Surface buoy system and tracking method to assist underwater robot communication and localization

Abstract

This invention relates to a surface buoy system and tracking method for assisting underwater robot communication and positioning, belonging to the field of underwater robot technology. To address the problem that the positioning accuracy of current underwater robots is affected by the static characteristics of existing buoys, leading to decreased accuracy as the distance between the buoy and the underwater robot increases, this invention utilizes a designed surface buoy system. On one hand, it acts as a communication relay, transmitting data information between the shore-based control unit and the underwater robot, enabling two-way communication between the two. On the other hand, the buoy obtains the relative position of the underwater robot through sonar positioning and autonomously moves to correct positional deviations, ensuring that the buoy and the underwater robot are on the same vertical line. Because the buoy and the underwater robot are on the same vertical line, the latitude and longitude of the buoy are the same as the latitude and longitude of the underwater robot. Combined with the depth position of the underwater robot, the precise location of the underwater robot can be determined.

Description

Technical fields:

[0001] This invention belongs to the field of underwater robot technology, specifically relating to a surface buoy system that assists underwater robots in communication and positioning, and a tracking method for underwater robots. Background technology:

[0002] With the development of the marine industry, underwater robots have a very broad prospect. However, the communication and positioning problems of underwater robots have been troubling researchers in this field. It is precisely the existence of these two major problems that limits the wider development and application of underwater robots.

[0003] To address the two issues mentioned above, many researchers have proposed and validated solutions. Regarding communication between underwater robots and shore-based ground stations, the mainstream solutions currently include cable communication, shallow-water wireless communication, and towed buoy relay communication. While all these solutions can meet the communication needs of underwater robots and ground stations, they also have significant drawbacks. Cable communication limits the underwater robot's range of movement due to the cable length, and the robot is easily entangled in the cable. Shallow-water wireless communication restricts the underwater robot to operating only in shallow waters and prevents it from operating in deep waters. Towed buoy relay communication combines the advantages of cable and wireless communication. The buoy communicates with the underwater robot via cable, and then the buoy acts as a relay station to communicate with the ground station via radio. However, because the buoy is passively moving, the cable is easily damaged during towing. Therefore, this communication solution remains in the experimental stage and has not been applied in industrial production.

[0004] To address the positioning problem of underwater robots, since navigation and positioning systems such as GPS or BeiDou have no signal underwater, the mainstream positioning methods for underwater robots currently include static buoy positioning, inertial navigation IMU positioning, and visual positioning. Static buoy positioning utilizes sonar and can provide long-term positioning of the underwater robot. However, because the buoy is static during sonar detection, the positioning accuracy decreases as the distance between the buoy and the underwater robot increases. Once the underwater robot is outside the sonar's detection range, it cannot be located. Inertial navigation IMUs experience increasing errors over time, and factors such as ocean currents severely interfere with their positioning. Visual positioning works well in clear water, but in practical applications, the color of seawater causes the acquired images to become hazy, severely limiting the line-of-sight range, making positioning impossible. Summary of the Invention:

[0005] This invention addresses the problem that the positioning accuracy of underwater robots is affected by the static characteristics of existing buoys, resulting in decreased accuracy as the distance to the underwater robot increases, as well as the problem that positioning of underwater robots using other methods is easily affected by factors such as ocean currents or limited by line-of-sight range.

[0006] A surface buoy system for assisting underwater robots in communication and positioning, the buoy system comprising: a buoy, a buoyancy block, a thruster, a radio frequency antenna, a positioning system, a communication cable, a telescopic rod, and a sonar;

[0007] The buoyancy block, thruster, radio frequency antenna, positioning system, and communication cable are all mounted on the buoy. The buoyancy block provides buoyancy to the buoy; the thruster adopts a dual-thruster structure to provide power to the buoy.

[0008] The positioning system is used to locate the buoy;

[0009] The sonar is mounted on the buoy via a telescopic rod. Three sonars are set up, and the distances between the three sonars and the center O of the buoy on the water surface are denoted as OA, OB, and OC. It is required that OA = OB = OC = R and the angle between any two of OA, OB, and OC is 120 degrees. The three sonars are used to obtain the straight-line distance between each sonar and the underwater robot.

[0010] The communication cable is used to connect the buoy and the underwater robot, enabling communication between the buoy and the underwater robot. The buoy is equipped with an onboard computer, which acquires the underwater robot's attitude data, sensor data, and image data via a network and forwards them to the shore-based control terminal.

[0011] The radio frequency antenna is used to enable wireless communication between the buoy system and the shore-based control terminal, forwarding the underwater robot's attitude and image data to the shore-based control terminal, and simultaneously receiving control commands from the shore-based control terminal and forwarding them to the underwater robot.

[0012] Furthermore, the onboard computer acquires the underwater robot's attitude data, sensor data, and image data via Ethernet and forwards them to the shore-based control terminal; attitude information and control commands are transmitted via TCP protocol, and image information is transmitted via UDP protocol.

[0013] Furthermore, when the radio frequency antenna performs wireless communication, the wireless communication is achieved through wireless network bridging.

[0014] Furthermore, the process by which the three sonars obtain their respective straight-line distances from the underwater robot is as follows:

[0015] The three sonars on the buoy are denoted as sonar A, B, and C; the sonar installed on the underwater robot is denoted as sonar D.

[0016] First, the buoy system activates its internal timer to begin measuring a set of data. When sonar A transmits the character 'a', the timer is recorded as t1. When sonar B transmits the character 'b', the timer is recorded as t2. When sonar C transmits the character 'c', the timer is recorded as t3.

[0017] When sonar D receives the character 'a', it immediately sends the character 'A'; upon receiving the character 'b', it immediately sends the character 'B'; upon receiving the character 'c', it immediately sends the character 'C'; when sonar A receives the character 'A', the timer is recorded as t4; when sonar B receives the character 'B', the timer is recorded as t5; when sonar C receives the character 'C', the timer is recorded as t6; a set of data measurement is completed; the timer is cleared.

[0018] Repeat the above process to collect the next set of data;

[0019] Calculate distance:

[0020]

[0021] Where c is the speed at which sound waves propagate in water.

[0022] A tracking method based on a surface buoy system that assists underwater robot communication and positioning includes the following steps:

[0023] S1. Based on the aforementioned surface buoy system for assisting underwater robot communication and positioning, a geometric model is established according to the spatial positional relationship between the buoy and the underwater robot. In the geometric model corresponding to the spatial positional relationship between the buoy and the underwater robot, point O is marked as the center position of the surface buoy, points A, B, and C are the positions of the three sonars on the buoy, point D' is the position of the underwater robot, and point D is the vertical projection of the underwater robot D' onto the water surface; ρ1, ρ2, and ρ3 are the straight-line distances between the three sonars A, B, and C on the buoy and the underwater robot D', R1, R2, and R3 are the vertical projections of ρ1, ρ2, and ρ3 onto the water surface, line segments OA = OB = OC = R and the angle between each pair of OA, OB, and OC is 120 degrees, R is the distance between the center of the buoy and the three sonars, and H is the depth of the underwater robot;

[0024] S2. Convert the three-dimensional geometric model into a two-dimensional geometric model representing R1, R2, and R3:

[0025]

[0026] S3. Geometric models based on the spatial positional relationship between buoys and underwater robots include:

[0027]

[0028] Then it is equivalent to

[0029]

[0030] S4. Tracking is performed based on the operation of the buoy system, and the specific process includes the following steps:

[0031] S41. Data acquisition, including: depth information H of the underwater robot and the distances ρ1, ρ2, and ρ3 between the three sonars on the buoy and the underwater robot;

[0032] ρ1, ρ2, and ρ3 were obtained through communication between the three sonars on the buoy and the sonar on the underwater robot;

[0033] S42. Data filtering: If the measured data meets the following conditions, the system judges the data to be correct; otherwise, the data is judged to be incorrect and the data set is discarded.

[0034]

[0035]

[0036]

[0037] S43. Based on the correct ρ1, ρ2, and ρ3 output after data filtering, and combined with the following conditions, the target direction is captured;

[0038]

[0039] A successful capture results in the buoy's nose pointing towards the underwater robot's vertical projection D on the water surface;

[0040] S44, Target Tracking:

[0041] Once the target is acquired, meaning its direction is locked, the underwater robot then enters the tracking phase.

[0042] First, determine whether the tracking is successful. The condition |ρ1-H|<δ is met. If it is met, it means that the initial tracking is successful. Here, δ is the tracking allowable error preset by the system.

[0043] If the initial tracking fails, the tracking continues. The tracking process involves the buoy moving forward while simultaneously performing data acquisition, data filtering, and target acquisition sequentially to ensure the buoy remains in tracking mode. The system then determines whether the conditions for successful tracking are met. If they are met, the tracking is successful; otherwise, the tracking continues until successful.

[0044] S45. Target Synchronization:

[0045] After successfully tracking the underwater robot, the buoy enters a real-time position synchronization state. The target synchronization process has two tasks: first, the buoy tracks the underwater robot's movement in real time, which is the same as the target tracking process and requires a smaller δ setting; second, the buoy sends latitude and longitude information to the ground station in real time, and combined with the depth information obtained by the depth sensor on the underwater robot, the underwater robot can be positioned in three-dimensional space.

[0046] Furthermore, in S41, the depth information H of the underwater robot is directly measured by the depth sensor of the underwater robot, and then transmitted from the underwater robot to the buoy system via cable communication.

[0047] Furthermore, the process by which S43 acquires the target direction is as follows:

[0048] Coarse adjustment orientation: If The buoy then spins 180°; if The buoy will then rotate 60° clockwise; if The buoy will then rotate 60° counterclockwise.

[0049] Fine-tuning orientation: After coarse-tuning orientation is completed, it is determined whether |ρ2-ρ3|<σ holds true, that is, whether the difference between ρ2 and ρ3 is small enough. If it holds true, the initial capture is successful; otherwise, the initial capture fails. If the capture fails, the size of ρ2 and ρ3 is compared. If ρ2>ρ3, the buoy is slowly rotated counterclockwise until |ρ2-ρ3|<σ holds true, that is, the capture is successful again.

[0050] Where σ is the capture allowable error preset by the system.

[0051] Furthermore, during the continued tracking in S44, the buoy moves forward, and the speed of the forward movement is determined by the difference between ρ1 and H. The larger the difference, the greater the speed of the forward movement, and vice versa.

[0052] Beneficial effects:

[0053] This invention utilizes a designed surface buoy system to achieve communication between a shore-based control unit and an underwater robot, as well as the positioning of the underwater robot. The buoy acts as a communication relay, relaying data between the shore-based control unit and the underwater robot, enabling two-way communication. Simultaneously, the buoy obtains the relative position of the underwater robot through sonar positioning and autonomously moves to correct positional deviations, ensuring that the buoy and the underwater robot are on the same vertical line. The buoy is equipped with a BeiDou satellite positioning module. Because the buoy and the underwater robot are on the same vertical line, the latitude and longitude of the buoy are the same as the latitude and longitude of the underwater robot. Furthermore, the depth sensor module on the underwater robot can obtain the underwater robot's depth position in real time, thus accurately locating the underwater robot. Therefore, this invention effectively solves the problem that the positioning accuracy of underwater robots is currently affected by the static characteristics of existing buoys, resulting in decreased accuracy as the distance to the underwater robot increases. At the same time, this invention also makes the positioning of underwater robots less susceptible to severe interference from factors such as ocean currents, and is not limited by factors such as line-of-sight range. Therefore, this invention has a wider range of applications and stronger applicability. Attached image description:

[0054] For ease of explanation, the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0055] Figure 1 This is a schematic diagram of the buoy system.

[0056] Figure 2 This is a functional block diagram of a buoy system acting as a communication relay.

[0057] Figure 3 This is a geometric model of the spatial positional relationship between the buoy and the underwater robot.

[0058] Figure 4 To simplify the geometric model of the spatial positional relationship between the buoy and the underwater robot.

[0059] Figure 5 This is a schematic diagram showing the position of point Q on one side of the bisector of ∠MON.

[0060] Figure 6 This is a schematic diagram showing the positional relationship of point D on one side of the angle bisectors of ∠AOB and ∠AOC.

[0061] Figure 7 This diagram illustrates the communication process between the three sonars on the buoy and the sonar on the underwater robot.

[0062] Figure 8 This is a flowchart illustrating the tracking process based on the operation of a buoy system. Detailed implementation method:

[0063] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0064] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0065] To address the problems existing in the background technology, this invention proposes a surface buoy system for assisting underwater robot communication and positioning, as well as a robot tracking method. The buoy system of this invention can achieve relay communication and real-time positioning of the underwater robot. Its most significant feature is the autonomous tracking of the underwater robot by the buoy (real-time tracking of the underwater robot's projection on the water surface). Because the buoy's real-time autonomous tracking results in the buoy always remaining directly above the underwater robot on the water surface, minimizing the relative distance, the greatest advantage of this invention is that it expands the underwater robot's range of motion (compared to static fixed buoy communication methods and fixed cable communication methods), and can continuously maintain a high degree of positioning accuracy for the underwater robot. The invention will be further explained below with reference to specific embodiments. Specific implementation method one:

[0067] This embodiment describes a surface buoy system for assisting underwater robots in communication and positioning. Its main purpose is to assist underwater robots in communication and positioning. The surface buoy system described in this embodiment is used to achieve relay communication for underwater robots, such as... Figure 1 As shown, the buoy system includes: buoy 1, buoyancy block 2, thruster 3, radio frequency antenna 4, Beidou positioning system 5, communication cable 6, telescopic pole 7, and sonar 8;

[0068] The buoyancy block 2, thruster 3, radio frequency antenna 4, Beidou positioning system 5, and communication cable 6 are all installed on the buoy 1. The buoyancy block 2 is used to provide buoyancy for the buoy, and the thruster 3 is used to provide power for the buoy. The present invention adopts a dual thruster structure.

[0069] The BeiDou-5 positioning system is used to locate buoys;

[0070] Sonar 8 is mounted on the buoy via telescopic rod 7. Three sonars are set up. The center distances of the three sonars to the surface buoy are denoted as OA, OB, and OC. It is required that OA = OB = OC = R and the angle between any two of OA, OB, and OC is 120 degrees. The three sonars are used to obtain the straight-line distance between themselves and the underwater robot.

[0071] Communication cable 6 is a zero-buoyancy cable used to connect the buoy and the underwater robot to enable communication between the buoy and the underwater robot. The buoy is equipped with an onboard computer, which acquires the underwater robot's attitude data, sensor data and image data via Ethernet and forwards them to the shore-based control terminal. Attitude information and control commands are transmitted via TCP protocol, and image information is transmitted via UDP protocol.

[0072] The radio frequency antenna 4 is used to realize wireless communication between the buoy system and the shore-based control terminal. The wireless communication is achieved through wireless network bridging. It forwards the attitude and image data of the underwater robot to the shore-based control terminal, and at the same time receives the control commands from the shore-based control terminal and forwards them to the underwater robot.

[0073] The communication process between underwater robots, buoy systems, and shore-based control terminals is as follows: Figure 2 As shown.

[0074] More specifically, Specific Implementation Method Two:

[0076] This embodiment is a tracking method based on a surface buoy system that assists underwater robot communication and positioning. It adopts fuzzy orientation and precise tracking to achieve autonomous horizontal tracking of the underwater robot by the buoy. The purpose of autonomous horizontal tracking is to ensure that the buoy and the underwater robot are on the same straight line perpendicular to the horizontal plane. The latitude and longitude information of the underwater robot is indirectly obtained by determining the latitude and longitude information of the buoy.

[0077] The tracking method of the surface buoy system based on assisting underwater robot communication and positioning described in this embodiment includes the following steps:

[0078] 1. Establish a geometric model based on the spatial relationship between the buoy and the underwater robot:

[0079] A geometric model is established to represent the spatial relationship between the buoy and the underwater robot, such as... Figure 3 As shown, Figure 3 In the diagram, point O is the center of the surface buoy, points A, B, and C are the positions of the three sonars on the buoy, point D' is the position of the underwater robot, and point D is the vertical projection of the underwater robot D' onto the water surface. ρ1, ρ2, and ρ3 are the straight-line distances between the three sonars A, B, and C on the buoy and the underwater robot D', respectively. R1, R2, and R3 are the vertical projections of ρ1, ρ2, and ρ3 onto the water surface, respectively. Line segments OA = OB = OC = R, and the angle between any two OA, OB, and OC is 120 degrees. R is the distance between the center of the buoy and the three sonars, and H is the depth of the underwater robot. The known measurable data include R (a fixed value), H (measured by the depth sensor on the underwater robot), and ρ1, ρ2, and ρ3 (measured by the three sonars on the buoy and the sonar on the underwater robot).

[0080] 2. Simplify the geometric model of the spatial relationship between the buoy and the underwater robot, such as... Figure 4 As shown;

[0081] Since the purpose of this system is to enable the buoy to track the underwater robot in the horizontal direction, i.e., the buoy has no active movement in the vertical direction, the three-dimensional geometric model is converted into a two-dimensional geometric model for ease of derivation:

[0082]

[0083] 3. Equivalent based on the geometric model of the spatial position relationship between the simplified buoy and the underwater robot

[0084]

[0085] Proof process:

[0086] Proof: If R1 = max{R1, R2, R3}, then point D is within the angular range of ∠BOC, and it is called

[0087] For the convenience of proof, set points M, N, and Q, as shown in Figure 5 , first prove the first theorem: If ∠MON = 120° and OM = ON, and the straight line OX is the angular bisector of ∠MON, and Q is an arbitrary point in the plane. If MQ < NQ, then point Q is on the side of the angular bisector OX with point M. Based on this theorem, prove that if R1 = max{R1, R2, R3}, then point D is within the angular range of ∠BOC, and it is called

[0088] First, prove the following theorem:

[0089] If ∠MON = 120° and OM = ON, and the straight line OX is the angular bisector of ∠MON, and Q is an arbitrary point in the plane. If MQ < NQ, then point Q is on the side of the angular bisector OX with point M, as shown in the rectangular coordinate system Figure 5 shown;

[0090] Let the coordinates of point M be The coordinates of point N be The coordinates of point Q be (b, c), where a > 0.

[0091] Then [[ID=4​​​​​​​​​​​​​​​​Applying the proven theorem above, we can obtain: If R1 = max{R1, R2, R3}, i.e., R2 < R1, R3 < R1; then point D is located on one side of point B on the angle bisector OC of ∠AOB, and point D is also located on one side of point C on the angle bisector OB of ∠AOC. For example... Figure 6 As shown;

[0097] In summary, point D lies within the angle subtended by ∠BOC, that is... Therefore, if R1 = max{R1, R2, R3}, then

[0098] Similarly, it can be proved that:

[0099] If R2 = max{R1, R2, R3}, then

[0100] If R3 = max{R1, R2, R3}, then

[0101] because

[0102]

[0103] so

[0104]

[0105] Equivalent to

[0106]

[0107] 4. Tracking based on the operation of the buoy system

[0108] The buoy system operation process includes: data acquisition, data filtering, target acquisition, target tracking, and target synchronization. The processing steps are as follows: Figure 8 As shown;

[0109] S41, Data Acquisition

[0110] The data to be collected includes: the depth information H of the underwater robot and the distances ρ1, ρ2, and ρ3 between the three sonars on the buoy and the underwater robot; ρ1, ρ2, and ρ3 are obtained by communication between the three sonars on the buoy and the sonar on the underwater robot, respectively.

[0111] The known data includes the horizontal distance R between the buoy's center and the three sonars on the buoy.

[0112] The depth information H of the underwater robot is directly measured by the depth sensor of the underwater robot, and then the data is read by the main control system on the underwater robot and transmitted to the buoy system through cable communication.

[0113] The process of obtaining ρ1, ρ2, and ρ3 through communication between the three sonars on the buoy and the sonar on the underwater robot is as follows:

[0114] like Figure 7 As shown, sonars A, B, and C are three sonars on the buoy, and sonar D is the sonar on the underwater robot.

[0115] First, the buoy system activates its internal timer to begin measuring a set of data. When sonar A transmits the character 'a', the timer is recorded as t1; when sonar B transmits the character 'b', the timer is recorded as t2; and when sonar C transmits the character 'c', the timer is recorded as t3.

[0116] When sonar D receives the character 'a', it immediately sends the character 'A'; upon receiving the character 'b', it immediately sends the character 'B'; and upon receiving the character 'c', it immediately sends the character 'C'. When sonar A receives the character 'A', the timer is recorded as t4; when sonar B receives the character 'B', the timer is recorded as t5; and when sonar C receives the character 'C', the timer is recorded as t6. A set of data measurements is completed; the timer is then reset.

[0117] Repeat the above process to collect the next set of data.

[0118] Calculate distance:

[0119]

[0120] Where c is the speed of sound in water (since the speed of sound is affected by temperature, the speed of sound is corrected in real time by temperature data obtained from the temperature sensor on the underwater robot to improve the accuracy of the measurement).

[0121] S42, Data Filtering

[0122] Because sonar measurements are subject to various complex interferences that can lead to errors in a small portion of the data, filtering out erroneous data is essential for accurate tracking by the buoy system. The key to filtering is determining the correctness of the data. The theoretical basis for this determination in this invention is the geometric theorem that the difference between any two sides of a triangle is always less than the third side.

[0123] like Figure 3 As shown, based on geometric knowledge, Since the difference between any two sides of a triangle must be less than the third side:

[0124] In △ABD′, |BD′-AD′|<AB, that is... Similarly,

[0125] Therefore, if the measured data meets the requirements

[0126]

[0127] If the system determines the data is correct, it saves the data; otherwise, it determines the data is incorrect and discards the data set.

[0128] S43, Target Acquisition (Fuzzy Orientation)

[0129] Based on the correct ρ1, ρ2, and ρ3 output from the data filtering stage, and combined with the theoretical theorems derived above,

[0130]

[0131] To achieve target acquisition, a successful acquisition is achieved when the buoy's nose (OA direction) faces the underwater robot's vertical projection D on the water surface. The acquisition process is as follows:

[0132] The buoy uses a dual-propeller structure, enabling it to perform translational motion in all directions and spin motion.

[0133] The capture process involves two steps: coarse orientation and fine orientation.

[0134] Coarse adjustment orientation: If The buoy then spins 180°; if The buoy will then rotate 60° clockwise; if The buoy will then rotate 60° counterclockwise.

[0135] Fine-tuning Orientation: After coarse orientation is completed, it is determined whether |ρ2-ρ3|<σ holds true, that is, whether the difference between ρ2 and ρ3 is small enough. If it holds true, the initial capture is successful; otherwise, the initial capture fails. If the capture fails, the magnitudes of ρ2 and ρ3 are compared. If ρ2>ρ3, the buoy is slowly rotated counterclockwise (reducing the difference between ρ2 and ρ3) until |ρ2-ρ3|<σ holds true, that is, the capture is successful again.

[0136] Wherein, σ is the system's preset capture allowable error. When the value of σ is set to be small, the difficulty of successful capture decreases, but the time required for capture increases; conversely, the larger the value of σ is set, the more difficult it is to succeed in capture, but once the capture state is entered, the time required from capture to locking is smaller.

[0137] S44, Target Tracking

[0138] Once the target is captured, meaning its direction is locked (the underwater robot's vertical projection on the water surface is directly in front of the buoy), the underwater robot then enters the tracking phase.

[0139] First, determine whether the tracking was successful. The condition |ρ1-H|<δ is met. If it is met, it means that the initial tracking was successful.

[0140] Wherein, δ is the tracking allowable error preset by the system. The smaller the value of δ, the more difficult it is to track successfully and the longer it takes to track. However, once the tracking is successful, the positioning accuracy of the underwater robot is higher. Conversely, if the value of δ is set to be larger, the easier it is to track successfully and the shorter it takes to track. However, once the tracking is successful, the positioning accuracy of the underwater robot is lower.

[0141] If initial tracking fails, tracking continues. The tracking process involves the buoy moving forward, with the speed determined by the difference between ρ1 and H; a larger difference results in a faster speed, and vice versa. Simultaneously, data acquisition, data filtering, and target acquisition are performed sequentially to ensure the buoy remains in tracking mode. After a certain time interval, a check is performed to determine if the tracking success conditions are met. If met, tracking is successful; otherwise, tracking continues until successful.

[0142] S45. Target Synchronization (Precise Tracking)

[0143] After successfully tracking the underwater robot, the buoy enters a real-time position synchronization state. The target synchronization process has two tasks: first, the buoy tracks the underwater robot's movement in real time, which is the same as the target tracking process, except that the δ value is set smaller to ensure the accuracy of synchronization; second, the buoy sends latitude and longitude information to the ground station in real time. This information indirectly represents the underwater robot's position information. Combined with the depth information obtained by the depth sensor on the underwater robot, the underwater robot can be positioned in three-dimensional space.

[0144] With the development of the marine industry and the advancement of related technologies such as underwater communication, the surface buoy system of this invention, which assists underwater robots in communication and positioning, has a broader application prospect. For example, combined with underwater optical communication, it can realize wireless communication between shore-based and underwater robots. The communication efficiency of underwater optical communication is higher than that of sonar. Experiments have verified that underwater blue-green light communication can achieve a communication rate of up to 20 Mbit / s at a distance of 100m, which is sufficient for the transmission of image and control signals. However, underwater optical communication technology is not yet mature and is still in the experimental stage. One drawback of underwater optical communication is that it requires directional transmission of information, that is, the two communicating devices must know each other's positions before establishing communication. The buoy system of this invention, with its autonomous tracking capability, can precisely overcome the shortcomings of directional transmission in underwater optical communication. Therefore, in the future, the combination of underwater optical communication and autonomous tracking buoys will be the mainstream solution for underwater communication and positioning.

[0145] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A surface buoy system for assisting underwater robots in communication and positioning, characterized in that, The buoy system includes: buoy, buoyancy block, thruster, radio frequency antenna, positioning system, communication cable, telescopic mast, and sonar; The buoyancy block, thruster, radio frequency antenna, positioning system, and communication cable are all mounted on the buoy. The buoyancy block provides buoyancy to the buoy; the thruster adopts a dual-thruster structure to provide power to the buoy. The positioning system is used to locate the buoy; The sonar is mounted on the buoy via a telescopic rod. Three sonars are set up, and the distances between the three sonars and the center O of the buoy on the water surface are denoted as OA, OB, and OC. It is required that OA=OB=OC=R and the angle between any two of OA, OB, and OC is 120 degrees. The three sonars are used to obtain the straight-line distance between each sonar and the underwater robot. The communication cable is used to connect the buoy and the underwater robot, enabling communication between the buoy and the underwater robot. The buoy is equipped with an onboard computer, which acquires the underwater robot's attitude data, sensor data, and image data via a network and forwards them to the shore-based control terminal. The radio frequency antenna is used to enable wireless communication between the buoy system and the shore-based control terminal, forwarding the underwater robot's attitude and image data to the shore-based control terminal, and simultaneously receiving control commands from the shore-based control terminal and forwarding them to the underwater robot.

2. The surface buoy system for assisting underwater robot communication and positioning according to claim 1, characterized in that, The onboard computer acquires the underwater robot's attitude data, sensor data, and image data via Ethernet and forwards them to the shore-based control terminal; attitude information and control commands are transmitted via TCP protocol, and image information is transmitted via UDP protocol.

3. A surface buoy system for assisting underwater robot communication and positioning according to claim 2, characterized in that, When a radio frequency antenna performs wireless communication, the wireless communication is achieved through wireless network bridging.

4. A surface buoy system for assisting underwater robot communication and positioning according to any one of claims 1 to 3, characterized in that, The process by which the three sonars determine their respective straight-line distances to the underwater robot is as follows: The three sonars on the buoy are denoted as sonar A, B, and C; the sonar installed on the underwater robot is denoted as sonar D. First, the buoy system starts its internal timer to begin measuring a set of data; when sonar A transmits the character 'a', the timer count is recorded. When sonar B transmits the character 'b', the timer records the countdown. When sonar C transmits the character 'c', the timer is recorded. ; When sonar D receives the character 'a', it immediately sends the character 'A'; upon receiving the character 'b', it immediately sends the character 'B'; upon receiving the character 'c', it immediately sends the character 'C'; when sonar A receives the character 'A', the timer is recorded. When sonar B receives the character 'B', the timer is recorded as 'B'. When sonar C receives the character 'C', the timer is recorded as 'C'. Complete the measurement of a set of data; clear the timer; Repeat the above process to collect the next set of data; Calculate distance: ； Where c is the speed at which sound waves propagate in water.

5. A tracking method for a surface buoy system based on assisting underwater robot communication and positioning, characterized in that, Includes the following steps: S1. A surface buoy system for assisting underwater robot communication and positioning as described in any one of claims 1 to 4, wherein a three-dimensional geometric model is established based on the spatial positional relationship between the buoy and the underwater robot, and in the geometric model corresponding to the spatial positional relationship between the buoy and the underwater robot, point O is marked as the center position of the surface buoy, points A, B, and C are the positions of the three sonars on the buoy, point D' is the position of the underwater robot, and point D is the vertical projection of the underwater robot D' on the water surface; , , These represent the straight-line distances between the three sonars A, B, and C on the buoy and the underwater robot D'. , , They are respectively , , The vertical projection on the water surface is given by line segment OA=OB=OC=R, and the angle between each pair of OA, OB, and OC is 120 degrees. R is the distance between the center of the buoy and the three sonars, and H is the depth of the underwater robot. S2. Convert the three-dimensional geometric model into a two-dimensional geometric model representation. , , : ； S3. Geometric models based on the spatial positional relationship between buoys and underwater robots include: ； Then it is equivalent to ； S4. Tracking is performed based on the operation of the buoy system, and the specific process includes the following steps: S41. Data acquisition, including: depth information H of the underwater robot and the distance between the three sonars on the buoy and the underwater robot. , , ; , , The data was obtained through communication between three sonars on the buoy and the sonar on the underwater robot. S42. Data filtering: If the measured data meets the following conditions, the system judges the data to be correct; otherwise, the data is judged to be incorrect and the data set is discarded. ； S43. Based on the correct output after data filtering And by combining the following conditions, the target direction can be captured; ； A successful capture results in the buoy's nose pointing towards the underwater robot's vertical projection D on the water surface; S44, Target Tracking: Once the target is acquired, meaning its direction is locked, the underwater robot then enters the tracking phase. First, determine whether the tracking was successful; the conditions for this determination are as follows. Whether it is valid or not, if it is valid, it means that the initial tracking was successful; among them, The tracking tolerance is preset for the system. If the initial tracking fails, the tracking continues. The tracking process involves the buoy moving forward while simultaneously performing data acquisition, data filtering, and target acquisition sequentially to ensure the buoy remains in tracking mode. The system then determines whether the conditions for successful tracking are met. If they are met, the tracking is successful; otherwise, the tracking continues until successful. S45. Target Synchronization: After successfully tracking the underwater robot, the buoy enters a real-time position synchronization state. The target synchronization phase has two tasks: first, the buoy tracks the underwater robot's movement in real time, a process similar to the target tracking phase, requiring... The first feature is a smaller buoy; the second is that the buoy sends latitude and longitude information to the ground station in real time, which, combined with the depth information obtained by the depth sensor on the robot, enables the underwater robot to be positioned in three-dimensional space.

6. The tracking method of a surface buoy system based on assisted underwater robot communication and positioning according to claim 5, characterized in that, In S41, the depth information H of the underwater robot is directly measured by the underwater robot's depth sensor, and then transmitted from the underwater robot to the buoy system via cable communication.

7. A tracking method for a surface buoy system based on assisting underwater robot communication and positioning, as described in claim 5 or 6, characterized in that, The process by which S43 acquires the target's direction is as follows: Coarse adjustment orientation: If The buoy will then spin 180°; if The buoy will then rotate 60° clockwise; if Then the buoy will rotate counterclockwise by 60°; Fine-tuning Orientation: Judgment after coarse-tuning orientation is completed. Whether it is true or false, i.e., judgment and If the difference is small enough, the initial capture is successful; otherwise, the initial capture fails. If capture fails, compare... and The size, if The buoy will then slowly rotate counterclockwise until... Successful recapture means that the capture was successful. in, The capture allowable error is preset for the system.

8. A tracking method for a surface buoy system based on assisted underwater robot communication and positioning according to claim 7, characterized in that, In S44, as tracking continues, the buoy moves forward, and the speed of this forward movement changes from... The difference between H and H determines the forward velocity; the larger the difference, the greater the forward velocity, and vice versa.

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