JPH0528326B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention is configured to determine whether or not there are irregularities on the road surface based on the level and frequency of a beat signal, thereby improving the reliability of the device.

[Industrial application field]

The present invention relates to a road surface condition sensor that detects unevenness on a road surface.

[Conventional technology]

A road surface condition sensor that detects road surface irregularities is required, for example, when the suspension of a vehicle is automatically changed depending on the road surface condition.

Although it is possible to detect the road surface condition using various methods, for example, it is possible to detect the road surface condition using a Doppler radar. In other words, the level of the beat signal of the Doppler radar is higher on uneven road surfaces than on flat roads, so the road surface condition can be detected by comparing the beat signal level with an appropriate threshold. It becomes possible to do so.

However, since the radiation beam of the Doppler radar has a width, the level of the beat signal constantly changes even if the road surface condition is constant. Therefore, as described above, simply comparing the level of the beat signal with an appropriate threshold value has the problem of lack of reliability.

[Problem that the invention seeks to solve]

The present invention solves the above-mentioned problems, and its purpose is to enable reliable detection of road surface irregularities using a Doppler radar.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention includes a transmitting/receiving section that transmits an output of a predetermined frequency, receives a reflected wave, and outputs a beat signal based on a transmitted signal and a received signal, as shown in FIG. 1, a detecting means 2 for detecting the vehicle speed of the vehicle, a first determining means 3 for determining whether there is an unevenness on the road surface based on the level of the beat signal output from the transmitting/receiving section 1, and the transmitting/receiving section 1. a second determining means 4 for determining whether or not there are irregularities on the road surface based on the frequency of the beat signal output from the section 1 and the detection result of the detecting means 2; and the first and second determining means. A third determining means 5 is provided which determines that the road surface is uneven only when both means 3 and 4 determine that the road surface is uneven.

[Effect]

Only when the determination results based on both the level and frequency of the beat signal indicate that there are irregularities, the third determining means 5 determines that there are irregularities on the road surface, so that irregularities on the road surface can be reliably detected. be able to.

〔Example〕

FIG. 2 is a block diagram of an embodiment of the present invention, in which 11 is an antenna for transmitting and receiving, 12 is a directional coupler, 13 is a mixer circuit, 14 is an oscillator, and 15 is a directional coupler.
is a bandpass filter, 16 and 17 are comparators, 1
8 is an input section; 19 is a vehicle speed sensor that detects vehicle speed;
20 is a microprocessor.

The oscillator 14 outputs a signal of a predetermined frequency, and the antenna 11 is connected to the oscillator 14 via the directional coupler 12.
By applying the output signal of , radio waves of a predetermined frequency are radiated. Radio waves radiated from the antenna 11 are reflected on the road surface and enter the antenna 11.
The received signal of the antenna 11 is applied to the mixer circuit 13, where it is sent to the oscillator 1 via the directional coupler 12.
It is mixed with the transmission signal added from 4.
A beat signal created by mixing the transmitted signal and the received signal in the mixer circuit 13 is applied to the comparators 16 and 17 via the bandpass filter 15.

For example, if the vehicle is traveling on a road surface as shown in FIG. 3A at a speed vd, the level of the output signal a of the bandpass filter 15 becomes high in uneven portions, as shown in FIG. 3B. Furthermore, the frequency f1 of the signal a when driving on a flat road is shown in the following equation (1), and the frequency f2 of the signal a when driving on an uneven road surface is shown in the following equation (2). Become something.

f1=fo・2Vd・cosα/C...(1) f2=fo・2Vd・sin(α+β)/C...(2) However, in equations (1) and (2), fo is the transmission signal. The frequency, α represents the mounting angle of the antenna 11, β represents the inclination angle of the road surface, and C represents the speed of light.

As can be seen from Figure 3A and equations (1) and (2), when the road surface is uneven, compared to when the road surface is flat,
The level of the output signal a of the bandpass filter 15 increases and its frequency decreases.

The comparators 16 and 17 respectively receive the signal a and the threshold T1,
While signal a is higher compared to T2 (T1<T2),
The output signals b and c are set to "1".
The microprocessor 20 also receives the output signals b,
Based on c and the detection result of the vehicle speed sensor 19, the process shown in the flowchart of FIG. 4 is performed to determine whether there are any unevenness on the road surface and output a suspension control signal.

That is, when the output signal a of the bandpass filter 15 becomes larger than the threshold value T2 and the output signal c of the comparator 17 becomes "1" (step S1), the microprocessor 20 first outputs the output signal b of the comparator 16.
The calculation shown in the following equation (3) is performed based on the frequency f of , and the vehicle speed V' is determined (step S2).

V'=f・C/2・fo・cosα (3) Next, the microprocessor 20 reads the detection result of the vehicle speed sensor 19, that is, the true vehicle speed Vd (step S3), and then uses the following equation (4). It is determined whether the indicated relationship is satisfied (step S4).

|Vd−V′|<ε...(4) Here, as can be seen from equation (1) above, if the road surface is flat, the vehicle calculated by calculating equation (3) in step S2 Since V' is equal to the detection result Vd of the vehicle speed sensor 19 read in step S3, the judgment result in step S4 is YES.
If so, the road surface is flat, and if the determination result is NO, the road surface has unevenness. If the judgment result in step S4 is YES, the microprocessor 20 returns to the processing in step S1, and if the judgment result is NO, it outputs the suspension control signal (step S5) and then returns to the processing in step S1. return.

In this way, in this embodiment, the bandpass filter 1
Since it is determined whether or not the road surface is uneven based not only on the level of the output signal a (beat signal) of No. 5 but also on the level and frequency, it is compared to the case where the judgment is based only on the level. This makes it possible to accurately judge the road surface condition.

Although Doppler radar was used in the above embodiment, it is of course possible to use ultrasonic waves.

〔Effect of the invention〕

As explained above, the present invention has a transmitting/receiving unit (in the embodiment, the antenna 11, direction (consisting of a frequency coupler 12, a mixer circuit 13, an oscillator 14, a bandpass filter 15, etc.), a detection means such as a vehicle speed sensor that detects the vehicle speed, and based on the level of the beat signal output from the transmitter/receiver section. a comparator 16 that determines whether there are irregularities on the road surface;
a comparator 17 that determines whether or not there are irregularities on the road surface based on a first determining means comprising a microprocessor 20 and a detection result of the detecting means of the frequency of the beat signal output from the transmitter/receiver section; ,
Only when the second determining means consisting of the microprocessor 20 and the first and second determining means both determine that the road surface is uneven, the third determining means (in the embodiment) determines that the road surface is uneven. (This is realized by performing steps S1 to S4 in the microprocessor 20).
This has the advantage that road surface irregularities can be reliably detected regardless of level fluctuations in the beat signal.

[Brief explanation of the drawing]

1 is a block diagram of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is an explanatory diagram of the operation of FIG. 2, and FIG. 4 is a flowchart showing the processing contents of the microprocessor 20. It's a chat. 1 is a transmitter/receiver unit, 2 is a detection means, 3 to 5 are first to third determination means, respectively, 11 is an antenna, and 12
13 is a directional coupler, 13 is a mixer circuit, 14 is an oscillator, 15 is a bandpass filter, 16 and 17 are comparators, 18 is an input section, 19 is a vehicle speed sensor, and 20 is a microprocessor.

Claims (1)

[Scope of Claims] 1. A transmitting/receiving unit that transmits a signal of a predetermined frequency, receives a reflected wave, and outputs a beat signal based on the transmitted signal and the received signal; a detection means that detects the vehicle speed of the vehicle; and the transmitting/receiving unit. a first determining means for determining whether or not there is an unevenness on the road surface based on a level of a beat signal output from the transmitter/receiver; and a frequency of the beat signal output from the transmitter/receiver and a detection result of the detector. a second determining means for determining whether or not the road surface is uneven based on the above; and a third determining means for determining that the road surface is uneven only if both the first and second determining means have determined that the road surface is uneven. A road surface condition sensor characterized by comprising: determination means.