RU2713005C1 - Multi-static underwater surveillance system - Google Patents

Abstract

FIELD: hydroacoustics.

SUBSTANCE: invention relates to the field of hydroacoustics, namely to multi-static underwater surveillance systems. Solved technical problem is improvement of composition and structure of MUSS. Said technical result is achieved by the fact that the entire area of the controlled sea region is divided into adjacent identical squares, including one IGS located in the center of the square, and a multiple of four PGS set located inside the square. Amount of PSG and their arrangement are calculated taking into account the following conditions: -at each point of the square the probability of detecting an underwater object in given hydroacoustic conditions should be not less than a given probability of detection at a given probability of false alarm; -squared area should be maximum possible; -number of PGS placed in a square shall be minimum possible.

EFFECT: determination of minimum amount of IGS and PGS and geographic coordinates of their installation to ensure a given probability of detecting an underwater object of a given class at a given probability of false alarm when the object is located in any point of the monitored area.

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Description

The invention relates to the field of hydroacoustics, namely to active underwater surveillance systems.

Active underwater observation systems are divided into monostatic sonar systems (HLS-mono) [1], characterized by the location of the transmitting and receiving antennas at one point in space, and multistatic sonar systems (HLS-multi) [2], which are distinguished by the spatial separation of the transmitting and receiving antennas.

The advantages of GLS-mono are lower manufacturing costs and greater ease of use, which is due to the possibility of placing the system on one ship or in a single hull when installing it in a stationary version. Another advantage of SFS-mono is the possibility of observing (evaluating the classes, coordinates, velocities and courses of underwater objects located in the controlled area) using one underwater system in the entire circular sector of angles. The disadvantage of HFS-mono lies in the shorter (in comparison with HFS-multi) detection range of underwater objects, which is due to the large attenuation of the probing signal (GL) when it propagates to the object and vice versa. As a result, FPP mono are installed on mobile marine objects (submarines, surface ships, underwater vehicles) or in the form of bottom stations that are not designed to monitor the underwater situation in large areas (an example of such a station is the detection of underwater swimmers).

The advantage of the SFS-multi compared to the SFS-mono is the large detection range, due to the shorter path of the propagation of GLs when the receiving antenna is closer to the object compared to the study antenna. The disadvantages of GLS-multi are the significant cost of manufacturing and positioning, as well as the inability of one emitting and one receiving antenna to illuminate the underwater situation in the circular sector of angles relative to the emitter.

Currently, the urgent task is to create underwater surveillance systems in areas of large area, both in coastal areas and in the open sea. The sonar systems previously used for this purpose with wide-aperture antennas with an area of up to 1000 m ² were ineffective due to their susceptibility to deliberate opposition from the enemy. In recent decades, the ideology of large sonar systems has been replaced by the ideology of multistatic underwater observation systems (MSPN) [2-9]. MSPN includes a set of integrated sonar network (GHS) control center (PU) MSPN, as well as co-operating spatially separated autonomous emitting (GHS) and receiving (ASG) sonar stations (Fig. 1). GHS periodically, according to the established program, emit ES, which are reflected from underwater objects (hereinafter referred to as objects) and are accepted by ASG. ASGs detect reflected signals (echo signals - ES) and by analyzing them determine the class of the underwater object, its coordinates (bearing and distance) and motion parameters (course and speed). The fact of detecting an object, its class, as well as the coordinates and motion parameters in the form of an ASG form by means of a GHS is transmitted to the MSPN control center. Transmission is in relay mode, i.e. each ASG that has accepted the form translates it to the next ASG. As a result of relaying, the form reaches the control room.

The advantages of MSPN are:

- the ability to monitor the underwater situation in the area of a large area, including by increasing the number of IHC and ASG;

- high resistance to deliberate counteraction due to the covert installation of stations and, as a result, the enemy’s unknown location of ASGs and the difficulty of disabling all emitting stations.

However, for the formation of MSPN it is necessary to solve two problems:

- determine the minimum required number of IHC and ASG to ensure compliance with the requirements for the detection of objects of specified classes at any point in the controlled area with a given probability (at a given level of false alarms) in given hydroacoustic conditions;

- determine the position of each IHC and ASG.

Ways to solve these problems in the sources are not given. The exception is the work [6], however, in it the arrangement of the IHS and ASG is considered only from the position of ensuring the specified accuracy of determining the coordinates of the object.

As a prototype we choose MSPN described in [4]. This MSPN consists of GHS and ASG, united in a single network using GHS, according to which data on detected underwater objects are transmitted to the control station. The main disadvantage of the prototype is the lack of methods for determining the number of IHC and ASG and the geographical coordinates of their installation to provide a given probability of detecting an object at any point in the controlled area for a given probability of false alarm.

Solved technical problem - improving the composition and structure of MSPN.

The technical result is the determination of the minimum number of IHC and ASG and the geographical coordinates of their installation to ensure a given probability of detection of an underwater object of a given class at a given probability of false alarm when the object is located anywhere in the controlled area.

The specified technical result is achieved by the fact that the entire area of the controlled area of the sea is divided into adjacent identical squares, including one IHS located in the center of the square, and a set of ASG located inside the square. The number of ASGs and their location are calculated taking into account the following conditions:

- at each point of the square, the probability of detecting an underwater object in a given sonar environment should be at least a given detection probability;

- the area of the square should be as possible;

- the number of ASGs to be squared should be as low as possible.

To fulfill these conditions, the following algorithm for calculating the number of ASGs and their location inside the square is proposed:

1) For the case of the location of the IHS, ASG and the object on the same straight line (Fig. 2), the values of the depths of the antennas of the IHS (N _IHS ) and ASG (N _ASG ) and the distance between the IHS and ASG (R _IHS-ASG ) are determined at which the detection range of the object (relative to the IHS) with a probability of detection of P _OB would be maximum (Fig. 2).

In a formalized form, this problem consists in finding from equation [10]:

such values of Н _ИГС , Н _ПГС and R _{ИГС-ПГС} , at which the value of R _ИГС-Ц will be maximum.

In equation (1):

Q _o (H _IGS , N _ASG , R _IGS-ASG , R _IGS-C ) - signal-to-noise ratio (SIR) of the detected object as a function of N _IGS , N _ASG , R _IGS-ASG , R _IGS-Ts ;

Q _pore is the threshold OSB corresponding to the given P _obn and P _lt , for coherent processing of the echo signal calculated by the formula [10]:

Concretizing the left side of equation (1), we obtain [10]:

Where

B - AP base:

B = Δƒ _ЗС ⋅T

Δƒ _ЗС - band of frequencies ЗС;

ƒ _AP - the average frequency of AP;

T - the duration of the AP;

Р _ЗС - pressure of ЗС in the band Δƒ _ЗС on the axis of the directivity characteristic (ХН) of the radiating antenna, reduced to 1 m from the radiating antenna;

R _equiv - bistatic equivalent radius of the underwater object;

β is the spatial attenuation coefficient of the acoustic signal at the ES frequency;

A (ƒ _ЗС , Н _ИГС , Н _Ц , R _ИГС-Ц ) - anomaly of the distribution of ЗС on the path of the IGS - object;

N _C - the depth of the underwater object (hereinafter the depth of the object);

A _C-ASG (ƒ _ЗС , Н _Ц , Н _ПГС , R _ИГС-Ц - R _{ИГС-ПГС} ) - anomaly of the propagation of ЗС on the object-ASG path.

The solution of equation (3) is carried out by enumerating within the acceptable limits the values of N _IHS , N _ASG and R _IHS-ASG with the simultaneous calculation of the value of R _IHS-C from the condition of equality of the left and right sides of the equation.

The initial data for the calculation are:

- characteristics of the object: depth H _C and bistatic equivalent radius R _equiv ;

- the probability of detecting an object at each point of the controlled area P _obn and the probability of false alarm P _lt ;

- technical characteristics of the IHS (type and geometrical dimensions of the emitting antenna, average frequency of the ЗС ƒ _ЗС , frequency band ЗС Δƒ _ЗС , pressure Р _ЗС ЗС on the ХН axis of the emitting antenna, reduced to a distance of 1 m from the emitter of the IHS, type of probe signal);

- technical characteristics of ASG: operating frequency band Δƒ _ASG , geometric dimensions and type of antenna (location of hydroacoustic receivers in the antenna array - along the generatrix of the cylinder, sphere, etc.);

- hydroacoustic characteristics of the controlled area of work: the depth of the area, the vertical distribution of the speed of sound, the waves of the sea surface, the spatial attenuation coefficient of the acoustic signal.

2) The maximum distance d between two ASGs equidistant from the IHS is determined (Fig. 3), at which the probability of detecting an underwater object passing between them would be no less than the specified probability of detection.

This problem is solved by solving with respect to d equations:

Where

3) A multiple of the 4th number of ASG is determined for installation inside one square.

where [x] is the operation of calculating the largest integer less than x.

From formula (6) it follows that the number of ASGs inside one square should be a multiple of four.

4) The coordinates of the ASG installation inside the square are determined (Fig. 4):

- if N _ASG = 4, ASGs are installed on the diagonals of the square symmetrically by the GHS at a distance R of the _GHS-ASG from it;

- if N _ASG > 4, then the remaining ASGs (in the amount of N _ASG - 4) are installed on a straight line connecting the nearest ASGs, in the intervals between the nearest ASGs, at the same distance d _ASG from each other, calculated by the formula

The side of the square L is determined (Fig. 4):

Consider a typical example.

Let it be necessary to control the underwater situation in an area having a rectangular shape with side lengths of 85 and 40 km, with a probability of detecting an underwater object at each point of its location in the controlled area of at least P _obn = 0.9 with a false alarm probability P _lt = 10 ^-4 .

Hydroacoustic conditions (GAU) correspond to the conditions of continuous acoustic illumination. The vertical distribution of the speed of sound (VSLW) is given in table. 1. Excitement of the sea 4 points.

The spatial attenuation coefficient is calculated by the formula

MSPN parameters are accepted as follows:

1) characteristics of the underwater object:

- depth H _C = 75 m;

- bistatic equivalent radius R _equiv = 3 m;

2) Characteristics of the GCI:

- type of radiating antenna - cylinder with a diameter of 15 cm and a height of 20 cm;

- ЗС frequency С _ЗС = 3.0 kHz;

- ЗС band Δƒ _ЗС = 400 Hz;

- ZS pressure on the axis ХН Р _ЗС = 10 kPa (154 dB);

- the probe signal is a pack of 5 pulses of 40 ms each pulse;

3) Characteristics of ASG

- type of receiving antenna - a cylinder with a diameter of 2.55 m and a height of 2.4 m;

- operating frequency band 0.5-6 kHz (its width Δƒ _ASG = 5.5 kHz);

Results of calculations:

- optimal depth of the antenna of the IGS N _IGS = 125 m;

- optimal depth of the antenna ASG N _ASG = 100 m;

- the optimal distance between the IGA and ASG R _IHS-ASG = 24.5 km;

- the maximum guaranteed detection range of an underwater object (with optimal antenna depths, object depth and distance between the IHS and ASG) R _IHS-C = 32.5 km;

- the maximum permissible distance between neighboring ASGs located at a distance R of the _IGS-ASG from the IGS d = 46.5 km;

- since d> 1.41⋅R IGS _-ASG , then, according to formula (6), the number of ASGs to form the square N _ASG = 4;

- the length of the side of the square L = 45.8 km.

Thus, each square has an area of 45.8 × 45.8 km ² and includes 1 IGA and 4 ASG. The GHS is located in the center of the square, and the GHS is located on the diagonals of the square at a distance of 24.5 km from the GHS. Two such squares were enough to cover the designated rectangular area with an area of 85 × 40 km ² . After the virtual coverage of the designated area with two squares, the coordinates of the IHC and ASG in the coordinate system of each area are converted into geographical coordinates.

In FIG. Figure 5 shows the resulting location of the GCI and ASG to provide control of the designated area with a given efficiency.

Thus, the claimed technical result of the invention is the determination of the minimum number of IHC and ASG and the geographical coordinates of their installation to provide a given probability of detecting an underwater object of a given class with a given probability of false alarm when the object is located at any point in the controlled area - it can be considered achieved.

Sources of information:

1. Koryakin Yu.A., Smirnov S.A., Yakovlev G.V. Ship sonar equipment. Status and current problems. St. Petersburg: Science, 2004.

2. Kovalenko V.V., Korchak V.Yu., Chulkov V.L. The concept and key technologies of underwater observation in network-centric wars // Fundamental and Applied Hydrophysics, 2011, Volume 4, No. 3, pp. 49-64.

3. Peshekhonov V.G., Braga Yu.A., Mashoshin A.I. Network-centric approach to solving the problem of lighting underwater conditions in the Arctic // Izvestiya SFedU. Engineering, 2012, No. 3, S. 219-227.

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5. Mashoshin A.I. The concept of creating integrated network systems for underwater observation // Proceedings of the Ninth Scientific and Practical Conference "Perspective Systems and Control Tasks, Taganrog, April 7-11, 2014, pp. 7-16.

6. Mikhnyuk A.N. Methods to increase the functioning efficiency of a multistatic underwater observation system. Dis. ... cand. Phys.-Math. sciences. M .: Wave Research Center, 2018.

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Claims (8)

1. A multistatic underwater observation system, including a control center, emitting hydroacoustic stations (IHS) and receiving hydroacoustic stations (ASG), united by a network of sonar communication, characterized in that the area of the monitored area of the sea is divided into adjacent squares that include the same IGA located in the center of the square, and a multiple of four the number of ASGs, while the depth of the antennas of the IHS and ASG, as well as their location in the square, is calculated based on the condition of the maximum area and a square under given hydroacoustic conditions while ensuring a given probability of detecting an underwater object at each point of the square at a given probability of false alarm. 2. The multistatic underwater observation system according to claim 1, characterized in that the number of ASG squared is calculated by the formula

where R _IGS-ASG - the distance between the ISS and ASG, providing the maximum detection range with a given probability of detection at a given probability of false alarm of an underwater object that is on a straight line with the IHS and ASG, d is the distance between two ASGs located at a distance R of the _IGS-ASG from the IHS at which the probability of detecting an underwater object in the middle of a straight line connecting them is equal to a given probability of detection for a given probability of false alarm, [x] - designation of the operation of finding the nearest integer less than x. 3. The multistatic underwater observation system according to claim 2, characterized in that the four ASGs are located symmetrically on the diagonals of the square IHS at a distance R of the _ISS-ASG from the IHS, and the remaining ASGs, if their total number is more than four, are located between the nearest ASGs on the connecting them straight line at the same distance d _ASG from each other, calculated by the formula

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