JP6634272B2 - Unmanned aerial vehicle detection device - Google Patents

Description

  The present invention relates to an unmanned aerial vehicle detection device.

  At present, unmanned aerial vehicles called so-called "drones" have been regarded as a problem. In other words, such unmanned aerial vehicles are currently in a situation where it is not possible to properly restrict their flights due to the lack of a sufficient legal system. Have been.

Applicants have attempted to search the patent literature for such unmanned aerial vehicles, termed "drones", but have been unable to find a suitable one. However, a technology relating to a drone detection system using aerial acoustic technology is disclosed on a URL homepage described as Non-Patent Document 1 below. The drone detection system realizes early detection of an incoming drone by analyzing the flying sound of the drone.
In addition, Non-Patent Document 2 below describes a technique for discovering an unmanned aerial vehicle by distinguishing it from birds and clouds by using image processing technology.

URL: https://www.oki.com/jp/press/2015/05/z15016.html Nikkei newspaper on October 4, 2015

  By the way, in the above-mentioned conventional technology, there is a problem that an unmanned aerial vehicle cannot be sufficiently distinguished from other flying objects. For example, the technology of Non-Patent Document 1 analyzes the flying sound of a drone, but it is difficult to distinguish an unmanned aerial vehicle from a flying object such as a bird (disturbing object) due to a disturbance in background sound. In particular, it is difficult to distinguish an unmanned aerial vehicle or a flying object flying a relatively long distance from a flying object (a disturbance substance) such as a bird.

  Further, although the technology of Non-Patent Document 2 uses image processing technology, since the resolution of the image is limited, flying objects such as birds flying relatively far away cannot be distinguished from unmanned aerial vehicles. . In addition, when the color of an unmanned aerial vehicle or a flying object is the same or similar to the background color of the sky or the like, the contour of the unmanned aerial vehicle or the flying object cannot be accurately detected. Cannot be distinguished.

  The present invention has been made in view of the above-described circumstances, and has as its object to detect an unmanned aerial vehicle more reliably than in the related art and to detect it.

  In order to achieve the above object, according to the present invention, as a first solving means according to the unmanned aerial vehicle detection device, a beat signal is generated by radiating a transmission wave of a predetermined frequency in space and receiving a reflection wave of the transmission wave. Transmitting and receiving means, and a detecting means for detecting an unmanned aerial vehicle flying in space by performing predetermined signal processing on the beat signal, wherein the detecting means is configured to detect a frequency component of a body vibration unique to the unmanned aerial vehicle by the beat signal. Is determined by determining whether the unmanned aerial vehicle is included in the unmanned aerial vehicle and another flying object.

  As a second solution according to the unmanned aerial vehicle detection device, in the first means, the transmission / reception unit emits the transmission wave to space based on a two-frequency CW system, an FM-CW system, or a CW Doppler system. Means for generating the beat signal.

  As a third solution according to the unmanned aerial vehicle detection apparatus, in the first or second means, the detection means extracts a peak frequency from a frequency component obtained by performing an FFT process on the reflected wave, and Means for determining that a frequency component exceeding a predetermined threshold value is caused by the unmanned aerial vehicle.

  As a fourth solution according to the unmanned aerial vehicle detection device, in any one of the first to third means, the detection means employs means for radiating a microwave as the transmission wave into space.

  According to the present invention, an unmanned aerial vehicle is detected by judging whether or not a signal component of a body vibration unique to an unmanned aerial vehicle is included in a beat signal. (Disturbance).

It is a block diagram showing functional composition of an unmanned aerial vehicle detection device concerning one embodiment of the present invention. It is a mimetic diagram for explaining a detection principle of an unmanned aerial vehicle detection device concerning one embodiment of the present invention. 5 is a flowchart illustrating signal processing according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The unmanned aerial vehicle detection device A according to the present embodiment includes an oscillator 1, a directional coupler 2, a transmission antenna 3, an oscillation control unit 4, a reception antenna 5, a mixer 6, a signal processing unit 7, and an output unit as shown in FIG. 8 is provided.

  The unmanned aerial vehicle detection device A is a device that detects an unmanned aerial vehicle T flying in space by using a microwave. The unmanned aerial vehicle detection device A detects the unmanned aerial vehicle T using microwaves generated based on the two-frequency CW method.

  Here, the unmanned aerial vehicle T to be detected by the unmanned aerial vehicle detection device A according to the present embodiment is an unmanned small airplane generally called a “drone”. As shown in FIG. 2, this unmanned aerial vehicle T has, for example, four thrust devices t1 to t4 (rotary wings) mounted at different positions with respect to the fuselage t5. These thrust devices t1 to t4 are powered by a motor or a small engine, and are also vibration sources for the body t5.

  The fuselage t5 of the unmanned aerial vehicle T has such a property that minute vibrations (body vibrations) are always repeated by the operation of the thrust devices t1 to t4, that is, the vibration sources attached to different parts. The frequency of the minute vibration (vibration frequency) naturally has a property of increasing in frequency as the number of thrust devices increases, although it is natural in structural mechanics. Although the details will be described later, the unmanned aerial vehicle detection device A according to the present embodiment focuses on the minute vibration of the airframe t5 unique to the unmanned aerial vehicle T from among the unmanned aerial vehicles T (flying objects) flying in the air. Is to be identified.

  It should be noted that such unmanned aerial vehicles T include those that fly by remote control using a remote controller and those that fly independently by being equipped with a GPS, an attitude control sensor, and the like. Many "drones" currently known have at least three thrust devices, and most have more than three and even number of thrust devices to ensure flight stability.

  Now, the oscillator 1 constituting the unmanned aerial vehicle detection device A according to the present embodiment is a signal that generates a sine wave signal in which two frequencies f1 and f2, which are predetermined frequencies, repeat at regular intervals based on a two-frequency CW method. Generator. That is, the oscillator 1 is a voltage-controlled oscillator that sets the oscillation frequency to two frequencies f1 and f2 based on the square wave signal input from the oscillation control unit 4. Such an oscillator 1 oscillates, for example, a sine wave of frequency f1 during the low level period of the square wave signal, and oscillates a sine wave of frequency f2 during the high level period of the square wave signal.

  The directional coupler 2 is a three-port circulator that outputs a sine wave signal input from the oscillator 1 to the transmission antenna 3 and the mixer 6. The directional coupler 2 outputs a sine wave signal as described above, but has a property of not transmitting a signal in the opposite direction. That is, in the directional coupler 2, a signal input from the transmission antenna 3 or the mixer 6 is not output to the oscillator 1.

  The transmission antenna 3 is a horn antenna or a reflector antenna designed for microwave transmission. The transmission antenna 3 converts a sine wave signal (electric signal) input as a transmission signal from the directional coupler 2 into a radio wave (transmission wave) and radiates it to space. This transmission wave is reflected when an object (flying object) that reflects a microwave exists in the space, and generates a reflected wave.

  The oscillation control unit 4 is a control device that controls the operation (oscillation) of the oscillator 1. The oscillation controller 4 outputs the square wave signal to the oscillator 1 as described above, thereby controlling the frequency of the sine wave signal output from the oscillator 1 to predetermined frequencies f1 and f2. Further, the oscillation control unit 4 outputs a timing signal synchronized with the square wave signal to the signal processing unit 7. Note that the repetition frequency and duty ratio of the square wave signal are set as appropriate.

  The receiving antenna 5 is a horn antenna or a reflector antenna designed for microwave reception. The receiving antenna 5 converts a reflected wave (radio wave) caused by the flying object into a received signal (electric signal) and outputs the signal to the mixer 6. The reflected wave is derived from the transmission wave, and thus has characteristics derived from the flying object in addition to the frequency, amplitude, and time characteristics of the transmission wave.

  Although not shown, the transmitting antenna 3 and the receiving antenna 5 include a predetermined scanning device so that the transmitting direction of the transmitting wave and the receiving direction of the reflected wave become a two-dimensional space having a predetermined width. The direction is variable. That is, this two-dimensional space is a monitoring area of the unmanned aerial vehicle detection device A. The transmitting antenna 3 sequentially radiates transmission waves to the monitoring area in a predetermined order in a scanning manner. Then, the receiving antenna 5 catches a reflected wave incident from the radiation direction of the transmitted wave.

  The mixer 6 is an analog multiplication circuit that multiplies the transmission signal and the reception signal, and outputs the multiplication signal to the signal processing unit 7. The multiplication signal includes a beat signal (beat signal) generated by multiplication (interference) between the transmission signal and the reception signal. That is, the beat signal generated by the mixer 6 based on the two-frequency CW method includes the distance to the flying object and the flying speed of the flying object as information on the flying object.

  The oscillator 1, the directional coupler 2, the transmission antenna 3, the oscillation control unit 4, the reception antenna 5, and the mixer 6 radiate a microwave as a transmission wave in space and receive a reflected wave of the transmission wave. The transmission / reception unit that generates the beat signal is configured as a whole. This transmitting / receiving section corresponds to the transmitting / receiving means of the present invention.

  The signal processing unit 7 detects the unmanned aerial vehicle T by performing predetermined signal processing on the beat signal. This signal processing unit 7 corresponds to the detecting means of the present invention. That is, the signal processing unit 7 performs predetermined signal processing on the multiplication signal based on the timing signal input from the oscillation control unit 4 to detect whether the flying object is the unmanned aircraft T. The details of the signal processing in the signal processing unit 7 will be described later as an operation description.

  The output unit 8 outputs the processing result of the signal processing unit 7, that is, the attribute information of the flying object to the outside, and is, for example, a display device and / or a communication device. When the output unit 8 is a display device, the output unit 8 outputs the type of the flying object, that is, the unmanned aircraft T or the unmanned aircraft T in addition to the position and the flying speed of the flying object as the attribute information of the flying object. An image is displayed as to whether it is a flying object other than.

  Next, the operation of the thus-configured unmanned aerial vehicle detection device A will be described in detail with reference to FIG.

  The transmission / reception unit in the unmanned aerial vehicle detection device A generates a beat signal based on the two-frequency CW method by receiving the reflected wave of the transmission wave radiated to the monitoring area as described above. Then, the signal processing unit 7 outputs the detection result in the monitoring area to the output unit 8 by performing the processing shown in FIG. 3 on the beat signal based on the timing signal input from the transmission / reception unit.

  First, the signal processing unit 7 converts a beat signal, which is an analog signal, into a digital signal (beat data string) (step S1). That is, the signal processing unit 7 sequentially converts the beat signal in synchronization with the timing signal to convert the beat signal into two beat data strings D1 and D2 corresponding to the two frequencies f1 and f2 of the transmission signal. Then, the signal processing unit 7 obtains two beat frequency data Df1 and Df2 indicating the frequency characteristics of the two beat data strings D1 and D2, respectively, by performing the FFT processing on the two beat data strings D1 and D2 (step). S2).

  Then, the signal processing unit 7 performs the following two processes on the two beat frequency data Df1 and Df2 obtained in this manner. One is a process of detecting the distance to the flying object and the flying speed of the flying object (flying state detection process), and the other is a process of determining whether the flying object is the unmanned aircraft T (type determination process). It is.

  The flying state detection processing includes peak detection processing for the two beat frequency data Df1 and Df2 (step S3), and calculation processing for calculating the distance to the flying object and the flying speed of the flying object (step S4). . This flying state detection processing is a known processing based on a two-frequency CW method. In the calculation process (step S4), the distance to the flying object is calculated based on one of the peak frequencies of the two beat frequency data Df1 and Df2 obtained in the peak detection process (step S3). The flying speed of the flying object is calculated based on the phase difference between the beat frequency data Df1 and Df2.

  In the type determination processing, the frequency distribution detection processing (step S5) for the two beat frequency data Df1 and Df2, and whether the flying object is an unmanned aircraft T based on the frequency distribution detection processing (step S5) is determined. The processing comprises a type determination process (step S6).

  In the frequency distribution detection processing, the frequency distributions of the two beat frequency data Df1 and Df2, that is, the lowest frequency and the highest frequency are detected. Then, in the type determination processing, it is evaluated whether or not the highest frequency is higher than a preset (stored) determination threshold. If the highest frequency is higher than the determination threshold, the flying object is unmanned aircraft T When the highest frequency is equal to or lower than the determination threshold, it is determined that the flying object is not the unmanned aircraft T.

  Here, the determination threshold will be additionally described. The unmanned aerial vehicle T is a small airplane provided with, for example, four thrust devices t1 to t4 as described above. During flight, each thrust device t1 to t4 serves as a vibration source, and the body t5 repeats minute vibration. This minute vibration depends on the structure of the body t5, but is at least several hundred Hz on the order of at least. The minute vibration having such a frequency is a vibration frequency at which natural objects such as birds assumed as flying objects and artificial objects such as balloons do not emit. The vibration generated by the natural or artificial object has a frequency on the order of several hertz.

  The discrimination threshold value in the present embodiment is set to a frequency at which the unmanned aerial vehicle T can be distinguished from the above-mentioned natural and man-made objects, for example, about 100 Hz. In the type discrimination process (step S6), the discrimination threshold set in this way is compared with the highest frequency of each beat frequency data Df1, Df2, and the highest frequency of each beat frequency data Df1, Df2 is determined. Is determined to be an unmanned aerial vehicle T, which is flying in the monitoring area when the state exceeding the predetermined time exceeds a predetermined time.

  As a result of the flight state detection processing and the type determination processing, the signal processing unit 7 outputs the distance to the unmanned aircraft T and the flying speed of the unmanned aircraft T to the output unit 8 as a detection result. Then, the output unit 8 notifies the detection result to the outside.

  According to the present embodiment, the unmanned aircraft T is distinguished from other flying objects based on the frequency of the minute vibration of the body t5 unique to the unmanned aircraft T. It can be detected separately from the body.

  Here, as a method of discriminating the unmanned aerial vehicle T from other flying objects, it is conceivable to use a frequency component of a beat signal resulting from rotation of the thrust devices t1 to t4 (rotary wings). Since the thrust devices t1 to t4 (rotor blades) are rotating (moving) at a predetermined number of revolutions, the beat signal includes the influence of the rotation as a frequency component.

  However, some unmanned aerial vehicles have a thrust device (rotor wing) covered by a cover. An unmanned aerial vehicle with such a cover cannot be identified as an unmanned aerial vehicle because the beat signal does not show the influence of the rotation of the thrust device. As a result of considering such a viewpoint, in the present embodiment, a method of discriminating the unmanned aerial vehicle T from other flying objects based on the frequency of the minute vibration of the body t5 unique to the unmanned aerial vehicle T is adopted.

Note that the present invention is not limited to the above embodiment, and for example, the following modified examples can be considered.
(1) Although the transmitting and receiving unit in the above embodiment is based on the two-frequency CW method, the present invention is not limited to this. For example, the transmitting and receiving unit may be configured based on the FM-CW system or the CW Doppler system.

(2) In the above embodiment, a microwave is used as a transmission signal, but the present invention is not limited to this. As long as the medium has a frequency (detection resolution) capable of detecting the minute vibration of the body t5 of the unmanned aerial vehicle T, for example, a millimeter wave or light (laser light) may be used.

A Unmanned aerial vehicle detection device 1 Oscillator 2 Directional coupler 3 Transmission antenna 4 Oscillation control unit 5 Receiving antenna 6 Mixer 7 Signal processing unit 8 Output unit T Unmanned aerial vehicle t1 to t4 Thrust device t5 Aircraft

Claims (4)

Transmitting and receiving means for emitting a transmission wave of a predetermined frequency into space, receiving a reflected wave of the transmission wave and generating a beat signal,
Detecting means for detecting an unmanned aerial vehicle flying in space by performing predetermined signal processing on the beat signal,
The unmanned aerial vehicle detection device, wherein the detecting unit determines whether the unmanned aerial vehicle is different from another flying object by determining whether a frequency component of a body vibration unique to the unmanned aerial vehicle is included in the beat signal.   2. The unmanned aircraft detection device according to claim 1, wherein the transmission / reception unit radiates the transmission wave to space based on a two-frequency CW system, an FM-CW system, or a CW Doppler system to generate the beat signal. . It said sensing means, unmanned aircraft sensing apparatus according to claim 1 or 2, wherein the frequency component obtained by FFT processing the beat signal is equal to or determines that the unmanned aircraft exceeds a predetermined determination threshold. The unmanned aircraft detection device according to claim 3, wherein the detection unit radiates a microwave as the transmission wave to a space.

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