JP2009014631A - Radar device and method for detecting target thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a failure or mistake in pairing even when a plurality of targets are in close proximity and differ in angles at which local maximal values are formed in a group of level peaks of upbeat/downbeat signals. <P>SOLUTION: In an FM-CW radar device the level peaks of upbeat/downbeat signals corresponding to frequency differences in sent and received signals between a period of rising frequencies and a period of falling frequencies are detected, and from among a plurality of first local maximal values belonging to a group of level peaks of upbeat signals distributed in angular orientation and a plurality of second local maximal values belonging to a group of level peaks of downbeat signals distributed in angular orientation, a first local maximal value and a second local maximal value are associated with each other in accordance with the proximity of local maximal values and the proximity of angles at which local maximal values are formed. This makes it possible to prevent a failure or mistake in pairing of a plurality of targets even when a plurality of targets are in close proximity and one and the same target differs in angles at which a first local maximal value and a second local maximal value are formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radar apparatus that transmits a radar wave that alternately repeats gradual increase and decrease in frequency as a transmission signal to a predetermined angle range, and receives a transmission signal reflected by the target as a reception signal, and a target detection method therefor In particular, the present invention relates to a radar apparatus that detects a relative distance or a relative speed of a target based on a frequency difference between a transmission signal and a reception signal, and a target detection method thereof.

  There is known an FM-CW (Frequency Modulated-Continuous Wave) radar apparatus that uses a frequency-modulated continuous wave as a radar wave. The FM-CW radar apparatus transmits, as a transmission signal, a radar wave that alternately repeats a frequency increase period in which the frequency gradually increases in a triangular wave shape and a frequency decrease period in which the frequency gradually decreases, and receives the transmission signal reflected by the target as a reception signal As received. Then, the FM-CW radar device mixes the transmission signal and the reception signal, and generates a beat signal corresponding to the frequency difference between the two. The FM-CW radar apparatus then uses the frequency (upbeat frequency) of the beat signal (upbeat signal) during the frequency increase period of the transmission signal and the frequency (downbeat signal) of the beat signal (downbeat signal) during the frequency decrease period. The relative distance and relative speed of the target are detected based on the frequency.

  Such an FM-CW radar apparatus is mounted on a vehicle and used to detect the relative speed and relative distance of a target such as a preceding vehicle. The in-vehicle FM-CW radar apparatus scans a predetermined angle range with a transmission signal by swinging the antenna. At this time, if a target exists, level peak groups of up / down beat signals distributed in the angular direction are formed. The FM-CW radar apparatus detects the angle at which the maximum value is formed in each level peak group as the angle at which the target is located. Further, the relative speed and the relative distance of the target are calculated from the upbeat frequency and the downbeat frequency indicating the respective maximum values. Patent Document 1 describes an example of such an in-vehicle FM-CW radar apparatus.

  When a scanning FM-CW radar apparatus as described above scans a predetermined angular range, and there is a single target in that angular range, the level peak group of each up / down beat signal , Each forming a single maximum. Therefore, a pair of upbeat frequency and downbeat frequency indicating each maximum value is uniquely obtained, and based on this, the relative speed and relative distance of the target are calculated.

  However, when there are a plurality of targets in the scanned angle range, a plurality of maximum values are formed in each of the level peak groups of the up / down beat signal. Therefore, in order to calculate the relative distance and relative speed of each target, it is necessary to associate (pair) the local maximum values formed by the same target.

In this regard, the conventional FM-CW radar apparatus according to the related art uses the angle at which the maximum value is formed as a criterion for determining the same target. That is, in each of the level peak groups of the up / down beat signals, the local maximum values having the closest angles are paired.
JP 2000-65921 A

  By the way, in the in-vehicle radar device, since the target and the radar device are moving at high speed, the angle of the reflecting surface of the target slightly changes with respect to the transmitted radar wave. Then, the maximum value of the level peak group may be formed at an angle other than the center of the target.

  Then, in the up / down beat signals for the same target, the angle at which the maximum value is formed is different, and the maximum values may not be paired. Then, there arises a problem that the relative distance and relative velocity cannot be detected for the target.

  In addition, when a plurality of targets are close in angle, angles at which local maximum values are formed are close to each other. For this reason, local maximum values may be paired between different targets. Then, the upbeat frequency and the downbeat frequency of different targets are used, and there arises a problem that the relative distance and the relative speed are erroneously detected.

  Furthermore, when the operation of the host vehicle is controlled based on the detection result, if the relative distance and relative speed of the target are not detected or are detected erroneously, the safety is lowered.

  Therefore, the object of the present invention is that even when the angles of a plurality of targets are close to each other and the angle at which the maximum value is formed in the level peak group of the up / down beat signal of each target is different, An object of the present invention is to provide a radar apparatus and a target detection method that prevent erroneous pairing.

  To achieve the above object, according to the first aspect of the present invention, a radar wave that alternately repeats a frequency rising period in which the frequency gradually increases and a frequency falling period in which the frequency gradually decreases is transmitted as a transmission signal in a predetermined angle range. In the radar apparatus that receives the transmission signal reflected by the target as a reception signal and detects the relative distance or the relative speed of the target based on the transmission signal and the reception signal, the transmission in the frequency increase period An upbeat signal level peak corresponding to a frequency difference between a signal and the reception signal and a downbeat signal level peak corresponding to a frequency difference between the transmission signal and the reception signal in the frequency drop period are detected. A level peak detecting means; a plurality of first maximum values in a level peak group of the upbeat signal distributed in the angular direction; Among the plurality of second maximum values in the level peak group of the downbeat signal, based on the closeness of the maximum value and the closeness of the angle at which the maximum value is formed, between the first and second maximum values From the pairing means for performing association, the frequency of the upbeat signal indicating the associated first maximum value, and the frequency of the downbeat signal indicating the second maximum value, the relative distance or relative of the target It has a distance / speed detecting means for detecting the speed.

  According to a preferred embodiment of the above aspect, the pairing means includes the first and second maximum values among a plurality of combinations of the plurality of first maximum values and the plurality of second maximum values. The difference between each other and the difference between the angles at which the first and second maximum values are formed are respectively weighted, and the association is performed based on the difference between the weighted maximum values and the difference between the angles. It is characterized by performing.

  According to another preferred embodiment of the above-mentioned aspect, the pairing means has a first number of the second (with a difference within a specified value) with respect to one of the first (or second) maximum values. Alternatively, when the first maximum value is detected, the first (or second) maximum value is associated with the second (or first) maximum value, and the first (or second) ) When a second number of the second (or first) maximum value that is larger than the first number, the difference of which is within a specified value, is detected. For the plurality of combinations of the local maximum value 2) and the second (or first) local maximum value, the association is performed based on the local maximum value and the angle at which the local maximum value is formed.

  According to the above aspect, the pairing means includes a plurality of first maximum values in the level peak group of the downbeat signal distributed in the angular direction and a plurality of second values in the level peak group of the downbeat signal distributed in the angular direction. The first and second maximum values are associated with each other based on the closeness of the maximum value and the closeness of the angle at which the maximum value is formed. Since the angle and shape of the reflection surface of the radar wave differs between different targets, paying attention to the difference in the level of the up / down beat signal, the same target is obtained if the maximum values are the same, and the other target is different. I can judge. Therefore, even when multiple targets are close to each other and the angle at which the maximum value of the up / down beat signal is formed is different for each target, in addition to the closeness of the angle, the closeness of the maximum value is further increased. By performing pairing based on the above, it is possible to prevent pairing failure or erroneous pairing between a plurality of targets.

  According to the above embodiment, the difference between the first and second maximum values and the difference between the angles at which the first and second maximum values are formed are respectively weighted. In such a case, the pairing can be performed with an emphasis on the closeness of the angle. Or, conversely, when the angle between the local maximum values is close, pairing can be performed with an emphasis on the closeness of the local maximum value.

  According to another embodiment described above, the second (or first) difference in which the difference in angle at which the maximum value is formed is within a specified value with respect to one first (or second) maximum value. The pairing based on the angle difference and the pairing based on the maximum value and the angle difference are switched according to the number of maximum values. That is, when there are few pairing candidates, the possibility of pairing failure or incorrect pairing is small, so use the angle difference.When there are many pairing candidates, pairing failure or incorrect pairing Since the possibility is great, the maximum value and the angle difference are used. By doing so, the efficiency of the entire pairing process can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof.

  FIG. 1 shows an example in which a radar apparatus according to this embodiment is mounted on a vehicle. The radar device 10 mounted in the front front grill of the vehicle 1 is an FM-CW radar device that uses a frequency-modulated continuous wave as a radar wave. The radar apparatus 10 includes a mechanism that swings the antenna, and scans a certain angle range (for example, ± 8 degrees) with the center in front of the vehicle by a transmission signal. The radar apparatus 10 receives a transmission signal reflected by a target such as the preceding vehicle 2 as a received signal, and the angle θc of the center portion of the preceding vehicle 2 with respect to the front center of the host vehicle 1 and the relative distance of the preceding vehicle 2. R and relative speed V are detected. Based on the detection result of the radar device 10, a control device (not shown) of the vehicle 1 controls the operation of the vehicle 1 so as to follow the vehicle 2 or avoid a collision.

  FIG. 2 is a diagram illustrating a method in which the radar apparatus 10 detects the relative speed and relative distance of a target. FIG. 2A shows a change in frequency of the transmission signal and the reception signal of the radar apparatus 10 with respect to time. As shown by the solid line, the frequency of the transmission signal transmitted by the radar apparatus 10 gradually increases during the frequency increase period UP corresponding to the rising period of the triangular wave, and gradually decreases during the frequency decrease period DN corresponding to the falling period of the triangular wave. This is repeated alternately. Then, when this transmission signal is reflected by the target, as shown by a dotted line, it receives a time delay ΔT according to the relative distance and a frequency shift ΔD due to the influence of the Doppler effect according to the relative speed. Received as a signal.

  When such a transmission signal and reception signal are mixed, a beat signal whose frequency changes is obtained as shown in FIG. 2B corresponding to the frequency difference between the two. That is, an upbeat signal with an upbeat frequency fu is obtained in the frequency rise period UP, and a downbeat signal with a downbeat frequency fd is obtained in the frequency fall period DN.

  The radar apparatus 10 calculates the relative distance R and the relative speed V of the target by using the upbeat frequency fu and the downbeat frequency fd as follows (where C is the speed of light and fm is a triangular wave). Frequency, f0 is the center frequency of the triangular wave, and ΔF is the frequency shift width of the triangular wave).

R = C · (fu + fd) / (8 · ΔF · fm)
V = C · (fd−fu) / (4.f0)
FIG. 3 shows a configuration of the radar apparatus 10 in the present embodiment. The radar apparatus 10 includes an antenna 11 that transmits and receives radar waves, and an antenna drive unit 12 that swings the antenna 11. The radar apparatus 10 also includes a transmission / reception circuit 14 that generates a transmission signal, controls the antenna driving unit 12, and generates an up / down beat signal. Further, the radar device 10 processes the up / down beat signal and detects the level peak, and the distribution of the level peak group of the up / down beat signal, the target angle, relative speed, relative It has a signal processing device 20 that detects the distance and outputs it to the vehicle control device.

  The transmission / reception circuit 14 generates the frequency-modulated transmission signal shown in FIG. 1 and causes the antenna 11 to transmit a part thereof. At this time, the transmission / reception circuit 14 swings the antenna 11 and scans an angle range of ± 8 degrees with the transmission signal W1 with respect to the front center of the radar apparatus. The transmission / reception circuit 14 synchronizes the frequency modulation period and the swinging operation of the antenna 11 so that the pair of frequency increase periods UP and the frequency decrease period DN correspond to each other for each predetermined unit angle range.

  The transmission / reception circuit 14 mixes another part of the transmission signal with the reception signal, and generates an up / down beat signal corresponding to the frequency difference between the two.

  The signal processing circuit 15 is configured by an application specific integrated circuit, for example, and each part thereof corresponds to a functional module. The AD converter 16 AD-converts the up / down beat signal. Then, an FFT (Fast Fourier Transform) processing unit 17 performs FFT processing on the up / down beat signal converted into a digital signal. And the level peak detection part 18 detects the level peak for every frequency of an up / down beat signal from a FFT process result. Therefore, the level peak detector 18 corresponds to “level peak detector”.

As an example, the signal processing device 20 is constituted by a microcomputer having a CPU, a ROM that stores various processing programs, and a RAM that is used as a work area for operations performed by the CPU. Each unit of the signal processing device 20 is realized by a CPU that operates in accordance with each processing program.
First, the data receiving means 22 receives the processing result data and stores it in the RAM. The target position predicting unit 24 then detects the angle, relative distance, relative speed, etc. of the current target based on the target detection result at the previous scan when one round trip of the antenna 11 is one scan. Predict. This prediction is used to determine the continuity of the current detection result, which will be described later.

  Next, the grouping unit 32 groups the level peak groups corresponding to the same target from the level peak groups distributed in the scan angle direction of each of the up / down beat signals. Here, grouping will be described with reference to FIGS.

  FIG. 4 shows an example of level peak groups of up / down beat signals generated from transmission / reception signals for one target. 4A and 4B, the horizontal axis represents the angle, the vertical axis represents the up / down beat frequency, and the size of the plotted points represents the size of each level peak. In the frame, each level peak group is shown with the angle as the horizontal axis and the vertical axis as the level peak level.

  First, since a target such as a vehicle has a lateral spread, an upbeat signal of almost the same frequency and a downbeat signal of almost the same frequency are generated from a plurality of adjacent angles from the transmission / reception signals for the same target. The Therefore, FIG. 4A shows a level peak group of the upbeat signal of the upbeat frequency fu1 detected in the range of the angle α ± 2 degrees. FIG. 4B shows a level peak group of the downbeat signal of the downbeat frequency fd1 detected in the range of the angle α ± 2 degrees.

As described above, in the angle range scanned by the antenna 11, the pair of frequency increase periods UP and frequency decrease periods DN are associated with each other for each predetermined unit angle range. Therefore, the upbeat signal and the downbeat signal are obtained at different angles within each unit angle range. However, in the following description, for the sake of convenience, the angle α ± n degrees (n = 1, 2,...) Indicates the center angle of each unit angle range. That is, an upbeat signal and a downbeat signal obtained at an angle α ± n degrees mean an upbeat signal or a downbeat signal detected within a unit angle range centered on the angle α ± n degrees.

  Next, the level of the received signal is highest at the center of the target. Therefore, the level peak group of the up / down beat signal generated from the transmission / reception signals for the same target shows a maximum value at the angle of the center of the target. When attention is paid to this, in the level peak group of the upbeat signal shown in FIG. 4A, the maximum value UP1 is formed at the angle α. Therefore, the level peak group that forms a mountain-shaped distribution adjacent to the maximum value UP1 is grouped as one group UG1 corresponding to the same target. Similarly, also in the level peak group of the downbeat signal shown in FIG. 4B, the maximum value DP1 is formed at the angle α. Then, the level peak group that forms a mountain-shaped distribution adjacent to the maximum value DP1 is grouped as one group DG1 corresponding to the same target.

  In this way, when grouping the level peak groups of up / down beat signals generated by the same target and determining the angle, relative distance, and relative speed of the target, the local maximum value of each group is used as a representative. Use. That is, the angle at which the maximum value of each group is formed is detected as the angle of the target, and the relative distance and relative speed of the target are calculated from the up / down beat frequency indicating the maximum value.

  By the way, there may be a plurality of targets in the angle range scanned by the radar apparatus 10.

  FIG. 5 shows an example of grouping when a plurality of targets are present. In FIG. 5, for convenience, only the maximum value is indicated by the size of the plotted points, and level peaks other than the maximum value are indicated by white dots of the same size.

  As shown in FIG. 5A, in the level peak group of the upbeat signal, the level peak groups forming the maximum values UP1, UP2, UP3 at the upbeat frequencies fu1, fu2, fu3, respectively, are group UG1, UG2. , Grouped as UG3. On the other hand, as shown in FIG. 5B, the level peak groups of the downbeat signals are grouped into the level peak groups that respectively form the maximum values DP1, DP2, and DP3 at the downbeat frequencies fd1, fd2, and fd3. Grouped as DG1, DG2, and DG3.

  Thus, a plurality of maximum values are formed in the level peak group of each up / down beat signal, and grouping is performed for each maximum value. Then, in order to detect the relative speed and the relative distance using the upbeat frequency and the downbeat frequency for each of the plurality of targets, the level peak group of each of the up / down beat signals generated from the same target is used. It is necessary to associate the local maxima with each other. This process is called pairing.

  Accordingly, the grouping means 32 prepares the level peak group of each up / down beat signal, the angle at which the maximum value is formed, and the maximum value for each group of level peaks of the up / down beat signal in preparation for the pairing process described later. A data set having the indicated frequency is stored in the buffer area of the RAM.

  Specifically, as shown in FIG. 5A, each of the data sets of the maximum values UP1, UP2, and UP3 on the upbeat signal side is in the order of the level of the maximum value in the buffer areas BUF11, BUF12, and BUF13. Are stored sequentially. Further, as shown in FIG. 5B, the data sets of the maximum values DP1, DP2, and DP3 on the downbeat signal side are sequentially stored in the buffer areas BUF21, BUF22, and BUF23 in the order of the level of the maximum value. Is done.

  Next, the pairing means 34 pairs a plurality of maximum values of the level peak group of the up / down beat signal stored in the buffer area with each other.

  FIG. 6 is a flowchart for explaining the pairing procedure. FIG. 7 shows the local maximum at which pairing is performed. In FIG. 7, it is assumed that the maximum value UP1 and the maximum value DP1, the maximum value UP2 and the maximum value DP2, and the maximum value UP3 and the maximum value DP3 correspond to the same target.

  The pairing means 34 searches for the maximum value on the downbeat signal side to be paired from the maximum value on the upbeat signal side in the order stored in the buffer, that is, in the order of the level of the maximum value.

  First, the pairing means 34 extracts the maximum value UP1 having the maximum level on the upbeat signal side (YES in S1, S2). Then, the pairing means 34 searches for the maximum value on the downbeat signal side satisfying a predetermined search condition on the basis of the maximum value UP1 (S4). Here, the maximum value UP1 serving as a reference for the search condition is referred to as a search reference maximum value. If the search condition is, for example, that the angle difference at which the maximum value is formed is within 2 degrees, the maximum values DP1 and DP3 are extracted. Note that the search condition may include a condition such that the level difference of the maximum value is within a predetermined range, or the frequency difference indicating the maximum value is within the predetermined range.

  Next, since there are a plurality of searched local maximum values (YES in S8), the pairing means 34 finds the local maximum value that is closest in angle to the local maximum value UP1 that is the search reference local maximum value, that is, has the smallest angular difference. Extract from local maximum values DP1 and DP3. At this time, the angle at which the maximum value UP1 is formed is (α + 2). Therefore, when a local maximum value having a minimum angle difference from the local maximum value UP1 is searched, the local maximum value DP1 formed at the angle (α + 2) is extracted (S8, P1 in FIG. 7).

  Next, the pairing means 34 uses the extracted maximum value DP1 on the downbeat signal side as the search reference maximum value, and searches for the maximum value on the upbeat signal side that satisfies the search condition (S10). Then, maximum values UP1 and UP3 are extracted. Then, the local maximum value that minimizes the angle difference from the local maximum value DP1 that is the search reference local maximum value is extracted from the local maximum values UP1 and UP3 (YES in S12, S14). Then, the maximum value UP1 formed at the angle (α + 2) is extracted (P2 in FIG. 7).

  Then, the search result from the upbeat signal side matches the search result from the downbeat signal side (YES in S16). That is, the angle at which each of the local maximum value UP1 and the local maximum value DP1 is formed is the closest. Therefore, first, the local maximum values UP1 and DP1 are paired (S18).

  When the maximum value UP1 is paired, the pairing means 34 performs pairing in the same procedure as described above with the maximum value UP2 on the upbeat signal side having the next highest level as the search reference maximum value (YES in S1). , S2). First, the maximum value DP2 formed at the angle (α-2) and the maximum value of the angle difference within 2 degrees are searched (S4). At this time, the already paired local maximum DP1 is excluded from the search target. Then, the maximum value DP2 formed at the angle (α-2) is extracted (P3 in FIG. 7). In this case, since there are no other candidates (NO in S6), if the maximum value DP2 is set as the search reference maximum value, the maximum value UP2 formed at an angle (α-2) within 2 degrees is extracted. (NO in S10 and S12, P4 in FIG. 7). Therefore, the local maximum values UP2 and DP2 are paired (S18).

  Then, the search is performed with the maximum value UP3 on the upbeat signal side having the next highest level as the search reference maximum value (YES in S1, S2). At this time, the already paired local maximum values DP1 and DP2 are excluded from the search target. Then, the maximum value DP3 formed at the angle α within 2 degrees with the angle α at which the maximum value UP3 is formed is extracted (S4,). Then, if the maximum value DP3 is set as the search reference maximum value, the maximum value UP3 formed at an angle of 2 degrees or less is extracted (NO in S6, NO in S10, NO in S12, P6 in FIG. 7). Therefore, the local maximum values UP3 and DP3 are paired (S18).

  As a result of the above procedure, the local maximum value UP1 and the local maximum value DP1, the local maximum value UP2 and the local maximum value DP2, and the local maximum value UP3 and the local maximum value DP3 are paired with each other because the formed angles are the closest. That is, local maxima formed by the same target are paired.

  In this way, the pairing unit 34 excludes the paired local maximum values from the search target, and performs the same processing on the remaining local maximum values. By doing so, finally, all the local maximum values on the upbeat signal side and the downbeat signal side are paired. In the pairing process, the angle of each target, that is, the angle at which the maximum value is formed is detected.

  When the pairing is completed, the distance / speed detection means 35 detects the relative distance and the relative speed of the target based on the upbeat frequency and the downbeat frequency indicating the paired maximum values.

  Next, the continuity determination means 36 determines the presence or absence of continuity from the error between the current detection result predicted from the detection result of the previous scan and the detection result actually detected in the current scan. At this time, if the error is within a predetermined range, it is determined that there is continuity. The number of times determined to have continuity is stored in the RAM.

  Next, the output possibility determination means 46 determines that the detection result of the target determined to have continuity for a predetermined number of times or more can be output to the vehicle control device.

  In addition, when a plurality of angles are detected from a single target, the target combining unit 48 combines these to generate a single target detection result.

  Then, the data output means 50 outputs the detection result of the target determined to be output to the vehicle control device.

  When the target detection result is output as described above, the vehicle control device performs acceleration / deceleration of the host vehicle based on the detection result, and follows the vehicle so as to maintain an appropriate inter-vehicle distance. Run control and avoid collisions.

  By the way, in the on-vehicle radar device 10, both the target and the radar device 10 are moving at high speed. For this reason, the angle of the reflecting surface of the target slightly changes with respect to the transmitted radar wave. Then, the maximum value of the level peak group of the up / down beat signal may be formed outside the center of the target. Then, the angle at which the maximum value of the level peak group is formed may be different in the up / down beat signal based on the received signal from the same target. Next, an example of pairing in such a case is shown.

  FIG. 8 shows an example of pairing when the angle of the maximum value is shifted. The local maximum value UP11 and the local maximum value DP11, the local maximum value UP12 and the local maximum value DP12, and the local maximum value UP13 and the local maximum value DP13 correspond to the same target. However, in this case, the maximum values UP11, DP11, and DP13 are formed at an angle different from the center of each target.

  First, the angle at which the maximum value UP11 having the highest level on the upbeat signal side is formed is (α + 3). Then, the maximum value DP13 formed at the angle (α + 1) is extracted as the maximum value with the smallest angle difference (P11). Next, when the local maximum value with the smallest angle difference is searched from the angle (α + 1) of the local maximum value DP13, the local maximum value UP13 formed at the angle α is extracted (P12). Then, pairing fails because both search results are different.

  Since pairing of the maximum value UP11 has failed, next, pairing is performed for the second level maximum value UP12. The angle at which the maximum value UP12 is formed is (α−2). Then, the maximum value DP12 formed at the angle (α-2) that minimizes the angle difference is extracted (P13). Next, when a local maximum value having the smallest angle difference is searched from the local maximum value DP12, the local maximum value UP12 formed at the angle (α-2) is extracted (P14). Then, the search results of both match and pair.

  Therefore, in this case, detection of the angle, relative speed, and relative distance of the target that should originally be detected by the maximum values UP11 and DP11 and the target that should be detected by the maximum values UP13 and DP13 is not performed. Therefore, the continuity of the detection results of these targets is interrupted, and there is a problem that they are not output to the vehicle control device.

  FIG. 9 shows another example of pairing when the angle of the maximum value is shifted. In the example shown in FIG. 9, the angle of the maximum value UP3 is different from that in the example of FIG.

  First, the angle at which the maximum value UP11 having the highest level on the upbeat signal side is formed is (α + 2). Then, the maximum value DP13 formed at the angle (α + 1) is extracted as the maximum value with the smallest angle difference (P21). Next, when searching for a maximum value that minimizes the angle difference from the maximum value DP13, the maximum value UP11 formed at the angle (α + 2) is extracted (P22). Then, since the search results of both match, it is paired.

  Next, pairing is performed on the maximum value UP12 of the second level. The angle at which the maximum value UP12 is formed is (α−2). Then, the maximum value DP12 formed at the angle (α-2) that minimizes the angle difference is extracted (P23). Next, when searching for a maximum value that minimizes the angle difference from the maximum value DP12, a maximum value UP12 formed at the angle (α-2) is extracted (P24). Then, the search results of both match and pairing is performed.

  Further, pairing is performed for the maximum value UP13 of the third level. The angle at which the maximum value UP13 is formed is (α-1). Then, the maximum value DP11 formed at the angle α that minimizes the angle difference is extracted (P25). Next, when a local maximum value having the smallest angle difference is searched from the local maximum value DP13, the local maximum value UP13 formed at the angle α is extracted (P26). Then, the search results of both match and pair.

  However, in this case, the maximum values UP11 and DP13 and the maximum values UP13 and DP11 are paired between different targets. Then, the relative distance and relative speed of the detected target are incorrect. Then, when the operation of the host vehicle is controlled based on such a result, there is a risk that the safety of traveling is reduced.

  In this way, in the procedure for pairing the local maxima with the smallest angle difference, that is, the angle that approximates the angle most closely, if there is a target that is close in angle when the local maxima are misaligned, Fails or is paired incorrectly. In this regard, focusing on the level of the up / down beat signal, the angle of the reflection surface of the radar wave and the shape are different between different targets, so the level of the up / down beat signal is also different. For example, when comparing a large vehicle such as a truck with a passenger car, the former reflecting surface is larger in area than the latter reflecting surface, so the level of the received signal from the former is greater than the level of the received signal from the latter . Therefore, a difference also occurs in the level of the up / down beat signal. Therefore, if the level of the maximum value of the level peak group of each up / down beat signal matches or approximates, it can be determined as the same target, and if it is different, it can be determined as a different target.

  Therefore, the radar apparatus 10 according to the present embodiment performs pairing using not only the difference in angle at which the maximum value is formed but also the level of the maximum value as a criterion.

  FIG. 10 is a flowchart for explaining the pairing procedure in the present embodiment. The maximum value shown in FIGS. 7 to 8 will be described as an example.

  In the present embodiment, the pairing means 34 first creates all combinations of the local maximum values UP11, UP12, and UP13 and the local maximum values DP11, DP12, and DP13 (S100). An example of a matrix of combinations is shown in FIG.

  Then, the pairing means 34 obtains the difference in angle at which the maximum value is formed and the difference in level of the maximum value in all combinations, and evaluates the sum of the difference in angle and the level as the evaluation points SC11, SC12,. , SC33 is calculated (S120). Then, the pairing means 34 performs pairing in order from the local maximum values having the large evaluation points (S130).

  By doing so, even if the angle between the maximum value on the upbeat signal side and the maximum value on the downbeat signal side formed from the same target is shifted, pairing is performed if the level difference is small. Therefore, pairing failure can be prevented. Further, even if local maximum angles formed by different targets are close to each other, they are not paired by mistake if the level difference is large. Therefore, erroneous pairing can be prevented.

  As a modified example, the evaluation points may be weighted.

  FIG. 12 is a diagram illustrating an example of weighting evaluation points. FIG. 12A shows the evaluation points for the angle difference. That is, a higher evaluation score is assigned as the angle difference is smaller. FIG. 12B shows the evaluation points for the level difference. That is, a higher evaluation score is assigned as the level difference is smaller. As shown in FIGS. 12A and 12B, the angle difference is weighted more than the level difference. In this case, pairing is performed in descending order of the total evaluation points.

  In this way, when the level difference between the local maximum values is small, pairing can be performed with an emphasis on the angle difference. Or, conversely, when the angles between the local maximum values are close to each other, the pairing can be performed with an emphasis on the level difference between the local maximum values.

  Furthermore, the number of level peaks of the level peak group in which the maximum value is formed may be added to the maximum value data set. In this case, if the number of level peaks matches, it can be determined that they are the same target. Therefore, a weighted evaluation point as shown in FIG. 12C may be applied to the level peak number difference.

  Further, the transmission / reception circuit 15 may be provided with means for detecting the phase difference of the up / down beat signal, and the phase difference of the up / down beat signal in which the maximum value is formed may be added to the maximum value data set. In this case, if the phases of the up / down beat signals match, it can be determined that they are the same target. Therefore, the pairing means 34 may apply an evaluation point weighted as shown in FIG. 12D to this phase difference.

  By performing pairing based on the total of these evaluation points, pairing with higher accuracy becomes possible.

  Further, the weighting as described above may be variable depending on the situation. For example, when the relative distance of the target detected in the previous scan is smaller than a predetermined reference value, that is, when the distance is relatively close, there is a high possibility that the angle difference between the targets is close. On the other hand, since the angle between the reflecting surface of the target and the transmission signal is increased, the possibility that a maximum value is formed at a position other than the center of the target is increased. Therefore, in such a case, as shown by the dotted line in FIG. By doing so, it is possible to prevent pairing failure or erroneous pairing that occurs when the angle difference is emphasized.

  Further, in the above case, the pairing means 34 may receive the low-speed tracking mode or the high-speed tracking mode from the vehicle control device and determine the distance of the target. . In other words, in the low-speed follow-up running mode, the target that is the subject of follow-up running is present in a relatively short distance, and in this case, the weighting for the angle difference may be reduced.

  Furthermore, in order to reduce the processing load on the signal processing device 20 by the evaluation point calculation as described above, another modification example as described below is possible.

  FIG. 13 is a flowchart for explaining a pairing procedure in another modification. The pairing means 34 first searches for the maximum value on the downbeat signal side from the maximum value on the upbeat signal side. At this time, a search is made for an angle difference within which the maximum value is formed is within 1 degree (S201). When the search result is singular (YES in S202), pairing is performed according to the normal procedure shown in FIGS. 6 and 7 (S203). In this case, since there is no other target whose angle is close, correct pairing is performed by a normal procedure. On the other hand, when there are a plurality of search results (NO in S202), the pairing unit 34 performs pairing using the evaluation points shown in FIGS. 10 to 12 (S204). In this case, evaluation points may be calculated for all combinations of maximum values, or more preferably, evaluation points may be calculated for combinations of a plurality of maximum values having an angle difference of 1 degree or less. Then, pairing is performed for the combination of the highest evaluation points.

  In this way, when normal pairing is possible, this is performed, and when there is a high possibility of pairing failure or incorrect pairing, pairing using evaluation points is performed. By doing so, the processing efficiency of the whole pairing process can be improved.

  In the above description, the case where the radar apparatus 10 searches the front of the vehicle has been described as an example. However, the present embodiment can be applied even when the radar apparatus 10 searches the side or the rear of the vehicle.

  As described above, according to the present embodiment, even when a plurality of targets are close to each other and the angle at which the maximum value in the level peak group of the up / down beat signal of each target is formed is different, pairing is performed. Failure and incorrect pairing can be prevented.

An example in which the radar apparatus according to the present embodiment is mounted on a vehicle will be described. It is a figure explaining the method for the radar apparatus 10 to detect the relative speed and relative distance of a target. It is a figure which shows the structure of the radar apparatus 10 in this embodiment. It is a figure which shows the example of the level peak group of the up / down beat signal produced | generated from the transmission / reception signal with respect to one target. It is a figure which shows the example of grouping in case a some target exists. It is a flowchart figure explaining a pairing procedure. It is a figure which shows the example of pairing. It is a figure which shows the example of pairing when the angle of local maximum has shifted | deviated. It is a figure which shows another example of the pairing when the angle of local maximum shifts. It is a flowchart figure explaining the pairing procedure in this embodiment. It is a figure which shows the example of the matrix of the combination of several maximum value. It is a figure explaining the example of the weighting of an evaluation point. It is a flowchart figure explaining the pairing procedure in another modification.

Explanation of symbols

10: radar device, 11: antenna, 18: level peak detector, 34: pairing means,
35: Distance / speed detection means

Claims (4)

A radar wave that alternately repeats a frequency increase period in which the frequency gradually increases and a frequency decrease period in which the frequency gradually decreases is transmitted as a transmission signal to a predetermined angle range, and the transmission signal reflected by the target is received as a reception signal. And a radar device that detects the relative distance or relative speed of the target based on the received signal,
Level beat of the upbeat signal corresponding to the frequency difference between the transmission signal and the reception signal during the frequency increase period, and downbeat corresponding to the frequency difference between the transmission signal and the reception signal during the frequency decrease period Level peak detection means for detecting the level peak of the signal;
Among the plurality of first maximum values in the level peak group of the upbeat signal distributed in the angular direction and the plurality of second maximum values in the level peak group of the downbeat signal distributed in the angular direction, the local maximum Pairing means for associating the first and second maximum values based on the closeness of the values and the closeness of the angle at which the maximum value is formed;
Distance / speed detection means for detecting the relative distance or the relative speed of the target from the frequency of the upbeat signal indicating the first maximum value and the frequency of the downbeat signal indicating the second maximum value. And a radar apparatus. In claim 1,
The pairing means includes a plurality of combinations of the plurality of first maximum values and the plurality of second maximum values, a difference between the first and second maximum values, and the first and second values. A radar apparatus characterized in that weighting is performed on a difference between angles at which two local maximum values are formed, and the association is performed based on the difference between the weighted local maximum values and the difference between angles. In claim 1,
The pairing means has a first number of the second (or first) in which a difference in angle at which a maximum value is formed is within a specified value with respect to one first (or second) maximum value. When the local maximum value is detected, the first (or second) local maximum value is associated with the second (or first) local maximum value, and the first (or second) local maximum value is obtained. On the other hand, when a second number of the second (or first) maximum value that is larger than the first number and the difference in angle at which the maximum value is formed is within a specified value is detected, A plurality of combinations of the 1 (or second) local maximum value and the second (or first) local maximum value are associated based on the local maximum value and the angle at which the local maximum value is formed. Radar device. A radar apparatus that transmits a radar wave that alternately repeats a frequency rising period in which the frequency gradually increases and a frequency falling period in which the frequency gradually decreases to a predetermined angle range as a transmission signal, and receives the transmission signal reflected by the target as a reception signal. In the target detection method for detecting the relative distance or relative speed of the target based on the transmission signal and the reception signal,
Level beat of the upbeat signal corresponding to the frequency difference between the transmission signal and the reception signal during the frequency increase period, and downbeat corresponding to the frequency difference between the transmission signal and the reception signal during the frequency decrease period A level peak detection step for detecting a level peak of the signal;
Among the plurality of first maximum values in the level peak group of the upbeat signal distributed in the angular direction and the plurality of second maximum values in the level peak group of the downbeat signal distributed in the angular direction, the local maximum A pairing step for associating the first and second local maximum values based on the closeness of the values and the approximateness of the angle at which the local maximum is formed;
A distance / speed detection step of detecting a relative distance or a relative speed of the target from the frequency of the upbeat signal indicating the associated first maximum value and the frequency of the downbeat signal indicating the second maximum value. And a target detection method.

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