JP2002311131A - Vehicle object detection device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To accurately detect a peak signal due to an object and a peak signal due to noise to enhance the detection capability of an object detection device. SOLUTION: An object detection apparatus for a vehicle using an FM-CW wave, a mixer 7 mixes a transmission wave and a reception wave to generate a beat signal, and the beat signal is subjected to frequency analysis by a frequency analysis means 13. Among the peak signals obtained by the above, the peak signal equal to or more than the threshold is determined as the detection peak of the object by the detection peak determination means 14, and the peak signal frequency prediction means 16 determines the future based on the detection information of the previously detected object. In the prediction area including the predicted peak signal frequency.
Reduces the threshold value, and the detected peak determining unit 14 determines that the peak signal equal to or greater than the changed threshold value is the detected peak of the object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detection device for a vehicle for detecting an object such as a preceding vehicle by a radar device using an FM-CW wave (frequency modulated continuous wave).

[0002]

2. Description of the Related Art Such an object detecting device for a vehicle is known, for example, from Japanese Patent Application Laid-Open No. 11-38129.

As shown in FIG. 5, in the conventional object detection device using an FM-CW wave, the oscillation operation of an oscillator 3 is controlled by an FM modulation control circuit 2 based on a timing signal input from a timing signal generation circuit 1. Modulation controlled, FIG.
As shown by the solid line in (a), a transmission wave whose frequency is modulated in a triangular waveform is transmitted from the transmission / reception antenna 6 via the amplifier 4 and the circulator 5. When the FM-CW wave is reflected by an object such as a preceding vehicle and the reflected wave is received by the transmitting and receiving antenna 6, the received wave is, for example, when the object approaches the own vehicle, as shown in FIG. ), As shown by the broken line, on the rising side where the frequency of the transmission wave increases linearly, it appears later than the transmission wave at a lower frequency than the transmission wave, and on the falling side where the frequency of the transmission wave decreases linearly. Appears later than the transmitted wave at a higher frequency than the transmitted wave.

The received wave received by the transmitting / receiving antenna 6 is input to the mixer 7 via the circulator 5. The mixer 7 includes the oscillator 3 in addition to the reception wave from the circulator 5.
The scanning wave distributed from the transmission wave output from the
As shown in FIG. 6B, the transmission wave and the reception wave are mixed by the mixer 7,
A beat signal having a peak frequency Fup on the rising side where the frequency of the transmission wave increases linearly and a peak signal Fdn on the falling side where the frequency of the transmission wave decreases linearly is generated.

[0005] The beat signal obtained by the mixer 7 is
Is amplified to a required level by the A / D converter 1
The amplified data that has been A / D-converted and digitized by 0 at each sampling time is stored and held in the memory 11 in time series. The memory 11 receives a timing signal from the timing signal generation circuit 1. In response to the timing signal, the memory 11 stores data on each of the rising side where the frequency of the transmission / reception wave increases and the falling side where the frequency decreases. Will be stored.

The data stored in the memory 11 is input to a CPU 12 having a frequency analysis means 13, a detection peak determination means 14, and an object detection means 15, and the CPU 12
At 12, the arithmetic processing based on the input data is executed.

The frequency analyzing means 13 analyzes the frequency of the beat signal data stored in the memory 11 to obtain a spectrum distribution.
FFT (Fast Fourier Transform) is used.

The detection peak judging means 14 detects a spectrum (peak signal) having a detection level equal to or higher than a predetermined threshold and having a maximum value, based on the spectrum data obtained by the frequency analysis by the frequency analyzing means 13. The peak signal on the rising side shown in FIG. 7A and the peak signal on the falling side shown in FIG. 7B are detected symmetrically with respect to the peak position when the relative speed with respect to the object is “0”. Is done.

The object detecting means 15 calculates the relative distance and relative speed of the object based on the rising peak frequency Fup and the falling peak frequency Fdn obtained by the detected peak judging means 14. Specifically, the distance to the object is calculated based on the sum of the two peak frequencies Fup and Fdn, and the relative speed with the object is calculated based on the difference between the two peak frequencies Fup and Fdn.

[0010]

The detection level detected by the object detection device decreases as the distance between the vehicle and the object increases (see FIG. 2). FIG.
(A) shows the spectrum data at the time T. An object moving away from the own vehicle has a peak signal Pa1 equal to or larger than a threshold value indicated by a dashed line, and two other peak signals Pc1 caused by noise. , Pc2 are smaller than the threshold value. FIG. 3C shows the spectrum data at time T + 1. Since the peak signal Pa1 of the object drops below the threshold value indicated by the dashed line due to the increase in the distance to the object, the object is detected at that time. There is a problem that can not be done. If the threshold is lowered to a level at which an object can be detected in order to solve such a problem, a new problem arises in that the object can be detected, but the other two peak signals Pc1 and Pc2 caused by noise are erroneously recognized as the object. Resulting in.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to accurately identify a peak signal due to an object and a peak signal due to noise to enhance the detection capability of an object detection device.

[0012]

In order to achieve the above object, according to the first aspect of the present invention, an FM-CW wave is transmitted and a reflected wave of the FM-CW wave from an object is received. Transmitting and receiving means, a mixer for mixing a transmitted wave and a received wave to generate a beat signal, a frequency analyzing means for frequency-analyzing the beat signal obtained by the mixer, and an ascending and descending frequency analysis by the frequency analyzing means Among the peak signals obtained based on the result, a detection peak determination unit that determines a peak signal equal to or greater than a threshold value as a detection peak, and an object based on the ascending and descending detection peaks obtained by the detection peak determination unit. An object detection device that calculates at least one of a distance and a relative speed with respect to an object. A peak signal frequency estimating means for estimating a frequency, and a threshold value changing means for changing the threshold value, wherein the detected peak judging means includes a threshold value changing means in a prediction area including the peak signal frequency predicted by the peak signal frequency estimating means. A vehicle object detection device is characterized in that a peak signal that is equal to or greater than the threshold value changed by the above is determined as a detection peak.

[0013] According to the above configuration, a future peak signal frequency is predicted from the detection information of the object detected in the past, and in the prediction area including the peak signal frequency, the peak signal that is equal to or greater than the threshold value changed by the threshold value changing means is detected. Is determined as the object detection peak, so it is necessary to reliably determine whether the newly detected peak signal is from an object detected in the past or due to noise, and enhance the detection capability of the object detection device. Can be.

According to the second aspect of the present invention,
In addition to the configuration of claim 1, the apparatus further includes a first measurement unit that measures a time during which the object is detected by the object detection unit, and the detection time of the object measured by the first measurement unit increases as the detection time increases. An object detection device for a vehicle, wherein the threshold value is reduced, is proposed.

According to the above arrangement, the threshold value is lowered as the detection time of the object measured by the first measuring means is prolonged. Can be reliably detected.

According to the third aspect of the present invention,
In addition to the configuration of claim 2, an object detection device for a vehicle is proposed in which the prediction area is widened as the detection time of the object measured by the first measurement unit increases.

According to the above configuration, the prediction area is widened as the detection time of the object measured by the first measuring means becomes longer. Therefore, when the peak signal is highly likely to be that of the object, the prediction area is increased. Omission of detection of an object can be reliably prevented.

According to the invention described in claim 4,
In addition to the configuration according to any one of claims 1 to 3, further comprising a second measurement unit that measures the existence time of an arbitrary peak signal obtained based on a frequency analysis result by the frequency analysis unit, and determines a detected peak. The means for detecting an object of a vehicle is characterized in that when the existence time of a peak signal in the prediction area measured by the second measurement means is equal to or more than a predetermined value, the peak signal is determined as a detection peak. Suggested.

According to the above configuration, the existence time of the peak signal in the prediction area is measured by the second measuring means, and when the existence time of the peak signal is equal to or more than the predetermined value, it is determined that the detected peak is detected. In addition, the effect of noise can be effectively eliminated to increase the reliability of the detected peak.

According to the invention described in claim 5,
In addition to the configuration according to any one of claims 1 to 4, further comprising an adding means for adding the frequency analysis result by the frequency analyzing means a plurality of times, wherein the detected peak determining means is a frequency analysis result obtained by the adding means. An object detection device for a vehicle, characterized in that a detection peak is determined by using the method.

According to the above configuration, the detection peak is determined using the value obtained by adding the frequency analysis results a plurality of times, so that the influence of one-shot noise is reliably eliminated and the reliability of the detection peak is reduced. Can be further increased.

The transmitting / receiving antenna 6 corresponds to the transmitting / receiving means of the present invention.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

1 to 4 show an embodiment of the present invention. FIG. 1 is an overall configuration diagram of an object detection device, FIG. 2 is a graph showing a relationship between a distance between a vehicle and an object and a detection level, FIG. 3 is a time chart showing a change in the detection level with the passage of time, and FIG. 4 is a flowchart for explaining the operation.

FIG. 1 shows a CPU of the object detecting apparatus according to the present embodiment.
Twelve circuit configurations are shown. The configuration other than the CPU 12 is as follows.
It is the same as that of FIG. Conventional CPU described in FIG.
12 is a frequency analysis means 13 and a detection peak determination means 1
4 and the object detection means 15,
The CPU 12 of the embodiment further includes a peak signal frequency prediction unit 1.
6 and a threshold changing unit 20. The peak signal frequency prediction means 16 predicts the relative distance and relative speed of the object in the future (time t + 1) from the relative distance and relative speed of the object at the current time (time t). The threshold changing unit 20 changes a threshold in a prediction area described later.

The first measuring means 17 in FIG. 1 is used in a second embodiment and a third embodiment which will be described later, and the second measuring means 18 is used in a fourth embodiment which will be described later. Is used in a fifth embodiment described later.

In the following, the first embodiment of the present invention will be described. As shown in FIG.
a1 and two other peak signals Pc1 and Pc2 caused by noise are smaller than the threshold value.
As shown in FIG. 3B, based on the following distance and relative speed of the preceding vehicle detected based on the peak signal Pa1,
The peak signal frequency prediction means 16 calculates the predicted frequency of the peak signal Pa1 at the time t + 1, and a prediction area is set near the predicted frequency.

When the prediction area is set in this way, the threshold value changing means 20 changes the threshold value inside the prediction area so as to be lower than the threshold value outside the prediction area. As described with reference to FIG. 2, the detection level detected by the radar device decreases as the inter-vehicle distance from the preceding vehicle increases, and therefore, as shown in FIG. Even if the signal Pa1 falls below the threshold value before the change, if the peak signal Pa1 exists in the prediction area, the peak signal Pa is changed to a low threshold value in the prediction area.
1 exceeds the threshold value after the change, the peak signal Pa1
Can be determined to be that of the preceding vehicle.

At this time, since the threshold value outside the prediction area is not changed, the other two peak signals Pc caused by noise are not changed.
Even if 1, Pc2 exists, its magnitude is less than the threshold value, and it can be determined that noise is caused even at time t + 1.

As described above, the threshold value is changed to be low in the prediction area predicted by the peak signal frequency prediction means 16, so that even if the peak signal Pa1 existing there becomes small, it exceeds the changed threshold value. Since the two peak signals Pc1 and Pc2 caused by noise outside the prediction area can be determined to be that of the preceding vehicle, there is no possibility that the two peak signals Pc1 and Pc2 are erroneously determined to be that of the preceding vehicle. Accuracy can be effectively increased.

Next, the above operation will be further described with reference to the flowchart of FIG.

First, the beat signal is sampled in step S1, the beat signal is subjected to FFT processing in step S2 to obtain spectrum data, and in step S3, the peak signal Pn is extracted from the detected spectrum. If the level of the peak signal Pn is equal to or higher than the threshold value in step S4, the peak signal Pn is set as the detection peak Pna of the object in step S5, and the relative speed and relative distance of the object are calculated from the detection peak Pna in step S6. S7
Calculates the next predicted position peak signal Pnb from the relative speed and relative distance of the object.

On the other hand, if the level of the peak signal Pn is less than the threshold value in step S4, the predicted position peak signal P calculated from the previous detected peak Pna is determined in step S8.
Focusing on nb, a prediction area is set near the prediction position peak signal Pnb, and the threshold value in the prediction area is reduced. If the current peak signal Pn is present in the prediction area in the subsequent step S9, and if the level of the peak signal Pn is equal to or more than the changed threshold in step S10, the process proceeds to step S5 and the current peak signal Pn is set to the object. The detection peak is set to Pna. If the current peak signal Pn does not exist in the prediction area near the predicted position peak signal Pnb in the step S9, or
If the level of the peak signal Pn is less than the changed threshold value at 10, the current peak signal Pn is not set as the object detection peak Pna at step S11.

Next, a second embodiment of the present invention will be described.

The second embodiment uses the peak signal frequency predicting means 16, the threshold value changing means 20, and the first measuring means 17 in FIG. In the second embodiment, the time T during which the preceding vehicle has been continuously detected by the object detecting means 15 is measured by the first measuring means 17, and when the time T is long, the reliability of the detection data of the preceding vehicle is low. Because it ’s expensive,
The threshold changing means 20 reduces the threshold according to the length of the time T, thereby preventing omission of detection and making it possible to detect the preceding vehicle more reliably. Specifically, when the time during which the preceding vehicle has been continuously detected is T, the threshold Th is reduced to Th ← Th−a * T with a being a constant. Therefore, the threshold value Th decreases linearly as the time T increases.

Next, a third embodiment of the present invention will be described.

The third embodiment uses the peak signal frequency predicting means 16, the threshold value changing means 20, and the first measuring means 17 in FIG. In the present embodiment, in addition to decreasing the threshold value according to the time T during which the preceding vehicle has been continuously detected, the width of the prediction area predicted by the peak signal frequency prediction means 16 according to the time T is increased. Let it.
In general, increasing the width of the prediction area increases the possibility of erroneous detection. However, when the time T during which the preceding vehicle has been continuously detected is long, the reliability of the detection data of the preceding vehicle is high. Even if the width of the area is increased, the possibility of erroneous detection does not increase, and detection omission of the preceding vehicle can be effectively prevented.

Next, a fourth embodiment of the present invention will be described.

The fourth embodiment uses the peak signal frequency predicting means 16, the threshold value changing means 20, and the second measuring means 18 in FIG. When the peak signal is detected due to sporadic disturbance such as noise, the possibility that the peak signal is continuously generated at the same place is reduced. Then, the existence time of an arbitrary peak signal is measured by the second measuring means 18 to determine whether the signal is a peak signal due to a preceding vehicle or a peak signal due to noise, and the peak signal in the prediction area is continuously measured over a predetermined time. Only when the detection is made, the peak signal is used as the detection peak, so that erroneous detection due to noise can be reliably eliminated, and the reliability of the detection peak can be improved.

Next, a fifth embodiment of the present invention will be described.

In the fifth embodiment, the peak signal frequency estimating means 16, the threshold value changing means 20, and the adding means 1 shown in FIG.
9 is used. In the present embodiment, by adding (integrating) the results of the frequency analysis in the prediction area up to the number analyzed in the past a plurality of times, the peak signal by the preceding vehicle which is continuously detected is sporadically generated. It is possible to more reliably determine the peak signal due to the generated noise and to prevent erroneous detection due to the noise.

Although the embodiments of the present invention have been described above, various design changes can be made in the present invention without departing from the gist thereof.

[0043]

As described above, according to the first aspect of the present invention, a future peak signal frequency is predicted from detection information of an object detected in the past, and in a prediction area including this peak signal frequency, Since the peak signal that is equal to or greater than the threshold value changed by the threshold value changing unit is determined as the detected peak of the object, it is ensured that the newly detected peak signal of this time is that of the previously detected object or that it is caused by noise. Judgment can be performed, and the detection capability of the object detection device can be increased.

According to the second aspect of the present invention,
Since the threshold value is decreased as the detection time of the object measured by the first measurement unit is prolonged, the object can be reliably detected when there is a high possibility that the peak signal is of the object.

According to the third aspect of the present invention,
Since the prediction area is widened as the detection time of the object measured by the first measurement unit becomes longer, the detection omission of the object is reliably prevented when there is a high possibility that the peak signal is of the object. be able to.

According to the invention described in claim 4,
The existence time of the peak signal in the prediction area is measured by the second measurement means, and when the existence time of the peak signal is equal to or more than a predetermined value, it is determined that the detected signal is the detected peak, so that the influence of noise is effectively eliminated. Thus, the reliability of the detected peak can be improved.

According to the invention described in claim 5,
Since the detection peak is determined using the value obtained by adding the frequency analysis results a plurality of times, the influence of the sporadic noise can be reliably eliminated, and the reliability of the detection peak can be further improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an object detection device.

FIG. 2 is a graph showing a relationship between a distance between a vehicle and an object and a detection level.

FIG. 3 is a time chart showing a change in a detection level over time.

FIG. 4 is a flowchart illustrating an operation.

FIG. 5 is an overall configuration diagram of a conventional object detection device.

FIG. 6 is a graph showing waveforms and peak frequencies of transmission / reception waves when an object is moving closer to the transmission / reception antenna;

FIG. 7 is a graph showing a peak signal detected by a detection peak determination unit.

[Explanation of symbols]

 Reference Signs List 6 transmitting / receiving antenna (transmitting / receiving means) 7 mixer 13 frequency analyzing means 14 detection peak determining means 15 object detecting means 16 peak signal frequency predicting means 17 first measuring means 18 second measuring means 19 adding means 20 threshold changing means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H180 AA01 CC12 CC14 CC30 LL01 LL04 5J070 AB19 AD01 AE01 AF03 AH25 AH31 AH35 AK22

Claims (5)

[Claims] A transmitting / receiving means for transmitting an FM-CW wave and receiving a reflected wave of the FM-CW wave from an object; and a mixer for generating a beat signal by mixing the transmitted wave and the received wave. 7), frequency analysis means (13) for frequency-analyzing the beat signal obtained by the mixer (7), and a peak signal obtained based on the frequency analysis results on the ascending and descending sides by the frequency analyzing means (13). A detection peak determining means (14) for determining a peak signal not less than a threshold value as a detection peak; and a distance to the object and an object based on the ascending and descending detection peaks obtained by the detection peak determining means (14). Object detection means (15) for calculating at least one of the relative velocities of the object and the vehicle. Peak signal frequency predicting means for (16)
And a threshold changing means (20) for changing the threshold, wherein the detected peak determining means (14) is provided in the prediction area including the peak signal frequency predicted by the peak signal frequency predicting means (16). An object detection device for a vehicle, wherein a peak signal equal to or greater than the threshold value changed in (20) is determined as a detection peak. 2. The method according to claim 1, further comprising: a first measuring unit configured to measure a time during which the object is detected by the object detecting unit, the detection time of the object measured by the first measuring unit. The object detection device for a vehicle according to claim 1, wherein the threshold value is reduced as the length of the vehicle becomes longer. 3. The vehicle object detection device according to claim 2, wherein the prediction area is widened as the detection time of the object measured by the first measurement unit (17) increases. . 4. A second measuring means (18) for measuring the existence time of an arbitrary peak signal obtained from the frequency analysis result by the frequency analyzing means (13), and the detected peak determining means (14) When the existence time of a peak signal in the prediction area measured by the second measuring means (18) is equal to or longer than a predetermined value, the peak signal is determined as a detected peak. 4. The object detection device for a vehicle according to claim 3. 5. An addition means (19) for adding a frequency analysis result by the frequency analysis means (13) a plurality of times, and a detection peak determination means (14) converts the frequency analysis result obtained by the addition means (19). 5. The method according to claim 1, wherein the determination of the detection peak is performed using the detection peak.
Item 10. The vehicle object detection device according to Item 7.