JP2020041818A - Radar device and object determination method - Google Patents

Abstract

To provide a radar device and an object determination method capable of discriminating a pedestrian and ground clutter with high accuracy.SOLUTION: The radar device 1 includes a reception unit 20, a generation unit 35, and a determination unit 36. The reception unit receives a reflected wave of a transmission wave reflected by an object as a reception signal. The generation unit generates a power spectrum for two dimensions of a distance direction corresponding to distance from the object and a speed direction corresponding to relative velocity of the object from the reception signal received by the receiving unit. The determination unit detects a peak from the power spectrum generated by the generation unit, and determines whether the peak is due to a pedestrian or not based on the peak and the power spectrum in the vicinity of the peak.SELECTED DRAWING: Figure 1

Description

  An embodiment of the present disclosure relates to a radar device and an object determination method.

  2. Description of the Related Art Conventionally, a radar apparatus receives a reflected wave of a transmission wave reflected by an object as a reception signal, and obtains a distance to the object, a relative speed, a direction of existence, and the like by analyzing the reception signal (for example, see Patent Document 1). ).

JP-A-2006-3873

  In particular, with respect to an object to be controlled by a vehicle (sometimes called a target), there has been a demand to further determine the type of the target (whether or not it is a pedestrian or not). However, with the conventional technology, it has been difficult to distinguish a pedestrian from road clutter with high accuracy.

  An aspect of the embodiment is made in view of the above, and an object of the invention is to provide a radar apparatus and an object determination method capable of determining a pedestrian and a road clutter with high accuracy.

  A radar device according to an aspect of an embodiment includes a reception unit, a generation unit, and a determination unit. The receiving unit receives a reflected wave of the transmission wave reflected by the object as a reception signal. The generation unit generates a two-dimensional power spectrum in a distance direction corresponding to a distance to the object and a speed direction corresponding to a relative speed to the object from the reception signal received by the reception unit. The determining unit detects a peak from the power spectrum generated by the generating unit, and determines whether the peak is caused by a pedestrian based on the peak and a power spectrum near the peak.

  According to the radar device and the object determination method according to one aspect of the embodiment, it is possible to determine a pedestrian and a road surface clutter with high accuracy.

FIG. 1 is a block diagram of the radar device according to the embodiment. FIG. 2 is a diagram illustrating an example of a relationship among a transmission frequency, a reception frequency, and a beat frequency according to the embodiment. FIG. 3 is a diagram illustrating a result of performing a distance FFT process on the beat signal according to the embodiment. FIG. 4 is a diagram illustrating processing contents of a second processing unit according to the embodiment. FIG. 5 is an explanatory diagram illustrating an example of a center cell and a cell near a peak according to the embodiment. FIG. 6A is an explanatory diagram illustrating characteristics in the speed direction of the peak vicinity data according to the embodiment. FIG. 6B is an explanatory diagram illustrating characteristics in the distance direction of the peak vicinity data according to the embodiment. FIG. 6C is an explanatory diagram illustrating the tendency of the characteristic of the peak vicinity data according to the embodiment. FIG. 7 is an explanatory diagram illustrating the tendency of the position of the center of gravity in the power speed direction according to the embodiment. FIG. 8 is an explanatory diagram illustrating an example of the definition of the power relative value according to the embodiment. FIG. 9A is an explanatory diagram illustrating the tendency of the power relative value of the data near the peak that is 1 bin away from the target peak in the distance direction according to the embodiment. FIG. 9B is an explanatory diagram illustrating the tendency of the power relative value of the data near the peak that is 2 bins away from the target peak in the distance direction according to the embodiment. FIG. 10 is an explanatory diagram illustrating the tendency of the power relative value of the data near the peak adjacent to the target peak in the oblique direction according to the embodiment. FIG. 11A is an explanatory diagram illustrating the tendency of the power relative value of the data near the peak that is 1 bin away from the target peak in the speed direction according to the embodiment. FIG. 11B is an explanatory diagram illustrating the tendency of the power relative value of the data near the peak that is 2 bins away from the target peak in the speed direction according to the embodiment. FIG. 12 is a flowchart illustrating an example of a process performed by the signal processing unit of the radar device according to the embodiment.

  Hereinafter, embodiments of a radar device and an object determination method will be described in detail with reference to the accompanying drawings. The present invention is not limited by the embodiments described below. FIG. 1 is a block diagram of a radar device 1 according to the embodiment.

  The radar device 1 according to the embodiment is mounted on a vehicle, and detects an object (hereinafter, referred to as a “target”) around the vehicle by FCM (Fast Chirp Modulation). The FCM method is a method of outputting a transmission wave in which a plurality of chirp waves whose frequencies continuously change are repeated, and detecting a distance and a relative speed to a target existing within a detection range.

  Specifically, in the FCM method, a reflected wave of a transmitted wave reflected by a target is received by a plurality of receiving antennas as a received signal, and a beat signal generated from the received reflected wave and the transmitted wave is subjected to a second signal. A distance and a relative speed with respect to the target are detected by performing a dimensional fast Fourier transform (Fast Fourier Transform) process (hereinafter sometimes referred to as a two-dimensional FFT process).

  Note that the two-dimensional FFT processing is performed by performing two FFT processings of a distance FFT processing in a distance direction corresponding to a distance to the target and a speed FFT processing in a speed direction corresponding to a relative speed to the target. is there.

  The radar device 1 is connected to a vehicle control device 2 as shown in FIG. The vehicle control device 2 controls a vehicle such as a PCS (Pre-crash Safety System) or an AEB (Advanced Emergency Braking System) based on the detection result of the target by the radar device 1. The radar device 1 may be used for various purposes other than the on-vehicle radar device (for example, monitoring an airplane or a ship).

  The radar device 1 includes a transmitting unit 10, a receiving unit 20, and a processing unit 30. The transmission unit 10 includes a signal generation unit 11, an oscillator 12, and a transmission antenna 13. The signal generation unit 11 generates a modulation signal whose voltage changes in a sawtooth waveform and supplies the modulation signal to the oscillator 12. The oscillator 12 generates a chirp signal based on the modulation signal generated by the signal generation unit 11, and outputs the generated chirp signal to the transmission antenna 13.

  The transmission antenna 13 converts a chirp signal input from the oscillator 12 into a transmission wave, and outputs the transmission wave to the outside of the vehicle. The transmission wave output from the transmission antenna 13 has a waveform in which a plurality of chirp waves are repeated. The transmission wave transmitted from the transmission antenna 13 to the front of the vehicle is reflected by the target and becomes a reflected wave.

  The receiving unit 20 includes a plurality of receiving antennas 21 forming an array antenna, a mixer 22 provided for each antenna 21, and an A / D converter 23 provided for each mixer 22. Each receiving antenna 21 receives a reflected wave from the target as a received wave, converts the received wave into a received signal, and outputs the signal to the mixer 22. Although the number of receiving antennas 21 shown in FIG. 1 is four, it may be three or less or five or more. In particular, in the present embodiment, since it is not necessary to obtain the direction of the target, only one receiving antenna may be used.

  The reception signal output from each reception antenna 21 is input to the mixer 22 after being amplified by an amplifier (for example, a low noise amplifier) not shown. The mixer 22 mixes the chirp signal and a part of the received signal, removes unnecessary signal components, generates a beat signal, and outputs the beat signal to the A / D converter 23.

Accordingly, a beat frequency f _SB (= f) which is a difference between the frequency f _ST of the chirp signal (hereinafter referred to as transmission frequency f _ST ) and the frequency f _{SR of the} reception signal (hereinafter referred to as reception frequency f _SR ). beat signal having a _ST -f _SR) is generated. The beat signal generated by the mixer 22 is converted to a digital signal by the A / D converter 23 and then output to the processing unit 30.

FIG. 2 is a diagram illustrating an example of a relationship among the transmission frequency f _ST , the reception frequency f _SR, and the beat frequency f _SB . As shown in FIG. 2, a beat signal is generated for each chirp wave. Here, the beat signal obtained by the first chirp wave is “B1”, the beat signal obtained by the second chirp wave is “B2”, and the beat signal obtained by the nth chirp wave is “Bn”. "

In the example illustrated in FIG. 2, the transmission frequency f _ST increases with time from the reference frequency f0 with a gradient θ (= (f1−f0) / Tm) for each chirp wave, and reaches the maximum frequency f1. It has a sawtooth waveform (so-called up-chirp) that returns to the reference frequency f0 in a short time.

The transmission frequency _{f ST} is reached in a short time from the reference frequency f0 to the maximum frequency f1 for each chirp wave, decreases with a slope with the take up frequency f1 in the time θ (= (f0-f1) / Tm) A sawtooth waveform (a so-called down chirp) may be used.

  Returning to the description of FIG. 1, the processing unit 30 will be described. The processing unit 30 includes a transmission control unit 31 and a signal processing unit 32. The signal processing unit 32 includes a first processing unit 33, a second processing unit 34, a generation unit 35, a determination unit 36, and an output unit 37.

  The processing unit 30 is, for example, a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output port, and the like, and controls the entire radar device 1.

  The processing unit 30 includes a transmission control unit 31 and a signal processing unit 32 that function when the CPU of the microcomputer reads a program stored in the ROM and executes the program using the RAM as a work area.

  Note that at least a part or all of the transmission control unit 31 and the signal processing unit 32 may be configured by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

  The transmission control unit 31 controls the signal generation unit 11 of the transmission unit 10, and causes the signal generation unit 11 to output a modulated signal whose voltage changes in a saw-tooth shape to the oscillator 12. As a result, a chirp signal whose frequency changes over time is output from the oscillator 12 to the transmitting antenna 13.

  The signal processing unit 32 performs two-dimensional FFT processing (distance FFT processing and speed FFT processing) on the beat signal output from each A / D converter 23. The signal processing unit 32 calculates the distance, the relative speed (the relative speed in the vertical direction and the relative speed in the horizontal direction) and the azimuth of the target based on the result of the two-dimensional FFT process, and calculates the calculated distance and From the relative speed, for example, it is determined whether the target is a pedestrian. Hereinafter, processing of each unit of the signal processing unit 32 will be described.

  The first processing unit 33 of the signal processing unit 32 generates a frequency spectrum for each receiving antenna 21 by performing a distance FFT process on each of the beat signals input from each of the A / D converters 23. Specifically, the first processing unit 33 performs a distance FFT process for each distance [bin] fr (fr1 to frm) for each beat signal. Here, the result of the distance FFT processing will be specifically described with reference to FIG.

  FIG. 3 is a diagram illustrating a result of performing a distance FFT process on a beat signal. In the frequency spectrum shown in FIG. 3, the horizontal axis represents the distance [bin] (frequency), and the vertical axis represents the magnitude (peak magnitude) of the power spectrum (power [dB]). In the example shown in FIG. 3, it is assumed that a peak appears only at the distance [bin] fr10.

  Here, the frequency of the beat signal increases and decreases in proportion to the distance between the target and the radar device 1. For this reason, the first processing unit 33 performs the distance FFT processing on the beat signal, thereby changing the peak (power is equal to or more than a predetermined value) appearing at the distance [bin] fr corresponding to the distance to the target in the distance direction. Obtain as the target peak of

  The first processing unit 33 periodically performs the distance FFT processing on each beat signal input from the four A / D converters 23 in a predetermined cycle. The first processing unit 33 outputs the result of the distance FFT processing to the second processing unit 34.

  The second processing unit 34 performs a speed FFT process on the result of the distance FFT process in the first processing unit 33. The speed FFT process is to perform the second FFT process for each speed [bin] fv for each distance [bin] fr of the frequency spectrum that is the result of the distance FFT process. Thereby, as a result of the speed FFT processing, a peak appears at the speed [bin] fv corresponding to the relative speed of the target.

  The second processing unit 34 uses the Doppler component of the received signal generated when the relative speed of the target is not zero. Specifically, the second processing unit 34 detects a change in the phase of the peak in the frequency spectrum of the beat signal. Here, the processing content of the second processing unit 34 will be described with reference to FIG.

  FIG. 4 is a diagram illustrating processing contents of the second processing unit 34. FIG. 4 shows a frequency spectrum of an arbitrary one of the plurality of receiving antennas 21 arranged in time series. FIG. 4 shows an example of a result of the distance FFT processing of the temporally continuous beat signals B1 to B8 and a phase change of a peak between the beat signals B1 to B8. In the example shown in FIG. 4, there is a peak at the distance [bin] fr10 between the beat signals B1 to B8, and the phase of the peak changes.

  Here, when the relative speed between the target and the radar apparatus 1 is not zero, a change in phase according to the Doppler frequency appears at the peak of the distance [bin] fr10 corresponding to the same target between the beat signals B1 to B8.

  The second processing unit 34 performs frequency FFT processing by arranging the frequency spectrums obtained by performing the distance FFT processing periodically in a predetermined cycle in a time series, so that a peak appears at a frequency (velocity [bin]) with respect to the Doppler frequency. Frequency spectrum to be obtained as a target peak in the velocity direction. The second processing unit 34 outputs the result of the speed FFT processing to the generation unit 35.

  Returning to FIG. 1, the generation unit 35 and the determination unit 36 will be described. Based on the result of the speed FFT processing input from the second processing unit 34, the generation unit 35 uses a two-dimensional orthogonal coordinate system (hereinafter, referred to as a two-dimensional coordinate system) with the distance direction as the first axis and the speed direction as the second axis. Described below).

  The determining unit 36 calculates the distance to the target, the relative speed, and the angle (azimuth) based on the power spectrum generated by the generating unit 35. Then, the determination unit 36 determines, for example, whether the target is a pedestrian from the calculated distance and relative speed. Then, the determination unit 36 outputs the calculation result and the determination result to the output unit 37.

  Note that the angle estimation by the determination unit 36 is performed using a predetermined estimation method such as ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques), DBF (Digital Beam Forming), or MUSIC (Multiple Signal Classification). Will be

  The output unit 37 outputs various information to the vehicle control device 2. For example, the output unit 37 outputs target information on the detected target to the vehicle control device 2. The target information includes, for example, a distance, a relative speed, and an angle of the target determined as a pedestrian by the determination unit 36.

Here, the determination unit of the general radar device determines whether the target is a pedestrian based on the target peak in the distance direction and the target peak in the speed direction. For example, a general discriminating unit, for a target peak in the distance direction, because pedestrians tend to have higher power than road clutter, if the power is equal to or greater than a predetermined threshold, the target is regarded as a pedestrian. Determine.
However, sometimes the power of the road clutter in the distance direction exceeds the threshold. In such a case, the determination unit may erroneously determine the road surface as a pedestrian.

  In addition, since the pedestrian moves but does not move on the road surface with respect to the target peak in the speed direction, the general determination unit determines that the ground speed obtained by subtracting the speed component of the vehicle from the relative speed with the target is equal to or greater than a predetermined threshold. If, the target is determined to be a pedestrian. However, such a determination unit may erroneously determine a pedestrian moving at a ground speed less than the threshold as a road surface.

  As described above, the general determination unit determines whether or not the target is a pedestrian based on the target peak in the distance direction and the target peak in the speed direction. It was difficult to determine with.

  Note that the general determination unit can improve the accuracy of the determination by determining whether or not the target is a pedestrian based on the target peak continuously acquired in the processing of a plurality of cycles. However, this increases the time required to determine whether or not the person is a pedestrian.

  Therefore, the determination unit 36 according to the embodiment determines whether the target is a pedestrian by using the fact that the characteristics of the power spectrum near the target peak in the two-dimensional coordinate system are different between the pedestrian and the road clutter. I do. Thereby, the radar apparatus 1 can quickly and at a high angle determine whether or not the target is a pedestrian from the instantaneous value acquired in one cycle of processing.

  Specifically, the determination unit 36 defines a center cell at a position where the target peak is detected in the two-dimensional coordinate system, and a power spectrum near the peak around the center cell (hereinafter, referred to as peak vicinity data). Is defined as a cell in the vicinity of the peak which is a position for detecting.

  FIG. 5 is an explanatory diagram illustrating an example of a center cell and a cell near a peak according to the embodiment. As illustrated in FIG. 5, the determination unit 36 has, for example, a horizontal axis representing a relative speed with respect to the target (hereinafter, referred to as speed) and a vertical axis representing a distance from the target (hereinafter, referred to as distance). In the two-dimensional coordinate system, a center cell (7) is defined at a position where the target peak is detected.

  Then, the determination unit 36 defines the neighboring cells (1) to (6) and (8) to (13) around the center cell (7). For example, in the distance direction, the determination unit 36 determines that the neighbor cell (3) is 1 [bin] away from the center cell (7) on the positive side, the neighbor cell (1) is 2 [bin] on the positive side, and the neighbor cell (1) on the negative side. A neighbor cell (11) separated by 1 [bin] and a neighbor cell (13) separated by 2 [bin] on the negative side are defined.

  Further, in the velocity direction, the discriminating unit 36 determines that the neighboring cell (6) is 1 [bin] away from the center cell (7) on the positive side, the neighboring cell (5) is 2 [bin] away on the positive side, and the negative cell is A neighbor cell (8) separated by 1 [bin] and a neighbor cell (9) separated by 2 [bin] on the negative side are defined. Further, the determination unit 36 defines four neighboring cells (2), (4), (10), and (12) adjacent to the center cell (7) in the oblique direction.

  Then, when detecting the target peak corresponding to the target from the power spectrum generated by the generation unit 35, the determination unit 36 determines each of the neighboring cells (1) to (6) of the center cell (7) where the target peak is detected. ) And (8) to (13) to detect near-peak data.

  At this time, the peak vicinity data has different characteristics depending on whether the received signal is a reflected wave from a pedestrian or a road clutter. Here, with reference to FIG. 6A, FIG. 6B, and FIG. 6C, the characteristics of the data near the peak and the tendency of the characteristics will be described.

  FIG. 6A is an explanatory diagram illustrating characteristics in the speed direction of the peak vicinity data according to the embodiment. FIG. 6B is an explanatory diagram illustrating characteristics in the distance direction of the peak vicinity data according to the embodiment. FIG. 6C is an explanatory diagram illustrating the tendency of the characteristic of the peak vicinity data according to the embodiment.

  As shown in the right diagram of FIG. 6A, in the case of road surface clutter, the power of the data near the peak in the speed direction is characterized in that it decreases as the road surface is stationary and moves away from the center cell (7) in the speed direction. As a result, in the case of road surface clutter, the peak shape of the data near the peak does not have a spread in the velocity direction and has a shape symmetric with respect to the target peak.

  On the other hand, as shown in the left diagram of FIG. 6A, in the case of a pedestrian, the power of the data near the peak in the speed direction is one even when the pedestrian moves away from the center cell (7) in the speed direction. Has a characteristic that it does not decrease in the positive speed direction). As a result, in the case of a pedestrian, the peak shape of the data near the peak has a wider width in the velocity direction than that of the road clutter, and is asymmetric with respect to the target peak.

  Further, as shown in the left diagram of FIG. 6B, in the case of a pedestrian, the power of the data near the peak in the distance direction is different from the center cell (7) in the distance direction because the transmission wave is reflected at the pedestrian's location. There is a characteristic that decreases as the distance increases. As a result, in the case of a pedestrian, the peak shape of the peak vicinity data does not have a spread in the distance direction and has a shape symmetric with respect to the target peak.

  On the other hand, as shown in the right diagram of FIG. 6B, in the case of road surface clutter, the power of the data near the peak in the distance direction is such that the transmitted wave is reflected on the road surface having a width (depth) in the distance direction, and thus the center cell (7 ) Has a characteristic that it hardly decreases even if it moves away from the distance direction. As a result, in the case of road clutter, the peak shape of the data near the peak has a shape that is wider in the distance direction than in the case of a pedestrian.

  For this reason, as shown in FIG. 6C, the bias of the power center of gravity (speed direction) of the data near the peak tends to be in the case of pedestrians and not in the case of road surface clutter. Also, the spread of the peak shape in the speed direction tends to be large for pedestrians and small for road clutter. Further, the spread of the peak shape in the distance direction tends to be small for pedestrians and large for road clutter.

  In the case of a pedestrian, as shown in the left diagram of FIG. 6A, the peak shape in the speed direction of the peak vicinity data is asymmetric with respect to the target peak, and as shown in the left diagram of FIG. The peak shape is symmetric with respect to the target peak.

  On the other hand, in the case of road surface clutter, as shown in the right diagram of FIG. 6A, the peak shape in the velocity direction of the peak vicinity data is symmetric with respect to the target peak, and as shown in the right diagram of FIG. The peak shape is also symmetric with respect to the target peak.

  For this reason, the power of the data near the peak tends to cause a distribution bias due to the difference in symmetry even in an oblique direction in the two-dimensional coordinate system. As described above, the peak vicinity data tends to show different characteristics depending on whether the received signal is a reflected wave from a pedestrian or a road clutter.

  Therefore, the determination unit 36 determines whether or not the target is a pedestrian based on the target peak and the data near the peak by using the tendency of the characteristic of the data near the peak described above. Thereby, the radar device 1 can determine the pedestrian and the road clutter with high accuracy.

  Specifically, the discriminating unit 36 determines the target for each of the center of gravity position in the speed direction, the peak shape in the distance direction, the peak shape in the oblique direction, and the peak shape in the speed direction of the data near the peak in the two-dimensional coordinate system. It is determined whether it is a pedestrian.

  When determining whether or not the target is a pedestrian based on the position of the center of gravity in the speed direction of the data near the peak, the determination unit 36 determines the target peak and the peak with the center cell (7) as the origin as the characteristic amount of the power spectrum. The center of gravity in the speed direction of the neighboring data is calculated.

At this time, the discrimination unit 36 determines the power of each of the peak neighboring data of the neighboring cells (1) to (6), the center cell (7), and the neighboring cells (8) to (13) as P _{1 to} P ₁₃ , respectively. Then, the center of gravity V is calculated by the following equation [1].

  Then, when the calculated center of gravity V exceeds the threshold based on statistics and is separated from the center cell, the determination unit 36 determines that there is a bias in the power center of gravity (speed direction) and determines the target as a pedestrian. FIG. 7 is an explanatory diagram illustrating the tendency of the position of the center of gravity in the power speed direction according to the embodiment.

  As shown by the broken line graph in FIG. 7, according to statistics, the center of gravity V in the case of road surface clutter tends to be concentrated and distributed near the center cell. On the other hand, as shown by the solid line graph in FIG. 7, the center of gravity in the case of a pedestrian tends to be distributed over a wider range than in the case of road surface clutter.

  For this reason, when the center of gravity V calculated by [1] exceeds the threshold indicated by the dotted line in FIG. 7 and is separated from the center cell, the determination unit 36 determines the target as a pedestrian. That is, the determination unit 36 determines the target as a pedestrian when the calculated center of gravity V is located in an area where the percentage of pedestrians is greater than the percentage of road surface clutter in the statistics illustrated in FIG. Accordingly, the determination unit 36 can determine with high accuracy whether or not the target is a pedestrian from the target peak and the peak vicinity data of the instantaneous values acquired in the current cycle.

  When determining whether or not a pedestrian is a pedestrian based on the peak shape, the determining unit 36 determines the difference between the power of the near-peak data and the power of the target peak (hereinafter referred to as the power relative Value).

  FIG. 8 is an explanatory diagram illustrating an example of the definition of the power relative value according to the embodiment. As illustrated in FIG. 8, the determination unit 36 defines, for example, respective power relative values in the neighboring cells (1) to (6) and (8) to (13) as A (1) to H (13).

Here, for example, A (1) is calculated by subtracting P ₇ (the power of the target peak in the central cell 7) from P ₁ (the power of the peak neighboring data in the neighboring cell (1)). Further, B (2) is calculated by subtracting the _{P 7} from _{P 2.} Note that other power relative values are similarly calculated.

  Then, the determining unit 36 determines whether or not the target is a pedestrian based on the peak shape in the distance direction of the peak vicinity data in the two-dimensional coordinate system. The target is determined to be a pedestrian (see FIG. 6C).

  At this time, the determination unit 36 determines whether or not the pedestrian is a pedestrian based on the power relative value of the data near the peak 1 bin away from the target peak and the power relative value of the data near the peak 2 bin away from the target peak in the distance direction. And do. Then, when the absolute value of the power relative value is larger than a threshold based on statistics, the determination unit 36 determines that the target in the speed direction is small, and determines that the target is a pedestrian.

  FIG. 9A is an explanatory diagram illustrating the tendency of the power relative value of the data near the peak that is 1 bin away from the target peak in the distance direction according to the embodiment. FIG. 9B is an explanatory diagram illustrating the tendency of the power relative value of the data near the peak that is 2 bins away from the target peak in the distance direction according to the embodiment.

  When determining whether or not the pedestrian is a pedestrian based on the power relative value of the data near the peak that is 1 bin away from the target peak in the distance direction, the determination unit 36 determines which one of C (3) and G (11) is larger. Is obtained as a feature value. Note that the determination unit 36 may acquire an average value of C (3) and G (11) as a feature amount.

  Here, as shown in FIG. 9A, in the statistics, the absolute value of the power relative value of the data near the peak that is 1 bin away from the target peak is larger for the pedestrian shown by the solid line graph than for the road surface shown by the broken line graph. Tends to be larger than clutter.

  Therefore, when the absolute value of the power relative value is larger than the threshold indicated by the dotted line in FIG. 9A, the determination unit 36 determines the target as a pedestrian. That is, the determination unit 36 determines the target as a pedestrian when the acquired power relative value is located in an area where the percentage of pedestrians is greater than the percentage of road clutter in the statistics illustrated in FIG. 9A.

  When determining whether or not a pedestrian is a pedestrian based on the power relative value of the data near the peak that is 2 bins away from the target peak in the distance direction, the determination unit 36 determines whether the pedestrian is A (1) or H (13). The larger one is acquired as a feature value. Note that the determination unit 36 may acquire an average value of A (1) and H (13) as a feature amount.

  As shown in FIG. 9B, in the statistics, the absolute value of the power relative value of the data near the peak that is 2 bins away from the target peak is larger than that in the statistics shown in FIG. 9A. However, the tendency is larger than that of the road clutter indicated by the broken line graph.

  Therefore, when the absolute value of the power relative value is larger than the threshold indicated by the dotted line in FIG. 9B, the determination unit 36 determines the target as a pedestrian. That is, the determination unit 36 determines the target as a pedestrian when the acquired power relative value is located in an area where the percentage of pedestrians is greater than the percentage of road clutter in the statistics illustrated in FIG. 9B.

  In addition, the determination unit 36 determines whether the target is a pedestrian based on the oblique peak shape of the data near the peak in the two-dimensional coordinate system. At this time, when the absolute value of the power relative value is smaller than a threshold based on statistics, the determining unit 36 determines that the target is a pedestrian, assuming that the spread in the oblique direction is large.

  FIG. 10 is an explanatory diagram illustrating the tendency of the power relative value of the data near the peak adjacent to the target peak in the oblique direction according to the embodiment. When determining whether or not the target is a pedestrian based on the oblique peak shape of the data near the peak in the two-dimensional coordinate system, the determination unit 36 determines B (2), B (4), F (10), And the maximum value of F (12) is acquired as a feature value.

  Here, as shown in FIG. 10, in the statistics, the power absolute value of the data near the peak adjacent to the target peak in the oblique direction is larger for the pedestrian shown by the solid line graph than for the road clutter shown by the broken line graph. Tend to be smaller than

  Therefore, when the absolute value of the power relative value is smaller than the threshold indicated by the dotted line in FIG. 10, the determination unit 36 determines the target as a pedestrian. That is, the determination unit 36 determines the target as a pedestrian when the acquired power relative value is located in an area where the ratio of pedestrians is higher than the ratio of road clutter in the statistics illustrated in FIG.

  The determining unit 36 determines whether the target is a pedestrian based on the peak shape in the speed direction of the data near the peak in the two-dimensional coordinate system. Here, when the spread of the peak shape in the speed direction is large, the determination unit 36 determines the target as a pedestrian (see FIG. 6C).

  At this time, the determination unit 36 determines whether the vehicle is a pedestrian based on the power relative value of the data near the peak 1 bin away from the target peak and the power relative value of the data near the peak 2 bin away from the target peak in the speed direction. And do. Then, when the absolute value of the power relative value is smaller than a threshold based on statistics, the determination unit 36 determines that the spread in the speed direction is large and determines that the target is a pedestrian.

  FIG. 11A is an explanatory diagram illustrating the tendency of the power relative value of the data near the peak that is 1 bin away from the target peak in the speed direction according to the embodiment. FIG. 11B is an explanatory diagram illustrating the tendency of the power relative value of the data near the peak that is 2 bins away from the target peak in the speed direction according to the embodiment.

  When determining whether or not the pedestrian is a pedestrian based on the power relative value of the data near the peak that is 1 bin away from the target peak in the speed direction, the determination unit 36 features an average value of E (6) and E (8). Get as quantity. Note that the determination unit 36 may acquire the larger one of E (6) and E (8) as the feature amount.

  Here, as shown in FIG. 11A, in the statistics, the absolute value of the power relative value of the data near the peak that is 1 bin away from the target peak is larger for the pedestrian indicated by the solid line graph than for the road surface indicated by the broken line graph. Tends to be smaller than clutter.

  For this reason, when the absolute value of the power relative value is smaller than the threshold indicated by the dotted line in FIG. 11A, the determination unit 36 determines the target as a pedestrian. That is, the determination unit 36 determines the target as a pedestrian when the acquired power relative value is located in an area where the proportion of pedestrians is greater than the proportion of road clutter in the statistics illustrated in FIG. 11A.

  When determining whether or not the pedestrian is a pedestrian based on the power relative value of the data near the peak 2 bins away from the target peak in the speed direction, the determination unit 36 calculates the average value of D (5) and D (9). Is obtained as a feature value. Note that the determination unit 36 may acquire the larger one of D (5) and D (9) as the feature amount.

  As shown in FIG. 11B, in the statistics, the absolute value of the power relative value of the data near the peak that is 2 bins away from the target peak is larger than that in the statistics shown in FIG. 11A. However, the tendency is smaller than that of the road clutter indicated by the broken line graph.

  Therefore, when the absolute value of the power relative value is smaller than the threshold indicated by the dotted line in FIG. 11B, the determination unit 36 determines the target as a pedestrian. That is, the determination unit 36 determines the target as a pedestrian when the acquired power relative value is located in an area where the percentage of pedestrians is higher than the percentage of road surface clutter in the statistics illustrated in FIG. 11B.

  As described above, the discriminating unit 36 acquires the center of gravity position of the data near the peak with respect to the target peak in the velocity direction and the power relative value of the data near the peak as feature amounts, and compares them with the threshold value. Is determined as a pedestrian.

  Accordingly, the determination unit 36 can accurately determine, for example, a pedestrian and a road surface clutter that have been difficult to determine by comparing the feature amount of the target peak with the threshold value.

  Next, an example of a process executed by the signal processing unit 32 of the radar device 1 according to the embodiment will be described with reference to FIG. FIG. 12 is a flowchart illustrating an example of a process executed by the signal processing unit 32 of the radar device 1 according to the embodiment.

  When a beat signal is input, the signal processing unit 32 repeatedly executes the processing shown in FIG. 12 in a predetermined cycle. Specifically, when a beat signal is input, the signal processing unit 32 first performs a distance FFT process on the beat signal (step S101), and then performs a speed FFT process on the result of the distance FFT process. Perform (step S102).

  Subsequently, the signal processing unit 32 generates a power spectrum in a two-dimensional coordinate system from the result of the distance FFT processing (Step S103). Thereafter, the signal processing unit 32 determines whether or not the pedestrian is a pedestrian based on the center of gravity of the target peak and the data near the peak in the velocity direction (step S104).

  Subsequently, the signal processing unit 32 determines whether the subject is a pedestrian based on the peak shape in the distance direction of the peak vicinity data (Step S105), and determines whether the subject is a pedestrian based on the peak shape in the oblique direction of the peak vicinity data. Is determined (step S106).

  Thereafter, the signal processing unit 32 determines whether or not the target is a pedestrian based on the peak shape in the speed direction of the data near the peak (Step S107), and makes a final determination whether or not the target is a pedestrian (Step S108). .

  At this time, the signal processing unit 32 finally determines that the target is a pedestrian, for example, when the signal processing unit 32 determines that the target is a pedestrian in all the processes of steps S104 to S108. Thereafter, the signal processing unit 32 outputs target information including the distance, the relative speed, the angle, and the like of the target determined to be a pedestrian to the vehicle control device 2 (Step S109), ends the process, and again executes The process starts from step S101.

  Note that the signal processing unit 32 determines that the target is a pedestrian if it is determined that the target is a pedestrian in at least one of the processes of steps S104 to S108, but not all of the processes of steps S104 to S108. May be finally determined.

  In addition, the signal processing unit 32 does not necessarily need to execute all of the processes of steps S104 to S108, and executes at least one of the processes of steps S104 to S108, so that the target is a pedestrian. A final determination as to whether or not it may be made may be made.

  The above-described embodiment is an example, and various modifications are possible. For example, when the characteristic amount of the power spectrum in the vicinity of the peak based on the target peak of the target is input, the determination unit 36 of the radar device 1 stochastically classifies the target into one of a pedestrian and a road surface. It may be a classifier.

  In the case of such a configuration, the discriminating unit 36 is characterized by the power center of gravity of the data near the peak in the speed direction, the power relative value in the distance direction of the data near the peak, the power relative value in the oblique direction, and the power relative value in the speed direction. Entered as quantity.

  Then, the determination unit 36 determines whether the target is a pedestrian based on, for example, Bayes theory based on the input feature amount, and outputs the determination result. The determination unit 36 can also determine the pedestrian and the road clutter with high accuracy from the instantaneous value of the power spectrum obtained in one cycle of processing.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

REFERENCE SIGNS LIST 1 radar device 2 vehicle control device 10 transmission unit 11 signal generation unit 12 oscillator 13 transmission antenna 20 reception unit 21 reception antenna 22 mixer 23 A / D converter 30 processing unit 31 transmission control unit 32 signal processing unit 33 first processing unit 34 Second processing unit 35 generation unit 36 discrimination unit 37 output unit

Claims (8)

A receiving unit that receives a reflected wave of the transmission wave reflected by the object as a reception signal,
From the received signal received by the receiving unit, a distance direction corresponding to the distance to the object, and a generating unit that generates a two-dimensional power spectrum of a speed direction corresponding to a relative speed with the object,
A determination unit configured to detect a peak from the power spectrum generated by the generation unit and determine whether the peak is caused by a pedestrian based on the peak and a power spectrum near the peak. A radar device characterized by the above-mentioned. The determination unit includes:
The radar apparatus according to claim 1, wherein the determination is performed based on a center of gravity in the velocity direction of the peak and a power spectrum in the vicinity of the peak in the two-dimensional direction. The determination unit includes:
The radar apparatus according to claim 1, wherein the determination is performed based on a peak shape in the velocity direction of the power spectrum near the peak and the peak in the two-dimensional direction. 4. The determination unit includes:
The radar apparatus according to any one of claims 1 to 3, wherein the determination is performed based on a peak shape in the distance direction of the power spectrum near the peak and the peak in the two-dimensional direction. The determination unit includes:
The radar apparatus according to any one of claims 1 to 4, wherein the determination is performed based on a peak shape in an oblique direction of the power spectrum near the peak and the two-dimensional peak. The determination unit includes:
The radar apparatus according to any one of claims 1 to 5, wherein the determination is performed by comparing a characteristic amount indicating a characteristic of a power spectrum near the peak with respect to the peak with a threshold. The determination unit includes:
The radar according to any one of claims 1 to 6, wherein the determination is performed by a probabilistic classifier that receives a characteristic amount indicating a characteristic of a power spectrum near the peak with respect to the peak. apparatus. A receiving step of receiving a reflected wave of the transmitted wave reflected by the object as a received signal,
From the received signal received by the receiving step. A generation direction that generates a power spectrum for a two-dimensional distance direction corresponding to the distance to the object and a speed direction corresponding to a relative speed to the object,
Determining a peak from the power spectrum generated in the generating step, and determining whether the peak is caused by a pedestrian based on the peak and a power spectrum near the peak. An object discriminating method characterized in that:

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