Radio receiver for determining the position of a sonar buoy

Abstract

A radio receiver (20) for determining the position of a sonar buoy (22) is disclosed, comprising a receiving unit (24) and a data processing unit (26). The receiving unit (24) is configured to continuously, and in particular continuously, receive a sequence of radio signals (28) from the sonar buoy (22) from the moment it is deployed. The data processing unit (26) is configured to determine the received level of the radio signals (28) in the sequence of radio signals and, based on a plurality of received levels of different radio signals (28) in the sequence of radio signals, to determine the position of the sonar buoy (22) absolutely or relative to the radio receiver (20).

Description

The invention relates to the determination of the position of a non-locally fixed, in particular self-applied, sonar buoy.Sonar buoys are operated temporarily, a few days, and most often only a few hours, in a body of water, in particular in the sea. After that, the sonar buoys can no longer be used. They are left over or destroyed by themselves. For this reason, the sonar buoys are produced as favorably as possible and there is often no need for the buoys to be fixed in a costly manner on the bottom of the body of water. Without fixation, however, the buoys are exposed to the environment. After the application, the sonar buoys drift, in particular due to flow and wind, and leave their original application position.For this reason, the sonar buoys are usually equipped with GPS sensors (global positioning system). However, the GPS system can fail or be disturbed in crisis times or the GPS sensors, which are particularly favorable, can fail. Without the current position of the sonar buoy, the position of a detected target that can be determined only relative to the sonar buoy can no longer be determined reliably. This effect increases with time due to the natural drift of the sonar buoy.The object of the present invention is therefore to provide an improved concept for determining the position of sonar buoys.The object is achieved by the subject matter of the independent claims. Further advantageous embodiments are the subject matter of the dependent claims.Embodiments show a radio receiver for determining a position of a sonar buoy. The radio receiver comprises a receiving unit and a data processing unit. The receiving unit is configured to receive a sequence of radio signals from the sonar buoy continuously from the time of suspension of the sonar buoy. That is, the buoy is activated on board a discharging platform or immediately after being exposed to the body of water. After exposure, the sonar buoy receives water sound with a plurality of water sound transducers disposed in the sonar buoy. The resulting water-borne sound signals are transmitted by the sonar buoy by means of a sequence of radio signals and can thus be received by the receiving unit. The sequence of radio signals may represent a continuous radio transmission. The radio receiver is optionally arranged on the dispensing platform. The discharging platform can be a watercraft, for example a manned or unmanned ship, or an aircraft, for example a helicopter, an aircraft or a (flying) drone.The water-borne sound signals transmitted with the radio signals can be evaluated by the platform on which the radio receiver is arranged. For example, the direction can be determined there from which sound components of the water sound impinge on the water-sound transducers. The direction can be determined, for example, by means of direction formation (beamforming), for example also only on the basis of gradient formation (i.e. the direction formation on the basis of dipoles, cf. DIFAR Buoy). Furthermore, the position of a transmitter of the sound components can be determined directly via runtime differences of the water sound to different sonar buoys. As a third option, the position of the transmitter can also be determined without beamforming, based on at least three sonar buoys arranged in an area, based on the propagation time differences of the sound components (TDoA).The data processing unit determines a reception level of the radio signals of the sequence of radio signals and, based on a plurality of reception levels of different radio signals of the sequence of radio signals, determines the position of the sonar buoy in absolute terms or relative to the radio receiver. That is, the reception level of the radio signals from the sonar buoy is continuously determined. Physically, it is now possible to infer the distance of the sonar buoy from one reception level and a position of the sonar buoy from a plurality of reception levels. Usually, from the distance of the sonar buoy to the radio receiver and the direction of the incident radio signals, first the position of the sonar buoy relative to the radio receiver is determined. If knowledge of the absolute position is necessary, the relative position of the sonar buoy relative to the radio receiver can be converted into an absolute position if the absolute position of the radio receiver is known. This is generally known with sufficient accuracy, even in the event of a failure of the GPS system.It is thus an idea to use the radio signals of the sonar buoys in order to determine the position of the sonar buoy that changes as a result of the drift of the sonar buoy and thus to improve the location of sound emitters under water.In embodiments, after suspension of the sonar buoy, the data processing unit may estimate parameters for a model having as input parameters the reception level and as output parameters a distance of the sonar buoy to the radio receiver. Knowing the position of the radio receiver and the sonar buoy, or at least their relative position to one another, is advantageous here. For modeling the distance (D in meters) of the sonar buoy to the radio receiver based on the reception strength (E in decibels), for example, the following formula can be used approximately:The unknown parameters X and S can be estimated so that the distance (D) between radio receiver and sonar buoy can be determined. X may be referred to as an attenuation factor. S may be referred to as a transmission level.That is, this or an alternative linear model may be used for determining the distance of the sonar buoy to the radio receiver. A linear model has a low complexity and therefore requires only a small amount of computing power.The parameters (e.g., X and S) may be more robust determined by linear regression using a plurality of (e.g., consecutive) measurements of the reception strength. When using linear regression, measurement inaccuracies of individual measurements are less important. The distance determination can also be made more robust, for example by averaging the reception strength or the resulting distance. Here, a moving average value is appropriate in the continuous determination of the distance.In exemplary embodiments, however, the data processing unit can also use a Kalman filter, in particular a nonlinear Kalman filter, for determining the position of the sonar buoy on the basis of the distance of the sonar buoy from the radio receiver.In further embodiments, the data processing unit may use a calibration model to take account of known environmental influences on the reception level in determining the position of the sonar buoy. The calibration model can map further influences on the reception level that are not taken into account by the linear model in order to improve the determination of the distance between sonar buoy and radio receiver. The calibration model may be determined in advance for a combination of platform and a radio receiver mounted at a predetermined location. In addition to checking or alternatively to creating the model, it is also possible for the platform to initially carry out a calibration run in order to be able to receive radio signals of the sonar buoy from all directions.For example, the data processing unit with the calibration model can take into account a direction-dependent shadowing by a carrier platform on which the radio receiver is mounted as an environmental influence in the determination of the position of the sonar buoy. Thus, for example, due to the arrangement of the radio receiver on a platform, a direction-dependent shadowing, i.e. attenuation of the radio signal depending on a reception direction, can occur. If the radio receiver is mounted on a ship, the bridge or other superstructures, such as e.g. containers, antennas, etc., can ensure that the radio receiver is shaded from specific reception directions. This attenuation can be taken into account in the measurement of the reception level, for example by an additive or multiplicative amplification factor.It is likewise possible to take into account, with the calibration model, a current flight height of a flying carrier platform on which the radio receiver is mounted as an environmental influence in the determination of the position of the sonar buoy. The flight altitude also has an influence on the reception level. The flight altitude influences the line of sight (line of sight) which has an influence on reception. Below any cloud layer, the attenuation is, for example, less than above. Likewise, the damping due to the different air pressures is not linear with the flight height of the carrier platform.Further disclosed is a system comprising a pre-described radio receiver mounted on a support platform and a sonar buoy. The radio receiver can determine the position of the sonar buoy. Furthermore, the system may comprise a further radio receiver mounted on a further carrier platform. The data processing unit of the radio receiver and the data processing unit of the further radio receiver can exchange position determination information in order to determine an improved position of the sonar buoy. That is to say, a data fusion of both data processing units can be carried out, so that the position of the sonar buoy can be carried out, for example, as a function of the distance of the sonar buoy to both radio receivers. It is also possible for the system to have a plurality of sonar buoys, wherein the radio receiver and / or the two radio receivers determine the position of the sonar buoys of the plurality of sonar buoys.Analogously, a method for determining a position of a sonar buoy is disclosed, comprising the following steps: a) receiving radio data from the sonar buoy continuously from the time of suspension of the sonar buoy; b) determining a reception 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 reception levels of different radio data.Also disclosed is a computer program comprising instructions which, when the program is executed by a computer, cause the computer to execute steps b) and c) of the method based on the sequence of radio signals received in step a). Any further method steps can likewise be carried out by means of the computer program.Preferred embodiments of the present invention will be explained below with reference to the accompanying drawings. It shows: FIG. 1 : shows a schematic block diagram of a radio receiver for determining the position of a sonar buoy on a carrier platform and the sonar buoy floating in the water body.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 identical or identically acting elements, objects and / or structures are provided with the same reference numerals in the different figures, with the result that the description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another.FIG. 1 shows a radio receiver 20 for determining a position of a sonar buoy 22. the radio receiver 20 comprises a receiving unit 24, here shown 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 arranged, for example, on a platform 30, here shown as a ship. The sonar buoy 22 can also be discharged from the platform 30. After the exposure, the sonar buoy 22 receives water sound 32 with a plurality of water sound transducers 34 arranged in the sonar buoy. The resulting water sound signals 36 are transmitted from 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.The data processing unit 26 determines a reception level of the radio signals 28 of the sequence of radio signals and, based on a plurality of reception levels of different radio signals 28 of the sequence of radio signals, determines the position of the sonar buoy 22 in absolute terms or relative to the radio receiver 24 or relative to the platform 30.The disclosed (water) sound transducers are designed for use underwater, in particular in the sea. The acoustic transducers may convert water sound into an electrical signal (e.g., voltage or current) corresponding to the sound pressure, the (received) water sound signal. Moreover, it is possible that the sound transducers can convert an applied electrical voltage into water sound. The electrical voltage can follow a predetermined pattern and then be referred to as a sonar signal (to be transmitted), while the water sound resulting from the sonar signal to be transmitted is referred to as a sonar signal (transmitted). Examples of sonar signals are a chirp (frequency-modulated signal) or, as a special case of the chirp, a sweep (linear frequency-modulated signal). The sound transducers can therefore be used as water-borne sound receivers and / or as water-borne sound transmitters. As a sensory material, the sound transducers can have a piezoelectric material, for example a piezoceramic. A plurality of water-borne transducers or one or more water-borne transducers in connection with a signal processing unit may be referred to as sonar systems. The sound transducers can be used for (active and / or passive) sonar (sound navigation and ranging, dt: sound navigation and distance determination). The sound transducers are preferably not suitable for medical applications or are not used for medical applications. Likewise, the sound transducers are preferably not used for the ultrasonic testing of materials or are not suitable for this purpose.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 a 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 represent a description of a corresponding block or detail or feature of a corresponding device.Depending on the implementation requirements, embodiments of the invention may be implemented in hardware or software. The implementation can be carried out using a digital storage medium, for example a magnetic or optical memory, on which electronically readable control signals, for example a computer program, are stored, which can cooperate or cooperate with a programmable computer system (CPU and / or GPU) in such a way that the respective method is carried out. For this reason, the digital storage medium should be computer readable. Embodiments may therefore comprise a data carrier having electronically readable control signals which are capable of interacting with a programmable computer system in such a way that one of the methods described herein is carried out.In some embodiments, a programmable logic device (e.g., a field programmable gate array, an FPGA) may be used to perform some or all of the functionalities of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor to perform any of the methods described herein. Generally, in some embodiments, the methods are performed by any hardware device. This can be universally usable hardware such as a computer processor (CPU) or a graphics processor (GPU) or hardware specific to the method, such as an ASIC. Distributed execution on CPU and GPU is also possible.The above-described embodiments are merely illustrative of the principles of the present invention. It is to be 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 herein by way of description and explanation of the embodiments.List of reference numbers:20 Radio receiver 22 sonar buoy 24 receiving unit 26 data processing unit 28 radio signal 30 platform 32 water sound 34 water sound converter 36 water sound signal 38 antenna of the sonar buoy

Claims

Radio receiver (20) for determining a position of a sonar buoy (22), having the following features: - a receiving unit (24) which is designed to receive a sequence of radio signals (28) from the sonar buoy (22) continuously, in particular continuously, from the time of suspension of the sonar buoy (22); - a data processing unit (26) which is designed to determine a reception level of the radio signals (28) of the sequence 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 sequence of radio signals.Radio receiver (20) according to claim 1, wherein the data processing unit (26) is configured to estimate parameters for a model after the sonar buoy (22) has been suspended, wherein the model has the reception level as an input parameter and a distance of the sonar buoy (22) from the radio receiver (20) as an output parameter, and wherein there is knowledge about the position of the radio receiver (20) and the position of the sonar buoy (22), or at least their relative position to one another.Radio receiver (20) according to one of the preceding claims, wherein the data processing unit (26) is designed to use a linear model as a model for determining a distance of the sonar buoy (22) from the radio receiver (26).Radio receiver (20) according to one of claims 2 or 3, wherein the data processing unit (26) is configured to use a Kalman filter for determining the position of the sonar buoy (22) based on the distance of the sonar buoy (22) from the radio receiver (20).Radio receiver (20) according to one of the preceding claims, wherein the data processing unit (26) is configured to use a calibration model to take account of known environmental influences on the reception level in the determination of the position of the sonar buoy (22).Radio receiver (20) according to Claim 5, wherein the data processing unit (26) is designed to take into account, with the calibration model, directional shadowing by a carrier platform (30) on which the radio receiver (20) is mounted, as an environmental influence in the determination of the position of the sonar buoy (22).Radio receiver (20) according to either of Claims 5 and 6, wherein the data processing unit (26) is designed to take into account, with the calibration model, a current flight height of a flying carrier platform (30) on which the radio receiver (20) is mounted, as the environmental influence in the determination of the position of the sonar buoy (22).A system (40) comprising a radio receiver (20) according to any preceding claim mounted on a support platform (30) and a sonar buoy (22), the radio receiver being configured to determine the position of the sonar buoy.The 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.Method for determining a 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 suspension of the sonar buoy (22); b) determining a reception level of radio signals (28) of the sequence of radio signals; c) determining the position of the sonar buoy (22) absolute or relative to a radio receiver (20) based on a plurality of reception levels of different radio signals of the sequence of radio signals.A computer program comprising instructions which, when the program is executed by a computer, cause the computer 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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