RU2242021C2 - Sonar method for detection of underwater objects moving at low radial velocity in controlled water area and sonar circular scanning station realizing this method - Google Patents

Abstract

FIELD: hydroacoustics, applicable for detection of underwater objects moving at a low radial velocity in the controlled water area.

SUBSTANCE: the method is based on successive irradiation of water space by hydroacoustic signals in different directions, reception of echo signals from fixed objects and objects moving at a low radial velocity, demodulation, filtering and display of the received echo signals on the screen of the two-coordinate indicator. At the same time K "radiation-reception" cycles are accomplished in m directions, all the received echo signals discredited in l elements of the distance are memorized, displayed on the screen of the two-coordinate indicator in the form of luminous marks so that in each of m directions successively K times l elements of the distance are displayed. The decision of detection of the object by the m-th direction is taken by appearance on the respective section of the indicator screen of a path formed by the luminous marks of the echo signal, obtained in K "radiation-reception" cycles. The detected objects moving at a low radial velocity and the fixed objects are classified by the presence of inclination of the luminous marks of the echo signals from the moving objects determined by variation of the distance to them and absence of inclination of the luminous marks of the echo signals from the fixed objects. The sonar station has a hydroacoustic cylindrical antenna of piezoelectric transducers combined in n identical bands, "radiation-reception" selector switch, generating device, reception channel. Each band is turned about its axis relative to the adjacent band so that the acoustic axis of the directional pattern of each i-th transducer of one band is shifted relative to the acoustic axis of the directional pattern of the i-th transducer of the adjacent band through angle φ=2Π/mn.

EFFECT: provided detection and classification of underwater objects moving at a low radial velocity, as well as reduced loss of power at radiation of hydroacoustic signals and enhanced signal-to-noise ratio at reception of reflected signals in a circular scanning sonar.

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Description

The invention relates to the field of hydroacoustics and can be used to detect underwater objects moving at a low radial speed in a controlled area: underwater swimmers, marine animals, large fish.

Known sonar methods for detecting and selecting moving objects based on the emission of pulsed signals, receiving reflected signals, spectral analysis of received signals, measuring the Doppler shift of the frequency components in the received signals, deciding whether to detect a moving object when the useful signal exceeds a predetermined threshold [1, 2 ]. At low radial velocities of objects, these methods are not effective due to the difficulties of isolating the Doppler shift of the spectrum of the useful signal against the background of fluctuating spectra of signals reflected from local and distributed stationary objects at the bottom and in the water area of the water area.

A known method according to the patent [3]. The essence of the method is to determine the phase difference of the emitted and reflected signals using correlation processing and taking it into account when measuring radial velocities of objects using Doppler parameters on a multiplicative scale. However, under conditions of observation of objects moving at low speed near the bottom, in addition to noise interference, the reverberation also acts on the receiver, which is distributed signals from stationary objects, while the correlation will be high for all reflecting objects and highlight the object moving at low speed against the background of interference it will be almost impossible.

Closest to the proposed invention is the method according to the patent [4]. The essence of the method lies in the fact that sequential irradiation is carried out using a sonar emitter of various zones of the controlled area with modulated radiation with carrier amplitudes below the level of sea noise, the reception of acoustic signals reflected from an underwater object by a sonar receiver, demodulation of the received signal, temporary filtering, followed by location , course and speed of the object according to the parameters of the received signal. However, the noise immunity of the method is determined by a single detection and in the conditions of reverberation noise may be low.

The objective of the invention is to increase the reliability of detection of underwater objects moving with a small radial speed, in the conditions of low signal to noise ratios when exposed to noise and reverberation noise, and enabling the HFS operator to distinguish between detected moving and stationary objects.

To solve the problem in a sonar method for detecting underwater objects moving at low radial speed, based on sequential irradiation of the water space with hydroacoustic signals in various directions, receiving echo signals from stationary and moving at low radial speed objects, demodulating, filtering and displaying a two-coordinate indicator on the screen received echo signals, new features have been introduced, namely: simultaneously in m directions, k cycles “radiation-n by ”, remember all received echoes, discretized by l distance elements, display them on the screen of the two-coordinate indicator in the form of brightness marks so that in each of m directions l distance elements are displayed k times k times, with the number of simultaneously displayed in each of m directions elements after the completion of the k-th cycle and with further irradiation of the water space is kept equal to kl, removing l elements of the initial cycle, shifting the remaining elements and displaying l el elements of the last cycle, the decision to detect an object in the mth direction is made by the appearance on the corresponding section of the screen of the indicator of the path formed by the brightness marks of the echo signals received in k cycles “radiation-reception”, the classification of detected moving with a small radial speed and stationary objects is carried out according the presence of a slope of the paths of brightness marks of echo signals from moving objects, due to a change in the distance to them and the absence of a slope of the paths of brightness marks of echo signals from motionless s objects.

The technical result from the use of the method is the ability to detect and classify underwater objects moving with a low radial speed against the background of stationary objects of the water layer and the bottom. This result is based on the fact that stationary objects in the water layer and bottom elements that form the bottom reverb form a stationary image on the indicator screen in the form of horizontal paths, while all moving objects (even with a low radial speed) form inclined paths. The slope of the path depends on the magnitude and direction of the change in the distance to the object for k cycles of “radiation-reception”.

Closest to the claimed invention, an analogue that is selected as a prototype of a device that implements the inventive method is a fish echo sonar “Eel” having a simultaneous all-round viewing mode [5, p. 140 ... 153].

The composition of the sonar includes:

- transceiving sonar antenna, consisting of omnidirectional piezoelectric transducers, combined in n identical belts;

- switch “radiation-reception”;

- generator device;

- a reception path, including equipment for processing received signals and a control panel with an electronic indicator.

In the “Eel” sonar in the mode of simultaneous all-round viewing, the antenna non-directionally emits acoustic sounding signals in the horizontal plane, that is, in one package the sonar irradiates the entire underwater space surrounding the vessel. At the same time, a pulse with a power of up to 7.5 kW is generated in the generator device, which is transmitted through the “radiation-reception” switch to the antenna, where electric energy is converted into acoustic energy and radiated into water.

In receive mode, an electronic circular scanning of the radiation pattern (MD) in the horizontal plane with a high speed is carried out. The slope of the beam varies electronically by switching the antenna belts in the radiation-receive switch. Object detection is performed by the operator according to the current information received in each radiation-reception cycle, without accumulating it on the screen of a two-coordinate electronic indicator.

The disadvantages of this sonar include:

- inefficient use of energy consumed in the radiation mode due to non-directional exposure of the surrounding space;

- lack of accumulation of information on the indicator screen;

- loss of information about echo signals from objects when they are received on a radiation pattern rotating at a high frequency in the horizontal plane.

The objective of the claimed device is to eliminate the indicated disadvantages of the prototype sonar and to achieve the following technical results: reduction of energy losses during radiation and increase of the signal / noise ratio in the reception mode, as well as increase in the reliability of detection and classification of underwater moving objects.

In order to achieve the indicated technical results in a circular scanning sonar (SFS) for detecting underwater moving objects containing a hydroacoustic cylindrical antenna of piezoelectric transducers combined in n identical belts, an “radiation-reception” switch, a generator device, a receiving path, including a received processing device signals and a control panel with an electronic indicator, while the control inputs of the generator device, the radiation-reception switch and The processing properties of the received signals are connected to the corresponding control outputs of the control panel, new features are introduced, namely, all the piezoelectric transducers of the hydroacoustic cylindrical antenna are directional, and each belt contains m piezoelectric transducers located uniformly around the circumference of the belt with an interval of 2πR / m and connected by radiation in parallel, each belt is rotated around its axis relative to the neighboring belt so that the acoustic axis of the radiation pattern to each i-th transducer of one belt is offset relative to the acoustic axis of the radiation pattern of the i-th transducer of the neighboring belt by an angle φ = 2π / mn, the input of each belt through the radiation-receive switch made by n-position is connected to the output of the generator during radiation, and when receiving, the outputs of each of the m converters of each belt are connected through an n-position “radiation-reception” switch, made in the m-channel reception mode, with the corresponding information inputs of the received signal processing device, in also filled with m-channel, m information outputs of the processing device are connected to the corresponding m inputs of a memory block containing k memory cells for storing on each of m channels in n positions of the “radiation-reception” switch the received echo signals discretized by l elements distance, kmn outputs of the memory unit are connected to the corresponding kmn inputs of a two-coordinate electronic indicator, made kmn-channel.

In the transition to a new element base, the receiving path, including a device for processing received signals, a memory unit and a control panel with an electronic indicator, is made on digital computer technology.

Thus, the claimed technical results were achieved by replacing the non-directional radiation and receiving the echo signals with a rotating radiation pattern with parallel-serial radiation and receiving echo signals with a fan of static radiation paths, as well as accumulating and presenting information about the detected underwater objects on a multi-channel electronic indicator.

The invention is illustrated in figure 1 and figure 2, where figure 1 shows a block diagram of a radar station circular view for detecting underwater moving objects that implements the proposed method, and figure 2 shows a representation of the paths from moving and stationary objects on an electronic screen indicator in Cartesian coordinates.

The proposed SFS contains a hydroacoustic cylindrical antenna 1 of piezoelectric transducers combined into identical belts, the inputs of the belts in the radiation mode are connected through the n-position switch “radiation-reception” 3 with the output of the generator device 2, and in the reception mode, the outputs of the antenna belts 1 through the same The n-position switch “radiation-reception” 3 is connected to the information inputs of the reception path 4, including a device for processing received signals 5, a memory unit 6, a control panel 7 with electronic ind katorom 8.

The hydroacoustic antenna 1 is designed to convert electrical signals supplied to it in the radiation mode from the generator device into acoustic signals, and to convert the received acoustic signals into electrical ones, which are supplied to the receiving path. In the proposed FPP, the hydroacoustic antenna is structurally a cylinder assembled from six (n) belts, around which eight (m) piezoelectric transducers are evenly spaced. Each of these receive-emitting transducers, which are directional, forms a separate spatial channel. The beam width of each piezoelectric transducer at the operating frequency is 7.5 ° horizontally and 20 ° vertically.

The angle between the acoustic axes of the eight DNs of each belt is 45 °, while each belt is rotated around its axis relative to the neighboring belt at an angle of 7.5 °. Thus, the hydroacoustic antenna forms in the circular horizontal sector a fan of 48 (mn) overlapping static levels of 0.7.

The realized DN width in the vertical plane provides an overview of the water layer to a predetermined depth, which eliminates the need to change the angle of inclination of the DN.

Generator device 2 is designed to generate, amplify and control the power of the probe pulses in accordance with the control signals coming from the control panel 7, and alternately supplying amplified electrical pulses to the antenna belts.

A description of the composition of the generator device is given in [5, p. 153], while in our example a capacitive storage with a partial discharge is used as an energy source, a description of which is known, for example, from [6, p. 240 ... 247].

The switch "radiation-reception" 3 in accordance with the control signals coming from the control panel 7, makes an alternate connection of each belt of the hydroacoustic antenna 1 to the output of the generating device 2 in the radiation mode and to the eight inputs of the device for processing the received signals 5 in the receiving mode. The device "radiation-reception" is known, for example, from [2, p. 77 ... 80].

The receiving path 4 is intended for the time-frequency processing of signals received in the receiving mode from the hydroacoustic antenna 1, accumulating and displaying them on the electronic indicator 8. The device of the receiving path of the sonar circular viewing station is known and described, for example, in [2, p. 99. ..132].

When translating the element base of the reception path to digital computer technology, the analog-to-digital conversion of signals, their input into a digital computer and digital processing is carried out in accordance with the principles described in [7, p. 32 ... 42] and [8, p. 389. ..436].

The device for processing received signals 5 is intended for amplification, frequency conversion of the spectrum and filtering of received signals. The principles and devices implementing this processing are known, for example, from [2, p. 112 ... 115].

The memory unit 6 introduced into the receiving path 4, which is the main memory of the digital computer, is designed to accumulate echo signals during parallel reception through eight spatial channels generated by the piezoelectric transducers of each antenna belt 1, in six positions of the radiation-reception switch 3, which switches each antenna belt at the reception after each radiation cycle. In this case, for the accumulation of echo signals discretized by 500 (l) distance elements, fifteen (k) cells are allocated for each of the 48 spatial channels in the memory block. The outputs of each of 720 (kmn) cells of the memory unit 6 are connected to the corresponding inputs of the electronic indicator 8.

The electronic circular viewing indicator 8 is a two-coordinate indicator with a brightness mark and serves to display information coming from the memory unit 6, as well as to classify, determine the distance and the course angle of all objects displayed on it that are within the range of the GLS.

The image of the environment on the electronic indicator at the choice of the operator can be presented in Cartesian and polar coordinates. The principles of constructing an electronic indicator of a circular review are known, for example, from [2, p. 130 ... 133]. In the considered example, the 720-channel electronic circular viewing indicator provides the display of the detected object with individual brightness marks corresponding to each echo signal arriving in each of the 15 radiation-receive cycles for each of the 48 spatial channels.

To display the echo marks on the distance scale in the electronic HFS indicator for each of 720 channels located along the abscissa axis, 500 (l) resolution elements are implemented along the ordinate axis.

Using the proposed drug, the claimed method is implemented as follows.

After applying power to the OUDS on the control panel 7, the parameters of the emitted hydroacoustic signals are set: type, duration, repetition period, power. Then they begin to irradiate the water space of the controlled water area, for which, from the generator device 2, an electric pulse with an operating frequency of filling is supplied to the sonar antenna 1 through a six-position “radiation-reception” switch, where it is converted into an acoustic signal emitted into the aqueous medium.

In each “emission-reception” cycle, the signal is emitted simultaneously by eight piezoelectric transducers of each of the six antenna belts 1, which are switched from the radiation mode to the reception mode using the “radiation-reception” switch 3. If there are reflecting underwater objects in the field of view of the HFS, echo signals from they are received by the same eight piezoelectric transducers that convert them into electrical signals. From the outputs of the piezoelectric transducers, the signals through the switch “radiation-reception” 3 are fed to eight inputs of the device for processing the received signals 5. In it, the received signals are amplified, converted in frequency, filtered, digitized and fed to eight inputs of the memory unit 6.

After storing the received and processed implementations of the echo signals in eight corresponding cells of the memory unit 6, the next antenna belt 1 is connected to the output of the generator device 2 through the radiation-reception switch 3 and a new radiation-reception cycle is started. As a result of the fifteen-fold sequential switching of the six antenna belts 1 from radiation to reception, 720 realizations of echo signals, discretized by 500 distance elements, are accumulated in the cells of memory unit 6.

To display information on each of the 48 observation directions corresponding to the course angles in the sector 0 ° ± 180 °, 48 vertical stripes consisting of fifteen lines are assigned to the electronic indicator screen 8. In this case, the echo signal reflected from the object is indicated on the line by a brightness mark (dot).

A complete frame of information is collected on the screen of the electronic indicator 8 in 48 directions sequentially for fifteen cycles of “radiation-reception”, further updating of the information is carried out in the current mode: after each new cycle “radiation-reception”, information of the initial cycle is deleted in each of the 48 stripes of the screen , the information remaining on the screen is shifted and the information obtained in the last cycle is displayed on the vacant space, and so on throughout the entire observation process.

As a result, with a parallel-sequential circular survey of the space implemented in the claimed invention, the simultaneous detection of all moving and stationary reflecting objects and the display of echo signals from them on the screen of the electronic indicator 8 in the form of extended groups (tracks) of brightness marks are provided. Traces are formed from brightness marks corresponding to echo signals from objects accumulated in the memory block during fifteen cycles of “radiation-reception” and displayed on the screen of indicator 8 in accordance with the directions to the objects and the distances to them.

Figure 2 shows that the paths from stationary objects of type “b” have a horizontal position, and the paths from moving objects of type “a” have a slope, the nature of which depends on the magnitude and direction of the change in distance to the object. This will allow the FPP operator to more accurately detect and classify moving and stationary objects in a controlled area. In this case, due to the mode of the current update of information during subsequent cycles “radiation-reception”, changes in the location of moving underwater objects will be displayed by the corresponding movement of their traces on the screen of electronic indicator 8.

Thus, the task set in the claimed invention has been fulfilled since, in comparison with the prototypes in the proposed method and the FPP, which implements the method, reliable parallel detection and reliable classification of moving objects is ensured by parallel-sequential viewing using a fan of static radiation patterns, as well as radiation power and power consumption are reduced two times.

Sources of information

1. Burdick B.C. Analysis of sonar systems. L .: Shipbuilding, 1988, p. 346-348.

2. Kolchedantsev A.S. Hydroacoustic stations. L .: Shipbuilding, 1982, p. 39-41, 105-107.

3. Patent of Russia No. 2058033, cl. G 01 S 15/00.

4. Patent of Russia No. 2150123, cl. G 01 S 15/04.

5. Tikunov A.I. Search instruments and systems. L .: Shipbuilding, 1989.

6. Roginsky V.Yu. Power supply of radio devices. L .: Energy, 1970.

7. Rokotov S.P., Titov M.S. Processing sonar information on ship digital computers. L .: Shipbuilding, 1979.

8. The use of digital signal processing. / Ed. E. Oppenheim. M .: Mir, 1980.

Claims (3)

1. A sonar method for detecting underwater objects moving with a small radial speed in a controlled area, based on irradiating the water space in m directions with hydroacoustic signals, receiving echo signals from stationary and moving objects with a low radial speed, demodulating, filtering and displaying on the screen a two-coordinate indicator accepted echo signals, characterized in that at the same time in m directions carry out k cycles of "radiation-reception", remember all the received echo signals, dis reticulated by l distance elements, display them on the screen of the two-coordinate indicator in the form of brightness marks so that l distance elements are displayed k times in each of m directions, the number of elements simultaneously displayed in each of m directions after the kth cycle is completed and further irradiation of the water space, keep equal to kl, removing l elements of the initial cycle, shifting the remaining elements and display the l elements of the last cycle in the vacated space, the decision to detect of an object in the mth direction is taken by the appearance on the corresponding section of the screen of the track indicator formed by the brightness marks of the echo signals received in k cycles of "radiation-reception", the classification of detected moving at a low radial speed and stationary objects is carried out by the presence of the slope of the tracks of the brightness marks of echo signals from moving objects, due to a change in the distance to them and the lack of slope of the paths of brightness marks of echo signals from stationary objects. 2. Surveillance sonar for detecting underwater objects moving at low radial speed in a controlled area, containing a hydroacoustic cylindrical antenna of piezoelectric transducers combined in n identical zones, a radiation-receive switch, a generator device, a receiving path, including a received processing device signals and a control panel with an electronic indicator, while the control inputs of the generating device, the radiation-reception switch and the image the bumps of the received signals are connected to the corresponding control outputs of the control panel, characterized in that all the piezoelectric transducers of the hydroacoustic cylindrical antenna are directional, each belt containing m piezoelectric transducers arranged uniformly around the circumference of the belt with an interval of 2πR / m and connected in parallel, each the belt is rotated around its axis relative to the neighboring belt so that the acoustic axis of the radiation pattern of each i-th transform The fir-tree of one belt is offset relative to the acoustic axis of the radiation pattern of the i-th transducer of the neighboring belt by an angle φ = 2π / mn, the input of each belt through the radiation-receive switch, made n-positional, is connected to the output of the generator during radiation, and the outputs when received each of the m converters of each belt are connected through an n-position radiation-receive switch made in the m-channel receive mode with the corresponding information inputs of the received signal processing device, also made m-channel m, m information outputs of the processing device are connected to the corresponding m inputs entered into the receive path of the memory block containing k memory cells for storing, for each of the m channels at n positions of the radiation-receive switch, the received echo signals discretized by l distance elements, kmn outputs memory blocks are connected to the corresponding kmn inputs of an electronic indicator made by kmn-channel. 3. The sonar station according to claim 2, characterized in that the receiving path, including a device for processing received signals, a memory unit and a control panel with an electronic indicator, is made on digital computer technology.

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