JPH0368851A - Road surface condition detector - Google Patents

Abstract

PURPOSE:To detect the condition of a road surface in a cold, snow covered place by alternately applying AC voltages having the different frequencies across a first electrode and a third electrode which are arranged side by side, and detecting the voltage across a second electrode in the vicinity of the first electrode and the first electrode. CONSTITUTION:A nonmagnetic container 7 containing electrodes 4, 5 and 6 is embedded so as to form the same surface as a ground surface 10 such as a road surface. The AC voltage of an AC power source 1 having a frequency F1 and the AC voltage of an AC power source 2 having a frequency F2 are switched with a switch 3 and alternately applied across the electrode 4 and the electrode 6. The voltage generated across the electrodes 4 and 5 is inputted into a voltage-value discriminating circuit 11 having high input impedance through input terminals 12 and converted into the logic values of 1 and 0. The outputs are converted into the signals for the conditions of the various surfaces of the road in a logic circuit 13 for performing logic operation in synchronization with the switch 3. The signals are outputted to output terminals 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a road surface condition detector, which is a type of sensor, used to control road heating, etc. on roads in cold and snowy areas.

(B) Conventional technology Sensors used to detect road surface conditions when controlling road heating, etc. detect changes in electrical resistance of snow, water, ice, etc. between two electrodes;
There are also methods that detect changes in electrical resistance after melting snow, ice, etc. with a heater, and methods that monitor road surface conditions using video cameras, etc., but both of the former two methods use exposed electrodes. There are many problems and shortcomings, such as corrosion of the electrodes, malfunctions due to wear of the electrodes due to passing vehicles, etc., and methods using video cameras, etc., such as reflections from external light and poor accuracy at night. .

(c) Problems to be Solved by the Invention This invention reduces the exposure of electrodes, etc. for detecting road surface conditions to the outside air as much as possible, thereby reducing various problems such as corrosion and abrasion, while preventing snow accumulation, water, etc. The purpose is to skillfully utilize the physical properties of ice, etc. to detect the presence or absence of snow, water, ice, etc. on the road surface, as well as its quantity.

(d) Means for Solving the Problems First, the basic structure of the present invention will be explained based on the drawings as follows. In the first engineering drawing, the king is an AC power source with a frequency of F□, and 2 is an AC power source with a frequency of F2? ! ! Source 3 is a changeover switch, which is connected to electrode 4.6 so that an AC power source with frequency F or an AC power source with frequency F2 can be connected. 4 is 1.2, AC 1! A first electrode connected to the source, 5, is connected to a second f!
! pole, 6 is the third electrode connected to the changeover switch 3, 7
8 is a capacitance formed by the WL electrode and 5, and 9 is formed by electrodes 5 and 6. It is capacitance.

(e) Effect This invention is characterized in that the value of the dielectric constant of air and water hardly changes depending on the frequency of the applied voltage, whereas the value of the dielectric constant of ice changes depending on the frequency of the applied voltage. Therefore, it is an attempt to detect the properties of objects in a target area with high sensitivity by skillfully utilizing phenomena that change considerably.

(Operation when there is air between electrodes 5 and 6) In Fig. 1, the voltage of 1 is VF, and the voltage of 2 is 1.
, but the frequency is different V F z, the capacitance of 8 is C
2 and the value at frequency F2 is C8, the voltage vl between electrodes 4 and 5 when the voltage of 1 is VF, and the voltage between electrodes 4 and 5 when the voltage of 2 is VF2. F2
, is approximately expressed by the following equation.

Vx=VFtX (cz/ (cx+cz))Vz
= V F 2 X (Cs / (Ct + C
s)) Since the dielectric constant of air is approximately 1 and this value does not change with frequency, it becomes Cz '' Cs in the above, and therefore V t '' V z .

(Operation when water exists between fflf45.6) In Figure 1, the voltage of the soil is VF, 2 has the same voltage value as 1, and the capacitance of VF, .
As the capacitance of 9, the value at frequency Fl is 04,
If the value at frequency F2 is C6, the voltage of 1 is V
The voltage F3 between electrodes 4 and 5 for F t, as well as 2
When the voltage of VF is VF, the voltage Vl between electrodes 4 and 5 is approximately expressed by the following equation.

V, = VF engineering X (C4/ (C engineering + 04)) V 4
= V F 2 X (Cs / (Ct + Cs
)) Since the dielectric constant of water is approximately 80 and this value does not change depending on the frequency, C4=Ca in the above, and therefore V a '' V 4 .

(Operation when ice exists between electrodes 5 and 6) In Fig. 1, the voltage of 1 is V F 1.2 is the same voltage value as 1, and the capacitance of V 01.9
Assuming that the capacitance at frequency Fl is C0 and the value at frequency F2 is C7, the voltage of l is VF□
The voltage F5 between electrodes 4 and 5 when the voltage of 2 is VF2, and the voltage F8 between the electrodes 4 and 5 when the voltage of 2 is VF2 are approximately expressed by the following equation.

ya==yFLX (C6/ (Ct+Ca))Vs
``VFgX (C7/ (Ct+Cy)) The value of the relative dielectric constant of ice varies considerably depending on the frequency of the applied voltage, and its value tends to be large in the low frequency region and small in the high frequency region. In this invention, the frequency Fl is from 10 hertz to 1 kilohertz,
1 kHz to 100 kHz as frequency F2,
Since a frequency between the two is used, C8 is several tens of times larger than C7. ■, depends on the values of C and C7, but C and C
Under the condition that 7 is almost equal, ■, will be several times as large as V,.

The above has described the theoretical voltage values between the electrodes 4 and 5 when air, water, and ice are respectively present in the target area to be detected.

(F) Embodiment An embodiment of this invention will be explained based on the drawings. It is. 10 is the ground surface such as a road surface, and 4. is formed so as to form the same surface as this.
A non-metallic container 7 containing 5.6 is buried. 11 is a high input impedance voltage value discrimination circuit, and 12 is its input terminal. 13 is a logic circuit that performs a logical operation based on the input of 1, and 14 is its output terminal. In addition, fallout in the natural world in cold regions during winter includes rain, snow, sleet, hail, etc., and in the following explanation, these will be collectively referred to as snowfall, etc.

As mentioned earlier in the theoretical explanation, depending on the state of the target area, 1! The voltage between the poles 4.5 will exhibit various values. If the road surface is currently dry, that is, if the surface of the container 7 is only air and there is no snow, etc., as described above (
W! , the effect when there is air between the electrodes 5.6), and the voltage between the electrodes 4.5 and 1.2 is approximately V regardless of the frequency.
L = Vz. Next, when the snow on the road surface has melted or when it is raining, this corresponds to the above-mentioned (electrode 5.611 Effect when water is present), and electrode 4.5, The voltage between is 1.2, which is also approximately V3=V, regardless of the frequency. Also, from the above explanation, V1=Vz<V3=V4.

Furthermore, in a state where the melted snow on the road surface is frozen, the voltage at the electrodes 4.5 and 111 corresponds to the effect described above (the effect when ice exists between the electrodes 5.6) and the frequency is 1.2. V5 > V6, and from the above explanation, V5,■, is smaller than V3,■, but Vt,
■It will show a value larger than 2.

The above is a qualitative description of the voltage generated between the electrodes 4.5, and this voltage is converted as follows. That is, fi! [The voltage generated at 4, 5, and ■ is the input terminal 12,
is converted into logical values of l and O by a high input impedance voltage value discriminator circuit, 11. This output is a logic circuit 1 that performs logical operations in synchronization with the switching of the changeover switch 3.
3 is converted into various road surface situation signals by 14
, is output to the output terminal of .

(G) Effects of the Invention The present invention is constructed as described above, and by virtue of its operation, has many excellent effects not found in conventional road surface condition detectors. That is, ■ Since there is no need to expose electrodes, etc. for detecting road surface conditions to the outside air, malfunctions and aging deterioration due to corrosion and wear of electrodes, etc. do not occur.

■ Compared to methods that monitor road conditions using video cameras, etc., there is no influence from outside light and it can be used day or night.

■ Since the entire detector can be configured to be extremely small and lightweight, there are fewer restrictions on where the sensor can be installed.

■ Since the entire detector can be configured to be extremely small and lightweight, the situation near the sensor can be reliably detected without disturbing the state near the sensor that is performing road heating, etc.

■ Since the entire detector can be configured to be extremely small and lightweight, it is inexpensive and has a large economic effect.

■ Since quantitative detection is possible, energy saving effects can be expected by increasing or decreasing the output of snow melting equipment, etc.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining the basic principle of the invention, and FIG. 2 is a block diagram for explaining the invention in detail. DESCRIPTION OF SYMBOLS 1... AC power supply of frequency Fl, 2... AC power supply of frequency F2, 3... Changeover switch, 4... First electrode connected to AC power supply of l, 2, 5...・The second 1 placed near the electrode 4! Poles, 6...Selector switch 3
A non-metallic outer covering, 8, for protecting the third electrode, 7, connected to the electrode 4.5.6 from the intrusion of rain, snow, etc.
・Capacitance formed by electrodes 4 and 5, 9...Capacitance formed by electrodes 5 and 6. 10... Ground surface such as a road surface, 11... Voltage value discrimination circuit with high input impedance,
12...↓1 input terminal, 13...11. Output terminals of logic circuits 14...13 that perform logical operations based on the inputs of.

Claims (1)

[Claims] 1. Two AC voltages with different frequencies are alternately applied between a first electrode and a third electrode that are arranged side by side in an insulator, and the voltage near the top of the first electrode is A road condition detector 2 having a structure having a second electrode disposed in the insulator and configured to detect a voltage between the first electrode and the second electrode. An impedance amplifier detects the voltage between the first electrode and the second electrode, and a discrimination circuit converts the detected voltage value based on two alternating current voltages with different frequencies into a logical value. The road surface condition detector according to claim 1, which is configured to use this logic value to discriminate the state of the target area using a logic circuit.