JP3050759B2 - Road condition detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the condition of a road surface in real time by an unmanned facility using ultrasonic waves. It is used for an information system that informs and a centralized monitoring system for roads.

[0002]

2. Description of the Related Art In recent years, with the development of so-called motorization in Japan, it has become one of the important social problems to ensure safe driving of automobiles. To this end, road managers constantly monitor and maintain the state of roads accurately, prevent and prevent traffic accidents in some cases, and provide drivers with information on road surface conditions in real time. It is necessary to ensure safe and smooth traffic. 2. Description of the Related Art Conventionally, patrols for directly monitoring road conditions are generally performed by personnel.

[0003] However, the patrol by the above-mentioned personnel requires a great deal of labor, time and cost, so that it is difficult to frequently monitor road conditions. In particular, patrols at night, in bad weather, or in mountainous areas often involve dangers, and in urban areas or arterial roads, there is a possibility that patrols may not be sufficiently performed due to traffic congestion. Therefore, in order to obtain real-time information in response to changes in various conditions such as weather, a remote-controlled television camera is installed at a key point, and a monitoring system that measures temperature, wind direction, and wind speed is adopted. .

[0004]

However, the above-described conventional monitoring system judges the image transmitted to the central control room through the television camera mounted at a relatively high position from the monitor screen, so that the road surface condition can be accurately determined. It can be difficult to figure out. Especially at night or in bad weather,
There was a problem that detailed information such as whether the road surface was wet, frozen, and the snow condition could not be obtained. Also, merely measuring the temperature can only estimate the possibility of road surface freezing.

Therefore, the road surface state detecting method of the present invention has been made in view of the above-mentioned conventional problems, and its purpose is to cover a wide area / road network.
Road conditions can be grasped accurately and in real time, and traffic accidents can be effectively prevented.In addition, unmanned facilities can be used to safely and labor-saving to achieve centralized management of roads at low cost. An object of the present invention is to provide a method for detecting a road surface condition.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and its contents will be described below with reference to the embodiments shown in the drawings.

According to a first aspect of the present invention, there is provided a road surface state detecting method, wherein ultrasonic waves are emitted toward a road surface, ultrasonic waves reflected from the road surface are received and the reflectance thereof is measured, and the temperature of the outside air is measured.
Compensate the acoustic impedance of air by the outside air temperature,
Characterized in that detecting the acoustic impedance of <br/> road from the acoustic impedance of air after compensation with the reflectance, consisting process determines the road surface condition based on the sound <br/> sound impedance of the detected road surface And

According to a second aspect of the present invention , in addition to the features of the first aspect, the determination of the road surface state is performed by
Process the detected acoustic impedance is compared with a plurality of reference acoustic impedance which is set in advance for the road surface condition
It is characterized by consisting of .

Furthermore, the road surface condition detection method according to claim 3 wherein the step of the measurement of the reflectance, measured energy of the ultrasonic wave received, obtains the ratio of ultrasonic energy when fired toward the road surface It is characterized by consisting of .

According to a fourth aspect of the present invention, there is provided a road surface state detecting method, comprising: receiving an ultrasonic wave reflected from a road surface; measuring a distance from a position where the ultrasonic wave is emitted or received to a position where the ultrasonic wave is reflected; The method may further include comparing the measured distance with a distance from a launch position or a reception position of the ultrasonic wave to a road surface.

A road surface state detecting method according to a fifth aspect is characterized in that ultrasonic waves are emitted intermittently and in a short time.

[0012]

First, the basic principle of the road surface condition detecting method according to the present invention will be described below with reference to FIG. Conventionally, it is known that each substance has a unique acoustic impedance. For example, according to the 1994 scientific chronology (edited by National Astronomical Observatory of Japan and published by Maruzen), the acoustic impedance of air, water, and ice is 428. ⁶ , 1.50 × 10 ⁶ ,
2.96 × 10 ⁶ Nsm ⁻³ . In FIG. 1, an ultrasonic wave 2 emitted from above toward a road surface 1 propagates through the air and is reflected by the road surface or by a material 3 when there is any substance on the road surface. This reflectance R
Is the energy E of the reflected ultrasonic wave 4 with respect to the intensity of the emitted ultrasonic wave, that is, the energy Ed, as in the following equation 1.
It is obtained as the ratio of e.

[0013]

(Equation 1)

In general, the acoustic impedance is equal to the product of the density of the medium and the speed of sound, so that the acoustic impedances of the air and the road surface are Z1 and Z2, respectively, and the density is ρ
Assuming that 1,1, .rho.2, and sound velocity are c1, c2, respectively, the following equation 2 is obtained.

[0015]

[Equation 2] Z1 = ρ1 · c1, Z2 = ρ2 · c2

Here, there is a relationship between the acoustic impedances Z1, Z2 and the reflectance R as shown in the following equation (3).

[0017]

(Equation 3)

The acoustic impedance Z1 of the air can be treated as substantially constant if the sound speed c1, which slightly varies depending on the temperature, is compensated for by temperature. Therefore, the acoustic impedance Z2 of the road surface can be obtained from the reflectance R according to the following equation (4). it can.

[0019]

(Equation 4)

As described above, since the acoustic impedance differs depending on the substance, it is possible to determine whether there is any substance on the road surface or what exists based on the value of Z2 obtained from the reflectance R.

Therefore, according to the road surface state detecting method of the present invention, the reflectance of the ultrasonic wave emitted toward the road surface is measured.
To obtain the acoustic impedance of the road surface
Changes the speed of sound propagating in the air,
Changes in the dance
Calculates the speed of sound in the air at the air temperature and calculates the acoustic impedance of the air
Of the material on the road surface by temperature compensation
If the presence or absence of a substance is detected on the road surface,
Increase the acoustic impedance of the material at that ambient temperature.
Since the measurement can be performed with high accuracy, the substance can be specified. Also, depending on the outside air temperature, for example, 0 ° C. or more,
Used as auxiliary data to judge whether the road surface is frozen.
Can be

Further, according to the road surface state detecting method of the present invention, a reference acoustic impedance corresponding to the detected acoustic impedance is selected from a plurality of reference acoustic impedances preset for various assumed road surface conditions. With the determination, the determination of the road surface condition is easily performed.

According to the road surface state detecting method according to the third aspect, since the energy of the ultrasonic wave received by using the prior art can be easily measured, the reflectivity of the ultrasonic wave on the road surface, and therefore, the acoustic impedance can be relatively simplified. Can be sought.

According to the road surface condition detection method according to claim 4, wherein the distance from the firing position or reception position of the ultrasonic to the road surface, the distance because they proved constant and advance until the road surface by measurements If it has changed significantly,
The presence of obstacles such as falling rocks and the presence of vehicles can be known together with the measurement results of the reflectivity of the ultrasonic waves.

According to the road surface state detecting method of the fifth aspect, the SN ratio in the measurement result can be increased by shortening the ultrasonic radiation time.

[0026]

FIG . 2 schematically shows a configuration of a monitoring system for detecting a road surface condition by the method of the present invention. The monitoring system includes a transmitter / receiver 13 supported on the tip of an arm of an L-shaped column 12 suspended from a side of a monitoring point on a road 11. The transducer 13 is configured to emit and receive ultrasonic waves by a known technique, and to measure the intensity, that is, the energy of the received ultrasonic waves. It is convenient to use, for example, a PLL or feedback control in the transmission circuit of the transducer 13 in order to stably maintain the transmission frequency. The output of the calculating means 14 is connected to a determining means 15 comprising a memory storing data storing acoustic impedance as a reference for determining a road surface condition and a CPU. The calculating means 14 is composed of, for example, a microcomputer common to the determining means 15 and
Can be provided integrally with the monitoring system, or can be arranged in a central control room or the like of the monitoring system. A thermometer 16 for measuring the temperature of the outside air at the monitoring point is attached to the support 12, and is electrically connected to the calculating means 14.

According to the method of the present invention, as shown in the flowchart of FIG. 3 , first, an ultrasonic wave having a predetermined frequency and intensity is emitted downward and vertically from the transmitter / receiver 13 toward the road surface 11 (step S1). . The emitted ultrasonic waves 17 are reflected by the road surface 11 and received by the transmitter / receiver 13, which measures the energy of the received ultrasonic waves 18 (step S).
2). The measured energy value of the received wave 18 is sent to the calculating means 14 via the line 19. The calculation means 14 calculates the reflectivity of the ultrasonic wave on the road surface 11 according to the above-described formula 1 (step S3). Further, the calculating means 14 calculates the acoustic impedance of the road surface using the calculated reflectance according to Equation 4 described above (step S4). At this time, using the outside air temperature input from the thermometer 16 via the line 20, the sound speed at the time of calculating the acoustic impedance is temperature compensated. Thereby, a more accurate value of the acoustic impedance can be obtained.

The acoustic impedance of the road surface obtained in this way is output to the judgment means 15. The determination means compares the input acoustic impedance measurement value with a reference acoustic impedance in the memory,
For example, (a) dry, (b) wet,
(C) Snow cover, (d) sherbet-like, or (e) ice-burn and more specifically classify and determine (step S5). At this time, the outside air temperature input from the thermometer 16 is used as an auxiliary temperature to judge whether the road surface 11 is frozen by judging whether the temperature is higher or lower than an appropriate temperature, for example, 0 ° C. as a threshold. be able to.

The reflected wave 18 received by the transducer 13
From the transmitter / receiver or the arithmetic means 1 using a known technique.
4, the distance from the transducer 13 to the road surface 11 can be measured. Since the transducer 13 is attached to the fixed position of the support 12 and the distance to the road surface 11 is known in advance, if the measurement distance by the ultrasonic wave becomes shorter than that, the transmitter / receiver 13 is mounted on the road surface at the time of measurement. Rock fall
It is possible to determine the presence of obstacles such as falling objects and vehicles, and to know the amount of snow when snow is covered. Ultrasonic waves are emitted intermittently and in a short time from the transmitter / receiver 13 in order to measure the distance to the reflecting surface. When the energy of the reflected wave is measured by such a transmitting method, the SN ratio is increased. Is preferred because it can be improved.

The judging means 15 outputs the judgment result of the road surface state obtained in this way to, for example, the above-mentioned display device in the central control room or the display means provided at a key point on the road (step S6). As a result, more detailed road surface information is transmitted to the road manager and the driver in real time as compared with the related art, so that the vehicle can travel more safely. Further, in the above-described embodiment, the determination unit determines the road surface condition based on the measured acoustic impedance of the road surface.In another embodiment, the value of the acoustic impedance is output to the display device as it is, and is directly output to the display device, for example. The road condition can also be determined by the observer by comparing the data table with the reference acoustic impedance data table.

Although the preferred embodiment of the present invention has been described in detail above, it is understood that the road surface state detecting method according to the present invention can be implemented in the technical scope thereof with various modifications and alterations to the above embodiment. It can be easily understood by those skilled in the art.

[0032]

Since the present invention is configured as described above, it has the following effects. According to the road surface state detection method of the present invention, by determining the acoustic impedance of the road surface from the reflectance of the ultrasonic wave reflected on the road surface, it is possible to specify the substance present on the road surface, so that the substance is, for example, By identifying whether it is water, ice, or snow,
Even on mountain roads or at night or in bad weather, patrols can be used to monitor road conditions at low cost due to unmanned, safe and labor-saving without actually checking the site by humans. Or wet or
It is possible to accurately and in real time know whether the vehicle is frozen or snow-covered and the degree of snow-covering / freezing, thereby ensuring safe driving of the vehicle at all times.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a basic principle of a road surface state detection method according to the present invention.

FIG. 2 is a diagram schematically showing a configuration of a monitoring system for implementing a road surface state detecting method of the present invention.

FIG. 3 is a flowchart of a road surface state detection method using the device of FIG. 2 ;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Road surface 2 Ultrasonic wave 3 Substance on road surface 4 Ultrasonic wave 11 Road, road surface 12 Prop 13 Transceiver 14 Calculation means 15 Judgment means 16 Thermometer 17 Ultrasonic wave 18 Received wave 19, 20 lines

Continuation of the front page (72) Inventor Tsuyoshi Sato 1-22-14-503 Minami Kusuba, Hirakata-shi, Osaka (56) References JP-A-3-68851 (JP, A) JP-A-7-113877 (JP, A Japanese Utility Model Showa 62-137735 (JP, U) Japanese Patent Publication 45-11273 (JP, B2) Japanese Patent Publication 45-12622 (JP, B2)

Claims (5)

(57) [Claims] An ultrasonic wave is emitted toward a road surface, the ultrasonic wave reflected from the road surface is received and its reflectance is measured, the temperature of outside air is measured, and the acoustic impedance of air is measured according to the outside air temperature. And detecting the acoustic impedance of the road surface from the reflectance and the acoustic impedance of the air after the compensation, and determining a road surface state based on the detected acoustic impedance of the road surface. Road surface condition detection method. 2. The road surface state detection method according to claim 1, wherein the determination of the road surface state includes a step of comparing the detected acoustic impedance with a plurality of reference acoustic impedances preset for the road surface state. . 3. The method of claim 1, wherein measuring the reflectivity comprises measuring the energy of the received ultrasonic waves and determining a ratio of the ultrasonic waves to the energy when the ultrasonic waves are emitted toward the road surface. The road surface state detection method according to claim 1 or 2. 4. The ultrasonic wave reflected from the road surface is received, and a distance from a position where the ultrasonic wave is emitted or received to a position where the ultrasonic wave is reflected is measured. 4. The road surface state detecting method according to claim 1, further comprising a step of comparing a distance from a launch position or a receiving position to the road surface. 5. The road surface state detecting method according to claim 1, wherein the ultrasonic waves are emitted intermittently and in a short time.