JP2007322231A - Road surface condition detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a road surface condition detector for precisely detecting a road surface condition (whether the road surface is dry or wet) while traveling. <P>SOLUTION: A vehicle speed sensor 15 detects vehicle speed while a control part 11 actuates respective parts if the vehicle speed detected by the speed sensor 15 exceeds a prescribed speed. A camera 12 generates image data by photographing the backside of a wheel bringing about water splashes on a wet road surface. An image analysis part 13 frequency-analyzes the image data generated by the camera 12 and calculates an integrated value by integrating prescribed frequency components characteristic of water splashes. A determination part 14 determines whether the integrated value calculated by the analysis part 13 is larger than a prescribed value or not to output a signal showing that the road surface is wet where the integrated value is larger than the prescribed value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a road surface state detection device that is mounted on a vehicle such as an automobile and detects a road surface state (road surface wetness) of a road.

  The driving support system for automobiles detects various information such as the operating state of the brakes and steering wheel by the driver, speed, and the distance between vehicles with other cars, and makes comprehensive judgment on these information to make it safer. In order to be able to travel, the vehicle is controlled on behalf of the driver, and has been developed in recent years. For example, when it is determined that there is a risk of a rear-end collision during driving, the driving support system reduces the speed and secures a safe inter-vehicle distance. Do.

The braking distance of an automobile is determined by the vehicle weight, the speed, and the friction between the tire and the road surface. When the vehicle weight and the speed are the same, the braking distance becomes longer as the friction between the tire and the road surface becomes smaller. In addition, if the friction between the tire and the road surface is small, slipping is likely to occur when a lateral force is generated due to a curve or lane change. The friction between the tire and the road surface changes depending on the road surface condition, and the wet road surface wet by rain becomes smaller than the dry road surface. For this reason, it is desirable that the road surface condition is taken into account in the travel control performed by the driving support system, and the inter-vehicle distance should be kept longer when wet. In order to detect the road surface condition, it is conceivable to use the rain detection device disclosed in Patent Document 1. This rain detection device detects rain by adhering raindrops attached to the windshield of an automobile.
JP 2004-106763 A

  However, since the above-described rainfall detection device cannot directly detect the road surface condition, when the road surface is wet despite no rain, such as immediately after the rain, the road surface condition is appropriately determined. It is not possible to perform proper traveling control. Since it is easy for the driver to determine that the road surface is wet during rainfall, the road surface condition should be accurately detected only when there is no rain, which is difficult for the driver to notice and to be alert. A detection device is desired.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a road surface condition detection device that can accurately detect a road surface condition during traveling.

  In order to achieve the above object, a road surface condition detection device according to the present invention is mounted on a vehicle and detects the road surface state. The road surface state detection device captures image data of a rear side of a wheel where splashing occurs on a wet road surface. The image data generated by the image capturing means, the image analysis means for frequency-analyzing the image data generated by the image capturing means, integrating the predetermined frequency components characteristic of splashing, and calculating the integrated value, and the image analysis means And determining means for determining whether or not the integrated value is larger than a predetermined value and outputting a signal indicating that the road surface is wet when the integrated value is larger than the predetermined value.

  The image analysis means preferably performs one-dimensional Fourier transformation in a direction substantially orthogonal to the splashing direction of the splash, extracts a predetermined frequency component from the obtained frequency spectrum, and performs integration. Also provided is a vehicle speed detection means for detecting the vehicle speed, and a control means for operating the photographing means, the image analysis means, and the determination means when the vehicle speed detected by the vehicle speed detection means exceeds a predetermined speed. It is preferable.

  In order to achieve the above object, a road surface condition detection device according to the present invention is mounted on a vehicle and detects a road surface condition by photographing a rear side of a wheel in which splashing occurs on a wet road surface. First image capturing means for acquiring image data, second image capturing means for acquiring image data by capturing the front of a wheel where splashing does not occur, frequency analysis of the image data acquired by the first image capturing means, and spraying The first image analysis means for calculating the first integrated value by integrating the predetermined frequency components characteristic to the above and the image data acquired by the second imaging means are frequency-analyzed and the same as the first image analysis means Obtained by the second image analysis means from the second image analysis means for calculating the second integrated value by integrating the frequency components of the first and the first integrated value obtained by the first image analysis means. A difference means for calculating a difference value obtained by subtracting the second integrated value, and determining whether or not the difference value calculated by the difference means is greater than a predetermined value. And determining means for outputting a signal indicating that the road surface is wet.

  The first image analysis means preferably performs one-dimensional Fourier transformation in a direction substantially orthogonal to the splashing direction of the splash, extracts a predetermined frequency component from the obtained frequency spectrum, and performs integration. Also, a vehicle speed detecting means for detecting the vehicle speed, and when the vehicle speed detected by the vehicle speed detecting means exceeds a predetermined speed, the first and second imaging means, the first and second image analyzing means, and the difference means And a control means for operating the determination means.

  In order to achieve the above object, a road surface condition detection apparatus according to the present invention is mounted on a vehicle and detects a road surface condition. In the road surface condition detection apparatus, a first region behind a wheel in which splashing occurs on a wet road surface; Imaging means for capturing image data by capturing an area including a second area in front of the wheel where no splashing occurs, and frequency analysis of a portion corresponding to the first area of the image data acquired by the imaging means A first image analysis unit that calculates a first integrated value by integrating predetermined frequency components characteristic of splashing, and a portion corresponding to the second region in the image data acquired by the photographing unit has a frequency Analyzing and integrating the same frequency component as the first image analyzing means to calculate a second integrated value; and whether the first integrated value obtained by the first image analyzing means A difference means for calculating a difference value obtained by subtracting the second integrated value obtained by the second image analysis means, and determining whether or not the difference value calculated by the difference means is greater than a predetermined value. And determining means for outputting a signal indicating that the road surface is wet when the value is larger than a predetermined value.

  The first image analysis means preferably performs one-dimensional Fourier transformation in a direction substantially orthogonal to the splashing direction of the splash, extracts a predetermined frequency component from the obtained frequency spectrum, and performs integration. A vehicle speed detecting means for detecting the vehicle speed; and when the vehicle speed detected by the vehicle speed detecting means exceeds a predetermined speed, the photographing means, the first and second image analyzing means, the difference means, and the determining means It is preferable that the control means to operate is provided.

  The road surface condition detection device according to the present invention determines whether or not the road surface is wet while traveling because it directly determines whether or not the water spray is scattered by the rotation of the wheel during traveling. can do.

  In FIG. 1, a road surface condition detection apparatus 10 according to the first embodiment of the present invention includes a control unit 11, a camera 12, an image analysis unit 13, a determination unit 14, and a vehicle speed sensor 15. ) 20 (see FIG. 2). The vehicle speed sensor 15 is a well-known vehicle speed detector that calculates the traveling speed (vehicle speed) of the vehicle 20 from the rotational speed of the wheels (tires) 21, and inputs the detected vehicle speed signal to the control unit 11 as needed. The control unit 11 determines the vehicle speed based on the vehicle speed signal input from the vehicle speed sensor 15, and operates the camera 12, the image analysis unit 13, and the determination unit 14 when the vehicle speed is equal to or higher than a predetermined speed.

  As shown in FIG. 2, the camera 12 is attached to the lower part of the vehicle 20 and photographs the rear of a wheel (for example, a front wheel) 21 from the inside. The camera 12 includes a photographic lens, an image sensor such as a CCD or CMOS sensor, a signal processing circuit, and the like. The image sensor photoelectrically converts an optical image of a subject formed through the photographic lens to generate a voltage signal. The signal processing circuit performs signal processing such as gain adjustment, double correlation sampling, and A / D conversion on the imaging signal generated by the imaging device, and generates digital image data.

  FIG. 3 shows a shooting area 23 shot by the camera 12. The imaging region 23 is a region where splashes 24 are generated when the road surface 22 is wet behind the contact portion between the wheel 21 and the road surface 22 (opposite to the traveling direction). The image analysis unit 13 applies a high-pass filter to the image data of the imaging region 23 generated by the camera 12, and extracts a predetermined spatial frequency component characteristic of the splash 24 that is scattered by the rotation of the wheel 21. Specifically, since the spray 24 has a high-frequency component in the AA ′ direction substantially orthogonal to the scattering direction, the entire imaging region 23 is subjected to a one-dimensional Fourier transform in the AA ′ direction and obtained by the Fourier transform. Integration is performed by extracting high frequency components of a predetermined value or more from the obtained frequency spectrum.

  In addition, when performing the frequency analysis, the image analysis unit 13 preferably excludes the images of the wheels 21 and the road surface 22 from the analysis target. Further, when the road surface 22 is reflected in the background of the splash 24, the frequency analysis is affected. Therefore, it is preferable to provide a plain board or the like behind the splash 24 so that the road surface 22 is not photographed. Further, the region from which the high frequency component is extracted is not limited to the entire region of the imaging region 23 but may be limited to a part of the imaging region 23 (for example, the region 25 shown in FIG. 4). By limiting the area, it is possible to speed up the analysis process. It is also preferable to provide an illuminating device that irradiates the imaging region 23 with light in consideration of a shortage of imaging light quantity at night or the like.

  The determination unit 14 determines whether or not the integrated value of the frequency calculated by the image analysis unit 13 is larger than a predetermined value. If the integrated value is larger than the predetermined value, it is determined that the spray 24 is detected and the road surface 22 is detected. A wetness detection signal indicating that is in a wet state is output. On the other hand, when the road surface 22 is not wet and the spray 24 does not occur, the high-frequency component is small, and the integrated value of the frequency calculated by the image analysis unit 13 is smaller than the predetermined value. In this case, the wetness detection signal is not output. The wetness detection signal output from the determination unit 14 is input to a driving support system or the like and used for travel control of the vehicle 20.

  The effect | action by the said structure is demonstrated using the flowchart shown in FIG. When the vehicle 20 starts traveling, detection of the vehicle speed of the vehicle 20 is started by the vehicle speed sensor 15 (step S1). When the vehicle speed is determined by the control unit 11 (step S2) and the vehicle speed falls below a predetermined speed (for example, 30 km / h) (No determination), the traveling safety is ensured even when the road surface is wet. Therefore, the vehicle speed sensor 15 continues to detect the vehicle speed without shifting to the following detection operation. When the controller 11 determines that the vehicle speed has exceeded the predetermined speed (Yes determination), the camera 12 captures an image of the imaging region 23 located behind the wheel 21 (step S3).

  When the image data of the imaging region 23 is generated by the camera 12, the image analysis unit 13 executes frequency analysis and performs predetermined analysis from a frequency spectrum obtained as a result of one-dimensional Fourier transform in the AA ′ direction. Only high frequency components equal to or greater than the value are extracted, and the extracted high frequency components are integrated (step S4). The integrated value calculated by the image analysis unit 13 is determined by the determination unit 14 to be larger than a predetermined value (step S5). When the integrated value is larger than the predetermined value (Yes determination), the spray 24 is detected, the road surface 22 is determined to be in a wet state, and a wetness detection signal is output. On the other hand, when the integrated value is smaller than the predetermined value (No determination), the wetness detection signal is not output, and the process returns to the detection of the vehicle speed in step S1.

  As described above, the road surface condition detection device 10 determines whether or not there is splashing sprayed by the rotation of the wheel during traveling by directly photographing, so the road surface condition (wet and dry on the road surface) during traveling. Can be accurately detected.

  Next, FIG. 6 shows a road surface condition detection apparatus 30 according to the second embodiment of the present invention. The road surface condition detection device 30 includes a control unit 31, a first camera 32, a second camera 33, a first image analysis unit 34, a second image analysis unit 35, a difference calculation unit 36, and a determination unit 37. The control unit 31 determines the vehicle speed based on the vehicle speed signal input from the vehicle speed sensor 15, and if the vehicle speed is equal to or higher than the predetermined speed, the first and second cameras 32 are configured. , 33, the first and second image analysis units 34, 35, the difference calculation unit 36, and the determination unit 37 are operated.

  The first and second cameras 32 and 33 have the same configuration as the camera 12 and are attached to the lower part of the vehicle 20. FIG. 7 shows imaging regions 23 and 38 that are imaged by the first and second cameras 32 and 33, respectively. The first camera 32 shoots the shooting area 23 located behind the wheel 21 where the spray 24 is generated with the road surface 22 wet, and generates image data. The second camera 33 shoots the shooting area 38 located in front of the wheel 21 where the splash 24 does not occur, and generates image data. The imaging region 38 is in a positional relationship symmetrical to the imaging region 23 with respect to a perpendicular line P that passes through the center of the wheel 21 and is perpendicular to the road surface 22.

  The first image analysis unit 34 performs frequency analysis (one-dimensional Fourier transform in the AA ′ direction) similar to that of the image analysis unit 13 on the image data generated by the first camera 32 to obtain a predetermined value. The above high frequency components are extracted and integrated to calculate an integrated value (hereinafter referred to as a first integrated value). In addition, the second image analysis unit 35 performs one-dimensional Fourier transform on the image data generated by the second camera 33 in the BB ′ direction, extracts high frequency components that are greater than or equal to a predetermined value, and integrates them. The integrated value (hereinafter referred to as the second integrated value) is calculated. The first and second image analysis units 34 and 35 extract the same frequency component.

  The difference calculating unit 36 calculates a difference value obtained by subtracting the second integrated value calculated by the second image analyzing unit 35 from the first integrated value calculated by the first image analyzing unit 34. The determination unit 37 determines whether or not the difference value calculated by the difference calculation unit 36 is larger than a predetermined value. If the difference value is larger than the predetermined value, the spray surface 24 is detected and the road surface 22 is wet. A wetness detection signal indicating the state is output.

  The road surface condition detection device 30 images the imaging regions 23 and 38 by the first and second cameras 32 and 33, respectively, and from the first integrated value (the integrated value of the first embodiment) obtained from the image data of the imaging region 23. Except for subtracting the second integrated value obtained from the image data of the imaging region 38, the same operation as the road surface condition detection apparatus 10 of the first embodiment is performed. Since the splash 24 appears only in the photographing area 23 on the rear side in the traveling direction and hardly appears in the photographing area 38 on the front side in the traveling direction, by subtracting the second accumulated value from the first accumulated value, Can be removed. Note that when the splash 24 is not generated, the second integrated value is substantially equal to the first integrated value.

  Similarly, in the case of the second embodiment, the region from which the high-frequency component is extracted is not limited to the entire region of the imaging regions 23 and 38 but may be limited to a part of the imaging regions 23 and 38. It is also preferable to provide an illuminating device that irradiates light to the photographing regions 23 and 38 in consideration of a shortage of photographing light amount at night or the like.

  Next, FIG. 8 shows a road surface condition detection apparatus 40 according to the third embodiment of the present invention. The road surface condition detection apparatus 40 includes a camera 41, the above-described control unit 31, first and second image analysis units 34 and 35, a difference calculation unit 36, a determination unit 37, and a vehicle speed sensor 15, and the control unit 31 includes When the vehicle speed is determined based on the vehicle speed signal input from the vehicle speed sensor 15 and the vehicle speed is equal to or higher than the predetermined speed, the camera 41, the first and second image analysis units 34 and 35, the difference calculation unit 36, and The determination unit 37 is operated.

  In the present embodiment, the first and second cameras 32 and 33 of the second embodiment are configured as one camera 41. The camera 41 includes an area 42 including the imaging areas 23 and 38 shown in FIG. To generate image data. The first image analysis unit 34 performs frequency analysis on a portion corresponding to the shooting region (first region) 23 from the image data generated by the camera 41, and the second image analysis unit 35 performs image data generated by the camera 41. To a portion corresponding to the imaging region (second region) 38 is subjected to frequency analysis. Since other operations are the same as those in the second embodiment, description thereof is omitted. In the present embodiment, the same effect as in the second embodiment can be obtained.

  In the first to third embodiments, the image analysis unit extracts a frequency component (high frequency component) equal to or higher than a predetermined value from the image data. However, the upper limit of the extraction frequency is defined and is from a certain lower limit value. You may make it extract the frequency component (frequency band) to an upper limit.

It is a block diagram which shows the structure of the road surface condition detection apparatus concerning 1st Embodiment of this invention. It is a front view of the vehicle which shows the installation location of a camera. It is a side view of the wheel which shows the photography field of a camera. It is a side view of the wheel which shows the field which performs frequency analysis. It is a flowchart which shows operation | movement of a road surface condition detection apparatus. It is a block diagram which shows the structure of the road surface condition detection apparatus concerning 2nd Embodiment of this invention. It is a side view of the wheel which shows the photography field of the 1st and 2nd camera. It is a block diagram which shows the structure of the road surface condition detection apparatus concerning 3rd Embodiment of this invention. It is a side view of the wheel which shows the photography field of a camera.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Road surface condition detection apparatus 11 Control part (control means)
12 Camera (photographing means)
13 Image analysis unit (image analysis means)
14. Determination part (determination means)
15 Vehicle speed sensor (vehicle speed detection means)
20 Vehicle 21 Wheel 22 Road Surface 30 Road Surface Condition Detection Device 31 Control Unit (Control Unit)
32 1st camera (1st imaging means)
33 Second camera (second photographing means)
34 1st image analysis part (1st image analysis means)
35 Second image analysis unit (second image analysis means)
36 Difference calculation unit (difference means)
37 determination unit (determination means)
40 Road surface condition detection device 41 Camera (photographing means)

Claims (9)

In a road surface condition detection device that is mounted on a vehicle and detects a road surface condition,
Photographing means for photographing the rear of a wheel where splashing occurs on a wet road surface and generating image data;
Image analysis means for analyzing the frequency of the image data generated by the photographing means, and calculating an integrated value by integrating predetermined frequency components characteristic of splashing;
Determining whether or not the integrated value calculated by the image analyzing means is greater than a predetermined value, and outputting a signal indicating that the road surface is wet when the integrated value is greater than the predetermined value. A road surface condition detection device.   2. The image analysis unit according to claim 1, wherein the image analysis unit performs a one-dimensional Fourier transform in a direction substantially orthogonal to a splashing direction of the splash, extracts a predetermined frequency component from the obtained frequency spectrum, and performs integration. Road surface condition detection device.   Vehicle speed detecting means for detecting the vehicle speed, and control means for operating the photographing means, the image analyzing means, and the determining means when the vehicle speed detected by the vehicle speed detecting means exceeds a predetermined speed. The road surface condition detection apparatus according to claim 1 or 2, characterized in that In a road surface condition detection device that is mounted on a vehicle and detects a road surface condition,
First imaging means for capturing image data by capturing the rear of a wheel where splashing occurs on a wet road surface;
Second imaging means for acquiring image data by imaging the front of the wheel where splashing does not occur;
First image analysis means for frequency-analyzing the image data acquired by the first imaging means and calculating a first integrated value by integrating predetermined frequency components characteristic of splashing;
A second image analysis means for frequency-analyzing the image data acquired by the second imaging means and calculating a second integrated value by integrating the same frequency components as the first image analysis means;
Difference means for calculating a difference value obtained by subtracting the second integrated value obtained by the second image analyzing means from the first integrated value obtained by the first image analyzing means;
Determining means for determining whether or not the difference value calculated by the difference means is greater than a predetermined value, and outputting a signal indicating that the road surface is wet when the difference value is greater than the predetermined value. Road surface condition detection device.   5. The first image analysis means performs one-dimensional Fourier transform in a direction substantially orthogonal to the splashing direction of the splash, extracts a predetermined frequency component from the obtained frequency spectrum, and performs integration. The road surface condition detection apparatus described.   Vehicle speed detection means for detecting the vehicle speed, and when the vehicle speed detected by the vehicle speed detection means exceeds a predetermined speed, the first and second imaging means, the first and second image analysis means, the difference means, and the 6. The road surface condition detection apparatus according to claim 4, further comprising a control unit that operates the determination unit. In a road surface condition detection device that is mounted on a vehicle and detects a road surface condition,
An imaging means for acquiring image data by imaging an area including a first area behind the wheel where splashing occurs on a wet road surface and a second area ahead of the wheel where splashing does not occur;
First image analysis means for calculating a first integrated value by frequency-analyzing a portion corresponding to the first region of the image data acquired by the photographing means and integrating predetermined frequency components characteristic of splashing; ,
Second image analysis means for calculating a second integrated value by frequency-analyzing a portion corresponding to the second region in the image data acquired by the photographing means and integrating the same frequency component as the first image analysis means. When,
Difference means for calculating a difference value obtained by subtracting the second integrated value obtained by the second image analyzing means from the first integrated value obtained by the first image analyzing means;
Determining means for determining whether or not the difference value calculated by the difference means is greater than a predetermined value, and outputting a signal indicating that the road surface is wet when the difference value is greater than the predetermined value. Road surface condition detection device.   8. The first image analysis means performs one-dimensional Fourier transform in a direction substantially orthogonal to the splashing direction of the splash, extracts a predetermined frequency component from the obtained frequency spectrum, and performs integration. The road surface condition detection apparatus described.   Vehicle speed detection means for detecting the vehicle speed, and when the vehicle speed detected by the vehicle speed detection means exceeds a predetermined speed, the photographing means, the first and second image analysis means, the difference means, and the determination means are operated. 9. The road surface condition detection apparatus according to claim 7, further comprising a control unit.

Images