JPS61262998A - Moving body detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to an apparatus for detecting a moving object such as a vehicle by using the Doppler effect of ultrasonic waves. an ultrasonic transceiver that is connected to the output side of the oscillation circuit for generation and has different transmission and reception frequencies; The present invention relates to a moving object detection device that includes a filter circuit that allows only ultrasonic signals received by a sonic transceiver to pass through, and a Doppler gate circuit that is connected to the output side of the filter circuit.

(Summary of the Invention) In the moving object detection device configured as described above, the present invention provides a moving object detection device configured as described above, from the rising edge of the received ultrasonic signal received by the ultrasonic transceiver, One oscillation output time T, the following predetermined time TZ (T
By using a trigger signal generation circuit that outputs a trigger signal to the Doppler gate circuit over a period of 2≦T1), it is possible to prevent transient waves from being erroneously detected as Doppler waves, and to expand the detection target object and detection range. ,
Also, the degree of freedom in selecting a vibrator can be expanded.

(Prior art and its problems) The characteristics of the vibrator (electroacoustic transducer) of the ultrasonic transceiver
Shown in (A) and (B) of the figure. That is, if the frequency of the maximum value of the transmitted sound pressure is fI, and the frequency of the maximum value of the reception sensitivity is f2, it is a general characteristic of a vibrator that f2>f. Therefore, high sensitivity is achieved by setting the emission frequency fs to fs#f and setting the reception frequency fr to fr#f2. In this case, f r > f s, which corresponds to the Doppler effect when objects approach.

The vibrator has a natural frequency f0 determined by its physical material and dimensions.

By the way, at the start and end points of emitting ultrasonic waves, transient vibrations occur in the vibrator. The frequency ft of this transient vibration is close to the natural frequency f0 of the vibrator (rt
#fo).

To summarize the frequency relationships from below to below, f t”; f, #f2>f, #f s, and
> fs, there is a risk that the transient vibration will be erroneously detected as a Doppler wave.

Note that the energy supplied from the transmitting circuit to the transducer is extremely large, and the emitted ultrasonic waves and transient waves coexist from the start to the end of ultrasonic emission, so the transient waves are ignored for the emitted ultrasonic waves. can do. However, since there are only transient waves after the end of the emitted ultrasound, the transient waves cannot be ignored.

A conventional moving object detection device that takes measures against transient waves is shown in the block diagram of FIG. 5 below.

In FIG. 5, 1 is a transmission/reception switching pulse oscillation circuit, 2 is an oscillation circuit for generating ultrasonic waves, 3 is a transmission gate circuit, 4 is a transmission amplifier circuit, 5 is an ultrasonic transceiver, 6 is a reception amplifier circuit, 7 is an internal oscillation circuit, 8 is a multiplication circuit, 9 is a filter circuit, 1O is a Doppler gate circuit, 11 is a duration verification circuit, 12 is an output circuit composed of a monomultiply with a retrigger function, 1
3 is a gate pulse generation circuit for the Doppler gate circuit 10.

Next, the operation of this conventional moving object detection device will be explained based on the time chart of FIG.

When the transmission/reception switching pulse oscillation circuit 1 and the ultrasonic generation oscillation circuit 2 are driven and the oscillation output is input to the transmission gate circuit 3, the output pulse signal of the transmission/reception switching pulse oscillation circuit 1 activates the transmission gate circuit 3 at a period T. open for a time T1;
The oscillation output from the ultrasonic generation oscillation circuit 2 is output to the transmission amplifier circuit 4.

The oscillation output amplified by the transmitting amplifier circuit 4 is input to the ultrasonic transceiver 5, and an ultrasonic wave SS having a frequency fs is emitted.

The emitted ultrasonic wave S81 hits an object, and the ultrasonic transceiver 5 receives the reflected wave and converts it into an electrical signal.

The wave reception amplification circuit 6 inputs the output signal from the wave transmission amplification circuit 4 and the reception signal from the ultrasonic transceiver 5, amplifies the signal, and outputs the amplified signal to the multiplication circuit 8. As shown in FIG. 6(A), the waveform of the output signal A of the receiving and amplifying circuit 6 includes an ultrasonic transmitting signal SI with a frequency fs and a transient transmitted signal S2 with a frequency ft (>fs). , the emitted ultrasonic wave SS is reflected from a moving object by a Doppler wave signal S, l of a frequency fs', and the reflected wave signal SI'' of a frequency fs reflected by a stationary object is a transient wave S.
There are a Doppler wave signal 82' of frequency ft' in which Sg is reflected by a moving object and a reflected wave signal S2# of frequency ft in which Sg is reflected by a stationary object.

Since reflections from stationary objects do not involve the Doppler effect,
The frequencies of the reflected wave signals SI', 82'' are equal to the frequency fs of the emitted ultrasonic wave SS, and the frequency ft of the transient wave S82, respectively.The frequencies fs', ft' of the Doppler wave signals s, ', s2' are as follows: When a moving object approaches, fs'>fs.

f, t'>ft, but when the moving object moves away, fs'<fs, ft'<fL.

The internal oscillation circuit 7 inputs an oscillation signal having the same frequency fs as the frequency fs of the emitted ultrasonic wave SS to the multiplication circuit 8. The multiplication circuit 8 prevents the Doppler frequency from decreasing by multiplying the oscillation signal from the internal oscillation circuit 7 by the input signal from the wave reception amplifier circuit 6 to perform frequency conversion.

The filter circuit 9 does not pass the frequency component of the frequency fs, but only passes the frequency component higher than the frequency fs.

The waveform of the filtered signal C that has passed through the filter circuit 9 in this manner is as shown in FIG. 6(C). The first waveform in Figure (C) is a direct leakage of the transient liquid transmission signal S2, and the second waveform is a reflected wave signal in which the transient liquid transmission signal S2 is reflected from a stationary object. 82', and the third waveform is due to the emitted ultrasound SS and the Doppler wave signals St', S2' reflected by the transient wave S82 from the approaching moving object.

On the other hand, the data 1-pulse B shown in FIG. 6(B) is input from the gate pulse generator R13 to the Doppler gate circuit 10. This gate pulse B is designed to detect reflected Doppler wave signals over a period of time from the time when a certain period of time t1 has elapsed since the ultrasonic transceiver 5 emits the ultrasonic wave SS to just before the next ultrasonic wave SS is emitted. This is what I did.

The reason why the fixed time t1 is taken is that the transient wave velocity wave signal s
Transient liquid transmission signal S2 due to direct leakage of S2 itself.
This is to prevent the signal from passing through the Doppler gate circuit 10. As a result, the first waveform in Figure (C) disappears.

Therefore, only when the gate pulse B is at H" level, the filtered signal C passes through the Doppler gate circuit 10, and the gate output signal G having the waveform shown in FIG. 6(D) is generated. This gate output signal G is It is input to the duration verification circuit 11.

If the duration of the gate output signal G is longer than the set time, an output signal H is outputted via the output circuit 12 as shown in FIG.

However, the conventional example having such a configuration has the following problems.

In other words, when the effective reflection area of a moving object is small or when the object is moving at high speed, the duration of the Doppler wave becomes too short, and in such cases, the Doppler wave is treated as a transient wave, resulting in false detection. There is a problem that arises.

In particular, in the case of a vibrator with a high sharpness Q, the duration of the transient wave becomes long, and this has a large effect on the size of the detected object and the detection range.

In this way, if the reflected wave of the transient wave SS with a frequency ft higher than the frequency fs of the emitted ultrasonic wave SS, reflected by a stationary object is regarded as a Doppler wave, there is a gate output signal G for this reflected wave, and this Since the gate output signal G exceeds the set time, the output signal H is output as shown in Figure (E) even though the object to be detected is a stationary object, resulting in the problem of false detection as an approaching moving object. there were.

Kuzu explains this issue in detail below.

Conventionally, as a means for preventing erroneous detection of reflected waves of transient waves SS caused by transient vibrations of the vibrator of the ultrasonic transceiver 5,
It takes advantage of the fact that the duration of transient vibrations is shorter than the duration of normal reflected waves from moving objects. That is, if the duration of the Doppler wave is longer than a set time, it is determined that there is a moving object.

In this method, it is necessary to obtain Doppler waves with a sufficiently long time compared to transient vibrations, but as mentioned above, when the effective reflection area of the moving object is small or when the moving object is moving at high speed, , the duration of Dotsupura waves becomes too short,
Doppler waves are regarded as transient waves, resulting in false detection.

In particular, in the case of a vibrator with a high sharpness Q, the duration of the transient wave becomes long, and this has a large effect on the size of the detected object and the detection range. That is, when the sharpness Q is set high, the risk of false detection becomes very high when a small object (for example, a motorcycle) moves at high speed.

Therefore, when a small object is to be detected or when a wide detection range is desired, it is necessary to select a vibrator with small transient waves. However, in the case of a vibrator with small transient waves, the sharpness Q is small and the sensitivity is poor, so there is a trade-off problem that the detection range becomes small.

In addition, since the frequency rt of the transient wave SS is higher than the frequency fs of the emitted ultrasonic wave SSI, the transient wave SS caused by a stationary object
In the case of the reflected wave 2, the received frequency is ft,
Since f t > f s, the object is erroneously detected as an approaching moving object even though it is a stationary object. Furthermore, in the case of the reflected wave of the transient wave SS2 from a moving object moving away at low speed, the received frequency is (
ft-fd)>fs, the object is mistakenly detected as an approaching moving object even though it is moving away.

In order to prevent such false detection, the duration verification circuit 1 was provided as in the configuration described above, but when a small object moves at high speed, the duration of the gate output signal G is The time is shorter than the set time, and the output signal H is not output. In other words, there was a problem in that even though there was a moving object approaching, it could not be detected.

(Purpose of the Invention) The present invention has been made in view of the above circumstances, and is intended to prevent erroneous detection of transient waves as Doppler waves, as well as to expand detection target objects and detection ranges, and The purpose is to expand the degree of freedom in selecting a vibrator.

(Structure and Effects of the Invention) (Structure) In order to achieve the above object, the present invention has the following structure.

That is, the moving object detection device of the present invention includes an oscillation circuit for generating ultrasonic waves, an ultrasonic transceiver connected to the output side of the oscillation circuit for generating ultrasonic waves and having different transmission and reception frequencies.
a filter circuit whose input side is connected to the connection line between the ultrasonic transceiver and the ultrasonic generation oscillation circuit and which illuminates only the ultrasonic signal received by the ultrasonic transceiver; and a filter circuit connected to the output side of this filter circuit. over a predetermined time period T2 (T2≦T1), which is less than one oscillation output time T1 of the ultrasonic generation oscillation circuit, from the rising point of the received ultrasonic signal received by the Doppler gate circuit and the ultrasonic transceiver. and a trigger signal generation circuit that outputs a trigger signal to the Doppler gate circuit.

[Effect]

The effects of this configuration are as follows.

The transmitted ultrasonic signal input from the ultrasonic generation oscillation circuit to the filter circuit is removed by the filter circuit. The received ultrasonic signals inputted from the ultrasonic transceiver to the filter circuit include a mixture of emitted ultrasonic waves and transient vibrations.

The trigger signal generation circuit outputs a trigger signal to the Doppler gate circuit for the predetermined time T2 from the rising edge of the received ultrasound signal. This predetermined time T2 is less than one oscillation output time T1 of the ultrasonic generation oscillation circuit. That is,
The time that the received ultrasound signal that has passed through the filter circuit can pass through the Doppler gate circuit is only the duration of the reflected signal component due to the emitted ultrasound in the received ultrasound signal, and the duration of the reflected signal component due to the transient wave. Time is not included.

Therefore, the received ultrasound signal passing through the Doppler gate circuit is only the reflected signal component of the emitted ultrasound.

This is true regardless of the object to be detected, the detection range, or the sensitivity of the transducer of the ultrasonic transceiver.

〔effect〕

From the above, according to the present invention, detection accuracy can be improved by preventing erroneous detection of transient waves as Doppler waves, and the detection target object and detection range can be expanded, and the transducer The effect is that the degree of freedom in selection can be expanded.

(Description of Examples) Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

〔composition〕

FIG. 1 is a block diagram of a moving direction identification device according to an embodiment of the present invention.

In FIG. 1, the portions other than the portions surrounded by chain lines are the same as those shown in FIG. 5 according to the conventional example, so the same blocks are denoted by the same reference numerals and the explanation thereof will be omitted.

This embodiment differs from the conventional example in the portion surrounded by a chain line, and its configuration is as follows.

14 is a first receiving gate circuit, 15 is a second receiving gate circuit, 16 is a monomulti circuit, and 17 is a Frisopf l:J tube circuit. The first reception gate circuit 14 has its input terminal connected to the output terminal of the transfer amplifier circuit 6, and its output terminal connected to the input terminal of the second reception gate circuit 15. The output end of the second wave reception gate circuit 15 is connected to the input end of the monomulti circuit 16. The output end of the monomulti circuit 16 is connected to the trigger terminal of the tosobra game 1 circuit 10 (3 TE, connected to the 1 input end of the flip-flop circuit 17, and the output of the gate pulse generation circuit 13). The J end is connected to the trigger end r of the first receiving gate circuit 14 and the other input end of the Pfron knob circuit 17. The output terminal of the flip-flop circuit 17 is connected to the second receiving wave 1-1.
It is connected to the I/rega terminal t of the circuit 15.

First receiving circuit 14. 2nd wave receiving game 1・Circuit 1
5. Mono multi-circuit 16 and flip-flop.

Trigger signal generation circuit 1 according to the configuration of the invention.
It makes up the day.

[Operation] Next, the operation of this embodiment will be explained based on the time chart of FIG. 2.

The output waveform from the receiving amplification circuit 6 in Figure (A), the output waveform from the gate pulse generation circuit 13 in Figure (B), and the output waveform from the gate pulse generation circuit 13 in Figure (C).
The output waveforms from the filter circuit 9 of ) are the same as the waveforms of (A) and (Bi(C)) of the conventional example in FIG. 6, respectively.

When the gate pulse B from the gate pulse generation circuit 13 rises to low, the output trigger signal E of the flip-flop circuit 17 rises as shown in FIG.

On the other hand, the waveform of the output signal I from the first receiving gate circuit 14 is as shown in FIG. That is, during the "H" level period of the data 1-pulse B from the gate pulse generation circuit 13, the waveform portion of the output signal A of the wave receiving amplifier circuit 6 that is in the "I" level period of the gate pulse B is The signal begins to pass through the first receiving gate circuit 14 [see figure (D)]. Correspondingly, the output trigger signal F of the mono multi circuit 16 becomes "H" level as shown in the figure (F).The mono multi circuit 16
When the set time 'I'2 has elapsed, the mono multi-circuit 1
The output trigger signal of 6 is inverted to 7° rail.

When this trigger signal F falls from 1'1 to 1,
The output trigger signal E of the one-tub circuit 17 falls. 71
When the output trigger signal E from the 2171371 circuit 17 disappears, the second receiving gate circuit 15 becomes open.

The output trigger signal F from the mono multi-circuit 16 has its rising to low point determined by the input start point of the reflected wave, and its pulse width is determined by the set time T2 of the mono multi-circuit 16. Since T 2 < T + (T + is the emission time of the emitted ultrasonic wave SS), the output trigger signal F is the inverse 11-wave signal 82'' of the transient wave SS.

It is not output during the existence period of Sz', but is output only during the existence period of the reflected wave signal S, ",S,' of the emitted ultrasonic wave SS,.

That is, the reflected wave signal S+N,St of the emitted ultrasonic wave SS,
It is possible to remove the influence of the reflected wave signals s, , s, of the transient wave SS2 after the rising edge of the transient wave SS2.

When the output trigger signal F from this monomulti circuit 16 is input to the Donpla game 1 to circuit 10, the filter circuit 9
The filtered signal C shown in FIG.
And the trigger signal F from the mono multi-circuit 16 is 'H
"Only when Leher's AND condition is satisfied, does the signal pass through the Dosobrage I circuit 10. If there is no reflected wave, there is no 1~Riga signal from the mono multi circuit 16, and there is no output from the Donpla gate circuit 10. In addition, there is no reset of the flip-flop circuit 17, and the seven-segment I state continues until there is a reflected wave.Once the mono multi circuit 16 is triggered, the trigger signal F from the mono multi circuit 16 rises. After the transition, the reflected wave signal S2 of the transient wave SSt
Even if #, Sz' exists, the Frisopfji1 knob circuit 17 is reset, so the second wave reception gate circuit 15
becomes the oven.

Therefore, Zhouj! The monomulti circuit 16 is not triggered twice within the same period of JIT, and there is no influence by the reflected wave signal 32''182' of the transient wave SS2.

From the above, the waveform of the gate output signal G of the Doppler gate circuit 10 is as shown in Figure (G).

That is, the transient wave S8 in the case of a stationary object (moving speed V-0)
The second reflected wave signal 82' is neglected.

Further, the reflected wave signal S1 # of the emitted ultrasonic wave SS has already been neglected at the stage of the filter circuit 9 because its frequency is the same as the frequency fs of the emitted ultrasonic wave SS. Therefore, in the case of a stationary object, the Doppler gate circuit 1
There is no output from 0.

On the other hand, the transient wave SS in the case of a moving object (V>0).

The reflected wave signal 82' is also neglected. Since the frequency fs' of the reflected wave signal SI' of the emitted ultrasonic wave SS is higher than the frequency fs of the emitted ultrasonic wave SS, the reflected wave signal 31' passes through the filter circuit 9 [Fig.
)reference〕. Therefore, this reflected wave signal SI' is not neglected and is outputted from the Doppler gate circuit 10 as shown in Figure (G).

Since the duration of the gate output signal G from the Doppler gate circuit 10 is sufficiently longer than the fixed time set in the duration verification circuit 11, the output circuit 1
Output signal H is outputted via 2.

Note that transient waves SS also occur when an object moves away at low speed.
You can neglect the influence of 2.

As described above, for a moving object, only the reflected wave signals S and l of the emitted ultrasonic waves SS can be detected.

[Another example] The present invention also includes the following configuration as an example.

(I) Emit ultrasonic waves SS as the filter circuit 9 in FIG. 1 to detect when an object is moving away.

A device that allows only frequency components lower than the frequency fs to pass through.

(II) When an object approaches and moves away □
As shown in FIG. 3, in order to distinguish between the two and detect them, in addition to a filter circuit 9 that passes only frequency components higher than the frequency fs of the emitted ultrasonic wave SS, A filter circuit 9' that passes only low frequency components is added to the filter circuit 9', and a Doppler gate circuit 10' and a sustain and output circuit 12' are added to the filter circuit 9'.

Alternatively, in order to detect the presence or absence of movement of an object without distinguishing between approach and separation (movement direction), only the frequency components lower than the frequency fs of the emitted ultrasonic waves SS are passed through the filter circuit 9 in FIG. A parallel connection of filter circuits that

[Brief explanation of the drawing]

1 and 2 relate to an embodiment of the present invention, in which FIG. 1 is a block diagram of a moving object detection device, FIG. 2 is a time chart, FIG. 3 is a block diagram of another embodiment, and FIG. (A),
(B) is a characteristic diagram of the transducer of the ultrasonic transceiver, FIGS. 5 and 6 are related to the conventional example, FIG. 5 is a block diagram, and FIG.
The figure is a time chart. 2... Oscillation circuit for ultrasonic generation 5... Ultrasonic transceiver 9, 9'... Filter circuit 10, 10'... Doppler gate circuit 18... Trigger signal generation circuit

Claims (1)

[Claims] (1) an oscillation circuit for generating ultrasonic waves; an ultrasonic transceiver connected to the output side of the oscillation circuit for generating ultrasonic waves and having different transmission and reception frequencies; a filter circuit connected to a connection line with an oscillation circuit for generating ultrasonic waves and passing only the ultrasonic signal received by the ultrasonic transceiver; a Doppler gate circuit connected to the output side of this filter circuit; A predetermined time T_2 (T_2≦T_
1) A moving object detection device comprising: a trigger signal generation circuit that outputs a trigger signal to the Doppler gate circuit;