Mechanical arm underwater laying and recovering AUV system and docking method

Abstract

The application relates to an underwater mechanical arm laying and recovering AUV system, which comprises a recovery mother ship, a recovery cage arranged in the belly of the recovery mother ship and used for clamping an AUV, a six-axis mechanical arm with one end connected to the recovery mother ship and the other end connected to the recovery cage and used for driving the recovery cage to move and open and close the recovery cage, and an acoustic-optic guiding system used for guiding the AUV to move towards the recovery mother ship; wherein the six-axis mechanical arm and the acoustic-optic guiding system can drive the recovery cage to clamp the AUV, and the AUV is controlled to actively dock with the recovery cage through the acoustic-optic guiding system. The six-axis mechanical arm clamping the AUV and the AUV active docking are combined to realize the laying and recovery of the AUV in multiple scenes and modes, that is, in a static docking scene, the six-axis mechanical arm clamps the AUV and the AUV actively docks; in a dynamic docking scene, the six-axis mechanical arm clamps the AUV and the AUV actively docks, the mutual interference of the two is reduced during recovery, and the laying and recovery of the AUV are easy to realize quickly and safely.

Description

Technical Field

[0001] This invention relates to the field of cableless underwater robot technology, and in particular to a robotic arm underwater deployment and recovery AUV system and docking method. Background Technology

[0002] An Autonomous Underwater Vehicle (AUV) is a type of underwater robot. An AUV is a cableless underwater robot with advantages such as stealth, maneuverability, and autonomous safety, making it an important piece of equipment for underwater special operations. It plays a vital role in both civilian and military fields, for example, in marine environmental monitoring, deep-sea environmental exploration, deep-sea search and rescue, submarine cable maintenance, underwater mine laying and clearing, and reconnaissance of specific areas.

[0003] AUVs, constrained by their size, cannot sustain prolonged underwater missions due to their limited power reserves. Furthermore, data collected after missions and maintenance require retrieval. However, deploying and recovering AUVs on surface or land necessitates large machinery, which suffers from poor concealment, operational complexity, and high costs. Complex sea conditions pose significant challenges to AUV deployment and recovery. Therefore, achieving underwater deployment and recovery of AUVs has become a current research hotspot.

[0004] Based on the movement of the underwater docking platform, docking can be categorized into two types: static docking and dynamic docking. The advantages of static docking include the ability to transmit data, replenish energy, and perform maintenance on the AUV after docking, extending its underwater mission time and avoiding difficulties in manual recovery. However, its disadvantages are also significant: the docking platform is fixed in a specific area and cannot move, resulting in greater spatial limitations and less flexibility. Dynamic docking, compared to static docking, not only possesses the latter's advantages but also faces fewer time and space constraints, making it crucial for improving the overall performance of AUVs.

[0005] Existing underwater deployment and recovery methods for AUVs mainly involve fixed funnel docking and fork-type capture docking. However, both methods suffer from drawbacks such as low docking success rates, significant space limitations, and lack of flexibility. These severely restrict the safety, accuracy, and speed of underwater AUV deployment and recovery.

[0006] To address this, we propose an underwater deployment and recovery system for AUVs using a robotic arm, along with a docking method. Summary of the Invention

[0007] To address the shortcomings of existing production technologies, this applicant provides a robotic arm-based underwater deployment and retrieval system and docking method for AUVs. This system combines a six-axis robotic arm for grasping the AUV with active docking, enabling multi-scenario and multi-mode deployment and retrieval. Specifically, in static docking scenarios, the six-axis robotic arm grasps the AUV and actively docks; in dynamic docking scenarios, the six-axis robotic arm grasps the AUV and actively docks. The system is simple to design, easy to operate, has a high success rate, reduces mutual interference during retrieval, and facilitates rapid and safe deployment and retrieval of AUVs.

[0008] The technical solution adopted in this invention is as follows:

[0009] A robotic arm-based underwater deployment and recovery system for AUVs includes:

[0010] Recover the mothership;

[0011] Recovery cage, located on the flank of the recovery mothership, is used to clamp the AUV;

[0012] The six-axis robotic arm is connected to the recovery mother boat at one end and the recovery cage at the other end. It is used to drive the movement of the recovery cage and to open and close the recovery cage.

[0013] An acoustic-optical guidance system is used to guide the AUV toward the recovery mothership;

[0014] Among them, the six-axis robotic arm and the acoustic-optical guidance system can drive the recovery cage to grab the AUV, and control the AUV to actively dock with the recovery cage through the acoustic-optical guidance system.

[0015] Its further features are:

[0016] The hull of the recovery mothership is provided with a groove, and one end of the six-axis robotic arm is set in the groove.

[0017] The six-axis robotic arm includes a first rotary joint, a first pitch joint, a second pitch joint, a third pitch joint, a second rotary joint, and an opening / closing joint. The first rotary joint is connected to the first pitch joint, the first pitch joint is connected to the second pitch joint, the second pitch joint is connected to the third pitch joint, the third pitch joint is connected to the second rotary joint, the second rotary joint is connected to the opening / closing joint, and the opening / closing joint is connected to the recovery cage. The recovery cage consists of two arc-shaped recovery cages, which are rotated by the opening / closing joint.

[0018] The acoustic-optical guidance system includes a communication sonar, a first underwater camera, a first guidance light, a second underwater camera, and a second guidance light. The communication sonar is mounted on the second slewing joint, the first underwater camera is mounted on the communication sonar, the first guidance light is mounted on the recovery cage, the second underwater camera is mounted on the bow of the AUV, and the second guidance light is mounted on the back of the AUV.

[0019] The first guide light and the second underwater camera form a six-axis robotic arm vision guidance system, and the first underwater camera and the second guide light form an AUV vision guidance system.

[0020] This invention also discloses a docking method for an underwater deployment and recovery AUV system using a robotic arm, comprising the following steps:

[0021] Step 1: Before the AUV is deployed, the six-axis robotic arm retracts into the groove of the recovery mother boat, and the opening and closing joints of the six-axis robotic arm drive the recovery cage to clamp the AUV.

[0022] Step 2: During the underwater deployment of the AUV, the position of the recovery cage and the AUV is adjusted by the six-axis robotic arm, and the opening and closing joint drives the recovery cage to open, so that the recovery cage no longer clamps the AUV, thus completing the deployment of the AUV.

[0023] Step 3: During AUV recovery, the communication sonar communicates with the AUV and guides the AUV to the vicinity of the recovery mother vessel. Then, the six-axis robotic arm vision guidance system and the AUV vision guidance system guide the AUV for recovery.

[0024] Its further features are:

[0025] In step three, the mother vessel remains hovered while the AUV actively docks with the recovery cage. When the AUV is far from the mother vessel, the communication sonar communicates with the AUV and guides it to move closer to the mother vessel. Simultaneously, the six-axis robotic arm extends downwards, and the third pitch joint and the second rotation joint adjust the direction of the recovery cage opening to align it with the bow of the AUV. When the AUV moves close to the mother vessel, the guidance mode is switched to visual guidance mode. The AUV uses the second underwater camera mounted on its bow to identify the first guide light on the recovery cage to adjust its attitude. The AUV then enters the recovery cage using its own thrusters, completing the AUV's recovery.

[0026] The mother vessel remains hovering while the six-axis robotic arm grabs the AUV. The communication sonar communicates with the AUV and guides it to move beneath the mother vessel and within the reach of the six-axis robotic arm. The six-axis robotic arm uses a first underwater camera to identify the second guide light on the AUV's back. The six-axis robotic arm then drives the opening and closing joints to open the recovery cage. The six-axis robotic arm rotates its joints to grab the AUV. After grabbing the AUV, the six-axis robotic arm retracts to its initial state, completing the recovery of the AUV.

[0027] The mother vessel remains in motion while the AUV actively docks with the recovery cage. When the AUV is far from the mother vessel, the communication sonar communicates with the AUV, sending the mother vessel's heading, speed, and position information to the AUV. The AUV adjusts its speed and heading based on the information received and moves rapidly towards the mother vessel. When the AUV approaches the mother vessel, it continues to obtain the mother vessel's heading and speed information via the communication sonar. To reduce mutual interference during docking, the six-axis robotic arm extends downwards, aligning the recovery cage with the mother vessel's bow. The AUV uses the second underwater camera to identify the first guide light to adjust its position and attitude. The AUV increases its speed and moves towards the center of the recovery cage. After the AUV enters the recovery cage, the six-axis robotic arm retracts to its initial state, completing the AUV's recovery.

[0028] The mother vessel remains in motion while a six-axis robotic arm grasps the AUV. When the AUV is far from the mother vessel, the communication sonar communicates with the AUV, sending the mother vessel's heading, speed, and position information to the AUV. Based on this information, the AUV adjusts its speed and heading, quickly moving towards the reachable position of the mother vessel's six-axis robotic arm. When the AUV approaches the mother vessel, it continues to obtain and maintain the mother vessel's heading and speed information via the communication sonar. The six-axis robotic arm uses a first underwater camera to identify the second guide light on the AUV to determine the relative positional error between the two, thereby driving each joint to grasp the AUV. After grasping the AUV, the six-axis robotic arm retracts to its initial state, completing the recovery of the AUV.

[0029] The beneficial effects of this invention are as follows:

[0030] This invention features a compact and rational structure, and is easy to operate. It achieves multi-scenario and multi-mode deployment and retrieval of AUVs by combining a six-axis robotic arm for grasping the AUV with active AUV docking. Specifically, in static docking scenarios, the six-axis robotic arm grasps the AUV and actively docks; in dynamic docking scenarios, the six-axis robotic arm grasps the AUV and actively docks. The design is simple, easy to operate, and has a high success rate. It reduces mutual interference during retrieval, facilitating rapid and safe deployment and retrieval of AUVs.

[0031] In addition, the present invention also has the following advantages:

[0032] (1) By setting up a communication sonar, when the AUV is far away from the recovery mother ship, the communication sonar communicates with the AUV and sends the heading, speed and position information of the recovery mother ship to the AUV. The AUV adjusts its own speed and heading according to the information obtained and moves quickly below the recovery mother ship.

[0033] (2) By setting up a six-axis robotic arm vision guidance system and an AUV vision guidance system, when the six-axis robotic arm grabs the AUV, the six-axis robotic arm vision guidance system provides guidance, and when the AUV actively docks, the AUV vision guidance system provides guidance.

[0034] (3) By setting up a six-axis robotic arm, the position and angle of the recycling cage can be adjusted, which facilitates the recycling of AUV. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the recovery mothership and AUV of the present invention.

[0036] Figure 2 for Figure 1 The main view.

[0037] Figure 3 This is a schematic diagram of the six-axis robotic arm of the present invention.

[0038] Figure 4 This is a schematic diagram of the AUV of the present invention.

[0039] Figure 5 This is a schematic diagram of the deployment of AUVs by the recovery mother vessel of the present invention.

[0040] Figure 6 This is a schematic diagram of the AUV actively docking with the recovery cage according to the present invention.

[0041] Figure 7 This is a schematic diagram of the six-axis robotic arm grasping an AUV according to the present invention.

[0042] The system includes: 1. Recovery mother vessel; 101. Groove; 2. Six-axis robotic arm; 201. First rotary joint; 202. First pitch joint; 203. Second pitch joint; 204. Third pitch joint; 205. Second rotary joint; 206. Opening and closing joint; 3. Recovery cage; 4. AUV; 5. Acoustic and optical guidance system; 501. Communication sonar; 502. First underwater camera; 503. First guide light; 504. Second underwater camera; 505. Second guide light. Detailed Implementation

[0043] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0044] like Figures 1-7 As shown, an underwater deployment and recovery system for AUVs with a robotic arm includes a recovery mother vessel 1, a six-axis robotic arm 2, a recovery cage 3, and an acoustic-optical guidance system 5, used for deploying and recovering AUVs 4. A groove 101 is provided on the flank of the recovery mother vessel 1, one end of the six-axis robotic arm 2 is disposed within the groove 101, and the other end of the six-axis robotic arm 2 is connected to the recovery cage 3.

[0045] like Figure 6 As shown, the six-axis robotic arm 2 includes a first rotary joint 201, a first pitch joint 202, a second pitch joint 203, a third pitch joint 204, a second rotary joint 205, and an opening / closing joint 206. The first rotary joint 201 is connected to the first pitch joint 202, the first pitch joint 202 is connected to the second pitch joint 203, the second pitch joint 203 is connected to the third pitch joint 204, the third pitch joint 204 is connected to the second rotary joint 205, the second rotary joint 205 is connected to the opening / closing joint 206, and the opening / closing joint 206 is connected to the retrieval cage 3. The retrieval cage 3 consists of two arc-shaped retrieval cages, which are rotated by the opening / closing joint 206. Before deploying the AUV4, the AUV4 is placed in the retrieval cage 3, which clamps the AUV4.

[0046] The acoustic-optical guidance system 5 includes a communication sonar 501, a first underwater camera 502, a first guide light 503, a second underwater camera 504, and a second guide light 505. The communication sonar 501 is mounted on the second slewing joint 205. The first underwater camera 502 is mounted on the communication sonar 501. The first guide light 503 is mounted on the recovery cage 3. The second underwater camera 504 is mounted on the bow of the AUV4. The second guide lights 505 are mounted on the stern of the AUV4. There are two second guide lights 505 and four first guide lights 503. The first guide lights 503 and the second guide lights 505 are spaced apart.

[0047] The first guide light 503 and the second underwater camera 504 form a six-axis robotic arm vision guidance system, and the first underwater camera 502 and the second guide light 505 form an AUV vision guidance system.

[0048] A docking method for an underwater deployment and recovery AUV system using a robotic arm includes the following steps:

[0049] Step 1: Before the AUV4 is deployed, the six-axis robotic arm 2 retracts into the groove 101 of the recovery mother boat 1, and the opening and closing joint 206 of the six-axis robotic arm 2 drives the recovery cage 3 to clamp the AUV4.

[0050] Step 2: When deploying the AUV4 underwater, the six-axis robotic arm 2 adjusts the position of the recovery cage 3 and the AUV4, and the opening and closing joint 206 drives the recovery cage 3 to open, so that the recovery cage 3 no longer clamps the AUV4, thus completing the deployment of the AUV4.

[0051] Step 3: During the recovery of AUV4, the communication sonar 501 communicates with AUV4 and guides AUV4 to move to the vicinity of the recovery mothership 1. Then, the six-axis robotic arm vision guidance system and the AUV vision guidance system guide AUV4 for recovery.

[0052] In step three, the recovery mothership 1 remains hovered, and the AUV4 actively docks with the recovery cage 3. When the AUV4 is far from the recovery mothership 1, the communication sonar 501 communicates with the AUV4 and guides the AUV4 to move near the recovery mothership 1. At the same time, the six-axis robotic arm 2 extends downward, and the third pitch joint 204 and the second rotation joint 205 adjust the opening direction of the recovery cage 3 so that the opening direction of the recovery cage 3 is aligned with the bow direction of the AUV4. When the AUV4 moves near the recovery mothership 1, the guidance mode is switched to visual guidance mode. That is, the AUV4 uses the second underwater camera 504 mounted on the bow to identify the first guide light 503 on the recovery cage 3 to adjust the AUV4's attitude. The AUV4 enters the recovery cage 3 through its own thrusters, completing the recovery of the AUV4.

[0053] In step three, the recovery mothership 1 remains hovered, and the six-axis robotic arm 2 grabs the AUV4. The communication sonar 501 communicates with the AUV4 and guides the AUV4 to move below the recovery mothership 1 and within the reach of the six-axis robotic arm 2. The six-axis robotic arm 2 identifies the second guide light 505 on the back of the AUV4 through the first underwater camera 502. The six-axis robotic arm 2 drives the opening and closing joint 206 to open the recovery cage 3. The six-axis robotic arm 2 rotates each joint to grab the AUV4. After grabbing the AUV4, the six-axis robotic arm 2 retracts to the initial state, completing the recovery of the AUV4.

[0054] In step three, the mother vessel 1 remains in motion while the AUV4 actively docks with the recovery cage 3. When the AUV4 is far from the mother vessel 1, the communication sonar 501 communicates with the AUV4, sending the heading, speed, and position information of the mother vessel 1 to the AUV4. The AUV4 adjusts its speed and heading based on the information received and moves rapidly downwards from the mother vessel 1. When the AUV4 moves near the mother vessel 1, it still obtains the heading and speed information of the mother vessel 1 through the communication sonar 501. To reduce mutual interference when the AUV4 docks with the mother vessel 1, the six-axis robotic arm 2 extends downwards, and the recovery cage 3 maintains the same heading as the mother vessel 1. The AUV4 uses the second underwater camera 504 to identify the first guide light 503 to adjust its position and attitude. The AUV4 increases its speed and moves towards the center of the recovery cage 3. After the AUV4 enters the recovery cage 3, the six-axis robotic arm 2 retracts to its initial state, completing the recovery of the AUV4.

[0055] In step three, the recovery mothership 1 remains in motion while the six-axis robotic arm 2 grasps the AUV4. When the AUV4 is far from the recovery mothership 1, the communication sonar 501 communicates with the AUV4, sending the heading, speed, and position information of the recovery mothership 1 to the AUV4. The AUV4 adjusts its speed and heading based on the information received, quickly moving towards the reachable position of the six-axis robotic arm 2 of the recovery mothership 1. When the AUV4 moves near the recovery mothership 1, the AUV4 still obtains the heading and speed information of the recovery mothership 1 through the communication sonar 501 and keeps them basically consistent. The six-axis robotic arm 2 uses the first underwater camera 502 to identify the second guide light 505 on the AUV4 to determine the relative position error between the two, thereby driving each joint to grasp the AUV4. After grasping the AUV4, the six-axis robotic arm 2 retracts to its initial state, completing the recovery of the AUV4.

[0056] A combination of a six-axis robotic arm 2 grasping the AUV4 and the AUV4 actively docking with it enables multi-scenario and multi-mode deployment and retrieval of the AUV4. Specifically, in static docking scenarios, the six-axis robotic arm 2 grasps the AUV4 and actively docks with it; in dynamic docking scenarios, the six-axis robotic arm 2 grasps the AUV4 and actively docks with it. The design is simple, easy to operate, and has a high success rate. It reduces mutual interference between the two during retrieval, facilitating the rapid and safe deployment and retrieval of the AUV4.

[0057] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A robotic arm-based underwater deployment and recovery system for AUVs, characterized in that, include: Recover the mothership (1); Recovery cage (3) is set in the belly of recovery mother boat (1) and is used to clamp AUV (4). A six-axis robotic arm (2) is connected at one end to the recovery mother boat (1) and at the other end to the recovery cage (3). It is used to drive the recovery cage (3) to move and to open and close the recovery cage (3). The six-axis robotic arm (2) includes a first rotary joint (201), a first pitch joint (202), a second pitch joint (203), a third pitch joint (204), a second rotary joint (205), and an opening and closing joint (206). The first rotary joint (201) is connected to the first pitch joint (202), the first pitch joint (202) is connected to the second pitch joint (203), the second pitch joint (203) is connected to the third pitch joint (204), the third pitch joint (204) is connected to the second rotary joint (205), the second rotary joint (205) is connected to the opening and closing joint (206), and the opening and closing joint (206) is connected to the recovery cage (3). An acoustic-optical guidance system (5) is used to guide the AUV (4) to move towards the recovery mothership (1). The acoustic-optical guidance system (5) includes a communication sonar (501), a first underwater camera (502), a first guide light (503), a second underwater camera (504), and a second guide light (505). The communication sonar (501) is mounted on the second rotating joint (205), the first underwater camera (502) is mounted on the communication sonar (501), the first guide light (503) is mounted on the recovery cage (3), the second underwater camera (504) is mounted on the bow of the AUV (4), and the second guide light (505) is mounted on the back of the AUV (4). The first guide light (503) and the second underwater camera (504) form a six-axis robotic arm visual guidance system, and the first underwater camera (502) and the second guide light (505) form an AUV visual guidance system. Among them, the six-axis robotic arm (2) and the sound and light guidance system (5) can drive the recovery cage (3) to grab the AUV (4), and control the AUV (4) to actively dock with the recovery cage (3) through the sound and light guidance system (5).

2. The underwater deployment and recovery AUV system with a robotic arm as described in claim 1, characterized in that: The hull of the recovery mothership (1) is provided with a groove (101), and one end of the six-axis robotic arm (2) is located in the groove (101).

3. The underwater deployment and recovery AUV system with a robotic arm as described in claim 2, characterized in that: The recycling cage (3) consists of two arc-shaped recycling cages, which are rotated by the opening and closing joint (206).

4. A docking method for an underwater deployment and recovery AUV system using a robotic arm, comprising the underwater deployment and recovery AUV system as described in claim 1, characterized in that... Includes the following steps: Step 1: Before the AUV (4) is deployed, the six-axis robotic arm (2) retracts into the groove (101) of the recovery mother boat (1), and the opening and closing joint (206) of the six-axis robotic arm (2) drives the recovery cage (3) to clamp the AUV (4). Step 2: When the AUV (4) is deployed underwater, the position of the recovery cage (3) and the AUV (4) is adjusted by the six-axis robotic arm (2), and the opening and closing joint (206) drives the recovery cage (3) to open, so that the recovery cage (3) no longer clamps the AUV (4), and the deployment of the AUV (4) is completed. Step 3: When the AUV (4) is recovered, the communication sonar (501) communicates with the AUV (4) and guides the AUV (4) to move to the vicinity of the recovery mother ship (1). Then, the AUV (4) is guided and recovered by the six-axis robotic arm vision guidance system and the AUV vision guidance system.

5. The docking method for an underwater deployment and recovery AUV system using a robotic arm as described in claim 4, characterized in that: In step three, the recovery mothership (1) remains hovered, and the AUV (4) actively docks with the recovery cage (3). When the AUV (4) is far from the recovery mothership (1), the communication sonar (501) communicates with the AUV (4) and guides the AUV (4) to move to the vicinity of the recovery mothership (1). At the same time, the six-axis robotic arm (2) extends downward, and the third pitch joint (204) and the second rotation joint (205) adjust the opening direction of the recovery cage (3) so that the opening direction of the recovery cage (3) is aligned with the bow direction of the AUV (4). When the AUV (4) moves to the vicinity of the recovery mothership (1), the guidance mode is switched to visual guidance mode. That is, the AUV (4) uses the second underwater camera (504) mounted on the bow to identify the first guide light (503) on the recovery cage (3) to adjust the position and attitude of the AUV (4). The AUV (4) enters the recovery cage (3) through its own thruster to complete the recovery of the AUV (4).

6. The docking method for an underwater deployment and recovery AUV system using a robotic arm as described in claim 4, characterized in that: The mother ship (1) remains hovered, and the six-axis robotic arm (2) grabs the AUV (4). The communication sonar (501) communicates with the AUV (4) and guides the AUV (4) to move to the area below the mother ship (1) and within the reach of the six-axis robotic arm (2). The six-axis robotic arm (2) identifies the second guide light (505) on the back of the AUV (4) through the first underwater camera (502). The six-axis robotic arm (2) drives the opening and closing joint (206) to open the recovery cage (3). The six-axis robotic arm (2) rotates each joint to grab the AUV (4). After grabbing the AUV (4), the six-axis robotic arm (2) retracts to the initial state, completing the recovery of the AUV (4).

7. The docking method for an underwater deployment and recovery AUV system using a robotic arm as described in claim 4, characterized in that: The mother vessel (1) remains in motion, and the AUV (4) actively docks with the recovery cage (3). When the AUV (4) is far from the mother vessel (1), the communication sonar (501) communicates with the AUV (4), sending the heading, speed, and position information of the mother vessel (1) to the AUV (4). The AUV (4) adjusts its speed and heading according to the information received and moves quickly towards the area below the mother vessel (1). When the AUV (4) moves to the vicinity of the mother vessel (1), it still obtains information about the mother vessel (1) through the communication sonar (501). 1) Heading and speed information: In order to reduce the mutual interference between the AUV (4) and the recovery mother boat (1) during docking, the six-axis robotic arm (2) extends downwards, and the recovery cage (3) is aligned with the bow of the recovery mother boat (1); the AUV (4) uses the second underwater camera (504) to identify the first guide light (503) to adjust its position and attitude, and the AUV (4) increases its speed to move towards the center of the recovery cage (3). After the AUV (4) enters the recovery cage (3), the six-axis robotic arm (2) retracts to the initial state, and the recovery of the AUV (4) is completed.

8. The docking method for an underwater deployment and recovery AUV system using a robotic arm as described in claim 4, characterized in that: The mothership (1) remains in motion, and the six-axis robotic arm (2) grabs the AUV (4). When the AUV (4) is far from the mothership (1), the communication sonar (501) communicates with the AUV (4) and sends the heading, speed and position information of the mothership (1) to the AUV (4). The AUV (4) adjusts its speed and heading according to the information and moves quickly toward the reachable position of the six-axis robotic arm (2) of the mothership (1). When the AUV (4) moves to the reachable position of the mothership (1), the mothership (1) moves to the reachable position of the AUV (4). When near the mothership (1), the AUV (4) still obtains the heading and speed information of the mothership (1) through the communication sonar (501) and keeps them basically consistent; the six-axis robotic arm (2) identifies the second guide light (505) on the AUV (4) through the first underwater camera (502) to determine the relative position error between the two, thereby driving each joint to grab the AUV (4). After grabbing the AUV (4), the six-axis robotic arm (2) retracts to the initial state to complete the recovery of the AUV (4).

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