JP3126495B2 - In-vehicle collision prevention radar system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collision prevention radar device for a vehicle, which is mounted on a vehicle and detects a target entering or leaving a front lane and issues an alarm.

[0002]

2. Description of the Related Art In order to ensure the safe running of a vehicle, an on-vehicle collision prevention radar device has been conventionally developed. In this device, an aerial is arranged in front of a vehicle, and a radio wave is transmitted and received by the aerial to detect a target (such as another vehicle) in front of the vehicle. That is, a radio wave is transmitted from the aerial to the front of the vehicle, a reflected wave from a target existing in front is received, and the approach of the target is detected based on received power and the like. As a result, a warning can be issued to the vehicle operator or the like, or a signal can be given to the braking control device to ensure safe traveling of the vehicle.

[0003]

However, the conventional on-vehicle collision prevention radar apparatus has a problem that a blind area is generated in front of the vehicle or an unnecessary target is captured.

First, consider the case where an antenna pattern is set as shown in FIG. As shown in this figure, when the target is to be detected only by the main lobe, the main lobe is made to cover the lane width at the point of the maximum detection distance. In this case, the maximum detection distance is 100 m.

[0005] However, with such a setting, a blind area shown by hatching in the figure occurs.
That is, when a target enters a region indicated by oblique lines in the figure, the target is not a target of an alarm or the like because the reflected power is low even though the target is relatively close to the own vehicle. This is a drawback in ensuring proper collision prevention.

In order to avoid such a blind area, a side lobe may be used as shown in FIG. However, when the side lobes are out of the lane, a target existing in a region shown by oblique lines in the figure is captured. Therefore, a process for discriminating between the unnecessary target and the necessary target is required, and the system configuration becomes complicated.

An object of the present invention is to solve such a problem, and an object of the present invention is to prevent a blind area from being generated and an unnecessary target from being captured.

[0008]

In order to achieve the above object, according to the present invention, the total gain of the transmitting and receiving antennas is set to approximately d ⁴ / sin ⁴ θ (d: lane width / 2, θ: vehicle center line). The power of the reflected wave received by the antenna when the target crosses the side of the rectangular area of the lane width extending along the traveling lane and a predetermined distance in front along the traveling lane. Is made substantially constant.

A second aspect of the present invention is characterized in that the threshold value of the power of the received reflected wave is determined to detect the entry or departure of a target into or from a rectangular area.

A third aspect is characterized in that the threshold value is variably set according to the type of the target. And Claim 4
Is characterized in that the threshold value is variably set according to the lane width.

[0011]

According to the present invention, the gain of the total transmission and reception of the antenna is set to a characteristic that is approximately proportional to d ⁴ / sin ⁴ θ.
That is, the characteristics are set as shown in FIG. Then, when the target enters or leaves the rectangular area as shown in FIG. 2, the power of the reflected wave received by the antenna becomes substantially constant. Therefore, for example, a blind area as shown in FIG. 6 does not occur, and a target existing outside the lane as shown in FIG. 7 is not captured. As a result, it is possible to more appropriately capture the target existing in front of the vehicle to prevent collision, and to determine the power of the received reflected wave as a threshold value, for example, as described in claim 2. It is possible to detect the entry of the target by simply performing the operation, thereby simplifying the signal processing and the system configuration.

In the third and fourth aspects, the threshold value is variably set according to the type of the target or the lane width. Therefore, it is possible to know not only the entry of the target into the rectangular area or the like, but also what kind of target the entry or the like is (for example, whether it is a truck or a passenger car). Alternatively, it is possible to perform suitable target detection according to the lane width.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows the configuration of an on-vehicle collision prevention radar device according to an embodiment of the present invention. The device shown in this figure is a transmitting and receiving antenna 1 arranged at the front of the vehicle.
0, a transmitting unit 1 that outputs a transmitting signal to the transmitting / receiving antenna 10
2. A receiving unit 14 for receiving a reflected wave from a target by the transmitting / receiving antenna 10, a gyrator 16 for sharing the transmitting / receiving antenna 10 between the transmitting unit 12 and the receiving unit 14, and processing such as amplification and detection by the receiving unit 14. The determination unit 18 performs a threshold determination on the power of the reflected wave thus determined, and a threshold table 20 referred to by the determination unit 18.

This embodiment is characterized in that the first
2 shows an antenna pattern of the transmitting and receiving antenna 10. The antenna pattern of the transmitting / receiving antenna 10 is set as shown in FIG. In other words, not only the main lobe but also a plurality of side lobes are used to cover a rectangular area with a maximum detection distance of 100 m and to prevent the occurrence of blind areas and the protruding side lanes of other side lobes. When the pattern of the transmitting and receiving antenna 10 is represented by a function of the angle θ with respect to the vehicle center line, the pattern approximately matches the antenna pattern shown in FIG. Thus, FIG.
By using the antenna pattern as shown in FIG. 2, a rectangular area as shown in FIG. 2 is approximately realized, no blind area is generated, and a target outside the lane is captured. Is gone.

This will be described in more detail below. First, when the power transmitted from the transmitting and receiving antenna 10 is P _t , the wavelength is λ, the gain of the transmitting and receiving antenna 10 is G, the reflection area of the target is σ, and the distance to the target is r, the reception of the transmitting and receiving antenna 10 is performed. The power _Pr is obtained by the following radar equation.

[0017] _{P r = {P t · σ} · λ 2 · G 2} / {(4π) 3 R 4} Here, the lane width / 2 d, the orientation of the target object relative to the vehicle center line θ Then, the distance r to the target is expressed as r = d / sin θ, and the received power Pr is as follows when the reflection area σ is a constant.

P _r = K · G ² · sin ⁴ θ / d ⁴ where K is a constant including the reflection area σ, wavelength λ, and the like.

Therefore, when the received power Pr is kept constant, the gain G of the transmitting and receiving antenna 10 may be made to have a characteristic proportional to d ² / sin ² θ. That is, the transmitting and receiving antenna 1
The gain of the total transmission and reception of 0 may be a characteristic proportional to d ⁴ / sin ⁴ θ. In this way, a rectangular area of transmission / reception power as shown in FIG. 2 is obtained. In the present embodiment, this region is approximately realized.

The second feature of this embodiment is the operation of the threshold value judgment by the judgment unit 18. That is,
Reflected power P _r obtained when target enters the range of the forward lane 100m is constant by setting the antenna pattern as described above. Therefore, in the determination unit 18,
The approach of the target can be detected only by determining the threshold value of the reflected power.

For example, a threshold value is set within a range shown by oblique lines in FIG. This threshold value is stored in the threshold value table 20 in association with the reflection area σ and the lane width d. The determination unit 18 sets a threshold value for determination based on a vehicle type, a lane width, or the like set by a vehicle operator or the like, or automatically with reference to a threshold value table 20.

[0022] For example, in the case of detecting a target object reflection area σ is large as the track is compared with the target object reflection area σ is small, such as passenger cars, the threshold according to the determination of the received power P _r Set large. This is the received power _Pr
And the reflection area σ is proportional. When the lane width is large, the threshold value is set relatively small. This received power P _r is inversely proportional to the fourth power of d is 1/2 of the lane width. The determination unit 18 supplies the result obtained by this determination to the alarm device and the braking control device.
As a result, a warning is issued to the vehicle operator or the like as necessary, or braking control of the vehicle is performed.

In the above description, transmission and reception are performed by a single antenna 10, but the transmitting antenna and the receiving antenna may be separated. In addition, a rectangular equal reflection power range is approximately realized by using side lobes. Instead, a plurality of antennas are provided on the left and right of the entire vehicle, and the rectangular area is covered by a total antenna pattern. It is good also as something like.

[0024]

As described above, according to the present invention,
Since the total gain of the transmitting and receiving antennas is approximately proportional to d ⁴ / sin ⁴ θ, there is no blind area in the front lane, and the target, such as a target running in another lane, is captured. Will not occur. As a result,
Collision prevention can be more suitably performed, and signal processing is also simplified, so that the system configuration is simplified.

According to the second aspect, since the power of the received reflected wave is determined by the threshold value to detect the entry of the target or the like, complicated signal processing becomes unnecessary. In addition, by setting the threshold value variably according to the periphery of the target as described in claim 3, or variably setting according to the lane width as described in claim 4,
A suitable collision prevention operation according to the type of the target and the lane width can be executed.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of the present invention, particularly an antenna pattern.

FIG. 2 is a diagram showing the principle of the present invention, in particular, an equal reflection power range.

FIG. 3 is a block diagram showing a configuration of a vehicle-mounted collision prevention radar device according to one embodiment of the present invention.

FIG. 4 is a diagram showing an antenna pattern obtained in this embodiment.

FIG. 5 is a diagram showing setting of a threshold value in this embodiment.

FIG. 6 is a diagram showing a problem in which an antenna pattern, particularly a blind area, occurs in a vehicle-mounted collision prevention radar device according to a conventional example.

FIG. 7 is a diagram showing a problem of capturing an antenna pattern of an in-vehicle collision prevention radar device according to a conventional example, particularly an unnecessary target.

[Explanation of symbols]

10 of the transmitting and receiving antenna 12 target object relative to the radar cross θ vehicle center line of 1/2 sigma target of the transmission unit 14 reception unit 18 determination unit 20 threshold value table d lane width direction P _r antenna reception power

Continuation of the front page (72) Inventor Koichi Morita 5-1-1 Shimorenjaku, Mitaka-shi, Tokyo Japan Radio Co., Ltd. (56) References JP-A-58-63871 (JP, A) JP-A-2-287181 (JP, A) JP-A-2-259586 (JP, A) JP-A-5-223932 (JP, A) JP-A-5-273340 (JP, A) JP-A-53-20789 (JP, A) Kaihei 3-105016 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95 G05D 1/02 G08G 1/16

Claims (4)

(57) [Claims] 1. An antenna disposed in front of a vehicle traveling in a lane having a predetermined width, a transmitting unit for transmitting radio waves by the antenna, and a reflected wave by a target such as another vehicle existing in front of the vehicle by the antenna. A receiving unit for receiving, and a determining unit for detecting the entry or departure of the target to the lane ahead of the vehicle by determining the power of the received reflected wave, a warning device for a signal related to the warning of the target, a braking device In an on-vehicle collision prevention radar device supplied to a control device, etc., the total gain of transmission and reception of the antenna is approximately d ⁴ / sin ⁴ θ
(D: lane width / 2, θ: azimuth based on vehicle center line)
The power of the reflected wave received by the antenna when the target crosses the side of the rectangular area of the lane width over the predetermined distance along the traveling lane along the traveling lane is made substantially constant. An in-vehicle collision prevention radar device characterized by the above-mentioned. 2. The in-vehicle collision prevention radar device according to claim 1, wherein the determination unit determines whether the target enters or leaves the rectangular area by determining a threshold value of the power of the received reflected wave. An in-vehicle collision prevention radar device characterized by detecting. 3. The on-vehicle collision prevention radar device according to claim 2, wherein the threshold value is variably set according to the type of the target. 4. The on-vehicle collision prevention radar device according to claim 2, wherein the threshold value is variably set according to the lane width.