decision-making and adaptive task planning capabilities. It can dynamically identify geological anomalies, optimize the exploration plan, and autonomously supplement CPT measurement points based on real-time collected shallow seismic profile data and CPT test data, realizing the transformation from pre-set exploration to adaptive exploration. 5. It can perform real-time processing and geotechnical parameter interpretation on CPT raw data at the AUV end, and automatically extract key geological conclusions, effectively addressing the challenges of underwater large-scale data processing; 6. By generating simplified reports, FEC encoding, MPSK modulation, and power amplification, this method achieves reliable and efficient transmission of key data and commands in low-bandwidth underwater acoustic channels, ensuring real-time linkage between underwater operations and surface command.

[0015] Secondly, this invention provides an AUV-based in-situ seabed testing and stratigraphic structure collaborative detection system. The system utilizes the AUV-based in-situ seabed testing and stratigraphic structure collaborative detection method provided by this invention. The system includes: a mothership, used to delineate the cruise area of ​​an autonomous underwater vehicle (AUV) and initialize its detection tasks; after the AUV returns to the mothership, the collected data is exported from the AUV, and a three-dimensional stratigraphic model of the cruise area is constructed on the mothership; and an AUV, comprising a suction anchor unit, a CPT (Crystal Profiling) unit, a shallow seismic profiling unit, an acoustic communication and positioning unit, and an underwater robot platform; the suction anchor unit is used to attach the AUV to the seabed; and the CPT unit is used to perform CPT detection... The system includes: PT in-situ testing; the shallow seismic profiling unit for acquiring acoustic profile data of shallow subsurface structures below the seabed; the acoustic communication and positioning unit for acquiring the absolute position of the autonomous underwater vehicle (AUV) and enabling information transmission between the mother ship and the AUV; the underwater robot platform carrying the suction anchor unit, the CPT detection unit, the shallow seismic profiling unit, and the acoustic communication and positioning unit for conducting in-situ seabed testing and collaborative seismic structure detection; the AUV performing in-situ seabed testing and collaborative seismic structure detection according to the detection task; and, during the detection task, making online intelligent decisions based on real-time detection results, dynamically adjusting the detection task when geological anomalies or significant seismic extensions occur, and periodically generating concise reports for transmission to the mother ship. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating the method for coordinated detection of seabed in-situ testing and stratigraphic structure based on AUV, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the external shape of the underwater robot platform according to an embodiment of the present invention; Figure 3 This is a top view of the AUV according to an embodiment of the present invention; Figure 4 This is a side view of an AUV according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the framework of the AUV-based in-situ seabed testing and stratigraphic structure collaborative detection system according to an embodiment of the present invention.

[0018] In the diagram: 1-Suction anchor unit, 2-CPT detection unit, 3-Shallow stratum profile detection unit, 4-Acoustic communication and positioning unit, 5-Underwater robot platform, 6-Navigation and positioning module, 7-Energy module, 8-Buoyancy adjustment module, 9-Main thruster, 10, 11, 12-Vertical thrusters, 13-Control module, 14-Cutting edge, 15-Lock-off valve. Detailed Implementation

[0019] Specific embodiments of the present invention will now be described in detail. It should be noted that the embodiments described herein are for illustrative purposes only and are not intended to limit the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other instances, well-known circuits, software, or methods have not been specifically described to avoid obscuring the invention.

[0020] Throughout this specification, references to "an embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "in an embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale.

[0021] It should be noted in advance that, in one alternative embodiment, except for independent descriptions, the same symbols or letters appearing in all formulas have the same meaning.

[0022] In one optional embodiment, please refer to Figures 1 to 4 This invention provides a method for coordinated detection of seabed in-situ testing and stratigraphic structure based on AUV, the method comprising the following steps: S1. Delineate the patrol area of ​​the autonomous underwater vehicle on the mother ship, and then configure the detection tasks of the autonomous underwater vehicle.

[0023] Step S1 specifically includes the following steps: S11. Delineate the cruising area of ​​the autonomous underwater vehicle on the electronic chart of the mother ship, and pre-set survey lines and CPT in-situ test points within the cruising area.

[0024] Specifically, in this embodiment, during the preparation phase of the operation, the operator delineates the rectangular cruising area of ​​the Autonomous Underwater Vehicle (AUV) on the electronic nautical chart of the mother ship (also known as the survey vessel) based on the regional geological background data of the target sea area and the specific objectives of this survey mission. Based on this, the operator pre-defines multiple parallel survey lines within the area and numbers them. All pre-define survey lines are parallel to the long side of the cruise area (i.e., the direction of the main survey line), and the vertical distance between adjacent pre-define survey lines is equal (preferably 150 meters), so that the AUV can achieve full coverage scanning of the cruise area according to these survey lines. The shortest distance between the first pre-define survey line and the long side of the cruise area should not be less than the densification spacing described later, and the last pre-define survey line is set in a similar manner. Each pre-define survey line has a starting point and an ending point, and the starting points and ending points of adjacent pre-define survey lines are arranged alternately, that is, the ending point of the previous survey line is closest to the starting point of the next survey line, thus forming an "S"-shaped continuous navigation trajectory. Subsequently, several CPT in-situ test points are pre-defined on the survey lines. These pre-define CPT in-situ test points are usually selected based on the stratigraphic distribution patterns revealed by existing geological data and the key strata of engineering concern, serving as control points for obtaining geotechnical mechanical parameters in the cruise area during the preliminary investigation stage.

[0025] More specifically, the AUV includes a suction anchor unit 1, a CPT detection unit 2, a shallow seismic profiling unit 3, an acoustic communication and positioning unit 4, and an underwater robotic platform 5. The suction anchor unit 1 is used to attach the AUV to the seabed; the CPT detection unit 2 is used to conduct in-situ CPT testing and obtain CPT test data; the shallow seismic profiling unit 3 is used to acquire acoustic profile data of the shallow subsurface structure below the seabed; the acoustic communication and positioning unit 4 is used to obtain the absolute position of the AUV and to achieve information transmission between the mother ship and the AUV; the underwater robotic platform 5 is used to carry the suction anchor unit 1, CPT detection unit 2, shallow seismic profiling unit 3, and acoustic communication and positioning unit 4 to conduct in-situ seabed testing and collaborative exploration of the subsurface structure.

[0026] The suction anchor unit 1, integrated into the lower middle part of the underwater robot platform 5, is a device that provides a large reaction force for CPT penetration testing. It consists of a sealed housing, a high-pressure bidirectional seawater pump, a locking valve 15, and pressure sensors. The sealed housing is an inverted, disc-shaped structure fixedly connected to the bottom of the AUV at its top. It is precision-cast from high-strength stainless steel, and pressure sensors are installed inside and outside. Its bottom edge is specially ground to form a continuous and sharp cutting edge 14. This cutting edge is designed to cut into the seabed surface sediment to the maximum extent when the AUV is on the bottom, forming an initial, relatively closed chamber. The high-pressure bidirectional seawater pump is a seawater-resistant ceramic plunger pump with a rated operating pressure of not less than 2MPa. It has precise flow and pressure control capabilities and is connected to the inner cavity of the sealed housing through a pressure-resistant pipeline. The locking valve 15 is a normally closed electrically controlled sea valve integrated into the pressure-resistant pipeline of the high-pressure bidirectional seawater pump.

[0027] The CPT detection unit 2 is integrated into the lower middle part of the underwater robot platform 5. It is the direct actuator for acquiring seabed rock and soil mechanical parameters. It consists of a hollow shaft servo motor, an electric cylinder, a displacement sensor, a probe rod, and a CPT probe. The hollow shaft servo motor and displacement sensor are installed inside the underwater robot platform 5. The piston rod of the electric cylinder is fixed to one end of a high-strength, low-friction probe rod. The horizontal distance between the probe rod axis and the geometric center of the sealing cover of the suction anchor unit 1 is 60 mm. The other end of the probe rod is equipped with an internationally standard CPT probe. The CPT probe integrates three core sensors, including a cone tip resistance sensor, a pore water pressure sensor, and a sidewall friction sensor, used to acquire CPT test data including cone tip resistance, sidewall friction, and excess pore water pressure. The displacement sensor is a differential transformer type displacement sensor. Its body is fixed to the rear housing of the hollow shaft servo motor. Its iron core push rod passes through the central hole of the hollow shaft servo motor and is connected to the rear end of the piston rod of the electric cylinder to follow the linear movement of the piston rod in real time and obtain the piston rod displacement signal. The cone tip resistance sensor is located at the very tip of the CPT probe and uses a foil strain gauge to measure the inter-cone resistance of the soil against the cone tip of the CPT probe. The sidewall friction resistance sensor is located on the friction sleeve behind the cone tip and measures the friction force between the soil and the outer surface of the friction sleeve, i.e., the sidewall friction resistance. This friction sleeve is a sleeve-type structure independent of the probe rod and is fixedly mounted on the CPT probe body. The pore water pressure sensor is located behind the cone tip, between the cone tip resistance sensor and the sidewall friction resistance sensor. It uses a piezoelectric or piezoresistive pressure sensor to measure the excess pore water pressure generated during the penetration of the CPT probe into the soil.

[0028] The shallow seismic profiling unit 3, integrated into the lower rear of the AUV, is a parametric array shallow seismic profiler. It detects seabed strata by simultaneously emitting two high-frequency primary frequency sound waves of similar frequencies. Utilizing the nonlinear effect of the seawater medium, a low-frequency sound wave is generated during sound wave propagation due to the "difference frequency." Its transducer is small and lightweight, making it ideal for AUV mounting. Furthermore, the parametric array shallow seismic profiler offers high resolution, reaching centimeter-level accuracy, which helps achieve high-resolution imaging of the seabed strata.

[0029] The acoustic communication and positioning unit 4 is integrated on the upper front of the underwater robot platform 5. It consists of an underwater acoustic communication transceiver, a transducer array, and an Ultra-Short Baseline (USBL) signal processing board. It is used to achieve bidirectional data transmission between the AUV and the surface mother ship, as well as to acquire the AUV's absolute underwater position. This unit integrates both underwater acoustic communication and USBL positioning functions. Both share the same transducer array for transmitting and receiving acoustic signals. The USBL signal processing unit performs demodulation and decoding based on the signal type (communication signal or positioning signal). Furthermore, the underwater acoustic communication transceiver employs Multiple Phase Shift Keying (MPSK) modulation technology and Forward Error Correction (FEC) coding technology to achieve reliable data transmission in complex underwater acoustic channels.

[0030] The suction anchor unit 1, CPT detection unit 2, shallow seismic profiling unit 3, and acoustic communication and positioning unit 4 are all electrically connected to the underwater robot platform 5 via watertight connectors. These watertight connectors can be embedded in the mounting holes of the robot platform, forming a radial seal with the bulkhead through O-rings, ensuring the sealing reliability and insulation safety of the electrical connections under the high pressure environment of the deep sea.

[0031] The underwater robot platform 5 abandons the torpedo-shaped structure and adopts a flat structure, which is welded or bolted together from 6-series aluminum alloy profiles. Its overall shape is a large-scale plate-like configuration spread out in the horizontal plane, with relatively small vertical dimensions. This flat configuration increases the contact projection area with the seabed when the autonomous underwater vehicle (AUV) lands, thereby improving initial stability. Simultaneously, the upper and lower surfaces of the underwater robot platform 5 are continuous planes. The lower surface, from bow to stern, has pre-reserved mounting interfaces for fixing the CPT detection unit 2, the suction anchor unit 1, and the shallow seismic profiling unit 3, respectively. The upper surface of the bow has pre-reserved mounting interfaces for fixing the acoustic communication and positioning unit 4.

[0032] Furthermore, the underwater robot platform 5 includes a navigation and positioning module 6, an energy module 7, a buoyancy adjustment module 8, a propulsion module, and a control module 13. The navigation and positioning module 6 is used to acquire real-time information on the calculated position, attitude, speed, depth, and height above the bottom of the underwater robot platform 5. The energy module 7, installed within the underwater robot platform 5, provides electrical power to the underwater robot platform 5, specifically a lithium battery. The buoyancy adjustment module 8 controls the underwater robot platform 5's diving and surfacing. The propulsion module enables the underwater robot platform 5 to achieve six degrees of freedom omnidirectional drive. The control module 13 controls the autonomous underwater robot to complete exploration tasks, including motion control, online intelligent decision-making, dynamic adjustment of exploration tasks, and generation of simplified reports and three-dimensional geological models. The control module 13 also corrects the accumulated error of the navigation and positioning module 6 based on the absolute position provided by the acoustic communication positioning unit 4.

[0033] The navigation and positioning module 6 is the foundation for the AUV's autonomous navigation and precise control. Located within the underwater robot platform 5 at the bow of the AUV, the data it collects or calculates is transmitted to the control module 13 via a data cable. Specifically, it includes: a strapdown inertial navigation system, used to calculate dead reckoning by measuring the AUV's own angular velocity and acceleration, outputting the AUV's calculated position, velocity, and attitude information at high frequency; a depth gauge, used to measure the AUV's real-time operating depth; and an altimeter, used to measure the real-time distance (height above the bottom) between the AUV and the seabed directly below, enabling altitude-holding cruise and seabed control.

[0034] The buoyancy adjustment module 8 includes a hydraulic pump, an oil bladder, and a pressure chamber. The pressure chamber is installed inside the underwater robot platform 5, and the oil bladder is located on the lower surface of the underwater robot platform 5. The hydraulic pump is connected to an oil pipe, with both ends of the oil pipe connected to the oil bladder and the pressure chamber, respectively. The AUV uses the hydraulic pump and oil pipe to transfer hydraulic oil bidirectionally between the internal pressure chamber and the oil bladder to adjust the displacement. This buoyancy adjustment module 8 precisely controls the buoyancy state of the AUV through the transfer of hydraulic fluid between the pressure chamber and the oil bladder, providing buoyancy assistance for diving to the bottom, testing operations, and surfacing for recovery. Especially when used in conjunction with the propulsion module, it can effectively reduce propulsion energy consumption and extend the AUV's underwater operating time.

[0035] The propulsion module includes two main thrusters 9 and four vertical thrusters. The two main thrusters 9 are located at the stern of the underwater robot platform 5, while the two vertical thrusters 10 are located at the front of the underwater robot platform 5. Vertical thrusters 11 and 12 are located in the middle of the underwater robot platform 5, and the two vertical thrusters 11 and 12 located in the middle of the underwater robot platform 5 are tilted to the left and right at preset angles with the vertical plane as the center line. During navigation, the two main thrusters 9 at the stern achieve horizontal movement through a differential control strategy. When rotating forward at the same speed, they propel the underwater robot platform 5 forward, and when rotating backward at the same speed, they achieve backward movement. When the two main thrusters 9 generate a speed difference, they generate a steering torque around the vertical axis, enabling left or right turns. At the same time, the four vertical thrusters achieve vertical and attitude adjustments through coordinated control. The four thrusters rotate forward synchronously to provide overall upward thrust and rotate backward synchronously to provide downward thrust. The two thrusters at the front and the two thrusters in the middle work differentially (e.g., forward rotation at the front and reverse rotation at the middle) to generate a pitching torque around the horizontal axis to adjust the pitch angle to adapt to the seabed slope terrain. The two thrusters on the left and the two thrusters on the right work differentially to generate a rolling torque around the longitudinal axis to keep the platform level. The two vertical thrusters 11 and 12 located in the middle of the underwater robot platform 5 are tilted to the left and right sides at a preset angle (preferably 20°) with the vertical plane as the center line. When the two thrusters perform differential motion (such as the left rear thruster increasing thrust while the right rear thruster decreases thrust), the thrust vector generated by their tilted arrangement forms a lateral component in the horizontal direction. The superposition of this component generates lateral thrust, enabling the underwater robot platform 5 to achieve lateral translation without changing its heading, which greatly improves the maneuverability and control flexibility in narrow areas or precise positioning.

[0036] The control module 13 is installed inside the underwater robot platform 5. It communicates with the suction anchor unit 1, CPT detection unit 2, shallow sea profile detection unit 3, acoustic communication and positioning unit 4, navigation and positioning module 6, energy module 7, buoyancy adjustment module 8 and power propulsion module through a data cable. It also stores the data collected and calculated during the detection through the built-in data storage area.

[0037] The control module 13 adopts a hierarchical control architecture for controlling the propulsion module, including an upper motion control layer and a lower thrust distribution layer.

[0038] At the motion control layer, the control module 13 compares the calculated position, attitude, speed, and heading information of the underwater robot platform 5, which is fed back in real time by the navigation and positioning module 6, with the operator's preset desired motion state (including desired speed, desired heading, desired depth, and desired attitude angle) and calculates the deviation. Based on this, in a coordinate system with the AUV's center of gravity as the origin, the control module 13 calls the built-in motion control algorithm (preferably an incremental digital PID control algorithm) to solve for the desired control force and desired control torque required to make the underwater robot platform 5 approach the desired motion state, including the desired thrust component along the three coordinate axes and the desired torque component around the three coordinate axes.

[0039] The motion control algorithm is preferably an incremental digital PID control algorithm. The proportional, integral, and derivative coefficients for horizontal heading control are preferably 5.0–15.0, 0.1–1.0, and 0.5–3.0, respectively. The proportional, integral, and derivative coefficients for depth and altitude control are preferably 8.0–20.0, 0.2–2.0, and 1.0–5.0, respectively. The proportional, integral, and derivative coefficients for attitude control channels (roll and pitch) are preferably 10.0–25.0, 0.5–2.5, and 2.0–6.0, respectively.

[0040] In the thrust distribution layer, the control module 13 establishes a mapping matrix (also known as the thrust distribution matrix) from the thruster thrust to the force and torque on the underwater robot platform 5 based on the installation position, installation angle, and thrust direction of each thruster. Taking the desired control force and desired control torque output from the motion control layer as input, and combining it with the thrust distribution matrix, the built-in thrust distribution algorithm (preferably a pseudo-inverse-based thrust distribution algorithm, such as Moore-Penrose pseudo-inverse solution) is called to distribute the desired control force and desired control torque to each thruster in real time, generating speed commands or thrust commands for each thruster. The commands drive the brushless DC motors of each thruster through power amplifiers, so that each thruster outputs the corresponding thrust according to the command.

[0041] The preferred thrust allocation algorithm is a weighted pseudo-inverse solution (an extension of the ordinary Moore-Penrose pseudo-inverse), with the objective function and constraints as follows:

[0042]

[0043] in, Let be the thrust command vector for each thruster, where the i-th element represents the output thrust of the i-th thruster, and T is the transpose operation. It is a positive definite diagonal weight matrix. Assign a matrix to the thrust. Let be the desired control force and desired control torque vector of the underwater robot platform 5. The diagonal elements are determined based on the energy efficiency of the thrusters. The weight coefficient of the two main thrusters at the tail is set to 1.0 as the baseline, the weight coefficient of the two vertical thrusters at the front is set to 1.2 to 1.5, and the weight coefficient of the two inclined vertical thrusters in the middle is set to 1.5 to 2.0. The larger the weight coefficient, the lower the priority of the thruster in the allocation, so that the thrusters with lower energy consumption are used first to extend the underwater endurance of the AUV.

[0044] After the thrust is distributed, the control module 13 also needs to convert the thrust commands of each thruster into motor speed commands. The conversion is based on the mapping relationship between the thrust and the speed of the thruster.

[0045] in, Let i be the output thrust of the i-th thruster. The thrust coefficient of the i-th propeller, pre-calibrated through the open-water propeller test. The density of seawater, Let be the diameter of the propeller of the i-th thruster. This represents the motor speed corresponding to the i-th thruster. The control module 13 calculates the motor speed of each thruster in real time based on this mapping relationship and drives the operation via an electronic speed controller. Specifically, for the vertical thrusters 11 and 12, their thrust has a fixed geometric decomposition relationship in the vertical and lateral directions, and their vertical thrust components... and lateral thrust component They respectively satisfy:

[0046]

[0047] For the two main thrusters 9, the control module 13 achieves horizontal motion through a differential control strategy: when straight forward or backward movement is required, the same rotational speed command is output to both main thrusters 9; when turning is required, different rotational speed commands are output to the two main thrusters 9, the magnitude of the speed difference determines the turning angular velocity, and the direction of the speed difference determines the turning direction. For the four vertical thrusters, the control module 13 calculates the rotational speed command of each vertical thruster based on the vertical thrust command, pitch torque command, and roll torque command output by the motion control layer through a thrust distribution algorithm; among them, the thrust distribution of the two vertical thrusters 11 and 12 located in the middle of the underwater robot platform 5 must simultaneously meet the vertical force requirement and the lateral force requirement. The control module 13 decomposes the desired thrust into vertical and lateral components based on their tilt angle, which participate in the vertical thrust distribution and lateral thrust distribution respectively.

[0048] The control module 13 controls the navigation and positioning module 6 mainly in three aspects: navigation system initialization, sensor data acquisition and synchronous triggering, and fusion and calculation of multi-source navigation information.

[0049] During the navigation system initialization phase, the control module 13 sends an initialization command to the navigation and positioning module 6 before the AUV is launched. This command includes the initial position coordinates (usually the mother ship's GPS coordinates), the initial attitude angles (obtained through a high-precision attitude reference system), and the initial navigation parameters (including cruising speed, sea clearance, equipment operating parameters, and communication cycle). The navigation and positioning module 6 then completes the initial alignment of the inertial navigation system based on these parameters.

[0050] During the data acquisition and synchronization triggering phase, the control module 13 outputs a synchronization acquisition trigger signal to the navigation and positioning module 6 according to a preset sampling period (preferably 50Hz). After receiving the trigger signal, the navigation and positioning module 6 synchronously acquires the calculated position, attitude, speed, depth and height above the bottom of the underwater robot platform 5, and sends each frame of data back to the control module 13 after adding a unified timestamp.

[0051] In the multi-source navigation information fusion and calculation stage, the control module 13 combines the absolute position measured by the acoustic communication positioning unit 4 with the calculated position of the navigation positioning module 6 itself for navigation calculation. Specifically, the control module 13 corrects the accumulated error of the navigation positioning module 6 based on the absolute position provided by the acoustic communication positioning unit 4. The positioning error of the strapdown inertial navigation system in the navigation positioning module 6 accumulates over time. Therefore, the control module 13 uses the absolute position provided by the acoustic communication positioning unit 4 at a preset period (preferably every 10 to 30 seconds) as an external observation and fuses it with the calculated position at the same time to correct the accumulated drift error of the navigation positioning module 6. This data fusion is achieved by the control module 13 calling a built-in combined navigation filtering algorithm, preferably an extended Kalman filter algorithm. The difference between the absolute position and the calculated position is used as a residual to optimally estimate the position state of the navigation positioning module 6, outputting the precise position information of the underwater robot platform 5. The aforementioned fusion correction process is triggered by the output cycle of the acoustic communication positioning unit 4, performing a position update each time a new absolute position is obtained. Between two corrections, the control module 13 still uses the calculated position of the navigation positioning module 6 as the basis for the current position of the underwater robot platform 5. The state vector of the extended Kalman filter algorithm includes the position, velocity, and attitude angle of the underwater robot platform 5, and the observation vector is the absolute position provided by the acoustic communication positioning unit 4. The filtering process is executed in a two-stage cycle of prediction and update. Between two USBL positioning updates, the control module 13 uses the calculation results of the strapdown inertial navigation system to predict the state. When a new absolute position is obtained, the residual is calculated and the state estimate and its covariance matrix are updated, thereby correcting the cumulative drift error of the navigation positioning module 6. This error correction process is actually a prior art technique.

[0052] The control module 13 controls the buoyancy adjustment module 8, including buoyancy state switching and precise buoyancy adjustment.

[0053] Regarding buoyancy state switching, the control module 13 outputs corresponding control commands to the buoyancy adjustment module 8 according to the needs of the current operation stage: when the AUV needs to dive or sit on the bottom, the hydraulic pump works in the forward direction, drawing hydraulic oil from the oil bladder through the oil pipe and injecting it into the internal pressure tank. The external oil bladder shrinks in volume due to the reduction of oil, and the overall displacement of the AUV decreases accordingly to obtain negative buoyancy. At the same time, it controls the four vertical thrusters to reverse and provide diving thrust (typically 0.3~0.5 times the maximum vertical thrust), so that the underwater robot platform 5 sinks smoothly to the predetermined seabed position; when it needs to surface, the hydraulic pump reverses... During operation, hydraulic oil is pumped from the pressure tank back to the oil bladder via oil pipes. The oil bladder expands in volume due to the injection of oil, and the overall displacement of the AUV increases accordingly to obtain positive buoyancy. At the same time, the four vertical thrusters are controlled to rotate forward to provide upward thrust (typically 0.3 to 0.5 times the maximum vertical thrust), causing the underwater robot platform 5 to float upward. When it is necessary to hover at a certain depth or cruise at a fixed altitude, the control module 13 adjusts the rotation direction and speed of the hydraulic pump to make the buoyancy of the underwater robot platform 5 reach a dynamic balance with its own weight, achieving a state of zero buoyancy or slight positive buoyancy (typically -5 to -20N).

[0054] Regarding precise buoyancy adjustment, the control module 13 uses a closed-loop control algorithm (preferably a PID control algorithm) to precisely adjust buoyancy based on real-time feedback from the depth gauge and altimeter. When the deviation between the actual depth and the target depth exceeds a preset threshold (preferably 15cm) during the dive, the control module 13 automatically adjusts the operating parameters of the hydraulic pump and the four vertical thrusters to correct the depth deviation. When a smooth landing is required during the bottoming process, the control module 13 gradually reduces the pump speed of the hydraulic pump or the motor speed of the four vertical thrusters during the approach to the seabed, so that the underwater robot platform 5 contacts the seabed at a slow speed, avoiding violent impact on the seabed soil.

[0055] After the underwater robot platform 5 sails to the CPT in-situ test point and completes its landing, the control module 13 controls the suction anchor unit 1 in three stages: sealing stage, suction stage, pressure holding stage, and bottom-lifting stage.

[0056] During the sealing phase, control module 13 first sends an opening command to lock valve 15 (energizing it to ensure communication between the inner cavity and external seawater). The sharp edges of the sealing shell, under the weight of the AUV and the diving thrust of the four vertical thrusters (typically 0.2~0.4 times the maximum vertical thrust), cut into the seabed. Then, control module 13 removes the opening command from lock valve 15, and lock valve 15 returns to its normally closed state, isolating the inner cavity of the sealing shell from the external seawater. This ensures that the inner cavity remains sealed in the event of an unexpected power outage, preventing the AUV from accidentally detaching from the seabed due to loss of suction. During the suction phase, control module 13 sends a start command to the high-pressure bidirectional seawater pump and sets it to suction mode. The high-pressure bidirectional seawater pump begins to pump seawater from inside the sealing shell through a continuous... The pressure-resistant pipeline inside the sealed housing is continuously pumped out. During this process, the control module 13 collects the pressure sensor signals inside and outside the sealed housing in real time at a preset sampling frequency (preferably 10Hz) and calculates the pressure difference inside and outside the sealed housing. When the pressure difference inside and outside the sealed housing is not lower than the preset safety threshold (preferably 0.5MPa), it enters the pressure holding stage. During the pressure holding stage, the control module 13 maintains the intermittent operation of the seawater pump to keep the pressure difference within the preset range. After the CPT in-situ test is completed, it enters the bottom-lifting stage. The control module 13 outputs an injection mode command to the high-pressure bidirectional seawater pump and an opening command to the lock valve 15. At this time, seawater can enter the sealed housing to quickly balance the internal and external pressures, release the suction force, and the AUV can easily detach from the seabed.

[0057] After the AUV settles smoothly at the CPT in-situ test point, the control module 13 controls the CPT detection unit 2 in three stages: penetration control, data acquisition control, and pull-out control.

[0058] During the penetration control phase, the control module 13 outputs a forward rotation command to the hollow shaft servo motor to drive the ball screw pair of the electric cylinder to rotate, causing the probe rod to extend and press the CPT probe into the seabed soil. During penetration, the piston rod displacement signal output by the displacement sensor is an analog voltage signal proportional to the iron core displacement. The control module 13 uses a built-in high-precision data acquisition card to sample this analog voltage signal at a high-frequency sampling rate (preferably 100Hz) as discrete time-series voltage data, and converts the voltage at each sampling point into a displacement value in millimeters according to the calibration coefficient of the differential transformer displacement sensor.

[0059] Furthermore, at the start of the CPT in-situ test, the control module 13 monitors the cone tip resistance and sidewall friction feedback from the CPT probe in real time. When the probe is suspended, these two resistance values ​​are close to zero. When the cone tip of the probe contacts and begins to penetrate the seabed soil, the soil resistance causes a significant step increase in the cone tip resistance and sidewall friction. The control module 13 determines this moment as the moment the probe contacts the seabed soil surface and uses the displacement sensor reading at this instant as the zero point. Using the displacement value at the moment the probe contacts the seabed soil surface as the zero point, the current displacement value is calculated as the penetration depth of the CPT probe. Simultaneously, the control module 13 performs differential processing on the penetration depth over time to calculate the penetration speed of the CPT probe in real time. The control module 13 compares the real-time penetration speed with the preset penetration speed (preferably 20 mm / s) through a built-in closed-loop control algorithm (preferably a PID control algorithm) to dynamically adjust the speed of the servo motor, ensuring that the probe penetrates at a constant speed.

[0060] In the data acquisition and control phase, when the probe contacts the seabed soil surface, the control module 13 marks the displacement sensor reading at that moment as the zero point of penetration depth and initiates the CPT data acquisition process. The control module 13 synchronously acquires the signals obtained by the cone tip resistance sensor, pore water pressure sensor, and sidewall friction sensor at a sampling frequency of 100Hz, binding each frame of data with the current penetration depth value and timestamp to obtain the final CPT test data and the corresponding penetration depth and timestamp.

[0061] In the extraction control stage, when the penetration depth reaches the preset target depth (preferably 3~15m), the control module 13 outputs a reverse command to the hollow shaft servo motor, so that the probe rod is pulled out of the soil at a uniform speed (preferably not exceeding 50mm / s).

[0062] The control module 13 controls the shallow subsurface profiling unit 3 through three stages: parameter configuration, transmission triggering, and data reception. In the parameter configuration stage, the control module 13 writes the preset equipment operating parameters from the mission instruction package issued by the mother ship into the configuration register of the shallow subsurface profiling unit 3 via a data cable, thus setting the working mode of the shallow subsurface profiling unit 3. In the transmission triggering stage, when the underwater robot platform 5 is in a constant altitude cruise mode and its attitude is stable (preferably with both roll and pitch angles less than 5°), the control module 13 outputs a synchronous trigger signal to the shallow subsurface profiling unit 3, triggering it to continuously transmit acoustic signals at a set transmission rate. In the data reception stage, the shallow subsurface profiling unit 3 amplifies and converts the received echo signals before transmitting them to the control module 13 via a data cable. The control module 13 packages and fuses each echo signal frame with the calculated position and timestamp provided by the navigation and positioning module 6 to form an acoustic profile data frame with precise spatial attributes.

[0063] The control module 13 controls the acoustic communication positioning unit 4 through two independent channels: communication control and positioning control.

[0064] In the communication control channel, the control module 13 triggers the underwater acoustic communication unit 4 to enter the transmission state periodically according to a preset communication cycle (preferably once every 30 to 60 minutes). In the underwater acoustic communication uplink, the control module 13 packages information such as simplified reports, CPT test data, and depth, and after FEC encoding, MPSK modulation, and power amplification, converts it into an acoustic signal through the transducer array and transmits it to the surface mother ship. In the downlink, the transducer array receives the acoustic command signal sent by the mother ship, and after pre-amplification, filtering, demodulation, and decoding, restores it to a control command and transmits it to the AUV's control module 13 for execution. The operating frequency band of the acoustic communication positioning unit 4 is preferably 10kHz to 30kHz. Within this frequency band, the communication rate and modulation parameters can be adaptively switched according to real-time underwater acoustic channel conditions (such as signal-to-noise ratio, multipath interference level, etc.). Under typical marine environmental conditions, its effective communication distance can reach more than 6 kilometers, and the data transmission rate can reach up to 1000bps.

[0065] In the positioning control channel, the control module 13 triggers the USBL positioning process according to a preset positioning update cycle (preferably once every 10-30 seconds), and this process is completed collaboratively by the mother ship-side equipment and the AUV-side equipment. The mother ship is equipped with a USBL acoustic beacon and a high-precision attitude reference system. The USBL acoustic beacon includes a transmitting transducer and a receiving array, and the high-precision attitude reference system is used to provide the mother ship's own heading, roll, and pitch attitude data. The AUV-side receives the acoustic positioning signal transmitted by the mother ship's USBL acoustic beacon through its transducer array. During the positioning process, the mother ship's USBL acoustic beacon transmits an acoustic interrogation signal to the AUV. The USBL receiving array at the AUV-side measures the phase difference of the acoustic interrogation signal reaching different hydrophone elements in the array, and calculates the distance and bearing of the AUV relative to the mother ship by combining this with the speed of sound propagation in water. The mother ship simultaneously transmits its own high-precision GPS coordinates (as the absolute position reference in the geodetic coordinate system) and hull attitude data to the AUV via a downlink communication link. The AUV's control module 13 fuses the relative distance and bearing measured by the USBL with the mother ship's GPS coordinates and attitude data to obtain the AUV's precise position in the geodetic coordinate system. This precise position is then sent to the navigation and positioning module 6 for periodic correction of the accumulated drift error of the strapdown inertial navigation system. Considering that phase difference measurement, distance / bearing calculation, coordinate system transformation, and the fusion of the relative distance and bearing measured by the USBL with the mother ship's GPS coordinates and attitude data are all standard techniques of the USBL underwater acoustic positioning system, the specific calculation process will not be described in detail here.

[0066] S12. Set the operating parameters of the autonomous underwater robot, including cruising speed, sea clearance, equipment operating parameters, and communication cycle.

[0067] Specifically, in this embodiment, after completing the spatial planning in step S11, the operator further sets the operating parameters of the AUV. These parameters include cruising speed, sea clearance in constant altitude cruising mode, equipment operating parameters, and communication cycle with the mother ship. This ensures that the AUV can stably collect data and maintain effective information exchange with the mother ship during operation. The equipment operating parameters mainly refer to the operating parameters of the shallow subsurface profiling unit 3, such as the primary frequency, difference frequency, pulse length, and transmission rate.

[0068] More specifically, the cruising speed is preferably 2–4 knots; the seabed clearance is preferably 5–15 meters, with the specific values ​​set by the operator based on the seabed topography and the effective detection range of the shallow seismic profiling unit; the communication cycle is preferably every 30–60 minutes for acoustic communication interaction to ensure that the AUV can stably collect data and maintain effective information exchange with the mother ship during operation; the primary frequency of the shallow seismic profiling unit 3 is preferably 85–115 kHz, the differential frequency is preferably 5–25 kHz, the pulse length is preferably 0.05–1 ms, and the transmission rate is not less than 20 ping / s. The operating parameters of the shallow seismic profiling unit 3 can be adaptively adjusted within a preset range according to the seabed type of the target sea area and the expected detection depth. For example, for areas dominated by soft sediments, the differential frequency can be appropriately reduced to increase the penetration depth; for hard seabeds or scenarios requiring higher resolution detection, the differential frequency can be increased to obtain finer stratigraphic imaging.

[0069] S13. The cruise area, the survey line, the CPT in-situ test point, and the working parameters are encapsulated into a mission instruction package and sent to the autonomous underwater robot.

[0070] Specifically, in this embodiment, the cruise area boundary, survey line numbers and coordinate sequences, preset CPT measurement point locations, and all navigation parameters are finally encapsulated into a structured mission instruction package. This mission instruction package employs a layered, nested data structure. The top layer is the mission header (containing metadata such as mission number and timestamp), the middle layer is the voyage planning segment (containing the latitude and longitude coordinate sequence of the cruise area boundary, the start and end coordinates of each survey line and survey line number, and the coordinates of the CPT in-situ test points), and the bottom layer is the navigation parameter segment. Each data segment is separated and verified by a specific frame header identifier. After the mission instruction package is encapsulated, it is sent to the standby AUV via the acoustic communication positioning unit 4.

[0071] S14. The autonomous underwater robot receives and parses the mission instruction packet, thereby completing the initialization of the exploration mission.

[0072] Specifically, in this embodiment, the AUV receives the mission instruction packet through the acoustic communication positioning unit 4 and uses the control module 13 to parse the mission instruction packet to complete the initialization of the detection mission.

[0073] S2. The autonomous underwater robot performs in-situ seabed testing and geological structure exploration according to the exploration mission.

[0074] Step S2 specifically includes the following steps: S21. The autonomous underwater robot performs a fixed-altitude cruise along the survey line and continuously collects acoustic profile data of the shallow seabed strata structure, thereby extracting acoustic strata information.

[0075] Specifically, in this embodiment, during constant altitude cruise mode, the control module 13 first adjusts the AUV to a state of zero buoyancy or slight positive buoyancy via the buoyancy adjustment module 8, balancing the AUV's own weight and buoyancy. Based on this, altitude control during constant altitude cruise is entirely handled by the vertical thrusters: the control module 13 calculates the required diving thrust in real time using a PID control algorithm based on the deviation between the measured altitude from the altimeter and the preset altitude, and converts this diving thrust into rotational speed commands for each vertical thruster using a thrust distribution algorithm. The buoyancy adjustment module 8 maintains a constant fuel level during constant altitude cruise. During this process, the two main thrusters 9 drive the AUV forward at a preset cruise speed.

[0076] During constant-altitude cruise, the shallow-sea profiling unit 3 continuously operates, emitting acoustic signals towards the seabed and receiving echoes. The received echo signals are pre-amplified and converted from analog to digital before being transmitted to the control module 13 via a data cable. The control module 13 packages and fuses each echo signal frame with the calculated position and timestamp provided by the navigation and positioning module 6, forming an acoustic profile data frame with precise spatial attributes. Based on this, the control module 13 performs time-varying gain compensation on the acoustic profile data frame to compensate for the spherical diffusion loss and medium absorption attenuation caused by sound waves propagating in seawater and strata, restoring the true amplitude of the reflected signals from strata at different depths. When implementing time-varying gain compensation, the preset gain curve satisfies:

[0077] in, This is the amplified acoustic profile data. For the two-way travel time of sound waves, This represents the initial gain coefficient for the shallow layer. The medium absorption attenuation coefficient can be adjusted according to the sound velocity and geological characteristics of the sea area being probed.

[0078] After completing time-varying gain compensation, control module 13 uses an automatic interface tracking algorithm to extract formation interface information. This algorithm uses the waveform similarity between two adjacent acoustic profile data as the core criterion, specifically employing a normalized cross-correlation algorithm to calculate the similarity: First, a local waveform window of 21 sampling points in length is extracted, centered on the target sampling point of the current channel. Simultaneously, a reference waveform window of the same length is extracted at the corresponding time position of the previous acoustic profile data. The waveform data within the two windows are then substituted into the normalized cross-correlation formula to calculate the cross-correlation coefficient. The calculation formula is as follows:

[0079] in, For cross-correlation coefficients, This represents the total number of sampling points within the local waveform window. The amplitude of the i-th sampling point within the current local waveform window. This represents the amplitude of the i-th sampling point within the previous local waveform window. and These are the average values ​​of the sampling points within the two local waveform windows, respectively.

[0080] The cross-correlation coefficient between the current acoustic profile and the previous profile is calculated for each trace. When the cross-correlation coefficient exceeds a preset threshold of 0.7, it is determined to be a continuation of the same continuous reflection interface. Based on this, each reflection phase axis is continuously tracked and marked on the time axis, and the reflection travel time corresponding to each phase axis is recorded synchronously. Next, the stratigraphic interface is identified, and the specific identification conditions are as follows: (1) If the normalized cross-correlation coefficients of three consecutive adjacent acoustic profile data are all stably greater than 0.7, forming a continuous in-phase axis trajectory without discontinuities, then the noise interference of a single channel that occasionally meets the standard can be eliminated; (2) The reflection intensity of all sampling points on the in-phase axis is more than 3dB higher than the average amplitude of the surrounding background noise, satisfying the effective reflection characteristics caused by the difference in acoustic impedance of different strata media. If both of the above conditions are met, it can be determined that an effective strata interface has been successfully identified. After the effective strata interface is identified, the average acoustic velocity of the strata in the cruise area obtained in advance through borehole calibration is substituted into the standardized time-depth conversion formula to complete the depth calculation of the strata interface, and the strata thickness is calculated using the depth of adjacent strata interfaces. Then, the strata interfaces are numbered sequentially from the seabed surface downwards, and the navigation and positioning module 6 provides the estimated position (the cumulative error has been corrected). Finally, acoustic strata information including coordinate position, strata number, and strata interface depth is obtained.

[0081] In addition, for signal interruptions caused by noise or missing strata, the algorithm sets the maximum number of interrupted channels to 5: when the interruption length does not exceed 4 channels, linear interpolation is used to fill the interruption with the reflection travel time data of adjacent valid channels; when the interruption length is not less than 5 channels, it is determined to be a real erosion interface of the strata, and the tracking of the same phase axis of that segment is terminated to ensure the continuity of the interface and avoid generating false interfaces that do not conform to geological laws.

[0082] S22. Upon reaching the CPT in-situ test point, the autonomous underwater robot sits on the seabed and performs the CPT in-situ test to obtain CPT test data, thereby acquiring measured stratigraphic information of the shallow strata structure below the seabed.

[0083] Specifically, in this embodiment, when the AUV travels along the survey line to the vicinity of the preset CPT in-situ test point, the control module 13 adjusts the thrust of the main thruster 9 and the vertical thruster to make the AUV hover and position itself directly above the target point. After hovering and positioning, the control module 13 controls the AUV to sit on the seabed and attaches it to the seabed through the suction anchor unit 1. Then, it controls the CPT detection unit 2 to perform CPT in-situ testing, obtaining CPT test data including the cone tip resistance, sidewall friction resistance, and excess pore water pressure when the CPT probe penetrates the seabed soil.

[0084] Furthermore, for any sampling point, the corrected cone tip resistance and friction ratio are calculated based on the CPT test data. These calculated corrected cone tip resistance and friction ratio are then projected onto the Robertson classification map to obtain the formation category corresponding to the penetration depth of that sampling point. The corrected cone tip resistance and friction ratio satisfy the following relationships:

[0085]

[0086] in, To correct the cone tip resistance, For cone tip resistance, The pressure of the superstatic pore water. This refers to the probe area ratio. The value is usually 0.8. The friction ratio is... This represents the sidewall friction resistance.

[0087] After determining the stratigraphic category at each sampling point, the control module 13 summarizes the stratigraphic category determination results at different depths to form a stratigraphic column chart describing the stratigraphic distribution and categories. When the stratigraphic category determination results of adjacent depth points change, the control module 13 marks that depth point as a stratigraphic interface and calculates the stratigraphic thickness using the depth of the adjacent stratigraphic interface. Then, the stratigraphic layers are numbered sequentially downwards from the seabed surface. Combined with the estimated position provided by the navigation and positioning module 6, the measured stratigraphic information, including coordinate position, stratigraphic number, stratigraphic interface depth, and stratigraphic thickness, can be obtained.

[0088] S23. After completing the CPT in-situ test, the autonomous underwater robot detaches from the seabed and continues to navigate along the survey line.

[0089] Specifically, in this embodiment, after the CPT probe penetrates to the preset target depth, the control module 13 controls the probe rod to retract. After the probe rod is fully retracted, the control module 13 outputs an injection mode command to the high-pressure bidirectional seawater pump and an opening command to the lock valve 15, thereby releasing the suction force and allowing the AUV to easily detach from the seabed.

[0090] After the adsorption force is released, control module 13 controls the hydraulic pump to pump hydraulic oil from the internal pressure tank back to the external oil bladder. The external oil bladder expands in volume, increasing the displacement and giving the AUV positive buoyancy. At the same time, the four vertical thrusters rotate synchronously in the forward direction, providing initial upward lift, allowing the AUV to smoothly and vertically detach from the seabed. Control module 13 continuously monitors the altimeter readings to confirm that the AUV has completely detached from the seabed and switches the AUV back to altitude-hold cruise mode to continue navigation along the survey line.

[0091] S3. When performing the exploration mission, the autonomous underwater robot makes online intelligent decisions based on real-time exploration results, dynamically adjusts the exploration mission when geological anomalies and significant stratigraphic extensions occur, and periodically generates concise reports and transmits them to the mother ship.

[0092] Geological anomalies include acoustic geological anomalies and measured geological anomalies. Significant stratigraphic extension refers to a key stratum not ending at the end of the survey line. The online intelligent decision-making refers to determining whether geological anomalies and significant stratigraphic extensions have occurred based on real-time detection results, and dynamically adjusting the detection task when such anomalies or extensions are detected. Specifically, the dynamic adjustment of the detection task includes: when significant stratigraphic extensions occur, extending the survey line and generating new CPT in-situ test points on the extended line segment (see step S31 for details); when geological anomalies occur, generating encrypted detection tasks based on the anomaly type and inserting these tasks into the detection task queue for execution (see step S34 for details).

[0093] Step S3 specifically includes the following steps: S31. Based on the acoustic profile data and the measured stratigraphic information, if a key stratigraphic layer does not end at the endpoint of the survey line, the autonomous underwater robot extends the survey line.

[0094] Specifically, in this embodiment, during the constant altitude cruise, the control module 13 continuously processes the acoustic profile data collected in real time by the shallow subsurface profile detection unit 3, tracks and marks each reflection phase axis one by one, records the reflection travel time and reflection intensity corresponding to each phase axis, and converts the reflection travel time into the subsurface interface depth relative to the seabed to form a subsurface interface depth sequence with geographic coordinates.

[0095] When the AUV travels along the current survey line to a preset distance (preferably 50 to 100 meters) from the end of the survey line, the control module 13 uses the current AUV position as a reference and backtracks to the nearest N acoustic profile data (N is preferably 50 to 100 channels, corresponding to a survey line length of approximately 50 to 100 meters). It extracts the depth sequence and reflection intensity sequence of each reflection phase axis from the N acoustic profile data and calculates the depth change trend curve and reflection intensity change trend curve for each phase axis within the range of the N acoustic profile data. The depth change trend curve is obtained by linearly fitting the depth value of the phase axis in the N channels of data. If the absolute value of its slope is less than a preset threshold (preferably no more than 0.5 meters per 10 channels), the depth of the phase axis is determined to be stable. The reflection intensity change trend is obtained by linearly fitting the reflection intensity value of the phase axis in the N channels of data. If the absolute value of the fitting slope is less than a preset threshold (preferably no more than 3 dB per 10 channels), the reflection intensity of the phase axis is determined to be stable.

[0096] If a certain phase axis simultaneously satisfies both the conditions of stable depth and stable reflection intensity, the control module 13 determines that the phase axis is a key stratigraphic interface with stable continuity, indicating that the corresponding key stratigraphic layer has not ended near the end of the survey line, but continues to extend stably beyond the end of the survey line. Based on this, if the depth of the stratigraphic interface of this key stratigraphic layer is within the target depth range of engineering interest (preferably 5 to 40 meters below the seabed), the control module 13 determines that the survey line extension condition is met.

[0097] After determining that the conditions for extending the survey line are met, control module 13 initiates the survey line extension process. Specifically, control module 13 obtains the coordinates of the design endpoint of the current survey line (i.e., the endpoint of the survey line set in the initial mission plan), and generates an extended survey line segment with this endpoint as the starting point, the direction of the current survey line as the direction, and a preset extension step length (preferably 100 meters) as the length. If extending the current survey line according to the preset extension step length would cause the AUV to navigate outside the cruise area, the survey line will be extended to the boundary of the cruise area at most. In addition, a CPT in-situ test point is generated every 50 meters on the extended survey line segment.

[0098] The starting point of the extended survey line segment is the endpoint of the original survey line, and the ending point is the new endpoint after extending the original survey line by a preset step length. The survey line number of the extended survey line segment is based on the original survey line number with an extension identifier added (for example, if the original survey line number is L1, the extended segment number is L1-E1) to distinguish it from the original survey line. After generating the extended survey line segment, the control module 13 adds the extended survey line segment to the current survey line. After completing the remaining segment of the current survey line, the AUV does not perform a return or turn, but continues to sail directly along the extended survey line segment and performs shallow seismic profiling and CPT in-situ testing. If, when navigating along the extended survey line to its end, the control module 13 detects again that the same key stratigraphic interface still meets the stable continuation condition at the end of the extended survey line, the above extension process is repeated to generate the next extended survey line (numbered L1-E2) until the key stratigraphic interface no longer meets the stable continuation condition, or the cumulative extension distance reaches the preset maximum extension distance (preferably 1000 meters to avoid the AUV consuming too much power and being unable to complete the remaining survey line), or when the AUV reaches the boundary of the cruise area, the survey line extension process is terminated, and the AUV turns to the next survey line according to the original mission plan.

[0099] S32. The autonomous underwater robot determines whether a geological anomaly has occurred based on a preset geological model, the acoustic stratigraphic information, and the measured stratigraphic information.

[0100] Step S32 specifically includes the following steps: S321. The autonomous underwater robot compares the acoustic stratigraphic information with the preset geological model.

[0101] During constant-altitude cruise, the control module 13 compares the real-time extracted acoustic stratigraphic information with the expected stratigraphic information corresponding to the geographical location in the preset geological model layer by layer. The preset geological model is a simplified stratigraphic structure model pre-established by the operator during the operation preparation stage based on historical geological data of the target sea area (including existing borehole data, seismic exploration data, regional geological survey reports, etc.) and stored in the storage area of ​​the control module 13. The preset geological model contains at least the following information: (1) the number of each expected stratigraphic layer, numbered sequentially from the seabed surface downwards as 1, 2, 3, ...; (2) the expected stratigraphic interface depth of each expected stratigraphic interface relative to the seabed surface and its allowable deviation range; (3) the expected thickness of each expected stratigraphic layer and its allowable deviation range. It should be noted that the stratigraphic interface depth mentioned in this embodiment refers to the vertical distance of the corresponding interface relative to the seabed surface.

[0102] The method for establishing the preset geological model is as follows: Operators import existing borehole data (including stratigraphic depths and lithological descriptions of each borehole), regional seismic exploration profile interpretation results, and previous regional geological survey reports obtained in this area into geological modeling software to establish an initial stratigraphic structure model covering the entire cruise area. This model is stored in a grid format, with each grid node containing the expected stratum number, expected stratigraphic interface depth, expected stratum thickness, allowable deviation ranges for the expected stratigraphic interface depth and thickness. When historical geological data for the target sea area is lacking, operators can set a simplified horizontal layered model as the preset geological model based on regional geological background data.

[0103] Specifically, for any given location, the control module 13 first compares the preset stratigraphic layer number at that location with the acoustic stratigraphic information to extract the actual stratigraphic layer number at that location. If the stratigraphic layer number is the same, using the geographic coordinates of the current AUV as an index, it reads the expected stratigraphic interface depth and expected thickness of the top interface of each expected stratigraphic layer at that location from the preset geological model. Simultaneously, it extracts the actual stratigraphic interface depth of each reflection phase axis actually identified at that location (numbered sequentially from the seabed surface downwards as 1, 2, 3, ...) from the acoustic stratigraphic information. For the i-th expected stratigraphic layer, the control module 13 calculates the absolute value of the difference between the actual stratigraphic interface depth and the expected stratigraphic interface depth at its top interface, as well as the absolute value of the difference between the actual thickness and the expected thickness of the layer, and records them as the burial depth deviation and thickness deviation of the layer, respectively.

[0104] S322. When the acoustic profile data at a certain location is inconsistent with the preset geological model, it is determined that the geological anomaly has occurred at that location.

[0105] Specifically, in this embodiment, for any given location, if the preset stratigraphic layer number at that location in the preset geological model differs from the actual stratigraphic layer number extracted from the acoustic stratigraphic information, a geological anomaly is determined to have occurred at that location, specifically defined as an acoustic geological anomaly. Otherwise, the control module 13 performs layer-by-layer determination of the burial depth deviation and thickness deviation, as follows: For each expected stratum, if both of the following conditions are met simultaneously, the stratum is determined to be consistent with the preset geological model: (1) the burial depth deviation does not exceed the preset depth deviation threshold (preferably not exceeding 20% ​​of the expected thickness of the stratum), that is, the burial depth deviation does not exceed the allowable deviation range of the expected stratum interface depth; (2) the thickness deviation does not exceed the preset thickness deviation threshold (preferably not exceeding 30% of the expected thickness of the stratum), that is, the thickness deviation does not exceed the allowable deviation range of the expected thickness. If any of the above deviations of a certain expected stratum exceeds the corresponding preset threshold, the control module 13 determines that an acoustic stratum anomaly has occurred at that location and marks it as a first-class geological anomaly.

[0106] When an acoustic formation anomaly is detected, the control module 13 records the current position of the AUV as the anomaly identification position for subsequent intelligent decision-making.

[0107] S323. Compare the measured stratigraphic information at the CPT in-situ test point with the acoustic stratigraphic information. If the deviation between the two exceeds a preset threshold, it is determined that the geological anomaly has occurred at that location.

[0108] Specifically, in this embodiment, after the AUV completes a CPT in-situ test point and obtains the measured stratigraphic information, the control module 13 extracts the measured stratigraphic information and acoustic stratigraphic information at the test point, and determines whether the stratigraphic layers obtained by the two are the same. If they are different, it is directly determined that the deviation between the two exceeds a preset threshold, and a geological anomaly occurs at this location, which is recorded as a measured geological anomaly; if they are the same, the next step of determination is performed, and the specific determination process is as follows.

[0109] The control module 13 performs layer-by-layer pairing and comparison of the measured stratigraphic information and acoustic stratigraphic information at the CPT in-situ test point. For the i-th stratigraphic layer in the measured stratigraphic information and acoustic stratigraphic information, the absolute value of the difference between the stratigraphic interface depth in the measured stratigraphic information and the stratigraphic interface depth in the acoustic stratigraphic information is calculated and recorded as the measured burial depth deviation. At the same time, the absolute value of the difference between the stratigraphic thickness in the measured stratigraphic information and the stratigraphic thickness in the acoustic stratigraphic information is calculated and recorded as the measured thickness deviation. The control module 13 compares the above deviations with a preset consistency judgment threshold. If the measured burial depth deviation of a certain stratigraphic layer exceeds the preset depth consistency threshold (preferably 0.3 meters), or the measured thickness deviation exceeds the preset thickness consistency threshold (preferably 0.5 meters), the control module 13 determines that the measured stratigraphic information and acoustic stratigraphic information at that location are inconsistent and marks it as a measured geological anomaly.

[0110] When a measured formation anomaly is detected, the control module 13 records the current position of the AUV as the anomaly detection position for subsequent intelligent decision-making.

[0111] S33. If no geological anomaly is found, the autonomous underwater robot continues to perform the original exploration mission.

[0112] S34. If the geological anomaly occurs, the autonomous underwater vehicle generates an encrypted detection task based on the anomaly type and inserts the encrypted detection task into the task queue of the detection task for execution.

[0113] The anomaly types include acoustic geological anomalies and measured geological anomalies. Step S34 specifically includes the following steps: S341. If the geological anomaly is an acoustic geological anomaly, then generate an encrypted survey line parallel to the current survey line, insert it into the task queue of the detection task, and execute it.

[0114] Specifically, in this embodiment, when the control module 13 determines in step S322 that an acoustic geological anomaly has occurred at a certain location, it first determines the continuous distribution range of the anomaly along the current survey line direction. Since the shallow subsurface profiling unit 3 continuously collects data at a fixed transmission rate during constant-altitude cruise, i.e., the time interval between two adjacent acoustic data channels is known, and the cruise speed of the AUV is also known, the control module 13 can accurately calculate the horizontal distance between two adjacent acoustic data channels. for , The time interval between two adjacent acoustic data points. This refers to the cruise speed of the AUV. Assuming the AUV maintains a constant altitude cruise, control module 13 starts counting from the first data channel that detects the anomaly and continues until the last data channel where the anomaly disappears, recording the total number of consecutive data channels showing the occurrence of the acoustic geological anomaly. The length of the anomaly along the current survey line direction is then... for .like If the anomaly is smaller than the preset minimum anomaly scale threshold (preferably 2 meters), it is determined to be accidental noise or a very small-scale geological body, and the encrypted detection task is not triggered; otherwise, it is determined to be a valid geological anomaly, and encrypted survey lines need to be generated for detailed investigation.

[0115] After determining the length of the anomaly along the current survey line, the control module 13 generates a densified survey line. Since the shallow subsurface profiling unit 3 acquires reflected acoustic data incident vertically directly below the AUV, the single-channel data itself lacks left-right resolution, making it impossible to directly determine whether the anomaly is to the left or right of the current survey line. If a densified survey line is deployed on one side only after inferring the anomaly's location based on limited information, an incorrect inference will cause the densified survey line to completely miss the anomaly's location, resulting in densified detection failure. Furthermore, the AUV's underwater communication bandwidth limits its ability to transmit all raw data back to the mother ship for manual assessment in real time; therefore, autonomous decision-making by the AUV is necessary. To fundamentally ensure the effectiveness and reliability of the densified detection, the control module 13 adopts a conservative strategy of deployment on both sides: generating a densified survey line on each side of the current survey line. Both densified survey lines are parallel to the current survey line, located on opposite sides of it, and equidistant from the current survey line. This distance is the densification spacing, preferably 50 meters.

[0116] The coordinates of the two endpoints of the densified survey line can be determined based on the anomaly identification location of the acoustic stratigraphic anomaly. Specifically, since the densified survey line is parallel to the current survey line, when the AUV first obtains the anomaly identification location of the anomaly along the current survey line, this anomaly identification location should also be the projection of one endpoint of the densified survey line onto the current survey line; similarly, when the AUV last obtains the anomaly identification location of the anomaly along the current survey line, this anomaly identification location should be the projection of the other endpoint of the densified survey line onto the current survey line. Since the anomaly identification location and densification interval are known, the coordinates of the two endpoints of the densified survey line are easily obtained. This is essentially a planar coordinate translation problem, which is a current technical method. For simplicity, the specific calculation process for obtaining the coordinates of the two endpoints of the densified survey line will not be explained here.

[0117] If the calculated length of the encrypted survey line is less than the preset minimum encrypted survey line length (preferably 50 meters), it is generated according to the minimum encrypted survey line length; if the encrypted survey line exceeds the boundary of the cruise area, it is truncated to the boundary of the cruise area. After the encrypted survey line is generated, the control module 13 generates CPT in-situ test points on the encrypted survey line at preset intervals (preferably 50 meters), and assigns priorities to the encrypted survey line. If acoustic geological anomalies are detected in multiple discontinuous sections along the same survey line, an encrypted survey line segment is generated for each anomaly section. Multiple encrypted survey line segments can be merged into one encrypted survey line, the length of which covers all encrypted survey line segments.

[0118] For the two encrypted survey lines, the control module 13 designates the encrypted survey line that is far away from the next preset survey line as the first encrypted survey line and assigns it a higher priority, while designating the encrypted survey line that is close to the next preset survey line as the second encrypted survey line and assigns it a lower priority.

[0119] During mission execution, the AUV first travels along the current survey line to its endpoint, completing all detection tasks for that line. Then, the control module 13 calculates the Euclidean distance between the AUV's current position and the coordinates of the two endpoints of the first encrypted survey line, designating the endpoint with the smallest Euclidean distance as the starting point of the first encrypted survey line, and the other endpoint as the endpoint. Next, the AUV turns to the first encrypted survey line, starting from its starting point and traveling along its direction. It then sequentially lands at preset CPT in-situ test points to conduct CPT in-situ tests. Simultaneously, the shallow seismic profiling unit 3 continuously collects acoustic data to obtain stratigraphic structure information for the encrypted survey line area. After completing all detection tasks on the first encrypted survey line, the AUV turns to the second encrypted survey line, again starting detection from the endpoint on the second encrypted survey line closest to its current position. After completing both encrypted survey lines, the AUV's current position is at the endpoint of the second encrypted survey line, which is closest to the starting point of the next preset survey line. The AUV can then continue detection from the starting point of the next preset survey line.

[0120] It is important to emphasize that the objective of the densified survey line is to conduct detailed detection of identified anomalies within a limited area, rather than to track geological regions. Therefore, the survey line extension rules described in step S31 are not applied to the densified survey line. Even if the AUV detects a key stratum at the end of the densified survey line before the end is completed, extension will not be triggered. Furthermore, newly discovered acoustic geological anomalies during the densified survey line detection process will not trigger the generation of a new round of densified survey lines. These restrictions ensure clear task boundaries and controllable operation time for densified detection, preventing the AUV from deviating too far from the main route or consuming excessive power due to nested densification triggered by anomalies, thus ensuring the priority completion of the pre-set survey line tasks.

[0121] The newly generated encrypted survey lines are marked as "encrypted survey line detection". They are inserted into the task queue after the current survey line task and before the next preset survey line task, that is, they are designated as the next survey line that needs to be patrolled by AUV. The patrol order of other preset survey lines is pushed back one position.

[0122] It should be noted that generating a cryptographic survey line on each of the left and right sides, compared to the scheme of inferring the azimuth of one side based on uncertain information before deployment, adds an extra survey line operating distance and the number of CPT test points. However, considering that the endurance of an AUV on a single dive can usually reach tens of kilometers, the extra power consumption of adding a cryptographic survey line is within an acceptable range. This strategy fundamentally avoids the risk of cryptographic detection completely failing due to azimuth inference errors, ensuring the reliability of detection results under complex seabed geological conditions.

[0123] Furthermore, extending the survey line segment does not serve as a trigger for densifying the survey line; that is, newly discovered acoustic geological anomalies on the extended survey line segment do not trigger the generation of a new densified survey line. The execution priority rule for survey line extension tasks and densification survey line tasks is as follows: survey line extension tasks take precedence over densification survey line tasks. That is, when the AUV simultaneously meets the conditions for survey line extension and densification survey line generation along the current survey line, the AUV prioritizes completing all extended survey line segment operations along the current survey line direction (until the extension termination condition is met). After confirming the termination of the extension, it returns from the current position to the starting point of the first densification survey line and sequentially executes all accumulated densification survey line tasks on that survey line.

[0124] S342. If the geological anomaly is a measured geological anomaly, then generate encrypted measuring points around the corresponding CPT in-situ test point, insert them into the task queue of the detection task, and execute them.

[0125] Specifically, in this embodiment, firstly, the control module 13 reads the anomaly identification location corresponding to the measured geological anomaly, and then determines the layout scheme of the densified measuring points based on the anomaly type, with the anomaly identification location as the center.

[0126] More specifically, the control module 13 generates a first-level encrypted measuring point around the anomaly identification location. This first-level encrypted measuring point comprises six points, located at 0°, 60°, 120°, 180°, 240°, and 300° on a circle with a radius of a preset distance (preferably 10 meters) centered on the anomaly identification location, and this circle is parallel to the horizontal plane. Of course, given the known anomaly identification location, the coordinates of the encrypted measuring points on the horizontal plane can be easily calculated.

[0127] After the encrypted test points are generated, the control module 13 assigns priorities to the encrypted test points and inserts them into the task queue. Specifically, firstly, the control module 13 inserts the generated encrypted test points into the task queue after the current CPT in-situ test point and before the next preset CPT in-situ test point, with the first encrypted test point located to the right of the current encrypted test point in a counter-clockwise direction having the highest priority, and the priorities of the remaining encrypted test points decreasing sequentially in a counter-clockwise direction. Then, the control module 13 completes the CPT in-situ test of each encrypted test point in sequence according to its priority.

[0128] At the encrypted measuring points, control module 13 also executes the measured geological anomaly judgment described in step S322. If a measured geological anomaly is detected again at a certain encrypted measuring point, the next level of encrypted measuring points is generated centered on that encrypted measuring point (except for the circumference radius being modified to 5 meters, the other layout methods are the same as the first level), and the next level of encrypted measuring points is inserted after the current encrypted measuring point for execution. To control the total number of tasks, the encryption level does not exceed 2 levels (i.e., at most, the first level of encrypted measuring points are generated around the initial measuring point, and the second level of encrypted measuring points are generated around the first level of encrypted measuring points). No further cascading encryption is performed at the second level of encrypted measuring points, that is, no further generation of the next level of encrypted measuring points is performed at the second level of encrypted measuring points, to avoid the exponential growth of the number of encrypted measuring points leading to exceeding the energy capacity and operation time limit of a single AUV dive. Finally, the AUV will return to the anomaly identification location corresponding to the measured geological anomaly and continue to perform the detection task according to the preset survey line. It should be noted that during the CPT in-situ test of the encrypted measuring points, the process of judging acoustic geological anomalies to generate encrypted survey lines is not triggered.

[0129] S35. The autonomous underwater robot generates a simplified report based on the detection results and transmits it to the mother ship according to the communication cycle.

[0130] Specifically, in this embodiment, after the AUV completes all detection tasks, the control module 13 first reads all detection data of this task from the storage area, including but not limited to: all acoustic profile data collected by the shallow seismic profiling unit 3 and the acoustic stratigraphic information extracted after real-time processing; CPT test data of each CPT in-situ test point and the corresponding measured stratigraphic information; and geological anomaly event logs recorded during the intelligent decision-making process (including anomaly type, anomaly identification location, distance between the densified survey line and the original survey line, coordinates of the densified survey point location, etc.).

[0131] During the AUV's exploration mission, the control module 13 reads newly acquired data from the storage area since the last communication window, and then periodically generates a simplified report according to the communication cycle and transmits it to the mother ship. The simplified report consists of structured data, including at least acoustic stratigraphic information; CPT test data and corresponding measured stratigraphic information for each CPT in-situ test point; geological anomaly event logs recorded during the intelligent decision-making process (including anomaly type, anomaly identification location, distance between the densified survey line and the original survey line, coordinates of the densified survey point, etc.); and the AUV's remaining battery power. Based on this, the control module 13 serializes the simplified report using a protocol buffer format when generating it, ensuring that transmission is completed within one communication cycle of the underwater acoustic communication link.

[0132] S4. After the autonomous underwater vehicle returns to the mother ship, the collected data is exported from the autonomous underwater vehicle, and then a three-dimensional geological model of the cruising area is constructed on the mother ship.

[0133] Specifically, in this embodiment, after the AUV completes all its exploration tasks, it surfaces according to a preset return procedure and is retrieved to the mother ship's deck. The operator connects the AUV to the computer on the mother ship via a deck data interface (preferably an Ethernet watertight connector) and exports all data collected by the AUV from the storage area of ​​the control module 13. This data includes at least all raw acoustic data collected by the shallow seismic profiling unit 3 and the acoustic stratigraphic information extracted after real-time processing, complete CPT test data and measured stratigraphic information for each CPT in-situ test point, position and attitude data (real-time working depth, height above the bottom, etc.) recorded by the navigation and positioning module 6, and geological anomaly event logs recorded during the intelligent decision-making process. After the data export is complete, the operator can use the acoustic stratigraphic information, measured stratigraphic information, and position and attitude data recorded by the navigation and positioning module 6 to construct a three-dimensional stratigraphic model of the cruising area using the layer model method on the mother ship's three-dimensional geological modeling platform (preferably an ArcGIS platform). Building upon this, the CPT test data obtained from each CPT in-situ test point can be further assigned to the stratigraphic volume elements in the 3D stratigraphic model using ordinary kriging interpolation, forming a comprehensive 3D stratigraphic model that combines stratigraphic structure and geotechnical mechanical properties. Considering that the layer modeling process based on the ArcGIS platform is an existing technical means, for simplicity, only a brief description of this process is provided below.

[0134] First, the operators imported all acoustic stratigraphic information into the ArcGIS platform and created a standard stratigraphic sequence template. This template contains all possible stratigraphic interfaces within the patrol area (i.e., the number of stratigraphic interfaces is the maximum number of stratigraphic interfaces in the acoustic stratigraphic information), and numbered them sequentially from shallowest to deepest. If a survey line lacks a specific stratum in the standard stratigraphic sequence template, a zero-thickness layer is assigned to that location in the modeling platform to ensure that all survey lines participate in subsequent modeling within a unified stratigraphic framework.

[0135] Then, within a unified stratigraphic correlation framework, the interface depth data of each stratum in the acoustic stratigraphic information of all survey lines are assigned to the corresponding dataset according to the stratigraphic number. For each stratigraphic interface in the standard stratigraphic sequence template, its stratigraphic interface depth on all survey lines is used as input. The constrained ordinary kriging interpolation method (specifically, logarithmic kriging is used, i.e., the natural logarithm of each strata thickness value is taken first, then ordinary kriging interpolation is performed, and then the thickness value is restored exponentially; if the logarithmic kriging method cannot be calculated due to zero data value, the least squares kriging with non-negative constraints is used instead, which is achieved by adding a non-negative penalty term to the kriging equation system) to generate the initial three-dimensional surface of the stratum, ensuring that the strata thickness at any position in the interpolation result is a non-negative value. When a stratum is marked as having zero thickness at a certain survey line, the interface depth value at that location is taken as the depth at which the bottom surface of the previous stratum and the top surface of the next stratum coincide. This value is used in the interpolation calculation for that stratum. However, the effective influence range of this zero-thickness data point is limited to a circular area with a preset radius (preferably 100 meters) centered on the missing survey line. Beyond this radius, the interpolation weight of the zero-thickness data point decays to zero according to an inverse distance weighting function, ensuring that the stratum thickness far from the missing survey line smoothly transitions to the average thickness of adjacent normal survey lines. By interpolating each stratum in the standard sequence in this way, the initial set of interface surfaces for each stratum is obtained, thus forming the initial three-dimensional stratigraphic model.

[0136] Finally, the stratigraphic interface depths interpreted at the CPT in-situ test points are used as hard constraint points to perform point-by-point correction on the initial 3D stratigraphic model. The correction follows the principle of depth sequence matching, meaning that the i-th stratigraphic interface in the CPT measured stratigraphic information at the same location corresponds to the i-th stratigraphic interface at the corresponding location in the initial 3D stratigraphic model. For stratigraphic interfaces that are not measured in the CPT, they are treated as local thin layers and only participate in the correction within their influence range (preferably a circular area with a radius of 50m centered on the CPT in-situ test point). Beyond this range, the thickness of the thin layer gradually becomes zero, restoring the stratigraphic sequence framework of the initial 3D stratigraphic model. For stratigraphic interfaces not measured by CPT, the corresponding stratigraphic interfaces in the initial 3D stratigraphic model are retained unchanged. For the i-th stratigraphic interface, the deviation between the measured stratigraphic interface depth at the CPT in-situ test point and the depth at that point in the initial 3D stratigraphic model is calculated. Radial basis function interpolation is used to extend the depth deviation values ​​of all CPT in-situ test points into a deviation correction surface for the entire cruise area, which is then superimposed onto the surface of the initial 3D stratigraphic model. After superposition, each grid point is checked to see if the depth of each stratigraphic interface increases downwards relative to the seabed surface. If this is not satisfied, it indicates a sequence inversion at that location. For grid points with sequence inversion, discrete smooth interpolation is used for local correction, ensuring that the depth of each stratigraphic interface increases downwards relative to the seabed surface, thus obtaining the final 3D stratigraphic model.

[0137] It should be noted that in some cases, the actions described in the specification can be performed in different orders and still achieve the desired results. In this embodiment, the order of steps is given only to make the embodiment clearer and easier to explain, and not to limit it.

[0138] In an optional embodiment, please refer to Figure 5 This invention provides an AUV-based in-situ seabed testing and stratigraphic structure collaborative detection system. The system utilizes the AUV-based in-situ seabed testing and stratigraphic structure collaborative detection method provided by this invention. The system includes a mother ship and an autonomous underwater vehicle (AUV). The mother ship is used to delineate the AUV's patrol area and initialize its detection mission. After the AUV returns to the mother ship, the collected data is exported from the AUV, and a three-dimensional stratigraphic model of the patrol area is constructed on the mother ship.

[0139] The autonomous underwater vehicle (AUV) comprises a suction anchor unit, a CPT (Continuous Threat Transmission) unit, a shallow seismic profiling unit, an acoustic communication and positioning unit, and an underwater robot platform. The suction anchor unit is used to attach the AUV to the seabed. The CPT unit is used to perform in-situ CPT testing. The shallow seismic profiling unit is used to acquire acoustic profile data of shallow subsurface geological structures below the seabed. The acoustic communication and positioning unit is used to obtain the absolute position of the AUV and to enable information transmission between the mother ship and the AUV. The underwater robot platform carries the suction anchor unit, the CPT unit, the shallow seismic profiling unit, and the acoustic communication and positioning unit to perform in-situ seabed testing and coordinated geological structure detection. The AUV performs in-situ seabed testing and coordinated geological structure detection according to the detection mission. During the detection mission, online intelligent decision-making is performed based on real-time detection results. The detection mission is dynamically adjusted when geological anomalies or significant stratigraphic extensions are observed, and concise reports are periodically generated and transmitted to the mother ship.

[0140] In summary, this invention has at least the following beneficial effects: This method integrates the shallow seismic profiler and the CPT (Continuous Probe) detection unit onto the same AUV platform, achieving for the first time an integrated collaborative operation of seabed geophysical exploration and in-situ geotechnical testing, ensuring spatiotemporal synchronization and deep fusion of multi-source data; based on the high mobility of the AUV, this method can autonomously complete movement, positioning, bottom testing, and rapid disengagement in a single dive, achieving continuous, multi-point, and efficient in-situ penetration, completely changing the traditional single-point static operation mode of CPT; employing a flat underwater robot platform design combined with negative buoyancy bottoming and suction anchor adsorption technology, while maintaining good underwater mobility, it can provide a stable and reliable CPT penetration method. Based on the reaction force, it adapts to complex seabed topography; the AUV has intelligent online decision-making and adaptive mission planning capabilities, and can dynamically identify geological anomalies, optimize the detection plan, and autonomously supplement CPT measurement points based on real-time collected shallow seismic profile data and CPT test data, realizing the transformation from pre-set exploration to adaptive detection; it can perform real-time processing and geotechnical parameter interpretation of raw CPT data at the AUV end, and automatically extract key geological conclusions, effectively addressing the challenges of underwater large-scale data processing; through the generation of simplified reports, FEC encoding, MPSK modulation, and power amplification, this method achieves reliable and efficient transmission of key data and commands in low-bandwidth underwater acoustic channels, ensuring real-time linkage between underwater operations and surface command.

[0141] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for coordinated in-situ seabed testing and stratigraphic structure detection based on AUV, characterized in that, Includes the following steps: The autonomous underwater vehicle (AUV) is designated as a patrol area on the mother ship, and its exploration tasks are then configured. The autonomous underwater robot includes a suction anchor unit, a CPT detection unit, a shallow subsurface profiling unit, an acoustic communication and positioning unit, and an underwater robot platform; The suction anchor unit is used to attach the autonomous underwater robot to the seabed. The suction anchor unit is a device that provides a huge reaction force for CPT penetration testing. It consists of a sealed shell, a high-pressure bidirectional seawater pump, a lock valve, and a pressure sensor. The CPT detection unit is used to perform in-situ CPT testing; The shallow seismic profiling unit is used to acquire acoustic profile data of shallow seismic structures below the seabed. The acoustic communication and positioning unit is used to obtain the absolute position of the autonomous underwater robot and to realize information transmission between the mother ship and the autonomous underwater robot. The underwater robot platform is used to carry the suction anchor unit, the CPT detection unit, the shallow seismic profiling unit and the acoustic communication and positioning unit to conduct in-situ seabed testing and collaborative exploration of the geological structure. The autonomous underwater robot cruises at a fixed altitude along the survey line and continuously collects acoustic profile data of the shallow seabed strata structure, thereby extracting acoustic strata information. Upon reaching the CPT in-situ test point, the autonomous underwater robot sits on the seabed and conducts the CPT in-situ test to obtain CPT test data, thereby acquiring measured stratigraphic information on the shallow subsurface structure below the seabed. After completing the CPT in-situ test, the autonomous underwater robot detaches from the seabed and continues to navigate along the survey line; If a key stratum does not end at the end of the survey line, the autonomous underwater robot extends the survey line based on the acoustic profile data and the measured stratum information. The autonomous underwater robot compares the acoustic stratigraphic information with a preset geological model; When the acoustic profile data at a certain location is inconsistent with the preset geological model, it is determined that a geological anomaly has occurred at that location; The measured stratigraphic information at the CPT in-situ test point is compared with the acoustic stratigraphic information. If the deviation between the two exceeds a preset threshold, the geological anomaly at that location is determined to have occurred. Geological anomalies include acoustic geological anomalies and measured geological anomalies; After the autonomous underwater vehicle (AUV) completes a CPT in-situ test point and obtains measured stratigraphic information, it extracts the measured stratigraphic information and acoustic stratigraphic information at that CPT in-situ test point and determines whether the stratigraphic layers obtained from the two are the same. If they are different, it is directly determined that the deviation between the two exceeds a preset threshold, indicating a geological anomaly at that location, and this is recorded as a measured geological anomaly. If they are the same, the measured stratigraphic information and acoustic stratigraphic information at the CPT in-situ test point are compared layer by layer. For the i-th stratigraphic layer in the measured stratigraphic information and acoustic stratigraphic information... For each layer, the absolute value of the difference between the stratigraphic interface depth in the measured stratigraphic information and the stratigraphic interface depth in the acoustic stratigraphic information is calculated and recorded as the measured burial depth deviation. At the same time, the absolute value of the difference between the stratigraphic thickness in the measured stratigraphic information and the stratigraphic thickness in the acoustic stratigraphic information is calculated and recorded as the measured thickness deviation. If the measured burial depth deviation of a stratigraphic layer exceeds a preset depth consistency threshold, or the measured thickness deviation exceeds a preset thickness consistency threshold, then the measured stratigraphic information and the acoustic stratigraphic information at that location are determined to be inconsistent and marked as a measured geological anomaly. If the geological anomaly is an acoustic geological anomaly, then an encrypted survey line parallel to the current survey line is generated, inserted into the task queue of the detection task, and executed. When acoustic geological anomalies are detected, the control module calculates the horizontal spacing between two adjacent acoustic data streams. for , The time interval between two adjacent acoustic data points. The control module, which controls the AUV's cruise speed, starts counting from the first data track detected by the anomaly and continues until the last data track where the anomaly disappears, recording the total number of consecutive data tracks showing the occurrence of acoustic geological anomalies. The length of the anomaly along the current survey line direction is then... for ,like If the anomaly scale is smaller than the preset minimum anomaly scale threshold, it is determined to be accidental noise or a very small-scale geological body and will not trigger a densified detection task; otherwise, it is determined to be a valid geological anomaly and densified survey lines need to be generated for detailed investigation. If the geological anomaly is a measured geological anomaly, then encrypted measuring points are generated around the corresponding CPT in-situ test point, inserted into the task queue of the detection task, and executed. If the geological anomaly occurs, the autonomous underwater vehicle generates an encrypted detection task based on the anomaly type and inserts the encrypted detection task into the task queue of the detection task for execution. The autonomous underwater robot generates a concise report based on the detection results and transmits it to the mother ship according to the communication cycle. After the autonomous underwater vehicle returns to the mother ship, the collected data is exported from the autonomous underwater vehicle and then used to construct a three-dimensional geological model of the cruising area on the mother ship.

2. The method for coordinated detection of seabed in-situ testing and stratigraphic structure based on AUV according to claim 1, characterized in that, The underwater robot platform includes: The navigation and positioning module is used to acquire the calculated position, attitude, speed, depth and height above the bottom of the underwater robot platform in real time. An energy module, which provides electrical power to the underwater robot platform; A buoyancy adjustment module, which is used to control the diving and surfacing of the underwater robot platform; A power propulsion module, which is used to realize the six-degree-of-freedom omnidirectional drive of the underwater robot platform; The control module is used to control the autonomous underwater robot to complete the exploration task, including motion control, online intelligent decision-making, dynamic adjustment of the exploration task, and data storage. The control module is also used to correct the cumulative error of the navigation and positioning module based on the absolute position provided by the acoustic communication and positioning unit.

3. The method for coordinated detection of seabed in-situ testing and stratigraphic structure based on AUV according to claim 1, characterized in that, The process of defining the patrol area of ​​the autonomous underwater vehicle (AUV) on the mother ship and then configuring the AUV's detection tasks includes the following steps: The autonomous underwater vehicle's cruising area is delineated on the mother ship's electronic chart, and survey lines and CPT in-situ test points are preset within the cruising area. The operating parameters of the autonomous underwater robot are set, including cruising speed, sea clearance, equipment operating parameters, and communication cycle. The cruise area, the survey line, the CPT in-situ test point, and the working parameters are encapsulated into a mission instruction package and sent to the autonomous underwater robot. The autonomous underwater robot receives and parses the mission instruction packet, thereby completing the initialization of the exploration mission.

4. The method for coordinated detection of seabed in-situ testing and stratigraphic structure based on AUV according to claim 3, characterized in that: The CPT test data includes the cone tip resistance, sidewall friction resistance, and excess pore water pressure when the CPT probe penetrates the seabed soil.

5. A system for in-situ seabed testing and coordinated detection of stratigraphic structure based on an AUV, wherein the system uses the method for in-situ seabed testing and coordinated detection of stratigraphic structure based on an AUV as described in any one of claims 1-4, characterized in that... include: The mother ship is used to delineate the cruising area of ​​the autonomous underwater vehicle and then initialize the exploration mission of the autonomous underwater vehicle. After the autonomous underwater vehicle returns to the mother ship, the collected data is exported from the autonomous underwater vehicle and then a three-dimensional geological model of the cruising area is constructed on the mother ship. An autonomous underwater vehicle (AUV) comprises a suction anchor unit, a CPT (Cyclic Subsurface Profiling) unit, a shallow subsurface profiling unit, an acoustic communication and positioning unit, and an underwater robot platform. The suction anchor unit is used to attach the AUV to the seabed and provides a strong reaction force for CPT penetration testing; it consists of a sealed housing, a high-pressure bidirectional seawater pump, a locking valve, and a pressure sensor. The CPT unit performs in-situ CPT testing. The shallow subsurface profiling unit acquires acoustic profile data of the shallow subsurface structure below the seabed. The acoustic communication and positioning unit obtains the absolute position of the AUV and enables information transmission between the mother ship and the AUV. The underwater robot platform carries the suction anchor unit, the CPT unit, the shallow subsurface profiling unit, and the acoustic communication and positioning unit. The system employs an autonomous underwater vehicle (AUV) to conduct in-situ seabed testing and coordinated exploration of geological structures. The AUV cruises along the survey line at a fixed altitude, continuously collecting acoustic profile data of the shallow seabed strata to extract acoustic stratigraphic information. Upon reaching a CPT (Continuous Probe Testing) point, the AUV lands and performs CPT testing to obtain CPT data, thereby acquiring measured stratigraphic information of the shallow seabed. After completing the CPT testing, the AUV detaches from the seabed and continues navigating along the survey line. Based on the acoustic profile data and measured stratigraphic information, if a key stratum does not end at the survey line's endpoint, the AUV extends the survey line. The AUV compares the acoustic stratigraphic information with a preset geological model. When the acoustic profile data at a certain location is inconsistent with the preset geological model, a geological anomaly is determined at that location. The measured stratigraphic information at the CPT in-situ test point is compared with the acoustic stratigraphic information. If the deviation between the two exceeds a preset threshold, the geological anomaly at that location is determined to have occurred. Geological anomalies include acoustic geological anomalies and measured geological anomalies; After the autonomous underwater vehicle (AUV) completes a CPT in-situ test point and obtains measured stratigraphic information, it extracts the measured stratigraphic information and acoustic stratigraphic information at that CPT in-situ test point and determines whether the stratigraphic layers obtained from the two are the same. If they are different, it is directly determined that the deviation between the two exceeds a preset threshold, indicating a geological anomaly at that location, and this is recorded as a measured geological anomaly. If they are the same, the measured stratigraphic information and acoustic stratigraphic information at the CPT in-situ test point are compared layer by layer. For the i-th stratigraphic layer in the measured stratigraphic information and acoustic stratigraphic information... For each layer, the absolute value of the difference between the stratigraphic interface depth in the measured stratigraphic information and the stratigraphic interface depth in the acoustic stratigraphic information is calculated and recorded as the measured burial depth deviation. At the same time, the absolute value of the difference between the stratigraphic thickness in the measured stratigraphic information and the stratigraphic thickness in the acoustic stratigraphic information is calculated and recorded as the measured thickness deviation. If the measured burial depth deviation of a stratigraphic layer exceeds a preset depth consistency threshold, or the measured thickness deviation exceeds a preset thickness consistency threshold, then the measured stratigraphic information and the acoustic stratigraphic information at that location are determined to be inconsistent and marked as a measured geological anomaly. If the geological anomaly is an acoustic geological anomaly, then an encrypted survey line parallel to the current survey line is generated, inserted into the task queue of the detection task, and executed. When acoustic geological anomalies are detected, the control module calculates the horizontal spacing between two adjacent acoustic data streams. for , The time interval between two adjacent acoustic data points. The control module, which controls the AUV's cruise speed, starts counting from the first data track detected by the anomaly and continues until the last data track where the anomaly disappears, recording the total number of consecutive data tracks showing the occurrence of acoustic geological anomalies. The length of the anomaly along the current survey line direction is then... for ,like If the anomaly is smaller than the preset minimum anomaly scale threshold, it is determined to be accidental noise or a very small-scale geological body, and no encrypted detection task is triggered; otherwise, it is determined to be a valid geological anomaly, and encrypted survey lines need to be generated for detailed investigation. If the geological anomaly is a measured geological anomaly, encrypted survey points are generated around the corresponding CPT in-situ test point, inserted into the task queue of the detection task, and executed. If the geological anomaly occurs, the autonomous underwater vehicle generates an encrypted detection task according to the anomaly type, inserts the encrypted detection task into the task queue of the detection task, and executes it. Based on the detection results, the autonomous underwater vehicle generates a simplified report according to the communication cycle and transmits it to the mother ship.

Images