A buoy-based underwater dynamic docking method and system for an AUV

Abstract

The application belongs to the technical field of ocean engineering, and particularly relates to an AUV underwater dynamic docking method and system based on a buoy. The underwater docking device is connected with a constant tension winch through a zero buoyancy cable; a tension sensor is used for real-time monitoring of the tension of the zero buoyancy cable; a depth sensor is used for real-time monitoring of the depth of the underwater docking device; a posture motor is used for real-time adjustment of the pitch angle of the underwater docking device; an azimuth motor is used for real-time adjustment of the azimuth angle of the underwater docking device; and a control unit executes a PID algorithm to eliminate the influence of buoy heaving motion on the depth, posture and azimuth of the underwater docking device according to the feedback of the tension sensor and the depth sensor. The AUV underwater dynamic docking method and system based on the buoy eliminate the influence of buoy motion on the underwater docking device, improve the success rate of underwater dynamic docking, solve the endurance and communication problems of AUVs, and expand the observation range of the buoy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ocean engineering, and particularly relates to an AUV underwater dynamic docking method and system based on a buoy. BACKGROUND

[0002] The ocean data buoy (hereinafter referred to as a buoy) is a main means for marine environment monitoring in China at present, and can long-term, fixed-point, continuous, real-time and all-weather automatically observe marine hydrology and meteorology and various elements, serving marine forecast, disaster prevention and reduction, marine resource development, marine traffic and marine military activities. The buoy has energy supply modes such as solar panels, wind turbines, fuel cells and diesel generators, can carry large power loads, and realizes various observation tasks. The buoy floats on the water surface, and can communicate with the shore-based control center in real time through satellite communication, radio and mobile network and the like.

[0003] However, the buoy is anchored in a position through mooring cables, ropes, steel wires and the like, and has a small activity radius, and cannot realize large-scale marine observation. The existing buoy docking AUV scheme adopts a fixed docking dock installed at the bottom of the buoy or a mode of dragging a docking dock through a cable, has no active control strategy, and has a low docking success rate.

[0004] The AUV belongs to one kind of underwater robots, and is used for underwater observation and detection operation. Since there is no cable limitation, the AUV has a large activity range, a high intelligent control level and a significant concealed detection capability, and is more and more widely applied to various marine exploration activities.

[0005] However, the AUV itself carries limited energy, cannot complete energy supply by itself, needs to be guaranteed by other platforms, and a large amount of data collected by the AUV under water cannot be returned to other platforms through low-speed underwater acoustic communication, but can only be returned to a mother ship or docked with other platforms. The existing AUV recovery mainly adopts a scheme of docking with a fixed dock station on the sea bottom or being captured by an unmanned ship. The energy supply capacity of the fixed dock station on the sea bottom is limited, and cannot cover a large range of task areas. The communication capacity depends on expensive submarine cables, and is limited in popularization. The time efficiency of the unmanned ship capturing mode is not high, and cannot realize all-weather and all-sea-condition docking. The unmanned ship capturing mode is mainly suitable for the scene of recovering the AUV to the mother ship after the AUV operation, and cannot meet the scene demand of the AUV long-term guarding and regular task execution.

[0006] In view of the above advantages and disadvantages of the buoy and the AUV, the applicant proposes a combined development scheme, and finds that in addition to structure improvement and adaptive design, there is also a problem that the buoy is easily affected by sea waves, and the underwater docking device directly connected with the buoy is difficult to keep position stable, resulting in a low docking success rate. SUMMARY

[0007] To solve the problems in the prior art, the application provides an AUV underwater dynamic docking method and system based on a buoy.

[0008] The application solves the technical problems by adopting the following technical scheme: an AUV underwater dynamic docking system based on a buoy, comprising:

[0009] A main float body is located at the lower part of the buoy and has a disc shape.

[0010] A constant tension winch is fixedly installed in the main float body.

[0011] A zero buoyancy cable is wound on the constant tension winch.

[0012] An underwater docking device is connected to the constant tension winch through the zero buoyancy cable, and a cage-shaped structure for docking with an underwater AUV is arranged on the underwater docking device, and an optical guiding module is arranged at the front end of the cage-shaped structure.

[0013] A tension sensor is installed on the underwater docking device and used for monitoring the tension of the zero buoyancy cable in real time.

[0014] A depth sensor is installed on the underwater docking device and used for monitoring the depth of the underwater docking device in real time.

[0015] An attitude motor is used for adjusting the pitch angle of the underwater docking device in real time.

[0016] An azimuth motor is used for adjusting the azimuth angle of the underwater docking device in real time.

[0017] A control unit is internally provided with a PID algorithm, and is signal-connected with the constant tension winch, the tension sensor, the depth sensor, the azimuth motor and the attitude motor, and the control unit executes the PID algorithm to eliminate the influence of the buoy heave motion on the depth, attitude and azimuth of the underwater docking device according to the feedback of the tension sensor.

[0018] An energy unit provides power support for all devices of the system.

[0019] A communication unit is used for the communication connection between the control unit and a shore-based station.

[0020] Preferably, the constant tension winch comprises:

[0021] A power and execution unit is used for the winding and unwinding of the zero buoyancy cable.

[0022] A sensing unit comprises a tension sensor for monitoring the cable tension in real time and an encoder for accurately measuring the cable length and rotating speed.

[0023] A signal and energy transmission hub comprises an optical and electrical slip ring, and ensures that the power and communication signals are uninterruptedly transmitted to the zero buoyancy cable during the winding and unwinding of the winch.

[0024] The sub-control unit, based on a PLC or embedded controller, has a built-in PID control algorithm. It collects tension sensor signals in real time, filters them, compares them with the set tension value, and dynamically calculates control commands. The drive motor quickly compensates for the slack or tightness of the cable caused by the rise and fall of the buoy, so that the underwater docking device can maintain basic stability at the preset depth even in complex sea conditions.

[0025] Preferably, the underwater docking device includes: an electronics compartment, a V-shaped support frame, and a cage-like structure.

[0026] The top of the electronic compartment is connected to the zero-buoyancy cable, and a tension sensor is installed at the connection point to monitor the tension between the underwater docking device and the zero-buoyancy cable in real time. A depth sensor is installed at the bottom of the electronic compartment to provide real-time feedback on the depth of the underwater docking device.

[0027] The upper end of the A-frame is connected to the bottom of the electronic cabin via an orientation motor, and the lower end is connected to the two sides of the middle of the cage structure via two attitude motors.

[0028] Preferably, the main buoy is provided with a central moon pool; the underwater docking device is provided with an ultra-short baseline beacon; the underwater docking device has a built-in wireless charging module and a near-field communication module; the front end of the cage structure is a horn-shaped guide shroud, the front diameter of the guide shroud is larger than the rear diameter, and the optical guidance modules are evenly arranged circumferentially at the opening edge of the guide shroud.

[0029] A buoy-based underwater dynamic docking method for AUVs, implemented using the aforementioned system, includes the following steps:

[0030] S1. The buoy receives the relay request from the underwater AUV, performs preliminary positioning of the underwater AUV, and sends an instruction to the underwater AUV to start the relay mission.

[0031] S2. The underwater AUV advances to the vicinity of the buoy and hovers at the designated depth in the direction of the ocean current.

[0032] S3. The buoy control unit sends a command, and the constant tension winch starts to release the cable. The constant tension winch lowers the underwater docking device to the AUV's hovering depth according to the PID control algorithm. The guide cover of the cage structure is adjusted to face the AUV's direction by the azimuth motor and attitude motor, and the cage structure is kept in a horizontal position. The PID control algorithm uses the tension error of the tension sensor as input.

[0033] S4. The AUV advances to the optical visible range of the underwater docking device, operates in optical navigation mode, and slowly advances along the central axis of the cage structure, using the optical guidance module as a marker, until the AUV head is completely inside the cage structure, thus achieving docking.

[0034] Preferably, when the buoy rises and falls with the waves, the depth, attitude, and orientation of the underwater docking device are kept stable by maintaining a constant tension in the zero-buoyancy cable. A position-type PID controller is used to control the output. :

[0035] ;

[0036] ;

[0037] in, To control the output, the motor speed is used for the control of the constant tension winch; For tension error; The set tension value for the cable, in N; This represents the real-time tension value of the cable, in N. For proportional gain, response tension error, Values ​​range from 0.8 to 2.0; To achieve integral gain and eliminate steady-state error, Values ​​range from 0.05 to 0.2; Differential gain suppresses tension abrupt changes. The value ranges from 0.1 to 0.5; t represents time.

[0038] Preferably, the PID controller is configured with output limiting and anti-integral saturation.

[0039] Output limiting: , This represents the maximum positive value of the motor speed. This indicates the maximum reverse speed of the motor;

[0040] Using an integral separation strategy, when At that time, the points item is suspended. The integral separation threshold is the tension change.

[0041] Preferably, in order to cope with the periodic disturbance of ocean waves, a rapid response mechanism is established, with a real-time tension sampling frequency ≥50Hz, a control cycle ≤20ms, and a motor response delay ≤100ms;

[0042] To prevent AUV impacts or cable entanglement, a tension change rate limit is introduced to suppress sudden tension changes. If the threshold is exceeded, emergency braking or reverse cable retraction is triggered. Triggering conditions:

[0043] ;

[0044] in, This represents the real-time tension value at the current time t. For the previous moment The real-time tension value, To set the threshold for the rate of change of tension.

[0045] Preferably, Take 200N; The value is 1.2; The value is 0.1; The value is 0.3; the control cycle is 20ms. Take ±100N.

[0046] Preferably, to suppress high-frequency noise, the tension signal filtering strategy is as follows: first, a first-order low-pass filter, followed by a moving average filter; the low-pass filter coefficients... =0.2~0.3, cutoff frequency 5~10Hz, moving average window N=5~10.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] 1. This invention proposes an underwater dynamic docking system for AUVs based on buoys. By lowering the underwater docking device carried by the AUV to a designated depth and maintaining stability, the underwater docking device works with the AUV to control its attitude and orientation. The AUV uses its own power system to achieve dynamic docking with the underwater docking device. The underwater docking device provides the AUV with energy replenishment and communication relay services, and can also serve as a docking station for the AUV. This solves the problems of AUV endurance and communication, while also expanding the observation range of the buoys.

[0049] 2. This invention proposes a buoy-based underwater dynamic docking method for AUVs. The underwater docking device of the buoy is lowered to a specified depth, and a constant tension winch is used. Combined with a PID algorithm, the motor speed is dynamically adjusted in real time according to the tension response to eliminate the influence of the buoy movement on the underwater docking device, providing a stable dynamic docking platform for the AUV. By adjusting the orientation and attitude of the cage structure with dual motors, the success rate of underwater dynamic docking is improved.

[0050] 3. A combined filtering method is used to reduce noise during tension signal acquisition, ensuring that the acquired signal is true and effective, reducing the position error between the underwater docking device and the AUV, and facilitating rapid and accurate docking.

[0051] 4. The appearance of the buoy of this invention is not much different from that of a conventional operational buoy. All modules related to the AUV relay function are arranged inside the buoy, which has good concealment and camouflage.

[0052] 5. The AUV communicates with the buoy via underwater acoustics / near-field throughout the entire process, eliminating the risk of surfacing and exposure, reducing the probability of accidental salvage, and making it more suitable for covert detection scenarios. Attached Figure Description

[0053] Figure 1 This is a general diagram of an AUV underwater dynamic docking system based on buoys.

[0054] Figure 2 This is a schematic diagram of an underwater docking device.

[0055] Figure 3 This is a flowchart of the AUV underwater dynamic docking method in this invention.

[0056] Figure 4 This is a flowchart of the PID closed-loop control strategy for a constant tension winch.

[0057] Figure 5 This is the starting diagram of the AUV underwater dynamic docking in this invention.

[0058] Figure 6 This is a diagram of the underwater dynamic docking process of the AUV in this invention.

[0059] Figure 7 This is a diagram showing the completion of the underwater dynamic docking of the AUV in this invention.

[0060] In the diagram: 1. Main buoy, 2. Control room, 3. Observation platform, 4. Constant tension winch, 5. Zero buoyancy cable, 6. Underwater docking device, 7. Control unit, 8. AUV body.

[0061] 101. Buoyancy Chamber; 102. Ultra-short Baseline Positioning System; 103. Instrument Chamber; 104. Central Lunar Pool.

[0062] 201. Camera

[0063] 401. Tension sensor

[0064] 601. Electronic cabin; 602. A-frame support; 603. Cage structure; 604. Positioning beacon; 605. Depth sensor; 606. Azimuth motor; 607. Attitude motor; 608. Guide cover; 609. Optical guidance module; 610. Wireless charging module; 611. Near field communication module. Detailed Implementation

[0065] To facilitate understanding of the present invention, it will be described in more detail below with reference to the accompanying drawings and specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0066] Example: Combining Figure 1The buoy-based underwater dynamic docking system for AUVs includes: a buoy, mooring system, docking unit, power unit, communication unit, and control unit 7. The buoy mentioned here refers to a buoy that can be used as an AUV relay station, or simply a buoy. Structurally, from top to bottom, the buoy consists of an observation platform 3, an operating room 2, and a main buoy 1. It contains a docking unit for docking with the underwater AUV, which comprises a constant tension winch 4, a zero-buoyancy cable 5, and an underwater docking device 6. A detailed explanation follows:

[0067] 1. Main buoy 1: It is disc-shaped, with a buoyancy chamber 101 on its outer perimeter and a through-water well for installing an ultra-short baseline positioning system 102; an instrument chamber 103 is located inside, which is equipped with a constant tension winch 4 and a control unit 7; a central moon pool 104 is located in the middle, which allows the underwater docking device 6 to pass through the main buoy 1.

[0068] II. Operation Room 2: This room is equipped with an underwater docking device 6, which can dock with an AUV after submerging in water. It also contains a camera 201 for remotely monitoring the operational status of the equipment in Operation Room 2. An elastic material is installed in the central moon pool 104 at the bottom of Operation Room 2. When the underwater docking device 6 is retrieved into Operation Room 2, the deformation of this elastic material clamps and secures the device, preventing it from swaying and colliding with the buoy and causing damage.

[0069] 3. Observation Platform 3: The vertical poles of its fence are used to install observation instruments, communication equipment, security systems, and wind turbines, etc. Solar panels can also be installed on the plane of Observation Platform 3.

[0070] IV. Mooring: A single-point horizontal mooring method is adopted, consisting of an anchor, anchor chain, cable, float, etc. It is connected to the main buoy 1 through the horizontal mooring point on the side of the buoy. Under the action of ocean currents and waves, the buoy deflects in the opposite direction of the mooring to avoid interference with the zero buoyancy cable 5, underwater docking device 6 and AUV.

[0071] V. Constant Tension Winch 4: Integrated into the instrument compartment 103 of the main buoy 1, it is a closed-loop automatic control system. Its main components include:

[0072] Power and execution unit: Consists of a variable frequency motor, reducer and winch, responsible for launching and retrieving the zero buoyancy cable 5;

[0073] The core sensing unit includes a tension sensor 401 that monitors cable tension in real time and an encoder that accurately measures cable length and motor speed.

[0074] Signal and energy transmission hub: photoelectric slip rings ensure uninterrupted transmission of power and communication signals to the zero-buoyancy cable 5 during continuous winch rotation;

[0075] Intelligent Control Unit: Based on a PLC or embedded controller, with a built-in PID control algorithm. This unit acquires signals from the tension sensor 401 in real time, filters them, compares them with the set tension value, dynamically calculates control commands, and drives the motor to quickly compensate for cable slack or tightness caused by the buoy's rise and fall, thus enabling the underwater docking device 6 to maintain basic stability at the preset depth even in complex sea conditions. In addition, the constant tension winch 4 has sufficient pulling force to retrieve the underwater docking device 6 along with the AUV back into the buoy.

[0076] VI. Zero-buoyancy cable 5: Stored on the winch of the constant tension winch 4, the length can be set from 500 meters to 1000 meters according to the AUV docking requirements. The inner layer of the zero-buoyancy cable 5 is a cable for transmitting signals and energy, including optical fiber and power line; the middle layer is a tensile-resistant Kevlar fiber layer; and the outer layer is a polyurethane material that provides watertightness, pressure resistance, and abrasion resistance, providing energy and communication for the underwater docking device 6.

[0077] VII. Underwater docking device 6: mainly composed of an electronics compartment 601, a V-shaped support 602, and a cage-like structure 603. Its top is connected to the zero-buoyancy cable 5 and is equipped with a tension sensor 401 to monitor the tension between it and the zero-buoyancy cable 5 in real time. Combined with... Figure 2 understand.

[0078] The top of the electronics compartment 601 is equipped with an ultra-short baseline positioning beacon 604. The beacon obtains the real-time position of the underwater docking device 6 through the ultra-short baseline positioning system 102 installed below it. The electronics compartment 601 houses the control module, communication module, and power supply module of the underwater docking device 6, which are electrically connected to other components through watertight connectors. The bottom of the electronics compartment 601 is equipped with a depth sensor 605, which can provide real-time feedback on the depth of the underwater docking device 6. The depth sensor 605 directly acquires the depth of the underwater docking device 6 and notifies the AUV to be docked of the depth value.

[0079] The upper end of the A-frame bracket 602 is connected to the bottom of the electronics compartment 601 via an orientation motor 606, and the lower end is connected to both sides of the middle section of the cage structure 603 via two attitude motors 607. The orientation motor 606 allows the A-frame bracket 602 to rotate in the horizontal plane, thereby adjusting the orientation of the cage structure 603 so that its opening is aligned with the direction of the AUV's approach. The attitude motors 607 adjust the attitude of the cage structure 603 to keep its centerline horizontal.

[0080] The front of the cage structure 603 is a flared guide shield 608, with a larger diameter than the rear. The guide shield 608 has circumferentially distributed optical guidance modules 609 along its opening edge to assist the AUV's optical navigation system, ensuring the AUV aligns with its central axis as it approaches the guide shield 608, thus increasing the success rate of the AUV entering the cage structure 603. The middle of the cage structure 603 features symmetrically arranged wireless charging modules 610 and near-field communication modules 611 for energy replenishment and near-field communication after AUV docking. An underwater camera is located at the rear central axis of the cage structure 603 to observe the relative position of the AUV and the underwater docking device 6 during docking. Buoyancy materials are provided at both the front and rear of the cage structure 603 to balance its own weight, maintaining a zero-gravity state in the water.

[0081] When the underwater docking device 6 is not in operation, the cage-like structure 603 is switched to a vertical position by rotating the A-frame support 602, and is then retrieved and fixed inside the operating room 2, above the water surface in the central moon pool 104, to prevent marine organisms from attaching. Figure 5 As shown; during operation, it is lowered into the water through the central moon pool 104. The weight of the electronic cabin 601 is much greater than the buoyancy, and the cage structure 603 has zero gravity. By adjusting the attitude motor 607 of the A-frame support 602, it is switched to a horizontal state, and the constant tension winch 4 is used to reach the designated depth and maintain stability, thus completing the docking task with the AUV.

[0082] 8. Energy Unit: Providing power support for all equipment in the system, this unit is integrated into the observation platform 3, main buoy 1, and other components. It primarily includes modules such as solar panels, wind turbines, fuel cells, batteries, and a power controller. The energy unit captures wind and solar energy from the marine environment through wind turbines and solar panels, storing the energy in the battery bank. The fuel cell compensates for the dependence of the solar panels and wind turbines on environmental conditions, serving as an emergency and supplementary energy source. Furthermore, when charging the AUV, the fuel cell automatically starts, increasing energy replenishment power and efficiency, reducing AUV docking time, and meeting the AUV's emergency energy replenishment needs. The power controller integrates multiple power generation methods, intelligently allocating the energy system's discharge and power generation to improve energy utilization efficiency.

[0083] 9. Control Unit 7: Installed inside the instrument compartment 103 of the buoy, it is electrically connected to the constant tension winch 4, underwater docking device 6, communication unit, and observation instruments, and serves as the control center of the entire system. It is responsible for tasks such as collecting data from other units, sending control commands to other units, and transmitting packaged data to the communication unit.

[0084] 10. Communication Unit: Integrated into the observation platform 3, mainly including Beidou communication unit, Tiantong satellite communication unit or other available narrowband low-orbit satellite communication unit, directly connected to the control unit 7, transmitting the data packaged and processed by the control unit 7 back to the shore base station, and receiving control commands sent by the shore base station and transmitting them to the control unit 7.

[0085] A buoy-based underwater dynamic docking method for AUVs is proposed, implemented based on the aforementioned buoy docking system, with the docking process combined with... Figures 1-7 The proposed AUV is understood in reference to AUV body 8 in the figure. The specific implementation method is as follows:

[0086] Step 1: When the AUV completes its mission, runs out of power, or needs to upload the collected data, the AUV establishes communication with a nearby buoy through its own underwater acoustic beacon and sends a relay request to the buoy.

[0087] Step 2: The buoy receives the relay request from the AUV through the ultra-short baseline positioning system 102 installed on its bottom and initially locates the AUV. The control unit 7 first checks the buoy's own status, including the communication link status, power status, and underwater docking device 6 status. If the AUV relay requirements are met, the buoy sends information through the ultra-short baseline positioning system 102 to inform the AUV to start the relay task.

[0088] Step 3: The AUV, guided by the buoy ultra-short baseline positioning system 102, advances to the waters near the buoy using its own power and hovers at the designated depth in the direction of the ocean current, waiting for the underwater docking device 6 to be in place.

[0089] Step Four: The buoy control unit 7 sends a command, the constant tension winch 4 starts working, executes the cable-laying procedure, unlocks the underwater docking device 6, and the underwater docking device 6 enters the water through the central moon pool 104 under its own gravity. Figure 6 As shown.

[0090] Step 5: The constant tension winch 4 continues to lay the cable, and the underwater docking device 6 reaches the AUV's hovering depth. Based on the AUV's hovering position, adjust the guide shield 608 of the cage structure 603 to face the AUV's direction, and maintain the cage structure 603 in a horizontal position. (Refer to...) Figure 1 understand.

[0091] Step Six: The tension sensor 401 is used to detect the real-time tension in the zero-buoyancy cable 5, and the constant tension winch 4 is used to perform sliding average processing on the real-time tension curve to obtain the set tension of the underwater docking device 6 under this environment. According to the real-time tension change, the constant tension device uses PID control technology to adjust the length and speed of the zero-buoyancy cable 5 of the constant tension winch 4 in real time, thereby blocking the influence of the buoy moving with the waves on the underwater docking device 6, so that the underwater docking device 6 maintains basic stability in depth, attitude and orientation.

[0092] The PID control in this method mainly aims to stabilize the tension in the cable. The depth of the underwater docking device 6 is roughly determined by the cable length of the constant tension winch 4. As long as the depth remains stable, the AUV docking requirements can be met.

[0093] The specific implementation plan for the constant tension winch 4 and the underwater docking device 6 is as follows:

[0094] 1. The core objective of constant tension control is to maintain a constant tension on the zero-buoyancy cable 5 of the underwater docking device 6 while the buoy is rising and falling with the waves, thereby ensuring its depth, attitude and orientation stability, and providing a stable and reliable docking platform for the AUV.

[0095] 2. System composition and signal flow:

[0096] The tension sensor collects the tension value of the zero-buoyancy cable 5 in real time (sampling frequency ≥ 50Hz).

[0097] The signal conditioning module amplifies, filters, and denoises the tension signal;

[0098] The PID controller calculates the motor control quantity based on the tension error;

[0099] The motor driver drives the constant tension winch to rotate forward / reverse / brake using four motors.

[0100] The encoder provides real-time feedback on the winch rotation angle and cable length.

[0101] 3. PID control algorithm design:

[0102] (1) Definition of control variables

[0103] The set tension value of the cable: (Unit: N);

[0104] Real-time tension value of the cable: (Unit: N);

[0105] Tension error: t is time;

[0106] Control output: The motor speed is used for the control of the constant tension winch.

[0107] (2) PID control law

[0108] Employ a positional PID controller:

[0109] ;

[0110] in, : Proportional gain, response tension error (recommended range: 0.8~2.0);

[0111] Integral gain, to eliminate steady-state error (recommended range: 0.05~0.2);

[0112] Differential gain, to suppress tension abrupt changes (recommended range: 0.1~0.5);

[0113] , and Based on on-site commissioning experience, different ocean currents and waves require different setting parameters. Ocean currents affect the stress on the underwater docking device, while waves affect the movement of the surface buoy.

[0114] (3) Output limiting and anti-integral saturation

[0115] Output limiting: , This represents the maximum positive value of the motor speed. This indicates the maximum reverse speed of the motor.

[0116] Anti-integral saturation: Employs an integral separation strategy when At that time, the points item is suspended. The integral separation threshold is the tension change.

[0117] 4. Tension Real-Time Response Mechanism (Dynamic Response Design):

[0118] (1) Rapid response mechanism (to deal with wave cycle disturbances)

[0119] Sampling frequency: ≥50Hz (to ensure response to wave disturbances with a period of 2~20s);

[0120] Control period: ≤20ms;

[0121] Motor response delay: ≤100ms (using servo motor + encoder closed loop).

[0122] (2) Suppression of sudden tension changes (to prevent AUV impact or cable entanglement)

[0123] Introducing a limit on the rate of change of tension:

[0124] ;

[0125] If the set tension change rate threshold is exceeded Triggering emergency braking or reverse cable retraction, triggering conditions:

[0126] ;

[0127] in, This represents the real-time tension value at the current time t. For the previous moment The real-time tension value.

[0128] 5. Tension signal filtering strategy (suppressing high-frequency noise):

[0129] (1) Moving Average Filtering:

[0130] ;

[0131] This is the real-time tension value after being filtered by the moving average.

[0132] Moving average filtering smooths noise by averaging N historical data. The larger N is, the better the filtering effect, but the greater the signal delay. The recommended moving average window is N=5~10. This value is a trade-off between noise suppression and response speed, effectively filtering high-frequency noise from the sensor without significantly affecting the system's real-time performance.

[0133] (2) Low-pass filter (first order IIR):

[0134] ;

[0135] The real-time tension value after IIR first-order low-pass filtering; recommended low-pass filter coefficients: =0.2~0.3 (cutoff frequency about 5~10Hz), mainly used to filter high-frequency noise in real-time tension values. This value can maintain the accuracy of real-time tension values ​​and truly reflect the changes in real-time tension values.

[0136] (3) Combined filtering strategy:

[0137] First, use an IIR low-pass filter, then a moving average, and finally input it into the PID controller.

[0138] 6. Typical control parameters

[0139] Table 1 Typical Control Parameters

[0140]

[0141] 7. Expected technical effects

[0142] Under sea conditions with a buoy heave amplitude of ±0.5m and a period of 4s, tension fluctuations can be controlled within ±50N; during AUV docking, the depth drift of the underwater docking device is <±0.1m, and the attitude angle change is <±5°.

[0143] Step 7: If the constant tension winch 4's PID control fails to achieve the expected stability, the constant tension winch 4 adjusts the depth of the underwater docking device 6 by reeling in and out the cable to find a more stable seawater environment. The constant tension winch 4 then performs PID control again until the underwater docking device 6 achieves stability. The location of the underwater docking device 6 is obtained using the ultra-short baseline positioning system 102 at the bottom of the buoy and its carried acoustic beacon, and this location information is forwarded to the AUV.

[0144] Step 8: Based on its own positioning information and the positioning information of the underwater docking device 6, the AUV formulates an acoustic navigation route and slowly moves towards the vicinity of the underwater docking device 6.

[0145] Step 9: When the AUV moves into the optical visible range of the underwater docking device 6, switch to optical navigation mode. The underwater docking device 6 uses its own camera to obtain the AUV's orientation, attitude and depth, and further precisely adjusts the orientation, attitude and depth of the cage structure 603 so that the central axis of the AUV is basically parallel to the central axis of the cage structure 603 and is within the range of the guide cover 608.

[0146] Step 10: The AUV uses optical navigation, guided by the optical guidance modules 609 around the guide shroud 608, to slowly advance along the central axis of the cage structure 603, ultimately allowing the AUV head to fully enter the cage structure 603, completing the AUV docking. Figure 7 As shown.

[0147] Step 11: After the underwater docking device 6 completes docking with the AUV, according to the relay mission requirements, it uses the wireless charging module and near-field communication module inside the underwater docking device 6 to dock with the corresponding charging and communication positions of the AUV to complete the AUV's energy replenishment and data transmission.

[0148] Step 12: After completing the AUV relay mission, the wireless charging module and near-field communication module of the underwater docking device 6 retract, the limiting mechanism unlocks, and the underwater docking device 6 uses its own power to slowly retreat along the central axis of the AUV until the AUV is completely detached from the horn-shaped structure 603. The underwater docking device 6 is then retrieved into the buoy operation room 2 using the constant tension winch 4 (e.g., Figure 5As shown), the buoy sends a relay mission completion command to the AUV via underwater acoustic communication, and the AUV can leave on its own and continue to perform other tasks; or, the constant tension winch 4 retrieves the underwater docking device 6 together with the AUV into the buoy for temporary docking. When performing the mission again, the AUV and the underwater docking device 6 are lowered into the water using the constant tension winch 4, and the same operation is performed to complete the AUV relay mission.

[0149] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.

Claims

1. A buoy-based AUV underwater dynamic docking system, characterized in that, include: The main buoy, located at the bottom of the buoy, is disc-shaped; A constant tension winch is fixedly installed in the main float. Zero-buoyancy cable, which is wound on a constant-tension winch; The underwater docking device is connected to a constant tension winch via a zero-buoyancy cable. The underwater docking device is equipped with a cage-like structure for docking with an underwater AUV. An optical guidance module is located at the front end of the cage-like structure. Tension sensor, which is installed on the underwater docking device, is used to monitor the tension of the zero-buoyancy cable in real time; A depth sensor, which is installed on the underwater docking device, is used to monitor the depth of the underwater docking device in real time; Attitude motors are used to adjust the pitch angle of the underwater docking device in real time. Azimuth motor is used to adjust the azimuth angle of the underwater docking device in real time; The control unit has a built-in PID algorithm and is connected to the constant tension winch, tension sensor, depth sensor, azimuth motor and attitude motor. The control unit executes the PID algorithm based on the feedback from the tension sensor to eliminate the influence of the buoy's heave motion on the depth, attitude and azimuth of the underwater docking device. The energy unit provides power to all equipment in the system; The communication unit is used to control the communication connection between the control unit and the shore base station; A constant tension winch includes: Power and actuation unit for deploying and retrieving zero-buoyancy cables; The sensing unit includes a tension sensor for real-time monitoring of the tension of the zero-buoyancy cable and an encoder for precise measurement of cable length and rotational speed. The signal and energy transmission hub includes photoelectric slip rings to ensure uninterrupted transmission of power and communication signals to the zero-buoyancy cable during winch cable deployment and retrieval. The sub-control unit, based on a PLC or embedded controller, has a built-in PID control algorithm. It collects tension sensor signals in real time, filters them, compares them with the set tension value, dynamically calculates control commands, and drives the motor of the constant tension winch to quickly compensate for the slack or tightness of the zero buoyancy cable caused by the rise and fall of the buoy. This allows the underwater docking device to maintain basic stability at the preset depth even in complex sea conditions. The main buoy is equipped with a central moon pool; the underwater docking device is equipped with an ultra-short baseline beacon; the underwater docking device has a built-in wireless charging module and a near-field communication module; the front end of the cage structure is a horn-shaped guide dome, the diameter of the front end of the guide dome is larger than the diameter of the rear end, and the optical guidance modules are evenly arranged circumferentially at the opening edge of the guide dome.

2. The buoy-based AUV underwater dynamic docking system according to claim 1, characterized in that, The underwater docking device includes: an electronics compartment, an A-frame support, and a cage-like structure. The top of the electronic compartment is connected to the zero-buoyancy cable, and a tension sensor is installed at the connection point to monitor the tension between the underwater docking device and the zero-buoyancy cable in real time. A depth sensor is installed at the bottom of the electronic compartment to provide real-time feedback on the depth of the underwater docking device. The upper end of the A-frame is connected to the bottom of the electronic cabin via an orientation motor, and the lower end is connected to the two sides of the middle of the cage structure via two attitude motors.

3. A buoy-based underwater dynamic docking method for AUVs, characterized in that, The system described in any one of claims 1-2 is implemented by including the following steps: S1. The buoy receives the relay request from the underwater AUV, performs preliminary positioning of the underwater AUV, and sends an instruction to the underwater AUV to start the relay mission. S2. The underwater AUV advances to the vicinity of the buoy and hovers at the designated depth in the direction of the ocean current. S3. The buoy control unit sends a command, and the constant tension winch starts to release the cable. The constant tension winch lowers the underwater docking device to the AUV's hovering depth according to the PID control algorithm. The guide cover of the cage structure is adjusted to face the AUV's direction by the azimuth motor and attitude motor, and the cage structure is kept in a horizontal position. The PID control algorithm uses the tension error of the tension sensor as input. S4. The AUV advances to the optical visible range of the underwater docking device, operates in optical navigation mode, and slowly advances along the central axis of the cage structure, using the optical guidance module as a marker, until the AUV head is completely inside the cage structure, thus achieving docking.

4. The buoy-based underwater dynamic docking method for AUVs according to claim 3, characterized in that, When the buoy rises and falls with the waves, the underwater docking device maintains a constant tension in the zero-buoyancy cable to ensure its depth, attitude, and orientation stability. A position-type PID controller is used to control the output. : ； ； in, To control the output, it is the motor speed of the constant tension winch, used for the control of the constant tension winch; For tension error; The set tension value for the zero-buoyancy cable, in N; Real-time tension value of the zero-buoyancy cable, unit: N; For proportional gain, response tension error, Values ​​range from 0.8 to 2.0; To achieve integral gain and eliminate steady-state error, Values ​​range from 0.05 to 0.2; Differential gain, suppressing tension abrupt changes. The value ranges from 0.1 to 0.5; t represents time.

5. The buoy-based underwater dynamic docking method for AUVs according to claim 4, characterized in that, In a PID controller, output limiting and anti-integral saturation settings are configured. Output limiting: , This represents the maximum positive speed of the constant tension winch motor. This indicates the maximum reverse rotational speed of the constant tension winch motor; Using an integral separation strategy, when At that time, the points item is suspended. The integral separation threshold is the tension change.

6. The buoy-based underwater dynamic docking method for AUVs according to claim 4, characterized in that, To cope with the periodic disturbances of ocean waves, a rapid response mechanism is established, with a real-time tension sampling frequency ≥50Hz, a control cycle ≤20ms, and a motor response delay of ≤100ms for the constant tension winch; To prevent AUV impacts or cable entanglement in zero-buoyancy environments, a tension change rate limit is introduced to suppress sudden tension changes. If the threshold is exceeded, emergency braking or reverse cable retraction is triggered. Triggering conditions: ； in, This represents the real-time tension value at the current time t. For the previous moment The real-time tension value, To set the threshold for the rate of change of tension.

7. The buoy-based underwater dynamic docking method for AUVs according to claim 6, characterized in that, Take 200N; The value is 1.2; The value is 0.1; The value is 0.3; the control cycle is 20ms. Take 100N.

8. The buoy-based underwater dynamic docking method for AUVs according to claim 4, characterized in that, To suppress high-frequency noise, the tension signal filtering strategy is as follows: first, a first-order low-pass filter, followed by a moving average filter; the low-pass filter coefficients... =0.2~0.3, cutoff frequency 5~10Hz, moving average window N=5~10.

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