JP2976025B1 - Road surface condition determination device - Google Patents

Abstract

Provided is a road surface state determination device capable of instantaneously and continuously estimating a friction coefficient of a road surface and accurately determining a road surface state. SOLUTION: The road surface condition determination device includes a detection unit that irradiates an electromagnetic wave to a road surface and detects a reflected wave from the road surface, and detects a water content of a measurement target based on a detection signal detected by the detection unit. Calculate the feature amount according to the content rate of
The state of the road surface is determined by comparing with a reference area value of the feature amount stored in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for determining a road surface condition.

2. Description of the Related Art Conventionally, when the road surface condition of a road is determined, the sliding frictional resistance of the road surface is measured, and the determination is made based on the measured value. Have been. (1) Deceleration method In this method, the vehicle running at the initial speed is braked to lock all the wheels, and the deceleration when all the wheels slide is measured using an accelerometer (deceleration meter). (2) Braking stop distance method In this method, the road surface friction coefficient is calculated based on the distance from the point at which braking is started to the point at which the vehicle stops. (3) Direct measurement method of sliding friction resistance In this method, there are a towed type and a self-propelled towed type, but the measurement principle is the same for both types, and when a special measuring wheel is braked and towed at a constant speed Is measured, and the ratio of the measured force to the wheel load is defined as a sliding friction coefficient. (4) Driving Force Measuring Method In this method, a strain gauge is attached to a driving shaft of a vehicle, and a driving force applied to the driving shaft when the vehicle starts moving is measured from the amount of strain of the strain gauge.

[0003]

Of these four methods, the methods (1), (2) and (4) are used for making a sudden brake on the road or stopping the vehicle at the site for measurement. There is a problem that it may hinder traffic and may be dangerous in tests on slippery roads. Method (1)-
In (4), since the measurement is not always performed, even if the road surface on which the vehicle is currently passing becomes suddenly slippery to the driver who is driving the vehicle, the state changes to a dangerous state.
There is a problem in that it is not possible to collect information about the friction coefficient of the road surface instantaneously and display a warning to the driver of the vehicle.

It is known that the coefficient of friction of a road surface is affected by the road surface condition. For example, the friction coefficient is as shown in Table 1 below.
By observing this, it can be seen that there is a correlation between the road surface condition, that is, the water content based on the magnitude of the water content on the road surface, and the sliding friction coefficient. From this, by detecting the road surface condition and measuring the water content in each road surface condition, it is possible to estimate the sliding friction coefficient of the road surface with high accuracy and determine the road surface condition.

[0005]

[Table 1] In Table 1, the vehicle speed is 50-60 km / h * 1 and the density is 0.25-0.5 * 2 and the density is 0.05-0.15.

An object of the present invention is to measure the water content and the degree of diffusion of light in each road surface condition using the characteristics shown in Table 1 and to estimate a highly accurate road surface friction coefficient. Accordingly, it is an object of the present invention to provide a road surface state determination device which can solve the above-described problems of the conventional art and can instantaneously and continuously accurately estimate a friction coefficient of a road surface to determine a road surface state.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a road surface condition determining apparatus, which irradiates an electromagnetic wave to a road surface and reflects the electromagnetic wave from the road surface. At least two first and second detecting means for detecting a wave, a first comparing means for determining a moisture level on a road surface, and a second comparing means for determining a level of diffuse reflection light on the road surface, wherein the first detecting means The second detecting means detects the wavelength of the non-absorbing band of water, and detects the wavelength of the non-absorbing band of water.
Based on the detection signal detected by the detection means, a feature quantity corresponding to the moisture content of the measurement target and a feature quantity corresponding to the degree of diffusion of light are calculated, and this feature quantity and the first and second comparison means are calculated. The state of the road surface is determined by comparing a reference area value stored in advance.

According to a second aspect of the present invention, in the first aspect, the friction coefficient of the object is estimated from the determination result.

[0009]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, wherein 1 is a first light receiver, 2 is a second light receiver, 3 is a light projector, and as shown in FIG. The light projector 3 is attached to a column 5 established on the side of the road R, and the first and second light receivers 1 and 2 are attached to a support arm 6 attached to the column 5. Reference numeral 4 denotes a road surface state determination processing unit. The determination processing unit 4 amplifies the first reflection signal photoelectrically converted by the first light receiver 1 and a high-frequency signal of the first reflection signal output from the amplifier 7. Comparison data obtained by comparing a low-pass filter 8 that blocks the passage of components to remove noise and a first reflection signal from the low-pass filter 8 with a threshold value described below to determine the water content on the road surface. , And comparators 9 and 10 for outputting.

The discrimination processing section 4 amplifies the second reflected signal photoelectrically converted by the second photodetector 2 and blocks passage of a high-frequency signal component of the second reflected signal output from the amplifier 11. And a comparator 13, 14 for comparing the second reflection signal from the low-pass filter 12 with a threshold value to be described later and outputting comparison data for determining the road surface condition. And

The discrimination processing unit 4 includes comparators 9, 10, 13,
A CPU 15 is provided which outputs a determination result of a road surface state, which will be described later, calculated based on the comparison data output from 14. The determination result output from this is displayed as characters on a display panel (not shown) provided on the upper part of the support 5 to warn the driver of the traveling vehicle.

The light projector 3 is preferably, for example, a mercury lamp that emits light including an emission spectrum of infrared light. The light from the light projector 3 is condensed by an appropriate optical system for collecting the road surface state, and thereafter, is referred to at an appropriate position on the road surface, for example, the center of the road R in the width direction at an arbitrary incident angle. Is projected toward the light emitting road surface. Note that the magnitude of the incident angle does not affect the determination of the road surface state described later.

Next, the operation of this embodiment will be described. The first and second light receivers 1 and 2 respectively receive the first infrared light and the second infrared light of the irregularly reflected light of the light projected from the light projector 3 during the road surface reflection and convert the light into an electric signal. Convert. First
The light receiver 1 has lead sulfide (PbS) as its light receiving element,
Lead selenide (PbSe) is suitable. The first light receiving element having a range of about 1.4 to 2.5 μm
An infrared transmission filter for transmitting infrared light is provided.

The second light receiver 2 preferably has a light receiving element such as a photo diode or a photo transistor. A filter that transmits the second infrared light in a range of less than 1.4 μm is provided on the front surface of the light receiving surface of the light receiving element.

In FIG. 1, a first reflection signal output from a first light receiver 1 is amplified to an appropriate level by an amplifier 7 and then transmitted to a low-pass filter 8, where a high-frequency signal component That is, the disturbance signal component is removed, and the first reflection signal output from the low-pass filter 8 is output to the comparator 9,
10 and is compared here with thresholds A1 and A2. The thresholds A1 and A2 are set according to the presence or absence of moisture, and A1 is a level when the road surface has a large amount of moisture.
2 indicates the level when the water content on the road surface is small. Then, the respective comparison data corresponding to the water content of the road surface obtained by comparing the threshold values A1 and A2, respectively, are as described above.
Input to PU15.

Similarly, the second reflected signal output from the second light receiver 2 is amplified to an appropriate level by the amplifier 11,
Sent to the low-pass filter 12, where the high-frequency signal component,
That is, the disturbance noise component is removed, and the second reflection signal output from the low-pass filter 12 is input to the comparators 13 and 14, where it is compared with the threshold values B1 and B2. The thresholds B1 and B2 are set according to the degree to which light is diffused depending on the road surface condition. B1 indicates the level of the diffused reflected light on the road surface, and B2 indicates the level of the diffused reflected light on the road surface. Then, at the threshold values B1 and B2, respective comparison data corresponding to the degree of light diffusion on the road surface obtained by the comparison are input to the CPU 15 as described above.

In the above case, if necessary, the light source of the light projector 3 may be modulated and transmitted at an appropriate frequency.
The second reflected signal is preferably demodulated after being amplified by the amplifiers 7 and 11. The modulation and demodulation make the first and second reflected signals less susceptible to disturbance.

FIG. 3 is a graph showing the reflectance characteristics of snow. As shown in the figure, the surface of snow shows a diffusion surface having a light reflectance close to 100% with respect to visible light, but the reflectance decreases as the wavelength of light increases, due to absorption by moisture. The solid line in FIG. 3 shows a relative reflectance characteristic curve of the snow surface with respect to the reflectance of barium sulfate when the wavelength is changed. This graph shows the same tendency regardless of the reflection angle. The part where the reflectance of the snow surface approaches zero in the infrared region of 1.4 to 2.4 μm is due to absorption by moisture. For this reason, the degree of reduction in reflectance differs depending on the water content of the snow surface.

The solid line portion in the infrared light region having a wavelength of 1.4 to 2.4 μm shown in FIG. 3 represents dense snow having a high water content (density of 0.25 to 0.5). In contrast, snow, which has a fluffy surface and does not melt, such as fresh snow, has a low moisture content (density 0.
05-0.15), so it looks like a broken line. Even if there is no snow, if the road surface of the road R is in a wet state containing water, the road R changes like a solid line portion or a broken line portion according to the degree of wetness.

When the road surface is dry (dry), the road R
If the road surface is wet (a little or a lot of water),
An example of the result of measuring the level of the output signal of the low-pass filters 8 and 12 for the road surface state of five roads R when there is snow on the road surface of the road R (the snow content is low or high) and this result (Table 2) shows a state in which the output levels are arranged in the order of the magnitudes based on. In this case, the reflected light signal of the infrared light is an average value for the wavelength of 1.4 to 2.5 μm.

[0021]

[Table 2]

As described above, since infrared light is absorbed by moisture, the amount of reflected light is small in snow and wet conditions. In a dry state, the road surface becomes a diffusion surface, so that the output level of the low-pass filter 8 is relatively high. With respect to the second infrared light, if there is snow on the road surface of the road, a diffused surface having a light reflectance of nearly 100% due to snow is formed, so that the output level of the low-pass filter 12 shows a very large value.

On the other hand, in a wet state where the road surface is wet, the road surface is mirror-finished, so that the regular reflection light component increases, but the irregular reflection light component decreases. Therefore, the output level of the low-pass filter 12 has a low value. Since the road surface of the dry road is a diffusion surface having a low light reflectance, the road surface has an intermediate value between snowfall and wetness.

In Table 2, the threshold value A1, which is the discrimination level of the comparator 9, is between the snow level (low water content) 3.3 and the snow level (high water content) 0.8 of the output level of the low-pass filter 8, This is, for example, 2.2. The threshold value A2, which is the discrimination level of the comparator 10, is between the snow cover (small water content) 3.3 and the dryness 5.5, and is set to, for example, 4.4.
When the output level of the low-pass filter 8 exceeds the threshold value A1, the comparator 9 outputs a signal "1" as a determination result.

The comparator 10 outputs a signal "1" when the output level of the low-pass filter 8 is lower than the threshold value A2. Therefore, when the determination result of the comparator 9 and the comparator 10 is “1, 0” based on the information of the first infrared light, it is determined that the state is the dry state. (Small ratio) or wet (a small amount of water). Also,
If it is “0, 1”, it is determined that the snow (large water content) or wet (large amount of water) is present.

Similarly, in Table 3 below, the threshold B1, which is the discrimination level of the comparator 13, is different from that of the low-pass filter
Between the dry reflected 2.0 and wet 0.8 of the second reflected signal level, which is set to, for example, 1.2. Also, comparator 1
The threshold value B2 of 4 is between snowfall 7.5 and dryness 2.0,
Set this to, for example, 4.0. When the level of the second reflection signal from the low-pass filter 12 exceeds the threshold value B1, the comparator 13 outputs a signal "1" as a determination result. When the second reflection signal level of the low-pass filter 12 is less than the threshold value B2, the comparator 14 outputs a signal "1" as a determination result. Therefore, according to the information of the second reflection signal, the judgment result of the comparators 13 and 14 is “1, 0”.
, It is determined to be in a snow-covered state, and "1, 1"
Is determined to be in a dry state. Also, "0,
If it is "1", it is determined to be in a wet state.

[0027]

[Table 3]

The judgment results of the comparators 9, 10, 13 and 14 are sent to the microprocessor 15. The microprocessor 15 determines the final road based on the result of measuring the moisture content of the road surface of the road R based on the information from the first infrared light and the determination result of the road surface state of the road R based on the information from the second infrared light. determination of road surface condition of R is performed based on the combination of Table 4, as shown in Table 4, dried, wet (water small amounts),
It is classified into five types: wet (large water content), snow (small water content), and snow (large water content).

[0029]

[Table 4] The combination in Table 4 is an example, and the comparators 9, 10, 13, 14
Thresholds A1, A2; B1, B2
The combination of Table 4 may be changed by changing the value of.

The final road R is calculated by the CPU 15.
And outputs the estimation result of the road surface friction coefficient as the road surface judgment result. The estimation of the road surface friction coefficient of this road R is shown in Table 1.
As described above, examples of the road surface condition and the friction coefficient of the road R are obtained by determining the magnitude of the moisture in the road surface condition of each road R. Therefore, by comparing Table 1 and Table 4, it is possible to estimate the slip friction coefficient of the road surface. An example is shown in Table 5 below.

[0031]

[Table 5]

The measured values of the road surface friction coefficient have been introduced in a plurality of documents so far, and are important data for estimating the road surface friction coefficient in the present invention. These data also show that the coefficient of sliding friction on the road surface changes depending on the vehicle speed, for example, as shown in “Newly Revised Road Surface Sliding” published by the Technical Research Institute, and this is shown in FIG. For this purpose, it is necessary and possible to make an association with the vehicle speed when estimating the road friction coefficient.

Since the vehicle travels on the road R, the reflected light from the irradiation area of the light projector 3 is blocked every time the vehicle passes through the irradiation area. Generally, the transit time of the irradiation area of the vehicle is short, and the time when the reflected light is not blocked is longer than this. Therefore, the minimum detection time longer than the light blocking time due to the passage of the vehicle is set, and the comparators 9, 10, 13, and
If the output of 14 does not change during this minimum detection time,
It is preferable that the output is taken in by the CPU 15 as a regular signal.

In the above-described embodiment, the data relating to the first reflected signal of the first infrared light is obtained from the average of the light having a wavelength in the range of 1.4 to 2.5 μm. In addition, since the difference between water and water reflectance is remarkable at a wavelength of 1.6 μm or 2.0 μm, it is more preferable to extract only a signal of such a wavelength and use it as data for determining the road surface condition of the road R. .

Further, although irregularly reflected light from the road surface is received, regular reflection light having the same angle of incidence and reflection angle on the road surface may be received to determine the road surface condition of the road R. In this case, the magnitude of the output level in each state of the road surface is as shown in Table 1.
Will be different. Furthermore, by taking in data of the road surface thermometer of the road R and using the wetness level as information including the presence / absence of freezing, the width of the road surface friction coefficient estimation can be expanded.

[0036]

As described above, the present invention is directed to a road surface condition determining apparatus, comprising: at least two first and second detecting means for irradiating an electromagnetic wave onto a road surface and detecting a reflected wave from the road surface; A first comparing means for judging a moisture level and a second comparing means for judging a level of diffuse reflection light on a road surface, wherein the first detecting means detects a wavelength of an absorption band of water; Detecting the wavelength of the non-absorption band,
Based on the detection signal detected by the detection means, a feature quantity corresponding to the moisture content of the measurement target and a feature quantity corresponding to the degree of diffusion of light are calculated, and this feature quantity and the first and second comparison means are calculated. Since the state of the road surface is determined by comparing with a reference region value stored in advance, the effect that the road surface condition can be determined by estimating the friction coefficient of the road surface of the road instantaneously and continuously accurately. There is.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement state at the time of determining a road surface state according to the first embodiment;

FIG. 3 is an explanatory diagram of snow reflectance characteristics in the embodiment.

FIG. 4 is an explanatory diagram showing a relationship between a road surface condition and a sliding friction coefficient in the embodiment.

[Explanation of symbols]

R road 1 first light receiver 2 second light receiver 3 light emitter 4 discriminator 5 support 6 support arm 7,11 amplifier 8,12 low-pass filter 9,10,13,14 comparator 15 CPU

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01W 1/00

Claims (2)

(57) [Claims] At least two first and second detection means for irradiating a road surface with an electromagnetic wave and detecting a reflected wave from the road surface
A first comparing means for determining the moisture level of the road surface;
Second comparing means for determining the level of the diffuse reflected light,
The first detecting means detects a wavelength of an absorption band of water, and a second detecting means.
The stage detects the wavelength of the non-absorption band of water, and, based on the detection signals detected by the first and second detection means, determines the characteristic amount corresponding to the moisture content of the measurement target and the diffusion degree of light. Feature
A road surface state determination unit that calculates the amount of the road surface and compares the characteristic amount with a reference area value stored in advance in the first and second comparison units. apparatus 2. A method for estimating a friction coefficient of an object based on a result of the determination.
Road surface condition determination apparatus according to claim 1, characterized in that it is carried out.