Mine hunting system

Abstract

A minehunting system (20) comprising a first and a second unmanned underwater vehicle (UAV) is disclosed. The first UAV (22) is trained to proceed on a predetermined course (32) to an object (34) in the water, generating a situational awareness picture (50) using a sonar system while proceeding and identifying the object (34). The second UAV (24) is trained to proceed on the predetermined course (32) to an object identified as the identified mine, with the second UAV and / or a base station being trained to monitor and, if necessary, adjust the current course (32) of the second UAV based on the situational awareness picture (50) of the first UAV. The second UAV (24) is further trained to disarm the mine.

Description

[0001] The invention relates to mine hunting, i.e., mine clearance, of sea mines using two unmanned underwater vehicles. The first unmanned underwater vehicle identifies the mine, and the second unmanned underwater vehicle renders it harmless. That is, the sea mine is typically detonated by the second unmanned underwater vehicle.

[0002] The first unmanned underwater vehicle (UAV) is equipped with numerous sensors to navigate to and identify a potential sea mine. The second UAV is designed for single use only, making its production as cost-effective as possible. Consequently, the second UAV is significantly less sophisticated. It is typically only capable of navigating to the identified sea mine and recognizing it. While identification, for example using a camera, is advantageous, it is not always feasible due to factors such as water turbidity. This capability is reserved for the first UAV, which is designed for multiple uses.

[0003] Underwater, however, there is no absolute navigation system like GPS above water, and absolute position determination via acoustic tracking from an external platform, such as a base station, is not always possible or can be inaccurate, especially at large distances. Therefore, underwater navigation is usually supplemented or alternatively achieved using a combination of magnetometer and accelerometer, and optionally a gyroscope. The orientation data is combined with the position from an external tracking system and used in the operational software to navigate the vehicle to its destination (automatically or manually). This means dead reckoning is performed from a known starting point, at least when absolute position determination is not possible or to optionally supplement absolute position determination.However, the sensors used for dead reckoning exhibit an error dependent on external factors. This error is, for example, time-dependent or temperature-dependent and therefore cannot be compensated for. Consequently, precise navigation to the mine is not possible. The quality of the tracking (dead reckoning and / or acoustic tracking) and the vehicle's orientation then corresponds to the positional accuracy. The sensors used for navigation are also referred to as a position sensor system.

[0004] The object of the present invention is therefore to create an improved concept for mine hunting with two unmanned underwater vehicles.

[0005] The problem is solved by the subject matter of the independent patent claims. Further advantageous embodiments are the subject matter of the dependent patent claims.

[0006] Exemplary embodiments show a minehunting system with a first and a second unmanned underwater vehicle. The first unmanned underwater vehicle travels, i.e., navigates, on a predetermined course toward an object in the water and generates a situational image using a sonar system while underway. For navigation, the known sensors for dead reckoning can be used. However, with the help of additional sensors, it is possible to correct the navigation error, at the latest when approaching the object, and, for example, to identify the object using a camera.

[0007] The first unmanned underwater vehicle is preferably remotely controlled, particularly via a wired connection, i.e., by means of a cable, for example, a fiber optic cable, to a base station, such as a surface vessel like a ship. In principle, it is also possible for the first unmanned underwater vehicle to be an autonomous underwater vehicle, but one that is connected to the base station via the cable. The cable then allows the transmission of the relatively large amounts of data required for object identification to the base station. This also makes it possible to perform acoustic tracking, for example, from the base station, either independently, additionally, or alternatively. The control of the first unmanned underwater vehicle can be carried out from the base station or autonomously within the first unmanned underwater vehicle itself. The base station can therefore also be part of the minehunting system.

[0008] Once the object is identified as a mine, the second unmanned underwater vehicle (UAV) proceeds on the same predetermined course toward the identified mine. The existing sensors for dead reckoning can be used for navigation. However, the additional sensors needed to correct navigational errors are lacking, which is necessary to keep the second UAV as cost-effective as possible, since it is typically destroyed during mine clearance. The second UAV's current course can be monitored and adjusted, if necessary, based on the situational awareness of the first UAV.

[0009] Preferably, the second unmanned underwater vehicle also generates a situational awareness picture while underway, using a sonar system, in particular a sonar system identical to that of the first unmanned underwater vehicle. That is, the sonar system detects reflection points in the vicinity of the second unmanned underwater vehicle and compares them with the situational awareness picture of the first unmanned underwater vehicle. Based on this comparison of the situational awareness picture of the first and the second unmanned underwater vehicle, the second unmanned underwater vehicle can monitor its course and adjust it if necessary. If the situational awareness pictures consist of point clouds of reflection points, as described below, the point cloud generated by the first unmanned underwater vehicle (situational awareness picture 1) is compared with the point cloud forming by the second unmanned underwater vehicle (situational awareness picture 1).Course control can be carried out by the second unmanned underwater vehicle or by the base station. Once the second unmanned underwater vehicle has reached its target, it can disarm the mine. This is done, for example, by detonating an explosive charge, preferably a shaped charge. To maintain its position, the second unmanned underwater vehicle can anchor itself to the mine, for example, using a spike. The spike can, for instance, be deployed from the underwater vehicle when it is in close proximity to the mine.

[0010] The second unmanned underwater vehicle is preferably remotely controlled, particularly via a wired connection, i.e., by means of a cable, for example, a fiber optic cable, to a base station, e.g., a surface vessel such as a ship. In principle, it is also possible for the second unmanned underwater vehicle to be autonomous. It is also possible for the navigation of the second unmanned underwater vehicle to be autonomous, but for the detonation command to be issued manually, i.e., by a human. The detonation command can be given via the cable or by means of underwater communication.

[0011] The idea is therefore to use a spatial representation of the environment, the situational awareness picture, to improve the navigation of the second unmanned underwater vehicle and correct course deviations. For example, the goal could be to minimize deviations in reflection points between the first and second situational awareness pictures, perhaps using a control system. This would enable the second underwater vehicle to precisely locate the target position specified by the first unmanned underwater vehicle, even without additional sensors.

[0012] When this disclosure refers to an "underwater craft," it always refers to an "unmanned underwater craft." Furthermore, the description does not always distinguish between the first and second unmanned underwater craft. Therefore, when only one "underwater craft" is mentioned, the corresponding characteristics can be applied to the first unmanned underwater craft as well as, additionally or alternatively, to the second unmanned underwater craft.

[0013] In some embodiments, the first unmanned underwater vehicle (UAV) is equipped to classify the mine. Based on this classification, the second UAV can then target a point of attack on the mine to neutralize it. This means that, for example, at the base station, a target position and, optionally, a target orientation are determined for the second UAV based on the type of sea mine, in order to neutralize the mine as effectively as possible. For instance, some sea mines can be detonated only if the detonation is controlled from one side. The target orientation is defined as any combination of roll angle, yaw angle, and pitch angle, although the roll angle is generally not critical.

[0014] In exemplary embodiments, the underwater transducers of the sonar system of the first unmanned underwater vehicle are arranged vertically in a row. In particular, the sonar system of the first unmanned underwater vehicle consists of two underwater transducers. This sonar system generates the positional image for correcting the navigation of the second unmanned underwater vehicle. However, it is possible that, in addition to this rudimentary sonar system, which only allows vertical direction finding and has only one horizontal beam, another sonar system is arranged on the first unmanned underwater vehicle. This additional sonar system is preferably a system with a plurality of underwater transducers, enabling classic beamforming, for example, in the form of delay-and-sum beamforming. Alternatively or additionally, the underwater transducers of the sonar system of the second unmanned underwater vehicle are arranged vertically in a row.In particular, the sonar system of the second unmanned underwater vehicle consists of two underwater transducers. If the sonar systems of the first and second unmanned underwater systems have the same number of underwater transducers, or if the sonar systems are also identical in construction, this simplifies the comparison of the situational awareness images.

[0015] Sonar systems with an array of only a few, specifically two, underwater transducers arranged vertically in a row (in the sense of a column vector) allow only simple vertical beamforming, but not horizontal beamforming. In the horizontal direction, only one beam is available. This means that underwater sound, including reflections from objects, can only be received horizontally within a narrow area around the transducers' line of sight, the opening angle of the receiving sector. Within this area, however, the vertical angle of incidence of the reflection can be determined. In other words, it is possible to obtain information for each measurement within a horizontally limited disk. To ensure that information is not only obtained within this narrow area (i.e., within the disk), the underwater transducers can be rotated horizontally, for example, with a motor.Thus, it is possible to obtain information within a swivel range of the underwater sound transducer in successive measurements and, for example, to detect objects.

[0016] The sonar system can be mounted on the underwater vehicle in a rotatable, i.e., swiveling, manner. The motion unit, e.g., a motor, can perform the swiveling of the sonar system. In particular, the motion unit can continuously move, i.e., swivel, the sonar system to enable successive measurements in different horizontal viewing directions. That is, the motion unit then makes it possible to look in a different horizontal direction with each measurement to obtain information from a different perspective. For example, a minimum swivel angle can be defined, whereby for a new measurement, starting from the current viewing direction, a new viewing direction is set that differs from the current viewing direction by the minimum swivel angle. Thus, the entire possible field of view of the underwater vehicle can be continuously, incrementally, scanned.Thus, the situational awareness picture for course correction can be created when the first or second unmanned underwater vehicle is a safe distance from the object, i.e., the (potential) mine. However, it is also possible to focus the viewing directions on a specific object to build a point cloud of it. This allows for the creation of a detailed point cloud of the mine.

[0017] The sonar system of the first and / or the second unmanned underwater vehicle comprises, for example, an array of underwater sound transducers, each with at least one first and one second transducer, wherein the transducers of the array are each configured to convert underwater sound into a corresponding electrical signal. The array of underwater sound transducers can be a single-beam (row or column vector of underwater sound transducers) or a multi-beam (two-dimensional array of underwater sound transducers). In particular, the sonar system consists of two underwater sound transducers. Preferably, the underwater sound transducers of the sonar system are arranged in a (vertically oriented) row, i.e., linearly. Such an arrangement of underwater sound transducers can also be referred to as a column vector.In the main orientation of the array of underwater sound transducers, a (vertical) column vector extends along an axis from the water surface to the water bottom.

[0018] However, it is also possible that the sonar system has an array of only a few, in particular two, underwater transducers arranged horizontally in a row (in the sense of a line vector). Such a row arrangement of the transducers only allows for simple horizontal beamforming, but not vertical beamforming. The vertical viewing direction is then set by means of a control unit by maneuvering the unmanned underwater vehicle in different vertical viewing directions (e.g., by adjusting the pitch angle).

[0019] The first and second underwater sound transducers are each configured to convert underwater sound into a corresponding electrical signal. Preferably, the sonar system is further configured to emit an underwater sound signal to form an active sonar. Correspondingly, a signal processing unit is configured to detect the reflections in the underwater sound that correspond to the underwater sound signal. However, it is also possible to use a different sonar system to emit the underwater sound signal. Such an arrangement is a special case of active sonar and is referred to as a bistactic or multistatic sonar.

[0020] Furthermore, the minehunting system in the underwater vehicles, and optionally supplemented by one in the base station, includes an orientation and position sensor system designed to continuously determine the (current) poses of the unmanned underwater vehicle. A pose refers to the spatial position, i.e., the position and orientation of the unmanned underwater vehicle. The orientation and position sensor system can include any selection of sensors for orientation and / or position determination of the underwater vehicle, in particular a selection from a gyroscope, an accelerometer, and a magnetometer, as well as acoustic tracking from the base station. Preferably, the sensors of the underwater vehicle measure the respective property in all three spatial axes. The orientation and position sensor system can be implemented as a microelectromechanical system (MEMS).Preferably, the orientation and position sensor system measures movements and / or accelerations in all six spatial directions. Furthermore, the signal processing unit for determining the pose of the unmanned underwater vehicle may have access to data from external sensor systems, such as acoustic tracking.

[0021] This means the orientation and position sensor system can be located on the underwater vehicle, at a distance from the underwater vehicle (e.g., in a base station), or partially on the underwater vehicle and at a distance from it. Data exchange between the base station and the underwater vehicle can be carried out via a cable, such as a fiber optic cable. The data exchanged can include, for example, control information used to maneuver the underwater vehicle. Furthermore, the orientation and position sensor system can transmit the determined positions from the underwater vehicle to the signal processing unit in the base station.

[0022] The minehunting system further comprises the signal processing unit, which can be located in the underwater vehicles and / or the base station. The signal processing unit is configured to perform vertical direction formation (beamforming) based on the electrical signals from the first and second underwater transducers. Preferably, the beamforming is not implemented as classical delay-and-sum beamforming; instead, it is sufficient to determine the signal propagation time difference between the arrival at the first and second underwater transducers to ascertain the direction of incidence.

[0023] Using the current viewing direction of the sonar system, the vertical beamforming, and the position data of the unmanned underwater vehicle (i.e., its pose and vertical beamforming), and preferably also the time of reflection, the spatial position of reflections in the underwater sound can be continuously determined and plotted on a situational image. The viewing direction of the sonar system and the vertical beamforming provide the position relative to the underwater vehicle. Distance can be determined from the signal time of reflection. Using the orientation and position sensor system, the relative position can be converted into an absolute position, referenced to a predefined reference frame.

[0024] Preferably, only the strongest reflection from a vertical column vector is included in the positional image. With a two-dimensional array of underwater transducers, the vertical column vectors can be generated for different (horizontal) directions using beamforming, so that the strongest reflection for each direction is included in the positional image. This positional image can also be referred to as a 3D environment image. This is advantageous because the strongest reflection in each direction is typically the direct sound from an object, thus directly eliminating any multiple reflections that would lead to an incorrect position of the reflecting object. Furthermore, the strongest reflection is also the nearest and therefore most relevant object, so focusing on the strongest reflection is sufficient.Based on the sum of reflections, a contour of the unmanned underwater vehicle's surroundings can now be displayed in the situational awareness image. In other words, a 3D point cloud (sum of reflections) is generated from the individual sonar measurements. Due to the temporal sequence of the measurements and the resulting different angles to the reflecting object, a representation of the object from various perspectives is created. The situational awareness image can thus be a rudimentary representation of the underwater vehicle's surroundings, consisting solely of a sum of reflection points.

[0025] That is, exemplary embodiments show that the first unmanned underwater vehicle and the second unmanned underwater vehicle are each configured to build up the situational image using individual reflection points, with each underwater vehicle generating one reflection point per measurement. The sum of the reflections results in the point cloud.

[0026] Thus, it is possible to use the orientation and position sensor system to convert the relative positions of reflection points, such as objects, obtained by the sonar system into an absolute position relative to a predefined reference system. For example, the starting point of the underwater vehicle, i.e., the position of the underwater vehicle where the first measurement is taken, can serve as a reference point. A coordinate system can be established based on this reference point. Depending on the accuracy of the position determination, it is also conceivable to include a time loss factor for the reference point. Without additional support, the position will typically drift over a short period due to the double integration of the acceleration when using a MEMS.In this case, it is possible to delete points that are far removed in time from the situational picture, or to change the reference system variably, for example to the last known position or the current position.

[0027] Reflection points can thus be plotted on a map, the situational image. Using these reflection points, a 3D point cloud of the surroundings is created. If individual reflective objects are examined more closely, the object's surface can be mapped with reflection points. This even allows for the object's classification, for example, by comparing it to a 3D model of relevant objects, especially mines. The comparison can be performed using pattern recognition. It is also possible to train an artificial intelligence to compare the point cloud with known 3D models.

[0028] For the sake of completeness, it should be noted that the objects can usually only be viewed from one side, since unmanned underwater vehicles, especially remotely controlled, unmanned underwater vehicles, which are connected to a base station, usually a (surface) ship, via a signal cable, usually an optical fiber, can only travel against the current.

[0029] To classify the object as a mine, a point cloud of the mine can be used in addition to other sensors. For this purpose, the sensor system of the first unmanned underwater vehicle is repeatedly panned from different positions relative to the mine. This generates a detailed point cloud of the mine. The second unmanned underwater vehicle can then reconstruct at least a portion of this point cloud, used for correct positioning, in order to set the correct target position and, optionally, the correct target orientation.

[0030] In addition to or as an alternative to the propulsion unit, the underwater vehicle's viewing direction can also be adjusted using a control unit. The control unit is designed to receive commands to orient the unmanned underwater vehicle, particularly horizontally, so that the sonar system points in a predetermined direction. The control unit can therefore be, for example, a rudder or a swiveling propulsion unit, such as a swiveling propeller or a swiveling water jet propulsion system. The principle of changing viewing directions can be implemented in the same way as with the propulsion unit.

[0031] Similarly, a minehunting method using a first and a second unmanned underwater vehicle is disclosed, comprising the following steps: a) Navigating the first unmanned underwater vehicle on a predetermined course to an object in the water, b) Generating a situational awareness picture using a sonar system of the first underwater vehicle while underway, c) Identifying the object; d) Navigating the second unmanned underwater vehicle on the predetermined course to the object when the object is identified as a mine, e) Monitoring and, if necessary, adjusting the course of the second underwater vehicle based on the situational awareness picture of the first unmanned underwater vehicle; f) Disposing of the mine by the second unmanned underwater vehicle.

[0032] Preferred embodiments of the present invention are explained below with reference to the accompanying drawings. These show: Fig. 1: A schematic top view of a minehunting system with two unmanned underwater vehicles in a schematic representation; Fig. 2: a schematic representation of a situational image consisting of reflection points.

[0033] Before exemplary embodiments of the present invention are explained in detail below with reference to the drawings, it should be noted that identical, functionally equivalent or equivalent elements, objects and / or structures in the different figures are provided with the same reference numerals, so that the description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another.

[0034] Fig. Figure 1 shows a schematic diagram of a minehunting system 20 in a top view. The minehunting system 20 comprises a first unmanned underwater vehicle 22 and a second unmanned underwater vehicle 24. The first unmanned underwater vehicle 22 is optionally connected by a cable 26 to a base station 28, shown here as a (surface) vessel. The cable 26 is preferably at least one data cable, for example, an optical fiber. The second unmanned underwater vehicle 24 is optionally connected to the base station 28 by another cable 30. The other cable 30 is preferably at least one data cable, for example, an optical fiber.

[0035] The first underwater vehicle 22 travels on a predetermined course 32 towards an object 34 in the water. During the journey, a sonar system generates a situational awareness picture and identifies the object 34. If the object 34 is identified as a mine, the second unmanned underwater vehicle 24 travels on the predetermined course 32 towards the identified mine. Specifically, the second underwater vehicle 24 is deployed into the water after the mine has been identified. Preferably, the first underwater vehicle 22 returns to the base station 28 after identification. The base station 28 can then optionally recover the first underwater vehicle 22, i.e., bring it back on board.

[0036] The second unmanned underwater vehicle 24 controls its course based on the situational awareness of the first unmanned underwater vehicle 22 and adjusts its course as necessary. A course adjustment is necessary if the course of the second underwater vehicle differs from that of the first. The second unmanned underwater vehicle 24 can neutralize the mine once it reaches it.

[0037] Fig.Figure 2 shows a schematic representation of a position image 50. In the center, a sonar system 52 is depicted with a first underwater transducer 54 and a second underwater transducer 56. The sonar system 52 can be mechanically swiveled, i.e., rotated about an axis that is vertical in this representation. Swiveling is symbolized by the movement arrows 58, 58'. In the vertical direction, the two underwater transducers 54, 56 arranged one above the other enable directional determination. In the horizontal direction, with a single-beam sonar as depicted, directional determination within a measurement is not possible. This means that reflections of an underwater sound signal, emitted, for example, by one or both underwater transducers, can only be received from one direction. This narrow reception angle is symbolized by the boundaries 60.Reflections of the emitted underwater sound signal from other directions can be obtained by swiveling the sonar system. Information can only be received from one viewing direction per measurement. However, it is also possible, in principle, to use a multibeam sonar, i.e., a two-dimensional array of underwater sound transducers.

[0038] This means that one reflection point is entered into the situational image for each measurement. With multibeam sensors, i.e., a two-dimensional array of underwater transducers, one reflection point can also be entered into the situational image for each beam, i.e., for each direction in which the array of underwater transducers is virtually looking. By panning the sonar system, reflections can occur at different locations on an object in multiple measurements. Furthermore, by moving the underwater vehicle, i.e., relative to the object, additional perspectives of the object and thus additional reflection points can be obtained. Three reflection points 62, 62', 62" are shown as examples. It should be noted that the reflection points are shown with extreme symmetry for the sake of clarity. Such symmetry cannot be achieved in reality.Furthermore, it should be noted that the underwater vehicle has a position sensor unit to assign the individual reflections, which are detected relative to the underwater vehicle, to a correct absolute position. This allows for a comprehensive situational picture to be generated even while the underwater vehicle is underway, using only two underwater transducers.

[0039] The reflections can be received between a minimum distance of 64 and a maximum distance of 66 originating from the sonar system 52.

[0040] The disclosed (water) sound transducers are designed for underwater use, particularly in the sea. The transducers can convert underwater sound into an electrical signal (e.g., voltage or current) corresponding to the sound pressure, the underwater sound signal. Furthermore, it is possible for the transducers to convert an applied electrical voltage into underwater sound. The transducers can therefore be used as underwater sound receivers and / or underwater sound transmitters. The transducer material can be a piezoelectric material, for example, a piezoceramic. The transducers can be used for (active and / or passive) sonar (sound navigation and ranging). The transducers are preferably not suitable for, or are not used for, medical applications.

[0041] Although some aspects have been described in connection with a device, it is understood that these aspects also constitute a description of the corresponding process, so that a block or component of a device is also to be understood as a corresponding process step or as a feature of a process step. Similarly, aspects described in connection with or as a process step also constitute a description of a corresponding block, detail, or feature of a corresponding device.

[0042] The embodiments described above merely illustrate the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be obvious to other people skilled in the art. Therefore, it is intended that the invention be limited only by the scope of protection set forth in the following claims and not by the specific details presented herein by way of description and explanation of the embodiments. Reference symbol list: 20 mine hunting systems 22 first unmanned underwater vehicle 24 second unmanned underwater vehicle 26 (first) cable 28 Base station 30 additional (second) cable 32 predetermined course 34 objects 50 Situation picture 52 movement units 54 (first) water transducer 56 (second) water transducer 58 movement arrows 60° reception angle 62 reflection points 64 Minimum distance 66 Maximum distance

Claims

[1] Mine hunting system (20) with the following features: - a first and a second unmanned underwater vehicle; - wherein the first underwater vehicle (22) is trained to travel on a predetermined course (32) to an object (34) in the water, to generate a situational image (50) during the journey using a sonar system and to identify the object (34); - wherein the second unmanned underwater vehicle (24) is trained to travel on the predetermined course (32) to an object identified as a mine, wherein the second unmanned underwater vehicle (24) and / or a base station is trained to monitor and, if necessary, adjust the current course (32) of the second unmanned underwater vehicle based on the situational awareness (50) of the first unmanned underwater vehicle; - the second unmanned underwater vehicle (24) is trained to neutralize the mine. [2] Mine hunting system (20) according to claim 1, wherein the second unmanned underwater vehicle (24) is configured to generate a situational awareness picture (50) while underway using a sonar system, and wherein the second unmanned underwater vehicle or the base station is configured to control and, if necessary, adjust the current course (32) based on a comparison of the situational awareness picture of the first unmanned underwater vehicle and the second unmanned underwater vehicle. [3] Mine hunting system (20) according to claim 2, wherein the sonar system of the first unmanned underwater vehicle and the sonar system of the second unmanned underwater vehicle are identical in construction. [4] Mine hunting system (20) according to one of claims 2 or 3, wherein the first unmanned underwater vehicle (22) and the second unmanned underwater vehicle (24) are each configured to build up the situational picture (50) by means of individual reflection points, wherein the underwater vehicles each generate one reflection point per viewing direction for each measurement. [5] Mine hunting system (20) according to one of the preceding claims, wherein the first unmanned underwater vehicle (22) is configured to classify the mine and wherein the second unmanned underwater vehicle (24) is configured, based on the classification of the mine, to target a point of attack on the mine in order to render the mine harmless. [6] Mine hunting system (20) according to any one of the preceding claims, - wherein the sonar system comprises a plurality of underwater transducers, wherein the underwater transducers of the plurality of underwater transducers of the sonar system of the first unmanned underwater vehicle form an array, in particular arranged vertically in a row; and / or - wherein the second unmanned underwater vehicle has a sonar system with a plurality of underwater sound transducers, wherein the underwater sound transducers of the plurality of underwater sound transducers of the sonar system of the second unmanned underwater vehicle form an array, in particular arranged vertically in a row. [7] Mine hunting system (20) according to one of the preceding claims, wherein the sonar system of the first unmanned underwater vehicle consists of two underwater sound transducers and / or wherein the second unmanned underwater vehicle has a sonar system, wherein the sonar system of the second unmanned underwater vehicle consists of two underwater sound transducers. [8] Mine hunting system (20) according to one of the preceding claims, wherein the first unmanned underwater vehicle (22) is configured to process only the strongest reflection of the sonar system per viewing direction and to incorporate it into the situational image (50). [9] Mine hunting system (20) according to one of the preceding claims, wherein the first unmanned underwater vehicle (22) is a remotely controlled unmanned underwater vehicle. [10] Mine hunting system (20) according to one of the preceding claims, wherein the second unmanned underwater vehicle (24) is a remotely controlled unmanned underwater vehicle. [11] Method for mine hunting with a first and a second unmanned underwater vehicle (24) comprising the following steps: - Navigating the first unmanned underwater vehicle on a predetermined course (32) to an object (34) in the water - Generating a situational image using a sonar system of the first underwater vehicle while underway - Identifying the object; - Navigating the second unmanned underwater vehicle on the predetermined course (32) to the object when the object (34) is identified as a mine, - Check and, if necessary, adjust the course of the second underwater vehicle based on the situation picture (50) of the first unmanned underwater vehicle; - Disarming the mine using the second unmanned underwater vehicle.

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