RU2764386C1 - Method for passive determination of the coordinates of a noise-emitting marine object - Google Patents

Abstract

FIELD: acoustics.

SUBSTANCE: area of application: invention relates to the field of hydroacoustic technology and can be used to solve the problems of passive determination of the coordinates of a noise-emitting marine object, namely, the distance and depth, during propagation of hydroacoustic signals in the sea. Substance: the technical result is achieved by refusing the attempt to measure the angles of arrival of rays and building ray trajectories, and solving the problem by examining the points of possible location of the noise-emitting marine object in the space "distance - depth" and taking the coordinates of the point wherein the highest value of the total coefficient of correlation between the array of abscissas of calculated correlation maxima (CM) formed therefor and the arrays of abscissas of the CM of the received signal, obtained by combining the abscissas of the CM found in sets of mutually correlation functions measured for each tier a static multi-tiered spread of directional characteristics in a vertical plane relative to two tiers of signal reception with a maximum signal/interference ratio, as coordinates of the noise-emitting marine object.

EFFECT: increase in the accuracy of determining the coordinates of a noise-emitting marine object.

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Description

The invention relates to the field of hydroacoustic technology and can be used to solve the problems of passively determining the coordinates of an object noisy in the sea, namely, the distance and depth during the propagation of hydroacoustic signals in the sea.

Known methods for passively determining the coordinates (distance and depth) of an object noisy in the sea, which are based on the use of the measured correlation function (CF) of the received acoustic signal. Information about the coordinates of the signal source in the CF is contained in the location on the abscissa (time) axis of narrow-band correlation maxima (CM) due to the interference of correlated source signals that came to the input of the receiving hydroacoustic antenna of the direction-finding station (NSS) along different ray trajectories. Each pair of rays in the CF (with a sufficient signal-to-noise ratio (SIR)) corresponds to one CM with a width equal to the reciprocal of the effective bandwidth of the signal at the antenna input, and a position on the abscissa axis equal to the absolute value of the difference in signal propagation times along the interfering beams [ Mashoshin A.I. Investigation of applicability conditions for the correlation function of a broadband multipath signal for estimating source coordinates. Acoustic journal, 2017, volume 63, no. 3, p. 307-313].

These methods can be divided into two groups depending on the algorithm for calculating the CF.

There are known methods in which to determine the coordinates of an object noisy in the sea, the autocorrelation function (ACF) of the signal at the output of one spatial channel (PC) is calculated [Hassab I.C. Contact Localization and Motion Analysis in the Ocean Environment: a Perspective. - IEEE Journal of Oceanic Engineering, 1983, vol. OE-8, No. 3, pp. 136-147; Quazi A.H., Lerro D.T. Passive localization using time-delay estimates with sensor positional errors. - JASA, 1985, vol. 78, no. 5. pp. 1664-1670; Worthmann B.M., Song H.C., Dowling D.R. High frequency source localization in a shallow ocean sound channel using frequency difference matched field processing. - Journal Acoust. soc. Am., 2015, vol. 138, p. 3549; Mashoshin A.I., Melkanovich B.C. Patent of the Russian Federation No. 2690223 dated August 28, 2018. A method for determining the coordinates of a sea noisy target. IPC G01S 15/00].

The methods of this group are used when the sound signal is received by an antenna that is not developed in the vertical plane (horizontal linear antenna). In this case, a single PC with a wide directivity characteristic with a tunable reception angle in the vertical plane is formed in the receiving path in the vertical plane.

The disadvantage of these methods is the low accuracy of determining the coordinates of an object noisy in the sea. The CMs in the measured ACF are formed by receiving signals from a noisy object from one bearing, propagating along separate ray trajectories having different lengths in the vertical plane. The received signal is formed by beams arriving at different angles due to the vertical refraction of sound during propagation in the aquatic environment.

When a signal is received by a single PC, the directivity characteristic (XH) is oriented to the group of rays that has the highest intensity. In this case, the second group of rays is received by the lateral XN field, as a result of which their intensity (response level) is significantly reduced, and the intensity of the CM in the ACF formed by the combination of these rays will be below the detection threshold, and this CM will be excluded from the analysis.

When working with XN with a high level of the side field, the noise immunity of reception decreases, since through the side field, interference from all directions covered by the side field is added to the received signal to the useful signal.

Thus, when using the signal of a single PC to calculate the ACF, a large amount of information about the received signal is lost and the noise immunity decreases, which leads to a decrease in the accuracy of coordinate estimation.

The second group of methods for determining the coordinates of an object noisy in the sea uses the cross-correlation function (CCF) of the signal at the output of two PCs formed in the receiving path, equally oriented to the signal source in the horizontal direction. In the vertical direction, PCs are focused on the maxima of the spatial spectrum of the received signal [Mashoshin A.I. Investigation of applicability conditions for the correlation function of a broadband multipath signal for estimating source coordinates. - Acoustic magazine, 2017, volume 63, no. 3, p. 307-313].

The closest analogue in terms of the number of common features and tasks to be solved to the proposed invention is a method for passively determining the coordinates of an object noisy in the sea [Baronkin V.M., Galkin O.P., Gladilin A.V., Mikryukov A.V., Popov O. E. Patent of the Russian Federation No. 2602732 dated 06/25/2015. A method for passively determining the coordinates of an object noisy in the sea. IPC G01S 3/80], which is taken as a prototype.

The method according to patent No. 2602732 includes:

- reception of hydroacoustic signals by a spatially developed antenna in the vertical and horizontal planes;

- amplification, filtering in the frequency band, digitization and space-time processing of received signals;

- formation of a static multi-tiered XH fan in a vertical plane;

- cross-correlation processing of at least one pair of beams in the vertical plane;

- selection of CM, measurement of the angles of arrival of the rays forming these CM, measurement of the abscissa of the CM (differences in the propagation times of the rays), as well as the ratio of the average energy values for each pair of rays;

- measurement of the speed of sound in water depending on the depth and roughness of the sea surface;

- according to the measured data and known characteristics of the bottom, the calculation of the signal of a noisy object;

- solution of the equation of hydroacoustics in the passive mode for an object noisy in the sea;

- calculation from the point of location of the receiving antenna of ray trajectories for the measured angles of arrival of rays in the vertical plane for pairs of rays with high values of the maximum of the cross-correlation function and finding the distance and depth of the points of intersection of the trajectories;

- at each point of intersection of the trajectories for all pairs of rays, the calculation of the difference in propagation times and the ratio of energies;

- comparison of measured and calculated propagation time differences and ratios of averaged energy values for all pairs of beams;

- determination of the coordinates of an object noisy in the sea at the intersection point of the ray trajectories, for which the measured and calculated values of the energy ratios and propagation time differences for all pairs of rays turn out to be the closest.

Reception of hydroacoustic signals by an antenna developed in a vertical plane makes it possible to form a static multi-tiered vertical fan KhN (VVKhN), in which part of the PC will be oriented towards the surface, and part towards the bottom. HNs are narrow and selective in terms of reception angles, which provides high noise immunity (a lot of signal and little interference) and, consequently, a large detection range. In addition, the orientation of the PC in space at reception angles in the range from - 20 ° to + 20 ° relative to the horizon allows you to block almost the entire sector for receiving bottom and surface rays in almost all types of hydroacoustic conditions (GAC) and to achieve optimal reception, in terms of noise immunity, each group of rays.

But determining the coordinates of an object noisy in the sea by the prototype method requires a very accurate measurement of the angles of arrival of rays (an accuracy of 5-10 minutes), which can be achieved using a vertical antenna with a height of about 20 - 25 meters, which is practically impossible.

An error in measuring the angles of arrival of rays leads to errors in the calculation of ray trajectories and in determining the points of their intersection, which leads to errors in determining the coordinates of an object noisy in the sea. In addition, in the case of receiving three or more rays and measuring the angles of their arrival with some error, the rays will intersect not at one point, but in some compact areas. The farther the region of intersection of the rays from the receiving antenna, the larger the area of this region [Borodin V.V. Potential accuracy of determining the position of a sound source in a waveguide. Voprosy sudostroeniya. Ser. Acoustics. 1983. Issue. 16. p. 88-103].

Thus, the disadvantage of the prototype method is the low accuracy of determining the coordinates of an object noisy in the sea, associated with the inability to provide high accuracy in measuring the angles of arrival of the rays.

The objective of the invention is to improve the operational characteristics of the direction-finding station.

The technical result of the proposed invention is to increase the accuracy of determining the coordinates of an object noisy in the sea.

To achieve this technical result, a method for passively determining the coordinates of an object noisy in the sea, including the reception of hydroacoustic signals by a spatially developed antenna in the vertical and horizontal planes, amplification, filtering in the frequency band, digitization and spatio-temporal processing of the received signals, the formation of a static multi-tiered XN fan in vertical plane, cross-correlation processing of pairs of rays in the vertical plane, CM extraction, measurement of CM abscissas (differences in ray propagation times), measurement of sound velocity in water depending on the depth and sea surface waves, according to the measured data and known characteristics of the bottom, calculation of the signal of a noisy object , the solution of the hydroacoustics equation in the passive mode for an object noisy in the sea and the determination of its coordinates, new features are introduced, namely: the definition of two angles (tiers) (UN1 and UN2) of signal reception with a maximum signal-to-noise ratio, measurement of the set VKF of the signal of each tier of the vertical fan XN relative to UN1 (VKFUN1 _i ), where i=1, 2 ... N, N - the number of tiers of VVKhN, and relative to UN2 (VKFUN2 _i ) in the analysis interval, detection in each of the measured VKF KM, measuring them abscissa, combining the CM abscissas detected in all measured VKFUN1 _i and VKFUN2 _i in the analysis interval, respectively, into two arrays of abscissas of the CM of the received signal, determining the area of the possible location of an object noisy in the sea in the “distance-depth” space, calculating for each point of this area taking into account the current GAC of the beam structure of the signal at the input of the NLS antenna, calculating for each point of this region the differences in the propagation times of all pairs of rays of the calculated beam structure (the QM abscissas that should be generated by these pairs of rays) and combining them into an array of calculated QM abscissas, calculating for each point of the region of the total correlation coefficient between the array of abscissas of the calculated CMs formed for it and the arrays of abscissas of the CMs at of the received signal, and taking as the coordinates of the object noisy in the sea the coordinates of that point of its possible location in the “distance-depth” space, for which the highest value of the total correlation coefficient was obtained.

The achievement of this technical result is ensured by the fact that the abscissas of the KM can be measured with high accuracy, due to the high resolution of the calculation of the CCF, in contrast to the angles of arrival of the rays, the accuracy of which is limited by the vertical dimensions of the antennas [Borodin V.V. Potential accuracy of determining the position of a sound source in a waveguide. Voprosy sudostroeniya. Ser. Acoustics. 1983. Issue. 16. p. 88-103]. In addition, the values of the abscissas of the calculated CMs at different points of the possible location of an object noisy in the sea in the "distance-depth" space differ significantly, therefore, comparing the abscissas of the CMs calculated for each point with the abscissas of the CMs of the received signal by calculating the correlation coefficient ensures high accuracy in determining coordinates of an object noisy in the sea.

The essence of the invention is illustrated in Fig. 1, which shows a block diagram of signal processing in accordance with the proposed method.

When implementing the method (Fig. 1), processing is carried out at the initial stage in two parallel branches.

The first branch includes sequentially performed operations: detection of a broadband signal of an object noisy in the sea at the output of the NLS receiving path by a static multi-tiered (N is the number of tiers) fan XH, formed in a vertical plane (VVHN) (block 1.1); determination of two angles (tiers) of signal reception with a maximum signal-to-noise ratio (SN1 and SN2) (block 1.2); measurement of a set of VKFs of the signal of each tier of VVKhN relative to UN1 (VKFUN1 _i ) and relative to UN2 (VKFUN2 _i ) in the analysis interval (the total number of measured VKFs is N * 2) (block 1.3); detection in each of the measured VKF KM, measurement of their abscissa (block 1.4); combining the abscissas of the QM detected in all measured VKFUN1 _i and VKFUN2 _i in the analysis interval, respectively, into two arrays of the abscissas of the KM of the received signal (block 1.5).

Performing the above operations ensures the formation of two arrays of abscissas of the KM of the received signal, used for comparison with similar arrays obtained on the basis of the calculated data generated by the blocks of the second branch.

The second branch includes operations: measuring the speed of sound in water depending on the depth and roughness of the sea surface (block 2.1); according to the measured data and known characteristics of the bottom, calculation of the signal of a noisy object, solution of the hydroacoustics equation for an object noisy in the sea (block 2.2); determination of the area of possible location of an object making noise in the sea in the “distance-depth” space (block 2.3); calculation for each point of this area, taking into account the current GAC of the beam structure of the signal at the input of the NLS antenna (block 2.4); calculation for each point of this region of the differences in the propagation times of all pairs of rays of the calculated ray structure (abscissas of the CM that should be generated by these pairs of rays) and their combination into an array of abscissas of the calculated CMs (block 2.5).

Operations of the second branch can be performed once for the current state of hydroacoustic conditions, which determines the beam structure of the signals. The execution of operations of the second branch ensures the formation for each point of the possible location of the object of the array of abscissas of the calculated CM, which are used to compare with the arrays of abscissas of the CM of the received signal, generated by the first branch.

The comparison is performed by sequentially located blocks 3 and 4, performing operations for calculating for each point of the region the total correlation coefficient between the array of abscissas of the calculated CMs generated for it and the arrays of abscissas of the CMs of the received signal (block 3) and, finally, the operation of determining the coordinates of an object noisy in the sea by choosing coordinates of that point of its possible location in the “distance - depth” space, for which the highest value of the total correlation coefficient was obtained (block 4).

The accuracy of determining the coordinates of an object noisy in the sea depends on the accuracy of measuring the parameters of the received signal. The prototype method does not allow for high accuracy in determining the coordinates, as it uses the angles of arrival of the rays, the measurement accuracy of which is several degrees. Errors in measuring the angles of arrival of rays lead to errors in the calculation of ray trajectories. As a result, in the case of receiving two beams, the point of their intersection is shifted by several tens or even hundreds of meters relative to the actual position of the signal source. And in the case of receiving three or more rays, the ray trajectories of all rays do not intersect at one point and only some areas of mutual approach of the ray trajectories can be distinguished, which does not allow using the prototype method to determine the coordinates of an object noisy in the sea.

The proposed method, unlike the prototype method, does not use the angles of arrival of the rays and does not build ray trajectories. Instead, the proposed method enumerates the points of the possible location of the signal source in the "distance-depth" space and compares the array of calculated CM abscissas formed for each point with the arrays of abscissas of the CM of the received signal. Due to the high resolution of the calculation of the CCF, the abscissas of the KM of the received signal can be measured with high accuracy, up to tenths of a millisecond. The abscissas of the calculated CMs at different points in the “distance-depth” space differ significantly, therefore, the implementation of comparing the abscissas of the calculated CMs with the abscissas of the CMs of the received signal by calculating the correlation coefficient ensures the high accuracy of the proposed method for determining the coordinates of an object noisy in the sea.

The proposed method can be implemented using equipment known in hydroacoustics, for example, the hydroacoustic antenna of the PSS is known from [Litvinenko S.L. Patent of the Russian Federation No. 2515133 dated 11/13/2012. Spherical hydroacoustic antenna. IPC G01S 15/00], and the formation of a static multi-tiered fan of directivity characteristics in the vertical plane can be performed according to [Baskin V.V., Grishman G.D., Kazakov M.N., Krinitsky AM, Leonenok B.I., Smaryshev M.D. Patent of the Russian Federation No. 2293449 dated 03.05.2005. A method for forming a frequency-independent directivity characteristic by the working sector of a multi-element hydroacoustic receiving circular antenna. IPC H04R 1/44, G01S 15/02].

When combining the abscissas of the CM found in the sets of measured VCFs, the accuracy of measuring the abscissa of the CM is taken into account. When CMs with similar abscissa values (tenths of a millisecond) are detected in different VKFs, only one value is entered in the array of abscissas of the CM of the received signal.

The determination of the area of possible location of an object noisy in the sea in the “distance-depth” space is performed using the values of the OSP calculated for all possible positions of the object by solving the hydroacoustics equation. The possibility of detecting an object at a particular point in the current GAC is determined by comparing the value of the OSP calculated for this point with the threshold value of the OSP.

The calculation of the beam structure of the signal at the input of the NLS antenna can be performed according to [Avilov K.V., Dobryakov N.A., Popov O.E. A software package for calculating sound fields in a marine environment that is inhomogeneous in depth and propagation path //Acoustics of the ocean. Reports of the X school-seminar acad. L.M. Brekhovsky. M.: GEOS, 2004. S. 27].

The calculation of the correlation coefficient can be performed according to the formula given in [Deza E.I., Deza M.M. Encyclopedic dictionary of distances. Per. from English. M.: Nauka, 2008].

All of the above allows us to consider the problem of the invention solved.

Claims (1)

A method for passively determining the coordinates of an object making noise in the sea, including the reception of hydroacoustic signals by a spatially developed antenna in the vertical and horizontal planes, amplification, filtering in the frequency band, digitization and space-time processing of the received signals, formation of a static multi-tiered fan in the vertical plane (VVKhN) , cross-correlation processing of pairs of beams in the vertical plane, selection of correlation maxima (CM), measurement of the differences in the propagation times of rays in the form of CM abscissas, measurement of the speed of sound in water depending on the depth and waves of the sea surface, according to the measured data and known characteristics of the bottom, signal calculation of a noisy object, solving the equation of hydroacoustics in the passive mode for an object noisy in the sea and determining its coordinates, which differs in that two angles of signal reception with a maximum signal-to-noise ratio (SV1 and SV2) are determined, a set of cross-correlations is measured ionic functions (VKF) of the signal of each tier of the vertical fan XN relative to UN1 (VKFUN1 _i ), where i=1, 2 ... N, N is the number of tiers of VVKhN, and relative to UN2 (VKFUN2 _i ) in the analysis interval, detection is performed in each of the measured VKF KM, measure the values of their abscissas, combine the abscissas of the KM detected in all measured VKFUN1 _i and VKFUN2 _i in the analysis interval, respectively, into two arrays of abscissas of the KM of the received signal, determine the area of the possible location of an object noisy in the sea in the space "distance - depth", for each point of this area, taking into account the current hydroacoustic conditions, the ray structure of the signal at the antenna input is calculated, for each point of this area, the propagation time differences of all pairs of rays of the calculated ray structure are calculated in the form of KM abscissas, which are due to these pairs of rays, and combine them into an array of abscissas calculated KM, calculate for each point of the area the total correlation coefficient between the array absts formed for it iss of calculated KM and arrays of abscissas of KM of the received signal, and the coordinates of an object noisy in the sea are determined by choosing the coordinates of that point of its possible location in the “distance - depth” space, for which the highest value of the total correlation coefficient was obtained.

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