JPH0894749A - Obstacle detector - Google Patents

Abstract

PURPOSE: To perform the accurate obstacle detection for a front vehicle by transmitting an FM-CW wave as a transmitted wave, mixing the received wave reflected from a reflecting body (front obstacle) with the transmitted wave so as to form the beat signal, analyzing the frequency of the beat signal, measuring the relative speed and the distance with the reflecting body, and discriminating a street-lamp post shaped body. CONSTITUTION: The result of the frequency analysis of a beat signal is received, and the peak frequencies on the rising side and the falling side are obtained. When the peak frequencies are generated for a plurality of reflecting bodies, the estimated distances after the specified time are computed for all combinations of the peak frequencies on the rising side and the falling side. The distance in the combination, wherein the estimated distance and the actually measured distance agree, is selected as the distance to a front vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an obstacle detection device,
In particular, the present invention relates to an apparatus for detecting an obstacle by emitting an FM-CW wave to a front object and measuring the distance and relative speed to the front object.

[0002]

2. Description of the Related Art FIG. 10 shows a fixed single beam FM-C.
The radar detection range θ (one side θ / 2 [ra
d]) is illustrated, and the detection distance is D = 100 [m]
Up to.

On the other hand, when the vehicle travels on a curved road, as shown in FIG. 11, the radius of curvature R on a curved road such as a highway is, for example, in a separated cross section where the up line and the down line of the road are not on the same plane. In the case of a two-lane road, it is defined up to the center of the dividing line (dotted line) of each lane.

Therefore, on such a curved road, the radar beam width θ from the vehicle 20 is θ as shown in FIG.
[rad], but the radar effective distance in the case of being surrounded by the soundproof wall W as the road shoulder protection body is as follows.

That is, the soundproof wall W when the vehicle is traveling on the right lane on the left lane of a two-lane road having a radius of curvature R [m]
A geometrical relationship where the radius of curvature of r is r [m] is shown in FIG. 13. In this case, the center position C of the vehicle is the coordinate (0, p) on the y axis, and the beam width is θ. / 2 [rad], the intersection coordinates of this beam and the soundproof wall W are (S,
y ₁ ) and (L, y ₂ ) (provided that S <L).

In such a geometrical relationship, the following equation is obtained.

[0007]

[Equation 1] Therefore, the values S and L that give the coordinates of the intersection of the beam and the soundproof wall W are expressed by the following equations.

[0008]

[Equation 2] In this case, if the own vehicle 20 as shown in FIG.
If there is no obstacle such as a vehicle in front of, the above coordinate values S ~
Up to L, the soundproof wall W is irradiated with radar.

[0009]

On the other hand, when there are obstacles such as the vehicle 21 within the radar detection range (θ) in front of the vehicle 20, as shown in FIG. Since an electromagnetic wave does not reach the wall of the vehicle and the streetlight pole LP, obstacles can be detected only by the front vehicle, and there is no problem as an obstacle detection device, but there is no obstacle in front as shown in (1) of FIG. Then, the rear lamppost LP is directly detected.

However, under the present circumstances, it is possible to discriminate the soundproof wall by using the spectrum shape in the frequency analysis of the electromagnetic wave (Japanese Patent Application No. 6-26687), but in the FM-CW system, it is the rising side in the modulation pattern. If the beat frequency on the descending side is not accurately combined, the speed and distance of the reflecting object cannot be obtained, so that the streetlight column LP as a non-vehicle object is determined to be a “stop vehicle” or an “obstacle”.

Therefore, the present invention transmits an FM-CW wave as a launch wave, mixes the received wave reflected by a reflecting object (front obstacle) with the launch wave to generate a beat signal, and frequency-converts the beat signal. In a device for detecting an obstacle by analyzing and measuring a relative speed and a distance to the reflecting object, a lamppost in a curved road is accurately obtained by accurately obtaining a combination of beat frequencies on an ascending side and a descending side in a modulation pattern. The purpose is to discriminate a shape object and accurately detect obstacles in front of the vehicle.

[0012]

In order to achieve the above object, an obstacle detecting device according to the present invention is raised in response to a result of frequency analysis of a beat signal obtained by mixing a launch wave and a received wave. Side and falling side peak frequencies are calculated, and when the peak frequencies occur for a plurality of reflecting objects, the predicted distance after a predetermined time is calculated for all combinations of the rising side and falling side peak frequencies, and the predicted distance and the actual distance are calculated. A calculation unit that selects a distance in a combination in which the measured distances are the same as the distance to the vehicle ahead is provided.

It should be noted that the above arithmetic unit can provide rear protection and front protection by using a predetermined parameter for the determination of the coincidence, and further provide limiter values for the rear protection and front protection. You can also

[0014]

In the obstacle detecting device according to the present invention, the calculating part mixes the emitted wave and the received wave to generate a beat signal and analyzes the frequency of the beat signal.

Then, the peak frequency on the rising side and the peak frequency on the falling side are calculated based on the result of the frequency analysis. When these rising and falling peak frequencies are for a single reflective object,
Since the relative distance calculated by the combination of both produces only a single correct value, it is used as it is as the detection distance.

However, when there are a plurality of reflecting objects in front of the vehicle, the peak frequency on the ascending side and the peak frequency on the descending side occur in correspondence with the number of the reflecting objects, and are calculated by the combination of both. I do not know which relative distance is correct.

Therefore, in the present invention, the next predicted distance after a predetermined time is calculated for all combinations of the rising and falling peak frequencies. Then, a combination in which the calculated predicted distance matches the distance actually measured after the predetermined time is detected, and the distance in this combination is selected as the distance to the preceding vehicle.

In this way, it is always accurately discriminated whether the reflecting object is a vehicle or a streetlight pole on a curved road. For example, when the detection distance becomes too short, an alarm is generated and safe driving is performed. Can be urged.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An obstacle detecting device according to the present invention will be described below by taking an "in-vehicle distance measuring device using an electromagnetic wave radar" as an example. Regarding the electromagnetic wave detection method and the electromagnetic wave sensor, the FM-CW method is taken as an example, and therefore the explanation will be made assuming that "the relative velocity and relative distance can be measured" by the detection.

FIG. 1 is a block diagram showing an embodiment of an obstacle detecting apparatus according to the present invention. In the figure, 1 is a transmitting antenna, 2 is a transmitting circuit, and 3 is a VCO (voltage controlled oscillator). Including a modulation circuit, 4 is a receiving antenna, 5 is a receiving circuit, and 6 is a mixer, and the transmitting circuit 2 and the modulating circuit 3 constitute a radio wave transmitting device, and the receiving circuit 5 is a radio wave receiving device. I am configuring.

The signal to be supplied to the modulation circuit 3 is generated by the signal generation circuit 8, which constantly receives the clock signal from the synchronization signal generation circuit 9, and further stores the modulation pattern which is composed of ROM or RAM. Upon receiving the modulation pattern composed of the triangular shape and the linear part stored in the section 11, the modulated wave as shown in FIG. 2 is generated.

The output signal of the mixer 6 is supplied to the demodulation circuit 7. The output signal of the demodulation circuit 7 is supplied to the demodulation signal separation circuit 12 to be signal-separated and further frequency analyzed as a digital signal.・ Signal processing unit 13
The frequency analysis result is sent to the CPU 10, which is provided to the CPU 10 as the determination unit which is a characteristic part of the present invention to output a determination signal.

The demodulation signal separation circuit 12 is also configured to receive the synchronization signal from the synchronization signal generation circuit 9.

Further, 14 is the measured data and CPU
Reference numeral 10 is a storage unit that stores data that is predicted and calculated (described later), and reference numeral 15 is a vehicle speed sensor that detects the actual vehicle speed.

Next, the operation of the obstacle detecting device will be described with reference to the flow chart shown in FIG.

Step S1: First, in order to perform electromagnetic wave sensing, when the CPU 10 instructs the modulation pattern storage unit 11 to output a modulation pattern, the storage unit 11 outputs a modulation signal as shown by the solid line in FIG. The data for forming is output to the signal generation circuit 8.

In response to this, the signal generation circuit 8 converts the modulation signal data into the analog signal a, and the modulation circuit (VCO).
3 and the signal b subjected to the triangular frequency modulation is transmitted via the transmission circuit 2 and the transmission antenna 1.
Incidentally, these modulation patterns may be program type variable data by a CPU or the like.

When the emission wave transmitted from the transmission antenna 1 is reflected by the reflecting object (front vehicle) 21 and returns as shown in FIG. 4, this reflection wave is received by the reception antenna 4.

That is, FIG. 2 shows the time change of the waveform obtained by mixing the emission wave and the reception wave when the radar wave is reflected by a reflecting object, for example, a vehicle in front, and FIG. The solid line in () indicates the emitted wave (electromagnetic wave that is frequency-modulated in a triangular shape). If the object is a moving object and is reflected by a radio wave reflecting object such as a vehicle, the frequency as indicated by the dotted line is due to the Doppler effect. The reception wave shown by the dotted line in FIG.

Step S2: This received wave is converted into an electric signal by the receiving circuit 5, and the mixer 6 mixes the emitted wave and the received wave. This mixed signal is sent to the demodulation circuit 7, where it is converted into a beat signal c having a beat frequency as shown in FIG.

The beat signal frequency f _b is defined by the following (3)
It is expressed by the sum or difference of the distance frequency f _r and the speed frequency f _d which correspond to the distance and velocity of the radio wave reflecting object by formula.

[0032]

F _b = (4Δf · f _m / C) rd ± (2f _o / C) rv (3) = f _r ± f _d where rv: relative speed of the reflecting object to the radar sensor [m / sec] rd: the relative distance from the radar sensor to the reflection object [m] C: velocity of light [m / sec] △ f: frequency modulation width [Hz] f _m: modulation frequency [Hz] f _o: radar carrier frequency [Hz]

Here, when the beat frequency on the rising side of the modulated wave frequency is f _up and the beat frequency on the falling side is f _dn ,

[0034]

## EQU00004 ## f _r = 0.5 (f _up + f _dn ), f _d = 0.5 (f _up −f _dn ) ... (4) Then, according to the equations (3) and (4),

[0035]

[Equation 5] rv = (C / 2f _o ) f _d , rd = (C / 4Δf · f _m ) _fr (5), and the relative distance to the radio wave reflecting object is obtained by the equation (5). The rd and the relative velocity rv are obtained (see FIG. 4).

For simplification,

[0037]

[Expression 6] rv = α (f _up −f _dn ), rd = β (f _up + f _dn ) (6)

Step S3: The beat signal c is sent to the demodulation signal separation circuit 12 for sampling and
Here, the demodulation signal is separated based on the synchronization signal from the synchronization signal generation circuit 9, and the information thereof is analyzed by the frequency analysis / signal processing unit 1.
Send to 3.

Step S4: The frequency analysis / signal processing unit 13 performs frequency analysis on the beat signals c of the emitted wave and the received wave. This frequency analysis means, as shown in FIG. 5, a portion where the frequency rises (UP side portion) and a portion where the frequency falls (DN side portion) in the frequency modulation pattern.
And the beat frequency (= peak frequency) according to the relative velocity and relative distance of the radio wave reflecting object is analyzed using FFT (Fast Fourier Transform), etc. A determination is made and the peak frequencies on the UP side and the DN side are output.

Then, the CPU 10 finds a combination of peaks as will be described later, and from FIG. 4 based on the above equations (3) to (5).
The distance rd and the relative velocity rv of the radio wave reflecting object shown in are calculated. Further, the vehicle speed is fetched from the vehicle speed sensor 15, and the props and the like are determined by comparing the calculated results of the relative speed rv and the relative distance rd.

Step S5: In this step, when there are a plurality of reflecting objects (when there is a streetlight pole on a curved road), a combination of the peak frequency f _up on the UP side and the peak frequency f _dn on the DN side is combined. Therefore, all of these combinations will be considered.

[1] Relative speed / relative distance calculation and combination (pairing): By combining the UP side peak frequency and the DN side peak frequency, the above (3) to (5)
From the formula, the relative speed and relative distance of the radio wave reflecting object are calculated. This is called pairing.

In the FM-CW system, in the case of a multi target (a plurality of reflecting objects), peaks corresponding to the number of reflecting objects are present on the UP side and the DN side. For example, when reflected by three objects, there are three UP-side peaks and three DN-side peaks.
There are 3 × 3 = 9 combinations of them. Therefore, nine types of detection data are generated, only three types of detection data are correct pairing, and the other six types of detection data are unnecessary.

[2] Concept of removing unnecessary detection distance data: The grounds for separating / removing unnecessary detection data will be described below with a slight separation from the flowchart of FIG. This shows that unnecessary data can be removed by predicting the detection data of the next time using the detection data at a certain time and comparing it with the actual detection data of the next time.

(A) Predicted distance error When predicting the distance to the target in the detection by the next sampling based on the detection data by the sampling this time, the relative speed detected this time is kept until the next detection. Computes the distance prediction value assuming that does not change. But,
Since an error occurs while the reflecting object and the vehicle are accelerating and decelerating,
First, the error will be examined.

Therefore, the current detection distance = rd [m] the current detection relative velocity = rv [m / sec] the detection interval time (= sampling time) = τ [sec] the actual relative acceleration = ra [m / se
c ² ] Next predicted distance = ed [m] Next actual distance = rr [m] Difference between predicted value and actual distance = εR [m].

The following equation is used to predict the distance to be detected next time. ed = rd + rvτ [m] (A-1)

If the relative acceleration does not change between samplings, the actual distance is given by the following equation. rr = rd + rvτ + 1 / 2raτ ² [m] (A-2)

Here, the formula (A-2) -the formula (A-1) = ε
R, and εR = 1 / 2raτ ² (A-3).

Assuming that the range of the acceleration a of the vehicle is | a | ≦ 0.5 G (G: = gravitational acceleration) (A-4), the range of the relative acceleration ra with respect to the target is thereby calculated. , | Ra | ≦ 1.0 G≈10 [m / sec ² ] ... (A-5).

Therefore, the distance difference εR is | εR | ≦ 5τ ² [m] (A-6). For example, if the sampling time is 0.1 [sec], the difference between the predicted value and the actual distance according to the formula (A-6) is | εR | ≦ 0.05 [m] That is, within ± 5 [cm] Becomes

Therefore, regarding the prediction of the distance, (A-
It can be said that there is no problem even if the equation (1) is used.

(B) Change in peak frequency of sampling interval The peak frequency for the target detected this time is UP side peak frequency = f _UP [Hz] DN side peak frequency = f _DN [Hz], and The detection data of this time is set as relative velocity = rv [m / sec] and distance = rd [m].

However, the relative velocity is positive in the approaching direction, the sampling time is τ [sec], and the relative acceleration is ra [m / sec ² ].
And the relative acceleration does not change between samplings. If the detection this time is the i-th time, the next detection is the (i + 1) -th time, and these will be represented by subscripts. The i + 1-th detection distance rd _{i + 1} is rv _{i + 1} = rv _i + raτ [m / s] (A-7).

Further, for example, α and β are α = -1 / 800 [m / s / Hz] and β = 1/1500 [m / H
z].

Further, when τ = 0.1 [sec] and this and Equation (6) and Equation (A-5) are substituted into Equation (A-7), (f _{UPi + 1} −f _UPi ) = (F _{DNi + 1} −f _DNi ) + δ However, | δ | ≦ 800 [Hz] (A-8).

Here, the i-th peak frequency and the i + 1-th
Letting Δf be the difference between the peak frequencies at the first time, Δf _UP = Δf _DN + δ ... (A-9).

(C) Elimination of erroneous pairing When a plurality of targets are detected, there are n peak frequencies and m peak frequencies for each target.

Here, for simplification, it is assumed that two targets are detected and two peak frequencies are present on each of the UP side / DN side. The two targets will be referred to as target 1 and target 2, respectively, and the detection data of each target will be as follows with the current detection as the i-th time.

* Target 1 peak frequency: f1 _UPi [Hz], f1 _DNi [Hz] Relative speed: rv1 _i = α (f1 _{UPi −f1 DNi} ) [m / s] _··· (A-10) Distance: rd1 _i = Β (f1 _UPi + f1 _DNi ) [m] _··· (A-11) * Target 2 peak frequency: f2 _{UPi + 1} [Hz], f2 _DNi [Hz] Relative speed: rv2 _i = α (f2 _{UPi −f2 DNi} ) [m / s] ··· (A-12) Distance: rd2 _i = β (f2 _UPi + f2 _DNi ) [m] _··· (A-13)

For simplification, when the relative acceleration with respect to the target is 0, δ = 0 in the equation (A-9), that is, the amount of change between the UP side and DN side peak frequencies of the sampling interval is treated as the same. Δ the peak frequency change of 1
Let f1 [Hz] and the amount of change of the target 2 be Δf2 [Hz].
Therefore, the next i + 1-th detection data is as follows.

* Target 1 peak frequency change amount: Δf1 Peak frequency: f1 _{UPi + 1} = f1 _UPi + Δf1 (A-14) f1 _{DNi + 1} = f1 _DNi + Δf1 (A-15) Relative speed: rv1 _{i + 1} = α (f1 _{UPi + 1 −f1 DNi + 1} ) (A-16) Distance: rd1 _{i + 1} = β (f1 _{UPi + 1} + f1 _{DNi + 1} ) (A-17) ) * Target 2 peak frequency variation: Δf2 Peak frequency: f2 _{UPi + 1} = f2 _UPi + Δf2 ・ ・ ・ (A-18) f2 _{DNi + 1} = f2 _DNi + Δf2 ・ ・ ・ (A-19) Relative speed: rv2 _{i +1 = α (f2 UPi + 1} -f2 DNi + 1) ··· (A-20) _{distance: rd2 i + 1 = β (} f2 UPi + 1 + f2 DNi + 1) ··· (A-21)

However, it is assumed that α = −1 / 800 [m / sec / Hz], β = 1/1500 [m / Hz] (A-22).

Here, there are four sets of detection data by random pairing in the i-th detection, and the above (rv1i, r
Besides (d1i) and (rv2i, rd2i), there are (rv3i, rd3i) and (rv4i, rd4i). However, rv3 _i = α (f1 _{UPi −f2 DNi} ) ... (A-23) rd3 _i = β (f1 _UPi + f2 _DNi ) ... (A-24) _{rv4 i} = α (f2 _{UPi −f1 DNi} ) ... (A-25) rd4 _i = β (f2 _UPi + f1 _DNi ) ... (A-26)

Here, the random pairing is shown in FIG.
As shown in (1) and (2), if the combination is represented by the UP-side peak frequency and DN-side peak frequency of the target 1 and the UP-side peak frequency and DN-side peak frequency of the target 2, (,), (,),
There are four ways of pairing: (,) and (,).

There are also four sets of detection data by random pairing in the (i + 1) th detection, and (rv1 _{i + 1} , r
In addition to d1 _{i + 1} ) and (rv2 _{i + 1} , rd2 _{i + 1} ), (rv3
_{i + 1, rd3 i + 1} ) and _{(rv4 i + 1, rd4 i} + 1) is.
However, rv3 _{i + 1} = α (f1 _{UPi + 1 −f2 DNi + 1} ) (A-27) rd3 _{i + 1} = β (f1 _{UPi + 1} + f2 _{DNi + 1} ) (A-28) ) Rv4 _{i + 1} = α (f2 _{UPi + 1 −f1 DNi + 1} ) (A-29) rd4 _{i + 1} = β (f2 _{UPi + 1} + f1 _{DNi + 1} ) (A-30)

By the above (a), the predicted value ed of the (i + 1) th detection distance is obtained by the following equation based on the i-th detection data. ed = rd _i + rv _i τ [m] (A-31)

Then, the prediction of the (i + 1) th distance is performed as follows with the set of detection data by the i-th random pairing. ed1 = rd1 _i + rv1 _i τ = β (f1 _UPi + f1 _DNi ) + ατ (f1 _{UPi −f1 DNi} ) ... (A-32) ed2 = rd2 _i + rv2 _i τ = β (f2 _UPi + f2 _DNi ) + ατ (f2 _UPi − f2 _DNi ) ... (A-33) ed3 = rd3 _i + rv3 _i τ = β (f1 _UPi + f2 _DNi ) + ατ (f1 _{UPi −f2 DNi} ) · (A-34) ed4 = rd4 _i + rv4 _i τ = β ( f2 _UPi + f1 _DNi ) + ατ (f2 _{UPi −f1 DNi} ) ・ ・ (A-35)

Further, (A-17), (A-21), (A
-28), (A-30) expressions and (A-14), (A-1
5), (A-18), and (A-19), the actual distance detection data are as follows. rd1 _{i + 1} = β (f1 _UPi + f1 _DNi + 2Δf1) ・ ・ ・ (A-36) rd2 _{i + 1} = β (f2 _UPi + f2 _DNi + 2Δf2) ・ ・ ・ (A-37) rd3 _{i + 1} = β (f1 _UPi + f2 _DNi + Δf1 + Δf2) ... (A-38) rd4 _{i + 1} = β (f2 _UPi + f1 _DNi + Δf1 + Δf2) ... (A-39)

Here, a pair of detection data for correct pairing at the i-th time and the i + 1-th time, (rv1 _i , rd1 _i ) and (rv1 _{i + 1} , rd1 _{i + 1} ) and (rv2 _i , rd2 _i )
And (rv2 _{i + 1} , rd2 _{i + 1} ) determine Δf1 and Δf2.

That is, assuming that rd1 _{i + 1} = rd1 _i + rv1 _i τ, Δf1 = ατ (f1 _{UPi −f1 DNi} ) / 2β or = from equations (A-10), (A-11) and (A-36) rv1 _i τ / 2β (A-40), and similarly Δf2 = ατ (f2 _{UPi −f2 DNi} ) / 2β or = rv2 _i τ / 2β (A-41).

By the way, the above ed1 and ed2 are correct pairings for the targets 1 and 2,
3 and ed4 are predicted values by pairing.

Of these, first, ed3 will be examined in the following cases. When ed3 = rd1 _{i + 1} : (A-34), (A-3
From (6) and (A-40), (f2 _DNi- f1 _DNi ) (ατ-β) = 0 (A-42)

However, from the expression (A-22), (ατ
Since -β) ≠ 0, f2 _DNi = f1 _DNi ... (A-43). In this case, there are two UP side peak frequencies,
The number of DNs on the DN side is one from the equation (A-43), and the pairing is correct with the same peak frequency for the two targets.

When ed3 = rd2 _{i + 1} : (A-3
4), (A-37) and (A-41), (f2 _UPi- f1 _UPi ) (ατ + β) = 0 (A-44)

Since (ατ-β) ≠ 0 since τ = 0.1, f2 _UPi = f1 _UPi ... (A-45). On the contrary, there are two peak frequencies on the DN side, but U
There is one on the P side from the equation (A-45), and the pairing is correct with the same peak frequency for the two targets.

When ed3 = rd3 _{i + 1} : (A-3
4), (A-38), (A-40) and (A-41), (f1 _UPi + f1 _DNi ) = (f2 _UPi + f2 _DNi ) ... (A-46). In this case, for example, as shown in FIG. 7, it corresponds to a situation in which two targets whose traveling directions are opposite to each other are detected.

However, this situation is only during the i-th detection, and the data due to erroneous pairing can be removed by observing the consecutive detection situations before and after. When ed3 = rd4 _{i + 1} : (A-34), (A-3
9), (A-40) and (A-41), (f1 _{UPi −f2 UPi} ) (ατ / β + 1) + (f1 _{DNi −f2 DNi} ) (ατ / β-1) = 0 ( A-47)

In _summary , (f1 _{UPi-f2 UPi} ) (ατ + β) / (ατ-β) + (f1 _{DNi- f2 DNi} ) = 0 (A-48)

By the way, in order for the expression (A-48) to hold for an arbitrary τ, it must be f1 _UPi = f2 _UPi and f1 _DNi = f2 _DNi (A-49).

At this time, there is only one random pairing, and therefore, the pairing is correct since it is the same as the case where there is only one target.

However, with α, β, and τ as examples, since the expression (A-48) holds even in cases other than the expression (A-49), erroneous pairing occurs. By observing the continuous detection status of, the data due to erroneous pairing can be removed as described later.

Further, even if δ in the equation (A-9) is taken into consideration, the same results as in the above items 1 to 4 can be obtained.

The examination result of this ed3 is e
The same applies to d4.

Therefore, the predicted value in the detection data by the random pairing of the current detection is the random value of the next detection.
If it matches the detection data from the alling, it is correct
It is pairing, and data due to incorrect pairing can be removed.
So that the kill.

(D) Removal of Street Lamp Posts on Curved Roads The situation where street lamp posts are detected on a curved road is as follows: For radar-equipped vehicles = (hereinafter referred to as own vehicle), a stationary object is detected in front. be equivalent to. However, from the perspective of the host vehicle, the situation in which the host vehicle approaches the stopped object can be regarded as a linear approach from the front (at a speed equal to the host vehicle speed).

Here, the situation of approaching a stationary object from the front and the situation of detecting a streetlight pole on a curved road will be examined by replacing them with a straight road.

In FIG. 8 (1), it is assumed that the distances are detected in the order indicated by the arrows, and the own vehicle (apparent stop ST) appears at each detection interval.
When 20 moves D [m], it moves D [m] in the circumferential direction on the curved road shown in (2) of the figure. L
A difference ΔD occurs in the detected relative distance when P is detected.

That is, when the amount of change in the relative distance is predicted with respect to the detected relative speed, the predicted value and the next detected data do not match because the predicted value on the curved road is smaller than the predicted value.

Therefore, even for a streetlight pole on a curved road
Based on the detection data of this time, the next detection relative distance as described above
If you predict the separation, by comparing with the next detection data,
It is possible to remove the streetlight post data for this time.

Step S6: The above grounds (a) to (d)
Thus, “the next predicted detection relative distance is calculated based on the current detection data, and if there is a match in the next detection data, the detection data is output from the next time. , The correct detection data of the target will be output.

However, due to the nature of electromagnetic waves, it may become undetectable in spite of the presence of the target due to multipath (a phenomenon in which the level of the reflected wave is lowered due to radio wave interference and an accurate beat frequency cannot be obtained). But
If the object is a moving object, this phenomenon is instantaneous, and it is possible to eliminate such an undetectable state by making a plurality of determinations.

Therefore, in the present embodiment, the "data output possible parameter" is used as a concept similar to the flag, and this value is used to output correct data by the comparison between this time and the next time, and the data for data loss due to multi-pass. Corrected pairing data output / non-output was adjusted by compensation.

Then, the initial value of the data output enable parameter is set as C (for example, "7") for each detection data of random pairing (referred to as random detection data).

Step S7: Next, as shown in FIG.
This time (i-th) in the memory block of the data storage unit 14
Random detection data and data output possible parameters are stored. However, the random detection data of this time is stored in the term of the predicted distance.

The next (i + 1) th detection distance is predicted from the data in the memory block by the following equation, and this is updated to the prediction distance term in the block. Predicted distance: = predicted distance (within block) + relative velocity x τ

Random pairing is also performed in the (i + 1) th detection, the same processing as described above is performed on the random detection data, and the data is stored in another memory block.

Steps S8 and S9: The terms of the predicted distances of the (i + 1) th random detection data and the i-th random detection data are compared, and if they match, this random pairing is correct as described above. Then, the additional value P (for example, “7”) is added to the data output enable parameter of the block of the i + 1-th random detection data.

Steps S10 and S11: It is judged whether or not the data outputable parameter in the block is equal to or more than the maximum limiter value M (for example, "20") for backward protection, and M or more is limited to M.

Steps S8, S12, S13: i + 1th
The predicted distance terms of the random detection data for the second time and the random detection data for the i-th time are compared, and if they do not match, the subtraction value D (for example, “3”) is subtracted from the data output possible parameter to determine the prediction value in the detection block. Substitute for the item of this detection data.

Steps S14, S15: Then, it is judged whether or not the data outputable parameter is less than or equal to the minimum limiter value 0 for forward protection, and when it is less than 0, the detection block is cleared.

Steps S16 and S17: After that, it is determined whether or not the data output enable parameter is equal to or higher than the threshold TH (for example, "14"), and only when the threshold is equal to or higher than the threshold TH, the data of the detection block is output as correct detection data.

Step S18: Then, based on the detection data in the detection block in the memory, the next prediction value is obtained by using the above prediction formula, and is substituted in the prediction value term.

Steps S19 and S20: The block name is changed so that the block remaining in the memory is the block of the i-th random detection data, and the process returns to step S1 until the calculation is completed.

Therefore, if the above numerical examples are used, the threshold value TH = is obtained by continuously detecting twice at C + P = 14.
This is 14 or more, and the correct detection distance data is output (backward protection).

Since the upper limit value = 20 is not exceeded even if successive matches are made thereafter, the detection data is continued to be output in the case of a single mismatch, but the threshold value TH = 14 or less when the mismatches occur twice in succession. Therefore, the detection data is not output (forward protection).

It should be noted that the initial state is delayed by one detection interval time when an interrupting vehicle is generated, but this "delay" does not pose a problem with the advent of a high-speed processing device, for example.

[0108]

As described above, according to the obstacle detecting device of the present invention, the peak frequencies on the rising side and the falling side are obtained in response to the result of the frequency analysis of the beat signal, and the peak frequencies are plural. Predicted distance after a predetermined time is calculated for all combinations of peak frequencies on the ascending side and the descending side when occurring for a reflecting object, and the distance in the combination in which the predicted distance and the actually measured distance are the same as those of the preceding vehicle. Since the distance is selected, the false alarm can be reduced, and the vehicle on the curved road can be accurately distinguished from other obstacles without using a special element.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an obstacle detection device according to the present invention.

FIG. 2 is a transmission / reception waveform diagram of the obstacle detection device according to the present invention.

FIG. 3 is a flowchart of a detection process stored and executed in a CPU as a calculation unit used in the obstacle detection device according to the present invention.

FIG. 4 is a plan view for explaining the operation of the obstacle detection device according to the present invention.

FIG. 5 is a waveform diagram showing a spectrum of a modulation frequency in the obstacle detection device according to the present invention.

FIG. 6 is a diagram showing a spectrum of peak frequencies when two targets (reflecting objects) are present in the obstacle detection device according to the present invention.

FIG. 7 is a plan view showing a situation of detecting the moment when opposing targets pass each other in order to explain the operation principle of the obstacle detection device according to the present invention.

FIG. 8 is a diagram showing a configuration of a detection block in a memory in the data storage unit of the obstacle detection device according to the present invention.

FIG. 9 is a diagram showing an apparent distance change with respect to a stationary object and a streetlight column in order to explain the operation principle of the obstacle detection device according to the present invention.

FIG. 10 is a block diagram showing a detection range on a straight road of an obstacle detection device using an FM-CW wave which is generally known from the past.

FIG. 11 is a diagram for explaining a radius of curvature of a curved road on which a vehicle travels.

FIG. 12 is a diagram showing a state of a vehicle equipped with a radar in a curved road.

FIG. 13 is a diagram showing a geometrical relationship between a radar beam width and a radius of curvature.

FIG. 14 is a diagram showing a situation of detection of a streetlight pole in a curved road.

[Explanation of symbols]

 1 Transmission Antenna 2 Transmission Circuit 3 Modulation Circuit 4 Reception Antenna 5 Reception Circuit 6 Mixer 7 Demodulation Circuit 8 Signal Generation Circuit 9 Synchronous Signal Generation Circuit 10 CPU (Calculation Unit) 11 Modulation Pattern Storage Unit 12 Demodulation Signal Separation Circuit 13 Frequency Analysis / Signal Processing unit 14 Data storage unit 15 Vehicle speed sensor In the drawings, the same reference numerals indicate the same or corresponding portions.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G01S 13/34 13/60 D G08G 1/16 E

Claims (3)

[Claims] 1. An FM-CW wave is transmitted as a launch wave, a reception wave reflected by a reflecting object is mixed with the launch wave to generate a beat signal, and the beat signal is subjected to frequency analysis to obtain a beat signal from the reflecting object. In an apparatus for detecting an obstacle by measuring a relative speed and a distance, a peak frequency on an ascending side and a descending side is obtained in response to a result of frequency analysis of the beat signal, and the peak frequency is generated for a plurality of reflecting objects. When the predicted distance after a predetermined time is calculated for all combinations of the peak frequencies on the rising side and the falling side, and the distance in the combination in which the predicted distance and the actually measured distance match is selected as the distance to the vehicle in front. An obstacle detection device having a section. 2. The obstacle detection device according to claim 1, wherein the arithmetic unit is provided with rear protection and front protection using a predetermined parameter for the determination of the coincidence. 3. The obstacle detection device according to claim 2, wherein the arithmetic unit has a limiter value for each of the rear protection and the front protection.