JP3608991B2 - Inter-vehicle distance sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inter-vehicle distance sensor that is mounted on a vehicle and detects a relative distance to a target.
[0002]
[Prior art]
Conventionally, an inter-vehicle distance sensor using a millimeter wave radar for detecting a target such as a preceding vehicle is mounted on the vehicle, and the detection output is used for an automatic travel control system (ACC) or the like. This inter-vehicle distance sensor detects the relative distance, relative speed, etc. of the target by irradiating millimeter waves toward the front of the vehicle, receiving the reflected waves from the target, and mixing the received signal with the transmission signal. Was.
[0003]
[Problems to be solved by the invention]
The reason why a conventional inter-vehicle distance sensor detects a ghost will be described with reference to FIG.
In a conventional inter-vehicle distance sensor using a millimeter wave radar, if the radio wave 12 reflected by the preceding vehicle 11 is reflected by a wall 13 such as a tunnel wall or a soundproof wall, an error occurs as if a ghost 14 is traveling through the wall. I sometimes recognized it. In order to prevent this erroneous recognition, the conventional inter-vehicle distance sensor responds by recognizing only the vehicle traveling in front of the host vehicle 15. However, even when such measures are taken, a ghost may be erroneously recognized as a vehicle traveling in front of the host vehicle on a curved road or the like.
[0004]
It is an object of the present invention to obtain an inter-vehicle distance sensor that can prevent a ghost from being erroneously recognized as an actual target.
[0005]
[Means for Solving the Problems]
The present invention has been made to achieve the above object. The present invention provides an inter-vehicle distance sensor that is mounted on a vehicle and detects a relative distance from a target, and a basic line based on the actual line and means for calculating an actual line constituted by a stationary object from the detected target. And means for determining whether the detected target is inside or outside the basic line, and erasing the target outside, the means for calculating the basic line comprises: The actual line is compared with the previous basic line, and a new basic line is calculated by learning .
[0006]
When the vehicle travels along a stationary object such as a wall, the inter-vehicle distance sensor calculates the actual line composed of continuous stationary objects from the detected targets and calculates the basic line based on this. To do. Then, what is outside the basic line is determined to be a ghost and is erased. As a result, it is possible to prevent a ghost generated by the reflection of radio waves from being erroneously recognized as an actual target.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
A millimeter wave radar inter-vehicle distance sensor to which the present invention is applied will be described with reference to the drawings.
FIG. 2 shows a circuit configuration of the inter-vehicle distance sensor 21.
The transmitter 22 irradiates the millimeter wave signal modulated into the ramp waveform from the transmission antenna 23. Radio waves emitted from the transmitting antenna 23 at a predetermined beam angle are reflected by the target when a target such as a preceding vehicle exists. The receiving antenna 24 receives the radio wave reflected by the target. The received signal is mixed with the local oscillation signal from the transmitter 22 by the mixer 25 and input to the digital signal processor 30 via the filter 26, amplifier 27, auto gain controller 28, and A / D converter 29. The
[0008]
In the digital signal processor 30, the FFT processing unit 31, the frequency analysis unit 32, and the signal processing unit 33 calculate the relative distance, relative speed, and lateral position for each target. Since these configurations and operations are not different from those of the conventional inter-vehicle distance sensor, detailed description thereof is omitted. The calculation result of the inter-vehicle distance sensor 21 is output to the ACC device (automatic travel control device) 34. The ACC device 34 performs automatic travel control based on each target information acquired from the inter-vehicle distance sensor 21.
[0009]
An example of a method for identifying a ghost will be described with reference to FIGS.
As shown in FIG. 3, the own vehicle 15 is traveling on a straight lane along a wall 13 such as a tunnel wall or a soundproof wall, and the preceding vehicle 11 is present on the same traveling lane ahead. Suppose that At this time, as described with reference to FIG. 1, the inter-vehicle distance sensor 21 detects the ghost 14 not only on the preceding vehicle 11 but also on the outside of the wall 13 as a target by signal analysis. At the same time, the protrusions 41, 42, 43 fixed to the wall 13 are detected as stationary objects.
[0010]
FIG. 4 illustrates the relative distance and lateral position of each target calculated by the inter-vehicle distance sensor 21 in the state of FIG.
The preceding vehicle 11 in front of the host vehicle 15 is detected at the position 0 in the lateral direction. The protrusions 41, 42, and 43 on the wall 13 are detected as stationary objects (relative speed = vehicle speed). A line formed by the protrusions 41, 42, and 43 detected continuously is set as an actual line 44.
[0011]
When the ghost 14 is detected by reflecting the radio wave on the wall 13, the lateral position of the ghost 14 is outside the actual line 44. Therefore, the target detected outside the actual line 44 can be determined as the ghost 14, and the target information is not output to the ACC device 34.
In the example described above, the target outside the actual line 44 is determined as the ghost 14. However, if a stationary object such as a sign is determined to be the actual line 44, there is a possibility that a vehicle actually traveling in the adjacent lane is erroneously determined as a ghost. In order to prevent such a situation, the basic line 45 is used as a reference for determining a ghost. The above example is an example in which the basic line 45 is matched with the actual line 44, and the present invention includes this example in the technical scope.
[0012]
Next, a specific example of a ghost determination method using the basic line 45 will be described below.
1. A line 46 for one lane is set as the width of the own vehicle travel lane. In addition, the width for one lane is set on both sides from the vehicle lane. The line that determines the width of the total three lanes is the maximum value 47 of the basic line.
[0013]
2. Among the stationary object targets detected by the millimeter wave radar, information on stationary object targets existing outside the line 46 of the own vehicle traveling lane is collected.
3. An actual line 44 is calculated from the collected lateral position of the stationary object target. At this time, the actual line 44 is calculated only when three or more stationary object targets are detected, and when it is less than that, the actual line 44 is not calculated, so that the sign that appears accidentally appears. It is possible to prevent erroneous recognition of stationary objects such as walls. In addition, as a method of determining the horizontal position of the line, there are a method of averaging the horizontal positions of the respective targets, a method of setting a target having the smallest horizontal position (the innermost target), and the like.
[0014]
4). Learning is performed by comparing the actual line 44 with the previous basic line 45 to determine a new basic line 45. Here, the previous basic line is a basic line that has been updated by the processing of the signal processing unit 33 until the previous time. Note that the maximum value 47 of the basic line described above is set as the default value of the basic line.
When the actual line 44 is inside the basic line 45, the basic line is learned inward. For example, a new basic line is set inward by a certain value from the currently stored basic line 45. Alternatively, a new basic line 45 is set inward by a value proportional to the difference between the actual line 44 and the basic line 45.
[0015]
Thus, by setting a new basic line 45 by learning, the basic line 45 is not significantly changed by a stationary object that appears in fragments, and an actual vehicle or the like may be erroneously determined as a ghost. Disappear. If the stationary object is a continuous object such as a wall, the basic line 45 approaches the actual line 44.
Also, when the actual line 44 is outside the basic line 45, the basic line 45 is learned outward as in the case of the inside. However, if the new basic line 45 is outside the maximum value 47 of the basic line, the basic line 45 is held at the maximum value 47, and a new basic line 45 is set further outside. do not do.
[0016]
The operation of the signal processing unit 33 that realizes the processing described above will be described with reference to the flowchart of FIG.
Similar to a normal inter-vehicle distance sensor, information such as a relative distance, a relative speed, and a beam angle is obtained for each target in the processing up to step S11.
In step S12, it is determined whether or not there is a target with a high relative speed outside the line 46 of the host vehicle lane stored in advance. Here, if there is a high relative speed target, that is, a stationary object, the process proceeds to step S14, and if not, the process proceeds to step S13.
[0017]
In step S13, it is determined whether or not there is a target whose distance derivative is equal to the relative speed. Here the distance differential advances to step S14 if the target, such as equal target, i.e. guardrail and the relative speed, the process proceeds to step S 20 to be equal.
In step S14, since the protrusions 41 to 43 from the wall or the guard rail is detected as a target, the actual line 44 is calculated from the lateral position of the target.
[0018]
In step S15, it is determined whether the actual line 44 is inside or outside the previous basic line 45. Here, if it is inside, in step S16, the previous basic line shifted inward by learning is set as a new basic line 45. If it is outside, in step S17, a new basic line 45 is set by shifting the basic line outward by a constant value or a proportional value by learning.
[0019]
When learning to the outside of step S17 is completed, it is determined in step S18 whether or not the new basic line 45 is outside the maximum value 47 stored in advance. Here, if it is not outside, the process proceeds to step S20, but if it is outside, that is, if the obtained basic line is outside the front three lanes, the stored maximum value 47 is set to a new basic line 45 in step S19. Set as. Thereby, the basic line 45 does not spread from the front three lanes.
[0020]
In step S <b> 20, the basic line 45 is newly set by detecting a stationary object, or remains unchanged without detecting a stationary object. In step S <b> 20, it is determined whether targets other than those recognized as the actual line 44 are inside or outside the basic line 45. If the target is inside the basic line 45, the target is determined as a target to be recognized in step S21. If it is outside, in step S22, the target is regarded as a ghost and is erased.
[0021]
After step S22, the target information is output to the ACC device 34, and the process returns to processing such as FFT processing and frequency analysis.
[0022]
【The invention's effect】
According to the present invention, it is possible to prevent a ghost from being erroneously recognized as an actual target in the inter-vehicle distance sensor.
[Brief description of the drawings]
FIG. 1 is a diagram showing a reason why a ghost is detected in a conventional inter-vehicle distance sensor.
FIG. 2 is a diagram showing a circuit configuration of an inter-vehicle distance sensor to which the present invention is applied.
FIG. 3 is a diagram showing a situation where an inter-vehicle distance sensor of the present invention is placed.
4 is a diagram showing target information in the situation of FIG. 3;
FIG. 5 is a flowchart showing processing in the signal processing unit of FIG. 2;
[Explanation of symbols]
11 ... preceding vehicle 12 ... radio wave 13 ... wall 14 ... ghost 15 ... own vehicle 21 ... inter-vehicle distance sensor 22 ... transmission device 23 ... transmission antenna 24 ... reception antenna 25 ... mixer 26 ... filter 27 ... amplifier 28 ... auto gain controller 29 ... A / D converter 30 ... Digital signal processor 31 ... FFT processor 32 ... Frequency analyzer 33 ... Signal processor 34 ... ACC devices 41, 42, 43 ... Projections 44 ... Actual line 45 ... Basic line 46 ... 1 Line 47 for lanes ... Maximum value of basic line

Claims (4)

In the inter-vehicle distance sensor that is mounted on the vehicle and detects the relative distance to the target,
Means for calculating an actual line composed of stationary objects from the detected target;
Means for calculating a basic line based on the actual line;
Means for determining whether the detected target is inside or outside the basic line, and erasing the target located outside ;
The inter-vehicle distance sensor characterized in that the means for calculating the basic line compares the actual line with a previous basic line and calculates a new basic line by learning . Means for calculating the actual line, the target detected as stationary horizontal average value in a direction positions are calculated, according to claim 1, lateral position of the averaged lateral position of the actual line Inter-vehicle distance sensor. 2. The inter-vehicle distance sensor according to claim 1 , wherein the means for calculating the actual line sets a lateral position of the innermost target among the targets detected as stationary objects as a lateral position of the actual line . Means for calculating the basic line, when the maximum value is greater than the lateral position of the new base line are determined in advance, according to claim 1 to 3 for holding the maximum value as the lateral position of the new base line The inter-vehicle distance sensor according to any one of the above.

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