JP3104599B2 - 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 an FM-CW radar apparatus suitable for accurately detecting a plurality of objects existing in front of a vehicle.

[0002]

2. Description of the Related Art Conventionally, a technique for realizing a vehicle-mounted radar device using an FM-CW radar device has been proposed.
For example, JP-A-7-49377 discloses a steer-type in-vehicle radar device using an FM-CW radar device as a target object detection mechanism. The radar apparatus has a function of estimating the position of a preceding vehicle traveling on the own lane from the traveling state of the vehicle and steering the radar antenna of the FM-CW radar apparatus at that angle. According to such a configuration, the possibility of the preceding vehicle being lost while traveling on a curve can be reduced, so that a high accuracy of object recognition can be obtained in the on-vehicle radar device.

[0003] In the FM-CW radar device, a transmission wave whose frequency is increased or decreased at a predetermined rate of change is transmitted from a radar antenna toward a detection area. When an object is present in the detection area, the reflected wave reaches the object after a propagation time τ corresponding to the distance between the object and the radar antenna, and a reflected wave is generated. The generated reflected wave reaches the radar antenna after a propagation time τ corresponding to the distance between the target object and the radar antenna.

[0004] In the FM-CW radar apparatus, the reflected wave reaching the radar antenna and the transmitted wave at that time are mixed as described above, so that the frequency deviation between the reflected wave and the transmitted wave is set as a variable frequency, and the reflected wave is changed. A beat signal having an amplitude corresponding to the intensity of the beat is generated. By performing a known FFT process on the beat signal generated as described above and performing frequency analysis, it is possible to obtain the spectral intensity of each frequency component included in the beat signal. The FM-CW radar apparatus has a spectrum analysis result (hereinafter, referred to as an up section spectrum) of a beat signal obtained in a process of rising a reflected wave, and a spectrum of a beat signal obtained in a process of falling of a reflected wave. Using the analysis result (hereinafter, referred to as a down section spectrum), the distance to the object and the FM
Calculate the relative speed of the object with respect to the CW radar device.

When a plurality of objects exist in the detection area of the FM-CW radar device, reflected waves are generated for each of the objects. When a plurality of reflected waves are generated in this way, a plurality of spectrum peaks are formed in the result of the spectrum analysis of the beat signal. In this case, in order to accurately detect a plurality of objects, it is necessary to appropriately combine a plurality of spectrum peaks included in an up-link spectrum and a plurality of spectrum peaks included in a down-link spectrum.

The above-mentioned conventional on-vehicle radar apparatus uses a frequency pairing method of pairing spectrum peaks in the order of frequency when a plurality of spectrum peaks exist in an up section spectrum and a down section spectrum, and the shape of the spectrum peak. , And appropriate pairing is achieved by using both of the correlation pairing techniques of pairing those having a high correlation.

When there is no large relative velocity difference between a plurality of objects existing in the detection area, the peak spectrum of the object having a relatively small relative distance is not detected in both the up section spectrum and the down section spectrum. Meanwhile, the peak spectrum of the object having a large relative distance appears on the high frequency side. Therefore, under such circumstances, accurate pairing can be performed by the above method.

On the other hand, when there is a large relative velocity difference between a plurality of objects existing in the detection area, the order of the spectral peaks of the same object is different between the upstream section spectrum and the downstream section spectrum. May appear. In this case, accurate pairing cannot be performed by the above method. However, the spectral peaks appearing in the up-going spectrum and the spectral peaks appearing in the down-going spectrum show a high correlation in shape if they are due to the same object, while they are the same. If it is not caused by the object, no high correlation is shown in the shape. Therefore, after the pairing is performed by the above method, by calculating the degree of correlation of the paired spectral peaks,
It is possible to determine whether proper pairing has been performed. Further, when it is determined that the correlation is low, if the pairing is performed again by the above-described method, accurate pairing can be performed.

Therefore, according to the above-mentioned conventional on-vehicle radar device, when a plurality of objects exist within the irradiation range of the FM-CW radar device, the plurality of objects can be recognized with high accuracy. Can be. Further, as described above, the above-described conventional on-vehicle radar device includes the F
The M-CW radar device can accurately illuminate the own lane. Therefore, according to the above-mentioned conventional on-vehicle radar device, it is possible to obtain an effect that a plurality of objects existing on the own lane can be detected with high accuracy.

[0010]

In order to widely monitor the front of the vehicle, it is effective to use a scanning radar device for the on-vehicle radar device. F for the object detection mechanism
According to the scanning radar device using the M-CW radar device, for each of a plurality of objects existing within a relatively large detection area, the distance to the object and the relative speed of the object can be detected, It is possible to detect the direction in which the target object exists with respect to the own vehicle.

In order to accurately detect the direction in which the target object exists relative to the host vehicle, it is necessary to calculate an up-spectrum spectrum and a down-segment spectrum for each predetermined scanning angle, and to perform a detection process for the target for each scanning angle. is necessary. Therefore, in order to realize such a function, that is, in order to sufficiently obtain the benefit of using the on-vehicle radar device as a scanning radar device, the detection region is divided into a plurality of regions, and the spectrum is calculated for each division. It is necessary to perform an analysis and appropriately pair spectral peaks included in the upstream section spectrum and the downstream section spectrum calculated for each section.

The above-mentioned arithmetic processing can be performed by performing the above-described pairing processing on the spectrum analysis results calculated for all the sections. However, if such calculation processing is performed, the calculation load of the on-vehicle radar device becomes excessive, and disadvantages in cost or responsiveness occur. In this sense, the calculation method of the above-described conventional device is not always the optimum calculation method in the scanning radar device using the FM-CW radar device.

[0013] The present invention has been made in view of the above points, and pairs a spectrum peak included in an up-stream spectrum with a spectrum peak included in a down-stream spectrum using scan angle data. It is an object of the present invention to provide an FM-CW radar device that solves the above-mentioned problem by simply performing the above-described problem.

[0014]

The above object is achieved by the present invention.
A frequency modulation mechanism that modulates the frequency of the transmission wave at a predetermined rate of change, a beat signal generation mechanism that generates a beat signal based on the reflected wave and the transmission wave with respect to the transmission wave, and a beat signal that is included in the beat signal. A spectrum analysis mechanism for detecting the spectrum intensity of each frequency component, a spectrum analysis result of a beat signal obtained in a process of increasing the frequency of the transmission wave, and a beat obtained in a process of decreasing the frequency of the transmission wave. An FM- which detects a distance to an object reflecting the transmission wave and a relative velocity of the object by combining the result of the spectrum analysis with the signal.
In a CW radar, a scanning means for scanning a predetermined detection area with the transmission wave, and a scanning means in a scanning angle direction of the transmission wave.
At least one predetermined scanning area among a plurality of predetermined scanning areas
The spectrum obtained by the spectrum analysis mechanism
Multiple peak spectra are included in the vector analysis results
Under certain circumstances, a predetermined scan adjacent to the one predetermined scan area;
The peak included in the spectrum analysis result
In the case where the spectrum is single, the one predetermined scanning area
The peak spectrum included in the spectrum analysis result obtained in the process of increasing the frequency of the transmission wave for,
The peak spectrum included in the spectrum analysis result obtained in the process of lowering the frequency of the transmission wave, the adjacent
This is achieved by an FM-CW radar device provided with a spectrum pairing means for performing pairing based on a combination in a predetermined scanning region . In addition, the above purpose
2. The FM-CW radar according to claim 1, as described in claim 2.
In the apparatus, the spectrum pairing means further comprises:
The spectrum for at least one predetermined scanning area.
Peaks in the spectrum analysis results obtained by the
In a situation where a plurality of spectra are included, the one
For the predetermined scanning area adjacent to the predetermined scanning area,
The peak spectra included in the vector analysis results are already paired.
If the ring is ringed,
In the process of increasing the frequency of the transmitted wave.
A peak spectrum included in spectrum analysis result, the
Spectral solution obtained in the process of decreasing the frequency of the transmitted wave
And the peak spectrum included in the analysis result
Pair based on the combination in the predetermined scanning area
Achieved by the FM-CW radar device
You.

In the present invention, the transmission wave is irradiated in the scanning angle direction determined by the scanning means. When an object exists in the direction of irradiation of the transmission wave, a beat signal reflecting the distance to the object and the relative speed of the object is generated. When the beat signal obtained in the process of increasing the frequency of the transmission wave is subjected to frequency analysis, an upstream section spectrum is obtained. Further, when the beat signal obtained in the process of lowering the frequency of the transmission wave is subjected to frequency analysis, a down section spectrum is obtained. The spectrum peak included in the up-link section spectrum and the spectrum peak included in the down-link section spectrum reflect the distance to the object that caused the spectrum peak and the relative speed of the object. When multiple spectrum peaks are included in the up section spectrum and the down section spectrum, the distance to the object and the relative speed of the object can be detected for a plurality of objects by appropriately combining the spectrum peaks. Becomes possible. According to the first aspect of the present invention, the up section spectrum and the down section spectrum are calculated for each predetermined scanning area . The spectral pairing means includes a spectral peak for one predetermined scanning region.
In a situation where there are multiple
When there is a single spectral peak for the constant scanning area
In this case, the up-spectrum of the one predetermined scanning area
Spectrum peak in the spectrum
And the vector peak in the adjacent predetermined scanning area.
Pair based on the match. Spectral peak
If there is only one, the spectrum
And the spectrum peak of the downstream section spectrum are unique
Paired to. In this case, adjacent to this predetermined scanning area
Touches the specified scanning area where there are multiple spectral peaks.
As a result, overlapping spectral peaks are confirmed in both scanning regions.
And the number of remaining spectral peaks is reduced. this
For easy pairing of all spectral peaks
Become. Further, in the invention according to claim 2, the spectrum pairing means further performs scanning for one predetermined scanning region.
When there are multiple spectral peaks,
Spectral peaks for a given scan region adjacent to the region
If the pairing has already been performed,
For regions in the up section spectrum spectrum Rupiku
And the spectrum peak in the downstream section spectrum
Pair based on the combination in the adjacent predetermined scanning area
Ring. Also in this case, adjacent to the predetermined scanning area,
For a given scanning area with multiple spectral peaks
Determines the spectral peaks that overlap in both scan areas,
The number of remaining spectral peaks is reduced. For this reason,
Pairing of all spectral peaks is facilitated.

[0016]

FIG. 1 shows a system configuration diagram of a vehicle-mounted scanning radar apparatus according to an embodiment of the present invention. The apparatus of the present embodiment is controlled by a radar electronic control unit 10 (hereinafter, referred to as a radar ECU) and an environment-recognition vehicle speed control electronic control unit 12 (hereinafter, referred to as an environment-recognition ECU).

A radar antenna 14 and a scanning controller 16 are connected to the radar ECU 10. The radar antenna 14 is an FM-CW (Frequency Modulati
on-Continuous Wave) A component of the radar, which is arranged, for example, in the vicinity of a front grill of the vehicle so as to be rotatable around a vertically extending rotary shaft 14a. The radar antenna 14 is an antenna having directivity, and transmits and receives signals within a predetermined irradiation range.

A scanning mechanism 18 is connected to the radar antenna 14. The scanning mechanism 18 includes the radar antenna 14
Is controlled by the scanning controller 16 in a feedback manner. Scan controller 16
Is supplied with a scanning angle signal from the radar ECU 10. The scanning controller 16 includes the radar antenna 14
Scan angle of, to match the command angle theta _S from radar ECU 10, the scanning mechanism 18 performs feedback control. Radar ECU10 is predetermined detection area ahead of the vehicle, to be scanned at a predetermined speed by the radar antenna 14, increases or decreases the command angle theta _S scan angle in a predetermined cycle.

The radar ECU 10 includes the radar antenna 1
By subjecting the signal supplied from 4 to appropriate processing,
An object existing in a detection area in front of the vehicle is detected, and the detection result is supplied to the environment recognition ECU 12. Environmental awareness E
The alarm unit 20, the brake 22, and the throttle 24 are connected to the CU 12. The environment recognition ECU 12
When an object is in front of the vehicle, the alarm 20, the brake 22, or the throttle 24 is driven in accordance with a preset logic to draw the attention of the vehicle occupant and reduce the speed of the vehicle.

FIG. 2 is a block diagram showing the function of the radar ECU 10. As shown in FIG. The radar ECU 10 is a device mainly composed of a microcomputer. Functionally, the radar ECU 10 can be divided into a scanning angle control unit 26, a radar signal processing unit 28, and an object recognition unit 30, as shown in FIG. The scanning angle control unit 26 is a block that supplies a scanning angle signal to the above-described scanning controller 16. The scan angle command value θ _S included in the scan angle signal is changed in synchronization with the control timing of the radar signal processing unit 28.

The radar signal processor 28 constitutes an FM-CW radar together with the radar antenna 14. When an object exists in the scanning angle direction of the radar antenna 14, a signal related to the object is supplied to the radar signal processing unit 28. When such a signal is supplied, the radar signal processing unit 28 generates a spectrum analysis result reflecting the inter-vehicle distance and the relative speed between the subject and the own vehicle, and associates the result with the scan angle to associate the result with the scan angle. It is supplied to the recognition unit 30. The configuration of the radar signal processing unit 28 will be described later in detail with reference to FIG.

The object recognizing unit 30 includes a radar signal processing unit 2
Based on the spectrum analysis result supplied from 8, the data regarding the object is calculated for each scan, and based on the calculation result, the position of the object existing in the detection region set in front of the vehicle and the object are calculated. The distance and the relative speed of the object are calculated. The system according to the present embodiment includes the object recognizing unit 30.
Is characterized in that the spectrum analysis result supplied from the radar signal processing unit 28 is processed by a method described later.

FIG. 3 is a block diagram showing the function of the radar signal processing section 28 described above. The above-described radar antenna 14 includes a transmission antenna 14b as shown in FIG.
And functions as a receiving antenna 14c. The carrier generation circuit 32, the frequency modulation circuit 34, the modulation voltage generation circuit 36, and the directional coupler 3 included in the radar signal processing unit 28
Numeral 8 constitutes a transmitting circuit of the FM-CW radar.

The carrier generation circuit 32 generates a carrier having a predetermined frequency and supplies the carrier signal to the frequency modulation circuit 34. On the other hand, the modulation voltage generation circuit 36 generates a triangular wave whose amplitude changes in a triangular shape, and supplies the triangular wave to the frequency modulation circuit 34. The frequency modulation circuit 34 uses the triangular wave supplied from the modulation voltage generation circuit 36 as a modulation signal,
The carrier supplied from the carrier generation circuit 32 is frequency-modulated.

A waveform shown by a solid line in FIG. 4A shows a change state of the frequency of the signal appearing at the output terminal of the frequency modulation circuit 34. As a result of the above-described frequency modulation, the output terminal of the frequency modulation circuit 34 has a predetermined fluctuation width Δf and a modulation frequency fm (= 1 / T) with time, as shown by a solid line in FIG. T indicates a modulated wave signal modulated in a triangular wave shape with a fluctuation cycle of a triangular wave generated from the modulation voltage generating circuit 36). The modulated wave signal appearing at the output terminal of the frequency modulation circuit 34 is supplied to the transmission antenna 14b via the directional coupler 38 and to a mixer 40 described later.

As described above, the modulated wave signal supplied to the transmitting antenna 14b is transmitted in the scanning angle direction of the transmitting antenna 14b. When an object exists in such a scanning angle direction, the transmission signal is reflected by the object, and the reflected wave is received by the receiving antenna 14c. The mixer 40 is connected to the receiving antenna 14c. Radar signal processing unit 2
8 is a mixer 4 as a receiving circuit of the FM-CW radar.
0, an amplification circuit 42, a filter 44, and a fast Fourier transform processing circuit 46 (hereinafter, referred to as an FFT signal processing circuit). The signal received by the receiving antenna 14c is
The signal is processed by the receiving circuit and converted into data representing the inter-vehicle distance and the relative speed between the object and the vehicle.

In FIG. 4A, the waveforms indicated by broken lines and alternate long and short dash lines indicate how the frequency of the reflected signal supplied from the receiving antenna 14c to the mixer 40 changes. Mixer 4
At 0, the reflected signal and the transmission signal supplied from the directional coupler 38 are mixed to generate a beat signal having a frequency difference between the two as a variation frequency.

FIG. 4B shows how the frequency of the beat signal changes. Hereinafter, as shown in FIG. 4 (B), the frequency of the beat signal generated in the section where the frequency of the transmission signal rises is defined as an up frequency fup, and the frequency of the beat signal generated in the section where the frequency of the transmission signal falls is defined as Downward frequency f
Called down.

The beat signal generated by the mixer 40 is supplied to a filter 44 after being amplified by an amplifier circuit 42. The filter 44 separates the beat signal supplied from the amplifier circuit 42 into a beat signal in a rising section and a beat signal in a falling section. The separated beat signals are both FFT
The signal is supplied to the signal processing circuit 46. FFT signal processing circuit 4
6 performs an FFT process on the beat signal in each section,
A power spectrum for the uplink frequency fup (hereinafter, referred to as an uplink section spectrum) and a power spectrum for the downlink frequency fdown (hereinafter, referred to as a downlink section spectrum) are calculated.

FIG. 5A shows an upstream spectrum calculated by the FFT signal processing circuit 46 when two objects are present in the scanning angle direction of the radar antenna 14. FIG. 5 (B) shows a downlink section spectrum calculated by the FFT signal processing circuit 46 under the same environment.

When there are a plurality of objects in the scanning angle direction of the radar antenna 14, reflected waves of the respective objects are received by the receiving antenna 14c. In this case, the mixer 40 forms a beat signal for each of the plurality of received signals. As a result, the FFT signal processing circuit 4
At 6, a power spectrum having a plurality of peaks is detected.

Assuming that there is no relative speed between the vehicle and the object, there is a gap between the transmitted wave transmitted from the transmitting antenna 14b and the reflected wave reaching the receiving antenna 14c. A phase difference occurs according to the time required for the signal to propagate between the two. In this case, since the Doppler shift is not superimposed on the frequency of the reflected wave, the waveform representing the frequency variation of the reflected wave is simply a temporally parallel translation of the waveform of the transmission signal as shown by the dashed line in FIG. Waveform. Therefore, the up frequency fup and the down frequency fdo
wn both have the same value as indicated by the dashed line in FIG. 4B. At this time, both fup and fdown are values corresponding to the inter-vehicle distance between the target object and the vehicle.

On the other hand, the relative speed Vr between the vehicle and the object
Exists, a Doppler shift corresponding to the relative velocity Vr is superimposed on the frequency of the reflected wave. For this reason, for example, when the object and the vehicle tend to approach each other, the frequency of the reflected wave is shifted to a higher frequency side as a whole. As a result, as shown by the broken line in FIG. 4A, the waveform representing the frequency of the reflected wave is a waveform that has been translated in time in accordance with the distance (the waveform shown by the one-dot chain line in the figure) on the higher frequency side. The waveform is translated in parallel.

When the frequency of the reflected wave is shifted to the high frequency side as described above, fup is smaller and fdown is larger than when the relative velocity Vr is "0". At this time, if the average value of fup and fdown is calculated as shown in the following equation, the Doppler shift component superimposed on fup and the Doppler shift component superimposed on fdown cancel each other out, and the distance between the object and the vehicle becomes smaller. A characteristic value corresponding to the distance can be obtained.

Fr = (fup + fdown) / 2 (1) The deviation between fup and fdown corresponds to the sum of the Doppler shift component superimposed on fup and the Doppler shift component superimposed on fdown. Therefore, as shown in the following equation, when a value of 偏差 of the difference between the two is obtained, the value becomes a characteristic value corresponding to the Doppler shift component caused by the relative speed between the vehicle and the object.

Fd = (fdown−fup) / 2 (2) In this embodiment, the center frequency of the modulated wave signal generated by the frequency modulation circuit 34 is f ₀ , the modulation frequency is fm, the modulation width is Δf, In addition, when the propagation speed of the transmission signal is high speed c and there is an object having a relative speed Vr at a position separated by the distance L, the following equation is established.

Fr = 4fm · Δf · L / c (3) fd = 2Vr · f ₀ / c (4) Therefore, in the FFT signal processing circuit 46, the spectrum peak representing the up frequency fup and the down spectrum When a spectrum peak representing the frequency fdown is obtained, these are substituted into the above equations (1) and (2) to obtain fr and fd, and the calculated values are further expressed by the above equations (3) and (4). By substituting into the formula, the inter-vehicle distance L and the relative speed Vr of the target existing in the scanning angle direction of the radar antenna 14 can be obtained.

As described above, FIGS. 5A and 5B
Is a spectrum analysis result when two objects are present in the scanning angle direction of the radar antenna 14. More specifically, the spectrum appearing at the frequency FM _U1 in FIG. 5A and the spectrum appearing at the frequency FM _d1 in FIG. 5B are caused by one object existing in the scanning angle direction. This is the peak that appears. FIG.
The spectrum appearing at the frequency FM _U2 in FIG. 5A and the spectrum appearing at the frequency FM _d2 in FIG. 5B are peaks appearing due to other objects existing in the scanning angle direction.

The results of spectrum analysis as shown in FIG.
FM_U1And FM_d1Combined with above
By performing calculations using equations (1) to (4), one
The distance L and the relative speed Vr of the target object can be obtained.
And FM_U2And FM _d2Combine with
By performing the above calculations, the distance between other vehicles
The separation L and the relative speed Vr can be obtained. like this
In addition, in the system of this embodiment, a set of spectrum
Obtaining data on multiple objects from analysis results
Can be.

As described above, the radar antenna 14 is scanned by the scanning mechanism 18. FIG. 6 shows an area set as a scanning area of the radar antenna 14 in the vehicle 48 on which the system of the present embodiment is mounted. As shown in FIG. 6, in the present embodiment, a region having a spread of 10 ° to the left and right with respect to the longitudinal axis of the vehicle 48 is a region scanned by the radar antenna 14, that is, a target object detection region. Have been. In the following description, a region on the left side of the axis of the vehicle 48 is defined as a region having a negative scanning angle θ _S , and a region on the right side of the axis of the vehicle 48 is defined as a region having a positive scanning angle θ _S.

FIG. 7 shows the scanning angle θ _{S of the} radar antenna 14.
And the frequency f of the transmission signal. As mentioned above,
In the system of the present embodiment, the radar signal processing unit 28
The scanning angle θ _S of the radar antenna 14 is controlled in synchronization with the above processing. More specifically, the radar antenna 14 is controlled such that the scanning angle θ _S changes by 0.5 ° while the frequency f of the transmission signal changes by one period as shown in FIG.
In the present embodiment, the radar antenna 14 has approximately 1
Control is performed so that an area of −10 ° to + 10 ° is scanned every 00 msec.

According to the system of the present embodiment, data relating to an object can be calculated by detecting one set of an up section spectrum and a down section spectrum. As described above, if the scan angle θ _S changes by 0.5 ° while the frequency f of the transmission signal changes by one cycle, a set of upstream section spectrums is generated every time the scan angle θ _S changes by 0.5 °. And the downstream spectrum can be obtained. Therefore,
According to the system of this embodiment, every time the radar antenna 14 is scanned by 0.5 °, data on the target object can be calculated.

That is, in the system of this embodiment,
The detection area in front of the vehicle 48 is divided into 40 detection areas at intervals of 0.5 °, and the radar antenna 14 has a scanning angle θ _S −
During the scanning of the region from 10 ° to + 10 °, that is, during about 100 msec, 40 sets of the spectrum analysis results shown in FIGS. 5A and 5B can be obtained. The radar signal processing unit 28 supplies the 40 sets of spectrum analysis results to the object recognizing unit 30 in a state where the results are associated with the scanning angle θ _S of the radar sensor 20 as the radar antenna 14 is scanned. I do.

FIG. 8 shows a state in which objects 50 and 52 are present in front of a vehicle equipped with the system of this embodiment. The object 50 is a fixed object such as a guardrail pole, and the object 52 is a preceding vehicle running on a road.
As described above, in the system of the present embodiment, a set of spectral analysis results is obtained every time the radar antenna 14 is scanned by 0.5 °. Further, the radar antenna 14 transmits and receives transmission and reception waves with a predetermined spread. For this reason, the detection area secured by scanning the radar antenna 14 by 0.5 ° is within a range of 0.5 °.
4 is a range in which the spread of the transmitted and received waves is added. The boundary line shown by a solid line in FIG. 8 indicates a boundary line (hereinafter, referred to as a region division line) that divides the detection region every 0.5 °. The boundary line shown by the broken line in FIG.
4 shows the spread range of the transmission / reception waves of the radar antenna 14 when the scanning direction of FIG.

When the scanning direction of the radar antenna 14 changes from a state in which it overlaps the area dividing line shown on the leftmost side in FIG. 8 to a state in which it overlaps an area dividing line adjacent to the right side of the area dividing line, FIG. The range indicated by the inside is scanned. Similarly, thereafter, every time the scanning direction of the radar antenna 14 changes by 0.5 °, the area indicated by the area shown in FIG. These regions to have portions that overlap with adjacent regions. Therefore, the object located near the boundary of each region is
It will be detected as an object in two areas.

In the situation shown in FIG. 8, the object 50 is
It exists in the overlapping area of the area and the area. The target object 52 exists in an overlapping area between the areas. Therefore, the object 50 is detected in the region and the region, and the object 52 is detected in the region and the region.

FIGS. 9A and 9B show an up section spectrum and a down section spectrum, respectively, with respect to a region. In these spectrum analysis results, peak spectra Su ₅₀ and Sd ₅₀ resulting from the target object 50 appear. Since the object 50 is an object fixed on the road, the vehicle equipped with the system of the present embodiment and the object 50
There is a large relative velocity between. Therefore, the position where the peak spectrum Su ₅₀ appears in the up section spectrum and the peak spectrum Sd ₅₀ in the down section spectrum.
Is relatively separated from the position where appears.

FIGS. 10A and 10B show an up-spectrum spectrum and a down-segment spectrum for a region, respectively. Among these spectral analysis results, peak spectra Su ₅₀ and S due to the target object 50 are included.
peak spectrum S due to the object 52 in addition to d ₅₀
u ₅₂ and Sd ₅₂ appear. Since the object 52 is traveling on the road, there is no relatively large relative speed between the vehicle equipped with the system of the present embodiment and the object 52. Therefore, the peak spectrum Su is included in the upstream section spectrum.
_The position where ₅₂ appears and the position where the peak spectrum Sd ₅₂ appears in the downstream section spectrum are relatively close to each other.

FIGS. 11 (A) and 11 (B) show an up section spectrum and a down section spectrum, respectively, for a region. Among these spectral analysis results, peak spectra Su ₅₀ and S due to the target object 52 are included.
only d ₅₀ appears. 12A and FIG.
(B) represents an up section spectrum and a down section spectrum for the region, respectively. Since no object is present in the region, no peak spectrum appears in these spectral analysis results.

As shown in FIGS. 9 (A) and 9 (B) or FIGS. 11 (A) and 11 (B),
When one peak spectrum appears in each of the ascending section spectrum and the descending section spectrum, those spectrum peaks are simply combined to obtain the above (1).
By performing the calculation based on the expressions (4) to (4), data on the target object can be accurately obtained.

However, as shown in FIGS. 10 (A) and 10 (B), when a plurality of spectrum peaks are present in each of the up section spectrum and the down section spectrum, pairing of the spectrum peaks may be performed. is necessary. When a plurality of objects detected at the same time have a large relative velocity difference as in the above-described objects 50 and 52, the order in which peak spectra caused by those objects appear in the up-segment spectrum and the down-segment spectrum The order in which they appear may be reversed.
Therefore, an accurate combination may not be obtained simply by pairing a plurality of peak spectra in order of frequency.

In the present embodiment, when a plurality of peak spectra are detected in a specific scanning region, the pairing of peak spectra is performed in consideration of the element of the scanning angle θ _S , thereby facilitating such pairing. It is characterized in that it can be performed accurately. Hereinafter, a pairing method performed in the present embodiment will be described with reference to FIGS.

FIGS. 13 and 14 show a flowchart of an example of a control routine executed by the radar ECU 10 in order to realize the above functions. The routine shown in FIGS. 13 and 14 is a routine that is started about every 100 msec each time scanning of the radar antenna 14 is started.

When the routine shown in FIGS. 13 and 14 is started, first, at step 100, the counter i is incremented. Counter i is radar antenna 1
4 is a counter representing the number of the area scanned by
“0” is set by the initial processing. Therefore, immediately after this routine is started, i is set to “1” in step 100.

In step 102, it is determined whether the data input for the area i has been completed, that is, whether the scanning of the area i has been completed. If it is determined that the data input has not been completed yet, the determination in step 102 is repeatedly performed until it is determined that the data input has been completed. If it is determined that the data input is completed, step 1
At 04, signal processing for obtaining an uplink section spectrum and a downlink section spectrum is performed.

When the processing of step 104 is completed,
Next, in step 106, it is determined whether or not the number of peak spectra included in the spectrum analysis result is larger than "1". The number of peaks is not greater than "1",
That is, when it is determined that the number of peaks is “1”, accurate pairing can be obtained by simply combining the peak spectrum included in the upstream section spectrum and the peak spectrum included in the downstream section spectrum. . Therefore, if the above determination is made,
Steps 108 and 110 are jumped, and the process of step 112 is executed.

If it is determined in step 106 that the number of peaks is greater than "1", step 108
In, the peak spectrum included in the uplink section spectrum and the peak spectrum included in the downlink section spectrum are paired in order of frequency. Next, step 1
At 10, it is determined whether or not the degree of correlation of the paired peak spectrum is equal to or greater than a predetermined threshold value α _TH . The degree of correlation of the peak spectrum is calculated based on the shape of the peak spectrum and the like. If the paired peak spectra are both due to the same object, a high degree of correlation is obtained. In this case, the above step 1
Condition 10 is satisfied. On the other hand, when the paired peak spectra are due to different objects, a low degree of correlation is calculated. In this case, the condition of step 110 is not satisfied.

If it is determined that the condition in step 110 is satisfied, it is determined that a plurality of peak spectra have been properly paired. Next, in step 112, the peak spectrum related to the object is determined based on the paired peak spectra. Data, that is, the inter-vehicle distance L between the target and the host vehicle, and the relative speed Vr of the target with respect to the host vehicle
Are calculated, and the calculated values are stored together with the number i of the scanning area.

On the other hand, if it is determined that the condition in step 110 is not satisfied, it is determined that a plurality of peak spectra are not properly paired, and in step 114, the spectrum information is held. .
In this embodiment, the number i of the scanning area, the level of the peak spectrum, and the position (frequency) at which the peak spectrum is detected are held as spectrum information.

When the above processing is completed, the process proceeds to step 1
At 16, it is determined whether or not the counter i has reached a predetermined value n. The predetermined value n is a number assigned to the final scanning area. If i ≧ n is not satisfied, it is determined that data collection for all scan areas has not been completed yet. In this case, the processes of steps 100 to 114 are repeatedly performed until it is determined that the condition of i ≧ n is satisfied. On the other hand, if it is determined that i ≧ n is satisfied, it is determined that the data collection for all the scanning regions has been completed. In this case, after the counter i is reset to “0” in step 118, the processing from step 120 shown in FIG. 14 is performed.

In step 120, the above step 114
In the region where the spectrum information is held, that is, the region in which the combination of the peak spectra is not determined (hereinafter, referred to as an uncertain region), the number of one region is substituted for the variable j. The one area is determined to be, for example, the area with the smallest number or the area with the largest number among the uncertain areas, or the area corresponding to the front of the vehicle.

In step 122, the variable k is set to "j-1".
Is substituted. Next, in step 124, it is determined whether or not the combination of the peak spectra of the region k has been determined. If the region k is also an uncertain region, it is determined that the above condition is not satisfied. In this case, thereafter, in step 126, it is determined whether or not k is smaller than j, and the processing of step 128 or step 130 is executed according to the determination result. As described above, the variable k is initially set to j-1. If k is j-1, the condition of step 126 is satisfied. In this case, after the value of k is decremented in step 128, the process of step 124 is executed again. In this case, the region k
Until is determined to be a fixed area, the determination of whether or not a smaller numbered area is a fixed area is sequentially performed. Also, as described later, the variable k is j + 1 under a specific situation.
May be set to In such a case, it is determined that the condition of step 126 is not satisfied, and step 13
After k is incremented by 0, step 124 is executed.
Is executed again. In this case, until an area k is determined to be a determined area, determination of whether or not an area having a higher number is a determined area is sequentially performed.

If it is determined in step 124 that the region k is a definite region, then in step 132, the k region, that is, the peak spectrum included in the definite region exists in the undetermined region adjacent to the k region. Is determined. If there is an overlapping peak spectrum (hereinafter, referred to as an overlapping peak), a peak spectrum in an uncertain region can be easily and accurately paired based on a combination of already determined peak spectra. On the other hand, if there is no overlap between them, pair rig cannot be performed by such a method. In this case, in step 134, j + 1 is substituted for the variable k.
A search for a fixed area having a number larger than that of the area j is started.

If it is determined in step 132 that there is an overlapping peak in the uncertain region, a process of pairing the overlapping peak in the spectrum analysis result of the uncertain region is performed in step 136. When the overlapping peaks are paired, the number of peaks remaining in the spectrum analysis result of the uncertain region decreases, and the pairing becomes easy. Thereafter, in step 138, the peak spectrum remaining in the spectrum analysis result of the uncertain region is paired by the frequency pairing method and the correlation pairing method.

When the above processing is completed, it is next determined in step 140 whether or not the peak spectra have been determined for all the regions. As a result, if it is determined that there is still an uncertain area,
The processes after 20 are executed again. On the other hand, if it is determined that the peak spectra of all the regions have already been determined, the current routine ends.

According to the above-described processing, when an appropriate combination of peak spectra cannot be obtained by the frequency pairing technique, an uncertain region is determined based on the result of spectrum analysis of another region adjacent to the region. A part of the peak spectrum included in the spectrum analysis result can be accurately paired. When the number of uncertain peaks included in the uncertain region decreases due to such pairing,
Compared to the case where all peak spectra are uncertain peaks, the remaining peak spectra can be easily paired. Therefore, according to the system of the present embodiment, it is possible to easily and surely pair a large number of peak spectra included in a plurality of spectrum analysis results. In this regard, the system according to the present embodiment has an effect that a function of accurately detecting an object in a wide detection area can be realized without disadvantages in cost and responsiveness.

In the above embodiment, the radar E
In the radar signal processing unit 28 of the CU 10, the carrier generation circuit 32, the frequency modulation circuit 34, and the modulation voltage generation circuit 36
Is the frequency modulation mechanism described above, the mixer 40 and the amplifier circuit 42 are the beat signal generation mechanism described above, the filter 44 and the FFT signal processing circuit 46 are the spectrum analysis mechanism described above, the scanning controller 16, the scanning mechanism 18 and the radar The scanning angle control unit 26 of the ECU 10 corresponds to each of the above-described scanning units. Further, in the above-described embodiment, the radar ECU 10 performs the processing in steps 120 to 136 described above.
By executing the above processing, the above-described spectrum pairing means is realized.

[0068]

As described above, according to the present invention, the up section spectrum and the down section spectrum are calculated for each scanning angle, and data on the object is obtained for each scanning angle.
Therefore, it is possible to accurately detect the positions of a plurality of objects existing in a detection area wider than the irradiation range of the transmission wave. Further, according to the present invention, when pairing spectral peaks, scanning angle data is used. For this reason,
Compared to the case where the scan angle data is not used, the spectral peaks can be easily paired.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an FM-CW radar apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of a radar ECU used in the FM-CW radar device shown in FIG.

FIG. 3 is a block diagram of a radar signal processing unit which is a component of the radar ECU shown in FIG. 2;

FIG. 4A is a waveform showing a change in the frequency of a signal transmitted and received by a radar antenna. FIG. 4B is a waveform of a beat signal detected by the radar ECU.

FIG. 5A shows spectrum data representing an uplink frequency. FIG. 5B shows spectrum data representing a downlink frequency.

6 is a diagram showing a detection range of the FM-CW radar device shown in FIG.

7 is a waveform showing a relationship between a scanning angle of the FM-CW radar device shown in FIG. 1 and a frequency of a transmission wave.

8 is a diagram showing an object existing in front of the vehicle and the FM shown in FIG. 1;
It is a figure showing the scanning area of -CW radar device.

FIG. 9A is an example of an uplink section spectrum obtained for the region shown in FIG. 8; FIG. 9B is an example of a downlink section spectrum obtained for the region shown in FIG.

FIG. 10A is an example of an up section spectrum obtained for the area shown in FIG. 8; FIG.
(B) is an example of a downlink section spectrum obtained for the region shown in FIG. 8.

FIG. 11A is an example of an uplink section spectrum obtained for the area shown in FIG. 8; FIG.
(B) is an example of a downlink section spectrum obtained for the region shown in FIG. 8.

FIG. 12A is an example of an uplink section spectrum obtained for the region shown in FIG. 8; FIG.
(B) is an example of a downlink section spectrum obtained for the region shown in FIG. 8.

13 is a flowchart (part 1) of an example of a control routine executed in a radar ECU provided in the FM-CW radar device shown in FIG. 1;

FIG. 14 is a flowchart (part 2) of one example of a control routine executed by the radar ECU provided in the FM-CW radar device shown in FIG. 1;

[Explanation of symbols]

Reference Signs List 10 radar electronic control unit (radar ECU) 12 environment recognition vehicle speed control electronic control unit (environment recognition vehicle speed control ECU) 14 radar antenna 16 scan controller 18 scanning mechanism 26 scan angle control unit 28 radar signal processing unit 30 object recognition unit 48 Vehicle 50,52 Object

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-5252 (JP, A) JP-A-6-242230 (JP, A) JP-A-5-142337 (JP, A) JP-A-7-152 318635 (JP, A) JP-A-8-75848 (JP, A) JP-A-8-211144 (JP, A) JP-A-9-145833 (JP, A) (58) Fields investigated (Int. Cl. G01S ^7/ 00-7/42 G01S 13/00-13/96

Claims (2)

(57) [Claims] 1. A frequency modulation mechanism for modulating a frequency of a transmission wave at a predetermined rate of change, a beat signal generation mechanism for generating a beat signal based on a reflected wave and a transmission wave with respect to the transmission wave, and a beat signal included in the beat signal. A spectrum analysis mechanism for detecting the spectrum intensity of each frequency component, a spectrum analysis result of a beat signal obtained in a process of increasing the frequency of the transmission wave, and a beat obtained in a process of decreasing the frequency of the transmission wave. An FM- which detects a distance to an object reflecting the transmission wave and a relative velocity of the object by combining the result of the spectrum analysis with the signal.
In the CW radar, scanning means for causing the transmission wave to scan a predetermined detection area, and a plurality of predetermined scanning areas in a scanning angle direction of the transmission wave.
The spectrum for at least one predetermined scanning area.
Peaks in the spectrum analysis results obtained by the
In a situation where a plurality of spectra are included, the one
For the predetermined scanning area adjacent to the predetermined scanning area,
The single peak spectrum included in the
The peak spectrum included in the spectrum analysis result obtained in the process of increasing the frequency of the transmission wave for the one predetermined scanning region, and the peak spectrum included in the spectrum analysis result obtained in the process of decreasing the frequency of the transmission wave. And a peak spectrum to be set in the adjacent predetermined scanning area.
An FM-CW radar device, comprising: spectrum pairing means for performing pairing based on matching . 2. The FM-CW radar device according to claim 1,
Oite, the spectral pairing means further comprises at least one
By the spectrum analysis mechanism for the predetermined scanning area of
Multiple peak spectra in the obtained spectrum analysis results
In the included situation, it is adjacent to the one predetermined scanning area.
For the predetermined scanning area that touches,
The included peak spectrum is already paired
In the case, the transmission wave for the one predetermined scanning area
Analysis results obtained in the process of increasing the frequency of
And the frequency of the transmission wave is
Included in the spectrum analysis results obtained during the descending process
And the peak spectrum in the adjacent predetermined scanning area.
It is characterized by pairing based on the combination
FM-CW radar device.