JP2000048294A - Road surface state detecting method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the constitution, to widen the detection range, and to lower the cost by deciding a road surface state according to the water film thickness found by substituting meteorological quantities measured by meteorological sensors installed nearby the road in specific relational expressions. SOLUTION: The meteorological sensor consisting of a thermometer 1, a rain gauge 2, and a pysheliometer 3 are installed nearby the road 4. Meteorological data obtained by the sensors 1 to 3 are transmitted to an information gathering device 7. A road surface state decision device 8 performs a road surface deciding processing based upon those meteorological data and outputs the result to a display device 9. The decision device 8 decides the road surface state according to the water film thickness t' found by substituting those meteorological data in the relational expressions, i.e., water film thickness t=f (rainfall, road surface coefficient) and t'=t-(k0.N(1-R)+Q1+V1.(T0-Tx)). Here, N is the solar radiation quantity, R an albedo (reflection factor of road surface), Q1 sensible heat of water, V1 a wind velocity, T0 air temperature, Tx water temperature, and k0 a constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting road surface conditions such as dryness, wetness / water film, snow cover, freezing and the like.

[0002]

2. Description of the Related Art Maintenance of expressways and general roads is progressing, and a road network is spreading all over the country. These roads have rain, snow,
Alternatively, if freezing or the like occurs, a slip accident is likely to occur.
For this reason, it is considered important to develop a sensor that promptly detects the road surface condition such as the degree of wetness of the running road surface and the presence or absence of freezing, informs the driver of the running vehicle of the information, and alerts the driver. Conventionally, there has been a non-contact type road surface state detection sensor as a sensor developed specifically for the purpose of realizing such needs.

FIG. 8 is a conceptual configuration diagram of the above-mentioned conventional non-contact type road surface state detection sensor. This sensor is an infrared sensor, and a support column 51 installed on the shoulder of the road,
A temperature measuring device 53 (typically an infrared radiation thermometer) for measuring the surface temperature of a road surface 52 attached to the horizontal portion 51a of the support pillar 51; an infrared projector 54 and an infrared receiver 55;
Road surface reflection ratio meter 56 that measures infrared reflection ratio
And a wet / freeze determination output device 57 for determining the road surface condition based on information from the temperature measuring device 53 and the road surface reflection ratio meter 56.

[0004] Such a road surface condition detecting sensor is provided on a road surface 52.
Is irradiated with infrared rays 58, and the ratio of the component (reflected wave) 59 that does not return to the incident direction of the reflected wave from the road surface 52 and the component (diffusely reflected wave) 60 that returns to the incident direction is determined, and the wet / freeze is obtained. The determination output device 57 calculates the degree of wetness of the road surface 52 (the degree of wetness of the road surface is grasped by the magnitude of this ratio), and furthermore, the temperature value obtained by measuring the amount of infrared radiation from the road surface 52 with the temperature measuring device 53 The condition of the road surface is detected from the data and the degree of wetness.
For example, when the surface temperature of the road surface 52 is below the freezing point and the road surface 52 is wet, the wet / freeze determination output device 57 determines that the surface is “freeze”.

[0005] However, the conventional road surface state detection sensor described above has the following problems. (1) The irradiation range of infrared rays is narrow, and the detection range is limited. (2) When applied to the detection of a wide range of road surface conditions such as a long road and a multi-lane road like an actual road, a plurality of road surface condition detection sensors are required. costly.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and can detect a road surface condition with a simple structure, and has a wide detection range and can be reduced in cost. It is an object of the present invention to provide a simple road surface state detecting method and its device.

[0007]

According to a first aspect of the present invention, there is provided a method for detecting a road surface state, comprising the steps of: measuring a weather sensor including a thermometer, a rain gauge, a pyranometer, etc., installed near a road; The road surface condition is determined based on the weather amount and a relational expression between the weather amount and the road surface condition which is obtained in advance.

According to a second aspect of the present invention, there is provided a road surface condition detecting device including a thermometer, a rain gauge, a pyranometer, and the like installed near a road, and a meteorological sensor for measuring a weather amount near the road, and a meteorological sensor for measuring the weather amount near the road. And a road surface state determination device that determines a road surface state based on a relational expression between the obtained weather amount, a previously obtained weather amount, and a road surface condition.

[0009]

An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral A denotes a road surface condition detecting device, which includes a thermometer 1, a rain gauge 2, a pyranometer 3, and the like installed near a target road 4, and a weather sensor for measuring a weather amount near the road. A signal transmission device 5 for transmitting weather data (meteorological amount) measured by the weather sensors 1, 2, 3 to an information collecting device 7 via a signal line 6, and various sensors 1 and 2 transmitted from the signal transmission device 5; An information collection device 7 that receives, collects, manages, and stores the weather data from the devices 2 and 3; a road surface determination device 8 that performs a road surface determination process based on the weather data received by the information collection device 7; The display device 9 outputs and displays the result.

In order to detect the road surface condition in the above-described configuration, the road surface condition is measured by the weather sensors 1, 2, 3 and the information collecting device 7
The road surface condition determination device 8 determines the road surface condition based on the weather data (meteorological amount) input to the road surface condition determination device 8 via the PC and a relational expression between the weather amount and the road surface condition which is obtained in advance. Performed by Specifically, the measured weather data is substituted into a relational expression to determine the road surface condition.

An example of the relational expression is shown below. That is, the water film thickness t (mm) at the time of rainfall can be generally expressed in the form of t = f (precipitation, road surface coefficient). The following empirical formula is determined for the water film thickness. t = A ₀ [T ^B0 L ^C0 I ^D0 S ^E0 ] Here, T: average roughness of road surface (degree of unevenness) (mm), L: distance until drainage (mm), I: precipitation (mm / hr) S: slope of the road (angle) a ₀ ~E _0: a constant. The parameters other than the precipitation I are determined by the state of the road to be measured. In this device, these parameters are determined in advance. Further, the water film thickness t partially evaporates and partially scatters and decreases due to the road environmental meteorological amount (temperature, solar radiation, wind speed, etc.), and is corrected using a thermal model taking these meteorological amounts into account. I do. Water film thickness t 'obtained by correction
Can be expressed as t '= f (water film thickness t, temperature, solar radiation, wind speed, humidity, road surface coefficient). In other _{words, t '= t- (k 0} · N (1-R) + Q 1 + V 1 · (T 0 -T
_X )), where N: solar radiation (KJ / m ² · min) R: albedo (reflectance of road surface) Q ₁ : sensible heat of water (Cal / m ² · min) V ₁ : wind speed (m / s) T ₀ : air temperature (° C.) T: water temperature (° C.) k ₀ : constant.

FIG. 2 is experimental data showing the relationship between elapsed rainfall time and water film thickness on an asphalt road surface. This data simulates almost the same inclination angle as a normal road surface, and it can be seen that when the rainfall time has sufficiently passed, the road surface water film thickness does not depend on the rainfall intensity and becomes a substantially constant value.
In addition, even before the road surface wetness is saturated, the road surface water film thickness can be shown as a function of the precipitation intensity and the elapsed time. In addition, on actual roads, there are road surfaces with deformed surfaces, such as the surface material, the degree of unevenness, and the rutting generated on the road surface. The water film thickness can be detected.

FIG. 3 is experimental data showing the relationship between the amount of snowfall and the thickness of snow. This result shows that there is a proportional relationship between the amount of snowfall and the thickness of the snow, and the thickness of the snow can be obtained from the amount of snowfall. However, this graph is data at a constant snow water ratio (ratio of snow depth to precipitation), and the proportional relationship changes as the snow water ratio changes.

FIG. 4 is experimental data showing the relationship between air temperature and snow water ratio. By using this result, the snow water ratio is uniquely determined by the outside air temperature, so first determine the snow water ratio by measuring the outside air temperature, select a proportional coefficient, and then use this proportional constant to calculate the snowfall amount. Judge the snow thickness.

Freezing is determined based on the time-dependent characteristics of the road surface temperature and the degree of road surface wetness. FIG. 5 shows the result obtained by experimenting the temporal change (trend) of the road surface temperature during freezing, in which the road surface was wetted beforehand. As a result, a phenomenon occurs in which the road surface temperature becomes constant because the water solidifies during freezing. This device detects this phenomenon only with weather data. That is, the road surface temperature is obtained by heat calculation in consideration of heat transfer between the outside air and the road surface and heat conduction inside the road surface from the air temperature and the amount of solar radiation. The road surface wetness is determined from the amount of precipitation or snowfall based on the above-described relationship. By comparing the calculated road surface temperature trend and the degree of wetness, for example, if the degree of wetness is large as shown in FIG. Conversely, even when the outside temperature rises and the freezing is released, it can be similarly determined that the freezing is released. Here, the road surface temperature can be calculated from the air temperature and the amount of solar radiation, but may be measured directly by a temperature sensor.

On the other hand, the detection range necessary for detecting the road surface condition from the meteorological amount by using these methods is determined by the relationship between the braking distance until the vehicle stops and the case where the speed limit of the vehicle is controlled from the road surface condition. It is known that it is necessary to output the average value of about 100 m section on expressways and about 50 m section on general roads. This device adopts this idea, and the measured meteorological quantity is constant within this detection range. Given that there is, output the average state.

The weather sensors 1, 2, 3 are not particularly limited as long as they can provide an electrical output. Further, a wireless transmitter may be used as the signal transmission device 5, and the configuration in that case is shown in FIG. 6 as another embodiment. The receiving antenna 6a is used instead of the signal line. The information collecting device 7 receives the information from the weather sensor and gives necessary data to the road surface condition determining device 8 in consideration of the type of data, delay time, and the like. The road surface condition determination device 8 determines the water film thickness (wetness) of the road surface from the amount of precipitation, the snow thickness of the road surface from the amount of snowfall, and the presence or absence of freezing from the road surface temperature and the road surface wetness.

FIG. 7 shows still another embodiment. In this embodiment, the weather sensors 1, 2, and 3 transmit their outputs to a signal transmission device 5 through an optical fiber 6b. The optical fiber 6b is buried on the road side at a depth of several cm, and its signal is analyzed by the signal transmission device 5. Road surface condition determination device 8
Performs calculation and determination of the road surface state based on information from the signal transmission device 5. That is, in the embodiment, the temperature distribution on the optical fiber surface (continuous temperature along the optical fiber) is measured, and the road surface temperature is easily measured by laying the optical fiber 6b close to the road surface. it can. In addition, by laying the optical fiber 6b along the road over a long distance, a continuous road surface temperature along the road can be measured, and the determination of freezing can be continuously performed.

In this embodiment, two sets of weather sensors 1, 2, 3 and a signal transmission device 5 are installed along the road 4, and these are connected to an information collection device 7 and the like via a signal line 6.
Needless to say, three or more sets of the weather sensors 1, 2, 3 and the signal transmission device 5 may be installed. Further, the design of the detailed configuration can be changed or modified as appropriate within the scope described in the claims at the time of implementation.

[0020]

According to the first and second aspects of the present invention, since the above configuration is employed, the road surface condition can be detected with a relatively simple configuration as compared with the conventional sensor system, and the detection range is also reduced. wide. In addition, in order to continuously detect the road surface condition of long-distance roads, it is only necessary to install a weather sensor, so an excellent effect that a device that is significantly lower in cost than a device using a conventional sensor can be realized. There is.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between elapsed rainfall time and water film thickness.

FIG. 3 is a graph showing a relationship between a snowfall amount and a snow thickness.

FIG. 4 is a graph showing a relationship between a temperature and a snow-water ratio.

FIG. 5 is a graph showing a temporal change (trend) of a road surface temperature during freezing.

FIG. 6 is a conceptual configuration diagram showing another embodiment.

FIG. 7 is a conceptual configuration diagram showing still another embodiment.

FIG. 8 is a conceptual configuration diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermometer (weather sensor) 2 Rain gauge (weather sensor) 3 Pyranometer (weather sensor) 5 Signal transmission device 6 Signal line 6a Receiving antenna 6b Optical fiber 7 Information collecting device 8 Road surface condition judging device 9 Display device

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[Procedure amendment]

[Submission date] July 22, 1999 (July 7, 1999
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

[0007]

According to a first aspect of the present invention, there is provided a method for detecting a road surface state, comprising the steps of: measuring a weather sensor including a thermometer, a rain gauge, a pyranometer, etc., installed near a road; relationship t of the weather amount and the road surface conditions obtained in advance the weather amount _{'= t- (k 0 · N} (1-R) + Q 1 + V 1 · (T 0 -T
_X )), where N: solar radiation (KJ / m ² · min) R: albedo (reflectance of road surface) Q ₁ : sensible heat of water (Cal / m ² · min) V ₁ : wind speed (m / s) T ₀ : Air temperature (° C.) T _X : Water temperature (° C.) k ₀ : A road surface state detection method characterized by determining a road surface state from a water film thickness t ′ obtained by substituting into a constant.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

According to a second aspect of the present invention, there is provided a road surface condition detecting device including a thermometer, a rain gauge, a pyranometer, and the like installed near a road, and a meteorological sensor for measuring a weather amount near the road, and a meteorological sensor for measuring the weather amount near the road. the weather amount obtained in advance the weather amount and the relationship t of the road surface condition _{'= t- (k 0 · N} (1-R) + Q 1 + V 1 · (T 0 -T
_X )), where N: solar radiation (KJ / m ² · min) R: albedo (reflectance of road surface) Q ₁ : sensible heat of water (Cal / m ² · min) V ₁ : wind speed (m / s) T ₀ : air temperature (° C.) T _X : water temperature (° C.) k ₀ : a road surface condition determination device for determining a road surface condition from a water film thickness t ′ obtained by substituting into a constant Detection device.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

An example of the relational expression is shown below. That is, the water film thickness t (mm) at the time of rainfall can be generally expressed in the form of t = f (precipitation, road surface coefficient). The following empirical formula is determined for the water film thickness. t = A ₀ [T ^B0 L ^C0 I ^D0 S ^E0 ] Here, T: average roughness of road surface (degree of unevenness) (mm), L: distance until drainage (mm), I: precipitation (mm / hr) S: slope of the road (angle) a ₀ ~E _0: a constant. The parameters other than the precipitation I are determined by the state of the road to be measured. In this device, these parameters are determined in advance. Further, the water film thickness t partially evaporates and partially scatters and decreases due to the road environmental meteorological amount (temperature, solar radiation, wind speed, etc.), and is corrected using a thermal model taking these meteorological amounts into account. I do. Water film thickness t 'obtained by correction
Can be expressed as t '= f (water film thickness t, temperature, solar radiation, wind speed, humidity, road surface coefficient). In other _{words, t '= t- (k 0} · N (1-R) + Q 1 + V 1 · (T 0 -T
_X )), where N: solar radiation (KJ / m ² · min) R: albedo (reflectance of road surface) Q ₁ : sensible heat of water (Cal / m ² · min) V ₁ : wind speed (m / s) T ₀ : air temperature (° C.) T _X : water temperature (° C.) k ₀ : constant.

Claims (2)

[Claims] 1. A road surface condition is determined based on a weather amount measured by a weather sensor including a thermometer, a rain gauge, a pyranometer, and the like installed near a road, and a relational expression between the weather amount and the road surface condition obtained in advance. A road surface state detection method, comprising: determining. 2. An apparatus for detecting a road surface condition such as a wet leap degree of a road surface and the presence or absence of freezing, comprising: a thermometer installed near a road;
A weather sensor consisting of a rain gauge, a pyranometer, etc., which measures the weather amount near the road, and a road surface condition based on a relational expression between the weather amount measured by the weather sensor and a previously obtained weather amount and a road surface condition. A road surface state detection device, comprising: a road surface state determination device for determining.