RU2552272C1 - Method of determining state of road surface - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: inspected section of the road surface is probed by electromagnetic waves, the electromagnetic waves reflected from this surface section are received, the phase shift between the falling and reflected waves or change of amplitude (power) of the received waves is determined with reference to their values for the falling waves, respectively, the main phase shift of these waves or the main change of amplitude (power) of these waves in absence of the covering layer on the road surface is determined. A passive reflector of the falling electromagnetic waves reflecting them in the direction opposite to the direction of the probing waves is buit-in into the surface layer of the inspected section of the road. The sounding is performed by the fixed frequency electromagnetic waves at some angle other than a right angle, and by the size of additional phase shift with reference to the main phase shift or additional change of amplitude (power) of the received waves with reference to the main change of amplitude (power) of these waves the state of the road surface is obvious.

EFFECT: higher accuracy.

4 cl, 5 dwg

Description

The invention relates to measuring technique and can be used for non-contact determination of the state of the surface of the roadway, which may form a layer of water, snow or ice.

There are various methods for determining the condition of road surfaces, based on various principles and related to the measurement of electrical capacitance (US 5398547, 03.21.1995), electrical conductivity and resistance (US 4745803, 05.24.1988; US 4287472, 09.09.1981), using ultrasound waves (US 5095754, 03.17.1992), light waves, in particular infrared radiation, etc. (Winter B. Sensoren warnen vor Wasser oder Eis auf der Strasse // Sensor magazine. 1998. N.2. P. 8). However, they have certain disadvantages: some of them are contact methods and are characterized by wear of the components of the applied measuring devices, associated with the use of communication lines between sensors and electronic units; other methods, being non-contact, are sensitive to weather conditions and cannot determine the thickness of the water layer.

Microwave methods for determining the state of pavement are also known (US 4690553, 09/01/1987; US 5686841, 11/11/1997; Hertl S., Schaffar G., Stori H. Contactless determination of the properties of water films on road // Journal of Physics E .: Scientific Instruments. 1988. Vol.21. N.10. P. 955-958). These methods and devices that implement them allow you to make non-contact measurements, determine and identify the presence of water, snow or ice on the surface of the roadway and measure their thickness. However, the known methods have a significant drawback: they do not provide high accuracy in measuring the thickness of a layer of a substance (water, snow or ice), which can be very thin. In addition, these methods are quite complex and have a high implementation cost.

There is also known a method (US 5497100, 03/05/1996), which consists in sensing the road surface with frequency-modulated electromagnetic waves, receiving reflected waves, obtaining a set of values of the amplitudes of the difference signals corresponding to the received and emitted waves, comparing this set with many known surface models and determining the condition of the road based on the results of this comparison. This method is characterized by low accuracy and difficult to implement: the process of obtaining useful information is associated with complex functional processing of the received signals.

A technical solution is also known (RU 2473888 C1, 01/27/2013), which, by its technical nature, is closest to the proposed method and is adopted as a prototype. This prototype method consists in sensing the road surface with frequency-modulated electromagnetic waves, receiving reflected waves, embedding a resonator in the surface layer of the controlled section of the road with a resonant frequency of electromagnetic waves that changes in accordance with the state of the road, which excite sounding electromagnetic waves in it, measuring the power of the reflected from the resonator and the received electromagnetic waves and judgment on the state of the road surface by the magnitude of the frequency, respectively the minimum received power. The frequency range of the sounding electromagnetic waves is selected from the condition that it exceeds the range of possible values of the resonant frequency of the resonator corresponding to the determined state of the road surface.

This method, like the above methods, is difficult to implement: the process of obtaining useful information is associated with the use of a frequency-modulated oscillator with complex functional processing of the received signals. In addition, it is often difficult to locate the transceiver antenna directly above the road surface in order to probe it with electromagnetic waves normal to it.

Therefore, there is a need to find a technical solution that is free from these shortcomings and provides the ability to take measurements with simpler means.

The technical result of the present invention is to simplify the process of determining the state of the road surface.

The technical result in the proposed method for determining the state of the road surface is achieved by the fact that the monitored section of the road surface is probed with electromagnetic waves, electromagnetic waves reflected from this surface section are detected, the phase shift between incident and reflected waves or a change in the amplitude (power) of the received waves with respect to their the values for the incident waves, preliminarily determine, respectively, the main phase shift of these waves or the main change in amplitude (power ) of these waves in the absence of a covering layer on the road surface, while a passive reflector of incident electromagnetic waves is built into the surface layer of the road section being monitored in the direction opposite to the direction of the sounding waves, and sounding is carried out by electromagnetic waves of a fixed frequency at a certain angle different from the right angle, and the magnitude of the additional phase shift with respect to the main phase shift or additional changes in the amplitude (power) are accepted waves with respect to the main change in the amplitude (power) of these waves judged road surface condition. As a passive reflector, retroreflective metal plate, retroreflective metal corner reflector, Van Atta retroreflective grating can be used.

The proposed method is illustrated by drawings.

Figure 1 shows the layout of the device for implementing the method.

Figure 2 shows the structural diagram of a device for implementing the method.

Figure 3 shows the sensing circuit using a plate passive retroreflector.

Figure 4 shows the sensing scheme using a corner passive retroreflector.

Figure 5 shows the sounding scheme using a retro-reflective van Atta lattice.

The drawings show the surface of the road 1, a layer of water, ice or snow 2, retroreflector 3, rod 4, antenna 5, microwave generator 6, circulator 7, detector 8, recorder 9, elements of the antenna array Van Atta 10, 11, 12 and 13 , transmission lines 14 and 15.

The essence of the proposed method is as follows.

If it is not possible to make measurements with fixing the microwave device used to implement the method above the road surface, then a measurement scheme with a lateral location at the roadside of the device can be applied. This device can be implemented using passive retro-guiding elements that reflect microwaves in the direction opposite to the direction of the probe waves, i.e. retroreflectors. Such a retroreflector provides the reception of reflected waves by the same transceiver antenna, wherever it is located.

According to this method, the sensing of a controlled section of the road surface is carried out by electromagnetic waves of a fixed frequency using a transceiver antenna located at the side of the road, at a certain angle different from the right angle, that is, not normal to the road surface; It is also possible to use separate transmitting and receiving antennas. The electromagnetic waves reflected from this surface area are received and the phase shift between the incident and reflected waves or a change in the amplitude (power) of the received waves with respect to their values for the sounding waves is determined. In this case, the main phase shift of these waves or the main change in the amplitude (power) of these waves in the absence of a covering layer on the road surface is preliminarily determined. A passive reflector of the incident electromagnetic waves in the direction opposite to the direction of the sounding waves, that is, a retro-reflector, is built into the surface layer of the controlled section of the road. There is no need for communication lines between the retroreflector immersed in the surface layer and the electronic unit located off the road at its side. The built-in passive reflector, like the surface of the road (for example, asphalt), is subject to the possible presence of a layer of water, ice or snow on the roadway and the influence of its parameters (thickness, electrophysical parameters). The magnitude of the additional phase shift with respect to the main phase shift or an additional change in the amplitude (power) of the received waves with respect to the main change in the amplitude (power) of these waves is judged on the state of the road surface.

In the absence of any covering layer of water, snow or ice on the road surface, the main phase shift or the main change in the amplitude (power) of these waves is determined by the change, respectively, of the phase or amplitude in the air space between the measuring device and the road surface. If there is any layer on the road surface, namely, if there is a layer of water, ice or snow on it, an additional phase shift Δφ with respect to the indicated main phase shift and an additional change in the amplitude ΔA (power ΔP) of the received waves with respect to the main change in the amplitude (power) of these waves. The output signal of this measuring device depends, depending on what serves as an informative parameter, on the magnitude of the total phase shift or changes in the amplitude (power) of the received waves. This phase shift or change in the amplitude (power) varies depending on the thickness of the layer covering the road surface. They also depend on the electrophysical parameters, in particular the dielectric constant of the covering layer (water, ice or snow).

Figure 1 shows the layout of the device for implementing this method. The device can be placed at the edge (on the sidelines) of the measuring section of the road surface 1 with the possible presence of an ice or snow layer 2 on it, providing sounding of this section at an angle different from the right angle, that is, not normal to the surface of road 1. To the surface the layer of the monitored section of the road 1 embeds a passive reflector of the incident electromagnetic waves in the direction opposite to the direction of the sounding waves, that is, retroreflector 3. Using the rod 4, a transmitting and receiving antenna is fixed 5. Radiation 5 of the antenna is directed at an angle different from a right angle.

Here, the electromagnetic waves emitted by the transceiver antenna 5 are reflected from the monitored portion of the road surface 1 with a possible layer of water, ice or snow 2. These reflected waves are received by the transceiver antenna 5. Determination of the parameters of the received waves (phase shift between incident and reflected waves ; changes in the amplitude (power) of the received waves with respect to its value for incident waves) allows, when comparing these data with a priori found many similar values in the absence of covering a layer, a surface layer of the road identify and measure its parameters.

The structural diagram of a device for implementing the method is shown in figure 2. Here, a microwave frequency generator 6 of electromagnetic oscillations of a fixed frequency is connected through a circulator 7 to an antenna 5 probing a controlled portion of the road surface 1, which contains a passive retroreflector 3 with, possibly, a layer 3 of water, snow or ice covering it. Electromagnetic waves reflected from this retroreflector 3 enter through the circulator 7 to the detector 8 (when measuring the phase shift it is a phase detector); then the received signal is fed to the recorder 9. In this block, the received signal is compared with a predefined set of values of a similar signal (the main phase shift of these waves or the main change in the amplitude (power) of these waves) in the absence of a covering layer on the road surface and, as a result of this comparisons, identification of the surface layer of the road and measurement of its parameters.

To determine the state of the road surface due to the presence of a precipitation layer on its surface or its absence, it is necessary to know the electrophysical parameters of the possible substances on its surface - water, snow and ice in the microwave frequency range of electromagnetic waves. Since the electrophysical parameters of water, snow, and ice differ significantly from unity (which corresponds to the absence of such a layer on the road) and from each other (Nyfors EG, Vainikainen P. Industrial microwave sensors. Artech House, Inc. 1989. 351 p.), The values additional phase shift Δφ with respect to the main phase shift (in the absence of cover layer 2) and the range of its change, as well as the value of the additional change in the amplitude ΔA (power ΔP) of the received waves with respect to the main change in the amplitude (power) of these waves (in the absence of a cover layer 2) differ significantly in the presence of a layer on the surface of the road or in its absence. This allows you to determine what type of precipitation layer (water, snow or ice) is present on the road (or absent), and also to find its thickness by the magnitude of the change Δφ or ΔА.

Figure 3 shows the sensing circuit using a plate passive retroreflector. As a passive retro-reflecting reflector 5, a flat metal plate placed at a certain angle can be used for such sensing. Such a retroreflector 3 provides reception of reflected waves by the same antenna 5, wherever it is located. The slope of the plate retroreflector 3 should correspond to the position of the antenna 5. Here, the path of propagation of electromagnetic waves consists of a part of the path in the air and part of the path in the surface layer of the road; this should be taken into account when calculating the phase shift or (and) changes in the amplitude (power) of the received wave compared with the corresponding characteristics of the probe wave. On the surface of such a plate retroreflector 3, a thin dielectric plate with small dielectric constant and dielectric loss tangent, for example, fluoroplastic (not shown), can be placed.

As a passive retro-guiding microwave element, which can help in providing the required information about the state of the road surface 1, a 90 ° angled metal reflector can also be used. Figure 4 shows the sounding scheme from an angular passive retroreflector 3. In a rectangular metal angular reflector, retro-directivity follows from the phase conjugation of the incident waves on each element before reflection (Margerum DL Self-phased arrays. In Microwave scanning antennas, Vol.III, Ch.5 , Hansen RC, Ed. Los Altos CA: Peninsula. 1985. P. 366-382). The device can be located at the side of the road and can irradiate a controlled area of the surface of the road 1 at an angle different from 90 ° to its surface. Such a retroreflector 3 provides reception of reflected waves by the same antenna 5, wherever it is located. The slope of the rectangular corner retroreflector 3 and the dimensions of its side elements must correspond to the position of the antenna 5. And here the path of propagation of electromagnetic waves consists of part of the path in the air and part of the path in the surface layer of the road; this should be taken into account when calculating the phase shift or (and) changes in the amplitude (power) of the received wave compared with the corresponding characteristics of the probe wave. Thin dielectric plates with small values of dielectric constant and dielectric loss tangent, for example, fluoroplastic (not shown), can be placed on the surfaces of the side elements of such an angular retroreflector 3.

Figure 5 shows the sounding scheme using a retro-reflective van Atta lattice. Known retro-reflective Van Atta lattice, which contains interconnected transmission lines for phase coupling (US 2908002, 10.06.1959). In particular, it is possible to implement such a planar retroreflective antenna (Hewitt BS The evolution of radar technology into commercial systems // 1994 IEEE MTT-S Int. Microwave Symposium Digest. San Diego, Calif. 1994. Vol.3. P.1271-1274) . Here, the connection of the elements eliminates any phase difference between the antenna elements if the signal is received at angles other than the bearing to the antenna. As a result, incident waves are re-emitted in the direction from which they came. The total path length from the source to the grating element and then back is a constant for all grating elements, each scattered signal returns in phase to the source. An example of such an array with four antenna elements is shown in FIG. Here, the elements 10, 11, 12 and 13 of the linear antenna array are connected by transmission lines 14 and 15 symmetrically in pairs with respect to the geometric center of this array. This passive retroreflector is placed under the surface of road 1 with a possible covering layer 2. On the surface of such a grating, a thin dielectric plate with small values of dielectric constant and dielectric loss tangent, for example fluoroplastic (not shown), can be placed. Transceiver antenna 3 is located at the side of the road. Various implementations of the Van Atta lattice as retro-reflectors are possible, including planar structures.

Thus, this method allows quite simply and with high accuracy to determine the state of the road surface. It makes it possible to record the presence or absence of a layer of water, snow or ice on the road surface and to make their identification.

Claims (4)

1. The method of determining the state of the road surface, in which the monitored section of the road surface is probed by electromagnetic waves, electromagnetic waves reflected from this surface section are received, the phase shift between the incident and reflected waves or the change in the amplitude (power) of the received waves relative to their values for incident waves, pre-determine, respectively, the main phase shift of these waves or the main change in the amplitude (power) of these waves in the absence of a covering layer I am on the road surface, characterized in that a passive reflector of electromagnetic waves incident on it is embedded in the surface layer of the road section being monitored in the direction opposite to the direction of the sounding waves, and sounding is carried out by electromagnetic waves of a fixed frequency at a certain angle different from the right angle and in magnitude additional phase shift with respect to the main phase shift or additional changes in the amplitude (power) of the received waves with respect to the main and Menenius amplitude (power) of these waves judged road surface condition. 2. The method of determining the state of the road surface according to claim 1, characterized in that a retroreflective metal plate is used as a passive reflector. 3. The method of determining the state of the road surface according to claim 1, characterized in that a retroreflective metal corner reflector is used as a passive reflector. 4. The method for determining the state of the road surface according to claim 1, characterized in that the Van Atta retroreflective grating is used as a passive reflector.

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