JPS6247566A - Road condition detector - Google Patents

Abstract

PURPOSE:To obtain good detecting sensibility even in case of the reflection factor of a road surface to be detected being not so much different from the ordinary road surface by detecting the surface state which using the reflected wave inputted after repeating the reflection between the surface and the lower face of a car body as the measuring object. CONSTITUTION:A delay circuit 16 is driven by a timer at the signal rise time of the trigger signal (b) outputted from a trigger signal oscillator 6 and outputs a delay signal (f) after the prescribed time TD. This time TD is set at the slightly smaller in value than the predicting time when the (n)th reflecting wave arrives after the signal (b) to be decided by the distance between the surface and vehicle being oscillated. On the other hand a sample and hold circuit 15 is actuated after the inputting of the signal (f) and inputs the envelope of the (n)th reflecting wave Sn from an envelope follower circuit 10 to compare the mean intensity, for instance, of the detected wave and the reference intensity of the (n)th reflecting wave. And if the detected wave intensity be smaller than the reference intensity it is judged that the detected surface L is a snow road, for instance, and the inner part counter is counted up by one. A statistics processing circuit 12 outputs a snow road detecting signal when the number of times of counting is more than the prescribed times.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a road surface condition detection device for a vehicle.

[Description of prior art]

2. Description of the Related Art Conventionally, a technique for measuring ground distance using an ultrasonic sensor is known, as shown in Japanese Patent Laid-Open No. 57-182544.

On the other hand, as proposed in U.S. Patent Application No. 59-151700 (unpublished), in view of the fact that the reflected wave intensity of ultrasonic waves emitted towards the road surface varies depending on the road surface condition, the reflected intensity is measured and There are also attempts to detect the state.

An overview of such a conventional road surface condition detection device will be explained with reference to FIGS. 3 and 4.

As shown in FIG. 3, the road surface condition detection device 1 includes a drive circuit 2.
, an ultrasonic sensor 3 attached to the lower surface C of the vehicle facing the road surface, and a signal processing circuit 4. .

The drive circuit 2 has a carrier wave excavator 5, a trigger signal oscillator 6, and a signal synthesis circuit 7 which inputs the output signals of these oscillators 5.6 to input terminals of a two-man AND gate, respectively.

The carrier wave generator 5 generates a carrier wave signal a of a predetermined frequency as shown in FIG. 4(a). The trigger signal oscillator 6 is activated intermittently, for example, from time TO to time Δ
Outputs 1~Riga signal @b for only T. Signal synthesis circuit 7
Inputs both the signals shown in Fig. 4(a) and (b) to the two input terminals respectively, and as shown in Fig. 4(C), the time period during which the oscillation trigger signal is output is Δt. Outputs drive signal C.

The ultrasonic sensor 3 has a speaker 8 and a microphone 9.

The speaker 8 receives a driving signal C as shown in FIG. 4(C), and an ultrasonic signal So with an intensity proportional to this signal intensity.
Fire it towards the road. Microphone 9 is 1 from the road.
The next reflected wave S+ is input to form a reflected wave signal wave d as shown in FIG. 4(d).

The signal processing circuit 4 includes an envelope follower circuit 10, a sample and hold circuit 11, and a statistical processing circuit 1.
2.

The envelope follower circuit 10 detects the envelope e of the reflected wave signal d, as shown in FIG. 4(e). The sample-and-hold circuit 11 has an envelope 1! shown in FIG. 4(e). For example, if the standard intensity 1c is compared with the average intensity Ia, and the average intensity la is less than the standard intensity 1c, it is determined that the road surface is a snowy road, considering that the reflectance of the road surface is smaller than that of a normal road surface. Detected and increments the internal counter by 1.

If the reference intensity IC is optimized, the reflected wave intensity will be the peak intensity! Of course, +1 can be used.

The statistical processing circuit 12 observes the contents of the detection counter after the trigger signal is repeatedly oscillated a predetermined number of times, for example, five times, and generates a snow road detection signal when the count is a predetermined number of times, for example, three times or more. Output.

According to the road surface condition detection device 1 having the above configuration, the microphone 9 receives the primary reflected wave S1 of the ultrasonic SO intermittently generated from the speaker 8 to form the reflected wave signal d, and the signal processing circuit 4 detects the envelope e of the reflected wave signal d, and detects, for example, a snowy road based on this envelope e;
It is possible to statistically process this detection state to detect a more accurate road surface state.

However, in the conventional road surface condition detection device 1 as described above, the signal processing circuit 4 is configured to process the signal based on the first-order foul wave S+. There is a problem in that the detection sensitivity is low when the reflectance of the road surface is not very different from the reflectance of a normal road surface, such as in the case of a snowy road.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned problems and provide a road surface condition detection device that has good detection sensitivity even when the reflectance of the road surface to be detected is not very different from that of a normal road surface.

[Summary of the invention]

In order to achieve the above object, the present invention includes a drive circuit that intermittently outputs a drive signal for generating ultrasonic waves; an ultrasonic sensor having a speaker that detects the reflected waves of the ultrasonic waves emitted from the speaker and a microphone that detects the reflected waves from the road surface of the ultrasonic waves emitted from the speaker; A road surface condition detection device is constructed by including a signal processing circuit that detects a road surface condition by comparing the reflected wave intensity of a reflected wave with a reference intensity.

(Operation of the invention) In the road surface condition detection device configured as described above, the reflected wave signals of multiple reflected waves are compared and processed in the signal processing circuit. If the coefficient is β, the composite reflectance of the n-th reflected wave is αnβn-1, so even if the difference △α in the road surface reflectance α is small, the difference will be expanded in the composite reflectance of multiple orders, and the detection accuracy will increase. becomes good.

[Explanation of Examples]

An embodiment of the present invention will be described based on FIGS. 1 and 2.

FIG. 1 is a circuit diagram showing a road surface condition detection device according to an embodiment of the present invention.

The road surface condition detection device 13 includes a drive circuit 2 and an ultrasonic sensor 3.
and a signal processing circuit 14.

The configurations of the drive circuit 2 and the ultrasonic sensor 3 are the same as those shown in the conventional example.

The signal processing circuit 14 includes an envelope follower circuit 10 and a statistical processing circuit 12 similar to those shown in the conventional example. A sample-and-hold circuit 15 similar to the sample-and-hold circuit 11 shown in the conventional example is provided between the circuits 10 and 12, and the trigger of this circuit 15 and the drive circuit 2 is connected to the output side of the signal oscillator 6. A delay circuit 16 is provided between them.

The delay circuit 16 is driven by a timer at the rising edge of the trigger signal b (see FIG. 4(b)) output from the trigger signal oscillator 6, and outputs the delayed signal f after a predetermined time TD. This time To is a value that is a little smaller than the predicted time when the n-th (e.g., 4th-order) reflected waves arrive after the 1st to 4th-order reflected waves are oscillated, which is determined by the distance between the road surface and the vehicle, such as 3rd and 4th-order reflected waves. This is set at the midpoint of the reflected wave arrival time.

The sample-and-hold circuit 15 is activated after the delay signal 2 is inputted, inputs the envelope of the n-th reflected wave Sn from the envelope follower circuit 10, and calculates, for example, the average intensity and the n-th reflected wave of the detected wave. Compare the wave reference intensity IC', and if the detected wave intensity I is smaller than the reference intensity IC-,
For example, it determines that the detected road surface is a snowy road, and operates to increment an internal counter by one. Statistical processing circuit 12
The operation is the same as the conventional example.

The operation of the road surface condition detection device 13 shown in FIG. 1 will be explained using FIG. 2.

First, the drive circuit 2 and the ultrasonic sensor 3 are shown in FIG.
) to (C). However, in this example, the microphone 9 of the ultrasonic sensor 3 receives not only the primary reflected wave S+ reflected from the road surface (see Figure 3), but also the repeated reflection between the road surface and the lower surface C of the vehicle body. It is a requirement that the n-th reflected wave 3n after the process is also detected.

Therefore, the envelope follower circuit 10 inputs the first, second, . . . , nth-order reflected wave signals d, and performs an envelope detection process for each reflected wave 3n.

As shown in Fig. 2, if the intensity of the ultrasonic waves emitted from the speaker 8 is expressed as IO1, the reflectance of the road surface is α, and the reflectance of the lower surface C of the vehicle body is β, then The reflected wave intensity of . . . becomes αlo, α2β■O1, etc. In the figure, two dot-dashed lines and a two-dot chain line indicate a normal road surface L1 and a snowy road L2 where the reflectance α is not significantly different from the normal road surface L1.

As described above, the number-and-hold circuit 15 is activated after receiving the delay signal f, so it is activated after time TS in FIG. Then, the intensity I of the fourth reflected wave is compared with the reference intensity IC', and if the detected intensity is smaller than the reference intensity 1c, it is detected that the road surface is a snowy road L2, and the internal counter is incremented by 1. be. Here, the reference strength may be set to α3β3 times the IC shown in the conventional example.

With the above configuration and operation, in the road surface condition detection device 13 according to the present embodiment, the n-th (for example, the 4th-order) reflected waves are measured except for the 1st-order, and the reflected waves of the n-th order (for example, the 4th-order) are measured, and the Even if there is a road surface condition, it is possible to detect the road surface condition with good accuracy.

In addition, in the above embodiment, an example was shown in which the sample and hold circuit 15 can detect the n-th reflected wave by providing the delay circuit 16, but the arrival of the n-th reflected wave requires the detection of the envelope by the envelope 17407 circuit 10. It can be detected in Figure 4(e). That is, the envelope follower circuit 10
It is possible to determine that the detected wave for the first time is an n-th reflected wave.

However, the ultrasonic sensor 3 is also affected by so-called wraparound noise, so as shown in this example, the delay time TO
It is better to mask only the

〔Effect of the invention〕

As explained above, in this invention, the road surface condition is detected by using the reflected wave input after repeated reflections between the road surface and the lower surface of the vehicle body as the measurement target, so that the reflectance of the road surface to be tested is higher than that of a normal road surface. Even when there is no difference, the detection sensitivity is good.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a road surface condition detection device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of its operation. FIG. 3 is a circuit diagram of a conventional road surface condition detection device, and FIG. 4 is an explanatory diagram of its operation. 2... Drive circuit 3... Ultrasonic sensor 14
...Signal processing circuit 16...Delay circuit Fig. 1 13 Road surface condition detection device 14 Signal processing circuit Fig. 2 ■, -ri summer 0

Claims (1)

[Claims] (1) A drive circuit that intermittently outputs a drive signal for generating ultrasonic waves, a speaker attached to the underside of the vehicle that generates ultrasonic waves for a certain period of time in response to the drive signal from the drive circuit, and a speaker that generates ultrasonic waves for a certain period of time. an ultrasonic sensor having a microphone that detects reflected waves of ultrasonic waves from a road surface, and a reference and the reflected wave intensity of reflected waves detected by the microphone after repeated reflections between the road surface and the lower surface of the vehicle. A road surface condition detection device comprising: a signal processing circuit that detects a road surface condition by comparing it with an intensity.