RU2722968C1 - Acoustic active aerial objects detection device - Google Patents

Abstract

FIELD: metrology.SUBSTANCE: invention relates to metrology and can be used for detection of airborne objects, for example small and lightly noisy unmanned aerial vehicles. Device for detecting acoustically active aerial objects includes two acoustic sensors shifted relative to each other along a vertical line, a canopy of soundproof material installed under them, a unit for processing electric signals of acoustic sensors. Unit includes balancing units, inputs connected to sensors, and outputs – to inputs of subtracting device, output of which is connected via strip filter to decision making unit. Said deflector is composed of ascending and descending elements. Bottom parts of the shield elements are located below the lower acoustic sensor. In one version, the soundproof perforated shield has a shape which forms a rectangular or C-shaped contour in a horizontal projection, the end face is fixed on the surface of a flat structure, for example on a wall or a bridge support, on which acoustic sensors are also mounted. In another version, soundproof perforated cap constructs axisymmetric closed circuit and is installed on vertical support passing through center of symmetry of shield, at that acoustic sensors are located on top of support.EFFECT: technical result is increase in detection range.3 cl, 4 dwg, 1 tbl

Description

The invention relates to techniques for receiving signals from sources of sound waves and can be used to detect airborne objects, for example, small-sized and slightly noisy unmanned aerial vehicles.

A known detection system for unmanned rotary-wing aircraft (RF patent 2593439 IPC G01S 17/00), which contains four acoustic sensors with a known relative position and location relative to the controlled area in space. Each acoustic sensor consists of a receiver and a unit. detection and classification. The output of the receiving device is connected to the input of the detection and classification unit, which is connected to the operational control and decision making unit, which is connected to the warning and indication system. The operational control and decision making unit is also connected to the camera pairing unit, which is connected to a rotary camera with a known spatial location and rotation speed.

A known system and method for detecting rotary-wing unmanned aerial vehicles described in US patent 7957225 B2, in which an acoustic signal is received using a set of acoustic sensors, the acoustic signal source is classified based on the spectral analysis of the acoustic signal, horizontal coordinates and the height of the acoustic signal source are determined based on the analysis at least four acoustic signals received from four acoustic sensors.

The presence of intense background noise when using known devices complicates the detection of a signal (acoustic marker) by known devices, adversely affects the quality of signal analysis and detection range.

If the directions to the noise source and the signal source obviously do not coincide, spatially selective devices can be used to detect and isolate the useful signal. In this case, an increase in the detection range of an object emitting an acoustic signal can be realized by attenuating the background noise in the receiving direction.

A device for directional signal reception, consisting of a receiving sensor mounted in the focus of a parabolic reflector (patent for utility model RU No. 113878, H01Q 3/08).

A device for directional signal reception, consisting of a receiving sensor and a wave transformer, made in the form of a conical or exponential horn nozzle (eg, patent for utility model RU No. 140983, H01Q).

Wide-aperture devices for the directional reception of acoustic signals are also known, consisting of a large number of elements organized in arrays / arrays (NP Krasnenko, AS Rakov and others. “Acoustic antenna array with electronically controlled beam pattern.” - TUSUR reports No. 3 (29), September, 2013).

The disadvantage of these devices is the dependence of the spatial selection efficiency on the angular size of the survey segment: the larger the absolute values of dA / dϕ and dA / dθ at the decay of the main lobe of the radiation pattern, the smaller the viewing window area ΔθΔϕ. To overlap a large sector of space (limited, for example, by the limits of the upper hemisphere), it is necessary either to provide a scanning mode along the grid of angles θ and ϕ, or to use a parallel working group of devices aimed at different parts of space.

Scanning mode leads to an additional delay in object recognition, as well as an increase in the probability of skipping an object, because Signals from different directions are received at the same time.

The aim of the invention is to improve the selection of the useful signal in a noisy environment.

The technical result is to increase the detection range of acoustically active aircraft by suppressing background acoustic noise coming from irrelevant "sub-horizontal" directions.

To achieve this result, the device for detecting acoustically active airborne objects includes two acoustic sensors vertically offset from each other, a visor made of soundproof material mounted under them, an acoustic signal processing unit for acoustic signals, including balancing nodes connected to the sensors by inputs and outputs to the inputs of the subtractor, the output of which through the bandpass filter is connected to the decision-making unit, while the visor is made of ascending and descending elements, the intersection of which forms the peak line of the peak, the lower parts of which are located below the lower acoustic sensor, and each point on the peak line of the peak is equidistant from both acoustic sensors.

In one embodiment, the soundproof visor has a shape that forms in a horizontal projection a rectangular or C-shaped contour, end-mounted on the outer surface of the wall (building or bridge support), on which acoustic sensors are also mounted.

In another embodiment, the soundproof visor constructively forms an axisymmetric closed loop and is mounted on a vertical support passing through the center of symmetry of the visor, with acoustic sensors located on top of the support.

Using a visor made of soundproof material, making of ascending and descending elements with the creation of a vertex at the points of their intersection allows you to create a specific configuration of the acoustic shadow from the “horizontal” noise background.

The placement of acoustic sensors along a vertical line in the region of the acoustic shadow of the visor from the “horizontal” background noise can improve the detection of useful signals and increase the detection range of the tracked small-sized flying object.

The processing unit for the electrical signals of acoustic sensors provides the mutual destruction of “subhorizontal” noises that fall into the area of both sensors.

As a result of the search, no information was found allowing to conclude that the distinguishing features of the claimed device are known, therefore, the claimed technical solution meets the novelty condition.

From the prior art it is not known the influence of the distinctive features of the claimed device on the achieved technical result, therefore, the claimed device meets the condition of an inventive step.

The invention is illustrated by drawings, where in FIG. 1 presents a structural diagram of the inventive device.

The inventive device contains two acoustic sensors 1 and 2, a visor 3 fixed under them, an electric signal processing unit 4. The visor 3 is a structure of soundproof material made of ascending 5 and descending 6 elements, the intersection of which forms the peak line of the visor. Acoustic sensors 1, 2 are located along a vertical line, while the lower part of the descending element 6 of the visor 3 is located below the lower acoustic sensor 2, and each point on the connection line of the ascending and descending elements of the visor 3 is equidistant from both acoustic sensors. This ensures a stable configuration of the acoustic shadow on sensors 1 and 2 with respect to acoustic noise coming from a wide sector of “horizontal” directions, which allows you to successfully suppress interfering (irrelevant) noise by the method of mutual compensation in the device’s electric path.

Depending on the installation location of the claimed device and the probable direction of arrival of acoustic noise, the visor can have a different configuration: the projection of the visor 3 on a horizontal plane can form a rectangular, or C-shaped (Fig. 2), or a circular contour (Fig. 3). For example, to provide an azimuthal viewing sector of up to 180 degrees, the device construct (including acoustic sensors) can be located directly on a flat structural element, for example, on a building wall or bridge support. In this case, a soundproof visor in a horizontal projection constructively forms a rectangular or C-shaped contour that abuts against the wall. To ensure a panoramic (circular) view, the soundproof visor in the horizontal plane is self-closed, fixed at a predetermined level by a vertical support passing through the center of the horizontal projection of the visor. At the top of this support are acoustic sensors. The structure can be deployed either in an open area above the level of objects creating acoustic obstacles, or at the top level of structures (for example, on the roof of a building). The options given to the design are not limited.

As acoustic sensors 1, 2, microphones or dynamic heads can be used. Acoustic sensors 1, 2 can be placed both in separate soundproof casing (Fig. 2), and be enclosed in a common casing 12, and mounted on a support 13, common to the entire structure (Fig. 3). The distance H between the acoustic centers of the sensors 1 and 2 determines the sensitivity of the device to a useful signal in a given frequency range taking into account the direction of reception (a larger vertical separation corresponds to a larger integral sensitivity), while the value of H is limited by the condition H <C / B, where C is the speed of sound , In - the upper limit of the working frequency range. So, at the upper operating frequency Fв = 400 Hz, the vertical separation is limited to 0.8 m. The electrical signal processing unit 4 includes balancing units 7 and 8, a subtractor 9, a broadband filter 10 with transparency in the range from the lower Fн to the upper Fв operating frequency , decision node 11. Balancing nodes 7, 8 are linear amplifiers with the possibility of independently setting the gain, amplitude-frequency and phase-frequency dependences in each channel. The subtractor 9 may be, for example, a differential amplifier. The decision node 11 may be a threshold device that generates a warning command (“Threat”) when the signal at its input exceeds a predetermined (threshold) value.

The cross section of the visor 3 in the vertical plane is a triangle with the base of the speaker and a height of BD (Fig. 4), and point B in the cross section of the visor 3 is equidistant from the sensors 1 and 2, ensuring equal lengths of acoustic paths from point B to the center of sensor 1 and from point In to the center of the sensor 2. The angle of inclination of the aircraft section is selected for reasons of acoustic reflections from the wall or from the opposite part of the structure to the sensors 1 and 2. The limit value of the angle obtained from these considerations is 30 degrees; the choice close to the limiting value is optimal to minimize the overall dimensions of the device. The slope of the AB section is selected so that in continuation of the straight line passing through these two points, both sensors are below it, that is, in the acoustic shadow zone of the background noise sources (Fig. 4). The direction defined by the orientation of the AB section defines the line of the “reception horizon”.

Subject to the specified conditions, the width of the visor (speaker size) for the frequency range 200-400 Hz will be about 2 meters.

The device is balanced by signals coming from directions below the line of the "horizon of reception", according to the criterion of maximum signal suppression in the operating frequency band. The transmission coefficient of node 8 of the balanced path exceeds the transmission coefficient of node 7 by an average of 2.5 dB in the specified frequency range (about 2 dB for a frequency of 200 Hz, about 2.5 dB for a frequency of 300 Hz and about 3 dB for a frequency of 400 Hz).

The device operates as follows.

For acoustic waves coming from below (rumble of traffic, noise of street crowds, etc.), in the general case - interfering sounds from directions bounded below by the AB line (Fig. 4), receiving sensors 1 and 2 are in the shadow zone from the visor 3 ( in Fig. 4, the "shadow zone" is indicated precisely for this case). Part of the energy coming from the lower direction of the waves is reflected from the visor 3 down and to the sides. Another part of it diffracts at point A, propagates along the portion AB acting as a sound guide, then diffracts again at point B and, splitting, falls on sensors 1 and 2. The arrangement of the sensors ensures equal length of acoustic paths B1 and B2. The neutralization of these noise components, balanced to the necessary extent by the nodes 7 and 8, occurs in the device 9.

Thus, the presence of a visor made of soundproof material, the execution of the ascending and descending elements under the acoustic sensors changes the local configuration of the acoustic field, providing a uniform and in-phase distribution of the horizontal background in the area where both sensors are located. In the processing unit 4 there is a mutual compensation of the electrical signals of the sensors induced by the subhorizontal component of the acoustic background. As a result, the signal received from the “horizontal” directions is freed from the influence of the interfering “horizontal” noise.

A similar situation occurs for sound waves arriving from “subhorizontal” lateral directions (Fig. 4, wavefront line f135). Thus, the insensitivity of the claimed device is provided with respect to signals arriving "from below" and from "lower lateral directions."

The signal from the source of the sound wave arriving at point B from the direction above the "reception horizon" (Fig. 4, front line f105) arrives at sensor 1 directly, in a straight line | s1 |. Because of this, the signal amplitude at the output of the sensor 1 turns out to be larger than at the output of the sensor 2. Sensor 2 continues to remain in the acoustic shadow zone for this wave; its path to the sensor 2 consists of two parts, | wB | + | B2 |. In addition, for this direction of arrival, the difference in acoustic lengths is no longer zero: | s1 | <| xB | + | B2 |. Both factors - amplitude and phase - lead to imbalance in the reception channel, and therefore to the appearance of an uncompensated component at the output of the subtractor 9. The larger the angle between the direction of sound propagation and the line AB (Fig. 4 shows the directions of the wavefront at an angle of 75 and 60

hail, i.e. left-top), the greater the difference in the path of the rays with an additional imbalance in sound intensity, and the larger the signal arrives at the decision node 11.

The experimentally measured dependence of the output voltage at the input of node 11 on the direction of the angle of sound arrival is shown in the table.

The experimentally confirmed efficiency of suppressing the subhorizontal components of the noise background reaches 30 dB or more, which increases the detection range of UAVs by about thirty times.

Claims (3)

1. A device for detecting acoustically active airborne objects, including two acoustic sensors offset relative to each other along a vertical line, a visor made of soundproof material installed under them, an acoustic signal processing unit for acoustic signals, including balancing nodes connected to the sensors by inputs and outputs to the inputs of the subtractor, the output of which through the band-pass filter is connected to the decision-making unit, while the visor is made of ascending and descending elements, the intersection of which forms the peak line of the peak, the lower parts of the peak are located below the lower acoustic sensor, and each point on the peak line of the peak is equidistant from both acoustic sensors. 2. The device according to claim 1, characterized in that the soundproof visor has a shape that forms a rectangular or C-shaped contour in horizontal projection, is end-mounted on a surface of a flat structure, for example, on a wall or bridge support, on which acoustic sensors are also mounted. 3. The device according to claim 1, characterized in that the soundproof visor constructively forms an axisymmetric closed loop and is mounted on a vertical support passing through the center of symmetry of the visor, while the acoustic sensors are located on top of the support.

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