RU2602732C1 - Method for passive determination of coordinates of noisy object in the sea - Google Patents

Abstract

FIELD: acoustics.

SUBSTANCE: invention relates to hydroacoustic equipment and can be used to solve tasks of passive determination of coordinates of a noisy object in the sea, namely, the distance, the depth and the bearing during propagation of hydroacoustic signals in the sea. Technical result is achieved by that the method of passive determination of coordinates of a noisy object in the sea, according to which hydroacoustic field signals of a noisy object in the sea are received, involves frequency-time processing of the received hydroacoustic signals coming at different angles due to vertical refraction of the sound, measuring the sound speed in water depending on the depth and heaving of the sea, calculation by the measured data and known characteristics of the sea bottom of the noisy object signal, solving an equation of hydroacoustics in passive mode for the noisy object in the sea, receiving of the hydroacoustic signals is performed by a spatially developed in the vertical and horizontal planes antenna, those signals are preliminarily amplified and filtered within a frequency band, after which the signals are digitized, space-time processing of the signals is carried out, followed by mutually correlation processing of at least one pair of the signals in the vertical plane, pairs of signals are identified with high values of maximum of the mutual correlation function, measured are angles of arrival of those signals propagating along separate beam paths in the vertical plane, measured is the propagation time difference from the position of maximum of the mutual correlation function on the time axis, as well as measured is the ratio of averaged values of energies for each pair of the signals, then from the point of location of the receiving antenna beam paths are calculated for the measured angles of arrival of the signals in the vertical plane for the pairs of signals with high values of maximum of the mutual correlation function and distances and depths of points of the paths intersection are found, then at each point of the paths intersection for all pairs of the signals propagating along those beam paths calculated are time differences of propagation and the ratio of energies, compared are the measured and the calculated time differences of propagation and ratios of the averaged values of energies for all pairs of the signals, and coordinates of the noisy object in the sea are determined by the point of intersection of the beam paths, for which the most close are the measured and the calculated values of the ratios of energies and the propagation time differences for all pairs of the signals propagating along separate beam paths.

EFFECT: technical result of the invention is higher accuracy of determining coordinates of a noisy object due to elimination of uncertainty when calculating signals delays, as well as measuring ratios of energies of signals propagating along separate beam paths in the vertical plane from one bearing point.

1 cl, 1 dwg

Description

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

Known methods for measuring the distance to a noise source can be divided into the following groups. The first group includes methods based on multi-position receiving and direction finding of the source by several receiving positions (triangulation or goniometric method), or measuring the differences of distances from the source to receiving positions (differential-ranging method), or a combination of these two methods (angular-differential-ranging method) (VV Karavaev, VV Sazonov. The static theory of passive location. M: Radio and communications, 1987, p. 5.4.).

The second group includes methods based on the analysis of the wavefront curvature of a useful signal (see the cited book by V.V. Karavaev, p. 5.1, as well as Underwater Acoustics and Signal Processing, edited by L. Bjorne. M.: Mir 1985, pp. 325-328 and pp. 415-418).

The disadvantage of these methods is the need for either the presence of several substantially spaced receiving positions in space, or the presence of a receiving antenna with a very large aperture - provided that the useful front signal coherence is preserved throughout the entire antenna aperture. The consequences of these factors are the high costs of implementing a range measurement method and / or relatively low measurement accuracy.

There is a method of determining the distance in the noise-detecting mode, based on the reception of sound pressure and vibrational velocity with the subsequent formation of mutual correlation between them, while the dispersion characteristics of the medium during the propagation of sound energy (phase and group velocities) in a limited medium (waveguide) are determined through cross-correlation functions in each channel, and the propagation velocity and delay time thus determined between the sound pressure and the vibrational velocity make it possible the ability to find the desired distance to the radiation source. (Aut. St. USSR No. 544232, IPC G01S 7/52, 1968).

The disadvantage of this method is that it does not have noise immunity with respect to the intrinsic noises of the carrier ship, since when determining the propagation velocities in each of the channels, intrinsic noises during the movement of the ship affect the receiving antenna and there is no detuning from them.

раз, и период интерференции, то есть расстояние между двумя соседними максимумами (Патент РФ №1840066, МПК G01S 7/52, от 13.06.1977 г.).There is a method of determining the distance in the mode of noise detection, providing increased noise immunity by reducing the influence of the intrinsic noise of the carrier ship on determining the distance while maintaining stealth. In this method, two spatial channels are used, they compensate for the delay time between the individual modes in these channels, introducing an artificial delay time in a given band, add the signals, obtaining the interference structure between these signals, and measure the spatial coherence scale when the carrier ship moves, i.e. the distance corresponding to the attenuation of the envelope of the interference structure in

times, and the period of interference, that is, the distance between two adjacent maxima (RF Patent No. 1840066, IPC G01S 7/52, dated 06/13/1977).

The disadvantage of this method is the inability to determine the depth of the noise source. In addition, it is necessary to single out individual modes, which requires very large antennas, whose vertical size is close to the depth of the sea at the receiving point.

There is also a known spectral-frequency method for measuring the distance to a noise source, based on the use of the frequency dependence of spatial attenuation and signal absorption in the marine environment on range. According to this method, a mixture of a noise signal and a noise is received, a frequency spectrum of a mixture of a received noise signal and a noise is measured, a set of predicted spectra of a noise signal is received at the receiving point for a predetermined combination of the range and tilt parameters of the frequency spectrum of the noise signal, the reference spectrum is calculated for each from the predicted spectra of the set, the calculation of the functional correlation between the measured mixture of the received noise signal radiation and interference and each reference spectrum from the set, and the selection of a hypothetical range value is carried out by determining the maximum value of the functional correlation at which the hypothetical range value is accepted as true. The method is operable when objects are located in the near acoustic illumination zone and are unreliable in the far acoustic illumination zone due to the influence of the phenomenon of vertical refraction of sound on the shape of the spectrum, as well as due to the influence of changes in the spatial attenuation, depending on the region of use of the method, and the effect of changes in the spectrum interference depending on the state of the water surface. (RF patent 2128848, IPC from 09.10.97).

A known method of measuring distance, according to which using the autocorrelation function of the signal, you can determine the distance to the target in the passive mode with multipath propagation in the near zone of acoustic illumination. According to this method, the sound signal is received by an antenna, which is assumed to be non-directional in the vertical plane and does not distinguish the angles of arrival of the signal in the vertical plane, but distinguishes the inter-beam delay time of the signal, the broadband signal from the output of the receiving antenna is fed to the correlator, the autocorrelation function of the received multi-beam signal is calculated, and the correlation maximum, measure the inter-beam delay time and calculate the difference in the lengths of the two ray paths from the known speed of sound. The horizontal distance to the target is calculated from the calculated difference in the lengths of the trajectories, the known depth of the sea and the immersion depth of the receiving antenna (B.C. Burdick, “Analysis of hydroacoustic systems. Transl. From English. L .: Sudostroenie, 1988, p. 377).

The disadvantage of this method is that it does not take into account the influence of vertical sound refraction and is extremely dependent on the actual hydroacoustic conditions and the possibility of predicting a fine multipath structure (accurate to the signal phase) and does not allow obtaining information about the speed of noisy objects.

The closest in technical essence and the achieved result to the invention (prototype) is a known method for passively determining the coordinates of an object that is noisy in the sea, by which hydroacoustic signals of the primary field of an object that are noisy in the sea are received, time-frequency processing of the received hydroacoustic signals coming at different angles from - due to vertical refraction of sound, measure the speed of sound in water depending on the depth and waves of the sea surface, according to the measured data and the known character the bottom noise sources calculate the signal of a noisy object, solve the hydroacoustic equation in passive mode for an object that is noisy in the sea, and to determine the distance to objects that are noisy in the sea, signal observation in three spatial channels is used (spatial channels mean receiving a vertical static fan XN in separate lobes), coming from different angles due to vertical refraction of sound. Then, based on the measured speed of sound in water, depending on the depth and waves of the sea surface, as well as on the known characteristics of the bottom and the known characteristics of the receiving system, the object signal in each spatial channel is calculated for several distance values, solving the hydroacoustic equation in the passive mode, and as a result of comparison the measured signal values with the calculated ones decide on the distance and speed and on the presence of several noisy objects in one direction. (Patent RU 2208811, IPC G01S 11/14, dated September 27, 2001).

The disadvantage of the prototype is the low accuracy of determining the coordinates of a noisy object, due to the fact that each spatial channel can receive several signals propagating along separate ray paths, whose interference does not allow to calculate the signal with acceptable accuracy, as well as the uncertainty in the calculation of signal delays caused by the presence of several intersection points of ray paths.

The technical result of the invention is to increase the accuracy of determining the coordinates of a noisy object by eliminating uncertainties in calculating signal delays, as well as measuring the energy ratios of signals propagating along individual ray paths in a vertical plane from one bearing.

The technical result is achieved due to the fact that in the method for passively determining the coordinates of an object that is noisy in the sea, by which hydroacoustic signals are received from the field of an object that is noisy in the sea, time-frequency processing of the received hydroacoustic signals coming at different angles due to vertical sound refraction is carried out, measure the speed of sound in water depending on the depth and the excitement of the sea surface, according to the measured data and the known characteristics of the bottom, calculate the signal of a noisy object, solve the gy acoustics in passive mode for an object that is noisy at sea, receiving hydroacoustic signals is carried out by an antenna spatially developed in the vertical and horizontal planes, these signals are pre-amplified and filtered in the frequency band, after which the signals are digitized, spatial-temporal signal processing is carried out, the correlation processing is performed at least one pair of signals in the vertical plane, select pairs of signals with high values of the maximum of the cross-correlation function, measure The angles of arrival of these signals propagating along individual ray paths in the vertical plane measure the difference in the propagation times by the position of the maximum of the cross-correlation function on the time axis, and also measure the ratio of the averaged energies for each pair of signals, after which the ray paths are calculated from the location of the receiving antenna for the measured angles of arrival of signals in the vertical plane for pairs of signals with high values of the maximum of the cross-correlation function and the distance and depth of the intersection points of the trajectories, then at each intersection of the paths for all pairs of signals propagating along these ray paths, the differences of propagation times and the ratio of energies are calculated, the measured and calculated differences of the propagation times and ratios of the averaged energies for all pairs of signals are compared, and the coordinates of an object noisy in the sea are determined by the point of intersection of the ray paths, for which the measured and calculated values of rel The sum of the energies and differences of the propagation times for all pairs of signals propagating along separate ray paths.

The invention is illustrated by the drawing, which shows an example of ray paths and their intersection points for the measured angles of arrival of one pair of sonar signals. The drawing shows the location of the receiving vertical antenna 1 in the marine waveguide and shows two ray paths 2 and 3, along which signals from a noisy object in the sea come. To determine the location of the object, first find the intersection points of the ray paths 4, 5, 6, 7. Then, special processing of the obtained materials is carried out and the measured and calculated values of the ratios of energies and differences of the times of arrival of the signals are compared. As a result, a decision is made: the object is at point 7.

The method is based on the reception of sonar signals spatially developed in the vertical and horizontal planes of the antenna and is implemented as follows. The signals from the antenna 1 are pre-amplified and filtered in a given frequency band, after which the signals are digitized for further digital signal processing. Then, spatio-temporal processing of the signals is carried out. In addition, they form a static fan of the main lobes of the directivity characteristics (XI), which allows measuring the angles of arrival of signals in the vertical and horizontal planes. The size of the antenna in the horizontal and vertical planes must be such as to provide a given accuracy in determining the angles of arrival of signals in the horizontal (for determining the bearing) and in the vertical (for determining the distance and depth) planes. The size of the antenna at a given frequency and width of each petal XN multilobe antenna can be determined by the formula:

- частота в кГц, α - ширина лепестков ХН в градусах по уровню - 3 дБ.where h is the antenna size in meters,

is the frequency in kHz, α is the width of the CN lobes in degrees at the level of 3 dB.

для заданного диапазона рабочих расстояний:The lower frequency of the band in which the signal is filtered is selected close to the optimal frequency

for a given range of working distances:

- оптимальная частота в кГц, R - расстояние в километрах.Where

is the optimal frequency in kHz, R is the distance in kilometers.

The bandwidth is selected based on the required accuracy of estimating time delays using the cross-correlation function. Since the width of the correlation maximum is approximately equal to the reciprocal of the signal bandwidth, then with the usually required accuracy of estimating the time delays of 0.5-1 ms, the signal bandwidth should be at least 1-2 kHz.

The width of the working CN petals in the vertical plane, as shown by experimental experience, when working at distances up to 10 km should not exceed 2 ÷ 4 ° and 2 ° at long distances. Thus, for example, if a working range of 25 km is specified, then by formula (2) we obtain an estimate for the optimal frequency of 4 kHz, and the antenna height by formula (1) will be 9.4 m. In practice, the maximum vertical size of the antenna is usually limited (no more than 10 m), in this case it is possible to work at frequencies above the optimum frequency to ensure the required width of each lobe XN 2 °.

To determine the coordinates of a noise sound source, it is necessary to receive at least two signals from this source from one bearing propagating along individual ray paths in a vertical plane (see drawing). For further measurements, it is necessary that the signals arrive at different lobes of the static XN fan in a vertical plane. The belonging of these signals to one sound source is determined by calculating the cross-correlation function between pairs of signals. To do this, they perform mutually correlation processing of at least one pair of signals in the vertical plane, select pairs of signals with high values of the maximum of the mutual correlation function, measure the angles of arrival of these signals propagating along individual ray paths in the vertical plane, measure the difference in propagation times from the position of the maximum of the correlation function on time axis. High values of the maximum of the cross-correlation function confirm that these signals belong to the same sound source, as well as the fact of the propagation of these signals along individual ray paths. In the general case, it is permissible for several signals propagating along individual ray paths to enter the lobe, provided that the energy of one of these signals is much larger than the energy of all other signals falling into this lobe, which is why this signal determines the cross-correlation function.

For pairs of signals with high values of the maximum of the cross-correlation function, measurements are made of the angles of arrival of signals in the vertical plane, the difference in propagation times equal to the position of the maximum of the mutual correlation function on the time axis, and the ratio of the averaged energies for each signal pair is measured.

Next, from the location of the receiving antenna, calculate the ray paths for the measured angles of arrival of signals in the vertical plane for pairs of signals with high values of the maximum of the cross-correlation function and find the distances and depths of the points of intersection of the paths, then at each intersection of the paths for all pairs of signals propagating along these beam trajectories, calculate the differences in propagation times and the ratio of energies, compare the measured and calculated differences in the propagation times and rel of the averaged energy values for all pairs of signals, and the coordinates of an object noisy in the sea are determined by the point of intersection of the ray paths, for which the measured and calculated values of the ratios of the energies and differences of propagation times for all pairs of signals propagating along individual ray paths turn out to be closest.

If only one pair of signals is measured, then there are several points of intersection of their ray paths. In this case, the choice of the intersection point corresponding to the true location of the sound source is made by comparing the measured and calculated differences of the propagation times and energy ratios of the pair of signals. The point of intersection of the sound source is the intersection point of the ray paths for which the measured and calculated values of the ratios of the energies and the differences in the propagation times of the pair of signals arriving along separate ray paths turn out to be the closest. That is, the coordinates of the intersection point of the ray paths, which corresponds to the minimum of the function B, calculated by the formula (3), correspond to the coordinates of the object noisy in the sea:

where ΔTe is the measured difference in propagation times for a pair of signals, ΔTc is the calculated difference in propagation times for a pair of signals, Ee is the measured energy ratio for a pair of signals, Ec is the calculated energy ratio for a pair of signals.

If several pairs of signals were found with high values of the maximum of the cross-correlation function, then the coordinates of the only intersection point of their ray paths correspond to the coordinates of an object that is noisy in the sea.

When carrying out the calculations, it is assumed that the depth of the receiving antenna is known, and for the sound propagation path going from the receiver to the previously measured bearing, the following are known: sound velocity profile, bottom topography, acoustic properties of the bottom and sea surface waves, the knowledge of which allows one to calculate radiation paths, times propagation and energy of signals. If it is not possible to measure the sound velocity profile and sea surface swell, they can be taken from climate databases. The bottom topography and acoustic properties of the bottom are extracted from the respective databases.

If there are several sources of noise signals on one bearing, the task of determining their coordinates is solved sequentially. In this case, the main criterion for belonging to a single noise source of signals propagating along individual ray paths in the vertical plane and arriving at different lobes of the vertical static XN fan remains a high value of the maximum of the cross-correlation function of these signals.

Separately, it is worth mentioning that it is possible to measure the motion parameters of the source of noise signals by the proposed method. This is possible because the distance and depth of the signal source are measured. Thus, using successive measurements of the distance and depth of the signal source, it is possible to determine the direction and magnitude of the velocity in the horizontal and vertical plane. Those. the proposed method allows to determine the coordinates and motion parameters of the object, i.e. completely solve the problem of noise detection.

The invention allows to significantly improve the accuracy of determining the coordinates of a noisy object by eliminating uncertainties in calculating signal delays, providing measurements of angles of arrival at the receiving point, as well as measuring differences in propagation times and ratios of average energy values for signals propagating along individual ray paths in the vertical plane with one bearing.

Claims (1)

A method for passively determining the coordinates of an object that is noisy in the sea, by which hydroacoustic signals are received from the field of an object that is noisy in the sea, the time-frequency processing of the received hydroacoustic signals coming at different angles due to vertical refraction of sound is carried out, the speed of sound in water is measured depending on the depth and sea surface swell, according to the measured data and known bottom characteristics, the signal of a noisy object is calculated, the hydroacoustic equation is solved in a passive mode for a volume noisy in the sea kta, characterized in that the reception of hydroacoustic signals is carried out by an antenna spatially developed in the vertical and horizontal planes, these signals are pre-amplified and filtered in the frequency band, after which the signals are digitized, spatial-temporal processing of the signals is carried out, the correlation processing of at least one pair of signals in the vertical plane, pairs of signals with high values of the maximum of the cross-correlation function are distinguished, the angles of arrival of these signals are measured, propagating along individual ray paths in the vertical plane, measure the difference in propagation times by the position of the maximum of the cross-correlation function on the time axis, and also measure the ratio of the average energy values for each pair of signals, after which the ray paths for the measured angles of arrival of the signals in the vertical plane for pairs of signals with high values of the maximum of the cross-correlation function and find the distances and depths of points n intersection of the trajectories, then at each intersection of the trajectories for all pairs of signals propagating along these ray paths, the differences of propagation times and the ratio of energies are calculated, the measured and calculated differences of the propagation times and ratios of the averaged energies for all pairs of signals are compared, and the coordinates of the noise in the sea the object is determined by the point of intersection of the ray paths, for which the measured and calculated values of the ratios of energies and differences of Distribution changed for all pairs of signals propagating along separate beam paths.

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