JPH0475472B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a Doppler radar device for a vehicle that monitors targets such as other vehicles and obstacles located in the longitudinal direction of the vehicle traveling direction.

[Prior art] Conventionally, when a vehicle is running and is rear-ended by another vehicle,
Doppler radar devices for vehicles have been proposed to monitor these vehicles in order to prevent dangers such as collisions with obstacles while reversing.

Conventionally, in this type of vehicle radar device, as shown in FIG. 1, for example, a vehicle 4, which is a small target approaching a vehicle 2 traveling on a road surface 1, and a vehicle 6, which is a large target, are detected. However, the vertical beam angle θ ₀ of the radar antenna 8 was set to a certain value so that radio waves could be radiated.

In addition, in this type of vehicle radar device, when the radar antenna receives radio waves and recognizes the existence of a target object, when the received radio waves are above a predetermined level, the presence of the target object is recognized, and when the received radio waves are above a predetermined level, the radar antenna recognizes the presence of the target object. At this time, so-called range cut processing was performed to cut out this noise as noise.

In other words, the radio waves received by the radar antenna include radio waves emitted from the radar antenna that directly hit a target and are reflected, as well as radio waves that are emitted from the radar antenna and are reflected when they hit the road. After the radio waves emitted from the radar antenna hit the road, there are radio waves that hit a target and are reflected, and there are radio waves called noise that are not caused by the reflection of the radio waves emitted from the radar antenna. Of these radio waves, radio waves other than those that directly hit the target and are reflected cause erroneous recognition of the object's reputation. On the other hand, the radio waves that cause these misrecognitions are of a lower level compared to radio waves that directly hit the target and are reflected.
Therefore, conventionally, these low-level signals are removed by the range cut process to determine whether a target exists or not, thereby avoiding erroneous recognition of the target.

Furthermore, in addition to such range cut processing, methods have also been known in the past to avoid misrecognition of targets by eliminating detection of targets whose relative speed is below a predetermined value or by eliminating detection of targets that are moving away. Some devices have been designed to avoid misrecognition of targets by using these methods alone or in combination with range cut processing.

[Problems to be Solved by the Invention] However, in conventional vehicle radar devices, by detecting the frequency difference and phase difference between the emitted radio waves and the reflected radio waves from the target object, Relative speed and approach of target to vehicle
Although it is said that it is possible to detect the direction of departure, the distance to the target cannot be measured.

For this reason, although it is possible to avoid misrecognition of the target by performing the above-mentioned range cutting, etc.
When radio waves emitted from a radar antenna directly hit a target and the reflected waves are received directly, large vehicles such as buses have a large slope, so a high level signal can be obtained even at a long distance. However, because small vehicles such as passenger cars have small reflective surfaces, high-level signals cannot be obtained unless they are at close range, making it impossible to detect at long distances.

That is, as shown in FIG. 1, for example, a large vehicle 6 can be detected at a distance _l1 , but a small car 4 can be detected at an even shorter distance _l2 .

Therefore, in conventional vehicle radar devices, the detection distance differs depending on the target object, and the distance at which the target object can be detected (detection distance) is not constant and varies depending on the size of the object. Therefore, there was a problem that it was difficult to put it into practical use in terms of preventing rear-end collisions and collisions.

The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a method for detecting distance from a vehicle equipped with a radar device to a target object, regardless of the size of the target object such as a vehicle or an obstacle. An object of the present invention is to provide a vehicular Drapler radar device that can maintain a constant detection distance.

[Means for Solving the Problems] That is, the present invention, which has been made to achieve the above object, emits continuous waves in the opposite direction or the same direction as the traveling direction of the vehicle, and the continuous waves are present on the road surface. A vehicular radar device configured to detect relative speed and approach/departure direction to the target object from reflected waves directly hitting the target object and displaying the detection results on a display means, The vertical beam angle of the radar antenna that emits the continuous waves is narrowed, and the entire beam of the continuous waves produces an angle of depression, and the presence of the target only when the distance of the target with respect to the vehicle is within a predetermined distance;
The gist of this invention is a vehicle radar device that is characterized by being able to detect relative speed and approaching/departing directions.

[Function] As described above, in the vehicle radar device of the present invention, the vertical beam angle of the radar antenna is narrowed, and the entire continuous wave beam emitted from the radar antenna produces an angle of depression, so that the object to the vehicle is The presence of the target, relative speed, and direction of approach/departure can be detected only when the distance to the target is within a predetermined distance.

Therefore, even if the target on the road surface is a large vehicle such as a bus, the continuous waves will be reflected only at the bottom of the vehicle, and the reflective surface of the continuous waves will be substantially the same as that of a small vehicle such as a passenger car. There will be no difference between Therefore, the presence of the target is recognized only when the distance of the target to the vehicle is within a predetermined distance without being affected by the size of the target on the road surface, and the relative speed and speed of the target are determined. It becomes possible to detect approaching and departing directions.

Note that the above-mentioned display means include lighting of a lamp, generation of an alarm sound, flashing of a lamp, continuation of an alarm sound, display using a meter, and the like.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

In FIG. 2A, 14 is a vehicle running on the road surface 1 in the direction of arrow A. A vehicle radar device is mounted inside the vehicle, and a horn-type radar antenna 16 is provided at the rear. radar antenna 16
As shown in FIG. 2A, the vertical beam angle θ ₁ is narrowed, and the beam center 17 is made to have a constant depression angle θ ₂ . The vertical beam angle θ ₁ and the depression angle θ ₂ are determined so as to satisfy a detection distance L, which will be described later. Note that the horizontal beam angle θ ₃ of the radar antenna 16 is widened as shown in FIG. 3 to prevent an undetectable area from occurring in the width direction of the road surface 1.

As shown in the block diagram of FIG. 2B, the radar apparatus is configured so that a transmission wave from a microwave CW oscillator 18 can be radiated from a radar antenna 16 via a circulator 20. When a transmitted wave is radiated toward a target object such as a vehicle, the reflected wave is transmitted to the antenna 1.
6 and is input to mixers 22 and 22' via circulator 20. The mixer 22' outputs the frequency difference between the transmitted wave and the received wave, that is, the relative speed signal output of the target object with respect to the vehicle.The relative speed is calculated by the counter 27 and displayed by the relative speed display device 24. If the Doppler frequency appearing at the mixer output terminal is Δf, the transmitted wave frequency is f, and the radio wave propagation velocity is C, the relative velocity is V.
is given by Δf=2V・f/C. The Doppler beat signals obtained by the mixers 22 and 22' always have a phase difference of π/2; when the target approaches, Bout advances by π/2 with respect to Aout, and conversely, when the target moves away, Bout advances with respect to Aout.
is delayed by π/2, so the relative movement direction, that is, the approach/departure direction, is determined by the phase difference detector 26 and the approach/departure signal S _AD is detected by the abnormal state determination device 28.
is input and judged. In addition, the counter 27
The relative speed signal Sv output from the vehicle 14 is inputted to the abnormal state determination device 28 together with the approach/departure signal S _AD , so that the abnormal state in which another vehicle or the like approaches the vehicle 14 is determined according to the degree of the abnormal state. The display lamp 30 and alarm sound generator 32 provide a step-by-step display. That is, when another vehicle 4 etc. approaches the vehicle 14, the indicator lamp 3 provided inside the vehicle 14
0 flashes, and at the same time the alarm sound generator 32 generates a continuous sound, and the time interval between the flashing of the lamp and the continuous sound changes in stages according to the relative speed with respect to the vehicle 4 etc. attitude. Note that the radar antenna 16 may be provided separately for transmission and reception.

In addition, in this embodiment, the Doppler beat signals obtained by the mixers 22 and 22' are sent to the amplifiers, respectively.
Via AMP, phase difference comparator 26, counter 2
7. and angular amplifier
In the APM, when the received signal level from the antenna 16 is low and the output signals from the mixers 22, 22' are low level, the signal is cut and the relative speed is calculated by the counter 27 and the phase difference detector A well-known range cut process is performed that prohibits the approach/departure determination operation by 26.

As described above _, in the vehicle radar device of this embodiment, as shown in FIG. 2A, the vertical beam angle θ ₁ of the radio waves emitted from the radar antenna 8 is set to The beam center 17 is made narrow so that the beam center 17 produces a constant depression angle θ ₂ . Therefore, even if there is a large vehicle 6 such as a bus on the road behind the vehicle 14, the radio waves will be reflected only at the bottom of the vehicle 6, and the radio wave reflecting surface will be similar to that of a passenger car. There is virtually no difference from the small vehicle 4.

As a result, the vehicle 4,
6, it becomes possible to detect the relative speed with respect to the vehicle and the direction of approach/departure.

Further, as shown in FIG. 2A, for example, after being reflected from the road surface, the radar antenna 8, such as the reflected waves of the radio waves 36 that hit the vehicles 4 and 6, directly hits a target on the road surface and is reflected. When a low-level radio wave other than a reflected wave is received, the well-known range cut processing by the amplifier AMP prohibits calculation of relative speed and judgment of approach/departure, so that the signal is detected within a predetermined detection distance L behind the vehicle 14. There is no possibility of erroneously recognizing a vehicle when there is no vehicle present.

Therefore, according to this embodiment, regardless of the size of the target object, it is possible to detect when the target object approaches within a certain distance behind the vehicle 14, improving the function of monitoring the rear of the radar device, and reducing the risk of a rear-end collision. can be avoided more reliably.
The detection distance L is normally set to 30 m, which allows for a certain margin for the braking distance of the following vehicle at a normal cruising speed. Note that the vertical beam angle θ ₁ is approximately 3 degrees, and the depression angle θ ₂ of the beam 17 is determined so as to satisfy the detection distance L described above.

Although the horn antenna 8 was used as the radar antenna in the above embodiment, a slot antenna 40 shown in FIG. 4 may be used instead. In order to narrow the vertical beam angle of the horn antenna 8, it is necessary to increase the height H shown in FIG. In terms of size, it is disadvantageous to mount it on a vehicle.
In the case of the slot antenna 40, in order to narrow the vertical beam angle, it is only necessary to increase the height H ₁ regardless of the depth L ₁ and the width W ₁ , so the weight does not increase so much and it is convenient for mounting on a vehicle. be.

The above has explained rear monitoring when a vehicle equipped with a radar device is moving forward, but it also covers monitoring of targets such as other vehicles and obstacles when the vehicle is moving backwards.
It is possible to monitor the rear to avoid collisions.

Furthermore, the radar device can be mounted not only at the rear of the vehicle but also at the front, thereby allowing the front of the vehicle to be monitored.

Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment in any way, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. .

[Effects of the Invention] As detailed above, in the vehicle radar device of the present invention, the vertical beam angle of the radar antenna is narrowed, and the entire continuous wave beam emitted from the radar antenna has an angle of depression. is,
The sensor is configured to be able to detect the presence of a target only when the distance of the target to the vehicle is within a predetermined distance. Therefore, according to the present invention, regardless of the size of the target, the presence of the target is detected for the first time when an object is detected within a predetermined distance from a vehicle equipped with the radar device. This makes it possible to keep the detection distance from the vehicle to the target almost constant, thereby enhancing the monitoring function to prevent dangers such as rear-end collisions and collisions.

[Brief explanation of the drawing]

FIG. 1 is a front view illustrating the operation of a conventional vehicle radar device. FIG. 2A is a front view illustrating the operation of a vehicle radar device including an embodiment of the present invention, FIG. 2B is a block diagram showing an outline of the embodiment, and FIG. A plan view showing the horizontal beam angle of the radar antenna, FIG. 4 is a perspective view of a slot antenna that can be used in place of the horn antenna of the same embodiment, and FIG. 5 is a perspective view of the horn antenna used in the above embodiment. It is. 1... Road surface, 2... Vehicle, 4, 6... Vehicle (target), 8, 16... Radar antenna, 40... Slot antenna (radar antenna).

Claims (1)

[Scope of Claims] 1. A continuous wave is emitted in the opposite direction or the same direction as the traveling direction of the vehicle, and the continuous wave directly hits a target object on the road surface and is reflected from the reflected wave. In a vehicle radar device configured to detect a relative speed and approach/departure direction to a target and display the detection results on a display means, the vertical beam angle of the radar antenna that emits the continuous wave is narrowed, and the The entire continuous wave beam produces an angle of depression, and the presence of the target is detected only when the distance of the target to the vehicle is within a predetermined distance.
A vehicle radar device characterized by being capable of detecting relative speed and approaching/departing directions.