Platform for the detection of turbulence caused by the wake of underwater vehicles

Abstract

The invention relaere is disclosed a platform (20) for detecting turbulence caused by the wake of underwater vehicles (22) with a sensor (24) and a signal processing unit (26). The sensor (24) is designed to detect a magnetic field surrounding the sensor and to output a corresponding electrical signal (27). The signal processing unit (26) is designed to obtain the electrical signal (27) and, based on successive measurements, to determine magnetic field changes caused by turbulence in the wake of accelerated ions as a superposition of the static geomagnetic field.

Description

[0001] Platform for detecting turbulence caused by the wake of underwater vehicles

[0002] Description

[0003] The invention relates to the detection of underwater vehicles using sensors or sensor arrangements that differ from classical sonars currently used for the detection of underwater vehicles.

[0004] Depending on their configuration, traditional sonars can transmit (active sonar) and / or receive (active and passive sonar) underwater sound at frequencies between 50 Hz and 100 kHz. However, modern underwater vehicles are becoming increasingly quieter and hardly emit any underwater sound at low speeds. This makes detection and positioning using passive sonar significantly more difficult. Positioning using active sonar has the disadvantage that the sound emitter is easily detected. Locating an underwater vehicle (especially an enemy one) using an underwater vehicle (your own) is therefore impossible without revealing your own position. This is precisely what is not desired.

[0005] The object of the present invention is therefore to create an improved concept for detecting underwater vehicles.

[0006] 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.

[0007] A multitude of concepts are now disclosed that can be divided into three categories. The concepts in the first category deal with the detection of the underwater vehicle itself. The concepts in the second and third categories each deal with the detection of the wake of the underwater vehicle. The concepts in the third category exploit physical effects to detect the water vortices in the wake, and the concepts in the second category could also function without water vortices. Each concept uses one sensor or a plurality of sensors, each of which determines a physical quantity based on a physical effect. One physical effect is exploited per concept.

[0008] The sensors can be arranged individually or in any number and combination on a platform. In other words, it is possible to use a single physical effect to detect the underwater vehicle. However, a plurality of physical effects can also be used in combination to detect the underwater vehicle. The more physical effects used, the higher the probability of detecting the underwater vehicle. It is also possible to use the sensor(s) used together with a conventional sonar, preferably a passive sonar. Finally, one embodiment discloses how one or more of the sensors of the second or third category can be attached to the (own) underwater vehicle as a platform for detecting the (particularly enemy) underwater vehicle.Furthermore, at least some of the concepts described can also be used to classify previously detected underwater contacts. That is, to determine their exact type. This is possible because different underwater vehicles produce individual, type-dependent manifestations of the physical effect under consideration.

[0009] Category 1 :

[0010] Embodiments of concept 1a (1st category, concept a) show a platform for detecting underwater vehicles with an underwater antenna and a signal processing unit. In this and the following concepts, the platform can be considered, for example, a surface platform, for example an autonomous or conventional watercraft or a floating buoy, or an underwater platform, for example an autonomous underwater vehicle or a manned underwater vehicle (submarine), a homing torpedo, or an underwater buoy. The underwater antenna has a plurality of underwater sound transducers. The underwater sound transducers of the plurality of underwater sound transducers are designed to convert underwater sound into an electrical signal corresponding to the sound pressure.The signal processing unit is designed to receive the electrical signals from the underwater sound transducers and to detect infrasound emitted by the underwater vehicle within the underwater sound. Infrasound is generated, for example, by the underwater vehicle's propulsion engines but also by the displacement of water, known as flow noise.

[0011] The idea behind concept 1a is to detect underwater sound not only in the familiar sound range of conventional sonars >50 Hz, but also in the infrasound range <15 Hz, especially <10 Hz, preferably <7 Hz. In principle, underwater sound transducers, such as piezoceramic underwater sound transducers, can detect sounds at these frequencies. However, such low frequencies are filtered out in almost all modern sonar systems to improve the signal-to-noise ratio in the actual, higher-frequency useful band. Furthermore, suitable signal processing is lacking. A major advantage of this concept is that the underwater vehicle can be detected even when the underwater sound transducers are located outside the underwater vehicle's wake.

[0012] Embodiments show that the underwater antenna has a length of at least 50 m, preferably at least 75 m, at least 100 m, at least 200 m, at least 350 m, or at least 500 m. These antenna lengths allow the detection of infrasound in water according to a half-wave antenna.

[0013] Further embodiments show that the platform has an underwater vehicle, and the underwater antenna comprises a towed antenna designed to be towed by the underwater vehicle. If an underwater vehicle is used to detect the (enemy) underwater vehicle, it is advantageous to use a towed antenna as the underwater antenna. This makes it possible to decouple the underwater antenna from the noise of the towed underwater vehicle. Furthermore, antenna lengths significantly greater than 100 m can be realized, allowing even noises with frequencies less than or equal to 1 Hz to be detected. For a half-wave antenna, this would be an underwater antenna length of 750 m or more.

[0014] It is also possible to use an antenna permanently mounted on the underwater vehicle, such as a side-view antenna, as an underwater antenna. However, the length of the underwater antenna is limited by the length of the underwater vehicle.

[0015] Furthermore, it is possible to form an antenna from the underwater sound transducers of the antenna permanently mounted on the underwater vehicle and the towed antenna in order to realize even greater lengths of the underwater antenna. That is, in one embodiment, the underwater vehicle has at least one of the plurality of underwater sound transducers, and the towed antenna has at least one of the plurality of underwater sound transducers, so that the underwater vehicle and the towed antenna each comprise a portion of the underwater antenna.

[0016] In further embodiments, the signal processing unit is configured to perform beamforming based on the infrasound to determine the direction in which the underwater vehicle is located. This makes it possible to determine not only the presence of the (enemy) underwater vehicle, but also its position.

[0017] Similarly, a method for detecting underwater vehicles is disclosed, comprising the following steps: - converting underwater sound into an electrical signal corresponding to the sound pressure; - analyzing the electrical signal to detect infrasound emitted by the underwater vehicle in the underwater sound.

[0018] Embodiments of concept 1b (1st category, concept b) disclose an underwater platform (20) for detecting underwater vehicles, comprising a magnetic anomaly detector (MAD) and a signal processing unit. The magnetic anomaly detector is configured to detect the Earth's magnetic field and output a corresponding MAD sensor signal. The signal processing unit receives the MAD sensor signal and can detect a deviation of the Earth's magnetic field caused by the underwater vehicle.

[0019] The idea behind Concept 1b is to detect a distortion of the Earth's magnetic field caused by the (enemy) underwater vehicle, particularly the ferromagnetic materials such as steel installed within it. The effects on the Earth's magnetic field are minimal but measurable. The detection of underwater vehicles using MAD sensors from the air is known. This allows aircraft or helicopters to fly over bodies of water and detect underwater vehicles using the MAD sensors.

[0020] Now, communication between an aircraft or helicopter and an underwater platform, such as an underwater vehicle, is not trivial. Therefore, it is advantageous for the underwater vehicle to be able to detect the (enemy) underwater vehicle in order to create a situational awareness for the underwater vehicle. This method for detecting the (enemy) underwater vehicle has the significant advantage that the magnetic signature of an underwater vehicle can only be reduced with great effort, thus offering good detection capabilities.

[0021] Embodiments show that the underwater platform has an underwater vehicle and a traction device. The traction device is designed to be pulled by the underwater vehicle, in particular a submarine. A suitable traction device can be, for example, a rope or a strap, or a combination of a rope or a strap and a towed antenna. The magnetic anomaly detector is arranged on the traction device so that the magnetic anomaly detector is arranged away from the underwater vehicle during operation. For example, the magnetic anomaly detector can be arranged at the end of a towed sonar. This is advantageous because it creates a very large distance between the magnetic anomaly detector and the underwater vehicle. The influence of the hostile underwater vehicle on the magnetic anomaly detector is thus reduced. This means that (enemy) underwater vehicles can be detected more reliably.Preferably, the magnetic anomaly detector has a distance of at least 100m, preferably at least 250m, more preferably at least 500m, more preferably at least 1000m or more preferably at least 1500m.

[0022] Similarly, a method for detecting underwater vehicles is disclosed, comprising the following steps: - detecting the Earth's magnetic field using a magnetic anomaly detector and outputting a corresponding MAD sensor signal; - detecting a deviation of the Earth's magnetic field by the underwater vehicle in the MAD sensor signal.

[0023] Category 2:

[0024] Embodiments of concept 2a (2nd category, concept a) show a platform for detecting underwater vehicles with a sensor and a signal processing unit. The sensor is designed to chemically analyze seawater and to output a proportion of at least one predefined substance in a corresponding analysis result. For example, the sensor can determine a concentration of the substance in the seawater. In the following embodiments, various suitable substances are described that indicate the detection of an underwater vehicle, in particular a manned underwater vehicle. Since categories 2 and 3 describe devices and methods for detecting the wake of the underwater vehicle, it is advantageous in each of these concepts to continuously, i.e.Measurements are taken with the sensor at least at intervals of less than 10, preferably less than 1 second, more preferably at intervals of less than 100 milliseconds. This enables the platform, in particular a mobile platform, to move with the sensor in the wake of the underwater vehicle and, once the wake is left, to find it again as quickly as possible.

[0025] The signal processing unit is configured to determine, based on the analysis result, a deviation from a previous analysis result or a deviation from an expected analysis result in order to detect the underwater vehicle. A deviation, particularly a significant one, from a previous analysis result can indicate that the platform's sensor has moved into or out of the wake of the (enemy) underwater vehicle. A deviation from an expected analysis result can, for example, indicate that the sensor is located in the wake of an underwater vehicle, even without having previously determined a reference value.

[0026] The idea of ​​concept 2a is to detect chemical substances released by an underwater vehicle in the wake of the underwater vehicle and to infer the presence of the underwater vehicle.

[0027] Embodiments show that the signal processing unit is configured to query a database for the expected analysis result based on a current position of the underwater platform. The database can be, for example, a nautical chart in which concentrations of the predefined substance are entered. This allows regional differences in the proportion of the predefined substance in the seawater to be taken into account. Thus, for example, even without a prior analysis result, it can be determined with greater accuracy whether the sensor is located in the wake of an underwater vehicle or not. In other words, the background level of the predefined substance can be determined, so that an increased concentration can be determined based on the background level.

[0028] In a further embodiment, the sensor is configured to determine a proportion of zinc, nickel, copper, hydrogen, or hydrocarbon as a predefined substance in the seawater. The signal processing unit is configured to compare the determined proportion of the predefined substance with a proportion of the predefined substance in a previous analysis result or with an expected proportion of the predefined substance in order to detect the underwater vehicle. The previous analysis result is preferably the analysis result of the last, i.e., immediately preceding, measurement.

[0029] Zinc is a suitable predefined material because underwater vehicles typically have zinc-containing sacrificial anodes. These sacrificial anodes prevent, for example, the hull or other external parts of the underwater vehicle from rusting.

[0030] Nickel is suitable as a predefined material because pipes such as cooling water pipes of underwater vehicles that come into contact with seawater typically contain nickel.

[0031] Copper is a suitable predefined material because it is also used for pipes on underwater vehicles that come into contact with seawater. Copper is also used in antifouling paint to protect the underwater vehicle against growth and other contaminants.

[0032] Hydrogen is a suitable predefined substance because it is a waste product of oxygen production. Oxygen is needed, for example, for the crew to breathe. The hydrogen content in seawater can be quickly and reliably determined using a pH analysis of the seawater, for example, as a chemical analysis.

[0033] In one embodiment, in addition to or alternatively to determining the proportion of zinc, nickel, copper, hydrogen, or hydrocarbon as a predefined substance in the seawater, the sensor is designed to determine a proportion of a hydrocarbon, in particular diesel, in the seawater. The signal processing unit is designed to compare the determined proportion of the hydrocarbon with the proportion of the hydrocarbon in a previous analysis result or with an expected proportion of hydrocarbon in order to detect the underwater vehicle. This makes it possible to detect small amounts of diesel in the wake of the underwater vehicle in diesel-powered underwater vehicles, since the diesel tanks are typically open at the bottom. Thus, seawater can replace the used diesel in order to keep the change in the buoyancy of the underwater vehicle as small as possible.Although the majority of the diesel floats on top due to its lower density compared to seawater, it is unavoidable that small amounts of diesel mix with the seawater and thus enter the wake of the underwater vehicle. In some versions, the sensor is designed to perform atomic absorption spectroscopy, laser-induced plasma spectroscopy, energy-dispersive X-ray spectroscopy, or at least two of the aforementioned methods to chemically analyze the seawater. Using the aforementioned methods, it is possible to analyze the seawater for predetermined substances.

[0034] In further embodiments, the sensor is configured to output proportions of a plurality of predefined substances in the seawater. Alternatively, the platform comprises a plurality of sensors, wherein the sensor is one of the plurality of sensors, wherein the sensors of the plurality of sensors are configured to chemically analyze the seawater and output a proportion of a plurality of predefined substances in the seawater in a respective corresponding analysis result. In other words, one sensor or a plurality of sensors can determine proportions of different substances in the seawater.

[0035] In these embodiments, the signal processing unit is designed to determine a chemical signature from the plurality of predefined substances based on the analysis results as a deviation of the proportions of the predefined substances from a previous analysis result or a deviation from an expected analysis result in order to detect, in particular to classify, the underwater vehicle. In other words, the signal processing unit can estimate a natural occurrence of the predefined substances at the current position of the platform. The estimate can be based on a previous measured value at which the platform performed a measurement outside the wake of an underwater vehicle. Additionally or alternatively, the estimate can be based on values ​​from a database. For example, the database is embodied in the form of a nautical chart in which concentrations of the predefined substances at various positions are entered.

[0036] Based on the chemical signature, a more robust detection of the underwater vehicle is possible. Furthermore, it is possible to classify the underwater vehicle using the chemical signature. For example, the types of underwater vehicles differ in the amount of diesel that is flushed from the fuel tanks or in the length of the pipelines that are in contact with seawater. This changes the chemical signature of the underwater vehicle.

[0037] Furthermore, the sensor(s) is / are designed to determine the isotopic composition of the detected substance(s) to enable classification of the underwater vehicle. The isotopic composition, e.g., of the diesel or the detected metals, makes it possible to determine the origin of the substances. Based on the origin, it is possible to assign the underwater vehicle to an underwater vehicle, in particular to a nation to which the underwater vehicle belongs.

[0038] The analysis of the isotopic composition in combination with the chemical signature of the underwater vehicle enables an even more precise classification of the underwater vehicle than the respective methods allow individually.

[0039] Similarly, a method for detecting underwater vehicles is disclosed, comprising the following steps: - chemically analyzing seawater to output a proportion of at least one predefined substance in an analysis result; - determining, based on the analysis result, a deviation from a previous analysis result or a deviation from an expected analysis result in order to detect the underwater vehicle.

[0040] Embodiments of concept 2b (2nd category, concept b) show a platform for detecting nuclear-powered underwater vehicles. The platform has a sensor and a signal processing unit. The sensor is designed to detect radioactive radiation and output a corresponding radiation signal. The sensor can be a Geiger counter. It is advantageous that manned underwater vehicles usually already have a Geiger counter on board. This can be mounted on the periscope, for example. Using the Geiger counter, the crew can check before disembarking whether the exit location is radioactively contaminated, for example by a nuclear bomb. This Geiger counter can also be used underwater to detect radioactive radiation in the wake of the underwater vehicle. Additionally or alternatively, a separate sensor can also be mounted on the platform.Optionally, the sensor can be integrated into a pressure-tight housing that allows radioactive radiation to pass through. The housing can be made of glass, for example, at the relevant points where the radiation is intended to pass through, allowing radioactive radiation to penetrate into the housing. Gamma radiation, in particular, can penetrate glass.

[0041] The signal processing unit is configured to receive the radiation signal and determine a deviation from a previous radiation signal or a deviation from an expected radiation signal to detect the underwater vehicle. The expected radiation signal may include or consist of the terrestrial radiation at the location. The previous radiation signal may originate from a measurement outside the wake of a nuclear-powered underwater vehicle near the current location.

[0042] The idea behind Concept 2b is to be able to detect nuclear-powered underwater vehicles, such as nuclear submarines, even if they emit no or very little noise. Since nuclear-powered underwater vehicles inevitably emit at least small amounts of radioactivity, such as gamma radiation, this can be detected in the water.

[0043] In embodiments, the platform is designed as a (particularly stationary) underwater platform or at least comprises one. The underwater platform is arranged on the waterbed or fastened to the waterbed, in particular the seabed. This means that the underwater platform can have a greater density than water and sink to the waterbed. The underwater platform can be fastened there, for example anchored. Alternatively, the underwater platform can also be buoyancy-neutral or have a lower density than the surrounding (sea) water. In this case, the underwater platform can be fastened to the waterbed, for example by means of a rope. The underwater platform is preferably arranged in the shipping channel, for example in a narrow water passage, such as in a strait. This has the advantage that underwater vehicles are forced to pass close to the underwater platform.Furthermore, the underwater platform is then necessarily located near the underwater vehicle. This makes it possible to directly detect atomic radiation emitted by the underwater vehicle and thus classify the underwater vehicle, for example, based on an isotopic analysis of the radioactive radiation. Although radioactive radiation can also be detected at greater distances, it is only indirectly via water molecules ionized by the radioactive radiation. This allows a distinction between nuclear-powered and conventionally powered submarines, but not a more precise one.

[0044] Similarly, a method for detecting nuclear-powered underwater vehicles is disclosed, comprising the following steps: detecting radioactive radiation and outputting a corresponding radiation signal; determining a deviation from a previous radiation signal or a deviation from an expected radiation signal to detect the underwater vehicle.

[0045] Embodiments of concept 2c (2nd category, concept c) show a platform for detecting underwater vehicles with a temperature sensor and a signal processing unit. The temperature sensor is configured to detect a temperature with an accuracy of less than or equal to 0.1°C, preferably less than or equal to 0.5°C, more preferably less than or equal to 0.01°C. This means that the temperature sensor is highly sensitive to temperature changes. The signal processing unit is configured to continuously receive the temperature of the temperature sensor and determine a rate of change of the temperature in order to detect the underwater vehicle.

[0046] The idea behind concept 2c is to detect rapid temperature changes in the wake of the underwater vehicle, resulting from the mixing of water layers triggered by the underwater vehicle. This results in frequent, rapid temperature changes. This means a dynamic temperature change occurs. Furthermore, the underwater vehicle slightly heats the surrounding water. This results in a static temperature change. Both effects are detectable with continuous temperature measurement.

[0047] Embodiments show that the temperature sensor is designed to detect at least 90% of a temperature change of 0.1 °C within a maximum of 5 ms, preferably within a maximum of 2 ms, more preferably within 1 ms. This makes it possible to track the dynamic temperature change at the necessary speed.

[0048] In further embodiments, the signal processing unit is designed to perform a statistical analysis of the temperature measurements over time in order to determine a deviation of the temperature from a usual temperature.

[0049] Similarly, a method for detecting underwater vehicles is disclosed, comprising the following steps: - continuously detecting a temperature with an accuracy of less than 0.1 °C; - determining a rate of change of the temperature in order to detect the underwater vehicle.

[0050] Embodiments of concept 2d (2nd category, concept d) show a platform for detecting underwater vehicles with a sensor and a signal processing unit. The sensor is configured to determine a refractive index of the water surrounding the platform and output a corresponding electrical signal. The sensor comprises or is, for example, a refractometer. The signal processing unit is configured to detect a change in the refractive index of the water surrounding the platform based on the electrical signal of successive measurements in order to detect the wake of the underwater vehicle.

[0051] The idea behind concept 2d is to detect a change in the refractive index in the wake caused by the underwater vehicle. The refractive index changes, for example, due to a change in the temperature of the (sea) water. However, there are other factors that change the refractive index, such as changes in salinity or chemicals in the wake. The salinity can vary due to the mixing water layers. Chemicals can be released from the underwater vehicle into the water. Thus, determining the refractive index represents both an alternative to the temperature measurement of concept 2c and a useful addition to enable more robust detection of the underwater vehicle through mixing water layers.

[0052] Similarly, a method for detecting underwater vehicles is disclosed, comprising the following steps: -Continuously determining a refractive index of the water surrounding the platform and outputting a corresponding electrical signal; -Detecting, based on the electrical signal of successive measurements, a change in the refractive index of the water surrounding the platform in order to detect the underwater vehicle.

[0053] Embodiments of concept 2e (2nd category, concept e) show a platform for detecting underwater vehicles with a sensor and a signal processing unit. The sensor is configured to detect light and output a corresponding electrical signal. For example, the sensor is a photodiode or the sensor has the photodiode, or the sensor is or includes a, preferably electronic, light image sensor, e.g., a CCD sensor (charge-coupled device) or similar. The signal processing unit is configured to output a recommendation based on the electrical signal as to whether the electrical signal contains components of bioluminescence.Depending on the time of day (especially at night) and, in the case of an underwater platform, also the diving depth (the greater the diving depth, the less light penetrates to the platform), it may be sufficient to detect the mere appearance of light in order to infer bioluminescence.

[0054] The idea behind Concept 2e is to detect bioluminescence triggered by the underwater vehicle. The underwater vehicle triggers this when it travels through an area inhabited by special microorganisms such as algae, which are stimulated by pressure and begin to glow.

[0055] In embodiments, the sensor is configured to detect spectral components of the light. This is possible, for example, if the sensor has a spectrometer. The signal processing unit is configured to detect, based on the spectral components, whether spectral components of bioluminescence are present in order to output a recommendation as to whether the electrical signal contains components of bioluminescence. This is advantageous, for example, in a bright environment, such as during daylight or a full moon, in order to be able to reliably detect bioluminescence despite the bright environment. Advantageously, in addition to the spectrometer, the sensor has a light image sensor to be able to analyze both the spectrum and the actual light image.

[0056] In further embodiments, the sensor is configured to take sequential light images of the platform's surroundings to detect the light. The light images are preferably captured using an electronic sensor, e.g., a CCD sensor. Based on the sequence of light images, it is possible to detect the onset of bioluminescence. A comparison with other parameters, such as the time of day or the current position, makes it possible to rule out other causes for the onset of illumination.

[0057] Further embodiments show that the signal processing unit is configured to process data that assigns the presence of pressure-luminescent organisms to locations for various locations. For example, the signal processing unit has access to a nautical chart on which luminescent organisms are mapped. The signal processing unit can then determine the presence of pressure-luminescent organisms for the current location of the platform and take this information into account when issuing the recommendation as to whether the electrical signal contains components of bioluminescence. This means that if illumination is detected in an area where luminescent organisms are known to occur, the probability that this is bioluminescence is significantly higher than in an area where it is known that such organisms do not exist, or at least where it is not known that the luminescent organisms exist.

[0058] Similarly, a method for detecting underwater vehicles is disclosed, comprising the following steps: - detecting light and outputting a corresponding electrical signal; - outputting a recommendation as to whether the electrical signal contains bioluminescence in order to detect the underwater vehicle.

[0059] Category 3:

[0060] Embodiments of concept 3a (3rd category, concept a) show a platform for detecting turbulence caused by the wake of underwater vehicles. The platform comprises a laser Doppler anemometer and a signal processing unit. The laser Doppler anemometer is designed to measure a flow characteristic in the water surrounding the platform and output a corresponding electrical signal. The laser Doppler technology is based on determining the Doppler shift of the scattered light of a moving object illuminated with laser light. A flow characteristic can be understood, for example, as whether the water is flowing calmly or turbulently, how fast the water is flowing, or in which direction the water is flowing. The signal processing unit is designed to receive the electrical signal and analyze the measured flow characteristic in order to detect the underwater vehicle.

[0061] Advantageously, the platform comprises a plurality of laser Doppler anemometers. Laser measurements allow for a point-by-point determination of the velocity and, optionally, direction of the surrounding water. Using multiple laser Doppler anemometers, multiple points within a volume can be examined for their flow velocity and, optionally, direction. This makes it possible, for example, to determine whether the flow is turbulent or linear.

[0062] The idea behind concept 3a is to detect turbulence in the water that indicates the wake of an underwater vehicle. Various techniques are available for this. One of these is laser Doppler anemometry. This is based on the Doppler shift of scattered light generated by particles in the water from one or more laser beams. In exemplary embodiments, the laser Doppler anemometer is designed to measure the flow properties in a backscatter arrangement. This means that the detector for receiving the scattered light is arranged on the same side of the measurement volume as the associated laser (or the associated lasers in a two-beam measurement system). With the backscatter arrangement, it is possible to construct the transmitting optics in such a way that they simultaneously accommodate the receiving optics, thus eliminating the need for complex adjustment between the transmitting and receiving units.However, the intensity of the scattered signal in this arrangement is an order of magnitude lower than in the forward scattering arrangement. Nevertheless, backward scattering is preferred, especially for moving platforms, especially underwater vehicles. This makes it possible to operate the laser at the bow facing forward. Since the measurement volume is then located in front of the moving platform, the measurement will experience little or no influence of the flow properties due to the moving platform.

[0063] Similarly, a method for detecting turbulence caused by the wake of underwater vehicles is disclosed, comprising the following steps: -Measuring a flow characteristic in the water surrounding the platform using a laser Doppler anemometer and outputting a corresponding electrical signal; -Analyzing the measured flow characteristic to detect the underwater vehicle.

[0064] Embodiments of concept 3b (3rd category, concept b) show a platform for detecting turbulence caused by the wake of underwater vehicles. The platform comprises a distance current meter and a signal processing unit. The current meter is configured to measure a flow characteristic in the water surrounding the platform and output a corresponding electrical signal. The signal processing unit is configured to receive the electrical signal and analyze the measured flow characteristic to detect the underwater vehicle.

[0065] The idea behind concept 3b is to detect turbulence in the water that indicates the wake of an underwater vehicle. In exemplary embodiments, the distance current meter comprises an ultrasonic Doppler profile current meter (Acoustic Doppler Current Profiler - ADCP). Using reflected, transmitted sound pulses, the distance of scattered particles in the water can be detected via the propagation time and the speed via the Doppler shift. Typically, high-frequency sound pulses are used for this purpose, in particular frequencies typically greater than 500 kHz, preferably greater than 1 MHz. Such frequencies cannot be detected by typical passive sonars, so the risk of detection by the transmitted sound is low. Furthermore, such high frequencies are also strongly attenuated in the water, so that the range is very short, limited to a maximum of a few hundred meters.

[0066] Similarly, a method for detecting turbulence caused by the wake of underwater vehicles is disclosed, comprising the following steps: - measuring a flow characteristic in the water surrounding the platform using a distance flow meter and outputting a corresponding electrical signal; - analyzing the measured flow characteristic to detect the underwater vehicle.

[0067] Embodiments of concept 3c (3rd category, concept c) show a platform for detecting turbulence caused by the wake of underwater vehicles. The platform comprises a thermal anemometer and a signal processing unit. The thermal anemometer is designed to measure a flow characteristic, in particular a flow direction and / or a flow velocity, in the water surrounding the platform and to output a corresponding electrical signal. The thermal anemometer uses the cooling experienced by the surface of a warm body in a colder flowing medium as a measuring effect. Preferably, the warm body is heated electrically so that a measurable change in the body's resistance occurs directly via the change in temperature of the body. The signal processing unit receives the electrical signal and analyzes the measured flow velocity in order to detect the underwater vehicle.The idea behind Concept 3c is to be able to detect turbulence in the water, which indicates the wake of an underwater vehicle, even without eddies or particles in the water. This can be reliably achieved using a thermal anemometer.

[0068] Embodiments show that the thermal anemometer has a hot film or a hot wire (or a combination of both). The hot wire anemometer comprises at least two hot wires arranged perpendicular to each other. This makes it possible to determine a two-dimensional flow direction. However, four hot films as well as three or four hot wires per thermal anemometer are preferably used. With three hot wires arranged perpendicular to each other, a three-dimensional flow direction can be determined, and a fourth wire can also be used to determine a backflow. Likewise, four hot film anemometers can be arranged on four sides of a body, for example a pipe, in order to be able to determine a three-dimensional flow direction including backflow. The hot film anemometer is advantageous when used on mobile platforms (e.g.

[0069] underwater vehicles) or platforms that are located directly in a water current, as it is robust and can withstand water resistance well.

[0070] In embodiments, the platform has a temperature sensor configured to determine a current temperature of the water surrounding the platform. The thermal anemometer is configured to adjust a current flow through a sensor element (e.g., a hot wire or hot film) such that a measurement temperature of the thermal anemometer has a constant temperature compared to the temperature of the water surrounding the platform, regardless of the flow properties of the water. This method is also referred to as constant-temperature anemometry. If a reference sensor is required to determine the temperature of the water, sensors already installed on the platform, for example, an underwater vehicle such as a submarine, or the temperature sensor according to concept 2c can be used.Alternatively, the thermal anemometer is designed to ensure a constant current flow through the sensor element, so that the flow properties of the water are measured via the temperature change. This method is also known as constant-current anemometry.

[0071] Similarly, a method for detecting turbulence caused by the wake of underwater vehicles is disclosed, comprising the following steps: -Measuring a flow characteristic in the water surrounding the platform using a thermal anemometer and outputting a corresponding electrical signal; -Analyzing the measured flow characteristic to detect the underwater vehicle.

[0072] Embodiments of concept 3d (3rd category, concept d) show a platform for detecting turbulence caused by the wake of underwater vehicles, comprising a sensor and a signal processing unit. The sensor is configured to detect a magnetic field surrounding the sensor and output a corresponding electrical signal. The signal processing unit is configured to receive the electrical signal and, based on successive measurements, to determine magnetic field changes caused by turbulence in the wake of accelerated ions as a superposition of the Earth's static magnetic field. This makes it possible to determine the entry into the wake of an underwater vehicle. The sensor is preferably configured to determine the magnetic field of the accelerated ions in at least two, in particular three, spatial directions.Here, the typical rotating magnetic field of the turbulence present in the wake of the underwater vehicle can also be determined.

[0073] The idea of ​​concept 3d is to detect the ions naturally present in seawater due to the salt content in the wake of the underwater vehicle. Due to their charge, the ions generate a magnetic field as they move. However, this field is superimposed in magnitude by the Earth's magnetic field, which makes measurement more difficult. For this reason, the signal processing unit analyzes a temporal progression of the magnetic field in order to detect a change in the magnetic field. In the wake of the underwater vehicle, a change in the magnetic field can then only be measured with a multi-dimensional magnetic field sensor. The magnetic field sensor is therefore preferably part of an array of (preferably similar) magnetic field sensors. In the case of a mobile platform, e.g. an underwater vehicle, the magnetic field sensor or the array of magnetic field sensors is preferably arranged in front of the underwater vehicle. Furthermore, the magnetic field sensor has a detection threshold of preferably less than.

[0074] The magnetic anomaly detector according to Concept 1b, for example, is suitable as an optional magnetic field sensor array, provided it has sufficient measurement speed to detect the water vortices. However, with the magnetic field sensor array according to Concept 1b, it should be noted that it is advantageously towed, and thus the towing underwater vehicle also generates water vortices.

[0075] Similarly, a method for detecting turbulence caused by the wake of underwater vehicles is disclosed, comprising the following steps: - detecting a magnetic field and outputting a corresponding electrical signal; - determining, based on successive measurements, magnetic field changes caused by turbulence in the wake of accelerated ions as a superposition of the Earth's static magnetic field.

[0076] Embodiments of concept 3e (3rd category, concept e) show a platform for detecting turbulence caused by the wake of underwater vehicles, comprising a bend sensor and a signal processing unit. The bend sensor is configured to detect turbulence in the water surrounding the bend sensor and output a corresponding electrical signal. The signal processing unit is configured to receive the electrical signal and, based on the electrical signal from successive measurements, to detect the turbulence caused by the wake of the underwater vehicle. Turbulence caused by the wake of the underwater vehicle is characterized, for example, by the fact that it forms a trail and can thus be detected via a plurality of measurements.Furthermore, if the turbulence can no longer be detected on a moving platform, it is possible to find the turbulence, ie the track, again by measurements in the immediate vicinity of the last measuring location.

[0077] The idea of ​​concept 3e is to be able to detect water currents using a highly sensitive bending sensor, similar to the whiskers of seals.

[0078] In exemplary embodiments, the bending sensor has a curvature, in particular a winding, preferably a plurality of windings. For example, the bending sensor is helically shaped. It is possible for the sensor element to have this shape; alternatively, it is also possible for the bending sensor to comprise a support form to which the sensor element is applied. This shape is advantageous for achieving low inherent rigidity and thus enabling high sensitivity of the bending sensor.

[0079] In further embodiments, the bending sensor comprises a piezo element. The piezo element can be applied to the support mold of the bending sensor. Application is possible, for example, in the form of a coating or a film. Alternatively, the piezo element can be rod-shaped. This allows the bending sensor to operate without a support mold. In a further alternative, the support mold can be mounted on the piezo element. Depending on the set sensitivity of the support mold, the pressure exerted by the support mold on the piezo element varies at a constant water velocity.

[0080] In addition to or as an alternative to the piezo element, the bending sensor can comprise a strain gauge. The strain gauge can be applied to the support shape of the bending sensor. The bending sensor preferably has a plurality of strain gauges. This allows compression and extension of the support shape in different directions to be detected as best as possible. The same principle can also be applied with piezo elements applied to the support shape. Further embodiments show the bending sensor, in particular the support shape of the bending sensor, with a length that is at least 20 times, preferably at least 50 times, particularly preferably at least 100 times as large as a thickness (i.e., a diameter with a round cross-section) of the bending sensor. Such a configuration also enables high sensitivity of the bending sensor.

[0081] In further embodiments, the bending sensor is one of a plurality of bending sensors, wherein the bending sensor and a further bending sensor of the plurality of bending sensors have a maximum sensitivity at different swirl frequencies. The sensitivity of the bending sensors can be achieved, for example, via a material of the bending sensor, in particular a material of the carrier shape, different lengths of the bending sensor, in particular of the carrier shape, or different winding steepnesses of the bending sensor, in particular of the carrier shape.

[0082] Similarly, a method for detecting turbulences in the wake of underwater vehicles is disclosed, comprising the following steps: - detecting turbulences with a bending sensor and outputting a corresponding electrical signal; - detecting turbulences in the wake of the underwater vehicle based on the electrical signal of successive measurements.

[0083] Across all concepts, a platform is understood as a mobile or (quasi) stationary, i.e. essentially stationary, platform. A platform is essentially stationary, for example, if it is connected to the waterbed, e.g. the seabed, by a cable. This limits its radius of movement to a predetermined extent. For example, a buoy, in particular an underwater buoy, can be used as an essentially stationary platform. A mobile platform can have its own propulsion or be externally propelled, e.g., towed. An externally propelled platform can be, for example, a towed antenna or another towed body. A self-propelled platform is, for example, a manned or unmanned (e.g., autonomous) underwater vehicle. Unmanned underwater vehicles also include underwater torpedoes.The advantage of a powered platform is that it does not require its own power supply, but can be powered by a towing device, such as an electrical cable. For example, an unmanned surface vehicle can pull a towed body underwater and optionally supply it with power.

[0084] In a given application, a platform can be used with one or any combination of the concepts described above. This means, for example, that the platform is equipped with different sensors that can detect the underwater vehicle according to the concepts described above. The use of multiple concepts reduces the probability of misdetection, i.e., a false negative or false positive detection result.

[0085] Furthermore, it is possible to use multiple platforms, whether different or similar, that can communicate with each other or with a base station. For this purpose, the platforms can have a communication unit.

[0086] Using the communication unit, the platforms can at least send data packets and optionally also receive them.

[0087] Preferably, the sensors record measurements continuously. This makes it possible, for example, with Category 2 and 3 concepts to follow the wake, i.e., in particular, to detect when a sensor is located in or outside the wake. Category 1 concepts also allow tracking the path of the underwater vehicle to be detected.

[0088] Particularly with sensors in categories 2 and 3, it is advantageous to use a plurality of similar sensors (i.e. several sensors per concept) per platform. This makes it possible to determine a gradient of the substances or physical properties to be detected (category 2) or of the turbulence (category 3). The direction of the gradient indicates the direction in which the measured physical effect weakens and the direction in which it becomes stronger. This means that the gradient can be used in particular to determine the direction in which the wake is left. For example, at least 3 or 5 sensors are used for this purpose, e.g. straight (3) or arranged in a cross (5). Any other sensor arrays can of course also be used which make it possible to detect a gradient in one, preferably two, spatial directions. The signal processing unit can determine the gradient.

[0089] To detect the underwater vehicle, the signal processing unit can use a sensor result or any combination of the sensor results from the concepts described above. The signal processing unit can perform the detection using a computer-implemented classification. Well-known classifiers include the Bayes classifier or neural networks. Training data and evaluation data are required to train the classifier. This can be obtained, for example, by equipping one or, preferably, a plurality of platforms with one or more of the sensors from the concepts described and knowingly recording data both outside and knowingly inside the wake of various underwater vehicles. This is of course easier in peacetime, since the actual position of underwater vehicles can be detected, for example, using active sonar.Furthermore, it is possible, at least for the boats of friendly navies, to drive the platform behind an underwater vehicle during test runs or to have it drive along stationary platforms.

[0090] Detection means that the platform determines that an underwater vehicle is nearby. Locating means that the platform determines at least a direction, preferably a position, i.e. direction and distance, of the underwater vehicle. Classifying means that the platform recognizes which underwater vehicle it is. Classification can, for example, include determining one or any combination of the following information: a friend-foe distinction, an origin (nationality), a type of underwater vehicle. Detection of the underwater vehicle is possible using the measurement results of one or more of the sensors in the concepts described. Locating the underwater vehicle in Category 2 and Category 3 concepts is possible, for example, by tracking its wake.A classification can be made based on the concepts of Category 3 by examining the structure of the turbulence in the wake. For example, the spatial extent of the turbulence, e.g., the diameter of the wake, as well as speed or average rotation direction can enable classification.

[0091] Concept-based embodiments that can be used with one or any combination of the concepts described above show an underwater vehicle, in particular a submarine, for detecting another underwater vehicle, comprising a measuring head and a deployment device. The measuring head has a sensor. The sensor is designed to detect a feature of the underwater vehicle underwater. The measuring head is further designed to be extended from the deployment device such that the sensor is located in front of the underwater vehicle. A pipe, for example, is suitable as a deployment device. The pipe can have guide means, for example guide grooves, on its walls.

[0092] The idea behind these overarching embodiments is to provide one or more sensors for an underwater vehicle that are 1. not exposed to contamination, e.g., by algae or mussels, when not in use, and 2. not affected by turbulence from the moving underwater vehicle. The first advantage is achieved by the measuring head being extendable from the deployment device. The second advantage is achieved by the measuring head being positioned in front of the underwater vehicle, in the main direction of travel, for a measurement or a series of measurements.

[0093] The deployment device can be designed to deploy unmanned underwater vehicles, in particular underwater moving bodies, from the underwater vehicle. For example, the deployment device can be a torpedo tube. This is advantageous because torpedo tubes are also present on existing underwater vehicles and can therefore also be used for deploying the measuring head, at least if they are located near the bow. Retrofitting to existing manned underwater vehicles is thus possible.

[0094] The measuring head may further comprise a fixing means that extends into a tube of the deployment device and is connected to the underwater vehicle to fix the measuring head to the underwater vehicle. One example of how the fixing means can be designed is a telescopic rod.

[0095] Alternatively, the measuring head can be part of an unmanned underwater vehicle, in particular a remotely operated underwater vehicle. The unmanned underwater vehicle is designed to move ahead of the underwater vehicle. The remotely operated underwater vehicle (ROV) can be controlled manually, automatically, or semi-automatically from the deploying underwater vehicle. In the case of automatic or semi-automatic control, this can be set so that the remotely operated underwater vehicle follows the directional changes of the deploying underwater vehicle, so that the remotely operated underwater vehicle moves ahead of the deploying underwater vehicle. The unmanned underwater vehicle can be connected to the deploying underwater vehicle by means of a communication cable in order to transmit the measurement results from the sensor(s) of the measuring head.The control cable for the remotely operated underwater vehicle can be integrated into the communication cable.

[0096] The unmanned underwater vehicle is preferably connected to the underwater vehicle by means of a traction means. The communication cable and / or the control cable can be integrated into the traction means. The underwater vehicle has a retrieval device which is designed to retrieve the unmanned underwater vehicle to the deployment device by means of the traction means. The retrieval device can retrieve the traction means, e.g. roll it up, and thus retrieve the unmanned underwater vehicle to the deployment device. If the deployment device is designed as a pipe, the retrieval device can preferably retrieve the unmanned underwater vehicle back into the pipe. For this purpose, the pipe can be supplemented with an energy-absorbing funnel so that the unmanned underwater vehicle can be retrieved into the pipe without damaging the underwater vehicle or the unmanned underwater vehicle.

[0097] Analogously, a method for detecting another underwater vehicle with an underwater vehicle is disclosed, comprising the following steps: -Extending a measuring head from a deployment device of the underwater vehicle such that a sensor of the measuring head is located in front of the underwater vehicle, wherein the sensor is designed to detect a feature of the underwater vehicle under water.

[0098] Preferred embodiments of the present invention are explained below with reference to the accompanying drawings. They show:

[0099] Fig. 1 : a schematic diagram of a platform for detecting an underwater vehicle in a block diagram;

[0100] Fig. 2: a schematic perspective view of a bending sensor according to concept 3e; and

[0101] Fig. 3: a schematic side view of an underwater vehicle with a deployment device for deploying a measuring head, which can be equipped, for example, with one or any combination of the sensors according to one of the described concepts.

[0102] 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 are provided with the same reference numerals in the different figures, so that the description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another. Fig. 1 shows a schematic block diagram of a platform 20, in particular a manned or unmanned underwater vehicle, for detecting an underwater vehicle 22. The platform comprises a sensor 24 according to one of the concepts described above, as well as a signal processing unit 26 according to one of the concepts described above. Sensor data orMeasured values ​​can be transmitted from the sensor to the signal processing unit 26 in the form of an electrical signal via an electrical connection 27. Conversely, a controlled preamplifier, for example, can already be integrated into the sensor, which can transmit, for example, an amplification factor or the like via the electrical connection.

[0103] Fig. 2 shows a schematic perspective view of the sensor 24 in a configuration as a bending sensor according to concept 3e. A support mold 28 is supported on a (sensor) layer 30 comprising a material that converts pressure into an electrical output voltage. The material is, in particular, a piezoelectric material, for example, lead zirconate titanate (PZT). The electrical output voltage can be tapped at the electrodes 32a, 32b.

[0104] As shown in Fig. 2, it is optionally possible to manufacture the bending sensor 24 as an integrated component. For this purpose, the layer 30 can be applied to a semiconductor substrate 34. An optional cavity 36 can then be introduced, in particular etched, into the semiconductor substrate 34. The cavity then allows not only a vibration of the support mold 28 to be detected, but also a 3-dimensional movement, thus also an upward and downward movement in the illustration in Fig. 2.

[0105] Furthermore, an electrical circuit 34a can be formed directly in the semiconductor substrate 34. This can, for example, be the signal processing unit or include data preprocessing. One or more further layers can be applied to the substrate, in particular between the substrate 34 and the layer 30.

[0106] Fig. 3 shows a schematic side view of an underwater vehicle 20 as a platform. The underwater vehicle 20 includes a deployment device 38. Using the deployment device 38, a measuring head 40 can be extended from the underwater vehicle such that it is located in front of the underwater vehicle. The measuring head has a sensor for detecting environmental information of the underwater vehicle. In particular, the sensor is a sensor of the previously described concepts.

[0107] 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.

[0108] 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.

[0109] List of reference symbols:

[0110] 20 Platform

[0111] 22 underwater vehicle to be detected 24 sensor

[0112] 26 Signal processing unit

[0113] 27 electrical signal (sensor signal)

[0114] 28 Carrier shape

[0115] 30 sensory layer 32 electrodes

[0116] 34 Substrat

[0117] 36 cavity

[0118] 38 Dispensing device

[0119] 40 measuring head

Claims

Patent claims 1 . Platform (20) for detecting turbulence caused by the wake of underwater vehicles (22), comprising: a sensor (24) configured to detect a magnetic field surrounding the sensor and output a corresponding electrical signal (27); a signal processing unit (26) configured to receive the electrical signal (27) and, based on successive measurements, to determine magnetic field changes caused by turbulence in the wake of accelerated ions as a superposition of the static earth's magnetic field.

2. Platform according to one of the preceding claims, wherein the sensor (24) is designed to determine the magnetic field in at least two, in particular three spatial directions.

3. Platform according to one of the preceding claims, wherein the sensor (24) has a detection threshold of preferably less than.

4. Platform (20) according to one of the preceding claims, wherein the platform comprises a sensor (24) which is designed to chemically analyze seawater and to output a proportion of at least one predefined substance in a corresponding analysis result (27); wherein the signal processing unit (26) is configured to determine, based on the analysis result, a deviation from a previous analysis result or a deviation from an expected analysis result in order to detect the underwater vehicle. Platform (20) according to one of the preceding claims, wherein the platform for detecting nuclear-powered underwater vehicles (22) has a sensor (24) configured to detect radioactive radiation and output a corresponding radiation signal (27); wherein the signal processing unit (26) is configured to receive the radiation signal (27) and determine a deviation from a previous radiation signal or a deviation from an expected radiation signal in order to detect the underwater vehicle.Platform (20) according to one of the preceding claims, wherein the platform comprises a temperature sensor (24) configured to detect a temperature with an accuracy of less than 0.1°C, wherein the signal processing unit (26) is configured to continuously receive the temperature (27) of the temperature sensor (24) and to determine a rate of change of the temperature in order to detect the underwater vehicle (22). Platform (20) according to one of the preceding claims. wherein the platform comprises a sensor (24) configured to determine a refractive index of the water surrounding the platform (20) and to output a corresponding electrical signal (27), wherein the signal processing unit (26) is configured to detect a change in the refractive index of the water surrounding the platform based on the electrical signal (27) of successive measurements in order to detect the underwater vehicle (22). Platform (20) according to one of the preceding claims, wherein the platform comprises a sensor (24) configured to detect light and to output a corresponding electrical signal (27); wherein the signal processing unit (26) is configured to output a recommendation based on the electrical signal (27) as to whether the electrical signal (27) contains components of bioluminescence in order to detect the underwater vehicle (22).Platform (20) according to one of the preceding claims, wherein the platform has a further sensor for detecting turbulence caused by the wake of the underwater vehicle, which is designed to detect the turbulence. Platform (20) according to one of the preceding claims, wherein the platform comprises an underwater antenna (24) having a plurality of waterborne sound transducers, wherein the waterborne sound transducers of the plurality of waterborne sound transducers are designed to convert waterborne sound into an electrical signal (27) corresponding to the sound pressure. wherein the signal processing unit (26) is configured to receive the electrical signals from the underwater sound transducers and to detect infrasound emitted by the underwater vehicle (22) in the underwater sound. Platform (20) according to one of the preceding claims, wherein the platform comprises a magnetic anomaly detector (MAD) (24) configured to detect the Earth's magnetic field and output a corresponding MAD sensor signal (27); wherein the signal processing unit (26) is configured to receive the MAD sensor signal and to detect a deviation of the Earth's magnetic field by the underwater vehicle (22).Platform (20) according to one of the preceding claims, wherein the platform is an underwater vehicle; wherein the underwater vehicle has a measuring head (40) in which the sensor (24) is arranged or the sensors (24) are arranged; wherein the underwater vehicle has a deployment device (38); wherein the measuring head (40) is designed to be extended from the deployment device such that the sensor (24) is located in front of the underwater vehicle (20). Method for detecting turbulence caused by the wake of underwater vehicles, comprising the following steps: Detecting a magnetic field and outputting a corresponding electrical signal; determining, based on successive measurements, magnetic field changes caused by eddies in the wake of accelerated ions as a superposition of the static Earth's magnetic field.

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