An unmanned underwater vehicle for underwater pipeline butt joining

Abstract

The application provides an unmanned underwater vehicle for underwater pipeline butt joint. The unmanned underwater vehicle comprises a vehicle body, a support frame, a buoyancy material, a vertical propeller, a horizontal propeller, a pressure-resistant cabin, a pipeline clamping mechanism and various task loads arranged on the vehicle body. The application provides an underwater unmanned vehicle which can realize the whole-process autonomous operation from long-distance guidance to final precise butt joint only through a single leading sensor without relying on optical visual guidance and without needing to pre-lay a responder array, and the unmanned vehicle also has a backup guidance capability in the case of failure of the leading sensor.

Description

Technical Field

[0001] This invention relates to the field of deep-sea operation equipment technology, and in particular to an unmanned underwater vehicle (UUV) for underwater pipeline docking. Specifically, it relates to an UUV for underwater docking operations between a deep-sea pipeline docking interface and an external pipe section, and more particularly to a deep-sea unmanned operation device that uses an ultra-short baseline acoustic positioning system as the core guidance method, image sonar as an auxiliary backup method, and a mechanical clamping mechanism to complete the autonomous docking of pipeline sections. Background Technology

[0002] Deep-sea pipeline transportation systems are crucial infrastructure for the development and transport of deep-sea resources. In the deep-sea environment, reliably connecting external pipeline sections to pre-laid interfaces on the seabed is a key step in establishing transportation channels. Due to the high pressure, darkness, low temperature, and turbidity of the deep-sea environment, manual diving operations are impossible, necessitating remote control or autonomous docking operations using unmanned underwater vehicles (UUVs).

[0003] Currently, the known underwater vehicle docking guidance technologies in this field mainly fall into the following categories: (i) A combined approach of single-beacon USBL guidance and optical vision guidance. This approach utilizes the ultra-short baseline array (UBS) onboard the vehicle to receive signals from a single acoustic beacon deployed in the target area during the long-range phase, calculating the vehicle's azimuth and slant range relative to the beacon for coarse long-range guidance. When the vehicle approaches within tens of meters, it switches to an optical camera to perform close-range precise alignment by recognizing visual markings on the interface. The disadvantages of this approach are: in the deep-sea environment, there are many suspended particles in the water, lighting conditions are extremely poor, the optical visibility distance is very limited, and it is easily affected by turbidity caused by seabed sediment disturbance, leading to a significant reduction in the reliability of the optical guidance phase; furthermore, the single-beacon USBL can only obtain the target's three-dimensional position information and cannot provide attitude information (roll angle, pitch angle, yaw angle) for the interface. The vehicle's attitude adjustment before docking relies entirely on additional inertial navigation or visual calculation steps, increasing system complexity and accumulated alignment errors.

[0004] (ii) Long-baseline acoustic positioning scheme. This scheme involves deploying multiple transponder arrays on the seabed in the docking target area. The vehicle measures its distance to each transponder through an interrogation-response method, achieving high-precision three-dimensional positioning. This scheme offers high positioning accuracy, but requires the pre-deployment and calibration of the transponder arrays on the seabed. The deployment process is complex, time-consuming, and costly, making it unsuitable for emergency docking scenarios requiring rapid deployment. Furthermore, once deployed, the transponder arrays are difficult to reposition, resulting in poor flexibility.

[0005] (III) Pure Image-Based Sonar Guidance Scheme. Image-based sonar is used to perform multi-beam scanning imaging of the docking target. Acoustic image recognition identifies the interface geometry and guides the spacecraft to approach and dock. Image-based sonar is unaffected by water turbidity and has a range of tens to hundreds of meters. However, its angular resolution and update rate are low, making it difficult to provide real-time, high-precision six-DOF pose information. Its precise guidance capability in the final docking stage is insufficient, and it is typically used only as an auxiliary detection method.

[0006] In summary, the main drawbacks of existing technologies are: poor reliability or even failure of optical guidance in deep-sea turbid waters; single beacon USBL cannot obtain the attitude of the docking target, and the docking end still needs to rely on other sensors; LBL deployment is complex and inflexible; and pure image sonar cannot independently support high-precision final docking.

[0007] The technical problem to be solved by the present invention is to provide an underwater unmanned vehicle that does not rely on optical vision guidance, does not require the pre-deployment of transponder arrays, and can achieve fully autonomous operation from long-distance guidance to final precise docking using only a single dominant sensor, while also having backup guidance capability in case the dominant sensor fails. Summary of the Invention

[0008] The purpose of this invention is to solve the problems in the prior art and to propose an unmanned underwater vehicle for underwater pipeline docking.

[0009] This invention is achieved through the following technical solution: This invention proposes an unmanned underwater vehicle (UUV) for underwater pipeline docking. The UUV includes: a vehicle body 1, on which a support frame 1-8, buoyancy material 1-4, vertical thruster 1-7, horizontal thruster 1-9, pressure chamber 1-10, pipeline clamping mechanism 1-14, and various mission payloads are provided; the pipeline clamping mechanism 1-14 includes a claw 1-14-1, a hydraulic cylinder 1-14-2, an ultra-short baseline array 1-14-3, a multi-degree-of-freedom telescopic robotic arm 1-14-4, and a claw support frame 1-14-5; the ultra-short baseline array 1-14-3 is fixedly installed at a preset position near the claw support frame 1-14-5 or the claw 1-14-1.

[0010] Furthermore, the support frame 1-8 forms the structural skeleton of the overall aircraft 1, made of corrosion-resistant metal or high-strength composite materials, and is used to support and fix various functional modules; the buoyancy material 1-4 is fixed to the upper area of ​​the support frame 1-8 to provide net buoyancy compensation for the aircraft; two vertical thrusters 1-7 are installed on the support frame 1-8, with the thrust direction along the vertical axis of the aircraft, and are used to provide vertical motion and attitude control; four horizontal thrusters 1-9 are installed circumferentially on the support frame 1-8, with the thrust direction along the horizontal plane, and are used to provide forward, backward, lateral, and yaw motion in the horizontal plane; the vertical thrusters 1-7 and the horizontal thrusters 1-9 together constitute the propulsion system of the aircraft, realizing multi-degree-of-freedom motion control.

[0011] Furthermore, the pressure chamber 1-10 includes a pressure chamber shell 1-10-1 and an inertial navigation system 1-10-2, a battery and components 1-10-3, and a control system 1-10-4 disposed therein. The pressure chamber shell 1-10-1 is a cylindrical sealed pressure-bearing shell with a spherical end cap, providing an atmospheric pressure working environment for the internal electronic equipment. The inertial navigation system 1-10-2 is used to calculate the vehicle's attitude and position information in real time. The battery and components 1-10-3 provides power to all the vehicle's electrical equipment. The control system 1-10-4 receives data from various sensors, runs navigation and control algorithms, and outputs thruster commands.

[0012] Furthermore, the pipe clamping mechanism 1-14 is installed on the lower front of the support frame 1-8; one end of the multi-degree-of-freedom telescopic robotic arm 1-14-4 is connected to the gripper support frame 1-14-5, and the other end of the gripper support frame 1-14-5 is connected to the gripper 1-14-1, which is used to adjust the spatial position of the clamped pipe segment; the gripper 1-14-1 is driven by the hydraulic cylinder 1-14-2 to achieve opening and closing action, which is used to clamp or release the pipe segment 2 to be docked; the hydraulic device 1-12 and the hydraulic oil tank 1-13 are set on the support frame 1-8, and provide hydraulic power to the hydraulic cylinder 1-14-2 and the multi-degree-of-freedom telescopic robotic arm 1-14-4 through the hydraulic pipeline.

[0013] Furthermore, the ultra-short baseline array 1-14-3 is a multi-element acoustic receiving array used to receive acoustic positioning signals emitted by the acoustic beacon 3-1 on the docking target 3. By mounting the ultra-short baseline array 1-14-3 on the pipe clamping mechanism 1-14 instead of the vehicle body, the baseline distance between the acoustic receiving array and the front end of the clamped pipe section 2 can be shortened, reducing coordinate transformation steps and improving the positioning accuracy of the docking end.

[0014] Furthermore, the docking target 3 is a deep-sea pipeline docking interface, on which a docking interface 3-2 is installed; multiple acoustic beacons 3-1 are deployed in the surrounding area of ​​the docking interface 3-2; the acoustic beacons 3-1 are acoustic transmitters, which are fixedly installed around the docking interface 3-2 according to a known geometric configuration.

[0015] Furthermore, there are four acoustic beacons 3-1, arranged in a square, diamond, rectangular or trapezoidal layout with the axis of the interface 3-2 as the center, and the spacing between adjacent beacons is the preset baseline length; the acoustic beacons 3-1 continuously or in a preset sequence transmit acoustic positioning signals.

[0016] Furthermore, the overall mission payload of the vehicle 1 includes: an image sonar 1-1, mounted on the front of the support frame 1-8, for multi-beam acoustic imaging of targets ahead; an underwater illumination device 1-2 and an underwater camera device 1-3, mounted on the front of the support frame 1-8, for providing optical illumination and video image acquisition as auxiliary observation means; an underwater sensor 1-5 for measuring environmental parameters; an altimeter 1-6, mounted on the top of the vehicle, for measuring the vehicle's height above the seabed; and a Doppler velocimeter 1-11, mounted on the bottom of the vehicle, for measuring the vehicle's velocity vector relative to the seabed and assisting the inertial navigation system 1-10-2 in dead reckoning.

[0017] Further, the entire vehicle 1 is lowered into the water by the surface support mother ship; before or after entering the water, the claws 1-14-1 of the pipe clamping mechanism 1-14 open under the drive of the hydraulic cylinder 1-14-2, clamping the pipe segment 2 to be docked; after the pipe segment 2 to be docked is firmly clamped, the entire vehicle 1 begins to submerge and sails towards the location of the docking target 3; after the pipe segment connection and locking are completed, the claws 1-14-1 of the pipe clamping mechanism 1-14 open under the drive of the hydraulic cylinder 1-14-2, releasing the pipe segment 2 to be docked; the entire vehicle 1 retreats by the thrusters, leaves the docking area, and then rises to the surface for recovery.

[0018] Furthermore, the ultra-short baseline array 1-14-3 can also be installed in a dedicated mounting position below the front of the support frame 1-8 of the overall aircraft 1, or on the external bracket of the pressure chamber shell 1-10-1 at the front of the pressure chamber 1-10.

[0019] The beneficial effects of this invention are: 1. Single sensor guidance throughout the entire process. With a four-beacon configuration and USBL, the vehicle can obtain complete six-DOF pose information solely through the ultra-short baseline acoustic positioning system throughout the entire process from a distance of hundreds of meters to final docking. There is no need to switch between different types of sensors at long, medium, and short distances, which simplifies the system architecture and software logic and improves the continuity and reliability of the guidance process.

[0020] 2. Not reliant on optical vision. The primary guidance method is acoustic, unaffected by deep-sea turbidity or insufficient lighting, and can still function normally in harsh water conditions where optical visibility is only a few meters. Underwater cameras and lighting devices serve only as auxiliary observation tools and do not participate in the core navigation chain.

[0021] 3. No pre-installed seabed array required. The required acoustic beacons are directly installed around the docking port and deployed along with the docking port. No additional seabed transponder array deployment and calibration work is required, resulting in high deployment efficiency, low cost, and good flexibility.

[0022] 4. Backup guidance guarantee. The USBL primary guidance and the image sonar backup guidance form a dual-mode redundancy, which automatically switches to the image sonar path when the USBL signal is abnormal, improving the reliability and fault tolerance of mission completion.

[0023] 5. High docking accuracy. The four beacon baseline lengths provide excellent attitude calculation geometry. Combined with the advantage of integrating the ultra-short baseline array into the clamping mechanism for close measurement, alignment accuracy superior to conventional methods can be achieved, meeting the engineering requirements for deep-sea pipeline docking. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of an unmanned underwater vehicle for underwater pipeline docking according to the present invention; Figure 2 This is a schematic diagram of the pressure-resistant compartment structure in an unmanned underwater vehicle for underwater pipeline docking according to the present invention; Figure 3 This is a schematic diagram of the robotic arm and clamping mechanism in an unmanned underwater vehicle for underwater pipeline docking according to the present invention; Figure 4 This is a schematic diagram of the working state of an unmanned underwater vehicle for underwater pipeline docking, which clamps a pipeline segment and approaches the docking interface according to the present invention. Figure 5 This is a flowchart illustrating the deep-sea pipeline docking process of an unmanned underwater vehicle according to the present invention.

[0026] Explanation of reference numerals in the attached drawings: 1 Overall vehicle; 1-1 Image sonar; 1-2 Underwater lighting device; 1-3 Underwater camera device; 1-4 Buoyancy material; 1-5 Underwater sensor; 1-6 Altimeter; 1-7 Vertical thruster; 1-8 Support frame; 1-9 Horizontal thruster; 1-10 Pressure chamber; 1-10-1 Pressure chamber hull; 1-10-2 Inertial navigation system; 1-10-3 Battery and components; 1-10-4 Control system; 1-11 Doppler velocimeter; 1-12 Hydraulic device; 1-13 Hydraulic oil tank; 1-14 Pipe clamping mechanism; 1-14-1 Claw; 1-14-2 Hydraulic cylinder; 1-14-3 Ultra-short baseline array; 1-14-4 Multi-DOF telescopic robotic arm; 1-14-5 Claw support frame; 2 Pipe section to be docked; 3 Docking target; 3-1 Underwater acoustic beacon; 3-2 Docking interface. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Specifically, in combination Figures 1-5 This invention proposes an unmanned underwater vehicle (UUV) for underwater pipeline docking. The UUV includes: a vehicle body 1, on which a support frame 1-8, buoyancy material 1-4, vertical thruster 1-7, horizontal thruster 1-9, pressure chamber 1-10, pipeline clamping mechanism 1-14, and various mission payloads are provided; the pipeline clamping mechanism 1-14 includes a claw 1-14-1, a hydraulic cylinder 1-14-2, an ultra-short baseline array 1-14-3, a multi-degree-of-freedom telescopic robotic arm 1-14-4, and a claw support frame 1-14-5; the ultra-short baseline array 1-14-3 is fixedly installed at a preset position near the claw support frame 1-14-5 or the claw 1-14-1.

[0029] Furthermore, the support frame 1-8 forms the structural skeleton of the overall aircraft 1, made of corrosion-resistant metal or high-strength composite materials, and is used to support and fix various functional modules; the buoyancy material 1-4 is fixed to the upper area of ​​the support frame 1-8 to provide net buoyancy compensation for the aircraft; two vertical thrusters 1-7 are installed on the support frame 1-8, with the thrust direction along the vertical axis of the aircraft, and are used to provide vertical motion and attitude control; four horizontal thrusters 1-9 are installed circumferentially on the support frame 1-8, with the thrust direction along the horizontal plane, and are used to provide forward, backward, lateral, and yaw motion in the horizontal plane; the vertical thrusters 1-7 and the horizontal thrusters 1-9 together constitute the propulsion system of the aircraft, realizing multi-degree-of-freedom motion control.

[0030] Furthermore, the pressure chamber 1-10 includes a pressure chamber shell 1-10-1 and an inertial navigation system 1-10-2, a battery and components 1-10-3, and a control system 1-10-4 disposed therein. The pressure chamber shell 1-10-1 is a cylindrical sealed pressure-bearing shell with a spherical end cap, providing an atmospheric pressure working environment for the internal electronic equipment. The inertial navigation system 1-10-2 is used to calculate the vehicle's attitude and position information in real time. The battery and components 1-10-3 provides power to all the vehicle's electrical equipment. The control system 1-10-4 receives data from various sensors, runs navigation and control algorithms, and outputs thruster commands.

[0031] Furthermore, the pipe clamping mechanism 1-14 is installed on the lower front of the support frame 1-8; one end of the multi-degree-of-freedom telescopic robotic arm 1-14-4 is connected to the gripper support frame 1-14-5, and the other end of the gripper support frame 1-14-5 is connected to the gripper 1-14-1. It can realize multi-degree-of-freedom movements such as extension, pitch, and yaw under hydraulic drive, which is used to adjust the spatial posture of the clamped pipe segment; the gripper 1-14-1 is driven by the hydraulic cylinder 1-14-2 to realize the opening and closing action, which is used to clamp or release the pipe segment 2 to be docked; the hydraulic device 1-12 and the hydraulic oil tank 1-13 are set on the support frame 1-8, and provide hydraulic power to the hydraulic cylinder 1-14-2 and the multi-degree-of-freedom telescopic robotic arm 1-14-4 through the hydraulic pipeline.

[0032] Furthermore, the ultra-short baseline array 1-14-3 is a multi-element acoustic receiving array used to receive acoustic positioning signals emitted by the acoustic beacon 3-1 on the docking target 3. By mounting the ultra-short baseline array 1-14-3 on the pipe clamping mechanism 1-14 instead of the vehicle body, the baseline distance between the acoustic receiving array and the front end of the clamped pipe section 2 can be shortened, reducing coordinate transformation steps and improving the positioning accuracy of the docking end.

[0033] Furthermore, the docking target 3 is a deep-sea pipeline docking interface, on which a docking interface 3-2 is installed; multiple acoustic beacons 3-1 are deployed in the surrounding area of ​​the docking interface 3-2; the acoustic beacons 3-1 are acoustic transmitters, which are fixedly installed around the docking interface 3-2 according to a known geometric configuration.

[0034] Furthermore, there are four acoustic beacons 3-1, arranged in a square, diamond, rectangular or trapezoidal layout with the axis of the interface 3-2 as the center, and the spacing between adjacent beacons is the preset baseline length; the acoustic beacons 3-1 continuously or in a preset sequence transmit acoustic positioning signals.

[0035] Furthermore, the overall payload of the vehicle 1 includes: an image sonar 1-1, mounted on the front of the support frame 1-8, for multi-beam acoustic imaging of targets ahead; an underwater lighting device 1-2 and an underwater camera device 1-3, mounted on the front of the support frame 1-8, for providing optical illumination and video image acquisition as auxiliary observation methods; an underwater sensor 1-5 for measuring environmental parameters such as water depth, temperature, and salinity; an altimeter 1-6, mounted on the top of the vehicle, for measuring the vehicle's height above the seabed; and a Doppler velocimeter 1-11, mounted on the bottom of the vehicle, for measuring the vehicle's velocity vector relative to the seabed and assisting the inertial navigation system 1-10-2 in dead reckoning.

[0036] Furthermore, the ultra-short baseline array 1-14-3 can also be installed in a dedicated mounting position below the front of the support frame 1-8 of the overall aircraft 1, or on the external bracket of the pressure chamber shell 1-10-1 at the front of the pressure chamber 1-10.

[0037] Combination Figure 4 and Figure 5 The working process of the underwater unmanned vehicle of the present invention performing deep-sea pipeline docking operations is as follows: (1) During the deployment and clamping phase, the entire vehicle 1 is deployed into the water by the surface support mother ship. Before or after deployment, the claws 1-14-1 of the pipe clamping mechanism 1-14 open under the drive of the hydraulic cylinder 1-14-2, clamping the pipe segment 2 to be docked. After the pipe segment 2 to be docked is firmly clamped, the entire vehicle 1 begins to submerge and sails towards the location of the docking target 3.

[0038] (2) During the USBL four-beacon guided docking phase, the ultra-short baseline array 1-14-3 mounted on the vehicle 1 receives acoustic positioning signals emitted by four acoustic beacons 3-1 on the docking target 3. In the long-range phase, the ultra-short baseline array 1-14-3 obtains the three-dimensional position information of the vehicle relative to the docking interface 3-2 by calculating the azimuth and slant range of each beacon signal, guiding the vehicle to approach the docking target 3. As the distance gradually decreases, the ultra-short baseline array 1-14-3 uses the arrival time difference or phase difference of the four acoustic beacon signals, combined with the known spatial geometry of the beacons, to calculate the complete six-degree-of-freedom pose of the docking interface 3-2 relative to the vehicle 1, including the three-dimensional position and three-dimensional attitude angles. Based on the pose calculation results, the control system 1-10-4 adjusts the spatial position and attitude of the overall vehicle 1 in real time through the vertical thruster 1-7 and the horizontal thruster 1-9. Simultaneously, the hydraulic device 1-12 drives the multi-degree-of-freedom telescopic robotic arm 1-14-4 to fine-tune the pointing angle of the clamped pipe segment 2 to be docked, making the axis of the pipe segment 2 nearly coincide with the axis of the docking interface 3-2. During the close-range docking phase, the ultra-short baseline array 1-14-3 continuously updates the six-degree-of-freedom pose information in real time. The control system 1-10-4 controls the thrusters to eliminate lateral and angular deviations. When the pose deviation meets the docking conditions, the control system controls the overall vehicle 1 to slowly advance axially, inserting the front end of the pipe segment 2 into the docking interface 3-2. The docking interface 3-2 is equipped with a locking mechanism that automatically locks after the pipe segment is inserted, completing the connection.

[0039] (3) During the release and recovery phase, after the pipeline segment connection and locking are completed, the claws 1-14-1 of the pipeline clamping mechanism 1-14 open under the drive of the hydraulic cylinder 1-14-2, releasing the pipeline segment 2 to be docked. The entire vehicle 1 retreats by the thruster, leaves the docking area, and then floats to the surface for recovery.

[0040] During USBL guidance, if abnormal situations such as acoustic beacon signal obstruction, severe multipath interference, or beacon malfunction prevent the USMR array 1-14-3 from properly calculating its pose, the control system 1-10-4 automatically switches to the backup guidance path: It activates the imaging sonar 1-1 to perform a multi-beam scan of the area ahead, identifies the geometric contour of the docking interface 3-2 through acoustic imaging, and guides the vehicle to approach the docking interface 3-2 until docking is completed, or switches back to the primary guidance path after the USBL signal is restored. The underwater illumination device 1-2 and the underwater camera device 1-3 provide auxiliary observation in the backup path.

[0041] The main advantages of this invention over the prior art are as follows: 1. Four-beacon configuration and USBL jointly calculate the complete six-DOF pose. Four acoustic beacons 3-1 form a known spatial geometry around the interface 3-2. The ultra-short baseline array 1-14-3 simultaneously receives four acoustic signals. By calculating the phase difference or time difference of arrival, and combining the prior knowledge of the beacon geometry, the complete six-DOF pose of the interface can be directly obtained. This supports the entire process from long-distance guidance to final precise docking without switching sensors.

[0042] 2. Dual-mode guidance architecture with USBL as the primary and image sonar as the backup. Ultra-short baseline acoustic positioning is used as the primary guidance method throughout the entire docking process. The image sonar backup path is only activated when the USBL signal is abnormal. This avoids the reliability issues of optical visual guidance in deep-sea turbid waters, and also avoids the high cost and inflexibility of LBL array deployment.

[0043] 3. The ultra-short baseline array is integrated into the clamping mechanism. The ultra-short baseline array 1-14-3 is directly mounted on the pipe clamping mechanism 1-14, which shortens the position conversion chain between the acoustic receiving array and the front end of the clamped pipe segment, reduces coordinate transmission errors, and improves the control accuracy at the docking end.

[0044] Implementation Method 1: Complete Operation Process of USBL Four-Beacon Full-Process Guided Docking This implementation describes the complete deep-sea pipeline docking operation process using an ultra-short baseline acoustic positioning system as the core guidance method and four underwater acoustic beacons 3-1 arranged in a square.

[0045] (a) Water surface deployment and pipe clamping The entire vehicle assembly 1 is lowered from the mother ship to the water surface. After the system is powered on, power is supplied to the control system 1-10-4 and all sensors via the power distribution system. Before entering the water or while floating on the surface, the control system 1-10-4 sends a command to the hydraulic device 1-12. Hydraulic oil is pumped from the hydraulic oil tank 1-13 through pipelines to the hydraulic cylinder 1-14-2. The piston rod of the hydraulic cylinder 1-14-2 extends, driving the claw 1-14-1 to open symmetrically to its maximum opening through a linkage mechanism. The mother ship crane or deployment frame sends the pipe section 2 to be docked into the clamping range of the claw 1-14-1. The control system 1-10-4 controls the hydraulic cylinder 1-14-2 to reverse its movement, causing the claw 1-14-1 to retract inward, firmly clamping the pipe section 2 to be docked. The clamping force is fed back to the control system 1-10-4 in real time by the pressure sensor in the hydraulic circuit, ensuring that the clamping force is within the preset safety range. After clamping confirmation, the entire vehicle assembly 1 detaches from the mother ship's lifting cable and enters autonomous operation mode.

[0046] (II) Diving and Long-Distance Navigation Control system 1-10-4 activates vertical thrusters 1-7 and horizontal thrusters 1-9, propelling the vehicle assembly 1 to descend into the deep sea and navigate towards the docking target 3. During the descent, inertial navigation system 1-10-2 continuously outputs the vehicle assembly's three-dimensional attitude angles, angular velocities, and acceleration data using its built-in fiber optic gyroscope and three-axis accelerometer, and performs dead reckoning in real time. Doppler velocimeter 1-11 emits acoustic pulses towards the seabed, accurately measuring the vehicle's three-dimensional ground velocity vector relative to the seabed using the Doppler frequency shift principle, and sends the data to control system 1-10-4. Control system 1-10-4 performs Kalman filtering to fuse the trajectory calculated by inertial navigation system 1-10-2 with the velocity data from Doppler velocimeter 1-11, correcting the cumulative drift of the inertial navigation system over time. Simultaneously, it combines the altitude above the seabed measured by altimeter 1-6 and the depth data measured by underwater sensor 1-5 to stably control the vehicle assembly 1 to approach the docking target 3 area at a predetermined depth.

[0047] Once the vehicle assembly 1 enters the effective range of the ultra-short baseline (USB) signal, the USB array 1-14-3 mounted on the pipe clamping mechanism 1-14 begins receiving acoustic positioning signals emitted by four underwater acoustic beacons 3-1 installed around the docking target 3 and the docking interface 3-2. The four underwater acoustic beacons 3-1 are arranged in a square configuration centered on the axis of the docking interface 3-2. Each beacon emits acoustic pulses of different frequencies via frequency division multiple access (FDMA), enabling the USB array 1-14-3 to distinguish and independently process each signal. The multi-element hydrophone array inside the USB array 1-14-3 measures the azimuth and time of arrival of each beacon signal, calculating the spatial azimuth and slant range of each beacon relative to the USB array. Based on the azimuth and range information of the four beacons, and combined with the known square geometric configuration of the beacons, the control system 1-10-4 calculates the three-dimensional spatial position of the vehicle assembly 1 relative to the docking interface 3-2.

[0048] During this long-range phase, since the distance between the vehicle and the docking target is significantly greater than the baseline length between the four beacons, the four underwater acoustic beacons 3-1 approximate a single equivalent point source in terms of angular resolution. The control system 1-10-4 primarily uses robust three-dimensional position calculations to guide the vehicle as a whole 1 towards the docking target 3 at a relatively high speed. Simultaneously, the imaging sonar 1-1, installed at the front of the support frame 1-8, performs a long-range scan of the forward sector in low-frequency mode, providing the operators with auxiliary situational awareness of the environment ahead. The altimeter 1-6 and Doppler velocimeter 1-11 continuously provide feedback on altitude above the seabed and ground speed, ensuring that the vehicle maintains a safe altitude during the approach and avoids contact with seabed protrusions.

[0049] (III) Fine calculation of six-DOF pose at mid-range As the distance between the overall vehicle 1 and the docking target 3 gradually decreases to a moderate range, the arrival time difference or carrier phase difference generated by the four underwater acoustic beacons 3-1 on each hydrophone element of the ultra-short baseline array 1-14-3 gradually becomes significant, and the spatial geometric configurations among the four beacons can be effectively distinguished in acoustic measurements. The control system 1-10-4 automatically switches to the six-degree-of-freedom attitude fine calculation mode: using the arrival azimuth angle, pitch angle, and slant range of the four beacon signals simultaneously acquired by the ultra-short baseline array 1-14-3, combined with the precise three-dimensional coordinates of the four underwater acoustic beacons 3-1 in the docking interface coordinate system pre-stored in the control system, the six-degree-of-freedom transformation relationship between the docking interface 3-2 coordinate system and the ultra-short baseline array 1-14-3 coordinate system, namely the three-dimensional relative position and the three-dimensional relative attitude angle, is calculated in real time through nonlinear least squares optimization or extended Kalman filter algorithm.

[0050] After obtaining the complete six-degree-of-freedom pose of the interface 3-2, the control system 1-10-4 enters the active docking control phase. Based on the pose deviation, the control system 1-10-4 outputs thrust control commands to the vertical thruster 1-7 and the horizontal thruster 1-9, respectively, driving the overall vehicle 1 to translate and rotate in space, eliminating lateral and angular deviations between the overall vehicle and the axis of the interface 3-2. Simultaneously, based on the remaining pose error fed back in real-time by the ultra-short baseline array 1-14-3, the control system 1-10-4 outputs control signals to the hydraulic device 1-12, driving the multi-degree-of-freedom telescopic robotic arm 1-14-4 to perform fine-tuning actions such as extension, pitch, or yaw, further adjusting the pointing angle of the clamped pipe segment 2 to be docked. Since the ultra-short baseline array 1-14-3 is directly mounted on the pipe clamping mechanism 1-14, its measurement reference and the front end of the clamped pipe section have only a fixed and pre-calibrated coordinate transformation relationship. This avoids the additional coordinate transmission error introduced by the mechanical gap and elastic deformation between the support frame 1-8 and the clamping mechanism when the array is mounted on the main body of the aircraft, and significantly improves the accuracy of the end control.

[0051] During this stage, if the deep-sea environment is relatively clear, underwater lighting devices 1-2 and underwater camera devices 1-3 can provide operators with auxiliary visual confirmation images, but they do not participate in the pose calculation of the automatic control loop.

[0052] (iv) Close-range final docking When the control system 1-10-4 determines that the attitude deviation meets the preset docking conditions—the lateral and vertical deviations converge to the preset allowable range, and the angular deviation between the axis of the pipe segment 2 to be docked and the axis of the docking interface 3-2 converges to the preset allowable range—the docking enters the final insertion stage. The control system 1-10-4 controls the vertical thruster 1-7 and the horizontal thruster 1-9 to perform precise attitude maintenance control with extremely low thrust, while simultaneously outputting a slow axial thrust command to the horizontal thruster 1-9, driving the overall vehicle 1 to smoothly advance the pipe segment 2 to be docked along the axial direction of the docking interface 3-2. During this process, the ultra-short baseline array 1-14-3 continuously outputs six-degree-of-freedom attitude information at the highest update rate. The control system 1-10-4 monitors the attitude error in real time. Once a deviation is detected to exceed the allowable range, the axial thrust is immediately paused and a correction action is performed until the attitude conditions are met again before continuing thrusting.

[0053] After the front end of the pipe segment 2 enters the guide cone surface of the interface 3-2, the final alignment is completed with the assistance of the mechanical guide structure. After the front end of the pipe segment is inserted to the designed depth, the locking mechanism set inside the interface 3-2 is automatically triggered to lock and fix the pipe segment. The control system 1-10-4 determines that the connection locking is complete through changes in hydraulic circuit pressure or acoustic feedback signals.

[0054] (v) Release and Recovery After the pipeline segment connection is confirmed, the control system 1-10-4 sends a release command to the hydraulic device 1-12. The hydraulic cylinder 1-14-2 drives the claws 1-14-1 to open symmetrically, releasing the pipeline segment 2 to be docked. The control system 1-10-4 then controls the horizontal thruster 1-9 to propel in the opposite direction, and the overall vehicle 1 slowly retreats axially, disengaging from the docking area. After the overall vehicle 1 has retreated to a safe distance, the control system 1-10-4 controls the vertical thruster 1-7 to increase thrust, driving the overall vehicle 1 to float upward. At the same time, the inertial navigation system 1-10-2 and the Doppler velocimeter 1-11 provide return navigation information, guiding the vehicle back to the mother ship's recovery area on the surface, completing the entire docking operation.

[0055] Implementation Method 2: Operation Procedure for Switching to Image Sonar Backup Guidance When USBL Signal is Abnormal This embodiment describes the complete process by which the control system automatically switches to the image sonar backup guidance path and completes docking when an abnormal situation occurs during the USBL boot process.

[0056] At any stage of the operation process described in Implementation Method 1, the control system 1-10-4 continuously monitors the working status of the ultra-short baseline array 1-14-3 in real time. Monitoring indicators include, but are not limited to: the received signal-to-noise ratio (SNR) of each of the four underwater acoustic beacon 3-1 signals, the number of consecutive valid received frames for each beacon signal, the convergence of the covariance matrix of the pose calculation results, and the inter-frame continuity of the calculation results. When the control system 1-10-4 detects any of the following abnormal conditions, it determines that USBL guidance is currently unavailable: the SNR of any underwater acoustic beacon signal is continuously lower than a preset threshold; a beacon signal is lost or experiences unrecoverable bit errors within multiple consecutive calculation cycles; the covariance matrix of the pose calculation results diverges, indicating that the calculation results are unreliable; or the pose calculation results exhibit inter-frame jumps exceeding the physically reachable range.

[0057] After USBL guidance is deemed unavailable, control system 1-10-4 automatically performs a guidance mode switch: first, it pauses the current docking propulsion action, maintaining the overall vehicle 1 in a fixed-point hover at its current spatial position; simultaneously, it activates image sonar 1-1, switching it to high-frequency, high-resolution multi-beam scanning mode. Image sonar 1-1 continuously transmits high-frequency acoustic pulses to a certain angular sector in front of the vehicle, receives the acoustic backscattered echoes from seabed targets, and generates a two-dimensional acoustic grayscale image based on the echo intensity differences. Control system 1-10-4 processes each frame of acoustic image returned by image sonar 1-1 in real time: first, it separates the geometric boundaries of potential targets from background noise using adaptive threshold segmentation and edge extraction algorithms; then, it uses prior knowledge of the known geometric shape of interface 3-2 to perform shape matching and feature recognition on the extracted geometric boundaries, locking the position of interface 3-2 in the acoustic image; finally, based on the pixel coordinates of the interface in the acoustic image and the beam angle geometry of the image sonar, it calculates the azimuth and approximate distance of interface 3-2 relative to overall vehicle 1.

[0058] The control system 1-10-4 uses the azimuth and distance information calculated by the image sonar as guidance input, controlling the thrusters to drive the overall vehicle 1 slowly towards the docking interface 3-2. During the approach, the underwater lighting device 1-2 and the underwater camera device 1-3 are activated simultaneously, providing auxiliary visual images for the operators when the optical visibility distance allows. When the vehicle approaches within the near-range blind zone of the image sonar, if the USBL signal has returned to normal and the preset reliability conditions are met, the control system 1-10-4 automatically switches back to the USBL-dominant guidance mode and continues to complete the final precise docking according to the process described in Implementation Method 1. If the USBL signal is not restored, the image sonar 1-1 continues to guide the vehicle to a very close distance to the docking interface. The control system 1-10-4 relies on the short-term attitude maintenance capability provided by the inertial navigation system 1-10-2 and the terminal ranging information of the image sonar 1-1 to control the vehicle to complete slow axial propulsion and pipe section insertion until the locking mechanism in the docking interface 3-2 is triggered.

[0059] Implementation Method 3: Alternative Solutions for the Installation Location of Ultra-Short Baseline Arrays In the aforementioned embodiments, the ultra-short baseline array 1-14-3 is mounted on the pipe clamping mechanism 1-14, specifically on the outer side of the pre-set mounting base of the claw support frame 1-14-5. As an optional alternative mounting scheme, the ultra-short baseline array 1-14-3 can also be mounted on a dedicated mounting position below the front of the support frame 1-8 of the overall aircraft 1, or on the external support of the pressure hull at the front of the pressure chamber 1-10.

[0060] This alternative requires a one-time system calibration after the vehicle's final assembly: At a land or shallow water calibration site, using a laser tracker or optical total station, the fixed transformation matrix of the acoustic center of the ultra-short baseline array 1-14-3 in the coordinate system of the end of the pipe clamping mechanism 1-14 is precisely measured, and this calibration matrix parameter is written into the pose calculation module of the control system 1-10-4. In the actual docking operation, the control system 1-10-4 first calculates the six-degree-of-freedom pose of the ultra-short baseline array 1-14-3 relative to the docking interface 3-2 according to the method described in Embodiment 1, and then superimposes the pre-calibrated fixed transformation matrix to obtain the final pose relationship between the front end of the pipe segment 2 to be docked and the docking interface 3-2.

[0061] The advantages of this alternative are: the ultra-short baseline array 1-14-3 is located away from the mechanical moving parts of the hydraulic device 1-12, hydraulic oil tank 1-13, and multi-degree-of-freedom telescopic robotic arm 1-14-4, resulting in less mechanical vibration noise and hydraulic fluid noise, and a better acoustic reception signal-to-noise ratio environment. Its disadvantages are: it increases the coordinate transformation chain length from the acoustic measurement reference to the front end of the clamping mechanism; calibration residual errors and structural micro-deformations will be amplified during coordinate transmission, which will have a certain impact on the accuracy of end-point control. Both installation schemes can be flexibly selected according to the specific structural layout of the aircraft, noise control level, and docking accuracy requirements.

[0062] Implementation Method 4: Alternatives to the Geometry of Underwater Acoustic Beacons In the aforementioned embodiments, the four underwater acoustic beacons 3-1 are arranged in a square configuration centered on the axis of the interface 3-2. As an optional alternative configuration, the four underwater acoustic beacons 3-1 can be flexibly adjusted to a rhomboid, rectangular, or trapezoidal configuration based on the actual geometry of the flange of the interface 3-2 and the available installation space. The rhomboid configuration is suitable for situations where the installation space of the interface flange is asymmetrical in the vertical and horizontal directions, while the rectangular configuration is suitable for situations where the flange width is limited but the vertical space is ample. Regardless of the configuration, the three-dimensional spatial coordinates of the four underwater acoustic beacons 3-1 in the interface coordinate system must be accurately determined after deployment using underwater photogrammetry or acoustic calibration methods, and the calibration coordinate parameters must be pre-written into the control system 1-10-4. The pose calculation algorithm calls the corresponding beacon geometric model during runtime, thus adapting to different beacon configurations and outputting the correct six-degree-of-freedom pose.

[0063] Furthermore, in applications requiring extremely high docking accuracy or high redundancy, the number of underwater acoustic beacons 3-1 can be increased from four to five or six, and their spatial distribution around the interface 3-2 can be designed based on optimizing the geometric accuracy factor. With the increased number of beacons, the ultra-short baseline array 1-14-3 simultaneously receives multiple acoustic signals. The pose calculation algorithm of the control system 1-10-4 utilizes the measurement information from the redundant beacons for least-squares adjustment or robust estimation, effectively suppressing measurement anomalies caused by multipath interference or local obstruction of individual beacon signals, further improving the robustness and accuracy of the six-degree-of-freedom pose calculation.

[0064] The above provides a detailed description of an unmanned underwater vehicle for underwater pipeline docking proposed in this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. An unmanned underwater vehicle for underwater pipeline docking, characterized in that, The unmanned underwater vehicle includes: a vehicle body (1), on which a support frame (1-8), buoyancy material (1-4), vertical thruster (1-7), horizontal thruster (1-9), pressure chamber (1-10), pipe clamping mechanism (1-14) and various mission payloads are provided; the pipe clamping mechanism (1-14) includes a claw (1-14-1), a hydraulic cylinder (1-14-2), an ultra-short baseline array (1-14-3), a multi-degree-of-freedom telescopic robotic arm (1-14-4) and a claw support frame (1-14-5); the ultra-short baseline array (1-14-3) is fixedly installed at a preset position near the claw support frame (1-14-5) or the claw (1-14-1).

2. The unmanned underwater vehicle according to claim 1, characterized in that, The support frame (1-8) is the structural skeleton of the overall aircraft (1), made of corrosion-resistant metal or high-strength composite material, used to support and fix the various functional modules; the buoyancy material (1-4) is fixed to the upper area of ​​the support frame (1-8) to provide net buoyancy compensation for the aircraft; two vertical thrusters (1-7) are installed on the support frame (1-8), with the thrust direction along the vertical axis of the aircraft, used to provide vertical motion and attitude control; four horizontal thrusters (1-9) are installed around the support frame (1-8), with the thrust direction along the horizontal plane, used to provide forward, backward, lateral and yaw motion in the horizontal plane; the vertical thrusters (1-7) and the horizontal thrusters (1-9) together constitute the propulsion system of the aircraft, realizing multi-degree-of-freedom motion control.

3. The unmanned underwater vehicle according to claim 2, characterized in that, The pressure chamber (1-10) includes a pressure chamber shell (1-10-1) and an inertial navigation system (1-10-2), a battery and components (1-10-3), and a control system (1-10-4) housed within it. The pressure chamber shell (1-10-1) is a cylindrical sealed pressure-bearing shell with a spherical end cap, providing an atmospheric pressure working environment for the internal electronic equipment. The inertial navigation system (1-10-2) is used to calculate the vehicle's attitude and position information in real time. The battery and components (1-10-3) provides power to all the vehicle's electrical equipment. The control system (1-10-4) receives data from various sensors, runs navigation and control algorithms, and outputs thruster commands.

4. The unmanned underwater vehicle according to claim 3, characterized in that, The pipe clamping mechanism (1-14) is installed at the lower front of the support frame (1-8); one end of the multi-degree-of-freedom telescopic robotic arm (1-14-4) is connected to the gripper support frame (1-14-5), and the other end of the gripper support frame (1-14-5) is connected to the gripper (1-14-1), which is used to adjust the spatial position of the clamped pipe segment; the gripper (1-14-1) is driven by the hydraulic cylinder (1-14-2) to achieve opening and closing action, which is used to clamp or release the pipe segment (2) to be docked; the hydraulic device (1-12) and the hydraulic oil tank (1-13) are set on the support frame (1-8), and provide hydraulic power to the hydraulic cylinder (1-14-2) and the multi-degree-of-freedom telescopic robotic arm (1-14-4) through the hydraulic pipeline.

5. The unmanned underwater vehicle according to claim 4, characterized in that, The ultra-short baseline array (1-14-3) is a multi-element acoustic receiving array used to receive acoustic positioning signals emitted from the acoustic beacon (3-1) on the docking target (3). By installing the ultra-short baseline array (1-14-3) on the pipe clamping mechanism (1-14) instead of the main body of the vehicle, the baseline distance between the acoustic receiving array and the front end of the clamped pipe section (2) can be shortened, reducing coordinate transformation links and improving the positioning accuracy of the docking end.

6. The unmanned underwater vehicle according to claim 5, characterized in that, The docking target (3) is a deep-sea pipeline docking interface, on which a docking interface (3-2) is installed; multiple acoustic beacons (3-1) are arranged in the surrounding area of ​​the docking interface (3-2); the acoustic beacons (3-1) are acoustic transmitters, which are fixedly installed around the docking interface (3-2) according to the known geometric configuration.

7. The unmanned underwater vehicle according to claim 6, characterized in that, There are four acoustic beacons (3-1), arranged in a square, diamond, rectangular or trapezoidal layout with the axis of the interface (3-2) as the center. The distance between adjacent beacons is the preset baseline length. The acoustic beacons (3-1) continuously or in a preset sequence emit acoustic positioning signals.

8. The unmanned underwater vehicle according to claim 1, characterized in that, The overall mission payload of the vehicle (1) includes: an image sonar (1-1), mounted on the front of the support frame (1-8), for multi-beam acoustic imaging of targets ahead; an underwater lighting device (1-2) and an underwater camera device (1-3), mounted on the front of the support frame (1-8), for providing optical illumination and video image acquisition as an auxiliary observation means; an underwater sensor (1-5), for measuring environmental parameters; an altimeter (1-6), mounted on the top of the vehicle, for measuring the vehicle's height above the seabed; and a Doppler velocimeter (1-11), mounted on the bottom of the vehicle, for measuring the vehicle's velocity vector relative to the seabed and assisting the inertial navigation system (1-10-2) in dead reckoning.

9. The unmanned underwater vehicle according to claim 1, characterized in that, The overall vehicle (1) is lowered into the water by the support mother ship. Before or after entering the water, the claws (1-14-1) of the pipe clamping mechanism (1-14) open under the drive of the hydraulic cylinder (1-14-2) to clamp the pipe segment (2) to be docked. After the pipe segment (2) to be docked is firmly clamped, the overall vehicle (1) begins to dive and sails towards the location of the docking target (3). After the pipe segment connection is locked, the claws (1-14-1) of the pipe clamping mechanism (1-14) open under the drive of the hydraulic cylinder (1-14-2) to release the pipe segment (2) to be docked. The overall vehicle (1) retreats by the thruster, leaves the docking area, and then rises to the surface for recovery.

10. The unmanned underwater vehicle according to claim 1, characterized in that, The ultra-short baseline array (1-14-3) can also be installed in a dedicated mounting position below the front of the support frame (1-8) of the overall aircraft (1), or on the external support of the pressure tank shell (1-10-1) at the front of the pressure tank (1-10).

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