JPS6293657A - Road condition detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a device for detecting road surface conditions using ultrasonic waves, and in particular to a device for detecting road surface conditions using ultrasonic waves. This invention relates to a situation detection device.

[Prior art]

In automobiles, in order to automatically and optimally control braking systems and switching between two-wheel drive and four-wheel drive, etc., road surface conditions (
It is necessary to accurately detect paved roads, gravel roads, muddy roads, snowy roads, etc.

Therefore, the present applicant has already applied for a road surface condition detection device that accurately detects road surface conditions using ultrasonic waves (Patent Application No. 130985 of 1982).

In the above road surface condition detection device, ultrasonic waves are emitted from a transmitter toward the road surface, reflected waves from the road surface are detected by a receiver, and the level of the detected reflected waves is compared with a predetermined reference value. The system is configured to detect road conditions by

For example, in the case of a hard road surface such as a concrete paved road, the level of reflected waves is high, and in the case of a soft road surface such as a muddy or snowy road, the level of reflected waves is low.

Therefore, by comparing the reflected wave level with the reference value as described above, it is possible to
It is possible to determine whether the vehicle is traveling on a road (μ is the coefficient of friction) or on a low μ road such as a muddy or snowy road.

By using the road surface condition detection device as described above, an optimal control device for a braking device or an automatic switching device between two-wheel drive and four-wheel drive (utility model registration No. 151700 of 1982 filed by the applicant), etc. can be realized.

[Problem that the invention seeks to solve]

However, in the road surface condition detection device described above.

Since the level of the reflected waves was used to judge the road surface condition, if the surface of the transducer became dirty or the intensity of the ultrasonic waves transmitted or received changed due to changes over time, the same The level of reflected waves detected also changes with respect to the road surface.

Therefore, there was a risk that the road surface condition would be misjudged.

For example, if the sensitivity of the transducer decreases due to changes over time, the level of reflected waves will decrease, so there is a risk that a paved road with relatively low reflection intensity may be mistakenly determined to be a snowy road.

The present invention aims to solve the problems of the prior art as described above.

[Means to solve the problem]

In order to achieve the above object, in the present invention, the level of the detected reflected wave or the standard for determining the road surface condition is determined based on the level of the direct wave that directly reaches the receiver from the transmitter without being reflected on the road surface. By changing the value, the road surface condition judgment criteria are automatically adjusted according to the level of direct waves. [Embodiment of the Invention] FIG. 1 is a diagram showing an embodiment of the present invention.

In the figure, the transmitter 2 is driven by the output of the transmitter circuit 1-, and emits ultrasonic waves S□ toward the road surface via the transmitter horn 3.

Further, the receiver 5 receives the reflected wave S2 from the road surface via the receiver horn 6, and sends a received signal to the receiver circuit 4.

The control device 7 repeatedly sends a trigger signal to the transmitting circuit 1 at a predetermined period, and each time the trigger signal is given, the transmitting circuit 1 sends out an ultrasonic drive output to drive the transmitter 2 .

Further, the control device 7 constantly detects the output of the receiving heat exchanger 4,
Performs predetermined calculations (details will be described later) to determine road conditions,
A judgment signal S4 is output according to the result.

On the other hand, when the ultrasonic wave S1 is emitted from the transmitter 2, before the reflected wave S2 from the road surface reaches the receiver 5.

Directly from the transmitter 2 to the receiver 5 via the vibration of the housing 8,
Alternatively, a so-called direct wave S, which propagates directly through the air, reaches the receiver horn 6 from the transmitter horn 3.

FIG. 2 is a diagram showing the above-mentioned transmitted waveform and received waveform, where the direct wave S is received immediately after the ultrasonic wave is transmitted, and the reflected wave S2 from the road surface is received much later than that.

Further, the level V of the direct wave S changes depending on the sensitivity of the transmitter and the receiver, regardless of the road surface condition.

Therefore, when the gains of the transmitter 2 and the receiver 5 change due to changes over time, etc., the level V4 of the direct wave S3 changes.

Since the level v2 of the reflected wave S2 changes depending on both the road surface condition and the gain of the transducer, the level v2 of the reflected wave S or the standard for determining the road surface condition depends on the level of the direct wave S3. By changing the value level, it is possible to always accurately judge the road situation regardless of changes over time.

Hereinafter, the content of calculations in the control device 7 will be explained.

FIG. 3 is an embodiment of a flowchart showing the calculation contents of the present invention.

In FIG. 3, first, at Pl, the level V of the direct wave S,
and the level v2 of the reflected wave S2.

Next, in P2, the ratio between the reflected wave and the direct wave, P=
By calculating V2/V, the level v2 of the reflected wave S2 can be calibrated by the level V of the direct wave S.

Next, at P3, the above value P is the reference value P for road condition judgment.
. Determine whether or not the above is true.

If P3 is YES, that is, P is P. In the second case, the process goes to P4, determines that the road surface is a high μ road (concrete paved road, etc.), and outputs a determination signal accordingly.

If the answer is No in P3, the process goes to P5, where it is determined that the road surface is a low μ road (muddy, snowy, etc.) and a determination signal thereof is output.

As described above, if the level v2 of the reflected wave S2 is calibrated by the level V of the direct wave S3, there is no possibility of misjudgment caused by changes in the transducer or the like over time.

Next, FIG. 4 is another embodiment of a flowchart showing the calculation contents of the present invention.

In FIG. 4, first, at P6, the level V of the direct wave S,
Read the level v2 of the reflected wave S2.

Next, at P7, the level V of the direct wave S is set to the initial setting value V.

Determine whether or not there has been a change from .

If No at P7, it indicates that vl has not changed, that is, the sensitivity of the transducer has not changed, so go to P8 and check that the level v2 of the reflected wave S2 is 00, the reference value for road condition judgment. Determine whether or not the value is greater than or equal to the value.

If YES in P8, the process goes to P9 and outputs a high μ road judgment signal, and if NO in P8, goes to Plo and outputs a low μ road judgment signal.

On the other hand, if P7 is YES, the direct wave S is generated.

The level eyebrows are the initial setting value V. If there is a change from
Since it indicates that the sensitivity etc. of the transducer is changing, Pl
Go to l and select the level V of the direct wave and its initial setting ■. Calculate which ratio, ie, S=v/V.

Next, PI3 is the reference value Q for determining road surface conditions. A value Qn is calculated by multiplying by the above S.

As a result, the reference value for road surface condition judgment is the direct wave S.

It can be calibrated at the level V□.

Next, in PI3, it is determined whether the level v2 of the reflected wave S2 is equal to or higher than the above-mentioned calibrated reference value Qn.

If PI3 is YES, it goes to PI3 and outputs a high μ road judgment signal, and if PI3 is No, it goes to PI3 and outputs a low μ road judgment signal.

As described above, by changing the reference value for road surface condition judgment according to the level V of the direct waves S, it is possible to automatically adjust the change in the gain of the transducer due to changes over time or the like.

Next, FIG. 5 is a diagram showing another embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate the same parts.

In the embodiment shown in FIG. 1, the level of the direct wave S3 is low, and detection tends to become unstable.

In order to solve the above problem, the embodiment shown in FIG. Direct wave S to the vessel,
It is designed to reliably transmit at a high level.

This makes it possible to increase the level of direct waves and improve accuracy.

Note that the control device 7 can be configured using a digital device such as a microcomputer, but it can also be configured using a normal analog device. For example, the third
When realizing the function shown in the figure with an analog circuit, transmitter 2
A circuit that distinguishes and detects direct waves and reflected waves based on the time from when the ultrasonic wave is emitted to when the received signal is detected by the receiver, and a division circuit that divides the value of the reflected wave by the value of the direct wave. and a comparison circuit that compares the result of division with a predetermined reference value.

〔Effect of the invention〕

As explained above, the present invention is configured to automatically adjust the judgment criteria for road surface conditions using direct waves, so if the transmitter or receiver becomes dirty or changes over time, etc. This provides an excellent effect in that the road surface condition can be reliably judged even when the sensitivity of the transducer changes.

[Brief explanation of drawings]

Fig. 1 is a diagram of one embodiment of the present invention, Fig. 2 is a diagram of transmission and reception waveforms,
FIGS. 3 and 4 are flowchart embodiments showing the calculation contents of the present invention, and FIG. 5 is another embodiment of the present invention. <Explanation of symbols> 1... Transmitting circuit 2... Transmitter 3... Transmitter horn 4... Receiving circuit 5... Receiver 6... Receiver horn 7...・Control device 8...Casing 9...Transmission management agent Junnosuke Nakamura, patent attorney Figure 4〕tJ)←

Claims (1)

[Claims] A transmitter emits ultrasonic waves toward the road surface, a receiver detects reflected waves from the road surface, and the road surface condition is determined by comparing the level of the detected reflected waves with a predetermined reference value. In the road surface condition detection device, the level of the detected reflected wave or the reference value is determined according to the level of the direct wave that directly reaches the receiver from the transmitter without being reflected on the road surface. What is claimed is: 1. A road surface condition detection device comprising a means for changing a direct wave, and automatically adjusting a criterion for determining a road surface condition according to a level of a direct wave.