JP2022053645A - On-vehicle radar device - Google Patents

Abstract

To make it possible to very simply determine that a front object is an automobile, with an on-vehicle radar, without using a machine learning model.SOLUTION: Detection waves irradiated forward from (an antenna 1 of) an on-vehicle radar in one's own vehicle V1 are reflected by a front vehicle V2, and are received with the antenna 1. It is determined that a front object is an automobile, when receiving second strong-receiving waves α2 within a predetermined time t4 after receiving first strong-receiving waves α1. It may also be determined that the front object is the automobile, under a condition that third strong-receiving waves α3 are received within the predetermined time t4 with a delay from the second strong-receiving waves α2.SELECTED DRAWING: Figure 3

Description

The present invention relates to an in-vehicle radar device capable of determining that an object in front is an automobile.

In recent vehicles, it is common to mount a radar for control in various in-vehicle devices such as automatic brake control, follow-up constant speed running control, and headlamp irradiation range control.

In-vehicle radar for detecting a front obstacle usually detects the distance to the front obstacle exclusively, and identifies what kind of object the front obstacle is (for example, a vehicle or a pedestrian). It is common to use an in-vehicle camera to identify).

On the other hand, Patent Document 1 discloses a technique of detecting that an obstacle in front is a vehicle by a radar by using a machine learning model.

Japanese Unexamined Patent Publication No. 2020-16597

By the way, the discriminating ability of the in-vehicle camera is significantly reduced in a dark environment such as at night. Then, in order to improve the discrimination ability in a dark environment, it is necessary to use an expensive camera such as an infrared camera.

On the other hand, the in-vehicle radar has excellent detection performance even at night when the surrounding environment is dark. Therefore, it is extremely preferable to enable the identification of the vehicle by the in-vehicle radar.

The one described in Patent Document 1, which identifies a vehicle by an in-vehicle radar, requires a large amount of time for learning because it uses a machine learning model, and also puts a heavy burden on the control system.

The present invention has been made in consideration of the above circumstances, and the purpose of the present invention is to provide an in-vehicle radar that makes it extremely easy to determine that the object in front is an automobile without using a machine learning model. To provide.

In the present invention, basically, when the front object existing in front of the own vehicle is a vehicle (preceding vehicle) traveling in the same direction as the own vehicle, the received wave received by the in-vehicle radar of the own vehicle is received. It was made based on the knowledge that it shows a peculiar reception situation.

That is, the automobile has a pair of left and right side mirrors and a vehicle body having a large surface area (particularly, a pair of left and right side surface portions). When there is a vehicle traveling in the same direction as the own vehicle in front of the own vehicle, the first strong reception wave and the second strong reception wave are sequentially received as the received waves received by the in-vehicle radar of the own vehicle. , The third strong reception wave will also be received with a further delay. In the present invention, it is determined whether or not the object in front is an automobile by analyzing such a reception situation.

Specifically, the following solution method is adopted in the present invention.

An in-vehicle radar device that acquires the distance to an object based on the delay time until the detection wave transmitted toward the front of the own vehicle is received as a reflected wave from an object existing in front of the own vehicle. And
The reception status acquisition means for acquiring the reception status of the detection wave,
Based on the reception status acquired by the reception status acquisition means, when the second strong reception wave is received within a predetermined time from the reception of the first strong reception wave, it is determined that the object is an automobile. Have the means,
It is done like this. According to the above solution method, it is possible to determine whether or not the object in front is an automobile very easily without using a machine learning model.

The preferred embodiment based on the above solution method is as follows.

The determination means may determine that the object is an automobile, provided that the third strong reception wave is received later than the second strong reception wave within the predetermined time. can. In this case, it is possible to more reliably (accurately) determine whether or not the object in front is an automobile.

The determination means may determine the size of the automobile based on the time difference between the time when the first strong reception wave is received and the time when the second strong reception wave is received. can. In this case, the size of the automobile can be easily determined.

In the determination means, when the time difference between the time when the first strong reception wave is received and the time when the second strong reception wave is received is less than a preset predetermined value, the object in front of the determination means It can be forbidden to determine that it is a car. In this case, it is preferable in preventing a situation in which the vehicle is erroneously determined to be an automobile.

The first strong received wave corresponds to the received wave of the reflected wave from the rear surface of the vehicle in front traveling in the same direction as the own vehicle.
The second strong received wave corresponds to the received wave of the reflected wave from the side mirror of the vehicle in front traveling in the same direction as the own vehicle.
The third strong received wave corresponds to the received wave of the diffracted wave due to the diffraction in front of the vehicle in front traveling in the same direction as the own vehicle.
Can be done. In this case, what the first strong reception wave to the third strong reception wave are is specifically specified.

According to the present invention, it is possible to determine that the front object is an automobile very easily without using a machine learning model.

The figure which shows the situation which irradiates the detection wave from the radar mounted on the own vehicle toward the vehicle in front. The figure which shows the state which the 1st strong reflection to the 3rd strong reflection which becomes a strong reception wave are generated based on the presence of an automobile in front. The figure which shows the reception situation of the received wave when the car is in front. The flowchart which shows the control example of this invention.

In FIG. 1, the own vehicle is represented by V1. The own vehicle V1 is equipped with an in-vehicle radar, its antenna is indicated by reference numeral 1, and its controller (control unit) is indicated by reference numeral U. Further, a front vehicle (automobile in FIG. 1) existing in front of the own vehicle V1 and traveling in the same direction as the own vehicle V1 is indicated by reference numeral V2.

The detection wave transmitted (irradiated) from the antenna 1 is reflected by the vehicle V2 in front and received by the antenna 1. By substituting the delay time from the transmission of the detection wave to the reception by the antenna 1 into a predetermined calculation formula set in the vehicle-mounted radar, the distance to the vehicle in front V2 is calculated. If the delay time is the same, the calculated distance is the same regardless of the difference in the radar method and its internal model.

The in-vehicle radar (controller U) mounted on the own vehicle V1 is designed to determine whether or not the object in front is an automobile. This determination is made by analyzing the received wave to see if it is a peculiar reception situation that occurs when the object in front is an automobile.

FIG. 2 shows a situation in which the front vehicle V2 is an automobile and is traveling in the same direction as the own vehicle V1, and the detection wave radiated forward from the antenna 1 of the own vehicle V1 is reflected by the front vehicle V2 to be an antenna. It schematically shows how to return to 1.

Since the front vehicle V2 is an automobile, it has a pair of left and right side mirrors 21 and a vehicle body (particularly a side surface portion) having a large surface area. The received waves returned from the vehicle V2 in front and received by the antenna 1 include the first strong received wave based on the first strong reflection, the second strong received wave based on the second strong reflection, and the third received wave based on the third strong reflection. As a result of verification, it was confirmed that there are three types of strong received waves.

The first strong reflection is a reflection on the rear surface of the vehicle V2 and is received as the first strong reception wave.

The second strong reflection is the reflection by the side mirror 21, but it does not return to the antenna 1 linearly, but returns to the antenna 1 along the vehicle body (particularly the side surface portion) of the vehicle V2 in front. It is received as the second strong receive wave.

The third strong reflection is diffraction in front of the vehicle V2 in front, and does not return linearly toward the vehicle V1 but returns to the antenna 1 along the vehicle body (particularly the side surface) of the vehicle V2 in front. And is received as the third strong receive wave.

By the way, it was confirmed that the second strong reflection and the third strong reflection do not occur because the motorcycle and the bicycle also have a pair of left and right side mirrors but do not have a vehicle body having a large surface area.

FIG. 3 is a time chart showing the relationship between the delay time from the transmission of the detected wave to the reception and the reception intensity of the received wave. The delay time corresponds to the distance, and the larger the delay time, the larger the distance. That is, since the delay time is the round-trip time of the detection wave, the distance is calculated by multiplying the half time of the delay time by the propagation speed of the detection wave.

In FIG. 3, the first strong reception wave corresponding to the first strong reflection is indicated by the reference numeral α1, the second strong reception wave corresponding to the second strong reflection is indicated by the reference numeral α2, and the second strong reception wave corresponds to the third strong reflection. The third strong received wave is indicated by reference numeral α3.

In FIG. 3, t4 is a predetermined time as a threshold value. The predetermined time t4 is set as a time corresponding to a length slightly larger than the length in the front-rear direction of a commercially available large vehicle (for example, a truck or a bus). Specifically, the predetermined time t4 is set to correspond to a distance of about 20 m, but it is a distance corresponding to the maximum length of a large vehicle actually running (commercially available). The time t4 may be set so as to be.

Further, T1 to T3 each indicate a time difference. The time difference T1 is the time difference between the time when the first strong received wave α1 is detected and the time when the third strong received wave α3 is detected. The time difference T2 is the time difference between the time when the first strong reception wave α1 is detected and the time when the second strong reception wave α2 is detected. The time difference T3 indicates the time difference between the time when the second strong reception wave α2 is detected and the time when the third strong reception wave α3 is detected. T1 = T2 + T3.

The time difference T2 can be considered as a value indicating the distance from the rear surface of the front vehicle V2 to the side mirror 21. Therefore, by observing the size of this time difference T2, it is possible to estimate the size (length in the front-rear direction) of the vehicle in front V2. For example, it is possible to distinguish between a small vehicle, a medium-sized vehicle, and a large-sized vehicle according to the distance corresponding to the time difference T2. When the time difference T2 is too small or too large, it is highly possible that the vehicle in front V2 is not a vehicle.

Next, referring to the flowchart shown in FIG. A control example for determining whether or not the front object is an automobile by the controller U of the in-vehicle radar will be described. In the control example shown in FIG. 4, in addition to the threshold value t4 which is a predetermined time, a plurality of times t1 to t3 as a threshold value are set in order to determine the size of the automobile. t1 <t2 <t3 <t4. The time t1 corresponds to a distance of about 1.5 m. t2 corresponds to a distance of about 4 m. t3 corresponds to a distance of about 7 m.

On the premise of the above, first, the detection wave is received in Q1. After that, in Q2, the reception status is analyzed (corresponding to the creation of a time chart as shown in FIG. 3).

After Q2, it is determined in Q3 whether or not the first to third strong received waves α1 to α3 corresponding to the first strong reflection to the third strong reflection are received. The strong received wave is assumed to have a reception level of a predetermined value or higher. If YES in the determination of Q3, is the time difference T1 between the time when the first strong received wave α1 is detected and the time when the third strong received wave α3 is detected in Q4 smaller than the predetermined time t4? Whether or not it is determined.

If YES in the determination of Q4, it means that the object in front is determined to be an automobile. After that, the size (length in the front-rear direction) of the automobile is determined by the processing of Q5 to Q9. That is, in Q5, it is determined whether or not the time difference T2 between the detection time of the first strong reception wave α1 and the detection time of the second strong reception wave α2 is t1 or more and less than t2. If YES in the determination of Q5, it is determined that the object in front is a small automobile.

If NO in the determination of Q5, it is determined in Q7 whether or not T2 is t2 or more and less than t3. If YES in the determination of Q7, it is determined in Q8 that the object in front is a medium-sized automobile. If NO in the determination of Q7, it is determined in Q9 that the object in front is a large automobile.

The determination results in Q6, Q8, and Q9 are displayed, for example, on the display 2 (see FIG. 1) set at a position easily visible to the driver of the own vehicle V1. The driver of the own vehicle V1 can see the display contents displayed on the display 2 and pay attention to the overtaking of the vehicle in front and the like.

If the determination in Q3 is NO, or if the determination in Q4 is NO, the process is terminated as it is (the determination that the object in front is an automobile is not performed).

Although the embodiments have been described above, the present invention is not limited to the embodiments, and appropriate modifications can be made within the scope of the claims. For example, when it is determined that the vehicle is a car, the size may be distinguished by two or four or more types, or the size may not be determined. It may be determined whether or not the vehicle is an automobile based on the first strong reception wave α1 and the second strong reception wave α (the third strong reception wave α3 is ignored). That is, when the first strong reception wave α1 and the second strong reception wave α2 are detected within the predetermined time t4, it can be determined that the front object is an automobile.

In the control example shown in FIG. 4, after confirming the existence of the first strong reception wave α1 to the third strong reception wave α3, it is determined whether or not the three strong reception waves α1 to α3 are detected within the predetermined time t4. I try to distinguish. On the contrary, it is confirmed whether or not the second strong reception wave α2 and the third strong reception wave α3 are detected within the predetermined time t4 from the time when the first strong reception wave α1 is received as the start time. You may try to do it. The size determination of the automobile can also be determined based on the time difference from the detection time of the first strong reception wave α1 to the detection of the third strong reception wave α3. Of course, the object of the present invention is not limited to what is specified, but also implicitly includes providing what is expressed as substantially preferable or advantageous.

According to the present invention, it is possible to determine whether or not the front object is an automobile by using an in-vehicle radar.

V1: Own vehicle V2: Front vehicle 1: Antenna (own vehicle)
U: Controller (own vehicle)
2: Display (own vehicle)
21: Side mirror (vehicle in front)

Claims (5)

An in-vehicle radar device that acquires the distance to an object based on the delay time until the detection wave transmitted toward the front of the own vehicle is received as a reflected wave from an object existing in front of the own vehicle. And
The reception status acquisition means for acquiring the reception status of the detection wave,
Based on the reception status acquired by the reception status acquisition means, when the second strong reception wave is received within a predetermined time from the reception of the first strong reception wave, it is determined that the object is an automobile. Have the means,
An in-vehicle radar device characterized by this. In claim 1,
The determination means is characterized in that the object is determined to be an automobile on condition that the third strong reception wave is received later than the second strong reception wave within the predetermined time. In-vehicle radar device. In claim 1 or 2,
The determination means is characterized in that the size of an automobile is determined based on the time difference between the time when the first strong reception wave is received and the time when the second strong reception wave is received. In-vehicle radar device. In any one of claims 1 to 3,
In the determination means, when the time difference between the time when the first strong reception wave is received and the time when the second strong reception wave is received is less than a preset predetermined value, the object in front of the determination means An in-vehicle radar device characterized in that it is prohibited to determine that it is an automobile. In claim 2,
The first strong received wave corresponds to the received wave of the reflected wave from the rear surface of the vehicle in front traveling in the same direction as the own vehicle.
The second strong received wave corresponds to the received wave of the reflected wave from the side mirror of the vehicle in front traveling in the same direction as the own vehicle.
The third strong received wave corresponds to the received wave of the diffracted wave due to the diffraction in front of the vehicle in front traveling in the same direction as the own vehicle.
An in-vehicle radar device characterized by this.

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