JPH11306486A - Ultrasonic vehicle sensor and vehicle sensing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle sensor having a sufficient sensitivity capable of performing stable vehicle detection even under an environment with a large background reflection wave. SOLUTION: This sensor is provided with a background reflection wave storage means 17 for storing background reflection waves depending on an install ation environment without containing vehicle reflection wave component, a reference level fluctuating means 20 for fluctuating the reference level of reflection waves at each time after the emission of ultrasonic waves, and a correction value setting means 18 for setting the amount of fluctuation at each time after the emission of ultrasonic waves at the reference level, wherein the correction value setting means 18 sets the fluctuation amount of the reference level so as to lower the level of background reflection waves at each time after the emission of ultrasonic waves. Even in an environment in which strong background reflection waves exist, erroneous sensing caused by background reflection waves can be prevented without deteriorating reception sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic vehicle detector for detecting a traveling vehicle using ultrasonic waves and a method of detecting the vehicle, and more particularly, to an ultrasonic vehicle detector for detecting an erroneous detection due to ultrasonic waves reflected from a background. This is to prevent occurrence.

[0002]

2. Description of the Related Art An ultrasonic vehicle detector detects the presence or absence of a vehicle based on the time when a reflected wave of a transmitted ultrasonic wave returns. However, when the ultrasonic vehicle detector is installed in a tunnel or the like, a background reflected wave is generated by an obstacle such as a ceiling.

FIG. 7 shows a reception waveform and a reception timing of a reflected wave received by a conventional ultrasonic vehicle sensor. Here, the horizontal axis indicates the time axis, and the vertical axis indicates the reception level.

[0006] Ultrasonic wave transmitted from ultrasonic vehicle sensor 1
Is transmitted, and when a vehicle is present, a vehicle reflected wave 2 which is a reflected wave from the vehicle reaches the vehicle sensor. When there is no vehicle to be detected, the road surface reflected wave 4 reflected on the road surface reaches the vehicle detector. The background reflected wave 3 reflected from a background such as a ceiling reaches the vehicle detector earlier than the road surface reflected wave 4.

[0005] In the vehicle sensor, the reception level of the reflected wave is
The vehicle is detected when the reception level of the vehicle reflected wave 2 exceeds the level of the detection threshold 6 by comparing with a threshold (sensing threshold) 6 higher than the reference level 5 by a predetermined value.

At this time, in order to prevent the background reflected wave 3 from being erroneously sensed as a vehicle, the sensing threshold 6 is set to an appropriate value so that the reception level of the background reflected wave 3 does not exceed the sensing threshold 6. Alternatively, the receiving sensitivity is set low. This makes it possible to prevent erroneous sensing due to the background reflected wave 3.

[0007]

However, in the case of a conventional ultrasonic vehicle sensor, if a background reflected wave 3 having a large reception level exists, it is detected in order to prevent the background reflected wave 3 from being erroneously detected as a vehicle. If the threshold 6 is set to a level higher than the reception level of the background reflected wave 3, when the reception level of the vehicle reflected wave 2 is low, the vehicle reflected wave 2 may not exceed the sensing threshold 6, and the vehicle may enter. Nevertheless, the problem of not sensing the vehicle occurs.

When the detection threshold 6 is set to a level at which a small vehicle reflected wave 2 can be detected, the receiving sensitivity must be set low so that the background reflected wave 3 does not exceed the detection threshold 6. Then, the reception level of the background reflected wave 3 decreases and the reception level of the vehicle reflected wave also decreases. As a result, the vehicle is detected even though the vehicle enters, as in the case where the detection threshold 6 is set to a large level. The problem of not doing so.

SUMMARY OF THE INVENTION The present invention solves such a conventional problem. An ultrasonic vehicle capable of performing a stable vehicle detection operation while maintaining sufficient sensitivity even in an environment where a large background reflected wave exists. It is an object to provide a sensor and to provide a vehicle sensing method thereof.

[0010]

Therefore, according to the present invention, at each time after the emission of an ultrasonic wave, the reference level is changed in a direction to cancel the background reflected wave at a time when the reception level of the background reflected wave is higher than the reference level. ing.

As a result, it is possible to suppress the background reflected wave from protruding from the reference level, and to remove the influence of the background reflected wave to detect the vehicle.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to an ultrasonic transmitter / receiver for transmitting / receiving ultrasonic waves and a reflected wave level detecting means for detecting a reflected wave level of ultrasonic waves obtained from the ultrasonic transmitter / receiver. An ultrasonic vehicle sensor comprising:
Background reflected wave storage means for storing a background reflected wave dependent on the installation environment that does not include a vehicle reflected wave component; reference level varying means for varying a reference level of the reflected wave at each time after ultrasonic emission; and Correction value setting means for setting the amount of change at each time after the ultrasonic emission, wherein the correction value setting means sets the amount of change of the reference level so as to lower the level of the background reflected wave at each time after the ultrasonic emission. Is set, and even in an environment where a strong background reflected wave exists, erroneous sensing due to the background reflected wave can be prevented without lowering the reception sensitivity.

According to a second aspect of the present invention, there is provided a background reflected wave maximum value detecting means for detecting the maximum value of the level of the background reflected wave, and the correction value setting means based on the background reflected wave indicating the maximum level. The amount of change in the reference level is set, and erroneous sensing due to fluctuation of the background reflected wave caused by climate change, vibration of a vehicle sensor, or the like can be prevented.

According to a third aspect of the present invention, there is provided a non-variation correction value setting means for setting the fluctuation amount at each time after the ultrasonic emission of the reference level to zero, and a switch for activating the non-variation correction value setting means. In this configuration, the level of the background reflected wave can be confirmed by operating the switch, so that the background reflected wave can be observed, and the efficiency of maintenance work can be improved.

According to a fourth aspect of the present invention, there is provided a vehicle detecting method for an ultrasonic vehicle detector for detecting a vehicle by comparing a reflected wave level of an ultrasonic wave with a detection threshold value, wherein the installation environment does not include a vehicle reflected wave component. The background reflected wave dependent on is measured, the reference level at the time of reflected wave level measurement, so as to lower the level of the background reflected wave at each time after ultrasonic emission, to temporally fluctuate, Even when the background reflected wave level is strong, erroneous sensing due to the background reflected wave can be prevented without lowering the reception sensitivity.

According to a fifth aspect of the present invention, the maximum value of the level of the background reflected wave is measured, and the reference level is temporally changed so as to lower the level of the background reflected wave indicating the maximum level. Therefore, it is possible to prevent erroneous sensing due to fluctuation of the background reflected wave.

According to a sixth aspect of the present invention, the temporal fluctuation of the reference level is set to zero so that the level of the background reflected wave can be confirmed, so that the maintenance work can be made more efficient. .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) As shown in FIG. 1, an ultrasonic vehicle sensor according to a first embodiment controls an ultrasonic transmitter / receiver 11 for transmitting / receiving ultrasonic waves and transmission of ultrasonic waves. Among the signals obtained from the ultrasonic transmitter 12 and the ultrasonic transmitter / receiver 11,
An ultrasonic receiving unit 13 for amplifying a transmission frequency component, an amplifying unit 14 for amplifying a weak signal from the ultrasonic receiving unit 13 to a controllable level, and a reference level for lowering the reference level at the reception time of the background reflected wave A variation unit 20, an addition unit 40 that adds the signal level output from the amplification unit 14 and the reference level output from the reference level variation unit 20, and determines the vehicle sensing and sets the variation amount of the reference level And a time counter (not shown) for measuring the time from the emission of the ultrasonic wave.

The CPU 30 has a configuration including A / D conversion and detects a level of the reflected wave output from the adder 40. The reflected wave level detector 15 compares the level of the reflected wave with the threshold value of the vehicle. A sensing determination unit 16 for determining the presence / absence, a background reflected wave storage unit 17 for storing a reflected wave depending on the installation environment that does not include a vehicle reflected wave component, and a reference level that varies with time according to the background reflected wave level And a D / A converter 19 that converts the correction value into an analog signal and outputs the analog signal to the reference level variation unit 20.

The operation of the CPU 30 of the ultrasonic vehicle sensor will be described with reference to FIGS.

Step 1: When the power is turned on, Step 2: The CPU 30 sets the D / A converter 19 to an initial value correction value for setting the reference level to be uniform at all times after the transmission of the ultrasonic wave. And converts the analog signal into an analog signal, which is provided to the reference level changing unit 20.

Step 3: In this state, the vehicle sensor receives a reflected wave. The received reflected wave signal is shown in FIG.

Step 4: The reflected wave level detecting section 15 detects the level of the reflected wave signal output from the adding section 40 and takes it into the CPU. The level of the reflected wave signal forms a peak at a certain time as shown in FIG.

Step 5: The sensing determination section 16 compares the level detected by the reflected wave level detecting section 15 with a sensing threshold. When the power is turned on, the sensing threshold is set to a high level in advance so that sensing is not performed by the background reflected wave.

Step 6: If the result of the comparison in step 5 indicates that there is no detection, the reflected wave level is stored as a background reflected wave in the background reflected wave storage unit 17, and Step 7: When the peak of the background reflected wave level appears, A correction value for temporally varying the reference level is generated so as to reduce the reference level, and stored in the correction value storage unit. The magnitude of the reduction of the reference level at this time is set according to the magnitude of the stored background reflected wave level.

Step 8: This correction value is converted to a D / A converter 19
And converts the analog signal into an analog signal, and supplies the analog signal to the reference level changing unit 20. The reference level change unit 20 changes the reference level based on the value of the time counter that measures the time from the emission of the ultrasonic wave so that the reference level decreases at the time when the peak of the background reflected wave level appears.

FIG. 3 (c) shows the reference level output from the reference level varying section 20, and a valley is formed when the background reflected wave level (FIG. 3 (b)) becomes a peak. I have.

FIG. 3 again with the reference level changed.
When the reflected wave signal shown in FIG.
Since the state changes to the state shown in FIG. 3C, the level output from the adding unit 40 is such that the level of the background reflected wave is small as shown in FIG.

Thereafter, Step 4 → Step 5 → Step 6 → Step 7 → Step 8 → Step 4 is repeated. If the reception level of the background reflected wave is higher than the reference level, the reference level is corrected and corrected. By continuing the lowering operation, finally, as shown in FIG. 3 (final waveform)
As shown by, a state where the reception level of the background reflected wave does not protrude from the reference level can be created.

When a vehicle enters in such a state, the vehicle reflected wave can be normally detected without causing erroneous detection due to the background reflected wave without lowering the receiving sensitivity or increasing the detection threshold. Can be sensed.

(Second Embodiment) An ultrasonic vehicle sensor according to a second embodiment prevents erroneous sensing due to wobble of a background reflected wave.

As shown in FIG. 4, the vehicle sensor has a maximum background reflection wave storage section 22 for storing the maximum background reflection wave level, and stores the level of the captured background reflection wave and the background reflection wave maximum value. The background reflected wave maximum value comparison unit 21 that compares the level of the background reflected wave stored in the unit 22 and selects the level to be stored in the background reflected wave maximum value storage unit 22, and captures the background reflected wave a certain number of times And a counter 23 for counting the number of comparisons for storing the maximum value among the captured values as a background reflected wave. Other configurations are the same as those of the first embodiment (FIG. 1).

The background reflected wave storage unit 7 of the vehicle sensor stores the background reflected wave of the level stored in the background reflected wave maximum value storage unit 22 and the count value of the counter 23 reaches a certain number. Only what was done is stored. Only this point is different from the first embodiment.

When the power is turned on, the D / A converter 19 converts the initial value correction value, which is set so that the reference level becomes uniform at all times after the transmission of the ultrasonic wave, into an analog signal. To the reference level variation unit 20. When a reflected wave is received in this state, the reflected wave level detection unit 15
The level of the reflected wave signal output from the adding section 40 is detected and taken into the CPU, and the sensing determination section 16 compares the level detected by the reflected wave level detecting section 15 with a sensing threshold.

As a result of the comparison, when it is not detected, the reflected wave is set as the maximum value of the background reflected wave, and the level is stored in the background reflected wave maximum value storage unit 22. At the same time, the counter 23
Is incremented by one. The reference level is not changed, the reflected wave level of the received reflected wave signal is fetched again, the reflected wave level is compared with the sensing threshold value, and if not detected, the background reflected wave maximum value comparing unit 21 is activated. Then, the reflected wave level is compared with the level of the reflected wave stored in the background reflected wave maximum value storage unit 22.

As a result of the comparison, if the level of the captured reflected wave is higher, the level is set as the maximum value of the background reflected wave, and the data in the maximum value of the background reflected wave storage unit 22 is updated. Is smaller, the level of the reflected wave stored in the background reflected wave maximum value storage unit 22 is maintained. The counter 23 increases the counter value by one each time a background reflected wave is taken.

Thereafter, the process of acquiring the reflected wave level of the reflected wave signal, comparing with the sensing threshold, comparing with the maximum value of the background reflected wave, and updating the maximum value of the background reflected wave is repeated, and the counter value of the counter 23 is set in advance. When the value becomes the same as the stored value, the data in the background reflected wave maximum value storage unit 22 is developed in the background reflected wave storage unit 7 and the count value of the counter 23 is reset.

Thereafter, as in the first embodiment,
A correction value of the reference level is generated in accordance with the magnitude of the background reflected wave level, stored in the correction value storage unit 18, and the correction level is given to the reference level change unit 20 to change the reference level.

Thereafter, by the same processing as described above, the maximum value of the background reflected wave when the count value of the counter 23 reaches a certain number is detected, and sequentially developed in the background reflected wave storage unit 7. Thus, by detecting the maximum value of the background reflected wave and changing the reference level, the reflected wave level is changed due to the climatic change of the installation environment such as temperature and wind, or the vibration of the ultrasonic handset. Is unstable, it is possible to prevent erroneous sensing due to fluctuations in the background reflected wave level.

(Third Embodiment) The ultrasonic vehicle sensor according to the third embodiment can check the level of the background reflected wave and check whether the influence of the background reflected wave has been removed. .

As shown in FIG. 5, the vehicle sensor includes a switch 25 for outputting a trigger signal when the background reflected wave level is confirmed, and a non-variation correction value storage for storing a correction value for preventing the reference level from changing at all. And a unit 24. Other configurations are the same as those of the first embodiment (FIG. 1).

FIG. 6A shows a state in which the reference level is changed with respect to the background reflected wave to remove the influence of the background reflected wave.

To check the background reflected wave level, the switch 25 is pressed. With this operation, a trigger signal is output from the switch 25, and the correction value stored in the non-variation correction value storage unit 24 is given to the reference level fluctuation unit 20, and as a result, the reference level is not changed at all. . The reflected wave signal at this time is as shown in FIG. 6B, and the background reflected wave protrudes from the reference level. At this time, the reflected wave level stored in the background reflected wave storage unit 17 is not changed.

In this state, when the switch 25 is operated and the trigger signal is released, the correction value in the correction value storage unit 18 is supplied to the reference level change unit 20 again, and returns to the state of FIG. The effects of background reflected waves are eliminated.

As described above, when the trigger signal is given by the switch 25, the reflected wave level of the background reflected wave can be observed,
It is possible to easily confirm whether or not the influence of the background reflected wave has been actually removed, and the maintenance work can be made more efficient.

This configuration is similar to that of the second embodiment (FIG. 4).
It is also possible to apply to. In that case, the correction value stored in the non-variation correction value storage unit 24 is
Is not changed, the reflected wave level in the background reflected wave maximum value storage unit 22 or the background reflected wave storage unit 17 is not changed.

[0048]

As is apparent from the above description, according to the present invention, erroneous sensing due to background reflected waves can be prevented, and more accurate vehicle sensing information can be obtained. Therefore, the use of the ultrasonic vehicle detector in a tunnel or the like becomes possible.

Further, by detecting the maximum value of the background reflected wave, it is possible to prevent erroneous sensing due to the fluctuation of the background reflected wave which fluctuates variously in the installation environment.

Further, since the fluctuation of the reference level can be canceled during the operation, the efficiency of the maintenance work can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ultrasonic vehicle sensor according to a first embodiment;

FIG. 2 is a processing flow showing an operation of the ultrasonic vehicle sensor according to the first embodiment;

FIG. 3 is a diagram showing a transition of a reflected wave signal in the ultrasonic vehicle sensor according to the first embodiment;

FIG. 4 is a block diagram showing a configuration of an ultrasonic vehicle sensor according to a second embodiment.

FIG. 5 is a block diagram showing a configuration of an ultrasonic vehicle sensor according to a third embodiment;

FIG. 6 is a diagram showing a transition of a reflected wave signal in the ultrasonic vehicle sensor according to the third embodiment;

FIG. 7 is a view for explaining a vehicle sensing method of a conventional ultrasonic vehicle sensor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmitted wave 2 vehicle reflected wave 3 background reflected wave 4 road surface reflected wave 5 reference level 6 sensing threshold 11 ultrasonic transmitter / receiver 12 ultrasonic transmitting unit 13 ultrasonic receiving unit 14 amplifying unit 15 reflected wave level detecting unit 16 sensing determining unit 17 Background reflected wave storage unit 18 Correction value storage unit 19 D / A conversion unit 20 Reference level fluctuation unit 21 Background reflected wave maximum value comparison unit 22 Background background maximum value storage unit 23 Counter 24 Non-variation correction value storage unit 25 Switch 30 CPU 40 Adder

Claims (6)

[Claims] 1. An ultrasonic vehicle sensor comprising: an ultrasonic transmitter / receiver for transmitting / receiving ultrasonic waves; and a reflected wave level detecting means for detecting a reflected wave level of an ultrasonic wave obtained from the ultrasonic transmitter / receiver. Background reflected wave storage means for storing a background reflected wave dependent on the installation environment that does not include a wave component; reference level varying means for varying a reference level of the reflected wave at each time after ultrasonic emission; and Correction value setting means for setting a variation amount at each time after the sound wave is emitted, wherein the correction value setting means changes the reference level so as to lower the level of the background reflected wave at each time after the ultrasonic wave emission. An ultrasonic vehicle detector characterized by setting an amount. 2. The apparatus according to claim 1, further comprising a background reflected wave maximum value detecting unit for detecting a maximum value of the level of the background reflected wave, wherein the correction value setting unit determines the reference level based on the background reflected wave indicating the maximum level. 2. The ultrasonic vehicle sensor according to claim 1, wherein the amount of variation is set. 3. A non-variation correction value setting means for setting a fluctuation amount at each time after the ultrasonic emission of the reference level to zero, and a switch for activating the non-variation correction value setting means, wherein the switch 3. The ultrasonic vehicle sensor according to claim 1, wherein the level of the background reflected wave can be confirmed by operating. 4. A vehicle sensing method for an ultrasonic vehicle detector for detecting a vehicle by comparing a reflected wave level of an ultrasonic wave with a sensing threshold value, wherein a background reflected wave that does not include a vehicle reflected wave component and is dependent on an installation environment is detected. A method for sensing a vehicle, comprising measuring and temporally varying a reference level at the time of measuring a reflected wave level so as to lower the level of the background reflected wave at each time after ultrasonic emission. 5. The method according to claim 1, wherein a maximum value of the level of the background reflected wave is measured, and the reference level is temporally changed so as to lower the level of the background reflected wave indicating the maximum level. Item 5. A vehicle sensing method according to Item 4. 6. The vehicle sensing method according to claim 4, wherein a temporal change in the reference level is set to zero, and the level of the background reflected wave is confirmed.