JP3114700B2 - FM-CW radar device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM-CW radar apparatus, and more particularly to a frequency-modulated continuous wave that is transmitted as a transmission wave toward a target such as an automobile, and is reflected back from the target. Incorporating the reflected wave as a received wave,
The present invention relates to an FM-CW radar device that detects a distance to the target and a relative speed to the target.

[0002]

2. Description of the Related Art Conventionally, an FM-CW (Frequency Module) capable of monitoring other vehicles mounted on a vehicle and traveling in front and behind and simultaneously measuring a distance and a relative speed with the other vehicles.
A dulation-continuous wave radar device is known (JP-A-6-138217, JP-A-7-120).
549, JP-A-9-288171, JP-A-10-20025, etc.). Also, in-vehicle radar devices include millimeter-wave radars that apply millimeter-wave radio waves.
Millimeter wave radar also has an FM-CW radar device.

[0003] This FM-CW radar apparatus transmits a continuous wave frequency-modulated (FM) by a triangular wave as a transmission wave to a target such as an automobile located ahead, and is reflected by the target and returned. The reflected wave is taken as a received wave, and a beat signal obtained by mixing the transmitted wave and the received wave at that time is subjected to signal processing by a frequency analysis method such as a fast Fourier transform (FFT), thereby obtaining a distance from the target. And a device for calculating the relative speed.

[0004] The FM-CW radar device is mounted on an automobile, and can monitor another automobile traveling in front or behind to simultaneously measure a distance and a relative speed.
By monitoring vehicles running ahead, they prevent rear-end collisions or collisions of vehicles, and are expected to be very useful in the future.

[0005] The distance in this FM-CW radar device,
For calculating the relative speed, the peak frequency indicating the target is used in the spectrum of the beat signal corresponding to the rising section and the falling section of the triangular wave. In the case of a single target, the distance R and the relative speed V are proportional to the sum and difference values of the peak frequencies from the peak frequency fa in the up section and the peak frequency fb in the down section, that is, R = A · ((Fa + fb) / 2) V = A · ((fa−fb) / 2) (A: constant) However, when there are a plurality of target objects, peaks corresponding to the number of the target objects appear in the spectrum of the up section and the down section.

In order to detect the distances and relative velocities of a plurality of targets, it is necessary to accurately combine the peaks of these up sections and the peaks of the down sections. Therefore, as one conventional method, the position of the target after a certain period of time is estimated from the distance and the relative speed of the target by all combinations of the peaks of the spectrum in the ascending section and the descending section, and the peaks that are in agreement are determined. In combination, distances and relative velocities of a plurality of targets are obtained.

[0007]

However, in the above-mentioned conventional FM-CW radar apparatus, when calculating the distance and the relative velocity, the target is detected in the spectrum of the beat signal corresponding to the rising section and the falling section of the triangular wave. The peak frequency shown is used, but when the relative speed of a plurality of adjacent targets is slow, the rate of change in the position of the target over time is small, and matching is achieved from all combinations of peaks. It takes time to detect peak combinations,
There are also problems such as detection of an incorrect combination.

[0008] The present invention has been made in view of the above points,
Calculate the degree of conformity of the peaks of the spectrum of the beat signal corresponding to the upper and lower sections of the triangular wave, and make the peak pair with a high degree of conformity a candidate for a peak combination of the target as a temporary peak pair, and associate it with the temporal change in the position of the target Accordingly, it is an object of the present invention to provide an FM-CW radar device capable of preventing an incorrect combination of peaks in upper and lower sections, finding an accurate peak pair, and accurately detecting a distance and a relative speed of a target.

[0009]

In order to achieve the above object, the present invention transmits a signal, which is frequency-modulated by a modulation signal having a fixed period, as a transmission wave toward a target, and transmits a reflected wave from the target. A transmitting / receiving means for receiving and obtaining a beat signal with a transmission wave, a frequency analyzing processor for extracting a spectrum of the beat signal by frequency analysis processing of the beat signal, and a spectrum obtained by the frequency analyzing A peak equal to or greater than a predetermined threshold is detected every half cycle, and a pair of peaks having a high degree of conformity is temporarily determined among peak pairs corresponding to the first half cycle and the second half cycle for each cycle of the modulated signal. As a candidate for a peak combination of a target as a peak pair, the temporal position of the temporary peak pair in the next cycle is estimated, and the target is determined based on the actual detected peak time position in the next cycle and the estimated time position. Confirm the carried out, and a target recognizing that calculates the relative speed between the distance and target from peak pair of targets that are determined by the target recognizer to the target, said target recognizer, modulated signal
The first half and second half of each cycle
All peak pairs detected in one half cycle
For the peak, the other half circumference corresponding to the detected peak
The peak search range for the period, and exists in that search range
Difference value and peak of interval integration between each peak and detected peak
Level difference value, the interval integration difference value and peak level
The degree of conformity is calculated based on the differential value of the
The first half and second half of each cycle
Of the pair of peaks, the pair with the highest matching
Peak pair and one of the peaks that make up the provisional peak pair.
If the peak constitutes another temporary peak pair, the temporary peak
Compare the degree of matching of the pair with the degree of matching of the other temporary peak pairs.
The peak pair with a higher degree of conformity as a temporary peak pair.
In this configuration, a provisional peak pair calculation process for selecting a target is performed .

Here, the target recognizer includes a peak frequency detector for detecting a peak equal to or higher than a predetermined threshold from a spectrum obtained by the frequency analyzer, and a first half cycle for each cycle of the modulated signal. And a target follower that determines whether or not a pair of peaks corresponding to the latter half cycle is at the estimated time position in the next cycle of the already determined target modulation signal, and follows the target, and a target other than the determined target. A tentative peak pair detector that sets a peak pair having a high degree of conformity to a new target as a tentative peak pair as a candidate for a peak combination of a target, and a tentative peak pair at a position substantially equal to the time position estimated in the previous cycle. A target determiner for determining whether there is a provisional peak pair detected by the detector and determining the target; The more from peak pairs and a detector for detecting a relative velocity between the distance and target to the target.

According to the present invention, a peak equal to or greater than a predetermined threshold is detected every half cycle of the modulated signal from the spectrum obtained by the frequency analysis processor, and the first half and the second half of each cycle of the modulated signal are detected. Of the pair of peaks corresponding to the half cycle of
Estimate the time position of the temporary peak pair in the next cycle as a candidate for the peak combination of the target as a temporary peak pair with the peak pair having a high degree of matching as the temporary peak pair, and determine the time position of the actual detected peak in the next cycle and the estimated time position The target is determined based on the target, and the distance from the peak pair of the determined target to the target and the relative speed with the target are calculated, so that the degree of matching is high without depending on the relative speed with the target. A target can be determined by selecting a peak pair having high reliability by using the consistency in the time series with the peak pair.

According to the present invention, there is provided a danger classifier for judging whether or not the apparatus is dangerous based on the distance to the target and the relative speed with respect to the target calculated by the target recognizer. And a warning device for generating a warning when the discrimination device determines that the danger is dangerous. According to the present invention, when the target is an obstacle, it is possible to determine the proximity of the obstacle and to issue an alarm.

[0013]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an FM-C according to the present invention.
FIG. 2 is a block diagram of an embodiment of a W radar device, and FIG.
FIG. 3 is a block diagram of an embodiment of a target recognizer in FIG. 1, and FIG.
5 is a flowchart for explaining the target recognizer shown in FIG. 4; FIGS. 7 and 6 are flowcharts for explaining a temporary peak pair calculation routine of the flowchart shown in FIG. 5; FIG. 6 is a flowchart for explaining the fixed target follow-up determination routine of the flowchart shown in FIG. 5, and FIG. 9 is a flowchart for explaining the temporary peak pair determination determination routine of the flowchart shown in FIG.

As shown in FIG. 1, the FM of this embodiment
The CW radar device includes a radar head 1, a low-pass filter (LPF) 2, an amplifier 3, an A / D converter 4, a microprocessor 5, and an alarm 6. The configuration of the radar head 1 itself is the same as that of the related art. As shown in FIG. 2, a transmitting antenna 11 and a receiving antenna 12 are provided, and a triangular wave having a fixed period shown in FIG. It is supplied as a control voltage to a control oscillator (VCO) 14, from which an FM modulated wave obtained by frequency-modulating the free-running oscillation frequency of the VCO 14 with a triangular wave is extracted.
The FM modulated wave, which is a continuous wave using the triangular wave as a modulation signal, is transmitted as a transmission wave from the transmission antenna 11 to the target through the directional coupler 15.

The transmitted wave is reflected by the target, and the reflected wave is received by the receiving antenna 12, supplied to the mixer 16, and frequency-converted to the FM modulated wave branched by the directional coupler 15. Here, the received reflected wave has a phase difference between the transmitted wave according to the distance between the radar device and the target and the Doppler shift due to the relative speed between the radar device and the target. Therefore, a beat signal indicating a frequency shift corresponding to the distance and the relative speed is extracted from the mixer 16. This beat signal is amplified by the amplifier 17 and then input to the low-pass filter (LPF) 2 in FIG.

In FIG. 1, the LPF 2 filters a low frequency component of the beat signal. Amplifier 3 is LPF2
Amplifies the beat signal filtered by the A / D converter 4
To supply. The A / D converter 4 converts an input signal into a digital signal and inputs the digital signal to the microprocessor 5.

The microprocessor 5 includes a frequency analysis processor 51, a target recognizer 52, and a danger discriminator 53. The frequency analysis processor 51 receives a synchronization signal synchronized with the cycle of the output triangular wave of the triangular wave generator 13 shown in FIG. 2 and also obtains a discrete value data of the beat signal sampled by the A / D converter 4 for a predetermined time. A spectrum is extracted by using a frequency component analysis method such as a fast Fourier transform (FFT). The target recognizer 52 calculates a distance and a relative speed from the FM-CW radar device to the target based on the spectrum calculated by the frequency analysis processor 51.

FIG. 3 is a block diagram showing an embodiment of the target recognizer 52. In the figure, a peak frequency detector 521 detects a peak having a certain threshold or more from the spectrum obtained by the frequency analysis processor 51. The target follower 522 determines whether or not there is a peak pair at the estimated position in the next cycle of the target that has already been determined, and follows the target. The temporary peak pair detector 523 obtains a peak pair having the highest degree of matching with a new target other than the confirmed target as a temporary peak pair.

The target determinator 524 determines whether the tentative peak pair obtained by the tentative peak pair detector 523 is located at the position estimated in the previous cycle, and determines the target. The distance and relative speed detector 525 detects the distance and the relative speed between the radar device and the target from the peak pair of the determined target.

The danger classifier 53 includes a target recognizer 52
The degree of danger to the target is determined from the distance and the relative speed obtained in. The alarm device 6 warns the driver of the vehicle equipped with the FM-CW radar device with an alarm display or an alarm sound according to the degree of danger determined by the danger classifier 53. That is, as shown in FIG. 11, in front of an automobile (hereinafter referred to as a radar car) 21 on which the FM-CW radar device is mounted,
For example, in a case where three preceding vehicles 22, 23, and 24 are running, the leading vehicles 22 to 23 in an ascending section that is a monotonically increasing section of a half cycle of a triangular wave and a descending section that is a monotonically decreasing section of a half cycle, respectively. 24, it is possible to measure the distance and relative speed between them by receiving the reflected waves,
As a result, the preceding vehicles 22 and 23 traveling in the same direction
And collision with the preceding vehicle 23 running in the opposite direction can be avoided.

In this embodiment, an FM-CW radar apparatus which detects a distance to a target such as a preceding vehicle and a relative speed with respect to the target using a radio signal is processed by processing the radio signal. A frequency analysis processor 51 for extracting a spectrum related to an object, a peak frequency detector 521 for detecting a peak frequency of the spectrum, a target follower 522 for determining following of the target from the peak frequency, and a new target A temporary peak pair detector 523 for obtaining a temporary peak pair for an object, and a target determiner 5 for determining the determination of the new target from the temporary peak pair.
24, and a distance and relative speed detector 525 for detecting the distance and relative speed to the target object. Next, the operation principle of the microprocessor 5 of FIG. Will be described in detail.

The microprocessor 5 is supported by various operation programs such as a frequency analysis processor 51 in addition to the main routine. When the ignition key is operated and the power is turned on in order to operate the engine of the vehicle equipped with the FM-CW radar device, the reset of the microprocessor 5 is canceled after a certain period of time. Upon reset release, the microprocessor 5 is started, executes the program from the zero address, and starts the main routine according to the flowchart shown in FIG.

In this main routine, first, initialization is performed, various variables are initialized (step S1), and then a frequency analysis process is performed (step S2). This frequency analysis processing will be described with reference to FIG. The transmitted wave transmitted from the radar head 1 is reflected on the target and returns as a reflected wave, and a beat signal is generated from the transmitted wave and the received reflected wave. The A / D converter 4 starts the A / D conversion of the beat signal at the same time as the output of the frequency-modulated (FM-modulated) radio wave by the triangular wave.

The discrete data of the beat signal is stored in the microprocessor 5 one by one from the A / D converter 4. The A / D conversion is performed at a constant sampling time, and therefore, a timer interrupt or the like is generally used for monitoring the sampling time. The discreteization of the beat signal by the A / D converter 4 is executed for one cycle of the triangular wave shown in FIG. In one cycle of the triangular wave, the discrete value data of the beat signal corresponding to the rising section and the falling section of the triangular wave is stored in the microprocessor 5.

From the discrete value data of the beat signal corresponding to the rising section and the falling section of the triangular wave, a discrete spectrum of each section can be obtained by a frequency analysis technique represented by FFT (etc.). This is the frequency analysis processing in step S3.

Subsequently, based on the discrete spectrum obtained in step S2, a target recognition process is performed in which a combination of peaks in the rising section and the falling section of the triangular wave is determined to detect the distance and the relative speed (step S2). S3) Then, the degree of danger to the own vehicle is determined based on the distance and the relative speed obtained in step S3 (step S4).
When it is determined that the degree of danger is high, the driver is alerted by an alarm display using the alarm 6 in FIG.

Next, the target recognition processing operation of step S3 by the target recognizer 52, which is a main part of the present embodiment, will be described in detail with reference to the flowchart of FIG. First, a peak in an upward section of the triangular wave is detected from a discrete spectrum. Normally, the peak position is detected by extracting a spectrum having a certain threshold or more and obtaining its center frequency. Similarly, the peak of the downward section of the triangular wave is detected (step S1).
0). In this way, the same number of spectrum peaks as the number of target objects are detected in the upper and lower sections.

Next, a follow-up determination of a confirmed target already recognized as a target is performed (step S).
11). The determination of the following of the confirmed target will be described in detail with reference to FIGS.

First, it is checked whether or not there is a fixed target already recognized as a target (step S50 in FIG. 6). The confirmed target indicates a target recognized as a target in the determination of a temporary peak pair, which will be described later. If there is no confirmed target, there is either only an undetermined target or there is no peak of the spectrum equal to or higher than the threshold value, and the return processing is performed without executing the tracking determination.

On the other hand, if there is a fixed target, it is checked whether or not the tracking determination has been performed for all the fixed targets (step S51 in FIG. 6). If the tracking determination has been performed for all the fixed targets, a return process is performed.
If the tracking determination has not been performed for all the confirmed targets, the tracking determination is performed for the unconfirmed confirmed targets.

If there is an unconfirmed confirmed target, it is determined whether there is a peak pair at the previously estimated position (step S52 in FIG. 6). This follow-up determination process is shown in FIG.
This will be described in detail with reference to FIG. In FIG. 10, time t = N
It is assumed that two targets have been determined. Each target is (PKup1 (N), PKdn1
(N)) and (PKup2 (N), PKdn2 (N)) peak pairs. At this time, the next cycle t
Estimate the position of both targets at = N + 1. Therefore,
Both estimated targets are identified as (PKup1R (N), PK
dn1R (N)), (PKup2R (N), PKdn2
R (N)).

In the next cycle t = N + 1, it is checked whether or not there is a peak pair at the position estimated at t = N. In this case, at t = N + 1 in FIG. 10, the peak pair (PKup1 (N
+1), PKdn1 (N + 1)), it is determined that the target determination has been updated, that the tracking determination has been completed in step S53 of FIG. 6, and that the peak pair (PKup
1 (N + 1), PKdn1 (N + 1)) are newly set as the determined targets.

On the other hand, if there is no peak pair at a position substantially equal to the estimated position indicated by the dotted line at t = N + 1 in FIG. 10, the determined target (PKup1 (N), PKdn1 (N)) is determined in step S54 in FIG. ) Is not recognized as a target, and it is determined that the target has disappeared.

In step S55 of FIG. 6, the updated fixed targets (PKup1 (N + 1), PKdn1 (N
+1)), the estimated position (PKu) in the next cycle t = N + 2
p1R (N + 1), PKdn1R (N + 1)) are obtained. The estimated position obtained here is the next cycle t = N + 2
Is used to determine the following of the determined target.

In step S56 of FIG. 6, step S5
3 (PKup1 (N +
1), PKdn1 (N + 1)) are excluded from peak candidates for provisional peak pair calculation described later. Next, step S5 is performed again.
Returning to step 1, it is determined whether all the confirmed targets have been examined. If all the confirmed targets have been examined and the following determination has been completed, the subroutine of the confirmed target following determination returns to the main routine.

After the determination of following the determined target in step S11 is completed, a temporary peak pair is calculated in step S12 of FIG. 5 for the remaining peaks excluding the determined target updated in step S56. Next, the process of calculating the temporary peak pair will be described in detail with reference to FIGS. 7 and 8 and FIGS.

Now, as shown in FIG. 11, a car (hereinafter referred to as a radar car) 21 on which the FM-CW radar device of this embodiment is mounted is located 3
It is assumed that two preceding vehicles 22, 23 and 24 are running. A beat signal obtained by transmitting and receiving a radio wave FM-modulated by a triangular wave shown in FIG. 12 is converted into a discrete value, and a spectrum obtained by frequency analysis such as FFT by the frequency analysis processor 51 is, for example, as shown in FIG. Become. At this time, the combination of the spectral peaks in the up and down sections of the triangular wave is completely unknown. 7, 8 and 13
This will be described in detail below.

In the process of calculating the temporary peak pair in step S12, it is first checked whether or not there is an unsearched peak in the up section (step S21 in FIG. 7). This is because the peaks in the down section are sequentially calculated as temporary pair pairs in correspondence with the peaks in the up section. If there is an unsearched peak in the up section, the process proceeds to step S22. If all the peaks have been searched, the process proceeds to step S23. Here, since it is the first search, the process proceeds to step S22 in FIG.

In step S22, the lowest frequency peak in the up section is selected and set as PKup (i). This is because a tentative peak pair is obtained by sequentially searching from peaks having lower frequencies. In this example, PKup1 in FIG. 13 is selected. Subsequently, a temporary peak pair search range in the down section for PKup (i) is set (step S2 in FIG. 7).
4). This limits the range in which the peak of the down section corresponding to PKup (i) exists, and thus the provisional peak pair can be efficiently calculated. Actually, when the relative speed is zero, the peak positions of the ascending section and the descending section match, but when the relative speed is not zero, the positions are different. Here, the detection range of the relative speed is, for example, ± 200 km.
/ H, the search range of the downstream section is determined accordingly.

Subsequently, peaks in the search range of the down section are searched in order, and it is checked whether or not there is an unsearched peak (step S25 in FIG. 7). In this example, FIG.
Search range 3 of the down section corresponding to the peak PKup1 of No. 3
1 has a peak PKdn1 and a peak PKdn2. If there is no unsearched peak in the search range 31, the process returns to step S21. However, since there is an unsearched peak, the process proceeds to step S26.

In step S26, the lowest frequency peak in the search range of the down section is selected and set as PKdn (j). This is because a tentative peak pair is obtained by sequentially searching from peaks having lower frequencies. In the example of FIG.
Kdn1 is chosen as PKdn (j).

Subsequently, the peak PKup (i) in the up section
The difference IDEF of the integral of the interval between the peak PKdn (j) of the descending interval and the peak PKdn (j) is calculated (step S27 in FIG. 7). The integral value of the peak PKup (i) is calculated within a preset integration interval (indicated by 32 in FIG. 13). As shown below, the integral value of the peak PKup (i) is calculated as follows.

ΔPKup (i) = ΣPWSup (fup) (1) Further, the integrated value of the peak PKdn (j) is similarly calculated as follows.

ΔPKdn (j) = ΣPWSdn (fdn) (2) From the above both integral values, the difference IDEFij of the interval integral is calculated by the following equation.

IDEFij = | ΔPKup (i) −ΔPKdn (j) | (3) In the example of FIG. 13, the difference IDEF11 of the section integration between the peak PKup1 in the up section and the peak PKdn1 in the down section.
Can be calculated by the following equation.

IDEF11 = | ΔPKup1-ΔPKdn1 | (4) Subsequently, a peak level difference PLDE between the peak PKup (i) in the ascending section and the peak PKdn (j) in the descending section.
F is calculated (step S28 in FIG. 7). As the peak levels of the peaks PKup (i) and PKdn (j), the peak having the highest level in the preset integration section is selected. In step S28, the difference between the peak levels can be calculated by the following equation.

PLDEF = | PKup (i) max−PKdn (j) max | (5) In the example of FIG. 13, the peak level difference PLDE between the peak PKup1 in the up section and the peak PKdn1 in the down section.
F can be calculated by the following equation.

PLDEF = | PKup1max-P
Kdn1max | (6) Subsequently, the degree of spectral adaptation Wij is calculated from the difference IDEF of the section integration and the difference PLDEF of the peak level by the following equation, and PKdn (j) forming a pair with the peak PKup (i) is calculated as one. Set PPi of peak pairs as a set
(Step S29 in FIG. 7).

Wij = 1 / (IDEF × PLDEF) (7) In the example of FIG. 13, W11 is calculated and the set PPi is calculated.
{(PKup1, PKdn1)} as an element.

When the process in step S29 is completed, the process returns to step S25 to check whether there is any unsearched peak in the search range of the down section. In the example of FIG.
Since the peak PKdn2 exists in the search range 31 of the down section corresponding to Kup1, the process proceeds to step S26 again.

In steps S26 to S29, in the same manner as above, the difference IDEF of the interval integration, the difference PLDEF of the peak level, and the degree of spectrum matching W
12 is calculated and the peak pair set PPi ｛(PKu
p1, PKdn1), (PKup1, PKdn2)} as elements.

Returning to step S25, it is checked whether or not there is an unsearched peak in the search range of the down section. FIG.
In the example of No. 3, since there is no unsearched peak in the search range 31 of the downstream section corresponding to the peak PKup1, the process proceeds to step S21. In step S21, it is checked whether there is an unsearched peak in the up section. In the example of FIG.
Since there are unsearched peaks PKup2 and PKup3 in the up section, the process proceeds to step S22 again.

From the next step S22, the peak P
As in the case of Kup1, an unsearched peak PKup
After setting a temporary peak pair search section in the down section for (i), the degree of spectrum matching Wij with the peak PKdn (j) present in the search range is obtained and added to the peak pair set PPiＰＰ. In the example of FIG. 13, the peak PKu
Peak PKdn1 and peak P within the search range for p2
Kdn2 are present, and the respective degrees of conformity W21
And W22 are calculated, and a set of peak pairs PP2 ｛(PK
up, PKdn1), (PKup2, PKdn2)}
Add to

Similarly, for the peak PKup3, the peak PKdn3 exists within the search range, and the degree of matching W33 is calculated and added to the peak pair set PP3 {(PKup3, PKdn3)}.

When returning to step S21, all peaks in the up section have been searched.
Proceed to 3. In step S23, in order to search again for each peak in the up section again, all the attributes of the peaks that have been searched in steps S21 and S25 are left unsearched, and FIG.
Go to step S30.

In step S30, it is checked whether there is an unsearched peak in the up section. This is because the peaks in the down section are sequentially selected from the set of peak pairs as temporary peak pairs corresponding to the peaks in the up section. If all have not been searched, the process proceeds to step S31. If all have been searched, the process returns to the main routine. Here, since it is the first search, the process proceeds to step S31. In step S31, the peak of the lowest frequency in the up section is selected and set as PKup (i). This is because a temporary peak pair is selected from a set of peak pairs by sequentially searching for peaks having lower frequencies. In the example of FIG. 13, PKup1 is selected.

Subsequently, a pair having the highest matching degree from the peak pair set PPi ｛｝ of the peak PKup (i) is set as a temporary peak pair SPP (i, j), and is set as a candidate for the peak combination of the target (step in FIG. 8). S32). This is because the peak pair of the up section and the down section is more matched (the correlation is stronger) as the difference IDEF of the above-mentioned section integration and the difference PLDEF of the peak level are smaller. This is because the higher (the larger) the higher the probability of being a true peak pair. FIG.
In the example of No. 3, a set PP of a peak pair of the peak PKup1
The peak pair (PKup
1, PKdn1) as a temporary peak pair SPP (1, 1).

Subsequently, it is checked whether or not the peak PKdn (j) in the descending section of the temporary peak pair selected in step S32 has already formed a temporary peak pair (step S33 in FIG. 8). This is the set of all peak pairs PPi
This is because the peak pair having the highest matching degree from ｛｝ is set as the temporary peak pair. In the example of FIG. 13, the peak PKdn
Since No. 1 does not form a temporary peak pair, step S30
Return to

In step S30, it is checked whether or not there is a peak in an unsearched up section. If there is, a tentative peak pair is converted into a peak pair set PP by the same steps.
Select from i ｛｝. In the example of FIG. 13, when the search of all the up sections is completed, the provisional peak pair SPP (1,
1), SPP (2, 2) and SPP (3, 3) are calculated.

Here, the case where it is determined in step S33 that the peak PKdn (j) forming the provisional peak pair has already formed the provisional peak pair will be described with reference to both FIGS. 14 and 15. First, the example of FIG. 14 will be described. In this example, two peaks PKdn2 and PKdn3 in the down section can be recognized as peaks, but a part of the spectrum overlaps. In this example, up to step S23, each spectrum matching degree Wij and peak pair set PP
It is assumed that i ｛｝ is required.

In step S30, it is checked whether there is an unsearched peak in the up section. This is because the peaks in the down section are sequentially selected from the set of peak pairs as temporary peak pairs corresponding to the peaks in the up section. If all have not been searched, the process proceeds to step S31. If all have been searched, the process returns to the main routine. Here, since it is the first search, the process proceeds to step S31.

In step S31, the peak of the lowest frequency in the up section is selected and set as PKup (i). This is because a temporary peak pair is selected from a set of peak pairs by sequentially searching for peaks having lower frequencies. In the example of FIG. 14, PKup1 is selected. In step S32, a pair having the highest degree of matching is determined from the peak pair set PPi ｛｝ of the peak PKup (i) as the provisional peak pair SPP (i, j).
And In the example of FIG. 14, the peak pair (PKup1, PKdn1) having the highest degree of matching is set as the temporary peak pair SPP from the peak pair set PPi ｛｝ of the peak PKup1.
(1, 1).

In step S33, the peak PKdn in the down section of the temporary peak pair selected in step S32
(J) checks whether a temporary peak pair has already been formed. This is because the peak pair having the highest matching degree from the set PPi # of all peak pairs is set as the temporary peak pair. In the example of FIG. 14, since the peak PKdn1 does not form a temporary peak pair, the process returns to step S30.

In step S30, it is checked again whether there is an unsearched peak in the up section. In the example of FIG.
The peak PKup2 and the peak PKup3 have not been searched.
Further, in step S31, the peak PKup2 of the lowest frequency in the up section is selected. In step S32,
From the peak pair set PP2 # of the peak PKup2, the peak pair with the highest degree of matching (PKup2, PKdn)
1) is a temporary peak pair SPP (2, 1).

In step S33, it is checked whether or not the peak PKdn1 in the downstream section of the temporary peak pair selected in step S32 has already formed a temporary peak pair. In the example of FIG. 14, the peak PKdn1 is already the peak PKup
Since one temporary peak pair is formed, step S in FIG.
Proceed to 34.

In step S34, the peak in the ascending section that forms a temporary peak pair with the peak PKdn (j) in the descending section is set as PKup (k). In the example of FIG.
Since Kdn1 has already formed a temporary peak pair with the peak PKup1, the peak PKup1 is selected.

Subsequently, both temporary peak pairs (PKup
(I), PKdn (j)), (PKup (k), PKd
n (j)) is compared (step S35 in FIG. 8). In the example of FIG. 14, the matching degree W11 of the temporary peak pair (PKup1, PKdn1).
And which of the degrees of matching W21 of the temporary peak pair (PKup2, PKdn1) is higher. Fit degree W of provisional peak pair (PKup (i), PKdn (j))
ij is a temporary peak pair (PKup (k), PKdn
If it is higher than the matching degree Wkj of (j)), step S
Proceed to step S36, and if it is low, proceed to step S37.

In step S36, the provisional peak pair (PK
up (i), PKdn (j))
Since the degree of conformity is higher than Wkj, the provisional peak pair SPP
(K, j) is released. Subsequently, a peak pair set PP
A peak pair having the next highest degree of matching from K ｛｝ is set as a temporary peak pair SPP (k, m) (step S3 in FIG. 8).
8).

On the other hand, in step S37, the matching degree Wk of the temporary peak pair (PKup (k), PKdn (j))
Since j is higher than the matching level Wij, the peak pair having the next highest matching level is set as the temporary peak pair SPP (i, n) from the peak pair set PPiＰＰ.

In the example of FIG. 14, the provisional peak pair (PKup
1, PKdn1) is equal to (PKup
2, PKdn1), which is higher than the matching degree W21, so that in step S36, the provisional peak pair (PKup2, P
Kdn1), that is, SPP (2, 1) is released. Then, since the provisional peak pair SPP (2,1) has been released, in step S38, the provisional peak pair corresponding to the peak PKup2 is extracted from the peak pair set PP2 # using the next highest peak pair (PKup2, PKdn).
2) is a temporary peak pair SPP (2, 2).

When the processing in step S37 or S38 is completed, the flow returns to step S30 to check whether or not there is an unsearched peak in the up section. In the example of FIG. 14, the peak PK
Since up3 has not been searched, the peak PKup3 is selected in the following step S31. Subsequently, in step S32, the peak pair (PKup3, PKdn3) having the highest degree of matching from the peak pair set PP3 # is set as the temporary peak pair SPP (3,3).

In step S33, since the peak PKdn3 does not form a temporary peak pair, the process returns to step S30. In step S30, it is checked whether there is an unsearched peak in the up section. However, since all the peaks have already been checked, the process returns to the main routine.

FIG. 15 shows the peak PK in FIG.
This is the case where dn2 and peak PKdn3 overlap. In this case, according to a series of temporary peak pair detection flowcharts, the peak pair (PKup1, PKdn1) is the temporary peak pair SPP (1, 1) and the peak pair (PKup3, PKK1).
dn3) becomes a temporary peak pair SPP (3, 3), and the peak PKup2 becomes floating because the paired peak does not exist in the down section.

The temporary peak pair calculation processing S12 described above
When the routine is completed, the determination of the provisional peak pair is made in step S13 shown in FIG. This step S1
The process of determining the provisional peak pair 3 is a process for determining a newly appearing target as a target.

Next, the process of determining the provisional peak pair will be described in detail with reference to FIGS. 9 and 16. First,
In step S60 of FIG. 9, it is checked whether or not there is a temporary peak pair that has already been determined. If there is no provisional peak pair that is being determined, either a new target has appeared in this cycle or no new target exists, and the estimated positions of all the provisional peak pairs in the next cycle are calculated. (Step S61 in FIG. 9), after the calculation, the process returns to the target recognition routine.

On the other hand, if it is determined in step S60 that there is a provisional peak pair for which the determination is being made, it is checked whether or not the determination has been performed for all the temporary peak pairs (step S62 in FIG. 9). Is performed, the return process is performed. If all of the temporary peak pairs have not yet been confirmed, the final determination is performed on the unconfirmed temporary peak pairs (step S in FIG. 9).
63).

This will be described with reference to FIG. It is assumed that at time t = N, two temporary peak pairs in the above-described triangular wave ascending section and descending section are obtained. Each target is (PKup1 (N), PKdn1
(N)) and (PKup2 (N), PKdn2 (N)). At this time N, the positions of both targets in the next cycle t = N + 1 are estimated. Then, both estimated targets are referred to as (PKup1R (N),
PKdn1R (N)), (PKup2R (N), PKd
n2R (N)).

In the next cycle t = N + 1, it is checked whether a temporary peak pair exists at the position estimated at t = N. In this case, at t = N + 1 in FIG. 16, the provisional peak pair (PKup1) is located at a position substantially equal to the estimated position indicated by the dotted line.
If (N + 1), PKdn1 (N + 1)) exists, the number of times of determination of the provisional peak pair is counted up (step S64 in FIG. 9).

Next, it is determined whether the number of times of determination of the provisional peak pair is equal to or greater than a predetermined number of times (FIG. 9).
Step S66). When the number reaches the predetermined number or more, the provisional peak pair is determined as the target (step S67 in FIG. 9). Note that the determined target is subject to the following determination of the determined target from the next cycle. If the number of determinations does not reach the predetermined number or more in step S66, an estimated position in the next cycle of the temporary peak pair is determined for determination in the next cycle (step S6 in FIG. 9).
8). In the case where the target is determined as the target in step S67, a similar determination is made for the following determination in the next cycle.
In step S68, an estimated position of the temporary peak pair in the next cycle is determined.

On the other hand, when there is no provisional peak pair at a position substantially equal to the estimated position indicated by the dotted line at t = N + 1 in FIG. 16, the provisional peak pair (PKup1
(N), PKdn1 (N)) are reset (step S65 in FIG. 9).

After the processing in step S68 or S65, the process returns to step S62 again to determine whether all the temporary peak pairs have been checked. If all the temporary peak pairs have been checked and the determination has been completed, the temporary peak pair determination has been completed. From the subroutine to the main routine.

Referring back to FIG. 5, after the provisional peak pair calculation process in step S13 is completed, the flow advances to step S14 to determine the distance R to the determined target and the relative speed of the determined target. V is obtained by the following equation.

R = kr × {(PKup1 (N) + PKdn1 (N)) / 2} (8) V = kv × {(PKup1 (N) −PKdn1 (N)) / 2} (9) In the above, kr and kv are constants determined by each parameter of the FM-CW radar device. The target determined by the above method is recognized as being recognized, and is followed up until it disappears outside the radar detection range.

As described above, the target recognizer 52
When the target recognition processing operation of step S3 is completed, the danger classifier 53 of FIG. 1 determines whether the recognized target is dangerous to the own vehicle based on the distance R and the relative speed V (FIG. 4). Step S4). When the danger classifier 53 determines that the degree of danger calculated is higher than a certain value and is danger, the alarm device 6 generates an alarm sound to notify the driver. Thus, the driver can avoid danger.

[0085]

As described above, according to the present invention,
From the spectrum obtained by the frequency analysis processor, a peak equal to or higher than a certain threshold is detected every half cycle of the modulation signal,
Of the peak pairs corresponding to the first half cycle and the second half cycle of each cycle of the modulated signal, a peak pair having a high degree of matching is set as a temporary peak pair as a candidate for a peak combination of the target, and a temporary pair of the next cycle is selected. Estimate the time position of the peak pair, determine the target based on the time position and the estimated time position of the actual detected peak in the next cycle, and determine the distance from the determined target peak pair to the target and the target. By calculating the relative speed of the target, the target is determined by selecting the peak pair with high reliability and the peak pair with high reliability without depending on the relative speed with the target object and using the consistency in the time series. I decided to
Compared to a conventional device that obtains a matched combination from all combinations of peak pairs, it is possible to calculate the distance to the target and the relative speed to the target at a high speed, particularly for a target having a low relative speed, and Accurate distances and relative speeds of a plurality of targets can be calculated at high speed and accurately.

The shape and level of a peak detected according to the shape and size of a target such as a large truck or an ordinary passenger car are different, but conventionally, when the movement of the target is similar, the shape of the target is changed. While the target may be erroneously recognized even if different, according to the present invention, a peak pair in which the shape and size of the peak are similar is selected as having a high degree of matching, It is possible to calculate the distance to the target and the relative speed with respect to the target more accurately than before, without misidentifying the target.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the device of the present invention.

FIG. 2 is a block diagram of an example of a radar head in FIG.

FIG. 3 is a block diagram of an embodiment of a target recognizer in FIG. 1;

FIG. 4 is a main routine of the operation of the microprocessor in FIG. 1;

FIG. 5 is a flowchart for explaining the operation of the target recognizer in FIG. 1;

FIG. 6 is a flowchart for explaining a follow-up determination process of a fixed target in FIG. 5;

FIG. 7 is a flowchart (part 1) for explaining a provisional peak pair calculation process in FIG. 5;

FIG. 8 is a flowchart (part 2) for explaining a temporary peak pair calculation process in FIG. 5;

FIG. 9 is a flowchart for explaining a temporary peak pair determination determination process in FIG. 5;

FIG. 10 is an explanatory diagram of a determined target following determination according to the present invention.

FIG. 11 is a diagram showing an example of an application example of the device of the present invention.

FIG. 12 is a diagram illustrating an example of a triangular wave used in the present invention.

13 is an explanatory diagram of a temporary peak pair calculation process in FIG.

FIG. 14 is an explanatory diagram of a provisional peak pair calculation process in FIG. 5;

FIG. 15 is an explanatory diagram of a provisional peak pair calculation process in FIG. 5;

FIG. 16 is an explanatory diagram of a target determination process in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Radar head 2 Low-pass filter (LPF) 3 Amplifier 4 A / D converter 5 Microprocessor 6 Alarm 31 Search range 32 Integration section 51 Frequency analysis processor 52 Target recognizer 53 Danger classifier 521 Peak frequency detector 522 Target Follower 523 Temporary peak pair detector 524 Target determiner 525 Distance and relative velocity detector

Continuation of the front page (56) References JP-A-8-94749 (JP, A) JP-A-6-207797 (JP, A) JP-A-11-38129 (JP, A) JP-A-5-232214 (JP) , A) JP-A-4-343308 (JP, A) JP-A-7-63842 (JP, A) JP-A-7-77575 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB G01S 13/34 G01S 13/93

Claims (3)

(57) [Claims] 1. A transmission / reception means for transmitting a signal frequency-modulated by a modulation signal having a fixed period to a target as a transmission wave, receiving a reflected wave from the target, and obtaining a beat signal with the transmission wave. A frequency analysis processor for performing frequency analysis processing on the beat signal to extract a spectrum of the beat signal; and a constant threshold value for each half cycle of the modulation signal from a spectrum obtained by the frequency analysis processor. The above peaks are detected, and a peak pair having a high degree of matching is set as a temporary peak pair among the peak pairs corresponding to the first half period and the second half period for each period of the modulation signal, and the peak of the target object is detected. As a candidate for the combination, the time position of the temporary peak pair in the next cycle is estimated, and the target is determined based on the time position and the estimated time position of the actual detected peak in the next cycle, And from peak pair of the determined target chromatic and target recognition unit for calculating a relative velocity between the distance and target until the target, the target recognizer
Are the first half and the second half of each cycle of the modulation signal.
One half period of the peak pair corresponding to the period
For all peaks detected in
Find the corresponding peak search range in the other half cycle,
A distinction is made between each peak present in the search range and the detected peak.
The difference value of the inter-integral and the difference value of the peak level are obtained, and
Based on the difference value of the inter-integration and the difference value of the peak level
The degree of conformity is calculated, and the first half of each cycle of the modulation signal is calculated.
Of the pair of peaks corresponding to the half cycle of the
Of which, the pair with the highest degree of matching is the temporary peak pair.
One of the peaks constituting the temporary peak pair is
When a peak pair is formed, the provisional peak pair
Compare the degree of matching and the degree of matching of the other temporary peak pair,
Select a peak pair with a high degree of conformity as a temporary peak pair
FM processing for calculating a temporary peak pair
-CW radar equipment. 2. The method according to claim 1, wherein the target recognizer includes a peak frequency detector for detecting a peak equal to or greater than a predetermined threshold from a spectrum obtained by the frequency analyzer, and a first half cycle for each cycle of the modulation signal. A target follower that determines whether or not the peak pair corresponding to the latter half cycle is at the estimated time position of the already determined target in the next cycle of the modulated signal, and follows the target; A temporary peak pair detector that sets a peak pair having a high degree of matching among the peak pairs with respect to a new target other than the target as a temporary peak pair and is a candidate for a peak combination of the target object, and a time position estimated in the previous cycle. A target determiner that determines whether or not there is a temporary peak pair detected by the temporary peak pair detector at an equal position to determine a target, A detector for detecting a distance from the determined target peak pair to the target and a relative speed to the target, and the temporary peak pair detector
Are the first half and the second half of each cycle of the modulation signal.
One half period of the peak pair corresponding to the period
For all peaks detected in
Find the corresponding peak search range in the other half cycle,
A distinction is made between each peak present in the search range and the detected peak.
The difference value of the inter-integral and the difference value of the peak level are obtained, and
Based on the difference value of the inter-integration and the difference value of the peak level
The degree of conformity is calculated, and the first half of each cycle of the modulation signal is calculated.
Of the pair of peaks corresponding to the half cycle of the
Of which, the pair with the highest degree of matching is the temporary peak pair.
One of the peaks constituting the temporary peak pair is
When a peak pair is formed, the provisional peak pair
Compare the degree of matching and the degree of matching of the other temporary peak pair,
Select a peak pair with a high degree of conformity as a temporary peak pair
2. The FM-CW radar apparatus according to claim 1, wherein a temporary peak pair calculation process is performed . 3. A danger classifier for judging whether or not the apparatus is dangerous based on a distance to the target and a relative speed with respect to the target calculated by the target recognizer. 2. The FM-CW radar device according to claim 1, further comprising: an alarm device for issuing an alarm when the discriminator determines that there is danger.