DEVICE FOR DETECTING ROAD SURFACE WATER

Abstract

The present invention is a device for detecting water on the road that allows to automatically adapt the speed limits on roads according to the traffic conditions, and to transmit the information to a receiver.

The device according to the invention is based on the use of a ray of light transformed by refraction and absorption phenomena for detecting water on the road, by using the passage of vehicles as an indicator of the state of the road by that the wheels will cause in the back of their passage splashes or columns of water when the road is wet, these splashes causing, especially by refraction or absorption effect, a change in the quality of a ray of light when it passes through them before it reaches a receiver.

The receiver can display the information on a vehicle dashboard or on variable display signaling panels, or even transmit it to one or more automatic radar traps.

Claims

1. A device for detecting water on the road, wherein said device consists of an emitter (5) of a focused light beam (7), a receiver (R), a device which allows processing of the signal received by the receiver (R) when the latter receives the beam (7), by using the passage of the vehicles (1) as an indicator of the state of the road (3) by that the wheels (2) will cause in the back of their passage splashes or water columns (4) when the road (3) is wet, these splashes (4) causing, especially by refraction or absorption effect, a change in the quality of the light beam (7) when the latter passes through them before it reaches the receiver (R).

2. The device according to claim 1, wherein the light beam (7) is emitted with a frequency modulation and amplitude known by a single receiver (pattern).

3. The device according to claim 1, wherein the emitter (5) is positioned on one side of the road (3), the beam (7) passing over it and targeting the receiver (R) on the other side of the road (3), the receiver (R) being directed towards the emitter (5).

4. The device according to claim 1, wherein the emitter (5) and the receiver (R) are positioned on the same side of the road (3), and a reflection system consisting of a simple mirror or a retro-reflector is placed on the other side of the road (3) and returns the ray from the emitter (5) to the receiver (R).

5. The device according to claim 1, wherein said device is installed on a vehicle (1), fixed thereunder.

6. The device according to claim 5, wherein the emitter (5) and the receiver (R) are positioned behind a wheel or wheels (2) on both sides thereof.

7. The device according to claim 5, wherein the emitter (5) is positioned so as to direct a light beam behind the wheel (2) on the pavement, and the receiver (R) of a camera (19) is positioned so as to film the image (18) produced by the light beam on the pavement.

8. The device according to claim 7, wherein said device comprises a second emitter which directs a light beam on the pavement in an area sheltered from splashes to form there an image filmed by a second receiving camera.

9. The device according to claim 7, wherein said device comprises an optical device for separating a primary light beam produced by the single emitter in order to obtain the light beams (24, 25) aimed for forming the images (18, 22).

10. The device according to claim 7, wherein said device comprises means for cleaning the lenses of the camera or cameras (19, 23) or the receiver (R) and the emitter or emitters (5, 20).

11. The device according to claim 7, wherein the device for processing the signal received by the receiver is a microprocessor equipped with image processing algorithms.

12. The device according to claim 3, wherein the receiver (R) consists of a sensitive surface (8) perpendicular to the axis of a tube (6) located in the bottom of the tube (6) whose opacity, diameter, length, as well as inner coating make it possible to limit interfering rays which are not directed parallel to the axis of this tube (6).

13. The device according to claim 12, wherein the sensitive surface (8) consists of a photovoltaic cell which will convert the amount of photons received by the sensitive surface (8) into an electrical signal.

14. The device according to claim 12, wherein the sensitive surface (8) consists of a plurality of photovoltaic sensors constituting pixels and in which counting of the sensors stimulated by the beam (7) makes it possible to measure the surface of the spot of the beam (7) on the face of the sensitive surface (8).

15. The device according to claim 1, wherein said device is connected by wire or radio to variable display signaling panels, to one or more radar traps or to the computer of the vehicle (2) on which it is fixed.

16. The device according to claim 1, wherein the activation of the device is triggered by an atmospheric or surface hygrometer placed on the road (3).

17. The group of detectors for deteriorated traffic conditions comprising the device of the invention according to claim 1.

18. The group of detectors for deteriorated traffic conditions according to claim 17, wherein a wired or radio link with a regional or national monitoring center to inform in real time about the traffic conditions and the maximum authorized speed.

19. The device according to claim 2, wherein the emitter is positioned on one side of the road, the beam passing over it and targeting the receiver on the other side of the road, the receiver being directed towards the emitter.

20. The device according to claim 2, wherein the emitter and the receiver are positioned on the same side of the road, and a reflection system comprising a simple mirror or a retro-reflector is placed on the other side of the road and returns the ray from the emitter to the receiver.

Description

[0030] The accompanying drawings illustrate the invention:

[0031] FIG. 1 shows a front view of a fixed device in position

[0032] FIG. 2 illustrates a profile view showing the column of water behind the wheels

[0033] FIG. 3 shows the characteristic curve of a dry road

[0034] FIG. 4 shows the characteristic curve of a wet road for intensity measurement.

[0035] FIG. 5 shows the characteristic curve of a wet road for a spot surface measurement.

[0036] FIG. 6: illustrates the profile view of a vehicle with the light beam emitter arranged on one side of the wheel and the receiver on the other side

[0037] FIG. 7: illustrates the vehicle seen from below with the light beam emitter arranged on one side of the wheel and the receiver on the other side

[0038] FIG. 8: illustrates the profile view of a vehicle with the device fixed under the vehicle with an emitter and two cameras

[0039] FIG. 9 shows the vehicle seen from below with the device fixed under the vehicle with an emitter and two cameras

[0040] FIG. 10: illustrates the profile view of a vehicle with the device fixed under the vehicle with two emitters and two cameras

[0041] FIG. 11: shows the vehicle seen from below with the device fixed under the vehicle with two emitters and two cameras.

[0042] With reference to these drawings

[0043] FIG. 1 shows a view of a device in position with vehicle (1) from the front, perpendicular to the light beam (7) with its wheels (2) on the road (3), the light beam (7) passing at a height of several centimeters above the road (3) and parallel to its surface. The height is set so that the light beam (7) passes below the bottom of the vehicle bodywork and under the mudguards and is not obstructed by surface defects of the road surface. The light beam (7) emitted by the emitter (5), passes over the road (3), then passes through the tube (6) in its length and reaches the sensitive surface (8) of the receiver (R).

[0044] FIG. 2 shows a profile view of the light beam (7) passing through the water column (4) produced by the movement of the wheel (2).

[0045] The receiver (R) consists of an opaque tube (6) at the bottom of which a sensitive surface (8) is placed perpendicular to the axis of the tube (6). The tube (6) may for example be made of opaque plastic of PVC type, the inner wall of which is covered with a substance that prevents reflection of parasitic rays not parallel to the axis of the tube (6), for example, a matte black paint. The diameter and length of this tube (6) are defined by those skilled in the art so as to limit parasitic rays. The sensitive surface (8) consists of a photovoltaic system, for example made of CCD sensors. If the signal intensity measurement is recorded, the sensor functions as a photovoltaic cell that will convert the amount of photons received in the normal target area of the light beam (7) on the sensitive surface (8) into an electrical signal whose intensity is proportional to the amount of photons received. When measuring the size of the surface of the spot produced by the light beam (7) on the sensitive surface (8), the receiver consists of several sensors, for example of CCD type, forming pixels. The amount of pixels activated by the light beam (7) is proportional to the spot surface and therefore makes it possible to find out the surface of the spot. These electrical signals are further processed by a microprocessor and a “rainy weather” signal is transmitted by wire or by means of electromagnetic waves to a fixed radar trap, which will then adjusts its maximum authorized limit.

[0046] To avoid false positives, especially in the case of an occasional punctual water puddle on the edges close to this system, to avoid too fast aging, and to reduce electrical power consumption, a hygrometer can be connected to this device. The presence of humidity only, in the air (atmospheric hygrometer) or on the road (surface hygrometer), triggers the device to start.

[0047] In the case of a dry road, the microprocessor will build a square type signal (FIG. 3) when a wheel passes in front of the light beam (7). On the ordinate axis, the amount of electromagnetic energy received or the amount of photoreceptors activated by the light beam (7), and on the abscissa the time in milliseconds, for example. For a vehicle (1) running at 100 km/h, wheels (2) having a diameter of 60 cm and a beam height in relation to the road of 5 cm, for example, the light beam will suddenly be interrupted during about 12 ms. Before and after this interruption with y=0 for 12 ms, y is constant and has a nominal value of 1. The curve will therefore display a straight line y=1 and then a vertical straight line segment (9) x=a, indicator of the beginning of the passage of the wheel (2), then a straight line segment (10) y=0 for 12 ms (passage of the wheel (2) completely blocking the light beam (7)), and then a vertical straight line segment (11) x=a+12, indicator of the end of the passage of the wheel (2), and finally a straight line y=1.

[0048] In the case of a wet road, FIG. 4 shows the curve produced when measuring the amount of photons received by the sensitive surface (8) with this intensity on the ordinate and the time on the abscissa. In the same example of the speed of the vehicle (1), the curve will be a straight line y=1, then a straight line segment (12) vertical x=a marking the beginning of the passage of the wheel (2), then a straight line segment (13) y=0 for 12 ms (passage of the wheel (2) completely blocking the light beam (7)), then a segment (14) more or less inclined or with irregular oscillations between y=0 and y=1 for a variable period (marking the existence of microdroplets or droplets of water that prevent the normal passage of the light beam (7) through the water column (4), and finally a straight line y=1 when the water column ends.

[0049] For a wet road in the same example, FIG. 5 shows the case where the receiver (R) measures the surface of the spot produced by the light beam (7) on the sensitive surface (8), this value being used on the ordinate. The curve now shows the same beginning through a straight line y=1, then a straight line segment (15) vertical x=a marking the beginning of the passage of the wheel (2), then a straight line segment (16) y=0 for 12 ms (the passage of the wheel (2) completely blocking the light beam (7)), then a segment (17) which increases with a rather steep slope to exceed y=1 up to a maximum value max (the surface of the spot is larger as a result of the refraction phenomena of the light beam (7) that passes through the water column (4)), and then returns over a variable period with a regular shape or showing irregular oscillations between y=max and y=1, and finally a straight line y=1 when the water column ends.

[0050] Observing these non-vertical segments (14) or (17) non-vertical, different from (11) x=a+12 is an incontestable proof of the “rainy weather”. The microprocessor then sends the appropriate signal to the fixed radar trap to adjust its authorized speed limit to that which is defined by the Highway Code in case of “rainy weather”.

[0051] In a device fixed on one side of the wheel and the receiver on the other side, directly beneath the vehicle, a light beam emitter (5) is fixed under the vehicle (1) behind the wheel (2), for example in the wheel arch at the wing plane on one side of the wheel (2). It is possible to use one or more wheels (2). A receiver (R) consisting of photoreceptors, such as photovoltaic cells receiving the light beam (7), and a microprocessor that converts the data produced by the sensitive surface, is mounted on the other side of the wheel. The emitter (5) sends a light beam (7) having an electromagnetic pattern emitted by a frequency modulation and amplitude known by a single receiver (pattern), in order to be able to differentiate the interfering signals. This pattern helps to avoid processing the parasitic lights on the receiver (R), and thus to limit interference phenomena. On a dry road or when the vehicle (1) is stationary, the receiver (R) records a signal with a nominal intensity on the receiving surface, or a nominal surface when the receiver is expected to record the surface excited by the light beam (7). In the case of water splashing (4) by the wheel (2) when the vehicle (1) moves on a wet road, the light beam undergoes transformations by refraction and absorption phenomena. A portion of the photons will be deflected or absorbed and will no longer reach the target, so decreasing in this situation the amount of light energy recorded by the receiver (R) on its receiving surface. A decrease in the intensity of the signal received by the receiver (R) is then noted. Deflections caused by the refraction phenomena will cause an increase in the diameter of the light beam (7), and hence an increase in the amount of excited photoreceptors at the receiver (R) level. In this case, an increase in the signal from this type of receptor is noted. These changes demonstrate the existence of water splashing and, thanks to it, the existence of a wet road on which it is necessary to reduce the speed of the vehicle (1) which risks losing its adhesion.

[0052] In a device mounted under the vehicle, the emitter (5) of the light beam (7) is fixed under the vehicle (1). FIGS. 10 and 11 show a system in which a single emitter (5) directs its light beam (7) on the pavement forming an image (18) behind the wheel (2). A camera (19) records the image (18) and sends it to a microprocessor equipped with image processing algorithms, and compares it with a reference image. This reference image is obtained by filming the image (18) obtained when the vehicle (1) is stopped. Without changing the operation at all, the skilled artisan may prefer the architecture with two emitters (5, 20) each producing an identical light beam. FIGS. 8 and 9 show a system with an emitter (5) and two cameras (19, 23) simultaneously shooting the two images (18, 22) produced by the light rays (24, 25) on the pavement. In the example with a single light emitter (5), the primary light beam (7) produces two identical secondary light beams (24, 25) by passing through an optical device (26). It is composed, for example, of a mirror that directs the beam (7) towards the roadway and a prism separating the primary beam (7) into two secondary beams (24, 25). The secondary measuring beam (24) is directed towards the pavement immediately behind the wheel (2). The reference secondary beam (25) is directed towards the pavement laterally to the wheel (2) in order to be more sheltered from the sprinkled columns of water (4) raised by the wheel (2) when the road is wet. A camera (23) records the image (22) of the secondary reference beam (25) on the pavement, while the other camera (19) records the image (18) of the secondary measurement beam (24). The images (18, 22) are then sent to a microprocessor equipped with image processing algorithms that compares them. A difference between the reference image (22) and the measurement image (18) indicates the existence of splashing water columns behind the wheel (2) and highlights the wet state of the road.

[0053] Cleaning devices for the lens of the camera or cameras (19, 23) or the receiver (R) and the emitter or emitters (5, 20) are provided in order to limit the dirt that disturbs the transmission of light rays. They consist, for example, of a pressurized sprinkler system or windscreen wiper blades, for example. The use of self-cleaning glasses by depositing a titanium dioxide based photocatalytic layer on them, for example, may also be considered.

[0054] The device according to the invention is connected by wire or radio to the computer of the vehicle (2), which can in turn send a warning message to the driver or can directly adjust the speed of the vehicle (2) in view of the deteriorated traffic conditions. The device sends information to the computer.

[0055] It translates this information by comparing it with the thresholds set by the government to declare the existence of a “rainy weather”, the presence of rain, wet or glazed pavement, crowding of cars, a peak of pollution, etc.

[0056] The computer translates this information into the maximum authorized speed in these damaged conditions and sends this value to a panel or multiple panels for digital display. The panel or panels display in turn for the drivers the maximum speed in these deteriorated conditions.

[0057] In the absence of information on deteriorated conditions, the relevant panels and radar traps set at the normal speed limit.

[0058] The device according to the invention can be used in a group of detectors for deteriorated traffic conditions connected via a computer to one or more variable display speed limitation panels (LED or LCD type, for example) and whose display is remotely changeable, this or these latter indicating in real time the authorized speed limit adapted to traffic conditions.

[0059] The group of detectors for deteriorated traffic conditions comprises one or more detectors arranged within one or more boxes.

[0060] The group of detectors for deteriorated traffic conditions consists of all or some of these detection elements centralized within a single detection box or in several systems, and connected to a computer that gathers the information collected by each detection system and sends the signal adapted to the damage observed to the display panels and to the radar traps or to the display panels that in turn transmit the signal to the radar traps.

[0061] Without limitation in the composition of the group of detectors for deteriorated traffic conditions, a complete system is composed, for example, of a “rainy weather” detector, a rain detector, a detector of wet or icy road, a detector of the number of vehicles per hour, a detector of decline of visibility, an air pollution detector.

[0062] In order to achieve an educational effect and to get the involvement of motorists, it is desirable to show at the same time the reason or reasons for the lowering of the maximum authorized speed, for example, wet road, ice, low visibility, rainy weather, pollution, and crowding of vehicles and so on.

[0063] The display panel or panels, after being updated, transmit this value to one or more automatic control radar traps.

[0064] The computer can also transmit information to display panels and radar traps simultaneously.

[0065] The computer or display panel or radar trap sends the information to a regional or national center to inform the authorities about the real-time traffic status.

[0066] The links between the detectors, the computer, the panel, the radar trap and the center are made by a wired system or by electromagnetic waves. The communication system based on the LoRaWAN (Long Range Wide-Area Network) protocol may be applicable very well herein, for example.

[0067] The device according to the invention is particularly intended for road safety.