Unmanned underwater vehicle

Abstract

The invention relates to a system for creating a positional image for an unmanned underwater vehicle (20), wherein the system has the following features: - a sonar system (22) comprising an array of waterborne sound transducers having at least a first and a second waterborne sound transducer (54, 56), wherein the waterborne sound transducers of the array of waterborne sound transducers are each designed to convert waterborne sound (30) into a corresponding electrical signal (32); - an orientation and position sensor system (24) which is designed to continuously determine poses (34) of the unmanned underwater vehicle (20); - a signal processing unit (26), wherein the signal processing unit (26) is designed to carry out a direction formation on the basis of the electrical signals (32) of the waterborne sound transducers of the array of waterborne sound transducers in order to continuously determine the position of reflections (62) in the waterborne sound (30) using a current viewing direction of the sonar system (22), the direction formation and the position data (34) of the unmanned underwater vehicle (20) and to enter said position into a positional image such that, on the basis of the sum of reflections (62), a contour of the surroundings of the unmanned underwater vehicle is depicted in the positional image.

Description

[0001] 2023,136

[0002] Unmanned underwater vehicle

[0003] Description

[0004] The invention relates to the creation of a situational image using inexpensive sonar systems that have only a small vertical opening angle.

[0005] Unmanned underwater vehicles (UAVs), especially remotely operated underwater vehicles (ROVs), often use inexpensive sonar systems. This is particularly true for ROVs used for minehunting. These UAVs are usually designed for single use and are therefore constructed as cost-effectively as possible. At least in the case of minehunting UAVs, the possibility of them being destroyed by a mine is taken into account. One cost factor for UAVs is the sonar system, specifically the number of transducers. Therefore, often only a small array with a few transducers is used, in the form of a multibeam (two-dimensional array) or singlebeam (one-dimensional array or column vector), often with only two transducers.

[0006] 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 2023,136 of the underwater sonar transducer's scan range in successive measurements and, for example, to detect objects. Specially trained sonar operators can detect objects within the received underwater sonar and, for example, restrict the maximum scan range to a smaller range in which the object is visible, in order to examine it more closely. However, information is only available for a portion of the scan range at any given time, so objects can only be detected by specially trained operators.

[0007] The object of the present invention is therefore to create an improved concept for unmanned underwater vehicles.

[0008] 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.

[0009] Exemplary embodiments show a system for generating a situational awareness picture for an unmanned underwater vehicle, in particular a remotely controlled underwater vehicle. The system includes a sonar system. The sonar system is preferably arranged on the underwater vehicle. The sonar system comprises an array of underwater sound transducers with at least a first and a second underwater sound transducer, wherein the underwater sound 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 transducers can also be called a column vector. In the main orientation of the array of underwater transducers, a (vertical) column vector extends along an axis from the water surface to the bottom. 2023.136.

[0010] 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).

[0011] When this revelation refers to an “underwater vehicle”, it always refers to an “unmanned underwater vehicle”.

[0012] 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, the 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 bistastatic or multistatic sonar. The underwater vehicle is preferably used for mine hunting.

[0013] Furthermore, the system comprises an orientation and position sensor system configured to continuously determine the (current) poses of the unmanned underwater vehicle. A pose is defined as 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. Preferably, the sensors measure the respective property in all three spatial axes. The orientation and position sensor system can be implemented as a microelectromechanical system (MEMS). 2023.136

[0014] 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 (UAV) may have access to data from external sensor systems, such as acoustic tracking. This means the orientation and position sensor system can be located on the UAV, at a distance from the UAV (e.g., in a base station), or partially on the UAV and at a distance from the UAV. Data exchange between the base station and the UAV can be achieved via a cable, such as a fiber optic cable. Data exchanged could include, for example, control information used to maneuver the UAV.Furthermore, the orientation and position sensor system can send the determined poses from the underwater vehicle to the signal processing unit in the base station.

[0015] The system further comprises a signal processing unit, which is located either within the underwater vehicle or at a distance from the underwater vehicle, for example, in a 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 classic 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.

[0016] 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 travel time of the reflection, the spatial or local 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. A 2023.136

[0017] Distance can be determined via the signal travel time of the reflection. Using the orientation and position sensor system, the relative position can be converted into an absolute position, referenced to a given reference frame.

[0018] Preferably, only the strongest reflection from a vertical column vector is included in the situational image. With a two-dimensional array of underwater sound transducers, the vertical column vectors can be generated for various horizontal directions using beamforming. The situational 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 environment can now be displayed in the situational image.In other words, the individual sonar measurements are used to create a 3D point cloud (sum of reflections). 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 resulting situational image can therefore be a rudimentary representation of the underwater vehicle's surroundings, consisting solely of a sum of reflection points.

[0019] One idea of ​​the present disclosure is therefore to use the orientation and position sensor system to convert the relative positions of reflection points, for example objects, obtained by the sonar system, into an absolute position relative to a given 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. 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 is usually determined by double integration of the 2023.136

[0020] Acceleration can drift when using a MEMS over a short period. In this case, it is possible to delete points that are far removed in time from the situational image, or to change the reference frame variably, for example to the last known position or the current position.

[0021] Based on this reference point, a coordinate system can be established. Reflection points can then be plotted on a map, creating a situational image. Using these reflection points, a 3D point cloud of the surroundings is generated. By examining individual reflective objects more closely, the object's surface can be mapped using reflection points. This even allows for the object's classification, for example, by comparing it to a 3D model of relevant objects, particularly mines. This comparison can be performed using pattern recognition. It is also possible to train artificial intelligence to compare the point cloud with known 3D models.

[0022] Due to the sheer number of reflection points and the potential for computer assistance, even sonar operators without specialized training can detect and, at best, classify objects in the water. It should be noted for the sake of completeness that objects can generally only be viewed from one side, as unmanned underwater vehicles, especially remotely operated underwater vehicles (ROVs) connected to a base station (usually a surface vessel) via a signal cable (most often an optical fiber), can only travel against the current.

[0023] Preferably, the unmanned underwater vehicle is configured to vary the viewing direction of the underwater sound transducers such that a comprehensive situational image is generated. The directions in which an object of interest is located can preferably be selected as the viewing direction. In exemplary embodiments, a movement unit of the underwater vehicle can be configured to adjust the viewing direction of the sonar system independently of the direction of travel of the unmanned underwater vehicle in order to enable different horizontal viewing directions in a short time. The sonar system can, for example, be rotatably, i.e., pivotably, mounted on the underwater vehicle. The movement unit, e.g., a motor, can perform the pivoting of the sonar system. In particular, 2023.136, the movement unit can continuously move, i.e., pivot, the sonar system to enable successive measurements in different horizontal viewing directions.The motion unit then allows the system to look in a different horizontal direction with each measurement, in order to obtain information from a different perspective. For example, a minimum pan angle can be defined, whereby for a new measurement, a new viewing direction is set starting from the current viewing direction, which differs from the current viewing direction by the minimum pan angle. Thus, the entire possible field of view of the underwater vehicle can be continuously and incrementally scanned. However, it is also possible to focus the viewing directions only on a specific object in order to build a point cloud of it.

[0024] 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.

[0025] In further embodiments, the signal processing unit is designed to compensate for deviations in the orientation and position sensor system that occur over time, based on a comparison of current reflections with the positional image. That is, if a known point in the positional image is recorded again, the deviation between the newly recorded point and the known point can be compensated. This results in a recursive, self-calibrating system. This is advantageous because the orientation and position sensor system, or one or more sensors of the orientation and position sensor system (especially a MEMS), can drift over time. Thus, it can happen that the position information is provided with an ever-increasing inaccuracy over time. If reflections from essentially known positions are received, it is possible to recalibrate the orientation and position sensor system.to recalibrate the affected sensor. This means that the orientation and position sensor system, or the affected sensor, is realigned with the reference system. This allows reflections from unknown positions to be incorporated back into the situational image.

[0026] Several approaches to implementing such a recursive system are grouped under the term SLAM in autonomous robotics and are used, for example, in robotic vacuum cleaners. The goal is to generate an accurate map of the unknown environment using imaging sensors, enabling the robot to navigate within this mapped environment. Here, too, recalibration of the position sensors via the imaging sensors is possible, for example, in buildings where no absolute positioning system like GPS is available. The application of this technique in underwater vehicles, particularly those with inexpensive, single-use technology such as mine clearance vehicles, is not known.

[0027] Preferred embodiments of the present invention are explained below with reference to the accompanying drawings. These show:

[0028] Fig. 1 : a schematic top view of an unmanned underwater vehicle in a principle representation with a section of a sonar system in a schematic frontal representation;

[0029] Fig. 2: a schematic representation of a situational image consisting of reflection points.

[0030] 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 2023.136 shown in different exemplary embodiments

[0031] The description of these elements is interchangeable or can be applied to each other.

[0032] Fig. 1 shows a schematic diagram of an unmanned underwater vehicle 20 in a top view. The underwater vehicle 20 comprises a sonar system 22, an orientation and position sensor system 24, and a signal processing unit 26. The signal processing unit 26 can also be located outside the underwater vehicle 20, for example, in a base station (not shown). Furthermore, it is possible that the orientation and position sensor system 24, preferably at most a portion thereof, is located in the base station.

[0033] The sonar system 22 is shown again in a frontal view below the underwater vehicle. This view shows a first and a second underwater sound transducer 54, 56 of an array of underwater sound transducers. The first underwater sound transducer 54 is arranged above the second underwater sound transducer 56. The underwater sound transducers 54, 56 are each configured to convert underwater sound 30 into a corresponding electrical signal 32. Furthermore, the underwater sound transducers 54, 56, or at least one of the two underwater sound transducers, are configured to emit an underwater sound signal 30', preferably a ping or alternatively a sweep. The sonar system is then an active sonar. The sonar system 22 has a beamwidth 31 within which the underwater sound signal 30' can be emitted and the underwater sound 30 can be received. Preferably, the viewing direction of the sonar system 22 can be swivelled so that the opening angle shifts according to the movement arrow 33.The viewing direction of the sonar system 22 is the direction in which the most transmission power is emitted, or in which the greatest reception sensitivity exists. It should be noted that the beamwidth 31, like the entire representation in Fig. 1, is not to scale. The beamwidth is usually only a few degrees, but has been greatly enlarged for better visualization.

[0034] The orientation and position sensor system 26 continuously determines poses 34 of the unmanned underwater vehicle 20 and transmits them to the signal processing unit 26. 2023.136

[0035] The signal processing unit 26 can perform vertical direction finding based on the electrical signals 32 from the first and second underwater sound transducers 54, 56. Using the current viewing direction of the sonar system 22, the vertical direction finding, and the poses 34 of the unmanned underwater vehicle 20, the unit continuously determines the position of reflections of the underwater sound signal 30' from an object 36 within the underwater sound field 30 and plots this position in a situational image. Determining the travel time of the underwater sound signal 30' can improve the position determination of the reflections. Based on the sum of the reflections, the signal processing unit 26 can then display a contour of the environment of the unmanned underwater vehicle 20 in the situational image.

[0036] Optionally, the underwater vehicle 20 has a motion unit 38. The motion unit 38 can control the panning of the sonar system 22, thus varying the viewing direction of the sonar system.

[0037] Optionally, the underwater vehicle also features a control unit 40, shown here as a rudder. In addition to or as an alternative to the movement unit, the control unit can orient the underwater vehicle 20 such that the sonar system 22 is swiveled, thus varying the direction of view of the sonar system.

[0038] Fig. 2 shows a schematic representation of a position image 50. In the center, a sonar system 22 is shown with a first underwater transducer 54 and a second underwater transducer 56. The sonar system 22 can be mechanically swiveled, i.e., rotated about an axis that is vertical in this representation. Swiveling is symbolized by the 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. That is, 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.

[0039] 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.

[0040] The reflections can be received between a minimum distance of 64 and a maximum distance of 66 originating from the sonar system 22.

[0041] 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 as underwater sound transmitters. The transducers can utilize a piezoelectric material, such as a piezoceramic, as the sensing material. 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.

[0042] 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.

[0043] 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.

[0044] 2023,136

[0045] Reference symbol list:

[0046] 20 underwater vehicles

[0047] 22 Sonar system

[0048] 24 Orientation and position sensor system

[0049] 26 Signal processing unit

[0050] 30 Water Sound

[0051] 30' underwater sound signal

[0052] 31 Opening angles

[0053] 32 electrical signal (underwater sound signal)

[0054] 33 Movement arrow

[0055] 34 Posen

[0056] 36 Object from which the underwater sound signal is reflected

[0057] 38 movement units

[0058] 40 Control unit

[0059] 50 Situation picture

[0060] 54 (first) water transducer

[0061] 56 (second) water transducer

[0062] 58 movement arrows

[0063] 60° reception angle

[0064] 62 reflection points

[0065] 64 Minimum distance

[0066] 66 Maximum distance

Claims

2023,136 Patent claims 1. System for creating a situational awareness picture for an unmanned underwater vehicle (20), wherein the system has the following features: - a sonar system (22) comprising an array of underwater sound transducers with at least one first and one second underwater sound transducer (54, 56), wherein the underwater sound transducers of the array of underwater sound transducers are each configured to convert underwater sound (30) into a corresponding electrical signal (32); - an orientation and position sensor system (24) designed to continuously determine poses (34) of the unmanned underwater vehicle (20); - a signal processing unit (26), wherein the signal processing unit (26) is configured to perform direction formation based on the electrical signals (32) of the underwater sound transducers of the array of underwater sound transducers, in order to continuously determine the position of reflections (62) in the underwater sound (30) and to plot them in a situational image using a current viewing direction of the sonar system (22) as well as the direction formation and the position data (34) of the unmanned underwater vehicle (20), so that a contour of the environment of the unmanned underwater vehicle is represented in the situational image based on the sum of reflections (62).

2. System according to claim 1, wherein the unmanned underwater vehicle (20) comprises a motion unit (38), wherein the motion unit (38) is configured to adjust a viewing direction of the sonar system (22) independently of a direction of travel of the unmanned underwater vehicle (20) in order to enable different horizontal viewing directions in a short time.

3. System according to claim 2, wherein the motion unit (38) is configured to continuously move the sonar system (22) to enable successive measurements in different horizontal viewing directions. 2023,136 4. System according to one of the preceding claims, wherein the unmanned underwater vehicle (20) comprises a control unit, wherein the control unit is configured to receive commands to align the unmanned underwater vehicle, in particular to align it horizontally, such that the sonar system (22) points in a predetermined direction of view.

5. System according to one of the preceding claims, wherein the signal processing unit (26) is configured to compensate for a deviation of the orientation and position sensor system (24) that occurs over time, based on a comparison of current reflections (62) with the situational image.

6. System according to one of the preceding claims, wherein the waterborne transducers (54, 56) of the array of waterborne transducers are arranged in a row.

7. System according to one of the preceding claims, wherein the array of water transducers consists of two water transducers.

8. System according to one of claims 6 or 7, wherein the waterborne transducers of the array of waterborne transducers are arranged one below the other in the main application orientation.

9. System according to one of the preceding claims, wherein the sonar system (22) is configured to emit an underwater sound signal (32) and wherein the signal processing unit (26) is configured to detect the reflections (62) corresponding to the underwater sound signal (32) in the underwater sound (30).

10. System according to one of the preceding claims, wherein the signal processing unit (26) is configured to include only the strongest reflection from a vertical column vector of the array of water transducers in the situational image. 2023,136 11. System according to one of the preceding claims, wherein the unmanned underwater vehicle (20) is a remotely controlled unmanned underwater vehicle. 16

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