JPH0954020A - Road condition detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the detecting precision of a road condition detecting device. SOLUTION: A microphone 1 detects contact sounds between a vehicle tire and a road surface. A speed detecting part 2 detects the speed of a vehicle. A signal processing part 3 samples contact sound signals from the microphone 1 and speed signals from the speed detecting part 2 at preset periods and gives the contact sound signals and the speed signals to a judging part every time. The judging part 4 squares a speed V (km/h) shown by the speed signals to find the first computed value v<2> and divides the level s of the contact signals by the first computed value v<2> to find the second computed value s/v<2> /. The judging part 4 judges a road to be dry if the second computed value s/v<2> is smaller than first threshold value m1 , to be wet if second computed value s/v<2> is not smaller than the first threshold value m1 and smaller than the second threshold value m2 , and to be bad if the second computed value s/v<2> is not smaller than the second threshold value m2 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface state detecting device for detecting a state of a road surface on which a tire of a vehicle is grounded.

[0002]

2. Description of the Related Art A road surface condition detecting device of this type prompts a driver to perform a driving operation suitable for an actual road surface condition, or adjusts a vehicle control condition to an actual road surface condition to stabilize traveling and braking. Helps increase sex.

An example of this road surface state detecting device is the device described in Japanese Patent Laid-Open No. 174543/1994. Here, the sound generated from the tire is collected by a microphone, and the state of the road surface on which the tire is in contact with the ground is determined based on the sound pressure level within a preset frequency band.

[0004]

However, in the above-mentioned conventional device, the influence of the vehicle speed is not taken into consideration at all, and therefore, the level of the sound generated from the tire changes with the change of the vehicle speed. If it changes, there is a possibility that the state of the road surface may be erroneously detected.

If the road surface state is erroneously detected, the vehicle is controlled based on erroneous information.
It is counterproductive in terms of safety. Therefore, in this type of device, it is extremely important to improve the detection accuracy.

An object of the present invention is to improve the detection accuracy of this type of road surface condition detecting device.

[0007]

In order to solve the above-mentioned problems, a road surface state detecting device of the present invention comprises a contact sound detecting means for detecting a contact sound between a tire of a vehicle and a road surface, and a speed for detecting the speed of the vehicle. The detection means and the determination means for determining the state of the road surface based on the contact sound detected by the contact sound detection means and the speed detected by the speed detection means.

That is, in this device, not only the contact sound between the tire and the road surface but also the vehicle speed is taken in, and the condition of the road surface is accurately determined based on the contact sound and the speed.

For example, the determination means squares the speed of the vehicle,
The level of the contact sound is standardized on the basis of the first calculated value obtained by this square, and the second level obtained by this standardization.
The state of the road surface is determined based on the calculated value. This standardized second operation value excludes the influence of speed,
It does not depend on speed, but only on road conditions. Therefore, the determination of the state of the road surface based on the second calculated value is accurate.

Further, it further comprises an extracting means for extracting a band component of a predetermined frequency band from the contact sound detected by the contact sound detecting means, and the judging means squares the speed of the vehicle, and by this square, The level of the band component is standardized based on the obtained first calculated value, and the state of the road surface is determined based on the third calculated value obtained by this standardization. In this way, when the band component of the specific frequency band is extracted from the contact sound and this band component is used as the material for the determination, it is possible to obtain a clear change in the third calculated value according to the state of the road surface. , It becomes easy to determine the condition of the road surface.

Further, for example, the determining means obtains the variation in the level of the contact sound with the passage of time, and determines the vehicle speed as 2
Then, the variation in the level of the contact sound is standardized based on the first calculated value obtained by the square, and the state of the road surface is determined based on the fourth calculated value obtained by this standardization. The standardized fourth calculated value excludes the influence of speed and changes only depending on the road surface state. Therefore, based on the fourth calculated value, the road surface state can be accurately determined. it can.

Further, it further comprises an extracting means for extracting a band component of a predetermined frequency band from the contact sound detected by the contact sound detecting means, and the judging means obtains a variation in the level of the band component with respect to the passage of time. , The speed of the vehicle is squared, the variation in the level of the band component is standardized based on the first calculated value obtained by the square, and the road surface state is calculated based on the fifth calculated value obtained by this standardization. To detect. In this way, when the band component of the specific frequency band is extracted from the contact sound and this band component is used as the material for the determination, the fifth calculated value can be clearly changed according to the state of the road surface. It becomes easier to determine the condition of the road surface.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of the road surface state detecting device of the present invention. This device includes a microphone 1 that detects a contact sound between a tire of a vehicle and a road surface, a speed detection unit 2 that detects a speed of the vehicle, a signal processing unit 3 that samples each output of the microphone 1 and the speed detection unit 2, and a road surface. A determination unit 4 that determines the state is provided.

As shown in FIG. 2, the microphone 1 is arranged near an axle 7 that supports the tire 6. This microphone 1
At the position of, the contact sound between the tire 6 and the road surface can be easily detected, and it is not easily affected by ambient noise, and water, mud, pebbles, etc. splashed by the tire 6 are hard to hit.

The speed detecting unit 2 may be a general one that detects the number of rotations of the tire and obtains the speed based on this number of rotations, and an existing one in the vehicle can be used.

The signal processing unit 3 samples the contact sound signal from the microphone 1 and the speed signal from the speed detecting unit 2 at a predetermined cycle, and determines the contact sound signal and the speed signal at each sampling. Give to part 4.

When the contact sound signal and the speed signal are input, the judging section 4 receives the speed v (km / km) indicated by the speed signal.
h) is squared to obtain the first calculation value v ^2, and the level s of the contact sound signal is divided by the first calculation value v ² to obtain the second calculation value s / v.
Ask for ² .

Here, on a dry road, the vehicle speed v =
Spectral distribution characteristics of contact sound signal sampled at 40 (km / h) and velocity v = 60 (km / h)
The spectral distribution characteristics of the contact sound signal sampled at the time are shown in FIGS. 3 (a) and 3 (b). Further, in the wet road, the spectrum distribution characteristic of the contact sound signal when the speed v = 40 (km / h) and the spectrum distribution characteristic of the contact sound signal when the speed v = 60 (km / h) are shown in FIG. Shown in a) and (b). Similarly, on a rough road, the speed v = 40
The spectrum distribution characteristics of the contact sound signal at (km / h) and the spectrum distribution characteristics of the contact sound signal at the speed v = 60 (km / h) are shown in FIGS.

When the second calculation value s / v ² was obtained for each of these spectral distribution characteristics according to the above calculation by the judging section 4, the result shown in the graph of FIG. 6 was obtained. However, the level s of the contact sound signal is an average value of the levels of all frequencies.

As is apparent from the graph of FIG. 6, the second calculated value s / v ² changes depending on the state of the road surface, but is hardly affected by the vehicle speed v. This second
The calculated value s / v ² is about 0.4 on a dry road, about 1.6 on a wet road, and about 2.0 on a bad road.

Therefore, 0.4 of the dry road and 1.6 of the wet road.
The value 1.8 second threshold m between the values 0.8 first and the threshold m _1, also of 1.6 and bad road in wet road 2.0 between
₂ by the first and second threshold values m ₁ and m ₂ ,
By evaluating the second calculated value s / v ² , the state of the road surface can be determined.

Therefore, the determination unit 4 determines the second calculated value s / v ² every time the second calculated value s / v ² is obtained in accordance with the above calculation.
v ² is compared with the first and second threshold values m ₁ and m _2, and if the second calculated value s / v ² is less than the first threshold value m ₁ ,
Judge as a dry road. Similarly, if the second calculated value s / v ² is greater than or equal to the first threshold value m ₁ and less than the second threshold value m ₂ , it is determined as a wet road, and the second calculated value s / v 2 is determined. ^{If 2} is greater than or equal to the second threshold m ₂ , it is determined to be a bad road.

FIG. 7 shows a second embodiment of the road surface condition detecting device of the present invention. In this device, a low-pass filter (hereinafter referred to as LPF) 11 for filtering a contact sound signal from the microphone 1 and a high-pass filter (hereinafter referred to as HPF) 12 are additionally provided in the device shown in FIG. LP
The F11 extracts a low frequency band component having a frequency of 1 kHz or less from the contact sound signal and transfers the low frequency band component to the signal processing unit 3. Further, the HPF 12 extracts a high frequency band component having a frequency of 3 kHz or higher from the contact signal and transfers the high frequency band component to the signal processing unit 3.

The signal processing unit 3 samples the low frequency band component from the LPF 11 and the high frequency band component from the HPF 12 together with the speed signal from the speed detecting unit 2 in a predetermined cycle, and at each sampling, the low frequency band component is sampled. The component, the high frequency band component, and the velocity signal are given to the determination unit 4.

When inputting these, the judging section 4 performs the same arithmetic processing as that of the first embodiment for each of the low frequency band component and the high frequency band component. That is, the speed v (km / h) indicated by the speed signal is squared to obtain the first calculated value v ²
And the level s _L of the low frequency band component is calculated as the first calculated value v
Divide by ² to obtain the third calculated value for low frequencies s _L / v ²
Ask for. In addition, the level s _H of the high frequency band component is set to the first
The third calculated value s for high frequencies is divided by the calculated value v ^2.
_{Calculate H} / v ² .

Here, for each spectral distribution characteristic shown in FIGS. 3 to 5, the third operation value s _L / v for low frequencies is obtained.
^{When 2} was obtained, the result shown in the graph of FIG. 8 was obtained. Further, when the third calculated value s _H / v ² for the high frequency was obtained for each of these spectral distribution characteristics, the result shown in the graph of FIG. 9 was obtained.

As is apparent from the graph of FIG. 8, the third calculated value s _L / v ² for low frequencies becomes extremely large on a rough road. Further, as is clear from the graph of FIG. 9, the third calculated value s _H / v ² for high frequencies becomes significantly large on the wet road. The clear change of the third calculated value according to the state of the road surface is that the low frequency band component with a frequency of 1 kHz or less and the high frequency band component with a frequency of 3 kHz or more are extracted from the contact sound signal, and these low frequency bands are extracted. This is because the third calculated value is derived from the component and the high frequency band component. That is, the specific frequency band component in the contact sound signal changes sensitively to the specific state of the road surface, and the third calculated value derived from this specific frequency band component also changes to the specific state of the road surface. Changes sensitively.

On the basis of this clearly changing third operation value, the condition of the road surface can be determined more accurately. Therefore, the determination unit 4 uses the third calculation value s _L for low frequencies.
/ V ² is the third threshold value m ₃ (= 0.
6) or more, it is determined to be a bad road, and if the third calculated value s _H / v ² for high frequencies is the fourth threshold value m ₄ (= 0.4) or more shown in the graph of FIG. 9, , Wet road.
In addition, the third calculated value s _L / v ² for the low frequency is the third
If it is less than the threshold value m ₃ and the third calculated value s _H / v ² for the high frequency is less than the fourth threshold value m ₄ , it is determined as a dry road.

Next, the third embodiment of the road surface condition detecting device of the present invention.
An embodiment will be described. The device of the third embodiment has the same configuration as that of the first embodiment shown in FIG. However, the processing contents of the signal processing unit 3 and the determination unit 4 are different.

The signal processing unit 3 repeatedly samples the contact signal from the microphone 1 500 times at a cycle of, for example, 500 Hz. The signal processing unit 3 gives the contact signal to the determination unit 4 and outputs the contact signal from the speed detection unit 2 for each sampling. The velocity signal is sampled at least once, and the velocity signal is given to the determination unit 4.

When the speed signal is input, the judging section 4 squares the speed v (km / h) indicated by the speed signal,
The first calculated value v ² is obtained. Further, when the contact signal is repeatedly given 500 times, the determination unit 4 obtains the variation p of the level of these contact signals. This variation p may be derived according to well-known statistics and probability theory, or the difference between the maximum value and the minimum value may be obtained. The determination unit 4 divides this variation p by the first calculation value v ² to obtain the fourth calculation value p / v ²
Ask for.

When the fourth calculated value p / v ² was obtained for each of the spectral distribution characteristics shown in FIGS. 3 to 5, the results shown in the graph of FIG. 10 were obtained.

As is apparent from the graph of FIG. 10,
The fourth calculated value p / v ² becomes significantly large when the road is rough. Therefore, the determination unit 4 determines that the fourth calculated value p / v ² is as shown in FIG.
If it is not less than the fifth threshold value m ₅ (= 0.6) shown in the graph, the road is judged to be bad.

FIG. 11 shows a fourth embodiment of the road surface state detecting device of the present invention. In this device, an LP for filtering the contact sound signal from the microphone 1 is added to the device of the third embodiment.
It is equipped with F11. This LPF 11 extracts a low frequency band component having a frequency of 1 kHz or less from the contact sound signal,
This low frequency band component is transmitted to the signal processing unit 3.

The signal processing unit 3 repeatedly samples the low frequency band component from the LPF 11 500 times at a cycle of 500 Hz, supplies the low frequency band component to the determination unit 4 for each sampling, and at the same time, the speed detection unit 2 The velocity signal from is given to the determination unit 4.

When the speed signal is input, the judging section 4 makes a first judgment.
Calculated value v ² is obtained. When the low frequency band component is repeatedly given 500 times, the determination unit 4 obtains a variation p _L of the levels of these low frequency band components, divides this variation p _L by the first calculation value v ² , and Fifth calculated value p _L /
Find v ² .

When the fifth calculated value p _L / v ² was obtained for each of the spectral distribution characteristics shown in FIGS. 3 to 5, the results shown in the graph of FIG. 12 were obtained.

Since the low frequency band component sensitively changing according to the condition of the road surface is extracted from the contact signal and this low frequency band component is used as the material for the determination, the fifth calculated value p _{L is used.}
/ V ² changes clearly depending on the road surface condition. Therefore,
The determination unit 4 determines that the fifth calculated value p _L / v ² is the sixth threshold value m ₆
When (= 0.35) or more, it is determined that the road is bad, the fifth calculated value p _L / v ² is less than the sixth threshold m ₆ , and the seventh threshold m ₇ (= 0.15). ) Or more, it is determined to be a wet road, and if the fifth calculated value p _L / v ² is less than the seventh threshold value m ₇ , it is determined to be a dry road.

The present invention is not limited to the above-mentioned embodiments, but various modifications are possible. For example,
You may combine these embodiment suitably. Also,
The microphone 1 and the speed detection unit 2 can be applied in any kind. For example, as the speed detecting unit 2, a speed detecting sensor using the Doppler effect of radio waves or ultrasonic waves may be applied.

[0041]

As described above, in the device of the present invention, not only the contact sound between the tire and the road surface but also the speed of the vehicle is taken in to judge the road surface condition, so that more accurate judgment can be expected. You can

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing a first embodiment of a road surface state detecting device of the present invention.

FIG. 2 is a diagram illustrating an arrangement mode of microphones in the apparatus of FIG.

FIG. 3 (a) is a traveling speed of 40k on a dry road.
FIG. 3B is a graph showing a spectrum distribution characteristic of a signal indicating a contact sound between a vehicle tire and a road surface at m / h, and FIG. 3B shows a spectrum distribution characteristic of a signal indicating a contact sound at a traveling speed of 60 km / h. Graph diagram

FIG. 4 (a) is a running speed of 40k on a wet road.
FIG. 4B is a graph showing the spectrum distribution characteristic of the signal indicating the contact sound at m / h, and the traveling speed is 60 km / h.
Graph showing the spectral distribution characteristics when

FIG. 5 (a) is a traveling speed of 40 km on a rough road.
FIG. 5B is a graph showing the spectrum distribution characteristic of the signal indicating the contact sound when the speed is / h, and FIG.

FIG. 6 is a graph showing a second operation value obtained by a determination unit in the device shown in FIG.

FIG. 7 is a block diagram schematically showing a second embodiment of the road surface state detecting device of the present invention.

FIG. 8 is a graph showing a third calculated value for a low frequency obtained by a determination unit in the device shown in FIG.

9 is a graph showing a third calculated value for a high frequency obtained by a determination unit in the device shown in FIG.

FIG. 10 is a graph showing a fourth calculated value obtained in the third embodiment of the road surface state detecting device of the invention.

FIG. 11 is a block diagram schematically showing a fourth embodiment of the road surface state detecting device of the present invention.

12 is a graph showing a fifth calculated value obtained by a determination unit in the device shown in FIG.

[Explanation of symbols]

 1 Microphone 2 Speed detector 3 Signal processor 4 Judgment unit 6 Tire 7 Axle 11 Low pass filter 12 High pass filter

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Claims (5)

[Claims] 1. A contact sound detecting means for detecting a contact sound between a tire of a vehicle and a road surface, a speed detecting means for detecting a speed of the vehicle, a contact sound detected by the contact sound detecting means, and a speed detecting means. A road surface state detection device comprising: a determination unit that determines the state of the road surface based on the determined speed. 2. The determination means squares the speed of the vehicle, standardizes the level of the contact sound based on the first calculated value obtained by the square, and determines the second calculated value obtained by this normalization. The road surface state detection device according to claim 1, wherein the road surface state is determined based on the above. 3. The extracting means for extracting a band component of a predetermined frequency band from the contact sound detected by the contact sound detecting means, wherein the determining means squares the speed of the vehicle, The road surface state detection device according to claim 1, wherein the level of the band component is standardized based on the obtained first calculation value, and the road surface state is determined based on the third calculation value obtained by the standardization. 4. The determination means obtains a variation in the level of the contact sound with the passage of time, squares the speed of the vehicle, and varies the level of the contact sound based on the first calculated value obtained by the square. The road surface condition is determined based on the fourth calculated value obtained by normalizing
The road surface condition detecting device described in. 5. The extraction means for extracting a band component of a predetermined frequency band from the contact sound detected by the contact sound detection means is further provided, and the determination means obtains the variation of the level of the band component with the passage of time. , The speed of the vehicle is squared, the variation in the level of the band component is standardized based on the first calculated value obtained by the square, and the road surface state is calculated based on the fifth calculated value obtained by this standardization. The road surface state detection device according to claim 1, which detects a road surface.