Clustered AUV drag-net obstacle clearing system and control method

Abstract

The application relates to a cluster type AUV drag net obstacle clearing system and a control method. The system comprises an AUV cluster, an obstacle clearing net, a laying device and a control device, the AUV cluster is composed of AUVs with underwater navigation, positioning and communication capabilities; the obstacle clearing net is a regular polygon, and is connected with each AUV through an angular point at an opening; the laying device is used for storage before each AUV enters water; the control device comprises a computer and control software, and is used for task planning before launching of the AUV cluster, parameter binding and remote control when the AUV cluster is on the water surface. The control method adopts a leader-follower method. The application solves the cooperative control problem of multiple AUVs participating in the drag net in three-dimensional space under the condition of rope net constraint, and compared with a traditional obstacle clearing scheme using a special ship mounted with large special equipment, the application has the advantages of simple operation, high efficiency and low cost.

Description

Technical Field

[0001] This invention belongs to the field of autonomous underwater vehicles (AUVs), specifically relating to a cluster-type AUV obstacle clearing system and control method. Background Technology

[0002] Trawling is a basic operational method for single or multiple surface vessels to conduct activities such as clearing surface obstacles, fishing, and underwater salvage. Because vessels typically only trawle on or near the surface, it is difficult to clear or salvage underwater targets suspended in deep water or near the seabed (such as war-related mines, aircraft wreckage, shipwrecks, and their cargo). AUVs, as underwater vehicles, can autonomously navigate underwater according to pre-set tasks or routes and have a certain carrying and towing capacity. A swarm of AUVs can perform underwater trawling at great depths. When swarming AUVs, maintaining a stable relative position and formation is crucial.

[0003] Currently, methods for maintaining and controlling AUV swarm formations generally involve maintaining or changing formations under conditions where individuals are unconstrained. This means that individual AUVs in the swarm can relatively freely form linear, triangular, or circular formations with other AUVs without being restricted by cables. However, trawling obviously requires consideration of the relative shape of the clearing net and its impact on the AUVs. Furthermore, current AUV swarm control methods generally only consider formation maintenance in a two-dimensional plane. For example, Chinese invention patent CN113342014A, "An Underwater Vehicle Formation, System, and Method for Beach Clearing," discloses a dual-AUV formation where two underwater vehicles are connected by a flexible cable of a certain length. However, this method of coordinating the movement of two AUVs cannot be extended to the formation control of a swarm of multiple AUVs in a three-dimensional trawling operation. In addition, existing AUV swarm control technologies generally rely on underwater acoustic communication, but current underwater acoustic communication technology is insufficient to guarantee the high-speed, low-latency, and high-reliability communication requirements for swarm control. Therefore, how to achieve formation maintenance control of AUV clusters in three-dimensional space is an important technical problem that needs to be solved. Summary of the Invention

[0004] In view of the problems existing in the above background technology, the present invention provides a clustered AUV net-pulling obstacle removal system and control method to solve the problem of coordinated control of multiple AUVs participating in net pulling in three-dimensional space under rope net constraints.

[0005] The technical solution of this invention is as follows:

[0006] A clustered AUV obstacle removal system includes an AUV cluster, an obstacle removal net, a deployment device, and control equipment.

[0007] The AUV cluster consists of AUVs equipped with underwater navigation, positioning, and communication capabilities;

[0008] The obstacle clearing net is a regular polygon, and it is connected to each AUV through the corner points of the openings;

[0009] The deployment device is used for storage of each AUV before it enters the water. It includes a housing, a launch guide rod fixed inside the housing, and a fixed bracket connected to the launch guide rod. The AUV is installed on the fixed bracket by an explosion bolt or an electromagnetic attraction device.

[0010] The control equipment includes computers and control software, used for pre-launch mission planning, parameter setting, and remote control of the AUV cluster when it is on the water.

[0011] Furthermore, the number of AUVs in the AUV cluster is maintained at more than three, each AUV has a unique identification number, and each AUV has three signal receivers installed at equal intervals on its back and a signal transmitter installed on its belly.

[0012] Furthermore, communication cables are installed at the opening edge of the obstacle clearing net to form a ring-shaped communication bus. Each AUV has a communication cable in the cable connecting it to the obstacle clearing net. The communication cable is used to hang on the ring-shaped communication bus. Each AUV is a node on the ring-shaped communication bus and can share its own status information and perceived information to the bus in a broadcast manner. Each AUV can obtain information shared by other AUVs from the communication bus.

[0013] A control method for a cluster-type AUV obstacle removal system includes the following steps:

[0014] Step 1: Before deployment, use the control equipment to input the initial position and preset route information of the AUV cluster into the control computer of each AUV;

[0015] Step 2: During deployment, detonate the explosive bolts at the connection between the AUV and the fixed support, or open the electromagnetic attraction device to separate each AUV from the fixed support. After the AUV cluster enters the water, adjust its course and depth to the set values.

[0016] Step 3: After the AUVs separate, they form a preset formation. The obstacle removal net is opened, and each AUV maintains a stable formation by adjusting its own speed and course. It pulls the opened obstacle removal net along the preset route to carry out underwater obstacle removal operations.

[0017] Step 4: After the clearing net is blocked by the underwater target, it becomes entangled on the target. The AUV pulling the net then explodes after circling the target, thus clearing the underwater obstacle.

[0018] Furthermore, the method for maintaining formation stability of each AUV in step three is as follows: one or more AUVs are designated as leaders, and they navigate according to the set mission and pre-planned route. The remaining AUVs act as followers, adjusting their own speed and direction with reference to the position and speed of the leaders.

[0019] Furthermore, the method for determining the leader and followers includes the following steps:

[0020] 1) Calculate the deviation of each AUV in the cluster, where the deviation represents the weighted sum of the relative distance and relative azimuth angle of the current AUV relative to other AUVs in the cluster;

[0021] 2) Each AUV will broadcast the calculated deviation and its own identification number to the other AUVs.

[0022] 3) The AUV that receives the deviation information sorts the deviation of each of the other AUVs in ascending order. For AUVs with a deviation less than or equal to the threshold s*, a vote information with a value of "1" is sent to them; otherwise, a vote information with a value of "0" is sent. s* is taken as the median of the deviation.

[0023] 4) Each AUV receives the ballot information from the other AUVs. The AUV that receives half or more "1" ballots is the leader; otherwise, it is a follower.

[0024] Furthermore, the calculation of the deviation of each AUV in step 1) includes the following sub-steps:

[0025] 1.1) Calculate the azimuth angle of the current AUV relative to the other AUVs in the cluster.

[0026]

[0027] Where θ ki This represents the relative azimuth angle of the current AUV with respect to the i-th AUV;

[0028] 1.2) Calculate the relative distance of the current AUV with respect to the other AUVs in the cluster.

[0029]

[0030] When the above formula When, take Δr k =0;

[0031] Where r ki This represents the actual distance of the current AUV relative to the i-th AUV. This represents the theoretical distance from the point where the current AUV is located to the i-th vertex in the regular polygon;

[0032] 1.3) Calculate the deviation of the current AUV in the cluster, as shown in the following formula.

[0033] s k =p1Δr k +p2Δθ k

[0034] Where p1 and p2 are the weighting coefficients for relative distance and relative azimuth, respectively.

[0035] Furthermore, the AUVs acting as followers adjust their speed and direction based on the position and speed of the leader. For the i-th AUV, assuming there are m leader AUVs in the cluster, the relative position of the i-th AUV to the j-th leader AUV is θ. ij v i0 Let be the current speed of the i-th AUV, then the expected speed in the next control cycle is:

[0036]

[0037] Where, k θ The proportional coefficient for speed adjustment.

[0038] Furthermore, the AUVs acting as followers adjust their speed and direction with reference to the position and speed of the leader. For the i-th AUV, let the combined heading angle of its current pitch and yaw angle be... Assuming there are m lead AUVs in the cluster, the expected composite heading angle of the i-th AUV in the next control cycle is:

[0039]

[0040] in, Let k be the theoretical relative position vector of the i-th AUV with respect to the j-th leader AUV. r This is the proportional coefficient for adjusting the synthetic heading angle.

[0041] Furthermore, in actual use, the calculated speed and composite heading angle are limited based on the upper and lower limits of the AUV's speed and composite heading angle.

[0042] The beneficial technical effects of this invention are as follows:

[0043] 1. This invention uses a lightweight, low-cost AUV cluster as the basic obstacle removal unit. Employing a trawling method and following a self-planned route, it removes underwater obstacles (such as fishing nets, fishing stakes, shipwrecks, and war-era mines) from specific areas. This solves the problems of high difficulty in accurately locating targets, challenging demolition, and high risk encountered in underwater obstacle removal, thus improving the safety and automation level of obstacle removal. Compared to traditional obstacle removal methods that use dedicated vessels equipped with large, specialized equipment, this invention is simple to operate, highly efficient, and low-cost.

[0044] 2. The AUV cluster of the trawling net of the present invention utilizes the structure of the obstacle clearing net to ensure reliable communication between AUVs through wired communication and enables AVUs to share information with each other through bus-type communication.

[0045] 3. The AUV cluster control method described in this invention can also be applied to maintaining the formation of AUV clusters without network constraints. This invention can also be extended to scenarios such as underwater salvage and covert underwater transportation of military supplies. Attached Figure Description

[0046] Figure 1 Diagram showing the components of a cluster-type AUV obstacle removal system;

[0047] Figure 2 This is a schematic diagram of the AUV cluster assembly relationship;

[0048] Figure 3 A schematic diagram illustrating the deployment and startup process of an AUV cluster.

[0049] Figure 4 This is a schematic diagram of an AUV cluster trawling system.

[0050] Figure 5 This is a schematic diagram illustrating the principle of AUV relative distance and orientation measurement.

[0051] Figure 6 This is a schematic diagram of AUV distance deviation;

[0052] Figure 7 This is a state transition diagram for a single AUV.

[0053] Reference numerals in the attached diagram: 1-box; 2-launching guide rod; 3-fixed bracket; 4-explosive bolt; 5-signal receiver; 6-signal transmitter; 7-depth stabilizer. Detailed Implementation

[0054] The technical solution of the present invention will be further described clearly and completely below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the present invention, and not all of the embodiments. Based on the described embodiments, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0055] This invention provides a cluster-type AUV obstacle clearing system, such as... Figure 1 As shown, it includes an AUV cluster, a clearing net, a deployment device, and control equipment; the AUV cluster consists of AUVs equipped with underwater navigation, positioning, and communication capabilities; the clearing net is a regular polygon, connected to each AUV through the corner points of its openings; as shown... Figure 2 As shown, the deployment device is used for storage of each AUV before it enters the water. It includes a housing 1, a launch guide rod 2 fixed inside the housing 1, and a fixed bracket 3 connected to the launch guide rod 2. The AUVs are installed on the fixed bracket 3 by explosive bolts 4 or electromagnetic attraction devices. The control equipment includes a computer and control software, which are used for mission planning, parameter setting and remote control of the AUV cluster before launch.

[0056] The present invention also provides a control method for a cluster-type AUV obstacle clearing system, comprising the following steps:

[0057] Step 1: Before deployment, use the control equipment to input the initial position and preset route information of the AUV cluster into the control computer of each AUV;

[0058] Step 2: During deployment, detonate the explosive bolts at the connection between the AUV and the fixed support, or open the electromagnetic attraction device to separate each AUV from the fixed support. After the AUV cluster enters the water, adjust its course and depth to the set values.

[0059] Step 3: After the AUVs separate, they form a preset formation. The obstacle removal net is opened, and each AUV maintains a stable formation by adjusting its own speed and course. It pulls the opened obstacle removal net along the preset route to carry out underwater obstacle removal operations.

[0060] Step 4: After the clearing net is blocked by the underwater target, it becomes entangled on the target. The AUV pulling the net then explodes after circling the target, thus clearing the underwater obstacle.

[0061] Example:

[0062] See Figure 2Before deployment, the AUVs within the cluster are connected by fixed supports to form a bundled AUV assembly, which is then mounted on the launch guide rod within the deployment device. The launch guide rod provides support and guidance for the AUVs. Each AUV is connected to its fixed support using either expansion bolts or electromagnetic engagement devices to ensure a secure connection between the AUVs in the cluster before water entry and during deployment. The obstacle clearing net must be folded, packaged, and installed at the rear of the bundled AUV assembly before deployment.

[0063] Before deployment, the initial position and preset route information (including route control points, heading, and navigation depth) of the AUV cluster are loaded into the control computer of each AUV using control equipment. See also Figure 3 After the AUV swarm enters the water, it adjusts its course and depth to the set values. The AUVs are then separated from their fixed supports by detonating explosive bolts at the connection points or by activating the electromagnetic engagement device. Once separated, the AUVs form a preset formation, and the obstacle-clearing net is deployed. The AUV swarm controls its formation according to the method described in this invention, pulling the deployed net along a preset route to clear underwater obstacles. When the net is blocked by an underwater target, it becomes entangled on the target. The AUVs pulling the net then detonate after circling the target, thus clearing the underwater obstacle.

[0064] like Figure 4 Taking a clearing net with four corner points as an example, by adding a depth stabilizer 7 and buoyancy materials to the clearing net, its own weight is made equivalent to its buoyancy, and the depth of the net can be adjusted to minimize the vertical interference force of the clearing net on the AUV. The net rope is made of high-strength aramid fiber, which reduces the weight of the net and decreases its resistance.

[0065] The AUV's tail thruster has a hollow central shaft, internally housing a towing cable. The towing cable contains high-strength aramid fibers and communication cables. The high-strength aramid fibers connect the AUV to the clearing net, while the communication cables connect to the opening in the clearing net and are attached to a ring-shaped communication bus. Each AUV possesses underwater navigation, positioning, and communication capabilities, and the thrust generated by its thruster is sufficient for its own navigation and the power requirements of the towing net. Each AUV in the swarm has a unique identification number. Figure 5 As shown, each AUV is equipped with one signal transmitter to emit sound, light, or electromagnetic signals of specific frequencies and waveforms. Each AUV is distinguished by emitting signals of different frequencies and waveforms. Simultaneously, each AUV is equipped with three equally spaced signal receivers to receive sound, light, and electromagnetic signals of specific frequencies and waveforms emitted by other AUVs. The three signal receivers of each AUV determine its relative distance and orientation to other AUVs by the time difference of receiving the same signal.

[0066] refer to Figure 5 :

[0067] The azimuth angle of the i-th AUV relative to the j-th AUV is

[0068]

[0069] The distance between the i-th AUV and the j-th AUV is

[0070]

[0071] Where d is the distance between the signal receivers, τ ij (1≤i、j≤3) represents the time difference between the i-th and j-th signal receivers receiving the same signal, and c represents the propagation speed of sound, light, or electromagnetic waves.

[0072] like Figure 6 As shown, a single AUV sorts the relative distances of other detected AUVs. The current AUV sorts the relative distances of the remaining AUVs (number 1 to n) in the cluster, and then groups them into pairs. For a cluster containing n+1 AUVs, the set of relative distances of the remaining AUVs obtained by the k-th AUV is {r}. k1 r k2 , ..., r kn The first distance group is {r}. k1 r kn The second distance group is {r}. k2 r k(n-1)}, and so on. k1 r k2 …r kn The theoretical distances r from the current point to points 1 through n in a regular n+1 polygon are respectively... k1 *、r k2 *…r kn * Corresponding.

[0073] The current AUV's relative distance to the other AUVs in the cluster is

[0074]

[0075] When the above formula When, take Δr k =0.

[0076] The current AUV is equivalent to the azimuth angle of the other AUVs in the cluster.

[0077]

[0078] Define the weighted sum of the relative distance and relative azimuth angle of the current AUV relative to other AUVs in the cluster as the deviation of that AUV in the cluster.

[0079] s k =p1Δr k +p2Δθ k (5)

[0080] Where p1 and p2 are the weighting coefficients for relative distance and relative azimuth, respectively.

[0081] Each AUV broadcasts its calculated deviation and its own identification number to the other AUVs via the communication bus. The AUVs receiving the deviation information sort the deviations of the remaining AUVs in ascending order. For AUVs with deviations less than or equal to a threshold s* (where s* is the median deviation), they send a vote with a value of "1"; otherwise, they send a vote with a value of "0". Each AUV receives the votes from the other AUVs via the bus. The AUV that receives half or more "1" votes becomes the leader; otherwise, it becomes a follower. A "leader-follower" formation control method based on an election approach is adopted. Within a control cycle, the process of a single AUV participating in the election and its state transitions within the cluster is as follows: Figure 7 As shown.

[0082] AUVs with different roles maintain formation stability by adjusting their speed and heading. The AUV designated as the leader continues sailing according to its assigned mission and pre-planned route. AUVs designated as followers adjust their speed and heading with reference to the leader's position and speed. For the i-th AUV, assuming there are m leader AUVs in the group, the relative bearing of the i-th AUV to the j-th leader AUV is θ. ij v i0 Given the current speed of the i-th AUV, the expected speed in the next control cycle is:

[0083]

[0084] Where, k θ The proportional coefficient for speed adjustment.

[0085] For the i-th AUV, let the combined heading angle of its current pitch and yaw angle be... Assuming there are m lead AUVs in the cluster, the expected composite heading angle of the i-th AUV in the next control cycle is:

[0086]

[0087] in, Let k be the theoretical relative position vector of the i-th AUV with respect to the j-th leader AUV. r This is the proportional coefficient for adjusting the synthetic heading angle.

[0088] In actual use, the calculated speed and composite heading angle can be limited based on the upper and lower limits of the AUV's speed and composite heading angle.

Claims

1. A cluster-type AUV obstacle clearing system, characterized in that: This includes AUV clusters, obstacle removal nets, deployment devices, and control equipment; The AUV cluster consists of AUVs equipped with underwater navigation, positioning, and communication capabilities; The obstacle clearing net is a regular polygon, and it is connected to each AUV through the corner points of the openings; The deployment device is used for storage of each AUV before it enters the water. It includes a box (1), a launch guide rod (2) fixed inside the box (1), and a fixed bracket (3) connected to the launch guide rod (2). The AUV is installed on the fixed bracket (3) by an explosion bolt (4) or an electromagnetic attraction device. The control equipment includes computers and control software, used for pre-launch mission planning, parameter setting, and remote control of the AUV cluster when it is on the water.

2. The cluster-type AUV obstacle removal system according to claim 1, characterized in that: The number of AUVs in the AUV cluster is maintained at more than 3. Each AUV has a unique identification number. Each AUV has three signal receivers (5) installed at equal distances on its back and a signal transmitter (6) installed on its abdomen.

3. The cluster-type AUV obstacle removal system according to claim 2, characterized in that: Communication cables are installed at the opening edge of the obstacle clearing net to form a ring-shaped communication bus. Each AUV has a communication cable in the cable connecting it to the obstacle clearing net. The AUV is connected to the ring-shaped communication bus using the communication cable. Each AUV is a node on the ring-shaped communication bus and can share its own status information and sensed information to the bus in a broadcast manner. Each AUV can obtain information shared by other AUVs from the communication bus.

4. A control method for a cluster-type AUV obstacle clearing system according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Before deployment, use the control equipment to input the initial position and preset route information of the AUV cluster into the control computer of each AUV; Step 2: During deployment, detonate the explosive bolts at the connection between the AUV and the fixed support, or open the electromagnetic attraction device to separate each AUV from the fixed support. After the AUV cluster enters the water, adjust its course and depth to the set values. Step 3: After the AUVs separate, they form a preset formation. The obstacle removal net is opened, and each AUV maintains a stable formation by adjusting its own speed and course. It pulls the opened obstacle removal net along the preset route to carry out underwater obstacle removal operations. Step 4: After the clearing net is blocked by the underwater target, it becomes entangled on the target. The AUV pulling the net then explodes after circling the target, thus clearing the underwater obstacle.

5. The control method for the cluster-type AUV obstacle removal system according to claim 4, characterized in that: The method for maintaining formation stability of each AUV in step three is as follows: one or more AUVs are designated as leaders, and they sail according to the set mission and pre-planned route. The remaining AUVs act as followers, adjusting their own speed and direction with reference to the position and speed of the leaders.

6. The control method for the cluster-type AUV obstacle removal system according to claim 5, characterized in that: The method for determining the team leader and followers includes the following steps: 1) Calculate the deviation of each AUV in the cluster, where the deviation represents the weighted sum of the relative distance and relative azimuth angle of the current AUV relative to other AUVs in the cluster; 2) Each AUV will broadcast the calculated deviation and its own identification number to the other AUVs. 3) The AUV that receives the deviation information sorts the deviation of each of the other AUVs in ascending order. For AUVs with a deviation less than or equal to the threshold s*, a vote information with a value of "1" is sent to them; otherwise, a vote information with a value of "0" is sent, and s* is taken as the median of the deviation. 4) Each AUV receives the ballot information from the other AUVs. The AUV that receives half or more "1" ballots is the leader; otherwise, it is a follower.

7. The control method for the cluster-type AUV obstacle removal system according to claim 6, characterized in that: Step 1) involves calculating the deviation of each AUV, which includes the following sub-steps: 1.1) Calculate the azimuth angle of the current AUV relative to the other AUVs in the cluster. in This represents the relative azimuth angle of the current AUV with respect to the i-th AUV; 1.2) Calculate the relative distance of the current AUV with respect to the other AUVs in the cluster. When the above formula At that time, take ; in This represents the actual distance of the current AUV relative to the i-th AUV. This represents the theoretical distance from the point where the current AUV is located to the i-th vertex in the regular polygon; 1.3) Calculate the deviation of the current AUV in the cluster, as shown in the following formula. Where p1 and p2 are the weighting coefficients for relative distance and relative azimuth, respectively.

8. The method for underwater obstacle removal using the cluster-type AUV net-like obstacle removal system according to claim 7, characterized in that: The AUVs designated as followers adjust their speed and direction based on the position and speed of the leader. For the i-th AUV, assuming there are m leader AUVs in the cluster, the relative position of the i-th AUV with respect to the j-th leader AUV is... , Let be the current speed of the i-th AUV, then the expected speed in the next control cycle is: in, The proportional coefficient for speed adjustment.

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