Minehunting system

Abstract

The invention relates to a minehunting system (20) for detecting sea mines (2) in a body of water. The minehunting system comprises a sonar system (12), which is designed to search the body of water for sea mines (2), and a control unit (26) for navigation of a watercraft (28). The control unit (26) is designed to navigate the watercraft (28) in an undulating movement (30, 30') through the body of water during the search for sea mines (2).

Description

[0001] Mine hunting system

[0002] Description

[0003] The invention relates to the detection of sea mines by watercraft, in particular ships.

[0004] Mine-hunting vessels (also known as minehunting boats) are typically used for mine clearance, for example when a naval unit is required to pass through a mined area. Minehunting boats travel along parallel, straight tracks to systematically search the area of ​​interest. The vessels are equipped with a sonar system, usually a hull-mounted sonar, which illuminates a corridor in front of the vessel in order to detect potential mines along the tracks. The vessel is guided along the tracks as precisely as possible to avoid gaps (so-called holidays) in the search pattern. Random, unplanned deviations are referred to as navigation errors. If an object resembling a mine is detected, an unmanned underwater vehicle can be deployed to positively identify the mine and, if positive, destroy it.

[0005] However, it has been found that sea mines are not uniform in their reflection behavior. Even a slight change in the aspect angle can significantly alter the mine's target size, from a strong and clearly visible target to a nearly invisible echo. This means that only a small angle difference is necessary for a mine that is clearly visible in the reflected sonar signal to virtually disappear into the background noise. The angles from which the sea mine can be easily detected are referred to as the main and side lobes.

[0006] To illustrate the detection probability, reference is made to Fig. 1. A sea mine 2 that is exposed to sonar waves (i.e. sonar signals) of a certain frequency displays different reflection behavior depending on the spatial direction from which the sonar signals are incident. This means that the reflection behavior is angle-dependent. In the following, a two-dimensional 2D simplification is chosen in the representation in Fig. 1. There are directions in which strong reflection occurs, schematically represented by the main lobes 4. There are directions in which moderate reflection still occurs, schematically represented by the side lobes 6. There are directions in which only a reflection that is orders of magnitude weaker occurs, schematically represented by the minima 8. Angles between the main / side lobes and the minima can be very small, on the order of a few degrees. This reflection behavior is frequency-dependent.At other frequencies, different angles between main / side lobes and minima may result.

[0007] Fig. 2 shows a schematic plan view of an illumination sector 10 of a sonar system 12 with a resulting detection probability 14 of a sea mine as a function of its position relative to the sonar system 12. The detection probability is shown over the width, ie the axis transverse to the main line of sight of the sonar system.

[0008] Away from lanes 16, the angle of incidence on an object in the water or on the water bottom changes automatically as the vessel moves. This means that objects adjacent to lane 16 are viewed from different aspect angles, even on straight lanes 16. Even if the object initially lies in a minimum direction relative to sonar 12, the aspect angle will change throughout the entire sonar sweep. This makes it likely that the target will move away from its minimum aspect. This increases the detection probability.

[0009] Mines that lie exactly on the vessel's track 16, however, always exhibit the same angle of incidence of the sonar signal. In other words, there is only a slight change in the aspect angle on or close to track 16. Objects on or near the track are therefore always viewed with the same aspect. If the object happens to be in a "minimum direction" to the sonar, the aspect angle will hardly change during the entire sonar sweep. The target remains faint and is unlikely to be detected. This causes the detection probability curve on the track to have a small dip 18. The detection probability over the transverse distance to the track is a curved function. Far from the track, the detection probability is zero. In the sonar sector (also called the illumination sector), it increases rapidly and is approximately constant across the width. This curve will be approximated by a rectangular function.

[0010] The object of the present invention is therefore to create an improved concept for mine hunting.

[0011] This problem is solved by the subject matter of the independent patent claims. Further advantageous embodiments are the subject matter of the dependent patent claims.

[0012] Embodiments show a minehunting system for detecting sea mines in a body of water, in particular for sea mines with angle-dependent reflection behavior. Sea mines lying on the waterbed typically exhibit angle-dependent reflection behavior, but sometimes also anchor-linked mines. Nevertheless, the minehunting system can exploit its full potential with mines on the waterbed, since the contrast of anchor-linked mines compared to the volume reverberation of the water is greater than the contrast of mines on the waterbed compared to the waterbed. The minehunting system comprises a sonar system, in particular an active sonar system, and a control unit for navigating a watercraft. Optionally, the minehunting system also comprises the watercraft. The sonar system searches the body of water, in particular the waterbed, for sea mines. For this purpose, the sonar system can emit sonar signals and process reflections of the sonar signals.Objects that could be a sea mine can be detected in the processed reflections of the sonar signals. The control unit is designed to navigate the vessel in one (or more) serpentine lines through the water while searching for sea mines.

[0013] The idea is therefore to travel in serpentine lines instead of laying out the search paths as straight lines. This automatically changes the aspect ratio, even for mines that would otherwise lie exactly in a straight line. In particular, the serpentine lines are predetermined, preferably symmetrical. Furthermore, it is advantageous to select the serpentine lines so that there is a straight section to which the serpentine line runs symmetrically. The straight section can be the original straight path on which the vessel would normally travel. The straight section can also be referred to as the main search direction. This means that the control unit can navigate the vessel in a serpentine line through the body of water along the main search direction.The watercraft can now, controlled by the control unit, travel along a plurality of parallel main search directions to completely search a search area, provided the search area is larger than the sonar can cover while traveling along one main search direction. The control unit then steers the watercraft along each of the main search directions in a serpentine line. Preferably, the control unit is further configured to navigate the watercraft in a serpentine line through the water while searching for sea mines within the search area to be searched. A sine curve, for example, is suitable as a serpentine line.

[0014] This means that instead of laying out the tracks as straight lines, they are varied with a slight serpentine curve, specifically a sine curve. The vessel oscillates slightly from left to right. In other words, the vessel travels in curves almost continuously, or at least for 70% of its route, to create the serpentine line.

[0015] In exemplary embodiments, the control unit is configured to navigate the watercraft such that, following the serpentine line, the watercraft travels a further serpentine line that runs parallel to the serpentine line. It is advantageous to relate the parallel shift not to the vessel's navigation reference point (represented by the origin / angle of the quarter circle 10, see Fig. 2), but rather to the location of the greatest extent of the sonar sector (the circular arc of the quarter circle 10).

[0016] It should be noted that an exact parallel shift cannot be achieved in reality due to environmental influences and navigation inaccuracies, and the parallel shift is therefore subject to certain inaccuracies. Using parallel paths, it is thus possible to search a larger area not only lengthwise along the serpentine line or path, but also widthwise, without the serpentine lines creating gaps in the search area. Preferably, the serpentine lines are traveled in different directions, i.e., on the outward journey, the control unit navigates the watercraft along the serpentine line in one direction, and on the return journey, the control unit navigates the watercraft along the further serpentine line in the opposite direction.Furthermore, in order to be able to search the search area completely, it is possible for the control unit to navigate the watercraft in such a way that it travels any number of additional parallel serpentine lines.

[0017] Additionally or alternatively, it is possible to use a system for detecting sea mines on the waterbed with a first and a second of the described minehunting systems, wherein the control unit of the first minehunting system and the control unit of the second minehunting system are configured to navigate the corresponding vessels such that the vessels travel in parallel, serpentine lines. Thus, when using two vessels, it is possible to cover the same area in half the time as the vessel of a single minehunting system. Advantageously, the two minehunting systems use different sonar frequencies. This prevents the minehunting systems from interfering with each other.Furthermore, it is advantageous if it is ensured, for example by the control unit or by the crew, that when a mine is detonated, both vessels maintain a sufficient safety distance from the mine to be detonated.

[0018] In further embodiments, the control unit is designed to select an amplitude [A] of the serpentine line greater than or equal to the product of the sine of half the expected angle [er] between adjacent main and / or side lobes and the detection range [d] of the sonar system |A = | • d • sin (e )]. For example, amplitudes of the serpentine lines can result which are between 7m and 20m, preferably between 10m and 15m. This ensures that the sea mine can always be illuminated by the sonar system from an angle from which the sea mine has good reflection behavior (main or side lobe). In particular, the amplitude A of the serpentine line(s) should be sufficiently large to achieve, in conjunction with the wavelength, a sufficiently large aspect change which is greater than a typical angular range of a target size minimum.

[0019] Further embodiments show the control unit, which is designed to select a half-oscillation of the serpentine line such that the half-oscillation is shorter than the detection range of the sonar system. A half-oscillation (also referred to as half a period) is the duration required by the navigation unit to allow the watercraft to cross the straight section twice in succession. This ensures, particularly in conjunction with the previously described embodiment, that the sea mine is actually illuminated from an angle at which the sea mine exhibits good reflection behavior. Half the wavelength, i.e. half-attenuation, of this sine should be somewhat smaller than the distance between the maximum and minimum detection range, for example as determined in the sonar condition check. This ensures that an object on the path is scanned over the maximum possible angular range.Advantageously, a full wave is used instead of a half wave. This increases the probability of detecting the mine. In particular, the angular range in which the sea mine is illuminated is expanded. This ensures that sea mines with unusual reflection behavior, with a larger angle between two main lobes, can also be reliably detected. Furthermore, a sea mine with a typical reflection behavior is illuminated twice in one main reflection direction (main lobe). This way, in the unlikely event that the sea mine is missed during the first scan, it can still be detected during the second scan.

[0020] Similarly, a method for detecting sea mines in a body of water is disclosed, comprising the following steps: a) scanning the body of water for sea mines using a sonar system; b) navigating a watercraft in a serpentine line through the water while searching for the sea mines. Furthermore, a computer program is disclosed, comprising commands that, when executed on a computer, cause a watercraft to travel in a serpentine line through the body of water while searching for the sea mines. Optionally, the computer program can control a sonar system to scan the body of water or the bottom of the body of water for sea mines.

[0021] Preferred embodiments of the present invention are explained below with reference to the accompanying drawings. They show:

[0022] Fig. 1 : a schematic plan view of a sea mine showing the target dimension which changes greatly depending on the angle;

[0023] Fig. 2: a schematic plan view of an illumination sector of a sonar system to illustrate the detection probability of a sea mine depending on its position relative to the sonar system;

[0024] Fig. 3: a schematic side view of a watercraft with the sonar system;

[0025] Fig. 4: a schematic plan view of a route on which the control unit navigates the vessel.

[0026] Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it is pointed out 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.

[0027] Fig. 1 and Fig. 2 have already been described in the introduction to the description. In addition to the introductory description, the effective detection range (d) is shown in Fig. 2. The effective detection range describes the area from which usable reflections of the transmitted sonar signals can be received. The effective detection range lies within the limits between the maximum detection range 21 and the minimum detection range 21'. The maximum detection range is, for example, determined by the maximum range of the sonar system. The minimum detection range is typically the distance at which the first sonar signals hit the location of the sea mine, typically the waterbed. The maximum and minimum detection ranges can be determined, for example, using a sonar condition check. Here, a reflector is pulled through the water and a check is carried out to determine the area in which the reflector is visible to the sonar.

[0028] Fig. 3 shows a schematic side view of a mine hunting system 20 for detecting sea mines 2 in a body of water 22, in particular on a body of water 24. The mine hunting system 20 comprises the sonar system 12 and a control unit 26 and optionally a watercraft 28. The sonar system 12 searches the body of water 22, in particular the body of water 24, for sea mines. A control unit 26 handles the navigation of a watercraft 28. The control unit can be an on-board computer of the watercraft, which can navigate, i.e. drive or steer, the watercraft 28 partially autonomously or fully autonomously on predetermined or (in particular in real time) calculated routes. The control unit navigates the watercraft in serpentine lines through the water while searching for sea mines.

[0029] Fig. 4 shows a schematic plan view of a route on which the control unit can navigate the watercraft in serpentine lines 30. Preferably, the serpentine lines 30 are aligned symmetrically to a straight section 32 (shown in dashed lines). The lighting sector 10 of the watercraft is shown as a representative of the watercraft. Depending on the width of the search area, i.e., the extent of the search area transverse to the direction of travel, it is sufficient if one route (= outward journey) is traveled. If the search area is wider than the width of the lighting sector 10, the watercraft 28 travels several routes, i.e., for example, an outward and return journey as shown in Fig. 4. The serpentine line 30' of the return journey preferably runs parallel to the serpentine line of the outward journey.It is also possible to use two vessels traveling in the same direction (especially one after the other), so that the return route is replaced by the second vessel. Preferably, the serpentine lines of the outward and return routes run parallel, as shown in Fig. 4.

[0030] For example, an amplitude [A] of the serpentine line 30, 30' is greater than or equal to the product of the sine of half the expected angle [er] between adjacent main and / or side lobes and the detection range [d] (see Fig. 2) of the sonar system |A = • d • sin (er)]. The angle er depends on the type of sea mine. Typically, the angle er is a maximum of 10 degrees, but in individual cases it can be higher. However, the types of sea mines present in the search area are usually known. This makes it possible to select the amplitude of the serpentine lines depending on the sea mines being searched for.

[0031] In Fig. 4, the serpentine line is selected such that one half-cycle is shorter than the detection range of the illumination sector. The sea mine is then securely illuminated from an angle at which the sea mine exhibits good reflection characteristics. In the illustration in Fig. 4, it should be noted that the near range of the sonar system is not part of the detection range (see Fig. 4).

[0032] Fig. 2). In this respect, a half-oscillation, with the addition of approximately one more half-oscillation, lies within the detection range. However, as described above, it is advantageous to fit a full oscillation into the detection range instead of a half-oscillation.

[0033] Furthermore, an optional overlap area of ​​the search areas covered by one journey is shown using dotted lines. The better the navigation, the smaller the overlap area can be. Due to the preferred parallel shift of the two serpentine lines for the outward and return journeys, an overlap with the search areas that goes beyond safeguarding against navigation inaccuracies is necessary in order to avoid gaps. Ideally, i.e. with perfect navigation, no overlap is necessary even due to navigation inaccuracies. Although some aspects have been described in connection with a device, it is understood that these aspects also represent a description of the corresponding method, so that a block or component of a device can also be understood as a corresponding method step or as a feature of a method step.Similarly, aspects described in connection with or as a method step also represent a description of a corresponding block, detail, or feature of a corresponding device. The above-described embodiments are merely illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented in the description and explanation of the embodiments herein.

[0034] List of reference symbols:

[0035] 2 sea mines

[0036] 4 Main lobe

[0037] 6 side lobe

[0038] 8 Minimum

[0039] 10 Lighting sector

[0040] 12 Sonar system

[0041] 14 Detection probability

[0042] 16 Track that the watercraft travels

[0043] 18 Dent in the detection probability on the track

[0044] 19 Rectangular curve approximating the detection probability

[0045] 20 Mine hunting system

[0046] 22 bodies of water

[0047] 24 Waterbed

[0048] 26 Control unit

[0049] 28 watercraft

[0050] 30 serpentine lines

[0051] 32 straight stretches

Claims

Patent claims 1 . Mine hunting system (20) for detecting sea mines (2) in a body of water (22) having the following features: - a sonar system (12) designed to search the body of water (22) for sea mines (2); - a control unit (26) for navigating a watercraft (28); - wherein the control unit (26) is designed to navigate the watercraft (28) in a serpentine line (30, 30') through the body of water (22) during the search for sea mines (2).

2. Mine hunting system (20) according to claim 1, wherein the control unit (26) is designed to navigate the watercraft (28) in a predetermined serpentine line (30) through the body of water (22).

3. Mine hunting system (20) according to one of the preceding claims, wherein the control unit (26) is designed to select the serpentine line (30, 30') such that there is a straight section to which the serpentine line (30, 30') runs symmetrically.

4. Mine hunting system (20) according to one of the preceding claims, wherein the control unit (26) is designed to navigate the watercraft (28) in such a way that the watercraft, following the serpentine line, travels a further serpentine line which runs parallel to the serpentine line.

5. Mine hunting system (20) according to one of the preceding claims, wherein the control unit (26) is designed to select an amplitude [A] of the serpentine line greater than or equal to the product of the sine of half the expected angle [er] between adjacent main and / or side lobes and the detection range [d] of the sonar system [ / I = | • d • sin (e )].

6. Mine hunting system (20) according to one of the preceding claims, wherein the control unit (26) is designed to select a half-oscillation of the serpentine line such that the half-oscillation is shorter than the detection range of the sonar system.

7. Mine hunting system (20) according to one of the preceding claims, wherein the mine hunting system (20) comprises the watercraft (28).

8. Mine hunting system (20) according to one of the preceding claims, wherein the control unit is designed to select the serpentine line such that the watercraft travels in curves for at least 70% of the route.

9. Mine hunting system (20) according to one of the preceding claims, wherein the control unit (26) is designed to navigate the watercraft (28) in a serpentine line (30, 30') through the body of water (22) during the search for sea mines (2) within a search area to be searched.

10. Mine hunting system (20) according to one of the preceding claims, wherein the control unit (26) is designed to navigate the watercraft (28) along a main search direction in a serpentine line (30, 30') through the body of water (22).

11. System for detecting sea mines (2) in a body of water (22) having the following features: - a first and a second mine hunting system (20) according to one of the preceding claims; - wherein the control unit (26) of the first mine hunting system and the control unit (26) of the second mine hunting system are designed to navigate the corresponding watercraft such that the watercraft travel on parallel, shifted serpentine lines (30, 30').

12. Method for detecting sea mines (2) in a body of water (22) comprising the following steps: a) searching the body of water for sea mines (2) by means of a sonar system; b) Navigating a watercraft in a serpentine line (30) through the water while searching for the sea mines (2).

13. A computer program comprising instructions which, when executed on a computer, cause a watercraft to travel in a serpentine line (30) through the body of water (22) while searching for the sea mines (2).

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