RU2694270C1 - Device for determining displacement of a surface ship during its noise direction-finding - Google Patents

Abstract

FIELD: hydroacoustics.

SUBSTANCE: invention relates to the field of hydroacoustics and is intended for recognition of sea ships of different displacement by their noise emission. A device comprising a branch of series-connected units between the output of the acoustic receiving antenna for noise direction-finding and the input of the computing device: a band-pass filter, an amplitude detector, a low-pass filter, a spectrum analyzer, characterized in that between the output of the acoustic receiving antenna for noise direction-finding and the input of the computing device, at least two new branches of series-connected units are inserted in parallel: a band-pass filter, an amplitude detector, a low-pass filter, a spectrum analyzer, wherein the parallel branches of the same-type units differ in the band-pass filtering frequency range, and the computing device comprises a series-connected multi-channel fluctuation period selection unit and a ship displacement determining unit.

EFFECT: high noise-immunity and possibility of determining the displacement of a surface ship at any unknown frequency range of the noise signal, in which low-frequency fluctuations are observed, which are caused by rolling at sea surface disturbance.

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Description

The invention relates to the field of hydro-acoustics and is intended for the recognition of marine vessels of different displacement due to their noise emission.

It is known [1, 2] that the rolling of a ship when it is dynamically influenced by wind waves has two main coordinate components: the side and keel. In general, the rolling process is a random process with a spectrum described by the Rayleigh curve with a pronounced maximum. This maximum corresponds to the main period of the ship’s motion, which depends on its displacement [3].

The rolling of surface ships leads to the formation of low-frequency fluctuations of the noise signal received by hydroacoustic means [4]. The nature of these fluctuations in simple models is considered quasi-harmonic, similar to the spectrum of pitching. Therefore, the average value of the period of fluctuations of the noise emission signal will correspond to the basic period of the ship’s motion, which, in turn, is due to its displacement. On this phenomenon are based methods and devices for determining the displacement of surface ships during their noise-finding.

The known method [5], in which the low-frequency oscillations of the noise signal of the ship are measured and the period of the low-frequency fluctuations of the signal is calculated as the time interval between two adjacent amplitude maxima. There are two drawbacks to this method. Firstly, the received sonar noise contains a mixture of the useful signal and interference, which distorts the calculated period of signal fluctuations. And secondly, as a consequence of the first drawback, the procedure for determining the period cannot be automated.

Known patent [6] on "Method for determining the displacement of a surface ship when it is sounding", which describes a device for determining the displacement of a surface ship with a previously unknown bandwidth of low-frequency fluctuations of its signal.

The closest analogue in terms of the composition of the blocks and the tasks to be solved for the invention is the device [7], which is taken as a prototype.

The device prototype contains the following series-connected blocks:

acoustic receiving antenna;

bandpass filter;

amplitude detector;

low frequency filter;

spectrum analyzer;

computing device.

The device filters the noise signal in the common frequency band of the receiving path, performs amplitude detection and filtering in the low frequency band characteristic of the ship’s pitching frequencies in order to detect low-frequency fluctuations of the noise signal. Then, the spectrum of low-frequency fluctuations is calculated and analyzed to determine the period of fluctuations. On the basis of the fluctuation period, the displacement of the surface ship is determined in the computing device.

The devices [6] and [7] have a common drawback associated with the low level of knowledge of the process of the formation of low-frequency signal fluctuations. According to [7], in which the theoretical analysis of the signal-to-noise ratio at the output of the bandpass filter was carried out, the entire frequency band of the main path should be used as the frequency band of the noise signal, which further detects low-frequency fluctuations. However, more recent field studies have shown [8] that low-frequency fluctuations are not always inherent in the entire frequency band of the received signal, but can occur only in a certain limited frequency range of the noise signal. In this case, the selection of fluctuations using the entire frequency band leads to a weakening of the effect of signal fluctuations, and in the limit to the impossibility to determine the period of fluctuations and, consequently, the displacement of the ship.

The task of the claimed device is to determine the displacement of surface ships at any previously unknown frequency range of the noise signal, in which low-frequency fluctuations occur due to rolling on the waves of the sea surface.

To solve this task, the first branch of the blocks in the form of serially connected bandpass filter, amplitude detector, low frequency filter and spectrum analyzer is introduced into the device for determining the displacement of a surface ship during its direction finding noise, which contains new signs, namely between the output of the acoustic receiving antenna and the input of the computing device parallel to the first branch of the blocks are connected at least two new ones in block meshes containing each serially connected bandpass filter, amplitude detector, low frequency filter and spectrum analyzer, while the bandpass filters of all parallel branches of the blocks, including the first one, have different bandwidth filtering frequency ranges, and the computing device contains serially connected multi-channel fluctuation period selection block, the input of which is the input of the computing device, and the unit for determining the displacement of the ship.

The best result is achieved if the lower frequency of the bandpass filter of the first branch is equal to the initial frequency of the receiving path, and the upper frequency of the bandpass filter of the last branch is equal to the final frequency of the receive path.

The technical result of the invention is to improve noise immunity and ensure the possibility of determining the displacement of a surface ship at any previously unknown frequency range of the noise signal, in which low-frequency fluctuations due to rolling on the waves of the sea surface occur.

We show the possibility of achieving the specified technical result.

Experimental studies conducted in [8] showed that in different hydrologic-acoustic conditions of observation low-frequency fluctuations can occur in different limited frequency ranges of the noise signal, the dependence of their location on the frequency axis has not yet been clarified. In this case, the use of detection of fluctuations of the entire frequency band of the receiving path leads to a decrease in the power of fluctuations recorded at the output of the spectrum analyzer. And, on the contrary, the use of a limited frequency range of the noise signal, in which fluctuations appear, leads to an increase in their power at the output of the spectrum analyzer [8].

The claimed device differs from the prototype device in that it contains not one but several of the same type of parallel signal processing branches, starting with a bandpass filter and ending with a spectrum analyzer. In this case, parallel branches of the same type of blocks differ in the frequency range of bandpass filtering. This will allow to use for selection of low-frequency fluctuations not the entire frequency band of the receiving path, but a set of limited areas. For that of the processing branches, for which the bandpass filter range is close to the limited frequency range of the noise signal, in which fluctuations occur under these conditions, the maximum possible low-frequency fluctuation power will be recorded at the output of the spectrum analyzer. At the same time, the presence of several parallel processing branches, differing in the frequency range of bandpass filtering, will allow simultaneously analyzing the entire frequency band of the receiving path for the presence of low-frequency fluctuations in any of the previously unknown regions of it.

All parallel signal processing branches are connected to the computing device of the claimed device, and a block for selecting the period of fluctuations on the set of branches is added to the computing device itself, which means choosing the best result. This will allow analyzing the result of signal processing on a set of branches, choosing the result obtained at the maximum power of low-frequency fluctuations. Thus, the noise immunity of the device will be increased in any case, in whatever frequency range of the noise signal the low-frequency fluctuations appear.

The invention is illustrated FIG. 1, which shows a block diagram of a device for determining the displacement of a surface ship when it is sounding.

The claimed device (Fig. 1) contains between the noise-finding antenna 1 and the computing device 6 at least three parallel-connected branches, in which one-type blocks are sequentially connected: a band-pass filter (blocks 2.1, 2.2, ... 2.n), an amplitude detector (blocks 3.1, 3.2, ... 3.n), low-frequency filter (blocks 4.1, 4.2, ... 4.n), spectrum analyzer (blocks 5.1, 5.2, ... 5.n). Computing device 6 contains two series-connected blocks: a block for selecting the period of fluctuations 6.1 and a block for determining the displacement of a ship 6.1. At the same time, block 6.1 has n inputs, each of which is connected to the outputs of spectrum analyzers 5.1, 5.2, ... 5.n.

Antenna noise-finding is known from [9], while the antenna modules can be performed according to [10] with integrated analog-to-digital conversion devices. Then the tasks solved in the remaining blocks can be implemented in modules of programmable signal processors and in modules of the universal part of the digital computing complex [11]. The number of parallel-connected branches of the same type is determined by the total bandwidth of the receiving path of the direction finding system. It is known [12] that to ensure acceptable noise immunity in each individual signal processing channel, it is necessary to use a bandwidth of at least one octave. Then, with the standard frequency band of the receiving path of the direction finding noise of 3-4 octaves, it is necessary in the claimed device to form 3-4 parallel branches of the same type blocks with different frequency bands of bandpass filtering. The relative bandwidth of all bandpass filters is the same and equals one octave. The lower frequency of the bandpass filter of the first branch is equal to the initial frequency of the receiving path. The upper frequency of the bandpass filter of the last branch is equal to the final frequency of the receiving path. The average frequencies of the bandpass filters of all branches are evenly distributed in the frequency range of the receiving path. With a wider frequency band of the receiving path, the number of branches of the same type blocks can be increased without changing the resulting effect of the device.

In the dynamics of the device operation, the noise signal of the ship, received by antenna 1 and translated into a digital code, simultaneously enters all n parallel processing branches.

In blocks 2.1-2.n, bandpass filtering of the signal [13] is performed with filters with a bandwidth of one octave. The presence of a set of 2.1-2.n filters allows, on the one hand, to cover the entire frequency band of the receiving path of the noise-finding and, on the other hand, to further isolate low-frequency signal fluctuations independently in different regions of the full band. Further, the filtered signals in each branch independently arrive each in its amplitude detector 3.1-3.n. All blocks 3.1-3.n are absolutely identical. They can be either quadratic or linear detection to highlight the fluctuations of the signal in amplitude. According to [7], the type of detection is not critical. Further, the signals in each branch independently arrive each into its low-pass filter 4.1-4.n, implemented according to [13], whose task is to suppress frequencies exceeding the upper useful frequency of signal fluctuations in the ship’s rolling range on an agitated surface. Further, the signals in each branch independently arrive each into its spectrum analyzer 5.1-5.n. Spectrum analyzers calculate the energy spectrum in the range of signal fluctuations, detect the presence of signal fluctuations due to rolling, and determine their period. Spectrum calculation is implemented according to [13] by the method of fast Fourier transform. The procedures of the method [6] can be used to detect the presence of signal fluctuations and determine their period, allowing to additionally determine the signal-to-noise ratio and increase the noise immunity of detecting fluctuations at any previously unknown width of the fluctuation spectrum. Then the periods of fluctuations and the corresponding signal-to-noise ratio, each obtained for its octave noise signal frequency band, simultaneously arrive at the computing device 6.

The computing device contains two series-connected blocks: a multichannel block for selecting the period of fluctuations and a block for determining the displacement of a ship.

The choice of the period of fluctuations is carried out on the basis of a comparison between the signal-to-noise ratio, which correspond to the periods obtained in parallel signal processing branches 2.1-5.1 - 2.n-5.n. Select the period that corresponds to the maximum value of the signal-to-interference ratio.

In the last block of the device, the displacement of the surface ship is determined from the tabular dependence of the displacement on the period of signal fluctuations caused by the roll [3].

All of the above allows us to consider the problem of the invention solved. A device for determining the displacement of a surface ship when it is sounding is proposed, which has increased noise immunity, which can be used as part of shipborne sonar observation devices for detecting sea vessels of different displacements by their noise emission.

INFORMATION SOURCES

1. Boroday I.K. and others. Applied problems of the dynamics of ships in the waves. P .: Shipbuilding, 1989

2. Boroday I.K., Netsvetaev Yu.A. Seaworthiness of vessels. P .: Shipbuilding, 1982

3. Sizov V.G. Theory of the ship: Training. benefit / Odessa. national Marine Acad. - Odessa: FENZHS, 2003. 284 p.

4. Kudryavtsev, A.A., Luginets, K.P., Mashoshin, A.I. On the amplitude modulation of underwater noise emission of civilian courts // Acoustic Journal. 2003. Vol. 49. No. 2 P. 224-228

5. Biryukova E.S., Shengelia M.V. Application of the Fisher criterion for testing statistical hypotheses in one of the tasks of the classification of objects // Proceedings of the NTK MS OAO Concern Okepribor. 2009. p. 163-164

6. Konson A.D., Volkova A.A. The patent of the Russian Federation №2645013 from 02.15.2018. The method for determining the displacement of a surface ship when it is sounding. IPC G01S 3/80

7. Mashoshin A.I. Optimization of the device for detecting and measuring the parameters of the amplitude modulation of the underwater noise emission of sea vessels. Acoustic Journal. 2013. volume 59. №3. Pp. 347-353

8. Konson A.D., Volkova A.A. Spectral properties of fluctuations of underwater noise emission of sea vessels / Sb. report XIV All Russian. conf. "Applied technologies of hydroacoustics and hydrophysics". SPb .: SPbNTS RAS. 2018

9. Litvinenko S.L. RF patent №2515133 dated 05/10/2014 Spherical sonar antenna. IPC G01S 15/00

10. Smaryshev, MD, Chernyakhovsky, A.E., Ivanov, A.M., Shatokhin, A.V., Seleznev, I.A., Nikandrov, V.A., Malyarov, K.V., Barsukov, Yu.V. The patent of the Russian Federation №2539819 from 01/27/2015. Antenna module with digital output. IPC H04R 1/44

11. Betelin V.B., Kapustin G.I., Kokurin V.A., Koryakin Yu.A., Liss A.R., Nemytov A.I., Pershin A.S., Ryzhikov A.V., Chelpanov A.V., Shalin S.A. The patent of the Russian Federation №2207620 from 10.03.2003. Digital computing system for processing signals in sonar systems. IPC G06F 15/16, G01S 15/88

12. Volkova A.A., Konson A.D., Nikulin M.N. Estimation of the distance to the source of the noise signal by the method of “optimal frequencies” using bandpass filters // Hydroacoustics. 2015. Vol. 22 (2). Pp. 43-52

13. Rabiner P., Gould B. Theory and application of digital signal processing. Per. from English M .: Mir, 1978

Claims (2)

1. A device for determining the displacement of a surface ship when it is sounding, in which between the output of the acoustic receiving antenna and the input of the computing device is included the first branch of the blocks in the form of serially connected bandpass filter, amplitude detector, low-frequency filter and spectrum analyzer, characterized in that between the output of the acoustic receiver The antenna and the input of the computing device parallel to the first branch of the blocks are connected to at least two new branches of the blocks, each containing connected bandpass filter, amplitude detector, low frequency filter and spectrum analyzer, while the bandpass filters of all parallel branches of the blocks, including the first, have different frequency bands of bandpass filtering, and the computing device contains series-connected multi-channel fluctuation period selection, the input of which is a computational device, and the unit determining the displacement of the ship. 2. The device according to claim 1, characterized in that the lower frequency of the bandpass filter of the first branch is equal to the initial frequency of the receiving path, and the upper frequency of the bandpass filter of the last branch is equal to the final frequency of the receive path.

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