JPH09113617A - Ultrasound sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasound sensor which does not malfunction even when the multipath reflection of radio waves occurs or noise gets mixed in a detected waveform pattern. SOLUTION: An ultrasonic sensor detects the waveform pattern of the reflected waves of ultrasound waves after transmitting the ultrasound waves and detects the presence/absence of an invader in a surveillance space by comparing the detected waveform pattern with the waveform pattern of the reflected wave when no invader exists in the surveillance space. The sensor transmits the ultrasound waves at prescribed time intervals, is provided with two or more storing means 21 and 22 which respectively store two or more detected waveform patterns and an ANDing means 23 which ANDs the waveform patterns stored in the storing means 21 and 22, and uses the AND of two or more waveform patterns of reflected waves as the waveform pattern of the detected reflected waves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic sensor, and more particularly, to an ultrasonic sensor, which is used in a parking lot or the like, transmits an ultrasonic wave to a monitored space, detects a reflected wave of the ultrasonic wave, and detects the reflected wave. The present invention relates to an improvement of an ultrasonic sensor for detecting presence of a vehicle or the like.

[0002]

2. Description of the Related Art An ultrasonic sensor used in a parking lot or the like transmits an ultrasonic wave of a predetermined frequency into a monitoring space using an ultrasonic vibrator, and a reflected wave from an object in the monitoring space. Is received by the ultrasonic transducer to detect the presence of the object. Here, the monitoring space refers to a space in which, when the transmitted ultrasonic wave is reflected by an intruder, the ultrasonic sensor can receive the reflected wave, and the ultrasonic sensor can detect the intruder. Means space.

FIG. 4 shows an example of the configuration of a conventional ultrasonic sensor. The ultrasonic sensor 1 includes an oscillator 10 and a wave transmission circuit 1
1, an ultrasonic wave transmitter 12, an ultrasonic wave receiver 13, an amplification circuit 14, a detection circuit 15, a current state storage circuit 16, an environment storage circuit 17, a comparison circuit 18, and a detection determination circuit 19
It is composed of The oscillation signal output from the oscillator 10 becomes a tone burst wave in the wave transmission circuit 11,
A pulse train is transmitted from the ultrasonic wave transmitter / receiver 12, reflected by an object in the monitoring space, and received by the ultrasonic wave transmitter / receiver 12. The received signal is amplified by the amplification circuit 13 and detected by the detection circuit 14.

The detected waveform data thus obtained is stored in the current state storage circuit 16 as a digitally converted waveform pattern. On the other hand, by the same method, the pattern of the detected waveform in the state where no intruder exists in the monitoring space is stored in the environment storage circuit 17 in advance. Therefore, the comparison circuit 18 compares the waveform pattern stored in the current state storage circuit 16 with the waveform pattern held in the environment storage circuit 17, and determines the presence or absence of an intruder based on the comparison result. be able to.

That is, if the two waveform patterns are the same, it can be determined that there is no intruder in the monitoring space, and if there is a difference between the waveform patterns, it can be determined that there is an intruder in the monitoring space. The detection determination circuit 19 makes this determination and outputs a detection signal when there is an intruder. The manner in which the waveform pattern of the reflected wave is stored in the current state memory circuit 16 is shown in (a) to (c) of FIG. FIG. 5A shows the received signal input to the detection circuit 15, and the threshold level 15
A signal exceeding 0 includes a transmitted wave 300, a reverberation wave 301 following this, and a reflected wave 310 detected thereafter.

FIG. 5B shows the transmitted wave 300 and the reverberant wave 3.
This is a detection gate signal for giving a timing for detecting only the reflected wave 310 without detecting 01, and is given as a fixed period after a fixed time from the transmission of ultrasonic waves. FIG. 5C shows the waveform data of the reflected wave that is digitally converted and stored in the current storage circuit 16, and indicates the detection gate period, that is, the period 32 in which the detection gate signal is active.
It is divided by a fixed quantization time ts and binarized by setting the period exceeding the threshold level 150 to "1" and the period not exceeding the threshold level 150 to "0". The time tw until the bit data of this waveform pattern changes from "0" to "1" indicates the distance from the ultrasonic sensor to the reflector that has reflected the ultrasonic wave.

By comparing this waveform pattern with a similar waveform pattern stored in the environment storage circuit 17, it is possible to detect the presence or absence of an intruder in the monitoring space. For example, by installing such an ultrasonic sensor 1 on the ceiling surface of an indoor parking lot and monitoring the floor surface, it is possible to recognize whether or not a vehicle is parked in the parking lot.

[0008]

The conventional ultrasonic sensor as described above repeatedly transmits the ultrasonic waves at regular intervals to detect the intruding object as described above. However,
Depending on the installation condition and usage condition of the ultrasonic sensor, the ultrasonic wave transmitted from the ultrasonic sensor is reflected on the floor surface, and the reflected wave is further reflected by the ultrasonic sensor or the ceiling, Multiple reflections that occur multiple times may occur between the two. For example, multiple reflections occur due to the temperature range in which the ultrasonic sensor is used and the distance between the installed ceiling and floor.

In this case, if the ultrasonic wave transmission interval is shorter than the extinction time of multiple reflection, which is the time until the reflected wave due to multiple reflection attenuates and does not exceed the threshold value 150, Since the detected waveform pattern includes the multiple reflection waveform of the ultrasonic wave transmitted last time or before, there is a problem that the intruder cannot be accurately detected.

This state is shown in FIG. Reflected waves 310, 3
Reference numerals 11 and 312 are reflected waves when the first transmitted wave 300 is reflected multiple times and are gradually attenuated.
The reflected wave 312 has an amplitude exceeding the threshold level 150 even during the active period 42 of the detection gate signal for the second transmission 400. For this reason,
As the reflected wave for the transmitted wave 400, the originally reflected wave 410
Not only will the reflected wave 312 of the previous time be detected. Therefore, the time tw indicating the distance to the reflecting object
However, it becomes short as tw '.

If this waveform pattern is stored in the current state memory circuit 16, it does not match the waveform pattern held in the environment memory circuit 17, so that the comparison circuit 18 compares even if there is no intruder. The results do not match,
The detection determination circuit 19 will erroneously determine that an intruder is present. If the waveform pattern stored in the environment storage circuit 17 in advance is detected when multiple reflections occur with the floor surface, the waveform of the original reflected wave from the floor surface. In some cases, the pattern cannot be stored in the environment storage circuit 17, and the intruder cannot be detected accurately.

Furthermore, under the influence of a single noise,
Even when the detected waveform pattern includes a noise wave other than the reflected wave, there is a problem that the intruder cannot be accurately detected in the same manner. This is shown in FIG. The solitary noise wave 33 has a threshold level of 150.
It has an amplitude exceeding .gamma. And is detected during the active period 32 of the detection gate signal. Therefore, the time tw indicating the distance to the reflecting object is shortened to tw ',
Intruders cannot be detected accurately.

The present invention has been made in view of the above circumstances, and provides an ultrasonic sensor which does not malfunction even when multiple reflections of ultrasonic waves occur or noise is mixed in a detected waveform pattern. The purpose is to do.

[0014]

An ultrasonic sensor according to the present invention as set forth in claim 1 detects a waveform pattern of a reflected wave of an ultrasonic wave after the ultrasonic wave is transmitted, and when an intruder is not present in a monitoring space. An ultrasonic sensor for detecting the presence or absence of an intruding object in the monitoring space as compared with the waveform pattern of the reflected wave, in which ultrasonic waves are transmitted at a predetermined transmission interval, and two or more detected ultrasonic waves are detected. Two or more storage means for respectively storing the waveform patterns, and a logical product calculation means for obtaining a logical product of the waveform patterns held in these storage means are provided, and the logical product of the waveform patterns for the two or more reflected waves is The detected reflected wave has a waveform pattern.

An ultrasonic sensor according to a second aspect of the present invention is the ultrasonic sensor according to the first aspect of the present invention, which is provided with a transmission interval control means for controlling an interval at which ultrasonic waves are transmitted. The transmission interval control circuit is configured to make the transmission interval different from the previous transmission interval.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the configuration of an ultrasonic sensor according to the present invention. This ultrasonic sensor 1a is a vehicle sensor that is installed on the ceiling of an indoor parking lot and detects whether or not there is a vehicle in the monitoring space. In addition to the conventional ultrasonic sensor 1 shown in FIG. A circuit 20, a first storage circuit 21 and a second storage circuit 22 as storage means, and an AND operation circuit 23 are provided.

The transmission interval control circuit 20 is a circuit for controlling the generation interval of the tone burst waves generated by the transmission circuit 11 to control the transmission interval of the supersonic waves. The transmission interval is changed so that the interval is different from the previous and current transmission intervals. For example, a pseudo random number is generated, the transmission interval is determined based on this random number, and the transmission timing is output to the transmission circuit 11.

First storage circuit 21 and second storage circuit 22
Is a storage unit that stores the waveform pattern of the reflected wave that has been detected by the detection circuit 15 and that has been digitally converted. The reflected wave pattern for two consecutive transmissions is stored in one of the storage circuits. . That is, the waveform pattern of the reflected wave with respect to a certain transmitted wave is the first memory circuit 2
If it is stored in 1, the waveform pattern of the reflected wave for the next transmission wave is stored in the second storage circuit 22.

The logical product operation circuit 23 is the first storage circuit 2
1 and the second memory circuit 2
2 is an arithmetic circuit for performing a logical product operation with the waveform pattern held in 2, and obtains the logical product of the binary data of these waveform patterns for each corresponding period divided by the quantization time ts. Current waveform storage circuit 16
Alternatively, it is stored in the environment storage circuit 17.

That is, the AND operation circuit 23 outputs data only when the data in the corresponding divided periods of the waveform pattern of the first storage circuit 21 and the waveform pattern of the second storage circuit 22 are both "1". Is set to "1" and in other cases to data "0", a new waveform pattern is generated. The operation of the ultrasonic sensor according to the present invention described in claim 1 will be described below. Figure 2 (a)
7A to 7D are diagrams showing a situation where a sporadic noise wave is mixed in the waveform pattern, which is similar to FIG. 7. (A) in the figure is a received signal input to the detection circuit 15, (b) in the figure is a detection gate signal,
(C) in the figure is waveform data stored in the first memory circuit 21 or the second memory circuit 22, and (d) in the figure
Is a waveform pattern output from the logical product arithmetic circuit.

Since the noise wave 33 is mixed in during the active period 32 of the detection gate signal, the waveform pattern of the reflected wave of the transmission wave 300 is composed of the original reflected wave 310 and the noise wave 33. The pattern will be stored in the first storage circuit 21. However, since this noise wave is a one-shot,
, The waveform pattern of the reflected wave is the reflected wave 410.
And is obtained as a correct waveform pattern and stored in the second memory circuit 22.

Therefore, if the logical product calculating circuit 23 obtains a logical product for these waveform patterns, the influence of the noise wave can be eliminated and a correct waveform pattern can be obtained. The operation of the ultrasonic sensor according to the second aspect of the present invention will be described below. 3 (a) to (d)
[Fig. 6] is a diagram showing a state in which reflection occurs a plurality of times, and is similar to Fig. 6. (A) in the figure is a received signal input to the detection circuit 15, and (b) in the figure
Is a detection gate signal, (c) in the figure is waveform data stored in the first memory circuit 21 or the second memory circuit 22, and (d) in the figure is an AND operation circuit. Is a waveform pattern output by.

Due to the multiple reflections, a reflected wave 512 of the transmitted wave 500 due to multiple reflections is generated during the active period 32 of the detection gate signal for the next transmitted wave 300.
Since the threshold level 150 is exceeded, the first memory circuit 2
The waveform pattern stored in 1 is composed of the original reflected wave 310 and the previous reflected wave 512. In exactly the same manner, the reflected wave 31 by the multiple reflections of the transmitted wave 300
2 exceeds the threshold level 150 during the active period 42 of the detection gate signal for the next transmission wave 400, the waveform pattern stored in the second memory circuit 22 is the same as the original reflected wave 410 and the previous reflection wave 410. And a reflected wave 312.

However, under the control of the transmission interval control circuit 20, the interval ti1 between the transmission wave 500 and the transmission wave 300,
Since the interval ti2 between the transmitted wave 300 and the transmitted wave 400 is different, the position of the multiple reflected wave 512 in the waveform pattern of the first memory circuit 21 and the multiple reflected wave in the waveform pattern of the second memory circuit 22. The position of 312 is different. Therefore, when the logical product of these waveform patterns is obtained in the logical product calculation circuit 23, the reflected waves 512 and 312 due to the multiple reflections are erased, and only the corresponding original reflected waves 310 and 410 remain in the waveform pattern.

Further, even if a noise wave is mixed in the waveform pattern of the reflected wave under the influence of periodic noise, the transmission interval is changed, so that the noise wave is generated in the two waveform patterns. There is no coincidence, and the noise wave is eliminated by the AND operation as in the case of multiple reflections. In this way, the influence of multiple reflections and the influence of periodic noise can be eliminated from the waveform pattern, so that the presence or absence of an object in the surveillance space can be accurately determined.

[0026]

In the ultrasonic sensor according to the present invention as set forth in claim 1, two or more storage means respectively store the waveform patterns of the reflected waves of the ultrasonic waves transmitted at the predetermined transmission intervals, and the logical product is obtained. The calculation means obtains the logical product of the waveform patterns held in these storage means. Therefore, even if a sporadic noise is mixed in the waveform pattern, the effect of this noise can be eliminated in the AND operation circuit, and the effect of noise can be obtained when there is no intruder in the monitoring space. Accordingly, it is possible to prevent the presence or absence of an intruder from being erroneously determined.

Further, when two or more ultrasonic sensors are installed adjacent to each other, the ultrasonic waves emitted from one ultrasonic sensor wrap around and are detected by the other ultrasonic sensor. Even in this case, the influence of this wraparound can be eliminated in the AND operation circuit,
It is possible to prevent the presence or absence of an intruder from being erroneously determined.

In the ultrasonic sensor according to the second aspect of the present invention, the transmission interval control circuit controls the ultrasonic wave transmission interval,
Two or more reflected waves detected when ultrasonic waves are transmitted with different transmission intervals are stored, and the logical product of these is obtained. Therefore, even when multiple reflections occur, the effect of the reflected wave due to multiple reflections can be eliminated in the AND operation circuit, and it is possible to prevent the presence or absence of an intruder from being erroneously determined. can do.

Further, even if periodic noise is mixed in the waveform pattern, the effect of this noise can be eliminated in the AND operation circuit, and if there is no intruder in the monitoring space, It is possible to prevent erroneous determination of the presence or absence of an intruder under the influence of noise.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an ultrasonic sensor according to the present invention.

FIG. 2 is a diagram showing a waveform pattern of a reflected wave when a sporadic noise wave is mixed.

FIG. 3 is a diagram showing a waveform pattern of a reflected wave in the case where a plurality of reflections occur.

FIG. 4 is a diagram showing a configuration of a conventional ultrasonic sensor.

FIG. 5 is a diagram showing a manner in which a waveform pattern is stored in a current state storage circuit in a conventional ultrasonic sensor.

FIG. 6 is a diagram showing a waveform pattern of a reflected wave in the case where a sporadic noise wave is mixed in a conventional ultrasonic sensor.

FIG. 7 is a diagram showing a waveform pattern of a reflected wave when the conventional ultrasonic sensor is reflected multiple times.

[Explanation of symbols]

 1a ... Ultrasonic sensor 20 ... Transmission interval control means 21, 22 ... Storage means 23 ... AND operation means ti1, ti2 ... Transmission interval

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Kawahara 1048 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Works, Ltd.

Claims (2)

[Claims] 1. The presence / absence of an intruder in the surveillance space is detected by detecting the waveform pattern of the reflected wave after the ultrasonic wave is transmitted and comparing with the waveform pattern of the reflected wave when there is no intruder in the surveillance space. In the ultrasonic sensor for detecting the, ultrasonic waves are transmitted at a predetermined transmission interval, and two or more storage means for respectively storing the two or more detected waveform patterns and the storage means are stored in these storage means. And a logical product calculating means for calculating a logical product of the waveform patterns, wherein the logical product of the waveform patterns of two or more reflected waves is used as the waveform pattern of the detected reflected wave. 2. The ultrasonic sensor according to claim 1, further comprising a transmission interval control means for controlling an interval at which ultrasonic waves are transmitted, and the transmission interval control circuit transmits the transmission interval to a previous transmission wave. An ultrasonic sensor characterized by being different from the interval.