Mother ship, unmanned ship and unmanned ship recovery method

Abstract

The invention discloses a mother ship, an unmanned ship and an unmanned ship recovery method. The method comprises the following steps: a far-end navigation task: planning a first reference path from an unmanned ship to a mother ship under a global navigation satellite system, and controlling the unmanned ship to track the first reference path by combining an ASAC-LOS guidance algorithm with a PID controller, so that the unmanned ship approaches the mother ship; a local relative coordinate system is constructed based on the relative distance and orientation between the unmanned ship and the mother ship, a second reference path with steering angle constraint is planned under the local relative coordinate system, and the unmanned ship is controlled to move along the second reference path by using an ASAC-LOS guidance algorithm in combination with a PID controller and is aligned with a traction steel wire rope on the mother ship; and a recovery control task: under the local relative coordinate system, an ASAC-LOS guidance algorithm is combined with a PID controller to control the unmanned ship to sail to the mother ship along a linear path, the unmanned ship is connected to a traction steel wire rope on the mother ship, and recovery is completed.

Description

Technical Field

[0001] The present invention relates to the recovery technology of unmanned boats. Background Art

[0002] With the continuous development of unmanned boat technology, its applications in fields such as ocean exploration, environmental monitoring, and maritime transportation are increasing day by day, and the autonomous operation ability has become a key factor in improving efficiency and safety. Especially in the collaborative operation between an unmanned boat and a mother ship, the recovery technology is particularly important.

[0003] Traditional automatic recovery methods using a stern chute, as described in the patent document CN115903809A, have obvious limitations. This method requires the precise alignment of the unmanned boat and the stern chute, but it is difficult and risky to achieve this operation in a high-sea state environment. Even a small deviation in the bow direction or position may lead to the failure of recovery, and in severe cases, it may cause a violent collision between the unmanned boat and the mother ship, resulting in safety accidents.

[0004] In addition, the current path planning methods based on inertial navigation and visual recognition have limited adaptability in complex environments and severe sea conditions, facing certain technical challenges. For example, under the conditions of large waves and strong winds, it is difficult for these navigation and control systems to ensure that the unmanned boat can safely and efficiently return to the stern chute of the mother ship, and it is easily affected by sea surface fluctuations, wind and wave changes, and the position deviation of the mother ship.

[0005] Therefore, how to achieve seamless switching between long-distance navigation and short-distance navigation and ensure precise control during the recovery process has become a key technical problem in the field of unmanned boat recovery. Summary of the Invention

[0006] The present invention provides a mother ship, an unmanned boat, and an unmanned boat recovery method, aiming to solve the problems of low recovery efficiency, insufficient safety, and poor adaptability to complex environments existing in the existing unmanned boat recovery technology.

[0007] First aspect, an unmanned boat recovery method, comprising: Remote navigation task: Plan a first reference path from the current position of the unmanned boat to the current position of the mother ship under the global navigation satellite system, and use the adaptive sideslip angle compensation line-of-sight method combined with a PID controller to control the unmanned boat to track the first reference path, so that the unmanned boat approaches the mother ship; Proximal navigation task: When the unmanned boat approaches the mother ship and is less than a specific distance La from the mother ship, start the proximal navigation task. In this task, a local relative coordinate system is constructed based on the real-time relative distance and azimuth between the unmanned boat and the mother ship to assist navigation. A second reference path with a steering angle constraint is planned in this local relative coordinate system, and the adaptive sideslip angle compensation line-of-sight method combined with a PID controller is continued to control the unmanned boat to move along the second reference path and align with the towing wire rope on the mother ship; Recovery control task: When the unmanned boat gets closer to the mother ship and reaches a specific distance Lb behind it, enter the recovery control task. In this task, continue to use the adaptive sideslip angle compensation line-of-sight method combined with a PID controller in the local relative coordinate system to control the unmanned boat to drive along a straight path towards the mother ship and connect to the towing wire rope on the mother ship, thus completing the recovery.

[0008] In some examples, in the remote navigation task, proximal navigation task, and recovery control task, the method of using the adaptive sideslip angle compensation line-of-sight method combined with a PID controller to control the unmanned boat includes: dividing the first reference path, the second reference path, and the straight path into n reference path points P1(x1, y1), P2(x2, y2), ……, P n (x n ,y n ) connected to form n - 1 reference navigation segments. Each reference navigation segment is composed of a starting point P i (x i ,y i ) and an end point P i+1 (x i+1 ,y i+1 ), where i ≤ n - 1; constructing a guidance circle with the current position P USV of the unmanned boat and a radius R LOS ; using the intersection point of the guidance circle and the reference navigation segment P i P i+1 as the virtual target point; calculating the expected heading angle ψ LOS that the unmanned boat should adopt according to the position of the virtual target point; calculating the expected heading ψ d according to formula (1):

[0009] ψ d = ψ p - ψ LOS - (a + b·V w sin(Δψ pw ))βs (1)

[0010] In the formula, ψ p is the direction from P i to P i+1 in the current reference course segment, and ψ LOS is the desired course angle; a and b are weight coefficients used to adjust the compensation intensity; V w is the wind speed; Δψ pw is the angle between the reference course segment direction ψ p and the wind direction β w ; β s is the measured sideslip angle.

[0011] The PID controller is configured to receive the calculated desired course ψ d and the desired speed set by the user, analyze the deviations between the actual course and speed and the desired course ψ d and the desired speed, and control and adjust the course and speed of the unmanned boat to reduce the deviations and ensure that the unmanned boat sails along the first reference path, the second reference path, and the straight-line path.

[0012] In some examples, the radius R LOS of the guidance circle is 5 to 10 times the length of the unmanned boat.

[0013] In some examples, the Theta* algorithm is used to plan the first reference path.

[0014] In some examples, the TAC-Theta* algorithm is used to plan the second reference path.

[0015] In some examples, the turning angle in the second reference path is greater than 135 degrees.

[0016] In a second aspect, an unmanned boat that can be recovered to a mother ship by applying the unmanned boat recovery method described above.

[0017] In some examples, a buckle for hooking a towing steel wire rope on the mother ship is provided at the front end of the unmanned boat.

[0018] In some examples, the buckle includes a body and a rotating member. The body encloses a three-sided closed structure, and the rotating member is located on the open side of the body. When the rotating member is hit by the towing steel wire rope, it rotates towards the body, thereby opening the opening to allow the towing steel wire rope to enter; subsequently, the rotating member will automatically rebound to re-close the opening to ensure that the towing steel wire rope is locked.

[0019] Third aspect, a mother ship, which is capable of providing real-time relative distance and azimuth information between it and the unmanned boat during proximal navigation tasks.

[0020] In some examples, a recovery channel and a drive system are provided at the stern of the mother ship. The drive system is capable of driving the traction steel wire rope to move, and pulling the unmanned boat hanging on it back into the recovery channel.

[0021] In some examples, the drive system includes: two chains and their matching sprockets. The two chains are installed in parallel on both sides of the recovery channel and are respectively connected to both ends of the traction steel wire rope spanning the recovery channel; a cage, which is configured to support the two chains and the matching sprockets. The cage is provided with side openings to enable the smooth movement of the traction steel wire rope. The cage includes a main body part and an extension part. The main body part is located inside the recovery channel, and the extension part can extend outside the recovery channel when unfolded. The main body part and the extension part are connected by a hinge; a telescopic member, which connects the hull of the mother ship and the extension part of the cage, and is used to retract the extension part into the recovery channel or unfold it to extend outside the recovery channel, so as to adjust the height of the traction steel wire rope relative to the water surface; and a motor, which is configured to drive the two chains to move synchronously, and pull the unmanned boat into the recovery channel through the traction steel wire rope. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the unmanned boat recovery process.

[0023] Figure 2 It depicts the process of how the unmanned boat gradually approaches the mother ship when performing a distal navigation task.

[0024] Figure 3 It is the working principle diagram of the ASAC-LOS guidance law algorithm.

[0025] Figure 4 It is a schematic diagram of the proximal navigation and recovery process of the unmanned boat.

[0026] Figure 5 It is the schematic diagram of the combined use of the path planning algorithm, the ASAC-LOS guidance algorithm and the PID controller.

[0027] Figure 6 It is the situation where the unmanned boat approaches the mother ship and is ready for controlled recovery after completing the proximal navigation task.

[0028] Figure 7 It is the layout schematic diagram of the recovery channel at the stern of the mother ship and its related recovery equipment.

[0029] Figure 8It is a view of the installation method of the head buckle of the unmanned boat.

[0030] Figure 9 It is a schematic diagram of the connection between the buckle at the front end of the unmanned boat and the towing steel wire rope on the mother ship.

[0031] Figure 10 It is a schematic diagram of the equipment configuration on the mother ship for recovering the unmanned boat.

[0032] Figure 11 It is a schematic diagram of the multi-angle docking between the towing steel wire rope of the mother ship and the unmanned boat.

[0033] Figure 12 It is a schematic diagram of the operation of the buckle and the towing steel wire rope used in combination. Detailed implementation manners

[0034] The recovery process of the unmanned boat includes three stages: remote navigation, proximal navigation, and controlled recovery. Figure 1 These three stages are shown and will be described in detail below.

[0035] S1. Remote navigation

[0036] During the process of the unmanned boat performing the remote navigation task, its main goal is to approach the mother ship. To achieve this goal, a global navigation satellite system (such as GPS, GLONASS, Galileo, or Beidou, etc.) is used to create a detailed geographic information database model and construct a global geodetic coordinate system to provide a high-precision position reference. For path planning, one of various advanced algorithms can be adopted, such as but not limited to the Theta* algorithm, depending on the specific task requirements and environmental conditions. These algorithms can calculate an optimal or near-optimal safe route in a complex marine environment. As for path tracking control, a technical solution combining the Adaptive Side-slip Angle Compensation Line-of-Sight (ASAC-LOS) and a PID controller is adopted. This method can not only ensure that the unmanned boat accurately follows the predetermined route but also compensate for the side-slip influence caused by factors such as ocean currents and wind forces through real-time adjustment, thereby ensuring the accuracy and stability of the navigation trajectory.

[0037] As Figure 2As shown in the figure, the geographic information database model includes the following elements: First, construct a global north-east coordinate system (i.e., a geodetic coordinate system based on the north and east directions). In this coordinate system, determine the current position of the unmanned boat 200 and set it as the starting point of remote navigation. At the same time, locate the current position of the mother ship 100 and set it as the target point of remote navigation. In addition, identify and record the outer closed shape of all obstacles 300 on the path. It should be noted that the positions of the unmanned boat 200 and the mother ship 100 are dynamically changing, and their position information is automatically updated every set time (for example, 1 second) to ensure the accuracy and real-time nature of navigation.

[0038] In the remote recovery stage, there are not high requirements for the position and attitude control of the unmanned boat. The key is to be able to quickly find the shortest path from the current position around the obstacles to the mother ship.

[0039] The Theta* algorithm has good real-time performance and high computational efficiency. It optimizes the traditional A* algorithm, can propagate information along the grid edges, and at the same time does not limit the path to the grid edges, thus allowing path planning at any angle. By implementing direct line-of-sight checks between nodes, the Theta* algorithm can directly connect any two nodes that are unobstructed within the line of sight. The flexible parent node selection mechanism of the Theta* algorithm enables it to find a shorter and straighter path than the traditional A* algorithm, greatly improving the efficiency of remote navigation.

[0040] In the geographic information database model, based on the existing position data, the Theta* algorithm is used to calculate an optimal path (the first reference path) from the current position of the unmanned boat (starting point) to the current position of the mother ship (target point). Although the position information of the mother ship and the unmanned boat obtained through the Beidou Satellite Navigation System (BDS) or other global navigation satellite systems is dynamically changing, by running the Theta* algorithm in real time, this path can be continuously updated to ensure that the unmanned boat can continuously adjust its navigation route according to the latest position information, so as to effectively approach the mother ship.

[0041] Preferably, first divide the reference path calculated by the Theta* algorithm into n - 1 reference navigation segments connected by n reference path points P1(x1, y1), P2(x2, y2), ……, P n (x n , y n ). Each reference navigation segment is composed of a starting point P i (x i , y i ) and an end point P i+1 (x i+1 , y i+1 ), where i ≤ n - 1, and record the current position information of the unmanned boat in real time.

[0042] Next, based on the relative position relationship between the unmanned boat and the current reference path, a virtual target point P is selected. LOS (x LOS , y LOS ). Selecting an appropriate virtual target point is one of the key steps to achieve accurate path tracking. This virtual target point is usually located at an ideal position in front of the unmanned boat, and it represents the target direction that the unmanned boat should face in the next stage. Specifically, the virtual target point is the intersection of the guidance circle and the reference path segment P i P i+1 , and the center of the guidance circle is the current position P of the unmanned boat USV , with a radius of R LOS , and R LOS is 5 - 10 times the length of the unmanned boat.

[0043] Then, according to the position of the selected virtual target point, the desired heading angle ψ LOS of the unmanned boat is calculated. This desired heading angle defines the direction that the unmanned boat needs to adjust in order to approach the virtual target point.

[0044] In addition, considering that in actual operation, the unmanned boat may encounter side - slip phenomena (lateral drift) caused by external factors such as ocean currents or wind, that is, there may be a deviation / angle (side - slip angle β s ) between the actual movement direction (velocity direction) of the unmanned boat and its heading (the direction pointed by the bow). Therefore, it is necessary to dynamically adjust the side - slip angle to effectively correct the heading of the unmanned boat so that it follows the predetermined path more closely.

[0045] The ASAC - LOS guidance algorithm can effectively transform the path - tracking problem into a heading - angle tracking problem in the distal navigation stage. This algorithm is used to compensate for the side - slip phenomenon encountered by the unmanned boat during navigation. By calculating and compensating the side - slip angle of the unmanned boat in real - time, the heading error caused by these external interference factors can be significantly reduced. This method not only improves the path - tracking accuracy of the unmanned boat but also enhances its autonomous navigation ability in complex marine environments.

[0046] Refer to Figure 3 , the ASAC - LOS guidance generates the desired heading ψ i P i+1 based on the current position of the unmanned boat and the reference path segment P d , and the calculation formula is as follows:

[0047] ψ d = ψ p - ψ LOS - (a + b·V w sin(Δψ pw ))β s(1)

[0048] In the formula, ψ p is the direction from P i to P i+1 in the current reference course segment, and ψ LOS is the desired heading angle; a and b are weight coefficients used to adjust the compensation intensity; V w is the wind speed; Δψ pw is the angle between the reference course segment direction ψ p and the wind direction β w ; β s is the measured sideslip angle.

[0049] For formula (1), the wind speed V w and the wind direction β w are collected in real time by an ultrasonic anemometer carried by the unmanned boat; the desired heading angle ψ LOS is calculated and generated based on the coordinates of the endpoints of the current reference course segment and the current position information of the unmanned boat, where the position of the unmanned boat is obtained by a high-precision global navigation satellite system receiver; the sideslip angle β s is determined by the vector angle between the actual movement direction of the unmanned boat and the heading, where the actual movement direction is obtained by dead reckoning using the longitude and latitude coordinates and timestamps continuously output by the high-precision global navigation satellite system receiver, and the heading is measured in real time by a three-axis magnetoresistive electronic compass.

[0050] In summary, this series of steps - including path segmentation, selection of virtual target points, calculation of the desired heading angle, and compensation for the sideslip angle - work together to improve the path tracking accuracy and stability of the unmanned boat when performing tasks.

[0051] The PID controller is designed to receive the desired heading calculated by the ASAC-LOS guidance law and the desired speed set by the user. Based on these inputs, the PID controller controls the thruster and other power mechanisms by analyzing the deviation between the actual heading and speed and the desired values, thereby adjusting the heading and speed of the unmanned boat to ensure stable navigation even in complex sea conditions.

[0052] Specifically:

[0053] Heading control: The heading controller is responsible for receiving the desired heading calculated by the ASAC-LOS guidance law as input. This step ensures that the unmanned boat can move forward along the preset reference path.

[0054] Speed control: The speed controller directly receives the desired speed set by the user as input. This allows the operator to flexibly adjust the speed of the unmanned boat according to the task requirements to adapt to different operating environments or task requirements.

[0055] Deviation Calculation and Control Instruction Generation: The core of the PID controller lies in its ability to accurately calculate the differences between the actual heading and speed and their respective expected values. Through the comprehensive processing of the proportional (P), integral (I), and derivative (D) components, the PID controller can output a series of control instructions. These instructions are aimed at minimizing the above-mentioned deviations and ensuring that the unmanned boat can efficiently respond to and correct any deviation from the reference path.

[0056] The PID controller calculates the thruster azimuth control instruction based on the deviation e between the expected heading ψ d and the current bow heading ψ of the unmanned boat ψ , as follows:

[0057]

[0058] where e ψ = ψ d - ψ, and K p,ψ , K i,ψ , and K d,ψ are the proportional, integral, and derivative coefficients respectively.

[0059] The PID controller calculates the thruster speed control instruction based on the deviation e between the expected speed V d and the current speed V of the unmanned boat V , as follows:

[0060]

[0061] where e V = V d - V, and K p,V , K i,V , and K d,V are the proportional, integral, and derivative coefficients respectively.

[0062] Execute Control Instructions: Finally, these control instructions are used to adjust parameters such as the thruster speed and azimuth of the unmanned boat. Such an adjustment mechanism enables the unmanned boat to continuously optimize its navigation state under changing ocean conditions until the actual heading and speed converge completely to the expected values.

[0063] S2. Proximal Navigation

[0064] As Figure 4 shown, when the unmanned boat approaches the mother ship and reaches a specific distance La (e.g., 500 meters) behind it, it will start to execute the proximal navigation task. The main objective of this stage is to ensure that the unmanned boat can accurately approach the mother ship and align with the recovery equipment on it.

[0065] A millimeter-wave radar installed on the mother ship is used to detect the relative distance and azimuth between the unmanned boat and the mother ship. Then, the mother ship transmits this information to the unmanned boat, and the unmanned boat establishes a local relative coordinate system based on the received information to assist navigation. For example, taking the installation position P0 of the millimeter-wave radar on the mother ship as the origin, a local relative coordinate system P0-X b Y b is established. Among them, the X b axis is positive to the right perpendicular to the center line of the mother ship, and the Y b axis is positive in the bow direction of the mother ship.

[0066] Set the current position P USV (x USV ,y USV ) of the unmanned boat as the starting point, and set the D point at a distance of L b (such as 200 meters) behind the mother ship as the target point, denoted as P D (x D ,y D ).

[0067] In the proximal navigation stage, the TAC-Theta* algorithm is used to plan a second reference path with steering angle constraints. This algorithm introduces steering angle constraints on the basis of the traditional Theta* algorithm to avoid overly sharp turning angles in the generated reference path, thereby improving the feasibility and stability of path planning.

[0068] According to the real-time position information of the unmanned boat and the mother ship provided by the millimeter-wave radar on the mother ship, the TAC-Theta* algorithm can plan an optimal path that conforms to the dynamic characteristics of the unmanned boat, from the current position P USV of the unmanned boat to the target point P D .

[0069] The TAC-Theta* algorithm ensures the smoothness and traceability of the path by selecting path nodes with a steering angle greater than θ max = 135°. To prevent significant steering angles from appearing in the generated path, a steering angle constraint function TAC(A, B, C, D) is introduced. This function is used to evaluate and adjust the steering angle between path nodes to ensure that the reference path fits the actual motion ability of the unmanned boat as much as possible. Specifically, in this function, B is the current node, A is the child node of B (i.e., the next node to be reached), C is the parent node of B (i.e., the previous node that has been passed), and D is the grandparent node of B (i.e., the node before the previous node that has been passed). In this way, TAC(A, B, C, D) can effectively limit the steering angle formed between consecutive nodes to ensure that they conform to the maximum steering ability of the unmanned boat, thereby improving the quality and feasibility of the entire path planning.

[0070] The function TAC(A, B, C, D) is defined as follows:

[0071]

[0072] In the formula, L BC represents the length of the route segment BC; L max is the maximum length preset by the user, usually set to 4 - 6 times the length of the unmanned boat. The TAC - Theta* algorithm can dynamically adjust the turning angle constraint according to the length of the route segment BC. Specifically, when the route segment BC is longer, the turning angle constraint can be appropriately relaxed; while when the route segment BC is shorter, the turning angle constraint will be more stringent. This adaptive adjustment strategy helps to eliminate the adverse effects brought by redundant path points and ensure the optimality of the path.

[0073] In the proximal navigation stage, the ASAC - LOS guidance algorithm combined with a PID controller is used to achieve precise path tracking of the unmanned boat. This process is similar to the description in the distal navigation stage. In particular, in the proximal navigation stage, the desired speed V d of the unmanned boat can be set independently by the user according to the specific situation, but it is generally recommended to set it slightly higher than the speed of the mother ship. Figure 5 Shows the schematic diagram of the combined use of the path planning algorithm, the ASAC - LOS guidance algorithm and the PID controller.

[0074] S3. Control the recovery

[0075] When the unmanned boat reaches a specific position P D behind the mother ship, it enters the recovery control stage. The core task of this stage is to ensure the precise docking of the unmanned boat with the recovery equipment on the mother ship. The unmanned boat needs to accurately drive along a straight line from the current position to the mid - point of the towing wire rope and complete the final recovery operation. Figure 6 Shows the schematic diagram of the unmanned boat approaching the mother ship and preparing for control recovery after completing the proximal navigation task.

[0076] In the recovery control stage, the unmanned boat keeps the local relative coordinate system established in the proximal navigation stage unchanged. The reference path is set to start from the current position of the unmanned boat and end at the recovery equipment on the mother ship (such as the mid - point of the towing wire rope). Through the real - time position information provided by the millimeter - wave radar on the mother ship, the reference navigation path of the unmanned boat is dynamically updated, and this path is defined as a straight line from the current position of the unmanned boat to the mid - point of the towing wire rope.

[0077] During this process, the ASAC-LOS guidance algorithm adjusts the heading of the unmanned boat using an adaptive sideslip angle compensation mechanism, enabling it to approach the mother ship steadily along a straight line. The PID heading controller adjusts the actual heading according to the desired heading calculated by ASAC-LOS to ensure that the direction of the unmanned boat is aligned with the mother ship. Meanwhile, the PID speed controller sets a speed slightly higher than that of the mother ship and adjusts the deviation to ensure that the unmanned boat approaches the mother ship safely at a constant speed.

[0078] In this way, by combining the ASAC-LOS guidance algorithm and the PID controller, the unmanned boat can accurately and stably sail towards and dock with the recovery equipment on the mother ship. Once the unmanned boat successfully docks with the recovery equipment, the recovery equipment will be activated to tow the unmanned boat into the interior of the mother ship.

[0079] As Figures 7 - 11 shown, the recovery equipment is installed in the recovery channel 103 at the tail of the mother ship 100 for recovering the unmanned boat 200. The equipment includes a towing steel wire rope 102 and a drive system that can drive the movement of the towing steel wire rope 102 to pull the unmanned boat hanging on it back into the recovery channel 103. In one embodiment, the drive system includes a pair of parallel chains 106 and their matching sprockets 107, as well as two motors 108 for driving the two chains to run synchronously. These two chains 106 are installed on both sides of the recovery channel 103 in parallel and are fixed within a support structure, namely the cage 105, to provide the necessary support. Both ends 104 of the towing steel wire rope 102 are connected to the two chains 106 by welding or special fastening devices and span across the interior of the recovery channel 103.

[0080] When the motors 108 are started, they drive the chains 106 to run synchronously, thereby causing the towing steel wire rope 102 to move along the recovery channel 103. The cage 105 is provided with side openings to facilitate the smooth movement of the towing steel wire rope. In addition, a part of the cage extends out of the stern to facilitate the hanging and connection of the approaching unmanned boat 200 by the towing steel wire rope.

[0081] The cage 105 is designed in a two-part structure, including a main body part and an extended part, which are joined by a hinge. The main body part is located within the recovery channel 103, and the extended part can extend out of the recovery channel 103 after being unfolded. The mother ship hull and the extended part are connected by a telescopic member 101 (such as a hydraulic cylinder). When the unmanned boat recovery and release task is not being performed, the mother ship hatch 109 is in a closed state, and the extended part is folded into the interior of the mother ship through the telescopic member 101. Only when the unmanned boat recovery and release task is being performed, the mother ship hatch 109 is opened, and the telescopic rod 101 lowers the extended part outside the recovery channel.

[0082] To adapt to unmanned boats of different sizes and draft depths, the telescopic member 101 can also flexibly adjust the angle of the extended part as needed, thereby changing the height of the towing wire rope 102 relative to the water surface, so that the towing wire rope 102 can accurately dock with the buckle 210 on the unmanned boat 200. The core part of the towing wire rope 102 uses high-strength and highly elastic Dyneema material, which has good corrosion resistance and is suitable for applications in the marine environment. The outer wrapping layer is made of composite fiber, and this material can withstand large impact forces without being easily broken, providing additional safety protection for the fixation of the unmanned boat.

[0083] The front end of the unmanned boat 200 is equipped with a buckle 210, which is made of high-strength metal material and has the ability to withstand large impact forces. The core component of the buckle 210 is the rotating part 211, which is designed as a one-way rotation mechanism to ensure that when the unmanned boat 200 is docked with the mother ship 100, the towing wire rope 102 can be firmly locked to prevent the unmanned boat 200 from accidentally detaching during the recovery process. The rotating part 211 remains locked when not under external force and will not move randomly.

[0084] As Figure 12 shown, the body 213 of the buckle 210 forms a three-sided closed structure, and the rotating part 211 is located on the open side. When subjected to an external force (such as the impact of the towing wire rope), the rotating part 211 can only rotate inward (i.e., towards the direction of the body 213), thereby opening the opening to allow the wire rope to enter; subsequently, without external force, the rotating part 211 will automatically rebound to re-close the opening to ensure that the wire rope is safely locked. For example, a torsion spring can be installed at the connection point between the rotating part 211 and the body 213, so that when an external force is applied to the rotating part 211, it will overcome the resistance provided by the torsion spring and rotate to open; once the external force disappears, the restoring force of the torsion spring will cause the rotating part 211 to rebound to the original position, thereby closing the opening. In addition to the torsion spring, a one-way bearing or a spring-loaded latch can also be used to control the rotation direction of the rotating part 211.

[0085] To adapt to the angle change requirements of the unmanned boat 200 under different sea conditions (the unmanned boat will perform heaving motions under the influence of waves and the wake of the mother ship), both ends of the body 211 extend obliquely to form structures 214. These outwardly extended structures 214 not only increase the vertical contact area between the buckle 210 and the towing wire rope 102, but also enhance the stability and reliability of the entire buckle 210.

[0086] The body 213 of the buckle 210 is fixed to the front end of the unmanned boat 200 by welding, ensuring its stability and reliability during navigation. In addition, the buckle 210 is cleverly placed inside the front cover 220 of the unmanned boat 200, avoiding any impact on the streamline of the hull. During the recovery control phase, the cover 220 of the unmanned boat 200 automatically opens to expose the built-in buckle 210 for docking operations.

[0087] When the unmanned boat 200 approaches the stern of the mother ship 100 and reaches a predetermined safe distance, the mother ship 100 uses its telescopic member 101 to lower the part of the retaining frame 105 outside the recovery channel to an appropriate position, ensuring that the towing steel wire rope 102 is at a suitable height for recovery. At this time, the unmanned boat 200 will automatically adjust its own heading and speed and move forward in the direction of the mother ship 100 at a pre-calculated relative speed.

[0088] As Figure 11 shown, even if there is a slight deviation between the center of the recovery channel 103 of the unmanned boat 200 and the mother ship 100 during docking, the buckle 210 designed at the front end of the unmanned boat can still effectively capture the towing steel wire rope 102, thus achieving a successful docking with the mother ship. This design greatly improves the fault tolerance rate of the docking process and ensures a high docking success rate even in complex sea conditions.

[0089] Once the docking is completed, the power system of the unmanned boat 200 immediately stops operating, including all propulsion and heading adjustment functions will be turned off. Subsequently, the mother ship 100 pulls the chain through the motor of its recovery equipment, drags the towing steel wire rope 102 fixed to the chain, gradually guides the unmanned boat 200 into the recovery channel, and finally pulls it completely into the mother ship to complete the entire recovery process.

[0090] Next, the staff will perform a series of subsequent operations, such as disconnecting the connection between the unmanned boat and the towing steel wire rope, firmly fixing the unmanned boat on the mother ship, and inspecting and maintaining the various equipment of the unmanned boat to ensure that it is ready for the next mission. After the entire recovery process is completed, all navigation and control systems of the unmanned boat will switch to the standby mode to respond to the needs of the next mission at any time.

[0091] In summary, the present invention uses Theta and TAC-Theta algorithms for path planning to ensure that the unmanned boat can reach the mother ship along the shortest and safest path and achieve precise docking, thus greatly improving the recovery efficiency. Combining the application of a precise global positioning system and a local positioning system, the present invention ensures the stable navigation ability of the unmanned boat in complex sea conditions.

[0092] In addition, by adopting a control strategy that combines the ASAC-LOS guidance algorithm with a PID controller, the intelligent management of the unmanned boat recovery process is achieved. This not only reduces the complexity of manual operations and the possibility of errors but also enhances the reliability and safety of the entire recovery operation.

[0093] The recovery device of the present invention demonstrates significant advantages: on the one hand, the requirements for the control accuracy of the heading and position of the unmanned boat are significantly reduced; on the other hand, the device has a stronger ability to adapt to high sea conditions and a higher operation fault tolerance rate, greatly improving the safety of the recovery process. Even when the unmanned boat is in different attitudes, it can successfully complete the docking task of the towing steel wire rope and the buckle, further demonstrating its high efficiency and reliability.

Claims

1. A method for recovering an unmanned boat, characterized in that, Including: Remote navigation task: Plan a first reference path from the current position of the unmanned boat to the current position of the mother ship under the global navigation satellite system. Use the adaptive sideslip angle compensation line-of-sight method combined with a PID controller to control the unmanned boat to track the first reference path, so that the unmanned boat approaches the mother ship; Proximal navigation task: When the unmanned boat approaches the mother ship and is less than a specific distance La from the mother ship, start the proximal navigation task. In this task, a local relative coordinate system is constructed based on the real-time relative distance and azimuth between the unmanned boat and the mother ship to assist navigation. Plan a second reference path with a steering angle constraint in this local relative coordinate system. Continue to use the adaptive sideslip angle compensation line-of-sight method combined with a PID controller to control the unmanned boat to move along the second reference path and align with the towing wire rope on the mother ship; Recovery control task: When the unmanned boat gets closer to the mother ship and reaches a specific distance Lb behind it, enter the recovery control task. In this task, continue to use the adaptive sideslip angle compensation line-of-sight method combined with a PID controller in the local relative coordinate system to control the unmanned boat to drive along a straight path towards the mother ship and connect to the towing wire rope on the mother ship, thus completing the recovery.

2. The unmanned boat recovery method according to claim 1, wherein In the remote navigation task, proximal navigation task and recovery control task, the method of using the adaptive sideslip angle compensation line-of-sight method combined with a PID controller to control the unmanned boat includes: Divide the first reference path, the second reference path, and the straight-line path into n - 1 reference flight segments connected by n reference path points P1(x1, y1), P2(x2, y2), ……, P n (x n , y n ), where each of the reference flight segments is composed of a starting point P i (x i , y i ) and an ending point P i+1 (x i+1 , y i+1 ), and i ≤ n - 1; With the current position P of the unmanned boat USV and radius R LOS Construct a guidance circle; Using the intersection point of the guidance circle and the reference flight path P i P i+1 as the virtual target point; Calculate the desired heading angle ψ that the unmanned boat should adopt according to the position of the virtual target point LOS ; Calculate the desired heading ψ according to Equation (1). d : ψ d = ψ p - ψ LOS -(a + b·V w sin(Δψ pw ))β s (1) where ψ p is the direction from P i to P i+1 in the current reference flight path segment, and ψ LOS is the desired course angle; a and b are weight coefficients used to adjust the compensation intensity; V w is the wind speed; Δψ pw is the angle between the reference flight path segment direction ψ p and the wind direction β w ; β s is the measured sideslip angle. The PID controller is configured to receive the calculated desired heading ψ d and the user-set desired speed, analyze the deviations between the actual heading and speed and the desired heading ψ d and the desired speed, and control and adjust the heading and speed of the unmanned boat to reduce the deviations, ensuring that the unmanned boat sails along the first reference path, the second reference path, and the straight-line path.

3. The unmanned boat recovery method according to claim 1, wherein Use the Theta* algorithm to plan the first reference path.

4. The unmanned boat recovery method according to claim 1, characterized in that Use the TAC-Theta* algorithm to plan the second reference path, and the steering angle in the second reference path is greater than 135 degrees.

5. An unmanned boat, characterized in that, This unmanned boat can be recovered to the mother ship by using the unmanned boat recovery method described in any one of claims 1 to 4.

6. The unmanned boat according to claim 5, characterized in that A buckle for hanging the towing wire rope on the mother ship is provided at the front end of the unmanned boat.

7. The unmanned boat according to claim 6, characterized in that, The buckle includes a body and a rotating part. The body surrounds a three-sided closed structure. The rotating part is located on the opening side of the body. When the rotating part is hit by the towing wire rope, it rotates towards the direction of the body, thus opening the opening to allow the towing wire rope to enter; subsequently, the rotating part will automatically rebound to re-close the opening to ensure that the towing wire rope is locked.

8. A mother ship, characterized in that, In the proximal navigation task, the mother ship can provide the unmanned boat described in claims 5 to 7 with the information required to establish the local relative coordinate system, including the real-time relative distance and azimuth information between the mother ship and the unmanned boat.

9. The mother ship according to claim 8, characterized in that, A recovery channel and a drive system are provided at the stern of the mother ship. The drive system can drive the towing wire rope to move and pull the unmanned boat hanging on it back into the recovery channel.

10. The mother ship according to claim 9, characterized in that, The drive system includes: Two chains and their supporting sprockets. The two chains are installed in parallel on both sides of the recovery channel and are respectively connected to the two ends of the towing wire rope spanning the recovery channel; A cage configured to support the two chains and the matching sprockets, the cage being provided with side openings to enable the smooth movement of the towing wire rope. The cage includes a main body portion and an extension portion. The main body portion is located within the recovery passage, and when the extension portion is unfolded, it can extend outside the recovery passage. The main body portion and the extension portion are connected by a hinge; A telescopic member connecting the hull of the mother ship and the extension portion of the cage, for retracting the extension portion into the recovery passage or unfolding it to extend outside the recovery passage, thereby adjusting the height of the towing wire rope relative to the water surface; and A motor configured to drive the synchronous movement of the two chains and pull the unmanned boat into the recovery passage through the towing wire rope.

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