JPH06307838A - Road surface condition sensing device - Google Patents

Abstract

PURPOSE:To provide a road surface condition sensing device which can sense generation of the water film condition of road surface on which car is going to run. CONSTITUTION:A laser beam L1 and sonic wave L2 are cast onto a road surface R, and the laser beams L1 and L3 before and after being reflected by the road surface are converted into electric signals, and then the amplitudes of these two signals are put identical, and also the synthesized wave therefrom is produced, and a signal to display the sensed water film on the road surface R is generated in accordance with the DC detection level of this synthesized wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface condition detecting device, and more particularly to a device for detecting a condition of a road surface on which a vehicle is about to travel.

[0002]

2. Description of the Related Art As a road surface state detecting device, Japanese Patent Laid-Open No. 60-
In Japanese Patent No. 142209, there is one disclosed in Japanese Patent Laid-Open No. 142209, in which a beam having a directivity is emitted to the front of the vehicle and a reflected wave thereof is received to measure the length of the distance. This is a device for determining the unevenness state, and is intended to perform general optimal control of the undercarriage according to the determined road surface state.

[0003]

In the prior art as described above, even if the distance between the vehicle body and the front road surface can be measured, it cannot be determined whether or not the road surface is covered with a water film, There was a problem that it was insufficient to control the general rotation.

Therefore, an object of the present invention is to realize an apparatus capable of detecting a water film state on a road surface.

[0005]

In order to achieve the above object, a road surface state detecting device according to the present invention is provided in a lower portion of a vehicle body, emits a laser beam to a road surface, and monitors the laser beam to generate an electrical signal. A light emitting section for outputting as a signal, a sound source provided under the vehicle body for emitting a sound wave to the laser beam on the road surface, and a light receiving section for receiving the laser beam reflected on the road surface and outputting an electric signal Section, and an electric signal from the light receiving section and an electric signal from the light emitting section are input to make the amplitudes of both electric signals coincide and generate an amplitude modulated wave that is synthesized, depending on the DC detection level of the amplitude modulated wave. And a detection circuit for generating a signal for detecting and displaying the water film on the road surface.

[0006]

In the present invention, the laser light is emitted from the light emitting portion provided in the lower portion of the vehicle body to the road surface, and the laser light is reflected on the road surface and given to the light receiving portion.

On the other hand, in addition to the laser light, sound waves from a sound source are reflected on the road surface and input to the above-mentioned light receiving portion.

In this case, when a water film is present on the road surface, the laser light causes a "stimulated Brillouin scattering" phenomenon due to the sound waves from the sound source, and the laser light is frequency-shifted.

The "stimulated Brillouin scattering" phenomenon will be briefly described. When a sound wave is projected on water, the water molecules become compression wave water having different densities due to the sound wave. If there is a difference in density, the natural frequency of that part changes, and the phenomenon in which the light wave becomes a scattered wave with its frequency (frequency) changed due to the combined action of this natural frequency and the light wave is called stimulated Brillouin scattering. There is.

Let E1 be the laser light before the stimulated Brillouin scattering and E2 be the laser light after the stimulated Brillouin scattering.
Can be expressed by the following equations (1) and (2), respectively.

[0011]

[Equation 1]

However, the laser light parameters k1, ω1,
φ1 indicates the wave number, angular frequency, and initial phase of the laser light itself from the light emitting part when there is no water film on the road surface (when stimulated Brillouin scattering does not occur), and the parameters k2, ω2, and φ2 are the road surface. The wave number, angular frequency, and initial phase when the above-mentioned stimulated Brillouin scattering occurs due to the presence of a water film above are shown.

Then, such laser beams E1 and E
When two are superposed, a composite wave E as shown in the following equation (3)
Is obtained.

[0014]

[Equation 2]

In the above equation (3), A1 = A
When 2 = A, the composite wave E becomes as shown in the following expression (4).

[0016]

[Equation 3]

The above equation (4) has a waveform as shown by a solid line in FIG. 4, and its envelope has a waveform as shown by a dotted line. This shows an amplitude modulated wave.

On the other hand, when there is no water film on the road surface, since there is no frequency shift due to stimulated Brillouin scattering on the road surface, the parameters of the input laser light to the light receiving section are only k1, ω1, and φ1. The wave of the laser light source comes back as it is.

Therefore, the parameters shown in equation (4) are as follows.

[0020]

[Equation 4]

Therefore, the above equation (4) becomes the following equation (5).

[0022]

[Equation 5]

As described above, when a water film exists on the road surface, the waveform becomes as shown in FIG. 4 due to stimulated Brillouin scattering, but when there is no water film on the road surface, it becomes as shown in equation (5), Signal of laser light as it is (see formula (1))
Becomes

Therefore, the waveform shown in the equation (5) becomes a direct current signal of 2A as shown in FIG. 4 by the direct current detection, and this direct current level and the waveform having the envelope shown in the equation (4) are detected by the direct current. By comparing with the direct current level at the time, it can be determined whether or not the water film exists on the road surface.

Therefore, in the detection circuit of the present invention, the electric signal from the light receiving portion and the monitored electric signal from the light emitting portion are input and the amplitudes of both electric signals are expressed by the above equation (4).
Then, the electric waves are matched with each other, and a composite wave is generated by combining these electric signals.

This composite wave is a constant DC signal as shown in FIG. 4 when there is no water film on the road surface, and a waveform having an envelope (amplitude modulation wave) when there is a water film on the road surface. Therefore, it becomes smaller than the DC detection level of the former, and it becomes possible to generate a signal for detecting and displaying the water film on the road surface according to the DC detection levels of both.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows a state in which a road surface state detecting device according to the present invention is attached to a vehicle. In the figure, 1 is a light emitting portion, 2 is a sound wave source, and 3 is a light receiving portion. These are provided below the bumper 4 of the vehicle 10 so that laser light and sound waves are output to the road surface R and received by the light receiving unit 3.

FIG. 2 shows the light emitting section 1 and the acoustic wave source 2 shown in FIG.
The laser beam L1 output from the light emitting unit 1 is reflected by the road surface R and input to the light receiving unit 3 as the reflected light L3. Two
Since the sound wave L2 from is also incident on the road surface R,
When the water W is present on the road surface R, the laser beam L1 is caused to cause stimulated Brillouin scattering by the sound wave L2, and the reflected laser beam L3 is input to the light emitting unit 3 in a frequency-shifted form.

As an example of stimulated Brillouin scattering, the frequency shift amount in water is 5690 MHz.
Here, as an example, the frequency of the 830 nm laser beam is 36
It is 1.44578 THz. On the other hand, 5,690
With a frequency shift of GHz, 361.44009THz
= 361.4445THz-0.00569THz causes a scattered light of 361.44009THz.

FIG. 3 shows an embodiment of a road surface condition detecting device according to the present invention. In this embodiment, first, the light emitting section 1 is a laser light source 1a, a collimator lens 1b, and the laser light source 1a and the collimator lens. 1b and a beam splitter 1c which is installed so that its optical axis coincides with that of the laser beam L1 and emits a laser beam L1 to a road surface R.
And a light receiver 1d for monitoring a part of the laser light and converting it into an electric signal.

The detection circuit 5 receives the electric signal A1 'from the light receiver 1d in the light emitting section 1 and the electric signal A2 from the light receiving section 3 and outputs a differential signal between them. An AGC amplifier 52 that uses the electric signal A1 ′ from the light receiver 1d as a controlled voltage, and the AGC amplifier 5
It includes a differential amplifier 53 which receives the output signal A3 of 2 and the output signal A2 of the light receiving unit 3 and outputs the difference between them. The output signal A4 of the differential amplifier 53 is the differential amplifier 5
The output signal of 1 is added to form the control voltage of the AGC amplifier 52.

Further, the detection circuit 5 has the output signal A of the light receiving section 3.
2 and the output signal A3 of the AGC amplifier 52 via the resistors r1 and r2, respectively, and the combined wave output from the adder 54 (when a water film exists on the road surface R, 4 for DC detection of the amplitude-modulated wave of No. 4), a smoothing circuit by a resistor r4 and a capacitor c1 for smoothing the output voltage of the diode D1, and the output voltage and voltage of this smoothing circuit -2
A), a Zener diode ZD1 for comparing with "A" and a resistor r5, and a transistor for receiving the output of the Zener diode ZD1 of the comparator circuit 55 at the base and for causing the light emitting diode LED1 connected to the emitter to emit light. It includes Tr and.

Next, the operation of the above embodiment will be described.

First, the sound wave L is directed from the sound wave source 2 toward the road surface R.
At the same time, the light beam L1 which is emitted from the laser light source 1a and becomes parallel light from the laser light source 1a enters the road surface R through the collimator lens 1b. At that time, a part of the light wave is received by the light receiver 1 by the beam splitter 1c arranged behind the collimator lens 1b.
The light is received at d and output to the detection circuit 5 as an electric signal A1 '.

Further, the stimulated Brillouin scattered light of the laser light L1 by the water film W on the road surface R and the sound wave L2 is detected by the light receiving portion 3 and output to the detection circuit 5 as an electric signal A2.

A differential amplifier 51 detects the amplitude difference between the electric signals A2 and A1 'and amplifies the electric signal A1'.
The control voltage of the GC amplifier 52 is used. Further, the amplitude difference between the output signal A3 and the signal A2 of the AGC amplifier 52 is detected by the differential amplifier 53 and is feedback-added as the signal A4 to the control voltage of the AGC amplifier 52.

As a result, the output signal A of the AGC amplifier 52 is
3 becomes equal to the amplitude of the signal A2 and both signals A2 and A3
Are added by the adder 54 as the light waves E2 and E1 of the equations (1) and (2), respectively, and the combined wave E shown in the equation (4) is obtained.
To get

As shown in FIG. 4, when the water film W does not exist on the road surface R, this composite wave becomes a DC signal having a constant amplitude 2A as shown in the above equation (5), and when the water film W exists. The frequency beat wave (amplitude modulated wave) has an envelope as shown in the above equation (4).

The composite wave E is DC-detected by the diode D1 and is output as a DC amplitude value via the smoothing circuit composed of the resistor r4 and the capacitor c1. In this case, when the water film W does not exist on the road surface R, the DC signal has a constant amplitude of 2A as described above, and when the water film W exists, the average value of the envelope as shown in the above equation (4) is obtained. .

Then, the DC voltage output from the capacitor c1 is compared with the voltage "-2A" generated by the Zener diode ZD1 of the comparison circuit 55.

The output voltage of the comparison circuit 55 at this time is 2 when the water film W does not exist on the road surface R because the constant amplitude 2A is output from the capacitor c1 as described above.
When A−2A = 0 and the water film W exists, the average value of the envelope as shown in FIG. 4 is smaller than the voltage 2A, and the negative voltage of the difference is output.

Therefore, when the water film W does not exist on the road surface R, the voltage is not applied to the base of the transistor Tr, so that the light emitting diode LED1 is not driven and does not light up. However, when the water film W exists, the base of the transistor Tr does not exist. Since a negative voltage is applied and the transistor Tr becomes conductive, the light emitting diode LED1 is driven and lights up.

[0043]

As described above, in the road surface condition detecting device according to the present invention, the laser light and the sound wave are emitted to the road surface and the laser light before being reflected on the road surface and the laser light after being reflected are converted into electric signals. After conversion, both electric signals are made to have the same amplitude, and a composite wave of these is generated, and a signal for detecting and displaying a water film on the road surface is generated according to the DC detection level of the composite wave. It becomes possible to inform the driver that there is a film of water on it, and this can be used as part of the control signal of the brake such as ABS.

[Brief description of drawings]

FIG. 1 is a front view showing a state in which a road surface state detecting device according to the present invention is attached to a lower portion of a vehicle.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a circuit diagram showing an embodiment of a road surface state detecting device according to the present invention.

FIG. 4 is a waveform diagram showing a composite wave (amplitude modulation wave / DC voltage wave) in the road surface state detecting device according to the present invention.

[Explanation of symbols]

 1 Light emitting part 1a Laser light source 1d Light receiver 2 Sound wave source 3 Light receiving part 5 Detection circuit 51,53 Differential amplifier 52 AGC amplifier 54 Adder D1 diode ZD1 Zener diode LED1 Light emitting diode R Road surface W Water film L1, L3 Laser light L2 Sound wave In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A light emitting unit provided under a vehicle body for emitting a laser beam to a road surface and monitoring the laser beam and outputting as an electric signal, and a light emitting unit provided under the vehicle body for the laser beam on the road surface. A sound source that emits sound waves, a light receiving unit that receives the laser light reflected on the road surface and outputs an electric signal, and an electric signal from the light receiving unit and an electric signal from the light emitting unit. And a detection circuit for generating a signal for detecting and displaying a water film on the road surface in accordance with the DC detection level of the combined wave while making the amplitudes of both electric signals coincident with each other. Road surface condition detection device.