JP2022012500A - Moving target detection device, moving target detection system, moving target detection program and moving target detection method - Google Patents

Abstract

[Problem] The present disclosure aims to appropriately set a variable spectrum threshold for a vibrating target (environmental noise) when detecting the distance of a moving target using an FMCW radar, increase the sensitivity of the FMCW radar, and avoid false detection of the vibrating target (environmental noise). [Solution] The present disclosure provides a moving target detection device 2 including a beat signal acquisition unit 21 for acquiring a beat signal between transmission and reception signals of the FMCW radar, a differential signal calculation unit 22 for calculating a differential signal between beat signals of different transmission and reception cycles, a frequency spectrum calculation unit 23 for calculating a frequency spectrum of the differential signal, and a moving target output unit 25 for outputting the distance of the moving target without outputting the distance of the vibrating target (environmental noise) based on a frequency whose frequency spectrum is larger than a spectrum threshold having a peak at a frequency corresponding to the distance of the vibrating target (environmental noise). [Selected Figure] Figure 1

Description

The present disclosure relates to a technique for detecting the distance of a moving object using an FMCW (Frequency-Modulation Continuous-Wave) radar.

A technique for detecting the distance of a moving object using an FMCW radar is disclosed in Patent Document 1 and the like. Here, examples of moving objects include walking people and moving vehicles. Then, after calculating the beat signal between the transmitted / received signals, the frequency spectrum of the beat signal is calculated, and the distance of the moving object is detected based on the peak frequency of the frequency spectrum.

Japanese Patent No. 3906869

Well-known FMCW radar detects the distance of a moving object based on a frequency whose frequency spectrum is greater than the "fixed" spectral threshold for white noise (natural noise). However, the white noise (natural noise) changes with time according to the secular change or the temperature change of the FMCW radar. Therefore, it may be desirable to detect the distance of a moving object based on a frequency whose frequency spectrum is greater than the "variable" spectral threshold for white noise (natural noise).

On the other hand, the conventional CW Doppler radar can detect white noise (natural noise) in low frequency narrow band signal processing. Therefore, the variable spectrum threshold value for white noise (natural noise) can be set to an appropriate small value, the sensitivity of the CW Doppler radar can be increased, and false alarm detection of white noise (natural noise) can be avoided. ..

On the other hand, the FMCW radar of Patent Document 1 may detect not only white noise (natural noise) but also stationary and vibrating objects (environmental noise) in wideband signal processing. Here, examples of the stationary object marker include a stationary object, a ground clutter, and the like. Examples of the vibration target (environmental noise) include an indoor fan, a ventilation fan, a cooling fan, an outdoor air conditioner, a building, a tree, a flag, a banner, an engine, and the like. Therefore, the variable spectrum threshold value for white noise (natural noise) cannot be set to an appropriate small value, and it is not possible to avoid false alarm detection of white noise (natural noise) after increasing the sensitivity of the FMCW radar. ..

Further, the variable spectrum threshold value for the vibration target (environmental noise) cannot be set to an appropriate large value, and the sensitivity of the FMCW radar should be increased to avoid false alarm detection of the vibration target (environmental noise). I can't do that. Further, since the use is limited as an in-vehicle radar and the conditions are limited only to the ground clutter and the bonnet shape, the FMCW radar of Patent Document 1 can be applied to a general-purpose case where the use and conditions are not limited. Can not.

Therefore, in order to solve the above-mentioned problems, the present disclosure appropriately sets variable spectrum thresholds for white noise (natural noise) and vibration target (environmental noise) when detecting the distance of a moving target using an FMCW radar. The purpose is to avoid false alarm detection of white noise (natural noise) and vibration target (environmental noise) while increasing the sensitivity of the FMCW radar.

In order to solve the above problem, the difference signal between beat signals having different transmission / reception cycles is calculated, the frequency spectrum of the difference signal is calculated, and the distance of the moving object is detected based on the peak frequency of the frequency spectrum. do. Here, in the frequency spectrum, the frequency peak of the stationary object is removed and the frequency peak of the moving object is maintained, but the frequency component of the white noise (natural noise) and the frequency component of the vibrating object (environmental noise). The frequency peak is also maintained.

Therefore, the vibration target (environment) is based on a frequency having a larger frequency spectrum than the variable spectrum threshold (time change according to the vibration target) having a peak at the frequency corresponding to the distance of the vibration target (environmental noise). The distance of the moving object is output without outputting the distance of noise).

Then, the spectral intensity is white noise (natural noise) based on the frequency whose frequency spectrum is larger than the variable spectrum threshold (time change according to the white noise) having a flat portion at the frequency corresponding to the white noise (natural noise). ) Output the distance of a higher moving object.

Specifically, the present disclosure comprises a beat signal acquisition unit that acquires a beat signal between transmission and reception signals of an FMCW radar, a difference signal calculation unit that calculates a difference signal between the beat signals having different transmission and reception cycles, and the difference signal. Frequency spectrum calculation unit for calculating the frequency spectrum of the above, and a spectrum threshold determination unit for determining the magnitude relationship between the frequency spectrum and the spectrum threshold having a peak at the frequency corresponding to the distance of the vibration target at each frequency. A moving object target output unit that outputs the distance of the moving object without outputting the distance of the vibrating target based on the frequency whose frequency spectrum is larger than the spectrum threshold. It is a moving object detection device.

Further, the present disclosure includes a beat signal acquisition step for acquiring a beat signal between transmission and reception signals of an FMCW radar, a difference signal calculation step for calculating a difference signal between the beat signals having different transmission and reception cycles, and a frequency spectrum of the difference signal. The frequency spectrum calculation step for calculating the frequency spectrum, the spectrum threshold determination step for determining the magnitude relationship between the frequency spectrum and the spectrum threshold having a peak at the frequency corresponding to the distance of the vibration target, and the spectrum threshold determination step for determining the magnitude relationship at each frequency. A moving object for causing a computer to sequentially execute a moving object target output step that outputs a moving object target distance without outputting the vibration target distance based on a frequency whose frequency spectrum is larger than the spectrum threshold. It is a mark detection program.

Further, the present disclosure includes a beat signal acquisition step for acquiring a beat signal between transmission and reception signals of an FMCW radar, a difference signal calculation step for calculating a difference signal between the beat signals having different transmission and reception cycles, and a frequency spectrum of the difference signal. The frequency spectrum calculation step for calculating the frequency spectrum, the spectrum threshold determination step for determining the magnitude relationship between the frequency spectrum and the spectrum threshold having a peak at the frequency corresponding to the distance of the vibration target, and the spectrum threshold determination step for determining the magnitude relationship at each frequency. A moving object characterized by comprising, in order, a moving object target output step for outputting the distance of the moving object without outputting the distance of the vibrating object based on a frequency whose frequency spectrum is larger than the spectrum threshold. It is a mark detection method.

According to these configurations, when detecting the distance of the moving object, the variable spectral threshold value for the vibrating object (environmental noise) is set to an appropriate large value, the sensitivity of the FMCW radar is increased, and then the vibrating object is increased. It is possible to avoid false alarm detection of (environmental noise).

Further, in the present disclosure, the spectrum threshold determination unit does not follow the intensity change of the frequency spectrum at the frequency corresponding to the distance of the moving object and changes with time, but changes with time corresponding to the distance of the vibrating object. It is a moving object detection device characterized in that the spectrum threshold value is set according to a change in the intensity of the frequency spectrum at a frequency that does not.

According to this configuration, the variable spectral threshold value for the vibration target (environmental noise) can be set to an appropriate large value according to the time change of the frequency peak of the vibration target (environmental noise).

Further, in the present disclosure, the moving object output unit is not based on a frequency whose frequency spectrum is larger than the spectral threshold but does not change with time, but based on a frequency at which the frequency spectrum is larger than the spectral threshold and changes with time. It is a moving object detection device characterized by outputting the distance of the moving object.

According to this configuration, it is possible to avoid false alarm detection of the vibration target (environmental noise) until the variable spectrum threshold value for the vibration target (environmental noise) is set to an appropriate large value.

Further, in the present disclosure, the spectral threshold determination unit determines the magnitude relationship between the frequency spectrum and the spectral threshold having a flat portion at a frequency corresponding to white noise at each frequency, and the moving object. The target output unit is a moving object detection device characterized in that the distance of the moving object whose spectral intensity is higher than that of the white noise is output based on a frequency whose frequency spectrum is larger than the spectrum threshold.

According to this configuration, when detecting the distance of a moving object, the variable spectral threshold for white noise (natural noise) is set to an appropriate small value, the sensitivity of the FMCW radar is increased, and then white noise (natural noise) is detected. ) False alarm detection can be avoided.

Further, in the present disclosure, the spectral threshold determination unit follows the change in the intensity of the time integration in each transmission / reception cycle for the signal intensity of the difference signal, or the white noise is described at all frequencies corresponding to the white noise. It is a moving object detection device characterized in that the spectrum threshold value is set according to a change in the intensity of a frequency spectrum.

According to this configuration, the variable spectral threshold value for white noise (natural noise) can be set to an appropriate small value according to the time change of the intensity of white noise (natural noise).

Further, the present disclosure is a moving object detection system including the above-described moving object detection device and the radar transmission / reception device of the FMCW radar.

According to this configuration, it is possible to provide a system having the above-mentioned effects.

As described above, the present disclosure appropriately sets variable spectrum thresholds for white noise (natural noise) and vibration target (environmental noise) when detecting the distance of a moving object using the FMCW radar, and the FMCW radar. It is possible to avoid false alarm detection of white noise (natural noise) and vibration target (environmental noise) while increasing the sensitivity of the radar.

It is a figure which shows the structure of the moving object detection system of this disclosure. It is a figure which shows the difference signal and the frequency spectrum of the stationary object mark of this disclosure. It is a figure which shows the difference signal and the frequency spectrum of the moving object of this disclosure. It is a figure which shows the difference signal and the frequency spectrum of the vibration target of this disclosure. It is a figure which shows the procedure of the moving object detection process of this disclosure. It is a figure which shows the moving object detection process and the spectrum threshold value setting process of this disclosure. It is a figure which shows the non-detection processing of any target distance of this disclosure. It is a figure which shows the output process of the target distance of the moving object of this disclosure. It is a figure which shows the non-output processing of the target distance of the vibrating object of this disclosure. It is a figure which shows the procedure of the spectrum threshold value setting process of this disclosure. It is a figure which shows the setting process of the spectrum threshold value with respect to the white noise of this disclosure. It is a figure which shows the update process of the spectrum threshold value with respect to the white noise of this disclosure. It is a figure which shows the setting process of the spectrum threshold value with respect to the vibrating object of this disclosure. It is a figure which shows the maintenance process of the said spectrum threshold value of this disclosure. It is a figure which shows the spectrum threshold value setting process and the moving object detection process of this disclosure.

Embodiments of the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are examples of the embodiments of the present disclosure, and the present disclosure is not limited to the following embodiments.

(Configuration of moving object detection system)
FIG. 1 shows the configuration of the moving object detection system of the present disclosure. The moving object detection system S includes an FMCW radar transmission / reception device 1 and a moving object detection device 2. The moving object detection device 2 includes a beat signal acquisition unit 21, a difference signal calculation unit 22, a frequency spectrum calculation unit 23, a spectrum threshold value determination unit 24, and a moving object target output unit 25, and is shown in FIGS. 5 and 10. This can be achieved by installing a target detection program on the computer.

The FMCW radar transmission / reception device 1 irradiates the target T with the transmission signal of the FMCW radar, and receives the reflection signal of the FMCW radar from the target T. The beat signal acquisition unit 21 acquires a beat signal between the transmission / reception signals of the FMCW radar (step S1 in FIG. 5). The difference signal calculation unit 22 calculates a difference signal between beat signals having different transmission / reception cycles (time-adjacent transmission / reception cycles in FIGS. 2 to 4) (step S2 in FIG. 5). The frequency spectrum calculation unit 23 calculates the frequency spectrum of the difference signal (step S3 in FIG. 5). The moving target output unit 25 detects the distance of the target T based on the peak frequency of the frequency spectrum.

The difference signal and frequency spectrum of the stationary object of the present disclosure are shown in FIG. Here, examples of the stationary object marker include a stationary object, a ground clutter, and the like. The beat signals of the first and second cycles have the same frequency and the same phase. The difference signal between the first and second cycles is canceled. The frequency spectrum between the first and second cycles has no peak at any frequency. In this way, in the frequency spectrum between different transmission / reception cycles, the frequency peak of the stationary object is removed, but the frequency component of white noise (natural noise) is maintained.

The difference signal and frequency spectrum of the moving object of the present disclosure are shown in FIG. Here, examples of moving objects include walking people and moving vehicles. The beat signals of the first, second (2, 3) cycles have different frequencies. The difference signal between the first, second (2, 3) cycles is not canceled. The frequency spectrum between the first, second (2, 3) periods has a peak at one (other) frequency. As described above, in the frequency spectrum between different transmission / reception cycles, the frequency peak of the moving object is maintained, but the frequency component of white noise (natural noise) is also maintained.

The difference signal and frequency spectrum of the vibration target (environmental noise) of the present disclosure are shown in FIG. Here, examples of the vibration target (environmental noise) include an indoor fan, a ventilation fan, a cooling fan, an outdoor air conditioner, a building, a tree, a flag, a banner, an engine, and the like. The beat signals of the first, second (2, and 3) periods have the same frequency and different phases (the vibration target (environmental noise) has an invariant distance but oscillates and rotates). The difference signal between the first, second (2, 3) cycles is not canceled. The frequency spectrum between the first, second (2, 3) periods has a peak at a certain (same) frequency. As described above, in the frequency spectrum between different transmission / reception cycles, the frequency peak of the vibration target (environmental noise) is maintained, but the frequency component of the white noise (natural noise) is also maintained.

Therefore, the vibration target (environment) is based on a frequency having a larger frequency spectrum than the variable spectrum threshold (time change according to the vibration target) having a peak at the frequency corresponding to the distance of the vibration target (environmental noise). The distance of the moving object is output without outputting the distance of noise).

Then, the spectral intensity is white noise (natural noise) based on the frequency whose frequency spectrum is larger than the variable spectrum threshold (time change according to the white noise) having a flat portion at the frequency corresponding to the white noise (natural noise). ) Output the distance of a higher moving object.

(Procedure for moving object detection process)
FIG. 5 shows the procedure of the moving object detection process of the present disclosure. FIG. 6 shows the moving object detection process and the spectrum threshold setting process of the present disclosure. FIG. 7 shows the non-detection process of any of the target distances in the present disclosure. FIG. 8 shows the output processing of the target distance of the moving object of the present disclosure. FIG. 9 shows the non-output processing of the target distance of the vibrating object of the present disclosure. The spectrum threshold setting process will be described in detail later.

From time t ₀ to t ₂ , no moving target has appeared, and no vibrating target (environmental noise) has appeared. The frequency spectrum has no frequency peak (see left column of FIG. 7). The variable spectral threshold has a flat portion at a frequency corresponding to white noise (natural noise) (see FIGS. 11 and 12). The spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum than the variable spectrum threshold value does not appear continuously n times (step S4, NO). The moving target output unit 25 does not detect the distance of any target (step S8).

_At times t2 to t3 _, moving targets began to appear, but vibration targets (environmental noise) did not appear. The frequency spectrum has a frequency peak corresponding to the distance of the moving object (see the left column of FIG. 8). The variable spectral threshold has a flat portion at a frequency corresponding to white noise (natural noise) (see the upper part of FIG. 14). The spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum than the variable spectrum threshold value does not appear continuously n times (step S4, NO). The moving target output unit 25 does not detect the distance of any target in order to avoid instantaneous false alarm detection of the moving target as much as possible (step S8).

_At times t3 to t5 _, a moving target appears, but a vibrating target (environmental noise) does not appear. The frequency spectrum has a frequency peak corresponding to the distance of the moving object (see the left column of FIG. 8). The variable spectral threshold has a flat portion at a frequency corresponding to white noise (natural noise) (see the upper part of FIG. 14). The spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum than the variable spectrum threshold value appears n times in succession (step S4, YES), and determines that the frequency has changed over time (step S5). , YES). The moving object target output unit 25 determines that the distance of the moving object target may be output (step S6).

_At times _t5 to _t7 , as with times _t0 to t2, no moving target and no vibrating target (environmental noise) have appeared. Therefore, the same processing as at times t ₀ to t ₂ is executed.

At times _t7 to _t8 , vibration targets (environmental noise) began to appear, but moving targets did not appear. The frequency spectrum has a frequency peak corresponding to the distance of the vibration target (environmental noise) (see the left column of FIG. 9). The variable spectral threshold has a flat portion at a frequency corresponding to white noise (natural noise) (see the left column of FIG. 13). The spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum than the variable spectrum threshold value does not appear continuously n times (step S4, NO). The moving target output unit 25 does not detect the distance of any target in order to avoid the false alarm detection of the momentary vibrating target (environmental noise) as much as possible (step S8).

_At times _t8 to t9, a vibrating target (environmental noise) appears, but a moving target does not appear. The frequency spectrum has a frequency peak corresponding to the distance of the vibration target (environmental noise) (see the right column of FIG. 9). The variable spectral threshold has a peak at the frequency corresponding to the distance of the vibrating target (environmental noise), but does not follow the spectral intensity of the vibrating target (environmental noise) (see the right column of FIG. 9). The spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum has appeared n times in succession as compared with the variable spectrum threshold value (step S4, YES), but determines that the frequency has not changed with time (step S5). , NO). The moving object target output unit 25 determines that the distance of the vibrating object target (environmental noise) should not be output (step S7).

At times t ₉ to t ₁₄ , vibration targets (environmental noise) appear, and moving targets will be described in detail later. The frequency spectrum has a frequency peak corresponding to the distance of the vibration target (environmental noise) (see the right column of FIG. 7). The variable spectral threshold has a peak at a frequency corresponding to the distance of the vibrating target (environmental noise) and follows the spectral intensity of the vibrating target (environmental noise) (see the right column of FIG. 13). The spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum than the variable spectrum threshold value does not appear continuously n times (step S4, NO). The moving target output unit 25 does not detect the distance of any target (step S8).

At times t ₁₀ to t ₁₁ , moving targets have begun to appear, and vibration targets (environmental noise) have been described in detail earlier. The frequency spectrum has a frequency peak corresponding to the distance of the moving object (see the right column of FIG. 8). The variable spectral threshold has a peak at the frequency corresponding to the distance of the vibration target (environmental noise) (see the lower part of FIG. 14). The spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum than the variable spectrum threshold value does not appear continuously n times (step S4, NO). The moving target output unit 25 does not detect the distance of any target in order to avoid instantaneous false alarm detection of the moving target as much as possible (step S8).

At times t ₁₁ to t ₁₂ , moving targets have appeared, and vibration targets (environmental noise) have been described in detail above. The frequency spectrum has a frequency peak corresponding to the distance of the moving object (see the right column of FIG. 8). The variable spectral threshold has a peak at the frequency corresponding to the distance of the vibration target (environmental noise) (see the lower part of FIG. 14). The spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum than the variable spectrum threshold value appears n times in succession (step S4, YES), and determines that the frequency has changed over time (step S5). , YES). The moving object target output unit 25 determines that the distance of the moving object target may be output (step S6).

At times t ₁₄ to t ₁₅ , as at times t ₀ to t ₂ , no moving target and no vibrating target (environmental noise) appeared. Therefore, the same processing as at times t ₀ to t ₂ is executed.

In this way, when detecting the distance of a moving object using the FMCW radar, the variable spectral threshold value for the vibrating object (environmental noise) is set to an appropriate large value, and the sensitivity of the FMCW radar is increased. It is possible to avoid false alarm detection of vibration target (environmental noise).

Then, it is possible to avoid false alarm detection of the vibrating object (environmental noise) until the variable spectrum threshold value for the vibrating object (environmental noise) is set to an appropriate large value.

Furthermore, when detecting the distance of a moving object using the FMCW radar, the variable spectral threshold for white noise (natural noise) is set to an appropriate small value, the sensitivity of the FMCW radar is increased, and then white noise (white noise) ( It is possible to avoid false alarm detection (natural noise).

(Procedure for spectrum threshold setting process)
The procedure of the spectrum threshold setting process of the present disclosure is shown in FIG. FIG. 6 shows the moving object detection process and the spectrum threshold setting process of the present disclosure. FIG. 11 shows the processing for setting the spectral threshold value for the white noise of the present disclosure. FIG. 12 shows an update process of the spectral threshold value for the white noise of the present disclosure. FIG. 13 shows the processing for setting the spectral threshold value for the vibrating object of the present disclosure. FIG. 14 shows the above-mentioned maintenance processing of the spectral threshold value of the present disclosure. FIG. 15 shows the spectrum threshold setting process and the moving object detection process of the present disclosure. The moving object detection process has been described in detail earlier.

At times t ₀ to t ₁ , the spectrum threshold value determination unit 24 initially sets a fixed spectrum threshold value having a flat portion at a frequency corresponding to white noise (natural noise) (step S11).

At times t ₀ to t ₃ , the spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum than the spectrum threshold value does not appear continuously n times (steps S12, NO). The spectrum threshold determination unit 24 follows the change in the intensity of the time integration within each transmission / reception cycle of the signal intensity of the difference signal, or changes the intensity of the frequency spectrum at all frequencies corresponding to white noise (natural noise). The variable spectrum threshold having a flat portion at the frequency corresponding to the white noise (natural noise) is updated according to (step S16).

In the left column of FIG. 11, the spectrum threshold value determination unit 24 moves and averages the time integral of the signal strength of the difference signal in each transmission / reception cycle in a plurality of transmission / reception cycles. In the right column of FIG. 11, the spectrum threshold determination unit 24 multiplies the moving average in the plurality of transmission / reception cycles for the time integration by the conversion coefficient from the time domain to the frequency domain.

In FIG. 11, the spectrum threshold value determination unit 24 updates the variable spectrum threshold value having a flat portion at a frequency corresponding to white noise (natural noise) by conversion from the time domain. Alternatively, the spectral threshold determination unit 24 may update the variable spectral threshold having a flat portion at a frequency corresponding to white noise (natural noise) directly in the frequency domain.

The moving average width of the above time integral is preferably set short when the speed of the moving object is high, and is preferably set long when the speed of the moving object is low. The frequency range of the variable spectral threshold is preferably set according to the Nyquist frequency. It is desirable that the magnitude of the variable spectrum threshold is set according to the desired sensitivity of the FMCW radar. Specifically, the magnitude of the variable spectrum threshold is preferably set to a conversion value ± x% (x: large) from the time domain when there is no moving target, and when there is a moving target. , It is desirable to set the conversion value from the time domain ± y% (y: small).

At times t ₃ to t ₅ , the spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum appears n times in succession as compared with the variable spectrum threshold value (step S12, YES), and changes with time. (Step S13, YES). The spectrum threshold determination unit 24 does not follow the intensity change of the frequency spectrum at a frequency that changes with time corresponding to the distance of the moving object, and has a variable portion having a flat portion at the frequency corresponding to the white noise (natural noise) in step S16. The spectral threshold is maintained (step S14, see the upper part of FIG. 14). Here, the time constant at which the variable spectrum threshold value follows the time change of the frequency peak intensity is set longer when the frequency peak intensity increases than when the frequency peak intensity decreases. Therefore, even if a moving object appears, the variable spectral threshold does not follow the time change of the frequency peak intensity.

_At times t5 to _t8 , the spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum than the variable spectrum threshold value does not appear continuously n times (steps S12, NO). The spectrum threshold determination unit 24 updates the variable spectrum threshold having a flat portion at a frequency corresponding to white noise (natural noise) by conversion from the time domain or directly in the frequency domain (step S16, FIG. 11). And see FIG. 12). Specifically, the spectral threshold determination unit 24 detects an increase in the intensity of white noise ₍ natural noise) at time _t4 , and updates the variable spectral threshold of white noise (natural noise) at time t6.

_At times _t8 to t9, the spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum appears n times in succession as compared with the variable spectrum threshold value (step S12, YES), but changes with time. It is determined that the frequency is not present (step S13, NO). The spectrum threshold determination unit 24 has a peak at a frequency corresponding to the vibration target (environmental noise), following a change in the intensity of the frequency spectrum at a frequency corresponding to the distance of the vibration target (environmental noise) and not changing with time. A variable spectral threshold is set (step S15, see FIG. 13). Here, the time constant at which the variable spectrum threshold value follows the time change of the frequency peak intensity is set longer when the frequency peak intensity increases than when the frequency peak intensity decreases. Therefore, when a vibration target (environmental noise) appears, the variable spectral threshold value follows the time change of the frequency peak intensity.

At times t ₉ to t ₁₁ and t ₁₂ to t ₁₄ (time t ₁₁ to t ₁₂ will be described in detail shortly), the spectrum threshold value determination unit 24 has a frequency having a larger frequency spectrum than the variable spectrum threshold value. However, it is determined that it does not appear n times in a row (step S12, NO). The spectral threshold determination unit 24 maintains a variable spectral threshold having a peak at a frequency corresponding to the vibration target (environmental noise) in step S15 (see step S17, FIG. 13).

At times t ₁₁ to t ₁₂ , the spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum appears n times in succession as compared with the variable spectrum threshold value (step S12, YES), and changes with time. (Step S13, YES). The spectrum threshold determination unit 24 does not follow the intensity change of the frequency spectrum at the frequency that changes with time corresponding to the distance of the moving object, and has a peak at the frequency corresponding to the vibration target (environmental noise) in step S15. Maintain the spectral threshold (step S14, see bottom of FIG. 14). Here, the time constant at which the variable spectrum threshold value follows the time change of the frequency peak intensity is set longer when the frequency peak intensity increases than when the frequency peak intensity decreases. Therefore, even if a moving object appears, the variable spectral threshold does not follow the time change of the frequency peak intensity.

At times t ₁₄ to t ₁₅ , the spectrum threshold value determination unit 24 determines that a frequency having a larger frequency spectrum than the variable spectrum threshold value does not appear continuously n times (steps S12, NO). The spectrum threshold determination unit 24 updates the variable spectrum threshold having a flat portion at a frequency corresponding to white noise (natural noise) by conversion from the time domain or directly in the frequency domain (step S16, FIG. 11). And see FIG. 12). Specifically, the spectral threshold determination unit 24 detects an increase in the intensity of white noise ₍ natural noise) at time t13 and updates the variable spectral threshold of white noise ₍ natural noise) at time t15.

In this way, the variable spectral threshold value for the vibration target (environmental noise) can be set to an appropriate large value according to the time change of the frequency peak of the vibration target (environmental noise).

Then, the variable spectral threshold value for white noise (natural noise) can be set to an appropriate small value according to the time change of the intensity of white noise (natural noise).

In the upper part of FIG. 15, when only white noise (natural noise) is present, the spectrum threshold setting process and the moving object detection process are tested. In the left column, the variable spectral threshold having a flat portion at the frequency corresponding to the white noise (natural noise) is set larger than the calculated intensity of the white noise (natural noise). In the right column, neither target distance is detected.

In the middle part of FIG. 15, when the intensity of the vibrating object (environmental noise) is low, the spectrum threshold setting process and the moving object detection process are tested. In the left column, the variable spectral threshold having a peak at the frequency corresponding to the vibrating object (environmental noise) is set larger than the intensity calculated value of the vibrating object (environmental noise). In the right column, the distance of the moving object is detected and output, but the distance of the vibrating object (environmental noise) is not output even if it is detected.

In the lower part of FIG. 15, when the intensity of the vibrating object (environmental noise) is high, the spectrum threshold setting process and the moving object detection process are tested. In the left column, the calculated intensity of the vibrating object (environmental noise) is calculated to be larger than the variable spectral threshold having a peak at the frequency corresponding to the vibrating object (environmental noise). In the right column, even if the distance of the vibrating object (environmental noise) is detected both during and after the formation of the variable spectrum threshold value, it is not output.

The moving object detection device, the moving object detection system, the moving object detection program, and the moving object detection method of the present disclosure remove stationary objects, white noise (natural noise), and vibrating objects (environmental noise). Therefore, it is possible to detect the distance of a moving object such as a walking person or a moving vehicle.

S: Moving object detection system T: Target 1: FMCW radar transmission / reception device 2: Moving object detection device 21: Beat signal acquisition unit 22: Difference signal calculation unit 23: Frequency spectrum calculation unit 24: Spectrum threshold value determination unit 25: Moving object indicator output unit

Claims (8)

A beat signal acquisition unit that acquires beat signals between transmission and reception signals of the FMCW radar,
A difference signal calculation unit that calculates a difference signal between the beat signals having different transmission / reception cycles,
A frequency spectrum calculation unit that calculates the frequency spectrum of the difference signal,
A spectrum threshold value determination unit that determines the magnitude relationship between the frequency spectrum and the spectrum threshold value having a peak at the frequency corresponding to the distance of the vibration target at each frequency.
A moving object output unit that outputs the distance of the moving object without outputting the distance of the vibrating object based on the frequency whose frequency spectrum is larger than the spectrum threshold.
A moving object detection device characterized by being equipped with. The spectrum threshold determination unit does not follow the intensity change of the frequency spectrum at a frequency that changes with time corresponding to the distance of the moving object, and the frequency at a frequency corresponding to the distance of the vibration target and does not change with time. The moving object detection device according to claim 1, wherein the spectral threshold value is set according to a change in the intensity of the spectrum. The moving object target output unit is not based on a frequency whose frequency spectrum is larger than the spectral threshold but does not change with time, and is based on a frequency at which the frequency spectrum is larger than the spectral threshold and changes with time. The moving object detection device according to claim 1 or 2, wherein the frequency is output. The spectrum threshold value determination unit determines the magnitude relationship at each frequency between the frequency spectrum and the spectrum threshold value having a flat portion at a frequency corresponding to white noise.
The moving object target output unit is characterized in that it outputs a distance of the moving object whose spectral intensity is higher than that of the white noise based on a frequency whose frequency spectrum is larger than the spectrum threshold. The moving object detection device described in any of the above. The spectrum threshold determination unit follows the change in the intensity of the time integration of the signal strength of the difference signal in each transmission / reception cycle, or changes the intensity of the frequency spectrum at all frequencies corresponding to the white noise. The moving object detection device according to claim 4, wherein the spectral threshold value is set accordingly. A moving object detection system comprising the moving object detection device according to any one of claims 1 to 5 and the radar transmission / reception device of the FMCW radar. A beat signal acquisition step for acquiring a beat signal between transmission and reception signals of the FMCW radar, and
A difference signal calculation step for calculating a difference signal between the beat signals having different transmission / reception cycles, and
The frequency spectrum calculation step for calculating the frequency spectrum of the difference signal, and
A spectrum threshold value determination step for determining a magnitude relationship between the frequency spectrum and a spectrum threshold value having a peak at a frequency corresponding to the distance of a vibrating object at each frequency.
A moving target output step that outputs the distance of the moving target without outputting the distance of the vibrating target based on the frequency at which the frequency spectrum is larger than the spectral threshold.
A moving object detection program to make the computer execute in order. A beat signal acquisition step for acquiring a beat signal between transmission and reception signals of the FMCW radar, and
A difference signal calculation step for calculating a difference signal between the beat signals having different transmission / reception cycles, and
The frequency spectrum calculation step for calculating the frequency spectrum of the difference signal, and
A spectrum threshold value determination step for determining a magnitude relationship between the frequency spectrum and a spectrum threshold value having a peak at a frequency corresponding to the distance of a vibrating object at each frequency.
A moving target output step that outputs the distance of the moving target without outputting the distance of the vibrating target based on the frequency at which the frequency spectrum is larger than the spectral threshold.
A moving object detection method, characterized in that

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