JP2014164492A - Block line recognition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately recognize a block line having a special color which is different from a color usually used.SOLUTION: A block line recognition device recognizes a block line on the basis of a gray scale image acquired by converting a road surface image picked up by a camera. When an own vehicle enters a provisional two-lane road where a yellow block line (yellow line) is used (S105:Yes), the recognition accuracy of a yellow line is enhanced (S115). Concretely, in consideration of higher brightness of R in such a yellow line area in a road surface image, the device converts the surface road image into a gray scale image in a state in which the brightness of R is weighed and reduces an edge threshold in extraction of an edge point so as to allow a yellow line to be easily extracted, which improves the recognition accuracy of the yellow line.

Description

  The present invention relates to a lane marking recognition device for recognizing a lane marking based on an image of a road surface.

  2. Description of the Related Art Conventionally, there has been known an apparatus that recognizes a lane line from a road surface image obtained by photographing a road surface in front of the host vehicle and performs driving support based on the recognition result. As an example, the travel path recognition apparatus described in Patent Document 1 stores a composite line pattern composed of a plurality of lane markings in advance, and compares the pattern with the pattern to determine the type of the composite line. Recognize correctly.

Japanese Patent No. 4207935

  By the way, white roads (white lane markings) are usually used on roads in many countries, but for example, provisional two-lane roads (hereinafter simply referred to as provisional two-lane roads) where two-way traffic is used A composite line composed of yellow lines (yellow to orange partition lines) is used as the center line. Yellow lines are also used in carpool lanes in the United States and construction sections in Europe.

  A provisional two-lane road is a road that was planned as a road with four or more lanes, but only two lanes were provisionally opened. In this case, the lane is allowed to run.

  And since the yellow line has a lower contrast with the road surface than the white line, it is difficult to extract the edge from the road image, so the accuracy of detecting the yellow line and the type of the yellow line (whether it is a solid line or a broken line) ) Is reduced, and the yellow line cannot be accurately recognized.

  This invention is made | formed in view of the said subject, and it aims at providing the lane marking recognition apparatus which can recognize the lane marking of the specific color different from the color normally used accurately.

  The lane marking recognition apparatus according to claim 1 made in view of the above-described problem is to capture a road surface in front of the host vehicle and generate a road surface image that is a color image, and a predetermined scanning line. And extracting means for detecting the edge of the lane marking drawn on the road surface by detecting a change in the color of the road surface image and comparing the degree of the change with a predetermined edge threshold value.

  The lane marking recognition device is generally used as a lane marking color, with a recognition section for recognizing a lane marking based on the edge extracted by the extraction section, and a road surface area in which no lane marking is drawn on the road surface. Road judging means for judging whether or not the host vehicle is traveling on a specific road using a specific color lane marking whose degree of color change with respect to the road surface area is smaller than the normal color.

Then, when the road determination unit determines that the host vehicle is traveling on the specific road, the extraction unit improves the extraction sensitivity, which is a sensitivity when extracting the edge of the specific color lane marking.
According to such a configuration, when the host vehicle is traveling on a specific road, the edge of the specific color of the lane marking is easily extracted from the road surface image. The accuracy of determining the line type can be improved. For this reason, the partition line of a specific color can be recognized with high accuracy.

  As already mentioned, the white line is usually used on roads in many countries, but the yellow line is used on provisional two-lane roads in Japan, carpool lanes in the United States, construction sections in Europe, and the like.

Therefore, in the lane marking recognition apparatus according to the second aspect, the normal color is white and the specific color is yellow or orange.
According to such a configuration, when the host vehicle is traveling on a provisional two-lane road or the like, the yellow line can be accurately recognized.

  In particular, as described above, a composite line composed of a yellow line and a white line is used as the center line of the provisional two-lane road. However, since the yellow line can be accurately recognized by the above configuration, such a composite line is used. It becomes possible to recognize correctly.

  In many cases, rubber poles and concrete blocks are installed on the center line of the provisional two-lane road. In such cases, the maintenance of the composite line is not sufficient, and the yellow line is faded. There may be. On the other hand, according to the above configuration, since the edge of the yellow line is easily extracted, even a yellow line in a faint state can be accurately recognized.

It is a block diagram which shows the structure of a lane marking recognition apparatus. It is a flowchart of a lane marking recognition process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment of the present invention is not limited to the following embodiment, and can take various forms as long as they belong to the technical scope of the present invention.

[Description of configuration]
The in-vehicle lane marking recognition device 10 of the present embodiment is configured to issue a lane departure warning to a driver, and includes a camera 11, a buzzer 12, a communication unit 13, a control unit 14, and the like (see FIG. 1). The lane marking recognition device 10 includes a rain sensor 15 that detects the amount of rainfall, a vehicle speed sensor 16 that detects the vehicle speed of the host vehicle, a yaw rate sensor 17 that detects the yaw rate of the host vehicle, and the like.

The control unit 14 includes a CPU, a ROM, a RAM, an I / O, and the like, and is a part that performs overall control of the lane marking recognition apparatus 10 according to a program stored in the ROM.
The camera 11 is configured as a CCD camera, an infrared camera, or the like, and captures a road surface around the host vehicle or ahead and generates a road image that is a color image.

The buzzer 12 is a part that emits various warning sounds in response to instructions from the control unit 14.
Moreover, the communication part 13 is a site | part which communicates with other ECU via in-vehicle LAN which is not shown in figure.

[Description of operation]
(1) Outline The lane marking recognition device 10 of the present embodiment performs edge extraction from the road surface image generated by the camera 11, detects the lane marking of the road that is running based on the extraction result, and The division line is recognized by determining the type (whether it is a solid line or a broken line).

  In addition, it is good also as a structure which recognizes a division line only by detecting a division line. In addition, the lane marking recognition device 10 further recognizes the type of the composite line based on the recognition result of the lane line when the traveling road is provided with a composite line composed of a plurality of lane markings. Also good.

  Further, the lane marking recognition device 10 predicts the travel locus of the host vehicle based on the amount of rainfall detected by the rain sensor 15, the vehicle speed detected by the vehicle speed sensor 16, the yaw rate detected by the yaw rate sensor 17, and the like. .

  Then, the lane marking recognition device 10 grasps the lane that the host vehicle should travel from the recognition result of the lane marking or the composite line, and determines that the host vehicle has a risk of departing from the lane, the buzzer 12 A warning sound is emitted and a lane departure warning is given. In addition, when there exists a danger that the own vehicle will deviate from a lane, it is good also as a structure which corrects the course of the own vehicle by performing steering assistance and avoids the departure from a lane.

  More specifically, the control unit 14 of the lane marking recognition device 10 converts the road surface image into a grayscale image. At this time, the control unit 14 calculates the average value of the luminance of each color component of R, G, B for each pixel of the road surface image, and in accordance with the average value, the luminance of each pixel in the grayscale image (gradation level) ) May be determined.

  Thereafter, the control unit 14 sets a plurality of horizontal scanning lines in the grayscale image, compares the luminance of each pixel adjacent along the scanning line, and determines a difference between the luminances in advance. A point that has reached the threshold is extracted as an edge point of the lane marking.

  It should be noted that the direction of the scanning line is not limited to the horizontal direction. Further, the control unit 14 may compare not only the adjacent pixels but also, for example, the luminance of pixels arranged at a predetermined interval along the scanning line.

  Then, the control unit 14 detects the straight line by performing the Hough transform on the edge points, and selects a straight line candidate having a large number of votes for the Hough transform from these straight lines, and further narrows down the lane line candidates. Thus, a lane line candidate to be detected as a lane line is determined.

  Specifically, the control unit 14 may narrow down the lane line candidates based on the contrast or brightness difference between the lane line candidates and an area (road surface area) where no lane line is drawn on the road surface. It is also possible to narrow down in consideration of various characteristics such as line thickness and total extension distance. Moreover, the control part 14 may narrow down considering the distance of the horizontal direction from the center of the own vehicle to a lane marking candidate.

  Also, the lane marking recognition apparatus 10 determines the type of the lane marking based on the number of edge points extracted for the detected lane marking. Specifically, when the number of edge points has reached the determination threshold, the type of lane marking is determined to be a solid line, and when the number of edges has not reached the determination threshold, the lane marking Is determined to be a broken line.

  Here, in Japan and the like, a white lane line (white line) is usually used. Orange demarcation lines (yellow lines) are used.

  When this yellow line is photographed, the yellow line has a higher R luminance than the white line, but the G and B luminances are lower, and the B luminance is lower than the road surface area. For this reason, the yellow line has a lower contrast to the road surface region than the white line, and it is difficult to extract the edge, and as a result, the accuracy of recognizing the yellow line is lowered.

  Therefore, the lane marking recognition device 10 according to the present embodiment improves the extraction sensitivity of yellow line edge points while traveling on roads (yellow line roads) where yellow lines are used (yellow line edge points are extracted). Make it easier).

  Further, since it becomes difficult to extract the edge point of the yellow line, when determining the type of the yellow line, there is a high possibility that the yellow line which is a solid line is erroneously determined as a broken line. For this reason, the lane marking recognition device 10 of the present embodiment determines the type of yellow line by making it easier to determine that the lane line is a solid line (improves the determination sensitivity of the solid line) while traveling on the yellow line road. Improve accuracy.

As a result, the accuracy of recognizing the yellow line is improved, and as a result, the type of the composite line including the yellow line can be accurately recognized, and a more appropriate lane departure warning can be performed.
(2) About lane marking recognition processing Next, lane marking recognition processing for recognizing the lane marking drawn on the road surface in front of the host vehicle will be described with reference to the flowchart shown in FIG. This process is periodically executed by the control unit 14 of the lane marking recognition device 10.

  In S100, the control unit 14 determines whether the yellow line edge point extraction sensitivity is improved, and if an affirmative determination is obtained (S100: Yes), the process proceeds to S125. When a negative determination is obtained (S100: No), the process proceeds to S105.

  In S105, the control unit 14 determines whether or not the host vehicle has entered the yellow road, and if an affirmative determination is obtained (S105: Yes), the process proceeds to S110 and a negative determination is made. If it is obtained (S105: No), the process proceeds to S145.

  Specifically, for example, the control unit 14 analyzes a color road surface image photographed by the camera 11, and on the road surface in front of the host vehicle, a yellow line (or a certain length along the traveling direction of the host vehicle) (or It may be determined whether or not a composite line including a yellow line is drawn. And the control part 14 may determine with the own vehicle having started the driving | running | working of the yellow line road, when such a yellow line is drawn.

In addition, it is known that the yellow line is used on provisional two-lane roads in Japan, car pool lanes in the United States, construction sections in Europe, and the like.
Therefore, the control unit 14 communicates with an ECU such as a navigation device (not shown) via the communication unit 13 to acquire the type information of the road on which the host vehicle is traveling, and determines the type of the road. good. The type information may be stored, for example, in map data included in the navigation device, or may be information acquired from the outside via a radio beacon or the like.

And the control part 14 may determine with the own vehicle having started the driving | running | working of the yellow road, when the road where the own vehicle is driving | running | working is the temporary 2-lane road mentioned above.
In S110, the control unit 14 shifts to the yellow line mode and improves the extraction sensitivity of the yellow line edge point (S115).

  Specifically, the control unit 14 may set the edge threshold for extracting the edge of the lane marking from the road surface image as a yellow line mode threshold smaller than the normal mode threshold. This makes it easier to extract the edges of all lane markings regardless of the color, so that the sensitivity of extracting yellow line edge points is improved, and consequently the accuracy of recognizing yellow lines is improved. .

  Further, as described above, the yellow line on the road surface image has a higher luminance of R than the white line. Focusing on this point, the control unit 14 weights the R luminance of each pixel during the yellow line mode (for example, a state in which the R luminance of each pixel is multiplied by a coefficient larger than 1). Thus, the road surface image may be converted into a gray scale image.

  By doing so, the contrast of the yellow line with respect to the road surface region on the gray scale image is increased, so that the sensitivity of extracting the edge point of the yellow line is improved, and consequently the accuracy of recognizing the yellow line is improved.

  In addition, it is good also as a structure which performs only one of the fall of an edge threshold value, and the weighting of the luminance of R. Even in such a case, the extraction sensitivity of the yellow line edge point can be improved.

  In subsequent S120, the control unit 14 improves the determination sensitivity of the solid line by setting the determination threshold used for determining the type of the lane marking to a yellow line mode threshold that is smaller than the normal mode threshold (the lane marking). Is easily determined as a solid line), and the process proceeds to S145. Thereby, it can prevent that the yellow line which is a solid line is misjudged as a broken line, and can improve the precision which recognizes a yellow line.

Note that, when the mode is shifted to the yellow line mode, only the yellow line edge point extraction sensitivity may be improved without improving the solid line determination sensitivity.
On the other hand, in S125, the control unit 14 determines whether or not traveling on the yellow road has ended, and when an affirmative determination is obtained (S125: Yes), the process proceeds to S130 and a negative determination is made. Is obtained (S125: No), the process proceeds to S145.

  Specifically, the control unit 14 analyzes the road surface image taken by the camera 11 in the same manner as in S105, and when a yellow line having a certain length is not drawn along the traveling direction of the host vehicle, etc. It may be determined that traveling on the yellow road has ended.

  Further, the control unit 14 determines the type of the road on which the host vehicle is traveling from the type information acquired from the navigation device or the like in the same manner as in S105. For example, when the traveling road is not a provisional two-lane road or the like. May determine that traveling on the yellow road has ended.

  In S130, the control unit 14 shifts to the normal mode, returns the edge threshold value to the normal mode threshold value, and cancels the weighting of the luminance of R at the time of conversion to the grayscale image. The extraction sensitivity is restored (S135).

In subsequent S140, the control unit 14 restores the determination sensitivity of the solid line by setting the determination threshold used for determining the type of the lane marking as the normal mode threshold, and the process proceeds to S145.
In S145, the control unit 14 converts the road surface image to generate a grayscale image while reflecting whether the mode is the yellow line mode or the normal mode, and extracts the edge of the lane marking from the grayscale image. And recognize the lane markings.

  In subsequent S150, the control unit 14 determines the type of the lane marking based on the number of edge points extracted for the detected lane marking in a state reflecting whether the mode is the yellow line mode or the normal mode, This process ends.

[Other Embodiments]
(1) The lane marking recognition apparatus 10 according to the present embodiment reduces the edge threshold during the yellow line mode, and converts the road surface image into a grayscale image in a state where the luminance of R of each pixel is weighted. Thus, the yellow line edge point extraction sensitivity is improved. However, the yellow line edge point extraction sensitivity may be improved as follows.

  That is, in S145, the control unit 14 of the lane marking recognition device 10 does not recognize the lane marking based on the luminance of the grayscale image but recognizes the lane marking based on the luminance R of the road surface image in the yellow line mode. You may do it.

  Specifically, the control unit 14 sets a plurality of horizontal scanning lines in the road surface image, compares the R luminance of each pixel adjacent along the scanning line, and the difference in luminance is an edge threshold value. You may extract the point which reached | attained as an edge point of a lane marking. Then, based on the extracted edge point, the lane marking may be detected in the same manner.

  Note that it is desirable to set the edge threshold so that both the white line and the yellow line can be extracted in consideration of the lower brightness of the white line than that of the yellow line. At this time, a threshold smaller than the threshold used during the normal mode may be used as the edge threshold.

Even in such a case, the extraction sensitivity of the yellow line edge point can be improved, and as a result, the accuracy of recognizing the yellow line can be improved.
(2) The lane marking recognition device 10 of the present embodiment is normally running on a yellow line road on the assumption that a white line is used as a road lane marking, but a yellow line is used in some circumstances. In this configuration, the accuracy of recognizing yellow lines is improved. However, depending on the country or region, there may be a possibility that a lane marking of another color is used instead of the white line, or a lane marking of another color (specific color) may be used instead of the yellow line.

  In such a case, the lane marking recognition device 10 uses the edge of the lane marking of the specific color in the same manner as the present embodiment when the host vehicle is traveling on the road where the lane marking of the specific color is used. It is conceivable to improve the point extraction sensitivity.

  Specifically, the extraction sensitivity is improved by converting the road surface image into a grayscale image with the luminance of the color component corresponding to the specific color in each pixel being weighted, or by reducing the edge threshold value. Also good. In addition, as in (1), an edge point may be extracted from the road surface image based on the luminance of the color component corresponding to the specific color, and a partition line may be detected based on the edge point.

By doing so, it is possible to improve the accuracy of recognizing a specific color division line.
[Correspondence with Claims]
The correspondence between the terms used in the description of the above embodiment and the terms used in the description of the claims is shown.

The camera 11 corresponds to a photographing unit.
Further, S105 of the lane marking recognition process corresponds to a road determination means, S115 corresponds to an extraction means, S120 corresponds to a recognition means, S145 corresponds to an extraction means and a recognition means, and S150 corresponds to a recognition means.

  DESCRIPTION OF SYMBOLS 10 ... Marking line recognition apparatus, 11 ... Camera, 12 ... Buzzer, 13 ... Communication part, 14 ... Control part, 15 ... Rain sensor, 16 ... Vehicle speed sensor, 17 ... Yaw rate sensor.

Claims (6)

Photographing means (11) for photographing a road surface of a road ahead of the host vehicle and generating a road surface image which is a color image;
By detecting a change in the color of the road surface image along a predetermined scanning line and comparing the degree of the change with a predetermined edge threshold value, the edge of the division line drawn on the road surface is extracted. Extracting means (S115, S145),
Recognition means (S120, S145, S150) for recognizing the lane marking based on the edge extracted by the extraction means;
An area in which the lane marking is not drawn on the road surface is defined as a road surface area, and the lane marking of a specific color whose degree of color change with respect to the road surface area is smaller than a normal color normally used as the color of the lane marking. Road determination means (S105) for determining whether or not the host vehicle is traveling on the specified specific road;
With
The extraction means improves the extraction sensitivity, which is a sensitivity when extracting the edge of the lane marking of the specific color when the road determination means determines that the host vehicle is traveling on the specific road. about,
A lane marking recognition device characterized by the above. The lane marking recognition apparatus according to claim 1,
The normal color is white, and the specific color is yellow to orange,
A lane marking recognition device characterized by the above. In the lane marking recognition device according to claim 1 or 2,
The extraction means converts the road surface image into a gray scale image, detects a change in shading on the gray scale image as a color change on the road surface image, and the vehicle determination means detects the vehicle by the road determination means. When it is determined that the vehicle is traveling on a road, the extraction sensitivity is improved by converting the road surface image into the grayscale image in a state where the color component corresponding to the specific color is weighted. ,
A lane marking recognition device characterized by the above. In the lane marking recognition device according to claim 1 or 2,
When the road determination unit determines that the vehicle is traveling on the specific road, the extraction unit displays a change in luminance of a color component corresponding to the specific color on the road image on the road image. Improving the extraction sensitivity by detecting as a color change of
A lane marking recognition device characterized by the above. In the lane marking recognition device according to any one of claims 1 to 4,
The extraction means improves the extraction sensitivity by lowering the edge threshold when the road determination means determines that the host vehicle is traveling on the specific road;
A lane marking recognition device characterized by the above. In the lane marking recognition device according to any one of claims 1 to 5,
The recognition means is
The lane marking is detected based on the edge extracted by the extraction means, and the lane marking is determined to be a solid line when the number of edges related to the lane marking reaches a predetermined threshold for determination. At the same time, if the number of edges does not reach the threshold for determination, it is determined that the partition line is a broken line,
Lowering the determination threshold when the road determination means determines that the host vehicle is traveling on the specific road;
A lane marking recognition device characterized by the above.

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