Radio receiver for determining a position of a sonar buoy

Abstract

Disclosed is a radio receiver (20) for determining a position of a sonar buoy (22), comprising a receiver unit (24) and a data processing unit (26). The receiver unit (24) is configured to non-intermittently, in particular continuously, receive a series of radio signals (28) from the sonar buoy (22) from the time the sonar buoy (22) is deployed. The data processing unit (26) is configured to determine a reception level of the radio signals (28) of the series of radio signals and to determine the position of the sonar buoy (22) absolutely or relative to the radio receiver (20) on the basis of a plurality of reception levels of different radio signals (28) of the series of radio signals.

Description

[0001] Radio receiver for determining the position of a sonar buoy

[0002] Description

[0003] The invention relates to the determination of the position of a sonar buoy that is not fixed in place, in particular a self-deployed one.

[0004] Sonar buoys are deployed temporarily, for a few days, or often just a few hours, in a body of water, especially the sea. After this time, the sonar buoys can no longer be used. They are either abandoned or destroyed. For this reason, sonar buoys are manufactured as cheaply as possible, and often, elaborate anchoring to the seabed is omitted. Without anchoring, however, the buoys are exposed to the elements. After deployment, the sonar buoys drift, particularly due to currents and wind, and leave their original deployment position.

[0005] For this reason, sonar buoys are usually equipped with GPS (Global Positioning System) sensors. However, the GPS system can fail or be disrupted in times of crisis, or the GPS sensors themselves, especially the cheaper ones, can malfunction. Without a current position of the sonar buoy, the position of a detected target, which can only be determined relative to the buoy, can no longer be reliably ascertained. This effect increases over time due to the natural drift of the sonar buoy.

[0006] The object of the present invention is therefore to create an improved concept for determining the position of sonar buoys.

[0007] 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.

[0008] Exemplary embodiments show a radio receiver for determining the position of a sonar buoy. The radio receiver comprises a receiving unit and a data processing unit. The receiving unit is designed to continuously receive a sequence of radio signals from the sonar buoy from the moment of its deployment. That is, the buoy is activated on board a deployment platform or immediately after being deployed into the water. After deployment, the sonar buoy receives underwater sound using multiple underwater transducers arranged within the buoy. The resulting underwater sound signals are transmitted by the sonar buoy via a sequence of radio signals and can thus be received by the receiving unit. The sequence of radio signals can constitute a continuous radio transmission. The radio receiver is optionally located on the deployment platform.The deployment platform can be a watercraft, such as a manned or unmanned ship, or an aircraft, such as a helicopter, airplane or (flying) drone.

[0009] The underwater sound signals transmitted via radio can be analyzed from the platform on which the radio receiver is located. For example, the direction from which sound components of the underwater sound reach the underwater sonar transducers can be determined. The direction can be determined, for example, using beamforming, or simply based on gradient calculations (i.e., direction calculations based on dipoles, cf. DIFAR buoy). Furthermore, the position of a sound source can be directly determined by measuring the time differences of the underwater sound to different sonar buoys. As a third option, the transmitter's position can also be determined without beamforming, based on the time differences of the sound components of at least three sonar buoys arranged in an area (Time Delay of Arrival, TDoA).

[0010] The data processing unit determines the received level of the radio signals within a sequence of signals and, based on a plurality of received levels of different radio signals within that sequence, determines the position of the sonar buoy, either absolutely or relative to the radio receiver. That is, the received level of the radio signals from the sonar buoy is continuously determined. Physically, it is now possible to deduce the distance of the sonar buoy from a single received level and its position from a multitude of received levels. Typically, the position of the sonar buoy relative to the radio receiver is first determined from its distance and the direction of the incoming radio signals. If knowledge of the absolute position is necessary, the relative position of the sonar buoy can be converted into an absolute position if the absolute position of the radio receiver is known.This is usually known with sufficient accuracy, even in the event of a GPS system failure.

[0011] The idea is therefore to use the radio signals of the sonar buoys to determine the changing position of the sonar buoy due to its drift, and thus to improve the location of underwater sound transmitters.

[0012] In exemplary implementations, the data processing unit can estimate parameters for a model after the deployment of the sonar buoy. The model takes the received signal strength as an input parameter and the distance between the sonar buoy and the radio receiver as an output parameter. Knowing the position of the radio receiver and the sonar buoy, or at least their relative positions, is advantageous. For example, the following formula can be used to approximate the distance (D in meters) between the sonar buoy and the radio receiver based on the received signal strength (E in decibels):

[0013] The unknown parameters X and S can be estimated so that the distance (£) between the radio receiver and the sonar buoy can be determined. X can be described as the attenuation factor. S can be described as the transmit level.

[0014] This means that either this or an alternative linear model can be used to determine the distance between the sonar buoy and the radio receiver. A linear model has low complexity and therefore requires little computing power.

[0015] The parameters (e.g., X and 5) can be determined more robustly using linear regression with a large number of (e.g., consecutive) measurements of the signal strength. When using linear regression, measurement inaccuracies of individual measurements have less of an impact. Distance determination can also be made more robust, for example, by averaging the signal strength or the resulting distance. A moving average is a suitable method for continuously determining the distance.

[0016] In exemplary embodiments, the data processing unit can also use a Kalman filter, in particular a non-linear Kalman filter, to determine the position of the sonar buoy based on the distance of the sonar buoy to the radio receiver.

[0017] In further embodiments, the data processing unit can use a calibration model to account for known environmental influences on the received signal level when determining the position of the sonar buoy. The calibration model can represent additional influences on the received signal level that are not considered by the linear model, thus improving the determination of the distance between the sonar buoy and the radio receiver. The calibration model can be predefined for a combination of a platform and a radio receiver mounted at a predetermined location. In addition to verifying, or alternatively to creating, the model, the platform can also first perform a calibration run to be able to receive radio signals from the sonar buoy from all directions.

[0018] For example, the data processing unit, using the calibration model, can take into account direction-dependent shadowing caused by a support platform on which the radio receiver is mounted as an environmental influence when determining the position of the sonar buoy. For instance, the placement of the radio receiver on a platform can lead to direction-dependent shadowing, i.e., attenuation of the radio signal depending on the direction of reception. If the radio receiver is mounted on a ship, the bridge or other structures such as containers, antennas, etc., can cause shadowing of the radio receiver from certain reception directions. This attenuation can be taken into account when measuring the received signal level, for example, by an additive or multiplicative gain factor.Similarly, the calibration model can be used to account for the current altitude of a flying platform on which the radio receiver is mounted as an environmental influence when determining the position of the sonar buoy. The altitude also affects the signal strength. It influences the line of sight, which in turn affects reception. For example, attenuation is lower below a cloud layer than above it. Furthermore, attenuation is not linear with the altitude of the platform due to variations in air pressure.

[0019] Furthermore, a system comprising a previously described radio receiver mounted on a carrier platform and a sonar buoy is disclosed. The radio receiver can determine the position of the sonar buoy. The system can also include another radio receiver mounted on a further carrier platform. The data processing unit of the radio receiver and the data processing unit of the second radio receiver can exchange position information to determine an improved position of the sonar buoy. That is, data fusion between the two data processing units can be performed, so that the position of the sonar buoy can be determined, for example, depending on its distance from both radio receivers. Furthermore, the system can include a plurality of sonar buoys, with the radio receiver and / or the two radio receivers determining the position of the sonar buoys in the plurality of sonar buoys.

[0020] Analogously, a method for determining the position of a sonar buoy is disclosed comprising the following steps: a) receiving radio data from the sonar buoy continuously from the time of deployment of the sonar buoy; b) determining a received level of the radio data; c) determining the position of the sonar buoy absolutely or relative to a radio receiver based on a plurality of received levels of different radio data.

[0021] Likewise, a computer program is disclosed, comprising instructions that, when executed by a computer, cause it to perform steps b) and c) of the method based on the sequence of radio signals received in step a). Any further steps of the method can also be executed by means of the computer program.

[0022] Preferred embodiments of the present invention are explained below with reference to the accompanying drawing. It shows:

[0023] Fig. 1 : a schematic block representation of a radio receiver for determining the position of a sonar buoy on a carrier platform and the sonar buoy floating in the water.

[0024] Before exemplary embodiments of the present invention are explained in detail below with reference to the drawings, it should be noted that identical, functionally equivalent or equivalent elements, objects and / or structures in the different figures are provided with the same reference numerals, so that the description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another.

[0025] Fig. 1 shows a radio receiver 20 for determining the position of a sonar buoy 22. The radio receiver 20 comprises a receiving unit 24, shown here as an antenna, and a data processing unit 26. The receiving unit 24 can continuously receive a sequence of radio signals 28 from the sonar buoy 22. The radio receiver 20 is shown by way of example on a platform 30, shown here as a ship. The sonar buoy 22 can also be deployed from the platform 30. After deployment, the sonar buoy 22 receives underwater sound 32 with a plurality of underwater sound transducers 34 arranged in the sonar buoy. The resulting underwater sound signals 36 are transmitted by an antenna 38 of the sonar buoy 22 by means of a sequence of radio signals 28 and can thus be received by the receiving unit 24 and forwarded to the data processing unit 26.

[0026] The data processing unit 26 determines a reception level of the radio signals 28 of the sequence of radio signals and determines, based on a plurality of reception levels of different radio signals 28 of the sequence of radio signals, the position of the sonar buoy 22 absolutely or relative to the radio receiver 24 or relative to the platform 30.

[0027] The disclosed (underwater) sound transducers are designed for use underwater, 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 (received) underwater sound signal. Furthermore, it is possible for the transducers to convert an applied electrical voltage into underwater sound. The electrical voltage can follow a predefined pattern and then be referred to as the (transmitted) sonar signal, while the underwater sound resulting from the sonar signal to be transmitted is referred to as the (transmitted) sonar signal. Examples of sonar signals are a chirp (frequency-modulated signal) or, as a special case of the chirp, a sweep (linearly frequency-modulated signal). The transducers can therefore be used as underwater sound receivers and / or underwater sound transmitters.The transducers can be made of a piezoelectric material, such as a piezoceramic, to serve as the sensor material. A plurality of underwater transducers, or one or more underwater transducers in conjunction with a signal processing unit, can be referred to as a sonar system. 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. Likewise, the transducers are preferably not used for, or are not suitable for, the ultrasonic testing of materials.

[0028] Although some aspects have been described in connection with a device, it is understood that these aspects also constitute a description of the corresponding method, such that a block or component of a device is also to be understood as a corresponding method step or as a feature of a method step. Analogously, aspects described in connection with or as a method step also constitute a description of a corresponding block, detail, or feature of a corresponding device. Depending on the implementation requirements, embodiments of the invention can be implemented in hardware or in software. The implementation can be carried out using a digital storage medium, for example, a magnetic or optical storage medium, on which electronically readable control signals, e.g.,A computer program is stored that can interact with a programmable computer system (CPU and / or GPU) in such a way that the respective procedure is carried out. For this reason, the digital storage medium should be computer-readable. Exemplary embodiments may therefore include a data carrier that has electronically readable control signals capable of interacting with a programmable computer system in such a way that one of the procedures described herein is carried out.

[0029] In some embodiments, a programmable logic device (for example, a field-programmable gate array, an FPGA) can be used to perform some or all of the functionalities of the methods described herein. In some embodiments, a field-programmable gate array can interact with a microprocessor to perform one of the methods described herein. Generally, in some embodiments, the methods are performed by any hardware device. This can be general-purpose hardware such as a computer processor (CPU) or a graphics processing unit (GPU), or hardware specific to the method, such as an ASIC. Distributed execution across the CPU and GPU is also possible.

[0030] 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. List of reference numerals:

[0031] 20 radio receivers

[0032] 22 Sonar buoy 24 Receiving unit

[0033] 26 Data processing unit

[0034] 28 Radio signal

[0035] 30 platform

[0036] 32 Water sound 34 Water sound transducer

[0037] 36 Underwater sound signal

[0038] 38 Antenna of the sonar buoy

Claims

Patent claims 1. Radio receiver (20) for determining the position of a sonar buoy (22) with the following features: - a receiving unit (24) which is designed to continuously, in particular continuously, from the time of deployment of the sonar buoy (22), receive a sequence of radio signals (28) from the sonar buoy (22); - a data processing unit (26) which is configured to determine a received level of the radio signals (28) of the sequence of radio signals and, based on a plurality of received levels of different radio signals (28) of the sequence of radio signals, to determine the position of the sonar buoy (22) absolutely or relative to the radio receiver (20).

2. Radio receiver (20) according to claim 1, wherein the data processing unit (26) is configured to estimate parameters for a model after the deployment of the sonar buoy (22), wherein the model has as input parameters the received level and as output parameters a distance of the sonar buoy (22) to the radio receiver (20), and wherein there is knowledge of the position of the radio receiver (20) and the position of the sonar buoy (22), or at least their relative position to each other.

3. Radio receiver (20) according to one of the preceding claims, wherein the data processing unit (26) is configured to use a linear model as a model for determining the distance of the sonar buoy (22) to the radio receiver (26).

4. Radio receiver (20) according to one of claims 2 or 3, wherein the data processing unit (26) is configured to use a Kalman filter to determine the position of the sonar buoy (22) based on the distance of the sonar buoy (22) to the radio receiver (20).

5. Radio receiver (20) according to one of the preceding claims, wherein the data processing unit (26) is configured to generate a calibration model. use to take into account known environmental influences on the received level when determining the position of the sonar buoy (22).

6. Radio receiver (20) according to claim 5, wherein the data processing unit (26) is configured to take into account, with the calibration model, a direction-dependent shading by a support platform (30) on which the radio receiver (20) is mounted, as an environmental influence when determining the position of the sonar buoy (22).

7. Radio receiver (20) according to one of claims 5 or 6, wherein the data processing unit (26) is configured to take into account, with the calibration model, the current flight altitude of a flying carrier platform (30) on which the radio receiver (20) is mounted, as an environmental influence when determining the position of the sonar buoy (22).

8. System (40) comprising a radio receiver (20) mounted on a carrier platform (30) according to one of the preceding claims and a sonar buoy (22), wherein the radio receiver is configured to determine the position of the sonar buoy.

9. System (40) according to claim 8, comprising a further radio receiver mounted on a further carrier platform, wherein the data processing unit (26) of the radio receiver (20) and the data processing unit of the further radio receiver are configured to exchange position determination information in order to determine an improved position of the sonar buoy.

10. Method for determining the position of a sonar buoy (22) comprising the following steps: a) Receiving a sequence of radio signals (28) from the sonar buoy (22) continuously from the time of deployment of the sonar buoy (22); b) Determining a received level of radio signals (28) of the sequence of radio signals; c) Determining the position of the sonar buoy (22) absolutely or relative to a radio receiver (20) based on a plurality of received levels of different radio signals or a sequence of radio signals.

11. Computer program comprising commands that are executed during the execution of the Programs by a computer cause it to execute steps b) and c) of the method according to claim 10 based on the sequence of radio signals received in step a).

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