JPH04105083A - Road condition detecting device - Google Patents

Abstract

PURPOSE:To enable a detectable road surface roughness range to be widely and accurately detected by transmitting an ultrasonic wave to a road, detecting the intensity of an irregular reflection wave received from the road and detecting a road condition on the basis of the detected wave intensity. CONSTITUTION:A transmitter 21 sends an ultrasonic wave having the prescribed frequency to a road 200 on the basis of an electrical signal having the prescribed frequency generated with an ultrasonic wave supply source 10. A receiver 22 is so positioned as to be capable of receiving irregular reflection waves, among reflection waves generated due to the aforesaid wave transmission. The received ultrasonic waves are converted into electrical signals and the signals amplified in an amplifier circuit 31 are detected in an AM detection circuit 32, thereby obtaining detection signals with the amplitude components thereof taken out. Thereafter, a high frequency components are eliminated from the signals in a low pass filter circuit 33, and a road condition detecting signal is outputted. Furthermore, a direction for the transmitter 21 to send waves to the road 200, another direction for the receiver 22 to receive the irregular reflection waves from the road 200 and a vehicle travel direction as shown by an arrow V are so set as to form an angle of approximately 90 degrees, thereby eliminating an error component attributable a Doppler effect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a road surface condition detection device, and particularly to a road surface condition detection device using ultrasonic waves.

[Conventional technology]

When controlling the driving of a vehicle, the condition of the road surface on which the vehicle is currently traveling is an important control parameter. As a physical quantity expressing the road surface condition, a value that quantitatively indicates the degree of unevenness of the road surface, that is, the roughness of the road surface is usually used.

Generally, two types of devices are used to detect such road surface conditions. The first device is a device that uses ultrasonic pulses, which emits ultrasonic pulses from a direction perpendicular to the road surface and receives reflected pulses from the road surface.

By measuring the round trip time of this pulse, the distance between the vehicle and the road surface is determined. The unevenness of the road surface is
It is detected as a minute change in the distance between the vehicle and the road surface. The second device emits ultrasonic waves as continuous waves instead of pulses from a direction perpendicular to the road surface, and receives reflected waves from the road surface. Then, information regarding the unevenness of the road surface is obtained based on the intensity of this reflected wave. In this case, the less uneven the road surface is, the smoother it is, the stronger the reflected waves will be.

A detection device based on this principle is known, for example, from Japanese Patent Application Laid-Open No. 62-12
It is disclosed in Japanese Patent No. 6377.

[Problem to be solved by the invention]

However, the above-mentioned first device has a problem in that the distance between the vehicle body and the road surface changes due to the vibrations of the vehicle, so the influence of the vehicle vibrations directly appears as an error. On the other hand, the second device described above does not detect the distance between the vehicle body and the road surface, so it is less susceptible to the influence of vehicle body vibrations. However, if the principle of detecting road surface conditions based on the intensity of reflected waves is used, another problem arises in that the range of detectable road surface roughness is limited. For this reason, the second device cannot detect the road surface condition of a rough road surface that is highly uneven and causes vibrations to the vehicle body.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a road surface condition detection device that can detect a wider range of road surface roughness and can perform accurate detection.

[Means for Solving the Problems] (1) The invention of Section 1 of the present application provides a road surface condition detection device that includes a transmitting means for transmitting ultrasonic waves toward the road surface, and a receiver for receiving the ultrasonic waves diffusely reflected from the road surface. and a detection means for detecting the intensity of the received diffusely reflected wave, and the road surface condition is detected based on this intensity.

(2) The invention of Section 2 of the present application is the road surface condition detection device according to the first invention, in which the transmitting means transmits ultrasonic waves in a direction substantially perpendicular to the traveling direction of the vehicle, and the receiving means transmits ultrasonic waves in the traveling direction of the vehicle. It is designed to receive ultrasonic waves from a direction substantially perpendicular to the direction.

[For production]

When ultrasonic waves are emitted onto a road surface, reflected waves and diffusely reflected waves (scattered waves) are generated on the road surface. To clearly distinguish between the two,
Hereinafter, in this specification, a normal reflected wave will be referred to as a regular reflected wave. All of the conventional devices described above detect road surface conditions using specularly reflected waves. That is, the road surface condition is detected by transmitting ultrasonic waves to a predetermined portion of the road surface and receiving reflected waves (regularly reflected waves) that are reflected at an angle equal to the incident angle with respect to the road surface at this time. The inventor of the present application has discovered that it is possible to detect road surface conditions using diffusely reflected waves instead of specularly reflected waves, and that the range of detectable road surface roughness is wider when using diffusely reflected waves. I did it.

As mentioned above, when ultrasonic waves are emitted onto the road surface, specularly reflected waves and diffusely reflected waves are generated on the road surface. The generation ratio of regularly reflected waves and diffusely reflected waves is determined by the degree of unevenness of the road surface, that is, the roughness of the road surface. If the road surface is smooth like a mirror, most of the waves will be specularly reflected. On the other hand, if the surface is so-called a rough surface with many irregularities on the order of the wavelength of the ultrasonic wave, most of the reflection will be diffused. Therefore, it can be determined that the roughness of the road surface is low if the ratio of specularly reflected waves is high, and the roughness of the road surface is high if the ratio of diffusely reflected waves is high. In this way, in principle, it is possible to detect the road surface condition using either method of measuring the intensity of specularly reflected waves or method of measuring the intensity of diffusely reflected waves. However, since specularly reflected waves have more directivity, conventionally it was common sense to perform detection based on the intensity of specularly reflected waves.

Contrary to this common sense, the invention of Section 1 of the present application expands the range of detectable road surface roughness by detecting the road surface condition based on the intensity of diffusely reflected waves.

The invention of Section 2 of the present application was made in order to eliminate the potential errors of the first invention.

While the vehicle is running, the diffusely reflected waves undergo a Doppler shift depending on the vehicle speed, and are received at a frequency different from the frequency at which they were transmitted. However, in general, the receiving sensitivity of an ultrasonic receiver (a transducer that converts ultrasonic waves into an electrical signal) changes depending on the frequency. Therefore, the reception sensitivity of the diffusely reflected wave changes depending on the vehicle speed, and this variation in reception sensitivity becomes a potential error. Therefore, in the invention of Section 2 of the present application, ultrasonic waves are transmitted in a direction substantially perpendicular to the traveling direction of the vehicle, and ultrasonic waves from the same direction are received.

In this way, the receiving frequency is always constant without undergoing Doppler shift, and potential errors are eliminated.

〔Example〕 .

The present invention will be described below based on illustrated embodiments. FIG. 1 is a block diagram showing the configuration of a road surface condition detection device according to an embodiment of the present invention. The components illustrated here are:
All of them will be mounted on the vehicle 100. The ultrasonic wave source 10 is a device that generates an electrical signal of a predetermined frequency, and based on this electrical signal, the transmitter 21 transmits the signal to the road surface 200.
This ultrasonic wave of a predetermined frequency is transmitted to. On the road surface 200, specularly reflected waves and diffusely reflected waves are generated based on this ultrasonic wave. The receiver 22 is placed at an appropriate position to receive the diffusely reflected waves. In general, the diffusely reflected waves spread out from the road surface in a hemispherical manner, so the placement of the receiver 22 does not require strict directionality, unlike when receiving specularly reflected waves. In this embodiment, as shown in Figure 1, ultrasonic waves are transmitted in a direction that forms an angle φ with respect to the road surface 200, and diffusely reflected waves that return in a direction that is oriented at the same angle φ are received. A transmitter 21 and a receiver 22 are attached at an angle.

Receiver 22 converts the received ultrasonic waves into electrical signals and provides them to amplifier circuit 31 . The signal amplified by the amplifier circuit 31 is further subjected to AM detection by the AM detection circuit 32. That is, a detected signal obtained by extracting the amplitude component of the signal can be obtained. Furthermore, a low-pass filter circuit 33 removes high frequency components due to the influence of wind and the like from this detection signal, and outputs a road surface condition detection signal. The road surface condition detection signal output in this way becomes a signal directly indicating the road surface roughness.

Here, the relationship between the signal strength detected in this way and the road surface roughness is as shown in the graphs shown in FIGS. 2 and 3. Figure 2 is a graph showing the relationship between the signal strength of the specularly reflected wave used in the conventional device and road surface roughness, and Figure 3 is a graph showing the relationship between the signal strength of the diffusely reflected wave used in this device and the road surface roughness. It is a graph showing a relationship. As shown in Figure 2, the signal strength of the specularly reflected wave attenuates as the road surface becomes rougher, or the signal strength of the diffusely reflected wave decreases as the road surface becomes rougher.
As shown in the figure, it increases as the road surface roughness becomes rougher. In this way, both specularly reflected waves and diffusely reflected waves contain information regarding road surface roughness, and information on road surface roughness can be obtained by detecting either of them. Reflected waves were used. However, the inventor of the present application recognized that detection using diffusely reflected waves expands the detection range of road surface roughness. Now, when the noise level of the processing system such as the ultrasonic transmitter/receiver and the detection circuit is taken as Io, the detection range of road surface roughness is range a as shown in Figure 2 when specularly reflected waves are used. However, if diffusely reflected waves are used, the range will be as shown in FIG. To illustrate this range with a specific example, if specular reflection waves are used, is it possible to detect the roughness of a road surface with minute irregularities?
If the unevenness becomes large enough to cause vibrations to the vehicle, detection becomes impossible. On the other hand, when diffusely reflected waves are used, the detectable range expands from irregularities that cause the vehicle to slip to irregularities that are large enough to cause vibrations to the vehicle. In general, the lower limit of road surface roughness is sufficient if it can detect even irregularities to the extent of slipping, and it can be seen that it is appropriate to use diffusely reflected waves as a road surface condition detection device mounted on a vehicle.

In this way, the use of diffusely reflected waves has the advantage that the detection range of road surface roughness is wider than when specularly reflected waves are used. However, if detection using diffusely reflected waves is performed while the vehicle is running, it will include potential error factors. This is because the diffusely reflected waves are affected by the Doppler effect as the vehicle travels. In the conventional device using specularly reflected waves, the influence of the Doppler effect is canceled out between the transmitted wave and the reflected wave, so the running of the vehicle does not become an error factor. However, due to the Doppler effect, the frequency of the diffusely reflected wave is displaced by an amount corresponding to the vehicle speed. Moreover, the receiving sensitivity of the receiver 22 is as shown in the graph shown in FIG.
Depends on receiving frequency. Therefore, when the frequency of the diffusely reflected wave changes depending on the vehicle speed, the reception sensitivity of the receiver 22 varies depending on the frequency, so the signal strength of the diffusely reflected wave that is finally detected varies depending on the vehicle speed.

In order to eliminate such potential error factors, in this embodiment, the transmitter 21 and receiver 22 are mounted in the orientation shown in FIG. FIG. 5 is a view of the vehicle 100 viewed from above, and the direction of arrow V is the traveling direction of the vehicle. Let θ be the angle formed by the direction in which the transmitter 21 transmits ultrasonic waves toward the road surface 200, the direction in which the receiver 22 receives diffusely reflected waves from the road surface 200, and the vehicle traveling direction indicated by arrow V. It is set so that it becomes θ-906. That is, the transmitted wave and the diffusely reflected wave take an arbitrary angle φ with respect to the road surface 200 when viewed from the front of the vehicle as shown in FIG. 1, but when viewed from above the vehicle as shown in FIG. be at right angles to. In other words, the propagation paths of the transmitted waves and the diffusely reflected waves are included in a plane perpendicular to the traveling direction. If such a setting is made, the vehicle speed component in the propagation direction of the transmitted wave and the diffusely reflected wave becomes zero, and the diffusely reflected wave is received at the same constant frequency as the transmitted wave without undergoing Doppler shift. Therefore, error components caused by the Doppler effect can be removed.

FIGS. 6 and 7 are graphs showing the results of removing errors caused by the Doppler effect using the method described above. That is, when the direction in which the transmitter 21 transmits ultrasonic waves toward the road surface 200 and the direction in which the receiver 22 receives diffusely reflected waves from the road surface 200 are set in the same direction as the vehicle traveling direction (θ=0°). The measurement results (Fig. 6) and the measurement results when the vehicle is oriented perpendicular to the running direction (θ-90') (
FIG. 7) is a graph showing. In the case of θ-0°,
The signal strength of the diffusely reflected wave also fluctuates as the vehicle speed fluctuates, but in the case of θ-90', the signal strength is almost constant without being affected by the vehicle speed fluctuation.

In this way, by setting θ-90', it becomes possible to accurately detect the road surface condition.

Note that, in practice, it is not necessary to set exactly θ-906, but it is sufficient to set it so that the potential error is suppressed to within an allowable range.

〔Effect of the invention〕

As described above, according to the present invention, since the road surface condition is detected based on the intensity of the diffusely reflected waves, the range of detectable road surface roughness can be expanded.

In addition, ultrasonic waves are transmitted in a direction almost perpendicular to the direction of travel of the vehicle, and ultrasonic waves from the same direction are received.
The receiving frequency is always constant without undergoing Doppler shift, and potential errors associated with measurements using diffusely reflected waves are eliminated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a road surface condition detection device according to an embodiment of the present invention, FIG. 2 is a graph showing the relationship between the signal strength of specularly reflected waves and road surface roughness, and FIG. 3 is a graph showing the relationship between the signal strength of specularly reflected waves and road surface roughness. A graph showing the relationship between signal strength and road surface roughness, Fig. 4 is a graph showing the reception sensitivity of the ultrasonic receiver, and Fig. 5 shows the orientation of the transmitter and receiver in the road surface condition detection device according to the present invention. The top view, Figures 6 and 7 show the mounting angles of the transmitter and receiver at θ-0, respectively.
9 is a graph showing the influence of vehicle speed on the detection signal strength when `` and θ-90''. For road surfaces 0 silk 2 1 @ surface roughness figure 3

Claims (2)

[Claims] (1) comprising a transmitting means for transmitting ultrasonic waves toward the road surface, a receiving means for receiving the ultrasonic waves diffusely reflected from the road surface, and a detecting means for detecting the intensity of the received diffusely reflected waves,
A road surface condition detection device that detects a road surface condition based on the intensity. (2) In the road surface condition detection device according to claim 1, the transmitting means transmits ultrasonic waves in a direction substantially perpendicular to the direction of travel of the vehicle, and the receiving means transmits ultrasonic waves from a direction substantially perpendicular to the direction of travel of the vehicle. A road surface condition detection device characterized in that each is provided so as to receive the following information.