JP3671229B2 - Radio radiometer type road surface condition grasping device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a road surface condition grasping device for a driving support road system (AHS), and more particularly, to a radio radiometer type road surface condition grasping device that performs road surface condition determination by measuring road surface radiation temperature and sky radiation temperature of a radio wave band.
[0002]
[Prior art]
As a road surface condition grasping apparatus for AHS, a 95 GHz millimeter wave radio wave radiometer type road surface condition grasping apparatus has been proposed and its effectiveness has been reported. At the 7th ITS World Conference held in Turin, Italy in 2000, T. Kitano made a presentation titled “Measurement of Snow and Ice Covered on Road by Road Surface Sensor” (3571). In this report, it is reported that the radio radiometer type road surface condition grasping device is extremely effective in distinguishing the road surface conditions of dry, wet, water film, snow cover and freezing.
[0003]
As shown in FIG. 4, a conventional radioradiometer type road surface condition grasping device is a radio wave radiation receiving unit 1 that receives radiation beams 9 'and 9''from a road surface 8, and a rotation that causes the radio wave radiation receiving unit to scan two-dimensionally. It consists of a data processing unit 5a that processes the measurement data in the platform 6 and the radio wave radiation receiving unit 1 and performs road surface determination.
[0004]
This measures the road surface state on the road surface 8, that is, various road surface states such as dryness and wetness, with the energy radiated from the road surface being measured as the radiation temperature. However, it is also necessary to measure the sky radiation temperature in order to calculate the emissivity necessary for road surface condition determination. FIG. 5 shows a state in which the radio wave radiometer-type road surface state grasping device shown in FIG. 4 measures the sky radiation temperature, and the radio wave radiation receiving unit 1 receives and measures the radiation beams 10 ′ and 10 ″ from the sky. In this case, it is necessary to make the angle with respect to the road surface (the angle with the line perpendicular to the road surface, that is, the depression angle), and the angle with respect to the sky (the angle with the line perpendicular to the road surface, that is, the elevation angle) when measuring the road surface radiation temperature. These are all realized by the turntable 6. As shown in Fig. 6, the data processing unit 5a takes in road surface and sky measurement data from the radio wave radiation receiving unit 1 and converts it into a radiation temperature. 11. An emissivity calculation unit 12 that calculates an emissivity from road surface temperature obtained by a different means from a road surface and sky radiation temperature, and a road surface determination unit 13 that determines a road surface state from the emissivity calculation result. In order radiation temperature of the road surface and the sky is to measure the horizontal polarization component and vertical polarization component, the radiation temperature measuring unit 11, both the emissivity calculating unit 12 performs the horizontal polarization component and vertical polarization component.
[0005]
[Problems to be solved by the invention]
By the way, the problem of the conventional radio wave radiometer type road surface condition grasping device is that the emissivity fluctuates in bad weather such as heavy rain and fog, and the error of road surface condition determination is extremely increased.
The reason is that in bad weather such as heavy rain and fog, the road surface radiation temperature and the sky radiation temperature are measured not on the road surface or the sky but in the rain and fog itself, and the measured radiation temperatures on the road surface and the sky are almost equal. The emissivity ε used to determine the road surface condition is
ε = (Tr−Th) / (Ts−Th) ( 2 )
Indicated by Here, Tr is the road surface radiation temperature, Th is the sky radiation temperature, and Ts is the road surface temperature. Equation ( 2 ) shows that when the road surface radiation temperature and the sky radiation temperature are approximately equal, the sky radiation temperature becomes higher than the road surface radiation temperature due to measurement errors and the like, and the emissivity ε may be a negative value. means. In this case, the road surface condition cannot be determined based on the emissivity.
Therefore, the conventional radio-radiometer type road surface condition grasping device has a drawback that a determination error of the road surface condition is likely to occur during bad weather.
[0006]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-described problems, and improves the accuracy of determination of road surface conditions in bad weather as seen in conventional radio wave radiometer type road surface condition grasping devices, and affects the weather conditions. An object is to provide a high-performance radio-radiometer type road surface condition grasping device that does not receive.
[0007]
[Means for Solving the Problems]
In order to achieve the object, the invention described in claim 1 includes a radio wave radiation receiving unit that measures a radiation temperature from a road surface and a radiation temperature from the sky, a turntable that two-dimensionally scans the radio wave radiation receiving unit, A radio-radiometer type road surface condition grasping device including a data processing unit that takes a measurement value transmitted from the radio-wave radiation receiving unit and performs road surface determination, and includes a road surface radiation temperature / sky radiation temperature difference measurement in the data processing unit. And a sky radiation temperature conversion unit. When the absolute value of the difference between the road surface radiation temperature and the sky radiation temperature measured by the difference between the road surface radiation temperature and the sky radiation temperature is less than a certain temperature (K), the sky radiation temperature conversion unit calculates the sky radiation temperature. The value,
Sky radiation temperature = road surface radiation temperature-K ( 1 )
The sky radiation temperature value is uniquely determined. This constant value K is determined in consideration of the road surface determination performance. Usually, it is about 3-10 degreeC.
[0008]
The invention described in claim 2 is characterized in that, in claim 1, visibility data installed outside is input to the sky radiation temperature conversion section of the data processing section. By this data input, a bad weather condition is defined and a constant value K is determined. In this case, the value of K can be determined more finely between 3 and 10 ° C.
[0009]
[Action]
As described above, when the difference between the road surface radiation temperature and the sky radiation temperature is small, the data processing unit measures the difference between the road surface radiation temperature and the sky radiation temperature. By providing a sky radiation temperature conversion unit that uniquely determines the temperature, the reversal phenomenon that the road surface radiation temperature becomes lower than the sky radiation temperature does not occur due to equipment performance fluctuations due to temperature fluctuations, etc., and stable measurement is always possible It becomes. When the difference between the road surface radiation temperature and the sky radiation temperature is large, the road surface radiation temperature / sky radiation temperature difference measurement unit and the sky radiation temperature conversion unit do not function, and the signal is simply passed.
Furthermore, by inputting the data from the visibility meter to the sky radiation temperature converter, the condition of bad weather can be grasped quantitatively, the constant value K used in Equation ( 1 ) can be defined more accurately, and even higher performance radio wave radiation A metered road surface condition grasping device is obtained.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
The basic form is the same as that of a conventional radio wave radiometer type road surface condition grasping device, and will be described with reference to FIG. The radio wave radiation receiving unit 1 that receives the radiation beams 9 ′ and 9 ″ from the road surface 8, the rotating table 6 that scans the radio wave radiation receiving unit two-dimensionally, and the measurement data at the radio wave radiation receiving unit 1 are processed to determine the road surface. This is a post-processing data processing unit that measures the road surface condition on the road surface 8, that is, various road surface conditions such as dryness and moisture, as energy radiated from the road surface as radiation temperature. It is also necessary to measure the sky radiation temperature in order to calculate the emissivity required for this.
[0011]
FIG. 5 shows a state in which the radio wave radiometer-type road surface state grasping device shown in FIG. 4 measures the sky radiation temperature, and the radio wave radiation receiving unit 1 receives and measures the radiation beams 10 ′ and 10 ″ from the sky. In this case, an angle with respect to the road surface (an angle with a line perpendicular to the road surface, that is, a depression angle) and an angle with respect to the sky (an angle with a line perpendicular to the road surface, that is, an elevation angle) when the road surface radiation temperature is measured must be equal. These are all realized by the turntable 6.
[0012]
The embodiment of the present invention is in the configuration of a data processing unit 5 as shown in FIG. The conventional data processing unit 5a takes in road surface and sky measurement data from the radio wave radiation receiving unit 1, converts it into a radiation temperature, a radiation temperature measurement unit 11, and road surface surface temperature obtained by another means from the road surface and sky radiation temperature. 1 includes an emissivity calculation unit 12 that calculates the emissivity from the road surface determination unit 13 that determines a road surface state from the emissivity calculation result. In the present invention, as shown in FIG. 1, the difference between the road surface radiation temperature and the sky radiation temperature is calculated as follows. A road surface radiation temperature / sky radiation temperature difference measuring unit 14 to be measured and a sky radiation temperature converting unit 15 for uniquely determining the value of the sky radiation temperature are provided.
[0013]
In the data processing unit 5 shown in FIG. 1, a road surface radiation temperature / sky radiation temperature difference measuring unit 14 for measuring the difference between the road surface radiation temperature and the sky radiation temperature, and a sky radiation temperature converting unit for uniquely determining the value of the sky radiation temperature. By providing 15, the road surface radiation temperature and the sky radiation temperature are substantially equal during bad weather such as heavy rain and fog, and the difference between them is small. In this case, the sky radiation temperature conversion unit 15 uniquely determines the sky radiation temperature from the road surface radiation temperature.
[0014]
FIG. 2 shows another embodiment. In this embodiment, the data of the visibility meter 16 can be input to the sky radiation temperature conversion section 15 of the data processing section 5. As a result, the value K for determining the sky radiation temperature uniquely from the road surface radiation temperature by the sky radiation temperature conversion unit 15 can be determined more finely.
[0015]
The measurement results of experiments based on the above embodiment will be described with reference to FIGS. These are the data measured by installing at Meishin High Speed Ibuki PA, each (a) is the horizontal polarization emissivity, vertical polarization emissivity, time variation characteristic of emissivity difference of both polarizations, (b) Is the emissivity of the horizontal polarization and the vertical axis is the emissivity fluctuation width characteristic indicating the difference in emissivity between the two polarizations. The data was acquired on August 6, 2001. FIG. 7 shows the measurement result by the data processing unit 5a of the conventional radioradiometer type road surface condition grasping device, and FIG. 3 shows the radio wave radiometer type road surface condition of the present invention. It is a measurement result by the data processing part 5 of an apparatus. In this case, the constant value K is 10 ° C. From these results, it can be seen that both the emissivity time variation characteristic and the emissivity variation width characteristic are markedly improved by the radio wave radiometer type road surface condition grasping device according to the present invention, and the performance improvement is sufficiently exhibited.
[0016]
【The invention's effect】
As described above, according to the present invention, it is possible to improve the accuracy of the determination of the road surface condition during bad weather as seen in the conventional radio-radiometer type road surface condition grasping device. In addition, there is an effect that it is possible to realize a high-performance radio-radiometer type road surface condition grasping device that is not affected by weather conditions.
[Brief description of the drawings]
FIG. 1 is a block diagram of a data processing unit according to an embodiment of the present invention.
FIG. 2 is a block diagram of a data processing unit showing another embodiment.
FIGS. 3A and 3B show measurement results obtained by the radio wave radiometer type road surface condition grasping apparatus according to the present invention, wherein FIG. 3A shows emissivity time fluctuation characteristics, and FIG. 3B shows emissivity fluctuation width characteristics;
FIG. 4 is an external view (road surface radiation temperature measurement) of a conventional radio wave radiometer type road surface condition grasping device.
FIG. 5 is an external view (sky radiation temperature measurement) of a conventional radio wave radiometer type road surface condition grasping device.
FIG. 6 is a block diagram showing a conventional data processing unit.
7A and 7B show measurement results obtained by a conventional radio wave radiometer-type road surface condition grasping device, wherein FIG. 7A shows emissivity time fluctuation characteristics, and FIG. 7B shows emissivity fluctuation width characteristics, respectively.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Radio wave receiving part 5 Data processing part 6 Turntable 7 Pole 8 Road surface 9 ', 9 "Road surface radiation beam 10', 10" Sky radiation beam 11 Radiation temperature measurement part 12 Emissivity calculation part 13 Road surface determination part 14 Road surface radiation temperature -Sky radiation temperature difference measurement unit 15 Sky radiation temperature conversion unit 16 Visibility meter

Claims (2)

A radio wave radiation receiver that measures the radiation temperature from the road surface, the radiation temperature from the sky,
A turntable for two-dimensionally scanning the radio wave radiation receiving unit;
The radio wave radiation receiving unit has a road surface radiation temperature / sky radiation temperature difference measurement unit that measures a difference between a road surface radiation temperature and a sky radiation temperature, and a sky radiation temperature conversion unit that uniquely determines a sky radiation temperature value. A radio radiometer type road surface condition grasping device comprising:
When the absolute value of the difference between the road surface radiation temperature and the sky radiation temperature measured by the road surface radiation temperature / sky radiation temperature difference measurement unit is equal to or lower than a certain temperature, the sky radiation temperature conversion unit A radio wave radiometer type road surface condition grasping device characterized in that a value is calculated from equation (1) .
(Expression 1) Sky radiation temperature = road surface radiation temperature−K (1)
Where K: constant temperature The radio radiometer type road surface condition grasping device according to claim 1, wherein the sky radiation temperature conversion unit of the data processing unit is input with visibility data installed outside.

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