JP3360119B2 - Road surface inspection sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface inspection sensor for determining the state of a road on which a vehicle travels.

[0002]

2. Description of the Related Art In order to realize safe road traffic, it is important to always keep track of the road surface on which the vehicle is traveling. For this reason, conventionally, a road surface determination device is fixedly installed on one side (road shoulder) of a road, and the road surface state is optically detected and determined by the road surface determination device. However, in the case of such a road surface discriminating device, since the device itself is fixed to a specific place, only road surface information within a certain area (range) can be detected. And the road surface condition of the entire road could not be accurately grasped.

For this reason, in recent years, a vehicle-mounted road surface discriminating device capable of continuously grasping the road surface condition has been desired. As such a road surface discriminating device, a road surface discriminating device utilizing a spatial filter is known. . First, the principle of determining the road surface using the spatial filter will be briefly described. That is, as shown in FIG. 5, an optical system 4 in which a light receiving lens 2 and a condensing lens 3 are arranged via a spatial filter 1 so as to face a road surface (the ground), and light is applied to the road surface by illumination 5 The light is reflected on the road surface, and the reflected light is condensed from the light receiving lens 2 via the spatial filter 1 to the condenser lens 3, and an output signal is detected by the photodiode (PD) 7. Thus, the detected output signal appears as a sinusoidal signal waveform corresponding to the traveling speed (time) as shown in FIG. 6, and this signal waveform changes every time according to the road surface condition. That is, such a change in the waveform (hereinafter, this change is referred to as “fluctuation”) is due to the size, brightness, and undulations of the particles that constitute the road surface. In the case of "dry asphalt", the output signal is a substantially linear signal without fluctuation as shown in FIG. 7A, and in the case of "snow", the output signal is as shown in FIG. 7B. Is output as a signal in which a low-frequency fluctuation is superimposed on a sine wave signal. This indicates that the spatial frequencies of the reflecting objects (surface of the road surface) constituting the road surface have different distributions.

FIG. 8 is a correlation distribution diagram comparing such a spatial frequency distribution between "dry asphalt" and "snow". The correlation distribution diagram converts an output signal obtained as a function of time into a speed. Based on the predetermined distance on the road surface (about 1m)
Is converted into a signal corresponding to the length of the signal and frequency-analyzed. According to this correlation distribution diagram, there is a remarkable difference in low frequency components between "dry asphalt" and "snow".
This difference makes it possible to determine the road surface condition.

FIG. 9 shows an example of a road surface discriminating apparatus using the above-mentioned spatial filter as disclosed in Japanese Patent Application No. 7-503399.
1 shows a road surface discriminating device disclosed in Japanese Patent Application Laid-Open Publication No. H10-26095. Briefly explaining this, as shown in FIG. 9, the optical system constituting the spatial filter is a grating plate 9 (slit array),
It is composed of a prism array 10, a condenser lens 11, and two photodiodes (PDs) 12, 12. Here, the prism array 10 mainly functions as a spatial filter. Further, a light emitting diode 13 is provided as a light source for illumination, and light emitted from the light emitting diode 13 is incident on the photodiode 12 via the light receiving lens 14, the slit plate 15, and the prism array 10, and its output is output. A signal is detected. Reference numeral 17 denotes a light emitting diode used as a light source for regular reflection. The output signal detected by such a road surface identification device is calculated by a signal processing circuit and converted into an electric signal as identification data.

FIG. 10 shows an example of an algorithm for determining a road surface state based on a converted electric signal. That is, in this example, the ratio between the low frequency component (Db) and the center frequency component (Da) is calculated, and this ratio is set to the threshold value (TH
1) is compared with the threshold value (TH2), and the ratio “Db /
If “Da” is larger than the threshold value (TH1), the road surface is determined to be “snow”, and the threshold value (TH1) and the threshold value (T
H2) (medium), the road surface is determined to be a "gravel road", and if it is equal to or smaller than the threshold value (TH2) (small), the road surface is determined to be an asphalt road. Further, the algorithm for such determination is a light-emitting diode 17 for regular reflection (see FIG. 9).
By using the detection signal from the temperature sensor that detects the road surface temperature, as shown in FIG. 11, the road surface state is "wet asphalt", "dry asphalt", "gravel road", "snow", "freeze" etc. This makes it possible to make a distinction in the classification.

[0007]

By the way, in the case of the conventional road surface patrol sensor as described above, the road surface condition in a predetermined area is "asphalt", "gravel road", "snow", and "ice".
In such a case, it is relatively easy to discriminate and can be used as accurate information. For example, (1) snow that has accumulated on the road surface has melted and has become a sherbet-shaped snow surface (hereinafter referred to as “jam snow”). When the road surface condition or (2) a road surface whose surface is a snow surface and its lower surface is an ice plate (hereinafter referred to as an “ice plate under snow”) is determined, the determination is performed. It is difficult and not easy, and when the road surface is “jam snow” or “ice plate under snow”, there is a particular danger when the vehicle runs, and therefore, it is desired to improve the discrimination accuracy.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional road surface discriminating apparatus, and to accurately correct even a relatively difficult road surface condition such as "jam snow" or "ice plate under snow". Another object of the present invention is to provide a road surface determining device capable of performing accurate and accurate determination.

[0009]

According to the present invention, in order to achieve the above-mentioned object, an invention according to claim 1 is provided with a light source mounted on a vehicle and irradiating light to a road surface, and a road surface. A road surface sensor having a light receiving unit that receives the reflected light through a spatial filter, and a road surface determination device that has an arithmetic processing unit that converts the received reflected light into an electric signal, wherein the arithmetic processing unit includes a road surface determination unit and A variation detection unit, wherein the road surface determination unit detects the first road surface detection data based on the short road surface distance and the second road surface detection data based on the long road surface distance, and performs the second road surface detection. The data is temporarily stored in the memory unit, and a fluctuation is calculated based on the detected data during the change of the second road surface detection data, and the road surface state whose surface state is changing from the fluctuation calculation data is calculated. Know To, and is characterized in that to determine the road surface condition.

According to a second aspect of the present invention, in the first aspect of the present invention, there is provided a temperature sensor for detecting a road surface temperature. The center frequency component and the center frequency component are output to the variation detection unit, and the low frequency component and the center frequency component are logarithmized, the past variation is added, and the determination result data based on this variation and the temperature sensor data are used. It is characterized by determining the road surface condition.

[0011]

1 to 3 show an embodiment of a road surface patrol sensor road surface discriminating apparatus according to the present invention. That is, as shown in FIG. 1, the road surface inspection sensor road surface determination device includes a road surface sensor 20 that monitors a road surface state as the vehicle travels, and a calculation unit 21 that processes and determines a detected output signal. . The road surface sensor 20 is installed near the front bumper of the vehicle, and the detection data analyzed (road surface determination) by the arithmetic unit 21 is transmitted to a traffic control center or the like as a transmission signal (communication data) and used. Here, in the road surface identification device of the present invention, the algorithm in the arithmetic unit 21 is characterized by:
Since the configuration itself of the road surface sensor 20 can adopt a conventional configuration, the arithmetic unit 21 will be described in detail below.

As shown in FIG. 2, the calculation unit 21 includes a road surface determination unit.
In addition to a variation detection unit 24, the road determination unit 23 detects road surface data for each “short distance (less than 1 m)” in the same manner as in the related art, while the variation detection unit 24 determines “long distance”. (20 m or more) "is detected. The road surface detection data detected at the “long distance” is temporarily stored in a memory 25 connected to the variation detection unit 24.

Hereinafter, the first embodiment will be described in detail. First, the detection signals detected by the road surface sensor 20 and the temperature sensor 26 as the vehicle travels
Is input to the road surface determination unit 23. Then, in the road surface determination unit 23, the low frequency component (Index1 (x)) and the center frequency component (Index2 (x)) of the light reflected from the road surface are output to the variation detection unit 24, respectively. At this time, the determination result of the road surface by the temperature sensor 26 is also output to the variation detection unit 24 almost simultaneously. That is, a method of classifying a road surface state using two indices (index 1: Index 1 and index 2: Index 2) in order to clarify a difference in frequency components depending on the road surface is employed. The sum of the signal intensities in the low frequency region is referred to as a "low frequency component", and the value obtained by normalizing the sum of the low frequency components of the dried asphalt is referred to as Index1 (index 1). Also, the sum of the signal intensities near the center frequency of the spatial filter is referred to as “center frequency component”, and similarly, the one normalized by the low-frequency component of dry asphalt is referred to as Index2 (index 2). Here, the “low frequency component” and the “center frequency component” are calculated by integration using a calculation formula (not shown). Specifically, when data is plotted in accordance with such two indices (Index1, Index2), a plot area (see FIG. 4) indicating the road surface condition can be obtained.

Next, the algorithm in the arithmetic unit 21 as described above will be described in detail with reference to the flowchart of FIG. That is, the low frequency component (Index 1) detected by the road surface sensor 20 and taken in from the road surface determination unit 23.
(x)) and the center frequency component (Index2 (x)) are subjected to logarithmic processing (STEP 1). Specifically, the logarithmic operation value of each frequency component is calculated by the following equation (1).

## EQU1 ## I _L1 (x) = log ₁₀ (Index1 (x)) I _L2 (x) = log ₁₀ (Index2 (x))

Then, the previously calculated low frequency component (Index
1 (x)) and the logarithmic component of the center frequency component (Index2 (x)) (I
_L1 (x-1), I _L2 (x-1)) and the amount of variation (Dif (x)) are calculated using the following equation (“the theorem of three squares”), and the result of this calculation is It is stored in the memory 25 (see FIG. 2).

(Equation 2)

Here, in order to estimate the variation, the past L
(M) is fetched from the memory 25 and added,
The value is substituted for the variation S (x) (STEP 2). The following equation (3) is established for calculating the variation S (x).

(Equation 3)

Next, it is checked whether or not the numerical value of S (x) calculated by the above equation (3) exceeds "threshold: St (constant)" (STEP 3). The result of the road surface determination unit is selected and adopted as it is.
On the other hand, when the variation is large, it is determined as detection data by comparing the data areas plotted in the “variation area” shown in FIG.
4). That is, in this example, FIG.
The detection data is plotted in the data area based on the logarithmically processed “Index1” on the horizontal axis and the logarithmically processed “Index2” on the vertical axis. . There is no unit because each numerical value is a numerical value representing a logarithm. Then, in this "range of variation" range, in this example, "thick wet ice film", "thin wet ice film", "shiny ice plate", "matte ice plate",
There are plot data such as “Snow surface” and “Dry”, among which “Area A”, which is at the almost middle fluctuation position.
Is determined that the road surface is in the “jam snow” state, and the plot data in the range of “region B” is determined that the road surface is in the “snow under ice” state. On the other hand, if the fluctuation amount is other than “regions A and B”, the road surface determination unit 23
The output result of the road surface is obtained from the adoption of the discrimination result obtained by the above as the output result as it is. The obtained determination result is transmitted to a road control center or the like by using a communication I / F or the like and used as traffic information, and a driver is notified of a road surface condition by a “traffic information display panel” or the like. You.

[0018]

The present invention is as described above. According to the first aspect of the present invention, there is provided a light source which is mounted on a vehicle and emits light toward a road surface and a spatial filter which filters light reflected by the road surface. A road surface sensor having a light receiving unit that receives light through
In a road surface determination device having an arithmetic processing unit that converts received reflected light into an electric signal, the arithmetic processing unit has a road surface determination unit and a variation detection unit, and the road surface determination unit is based on a first road surface distance based on a short road surface distance. The detection of the road surface detection data and the detection of the second road surface detection data based on the long road surface distance are performed, the second road surface detection data is temporarily stored in the memory unit, and the fluctuation of the second road surface detection data is changed. The fluctuation calculation is performed based on the detected data in the middle, and the road surface state in which the surface state is changing is identified from the fluctuation calculation data to determine the road surface state. There is an effect that accurate and accurate determination can be made even in a road surface state where it is relatively difficult to determine.

According to a second aspect of the present invention, in the first aspect of the present invention, there is provided a temperature sensor for detecting a road surface temperature. The center frequency component and the center frequency component are output to the variation detection unit, and the low frequency component and the center frequency component are logarithmized, the past variation is added, and the determination result data based on this variation and the temperature sensor data are used. Since the road surface condition is determined, it is possible to accurately and accurately determine even a relatively difficult road surface condition such as jam snow or an ice plate under snow.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a vehicle equipped with a road surface inspection sensor of the present invention.

FIG. 2 is a block diagram showing a calculation unit of the road surface inspection sensor of the present invention.

FIG. 3 is a flowchart showing the algorithm.

FIG. 4 is a data distribution diagram showing a range of a “variation region” plotted based on detection data.

FIG. 5 is a principle diagram showing a road surface determination method using a spatial filter.

FIG. 6 is a waveform chart showing an example of the output signal.

FIG. 7 (A) is an output signal of “dry asphalt”,
(B) is a waveform diagram showing an output signal of “snow”.

FIG. 8 is a distribution diagram showing spatial frequency conditions of “dry asphalt” and “snow”.

FIG. 9 is a perspective view showing an example of a conventional road surface inspection sensor.

FIG. 10 is a flowchart illustrating an example of a conventional road surface determination algorithm.

FIG. 11 is a flowchart illustrating another example of a conventional road surface determination algorithm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spatial filter 2 Light receiving lens 3 Condensing lens 4 Optical system 5 Lighting 7 Photodiode (PD) 9 Lattice plate (slit array), 10 Prism array 11 Condensing lens 12 Photodiode (PD) 13, 17 Light emitting diode 14 Light receiving Lens, 15 Slit plate 20 Road surface sensor 21 Calculation unit 23 Road surface determination unit 24 Variation detection unit 25 Memory 26 Temperature sensor

Continuation of the front page (56) References JP-A-10-221042 (JP, A) JP-A-2000-180357 (JP, A) JP-A-7-49223 (JP, A) JP-A-10-103939 (JP, A A) Patent 2697307 (JP, B2) Patent 2707425 (JP, B2) Patent 2707427 (JP, B2) Masasuke Hirata, Yasuhiro Miyata, Masashi Nakano, Eiichi Shiba, "Development of Road Condition Sensing System," Electronic Information, 1999 Proceedings of the Conference of the Institute of Communication Engineers Information and systems 1, Japan, The Institute of Electronics, Information and Communication Engineers, March 8, 1999, SID-1-2, p. 351- 352 Keisuke Hirasawa, Yasuhiro Miyata, Masashi Nakano, Eiichi Shiba, "Development of Road Condition Sensing System", Proc. Of the 1999 IEICE General Conference, Information and Systems 2, Japan, The Institute of Electronics, Information and Communication Engineers , March 8, 1999, SID-1-2, p. 395- 396 Yuichi Shinmoto, Toshiro Nakao, Junichi Takagi, "Winter Road Management System Using GVS", OMRON TECHNICS, Japan, OMRON Corporation, December 20, 1998, Vol. 38, No. 4, p. . 403-409 Yoshio Murata, Yuichi Niimoto, Junichi Takagi, "Road surface discrimination sensor for general vehicles", OMRON TECHNICS, Japan, Omron Corporation, December 20, 1998, Vol. 38, No. 4, p. 410-416 (58) Field surveyed (Int. Cl. ⁷ , DB name) G01W 1/00-1/18 G01B 11/30 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. A road surface sensor having a light source mounted on a vehicle and emitting light toward a road surface, a light receiving unit receiving light reflected by the road surface through a spatial filter, and an electric signal representing the received reflected light. The arithmetic processing unit has a road surface determination unit and a variation detection unit, and the road surface determination unit detects and detects first road surface detection data based on a short road surface distance. The second road surface detection data is detected based on the road surface distance, the second road surface detection data is temporarily stored in the memory unit, and the second road surface detection data is detected based on the detection data in the middle of the change. ,
A road surface inspection sensor which performs a fluctuation calculation, identifies a road surface state whose surface state is changing on the basis of the fluctuation calculation data, and determines the road surface state. A temperature sensor for detecting a road surface temperature;
The road surface detection data by the temperature sensor and the low frequency component and the central frequency component of the reflected light are output from the road surface determining unit to the variation detecting unit, and these low frequency components and the central frequency component are logarithmized, and the past fluctuation amount is calculated. The road surface inspection sensor according to claim 1, wherein the road surface state is determined based on the determination result data based on the variation and the temperature sensor data.