Sonar system, method, and program

Abstract

To provide a sonar system that can estimate the shape of a towed array without using a sensor such as a compass.SOLUTION: A sonar system includes a reception processing device that calculates an arrival direction of a sound wave from reception data of the sound wave for each of a plurality of combinations different from each other of a plurality of receiving elements constituting an array, and estimates the shape of the array based on the arrival direction and an arrival time of the sound wave.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a reception processing device, a sonar system, a method, and a program. [Background technology]

[0002] Sonar is a device that uses sound waves to pinpoint the position of underwater objects. It has an array of multiple receiving elements that receive sound waves and obtains underwater acoustic information. The receiving elements convert the received sound waves into electrical signals. In a towed sonar, a platform such as a ship tows an array of multiple receiving elements on a cable. The cable and array are deformed by external forces such as the movement of the platform and ocean currents. This deformation is difficult to predict. This makes it difficult to estimate the exact position of the array as seen from the platform. Such position errors of the array affect signal processing and the like, adversely affecting the performance of the sonar itself.

[0003] For example, in Patent Document 1, a compass is set at the position of the line array receiver, and the coordinates of each receiver are obtained using the output of each compass and the known interval between the receivers, and the shape of the line array when it is deformed is obtained. In this way, by attaching a sensor such as a gyrocompass to the receivers that make up the array, the accuracy of estimating the position of the array as seen from the platform is improved. However, the same number of sensors (compasses) are required as the number of receivers that make up the array. In a towed sonar, since a large number of receivers are arranged, a large number of sensors (compasses) must be built into the array, which makes it impractical in terms of manufacturing costs, etc. In response to this problem, Patent Document 2 discloses a towing cable equipped with a compass, and a signal processing device receives compass direction information (compass direction) from the compass and received signals from each receiver of the line array through the towing cable, performs phasing processing using these compass directions and received signals, and detects the presence and direction of a target (for example, direction, depth, inclination, etc.) using the phasing output. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-261727 A [Patent Document 2] JP 2011-158391 A Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, with towed sonar, the shape of the array underwater cannot be accurately determined, which can cause errors in signal processing and the like, adversely affecting sonar performance.

[0006] The present invention has been devised in view of the above problems, and has an object to provide an apparatus, method, and program capable of estimating the shape of a towed array without relying on sensors such as a compass. [Means for solving the problem]

[0007] According to one aspect of the present invention, a reception processing device of a sonar system calculates the direction of arrival of sound waves from received data of sound waves for each of a number of different combinations of a number of receiving elements that make up an array, and estimates the shape of the array based on the direction of arrival and the arrival time of the sound waves.

[0008] According to one aspect of the invention, there is provided a method for estimating a shape of an array of receive elements in a towed sonar system, comprising the steps of: calculating an arrival direction of the sound wave from reception data of the sound wave for each of a plurality of different combinations of the receiving elements; An array shape estimation method is provided for estimating the shape of the array based on the directions of arrival and the times of arrival of the sound waves.

[0009] According to one aspect of the present invention, there is provided a program for causing a computer to execute a process for estimating a shape of an array of a plurality of receiving elements in a towed sonar system, the program comprising: A program is provided that calculates the direction of arrival of the sound waves from the received data of the sound waves for each of a plurality of different combinations of the receiving elements, and estimates the shape of the array based on the direction of arrival and the time of arrival of the sound waves. Furthermore, according to the present invention, there is provided a computer-readable recording medium (e.g., semiconductor storage such as RAM (Random Access Memory), ROM (Read Only Memory), or EEPROM (Electrically Erasable and Programmable ROM), HDD (Hard Disk Drive), CD (Compact Disc), DVD (Digital Versatile Disc)) storing the above program. Effect of the Invention

[0010] According to the present invention, it is possible to estimate the shape of the towed array without relying on sensors such as a compass. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of an embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram illustrating a schematic embodiment of the present invention. [Diagram 3] FIG. 1 is a diagram illustrating a schematic configuration of an embodiment of the present invention. [Figure 4] FIG. 1 is a diagram illustrating an embodiment of the present invention. [Diagram 5] FIG. 1 is a diagram illustrating an embodiment of the present invention. [Figure 6] FIG. 1 is a diagram illustrating an embodiment of the present invention. [Figure 7] FIG. 1 is a diagram illustrating a schematic configuration of an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of the present invention will be described. According to the present invention, the shape of the array is estimated by numerical calculation such as signal processing based on the acoustic signal received by each receiving element of the array in the towed sonar. Here, as the towed sonar, an array (line array) in which multiple receiving elements (receivers) are arranged in a line on a towing cable is assumed. In a platform such as a ship equipped with a towed sonar and a transmitting device, the shape of the array is estimated from the reception data of the receiving elements of the array. That is, when multiple receiving elements arranged on the line array receive an acoustic signal (sound wave) emitted from a certain sound source, the phase difference is calculated from the reception signals of adjacent receiving element pairs, and the direction of the sound source as seen from the midpoint of the receiving element pairs is calculated. By performing this calculation of the sound source direction between adjacent receiving element pairs of the line array, multiple azimuth lines of the sound source as seen from the line array can be drawn. When the position of the sound source is known, the shape of the line array as seen from the sound source can be estimated.

[0013] A sonar system 100 according to an embodiment of the present invention will be described with reference to Fig. 1. In Fig. 1, a transmission / reception control device 101, a transmission device 102, and a reception processing device 103 are arranged on a platform such as a ship. A plurality (N pieces) of reception elements 104 constituting an array (line array) 105 are towed by a cable (not shown) and electrically connected to the reception processing device 103.

[0014] The transmitting device 102 converts the transmission signal (electrical signal) supplied from the transmission / reception control device 101 into an acoustic signal (sound wave) and sends it out.

[0015] Each receiving element 104 receives sound waves, converts the sound waves into electrical signals, and sends the data to the reception processing device 103. Note that each receiving element 104 may convert the electrical signals converted from the sound waves into digital signal data using an analog-to-digital converter (not shown), and transmit the digital signal data to the reception processing device 103 via a cable transmission line (not shown). The reception processing device 103 is configured to be able to determine which receiving element 104 the data transmitted from each receiving element 104 came from.

[0016] The transmission / reception control device 101 sends information (data) such as the waveform of a signal to be transmitted from the transmission device 102 and the transmission time to the transmission device 102 and the reception processing device 103 .

[0017] The reception processing device 103 performs calculations on the data transmitted from the transmission / reception control device 101 and each receiving element 104 to estimate the shape of the array 105 .

[0018] 2 is a diagram for explaining a system according to an embodiment of the present invention. A ship 110 equipped with a transmission / reception control device 101, a transmission device 102, and a reception processing device 103 in FIG. 1 transmits a plurality of reception elements 104 (N reception elements 1041 to 1044) from the stern side of the ship. N ) tows an array 105 (also called a "towed array") connected by cables 106. Sound waves transmitted from a transmitting device 102 on the bottom side of the ship 110 are received by multiple receiving elements 104 of the array 105. The receiving elements 104 are composed of cylindrical hydrophones equipped with cylindrical sensing parts. The multiple receiving elements 104 of the array 105 are electrically connected to a receiving processing device 103 inside the ship 110 via cables 106.

[0019] Fig. 3 is a diagram for explaining the processing (functions) executed by the reception processing device 103 in Fig. 1. The reception data 1031 includes data obtained by converting the acoustic signals (sound waves) received by each reception element 104 into digital signals. The reception data 1031 from each reception element 104 may also include time information when the acoustic signals (sound waves) were received by each reception element 104.

[0020] The direction calculation process 1032 calculates the direction of arrival of the sound wave from a set of reception data 1031 from a pair of adjacent reception elements 104, using the frequency of the received sound wave and the distance between the reception elements.

[0021] FIG. 4 is a diagram for explaining the direction calculation process 1032. The arrival direction θ i is the distance between adjacent i-th and (i+1)-th receiving elements 104: d iThe frequency of the sound wave is f, the speed of sound is C, and the phase difference α between the adjacent i-th and (i+1)-th receiving elements 104 is calculated by the following formula (1): sin -1 is the inverse sine function.

[0022] TIFF0007596725000001.tif10150…(1)

[0023] However, the solution of equation (1) is the distance between the receiving elements d i is larger than the wavelength of the sound wave: C / f, i.e., d i If >C / f, then -π<θ i <π, and there are regions in which the arrival direction cannot be determined.

[0024] When the transmitting device 102, which is the sound source, uses sound waves with such wavelengths, the phase difference α is replaced by TIFF0007596725000002.tif6150…(2) In this case, (2n+1) arrival directions are obtained, but the true arrival direction can be obtained by performing the same calculation for sound waves of multiple wavelengths arriving from the same direction.

[0025] By performing the direction calculation process 1032 on the received data 1031 from adjacent receiving elements 104, multiple sound wave arrival direction lines can be drawn as shown in Fig. 5. In other words, the direction (arrival direction line) of each center between adjacent receiving elements with respect to the transmitting device 102, which is the sound source, is obtained. From Fig. 5, it can be seen that the position coordinates of the sound source (transmitting device 102) are calculated by the arrival direction line (arrival direction and the distance between the center between adjacent receiving elements and the sound source) and the distance d between adjacent receiving elements. i From this, the positions of adjacent receiving elements are obtained.

[0026] The shape estimation process 1033 estimates the shape of the array by using the arrival time of the sound waves (the reception time of the sound waves at the receiving elements 104) calculated from the reception data 1031, the result of the direction calculation process 1032, and the like. The distance between the receiving elements 104 and the sound source is found from the transmission time and arrival time of the sound waves from the transmission / reception control device 101. Specifically, for example, the coordinates of adjacent i-th and (i+1)-th receiving elements 104 are found using the following equations (3) to (6) for variables such as those shown in Fig. 6.

[0027] In FIG. 6, the receiving element coordinates (x i , y i ), (x i+1 , y i+1 ) are the adjacent i-th and (i+1)-th receiving elements (receiving elements 104 in FIG. 2). i , 104 i+1 (i=1,...,N-1)) is a two-dimensional position coordinate, and (x0, y0) is a two-dimensional position coordinate of the sound source (transmitting device 102). In FIG. 6, the horizontal direction is the x coordinate (x-axis) and the vertical direction is the y coordinate (y-axis). In this embodiment, the coordinates of the receiving element 104 and the sound source are projected coordinates onto a two-dimensional plane parallel to the sea surface, for example. This is because the receiving element 104 of the array 105 is designed to be parallel to the sea surface using, for example, a neutrally buoyant cable, and the error is small even when handled on a two-dimensional plane. In other words, even if the value of the Z-axis coordinate (depth) is the same, the estimation error of the array shape is small. Therefore, the shape of the array estimated by the shape estimation process 1033 is a shape projected onto a two-dimensional plane.

[0028] In Figure 6, d i , adjacent receiving elements 104 i , 104 i+1 The distance between the sound source and the receiving element is known. i , adjacent receiving elements 104 i , 104 i+1 The sound source distance l is the distance from the center of the sound source (the transmitting device 102 in FIG. 1). i The receiving element 104 i , 104 i+1Alternatively, the distance (already calculated) to the sound source (transmitting device 102 in FIG. 1) calculated by each of the adjacent receiving elements 104 may be used as the arithmetic average. i , 104 i+1 Regarding the cable positive lateral orientation φ i is the true direction from true north. i , adjacent receiving elements 104 i , 104 i+1 is the direction of arrival of the sound wave at the center of the sound source (already calculated). From FIG. 6, it can be seen that the following equations (3) to (6) hold true.

[0029] TIFF0007596725000003.tif14150…(3)

[0030] TIFF0007596725000004.tif9150…(4)

[0031] TIFF0007596725000005.tif6150…(5)

[0032] TIFF0007596725000006.tif6150…(6)

[0033] Adjacent receiving elements 104 i , 104 i+1 Cable positive lateral direction φ for (i=1,..,N-1) i When (i=1, .., N-1) is known, the adjacent receiving elements 104 are calculated from the above equations (3) to (6). i , 104 i+1 Position coordinates (x i , y i ), (x i+1 , y i+1 ) is obtained.

[0034] On the other hand, the cable normal horizontal direction φ1 for the first and second adjacent receiving elements 1041 and 1042 is known, but the cable normal horizontal direction φ1 for the adjacent receiving element 104 i , 104 i+1 Cable positive lateral direction φ for (i=2,..,N-1) iWhen is unknown, first, the position coordinates (x1, y1) of the first receiving element 1041 are found from, for example, the following equations (7) and (8).

[0035] TIFF0007596725000007.tif9150…(7)

[0036] TIFF0007596725000008.tif9150…(8)

[0037] Then, from the position coordinates (x1, y1) of the first receiving element 1041, the position coordinates (x2, y2) of the second receiving element 1042 are found using the recurrence formulas (5) and (6) above.

[0038] The cable positive horizontal direction φ2 for the adjacent second and third receiving elements 1042 and 1043 may be calculated using a relational expression (inverse trigonometric function) that holds between φ2, the position coordinates (x2, y2) of the second receiving element 1042, the sound source coordinates (x0, y0), the receiving element distance d2, and the sound source distance l2, and the position coordinates (x3, y3) of the third receiving element 1043 may be recursively calculated using equations (5) and (6). i For (i=3,..,N-1), φ i and the position coordinate of the i-th receiving element (x i ,y i ) and the sound source coordinates (x0, y0) and the distance between the receiving elements d i and sound source distance l i Using the equation (the inverse trigonometric function equation) i From the equations (5) and (6), the (i+1)th receiving element 104 i+1 Position coordinates (x i+1 ,y i+1 ) may be calculated recursively.

[0039] According to this embodiment, in a towed sonar system, the direction of arrival of an acoustic signal (sound wave) transmitted from a transmitting device (sound source) is obtained from the signal received at the array, and the position coordinates of the multiple receiving elements that make up the array are calculated by arithmetic processing based on the direction of arrival, the distance to the sound source, and the position coordinates of the sound source. Therefore, the shape of the array can be estimated without attaching sensors such as gyros to the receiving elements of the array.

[0040] FIG. 7 is a diagram for explaining an embodiment of the present invention, and is a diagram for explaining a configuration in the case where the reception processing device 103 of FIG. 1 is implemented in a computer device 200. Referring to FIG. 7, the computer device 200 includes a processor 201, a storage device 202 such as a semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read-Only Memory) (or may be a HDD (Hard Disk Drive) or the like), a display device 203, and an interface 204 that connects to the transmission / reception control device 101 and the receiving element 104 of FIG. 1. The processor 201 may be a DSP (Digital Signal Processor). By executing a program stored in the storage device 202, the processor 201 executes the processing of the reception processing device 103 of FIG. 3.

[0041] Although FIG. 2 shows an example of a line array towed from a ship, this embodiment can be widely used in cases where it is desired to estimate the relative positions of a plurality of receiving elements.

[0042] 3, for the sake of simplicity, the direction calculation process 1032 uses the reception data 1031 from two adjacent receiving elements 104, but it goes without saying that the reception data used in the direction calculation process 1032 does not necessarily have to be adjacent. For example, the direction calculation process 1032 may perform calculations from three or more reception data 1031.

[0043] Regarding the direction calculation process 1032, a process using sound waves of multiple wavelengths when the distance d between the receiving elements is greater than the wavelength of the sound wave has been described. However, it is also possible to use a process in which two beams with close beam centers are created and the direction of arrival is calculated from the phase difference between them.

[0044] In this embodiment, the sound waves received by the receiving elements 104 of the array 105 may be not only direct waves from the transmitting device 102 as illustrated in FIG. 2, but may also be sound waves containing time information, such as reflected waves from a target. Sounds emitted by a target include sounds that are constantly generated from sources such as an engine, and sounds that are generated for a short period of time, such as when steering a ship. Transient sounds that are generated for a short period of time are called transient signals. The sound waves received by the receiving elements 104 of the array 105 may be transient signals from a target.

[0045] The disclosures of Patent Documents 1 and 2 are incorporated herein by reference. Modifications and adjustments of the embodiments and examples are possible within the scope of the entire disclosure of the present invention (including the scope of claims), and further based on the basic technical ideas. Furthermore, various combinations and selections of the various disclosed elements (including each element of each claim, each element of each example, each element of each drawing, etc.) are possible within the scope of the claims of the present invention. In other words, the present invention naturally includes various modifications and alterations that a person skilled in the art would be able to make in accordance with the entire disclosure including the scope of claims and the technical ideas. [Explanation of symbols]

[0046] 100 Sonar System 101 Transmission and reception control device 102 Transmitting device 103 Receiving processing device 104, 1041-104 N Receiving element 105 Line Array 106 Cable 110 Ship 200 Computer Equipment 201 Processor 202 Storage device 203 Display device 204 Interface 1031 Received Data 1032 Direction calculation processing 1033 Shape Estimation Processing

Claims

1. A reception processing device for a sonar system, comprising: A receiving processing device characterized in that, for each of a number of different combinations of a number of receiving elements connected by a towing cable to form an array, the device calculates the direction of arrival of the sound waves from the received data of the sound waves, and estimates the shape of the array based on the direction of arrival and the time of arrival of the sound waves.

2. For each pair of two adjacent receiving elements of the plurality of receiving elements constituting the array, calculate an arrival direction of the sound wave from the reception data of the sound wave; The position coordinates of the sound source of the sound wave; For each pair of two adjacent receiving elements, The arrival direction, the distance between the receiving elements, the distance to the sound source, and the true horizontal direction of the cable based on true north; Based on 2. The reception processing device according to claim 1, further comprising: a receiving device for receiving a signal from said receiving element;

3. 3. The reception processing device according to claim 2, wherein position coordinates of each of the receiving elements and the sound source are calculated on two-dimensional coordinates obtained by projecting each of the receiving elements and the sound source onto a two-dimensional plane, and a shape of the array is estimated on the two-dimensional plane.

4. A plurality of receiving elements forming an array; A reception processing device according to any one of claims 1 to 3, A transmitting device for transmitting sound waves; a control device that provides a transmission waveform and a transmission time to the transmitting device; Equipped with The control device provides at least the transmission time of the sound wave to the reception processing device, A sonar system characterized in that the reception processing device determines a distance to a sound source of the sound wave from a transmission time of the sound wave and a reception time of the sound wave at the receiving element.

5. The plurality of receiving elements constituting the array include A direct wave from the transmitting device, Reflected waves from the target, receiving any of the transient signals from the target; 5. The sonar system according to claim 4, wherein said reception processing device estimates a shape of said array from reception data of said plurality of receiving elements that constitute said array.

6. 6. The sonar system according to claim 4, wherein the receiving element has a cylindrical sensing portion and is towed from a platform by the cable.

7. 1. A method for estimating a shape of an array of receive elements in a towed sonar system, comprising: an array shape estimation method comprising: calculating an arrival direction of the sound wave from received data of the sound wave for each of a plurality of different combinations of the receiving elements; and estimating a shape of the array based on the arrival direction and the arrival time of the sound wave.

8. For a plurality of receiving elements connected by a towing cable to form the array, for each pair of adjacent receiving elements, a direction of arrival of the sound wave is calculated from the received data of the sound wave; 8. The array shape estimation method according to claim 7, further comprising the step of calculating position coordinates of each receiving element based on the position coordinates of the sound source of the sound waves, the direction of arrival for each pair of two adjacent receiving elements, the distance between the receiving elements, the distance to the sound source, and the forward lateral direction of the cable relative to true north.

9. A program for causing a computer to execute a process for estimating a shape of an array consisting of a plurality of receiving elements in a towed sonar system, comprising: A program that calculates an arrival direction of the sound wave from received data of the sound wave for each of a plurality of different combinations of the receiving elements, and estimates a shape of the array based on the arrival direction and the arrival time of the sound wave.

10. For a plurality of receiving elements that are connected by a towing cable and that constitute the array, a direction of arrival of the sound waves is calculated from the reception data of the sound waves for each pair of adjacent receiving elements; 10. The program according to claim 9, which causes the computer to execute a process of calculating the position coordinates of each receiving element based on the position coordinates of the sound source of the sound wave, the arrival direction for each pair of two adjacent receiving elements, the distance between the receiving elements, the distance to the sound source, and the true horizontal direction of the cable relative to true north.

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