Passive hydroacoustic system for determining coordinates of underwater objects in group

Abstract

FIELD: multi-channel hydroacoustic systems.SUBSTANCE: invention which can be used for monitoring underwater conditions, detecting in a given field of view and determining the coordinates of each underwater object in a group that emits or scatters acoustic signals with a priori unknown parameters. The hydroacoustic system consists of a multi-position passive hydroacoustic station, a differential delay pair calculator, and a calculator for the coordinates of underwater objects. The claimed device is a hydroacoustic system for determining the coordinates of underwater objects in a group, containing a multi-position passive hydroacoustic station with three non-directional receivers that form two identical processing channels containing a cross-correlation function calculator, a modulus calculator and a maximum moment determinator, as well as a calculator of differential delay pairs for underwater objects and a calculator of the coordinates of underwater objects in a group. The listed components of the claimed device are interconnected in a certain way.EFFECT: expansion of the functional capabilities of hydroacoustic systems, which consists in the ability to determine the coordinates of each underwater object in a group in passive location mode under conditions of a priori uncertainty in the parameters of acoustic signals.1 cl, 2 dwg

Description

[0001] The present invention relates to multi-position hydroacoustic systems (HAS) and can be used to position a group of underwater objects (OO) emitting or scattering acoustic signals with a priori unknown parameters. Positioning of the group of underwater objects is based on calculating their coordinates based on the relative delays of the acoustic signals arriving from each object in the group to each of the three receiving antennas of the multi-position passive HAS.

[0002] The classic differential ranging method (DRM), based on measuring the curvature of the signal wavefront, uses three collinearly positioned omnidirectional antennas and, based on the delays in the arrival of signals relative to each other, determines the coordinates of a single target. DRM does not require determining the target bearing, significantly simplifying its implementation compared to direction finders and multibeam echo sounders, which solve this problem. Furthermore, the DRM sonar operates in passive mode, ensuring the concealment of its location [1-3].

[0003] The RDM is based on the difference in distances from a single object to three collinear antennas, each positioned in a known manner. The distance from the PO to each antenna is determined by the difference in delays between the signals arriving at each antenna, measured by calculating the cross-correlation functions (CCF) of the received signals.

[0004] The derivation of algorithms that make it possible to determine the coordinates of a single underwater object based on the delays in the moments of reception of its signals in a three-channel sonar with non-directional antennas, and the final calculation formulas, as well as a description of the methods and algorithms for digital spatio-temporal processing of hydroacoustic signals are given in the works [4-7].

[0005] There are known similar in purpose GAS and devices intended for monitoring the underwater environment and determining the coordinates of underwater objects based on the curvature of the wave front of the radiation source field by receiving antennas spaced in a known manner in space and measuring the difference in the arrival times of the signal from the radiation source to several receivers.

[0006] U.S. Patent No. 3,947,803, issued March 30, 1976 [8], describes a system for determining the direction to an object and its range relative to a given position. This involves receiving the sound energy emitted by the object via three antennas arranged in a known manner, determining the cross-correlation functions (CCF) of the signals in the antennas, determining the difference in signal propagation time to pairs of antennas based on the position of the CCF maxima on the delay scale, and using these data to calculate the range and direction to the object.

[0007] However, if there are several radiation sources in the observation field, the use of this method is impossible due to the ambiguity of assigning the VCF maxima to one or another source.

[0008] US Patent No. 4910719 dated March 20, 1990 [9] proposes a method of passive sound telemetry, according to which signals from a sound source are received by three linearly arranged antennas, processed by determining the CCF of the signal from the central antenna with the signals from the other two antennas, and then, using an iterative procedure, the parameters of the relative position of the main CCF maxima on the delay scale are determined, from which the range and direction to the radiation source are calculated.

[0009] Along with the increased noise immunity of the method and the reduced volume of computational procedures, this method is not without its main drawback [8], that is, the impossibility of determining the coordinates of several radiation sources.

[0010] The Russian Federation patent for invention No. 2788476 C1 dated 21.12.2021

[10] proposes a method for determining the coordinates of radiation sources using a passive sonar, which includes receiving signals by three or more antennas that form fans of directional spatial channels, calculating for each cell of the coordinate grid (CG) indication “direction-range” of the VCF of signals from all antennas and determining the coordinates of all radiation sources based on the position of the main maxima of their signal marks on the CG scales.

[0011] Despite the fact that the considered method allows one to determine the coordinates of several radiation sources, it has the following disadvantages:

[0012] - a structurally complex wide-aperture receiving system is required, each receiving antenna of which must form a fan of directional spatial channels;

[0013] - requires the implementation of complex and resource-intensive algorithms for digital processing of received signals in real time;

[0014] - the calculation of the coordinates of the acoustic radiation sources is not performed, as a result of which the accuracy of measuring the coordinates of the hydroacoustic signal source is limited by the error in the graphic display of signal marks on the observer-operator indicator.

[0015] The closest analogue of the claimed invention is the calculator of coordinates of a single source of hydroacoustic radiation, described in

[11] , which was chosen as a prototype.

[0016] Determination of the coordinates of a single PO emitting or scattering acoustic signals with a priori unknown parameters is achieved by using a multi-position passive sonar system containing three non-directional receiver antennas with analog-to-digital converters (ADC) of the received signals, the outputs of which are connected to two processing channels consisting of series-connected VKF calculators, module calculators (MC), maximum moment detectors (MMD) of the received signal and an underwater object coordinate calculator (UOCC), the inputs of which are connected to the outputs of the first and second channels of a three-position hydroacoustic station, and the UOCC output is the output of the sonar system for determining the coordinates of a single PO.

[0017] However, the prototype suffers from the same shortcomings as the similar devices discussed above. It can only determine the coordinates of a single POE emitting or scattering signals with a priori unknown parameters. The prototype lacks a technical solution for determining the coordinates of each POE in a group of several POEs, as each receiver (after each ADC) will have multiple responses (the number of responses is equal to the number of POEs), and it is unknown which response corresponds to which POE.

[0018] The proposed invention is aimed at overcoming the indicated disadvantages of the prototype and analogues.

[0019] To solve the stated problem - determining the coordinates of each object in a group of several objects - a series-connected differential delay pair calculator (DDP) for underwater objects and a calculator of coordinates of underwater objects in a group (UOC) are introduced into the known prototype device, two inputs of the DDP are connected to the outputs of the first and second maximum moment determinants, and the UOC output is the output of the passive GAS for determining the coordinates of the objects in a group.

[0020] By introducing a set of essential distinctive features into the known prototype device, the proposed invention provides a technical result - determining the coordinates of each PO in a group that emits or scatters acoustic signals with a priori unknown parameters.

[0021] The essence of the proposed invention is explained by the structural diagram shown in Fig. 1, where it is indicated:

[0022] 1, 5, 6 - analog-to-digital converter (ADC) of a three-position passive hydroacoustic system;

[0023] 2 - VKF (VVKF) calculator of received signals of the first and second input receivers;

[0024] 7 - VKF (VVKF) calculator of received signals of the second and third input receivers;

[0025] 3, 8 - calculators of modules (CM) of signals of the first and second processing channels;

[0026] 4, 9 - maximum moment detectors (MMD) of signals of the first and second processing channels;

[0027] 10 - differential delay pair calculator (DDP);

[0028] 11 - underwater object coordinate calculator (UOC) in the group.

[0029] The essence of the proposed invention is that the unknown signal received by the multi-position passive GAS in each of the three receivers is converted into digital form using an ADC and in the first and second processing channels is processed in the same way in the series-connected VVKF 2, VM 3, OMM 4 and VVKF 7, VM 8, OMM 9. If a group of N underwater objects is present in the analyzed zone, the signals at the outputs of VM 3 and VM 8 will have M maxima, N≤M≤N 2 , corresponding to these PO (the maximum value of M is when all emissions are highly correlated, the minimum is when all POs emit uncorrelated signals). The estimates of the moments of signal maxima in each processing channel obtained in OMM 4 and OMM 9 are fed to VPRZ 10.

[0030] 8 VPRZ 10 calculates the differences in the moments of the maximum of the CCF relative to each other in two processing channels and generates pairs of differential delays. The number of pairs of differential delays is equal to the number of their "each with each" combinations in the two processing channels and, therefore, is equal to M 2 . From M 2 N pairs of differential delays are selected, corresponding to each software n in the group (n=1,2,…, N).

[0031] The selection of pairs of differential delays in the VPRZ 10 is made on the basis of the calculated relationships obtained from the consideration of the collinear antenna system of non-directional receivers A1, A2, A3 and some n-th PO n (X n ,u n ), which is part of a group of N hydroacoustic radiation sources, as shown in Fig. 2.

[0032] Using the cosine law, we determine the value of cosθ 1n from triangles A1POnA2 and A1PO n A3 and we equate the obtained values:

[0033]

[0034] where R 2n - the distance between the central receiving element A2 and the software in question n ;

[0035] L1, L2 - shoulders of the receiving collinear antenna system;

[0036] τ 21n - differential delay of the software signal n , received by the first and second input receivers, calculated in VPRZ 10 according to the data of OMM 4;

[0037] τ 32n - differential delay of the software signal n , received by the second and third input receivers, calculated in VPRZ 10 according to the data of OMM 9;

[0038] c - the speed of sound in water.

[0039] From (1) we determine the distances between the central receiving element A2 and PO n :

[0040]

[0041] Considering the impossibility of a priori unambiguous comparison of the calculated differential delays τ 21 and τ 32 with specific software, a sequential search of all pairs of delays (τ) is performed 21i , τ 32j ) where i=1,2,…, M 2and j=1,2,…, M 2 - indices of the maximum responses at the output of OMM 4 and OMM 9, respectively.

[0042] For a combination of indices i=p and j=q, the condition for making a decision on the membership of a pair of differential delays (τ 21p , τ 32q ) one software, the number n of which is uniquely determined by a unique combination of indices p and q, is the equality

[0043] θ 2pq +θ доп pq =180°, (3)

[0044] where θ 2pq - the angle between the base of the receiving antenna system of the passive sonar and the direction to the n-th underwater object;

[0045] θ доп pq - angle complementary to θ 2pq to the straight angle.

[0046] The angles included in equality (3) at the central receiving element of the antenna system A2 are determined by the cosine law:

[0047] - angle θ 2pq from triangle A2PO n A3:

[0048]

[0049] - angle θ доп pq from triangle A1PO n A2: where in accordance with (2)

[0050]

[0051] After searching through all the combinations of indices i and j, pairs of differential delays (τ) will be selected 21n , τ 32n ), n=1,2,…,N, corresponding to all radiation sources.

[0052] Next, in VKPO 11, the coordinates in the Cartesian coordinate system of all the software in the group are calculated using (4) and (5), while each unique pair of indices p and q generated in VPRZ 10 corresponds to a specific software number n:

[0053] x n= R 2n cosθ 2n ; x n= R 2n sinθ 2n ,

[0054] n=1,2,…, N

[0055] Thus, the proposed technical solution provides the ability to determine the coordinates of each PO in a group of objects emitting or scattering signals with a priori unknown parameters.

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[0058] 3. Chernyak VS Multiposition radar. - M.: Radio and Communications, 1993. - 416 p.

[0059] 4. Maryev A.A., Markovich I.I., Zavtur E.E. Study of errors of the difference-ranging method of passive location / / Radiation and scattering of electromagnetic waves IREMV-2015: Proceedings of the International Scientific Conference - Divnomorskoye: Southern Federal University, 2015. - P. 395-399.

[0060] 5. Markovich I.I. Digital signal processing in systems and devices: monograph. - Rostov n / D: Publishing house of SFedU, 2012. - 236 p.

[0061] 6. Markovich I.I. Methods and algorithms for digital spatio-temporal processing of hydroacoustic signals in multibeam echo sounders and obstacle locators / / Fundamental and Applied Hydrophysics. - 2014. - Vol. 7, No. 2. - P. 58-71.

[0062] 7. Markovich I.I., Zavtur E.E. Algorithm for determining target coordinates using the difference-ranging method taking into account the inaccuracies in the installation of receiving hydroacoustic antennas / / Bulletin of SFedU. Technical sciences. - 2017. - No. 8 (193). - P. 162-171.

[0063] 8. US Patent 3947803, IPC G01S 3 / 80, Direction finding system; Claimed 12.05.1971. Published 30.03.1976.

[0064] 9. US Patent 4910719, IPC G01S 5 / 18, Passive sound telemetry method; Claimed 20.04.1988. Published 20.03.1990.

[0065] 10. Patent 2788476 C1, Russian Federation, IPC G01S 3 / 80 (2006.01). Method for determining the coordinates of radiation sources using a passive sonar. No. 2021138452. Claimed 21.12.2021. Published 19.01.2023. Bulletin No. 2 / L.E. Gamper, O.V. Sopina. Applicant and patent holder - Joint Stock Company "Concern "Okeanpribor".

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Claims

A passive hydroacoustic system for determining the coordinates of underwater objects in a group, comprising a multi-position passive hydroacoustic station, characterized in that it comprises three collinearly located non-directional receivers, the second of which is a central receiver, wherein the distances between the first and second receivers and between the second and third receivers are known, in each of said receivers there is an analog-to-digital converter (ADC), two processing channels, in each of which a cross-correlation function calculator, a calculator of its modulus and a determiner of the moments of its maxima are connected in series, wherein the outputs of the first and third ADCs are connected to the first inputs of the first and second processing channels, and the output of the second ADC is connected to the second inputs of the first and second processing channels, wherein the first processing channel is configured to determine the moments of the maxima of the cross-correlation function of the signals received by the first and second receivers,and the second processing channel is configured to determine the moments of maxima of the cross-correlation function of signals received by the second and third receivers, the outputs of the processing channels are connected to two inputs of a calculator of pairs of differential delays for underwater objects, configured to form candidate pairs of differential delays by enumerating combinations of the moments of maxima of the cross-correlation functions obtained in the first and second processing channels, and selecting from said candidate pairs of differential delays pairs corresponding to each underwater object in the group, according to the calculated geometric condition of belonging of two differential delays to one underwater object, determined on the basis of calculated relationships for a collinear system of non-directional receivers, the output of the calculator of pairs of differential delays is connected to the input of the calculator of coordinates of underwater objects in the group,designed with the ability to calculate the coordinates of each underwater object in a group based on a pair of differential delays selected for it, wherein the output of the calculator for the coordinates of underwater objects in a group is the output of a passive hydroacoustic system for determining the coordinates of underwater objects in a group.

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