JPH0836056A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE:To prevent an error in detection due to the inflow of vapor having a temp. difference and to enhance the reliability of a sensor by observing Doppler signals with a frequency or a phase difference and by integrating a continuing period of time of only signals from a moving body (a human body). CONSTITUTION:A Doppler component detecting part d inputs a received signal outputted from an ultrasonic wave receiver E and amplified in an amplifier circuit D1 to a mixer D2. The received signal is mixed with a reference signal (a sending wave signal) to convert into a pair of Doppler signals having different phases each other. The paired Doppler signals are detected in detectors, D3A, D3B, respectively and are then amplified in amplifiers D4A, DAD to input to a Doppler signal determining circuit F. The circuit F judges the presence of the Doppler signals when the amplitude level of a received wave signal exceeds a threshold value, and inputs it to a frequency observing circuit H, and then to a phase difference observing circuit I. When the frequency and the phase difference are reference values or higher judgement is made to be the Doppler signals from a moving body (a human body). A signal continuing period of time is integrated in an integrating circuit G to output a detecting signal when the Doppler signals exceed the threshold value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the presence of a moving object in a reflective space by transmitting an ultrasonic wave of a predetermined frequency into the monitored space and detecting a reflected wave from an object in the monitored space. To an ultrasonic sensor applied to

[0002]

2. Description of the Related Art As an ultrasonic sensor of this type, there has been proposed an ultrasonic sensor capable of detecting a moving object by utilizing the Doppler effect when an ultrasonic wave is transmitted to the moving object. This conventional one continuously transmits an ultrasonic wave of a predetermined frequency from a wave transmitter, and at the time of receiving a reflected wave at a constant time interval, the received signal of the wave received signal is output from the wave receiver. Based on whether the Doppler component is positive or negative, a predetermined unit value is sequentially added or subtracted to obtain an integrated value, and if the integrated value exceeds a specified threshold, the moving object is monitored at that point. Judge that it exists in the space,
It is configured to output a predetermined moving object detection signal.

In this conventional ultrasonic sensor, a wave transmitter for transmitting an ultrasonic wave into the surveillance space, a wave receiver for receiving a reflected wave from an object existing in the surveillance space, and a transmission signal. Means for mixing a reference signal and a received signal having the same frequency but different phases and converting them into a pair of Doppler signals having different phases, and the movement of the intruding object by the reference signal (transmitted signal) and the received signal And a Doppler signal determination circuit that determines whether the moving direction is positive or negative (approaching or separating), and an integration processing circuit that sequentially adds or subtracts a predetermined unit value based on the positive or negative of the Doppler component to integrate. And means for outputting a moving object detection signal when the integrated value calculated by the integration processing circuit exceeds a predetermined threshold value.

FIG. 7 shows a configuration example of the conventional ultrasonic sensor. In this conventional example, the ultrasonic sensor includes an oscillator a, a wave transmission circuit b, an ultrasonic wave transmitter c, an ultrasonic wave receiver e, an amplification circuit d1, a mixer d2, detection circuits d3a and d3b, and an amplification circuit. a Doppler component detection unit d including d4a and d4b, a Doppler signal determination circuit f, an integration circuit g,
It has.

The oscillating signal oscillated from the oscillator a is sent from the ultrasonic wave transmitter c through the wave sending circuit b. The ultrasonic wave reflected by the moving object is received by the ultrasonic wave receiver e and amplified by the amplifier d1. This signal is mixed with the transmitted signal by the mixer d2, converted into a pair of Doppler signals having different phases, and detected by the detection circuits d3a and d3b.
After being detected by, the signals are amplified by the amplifier circuits d4a and d4b and input to the Doppler signal determination circuit f. When the amplitude level of the received signal exceeds a predetermined threshold value, the Doppler signal determination circuit f determines the presence or absence of the Doppler signal based on the phase shift of the pair of Doppler signals and integrates the duration of the Doppler signal. output to g. The integrating circuit g outputs a detection signal when the integrating time exceeds a predetermined threshold value.

[0006]

However, the above-mentioned conventional devices have the following problems. That is, when an ultrasonic sensor of this kind is installed in a room and used for human body detection, for example, an airflow having a temperature difference from room temperature may flow into the monitoring space from an air conditioner or the like, or may be directly exposed to an ultrasonic wave. In some cases, it may correspond to a sound wave sensor.

At this time, the air flow having a temperature difference forms a fault-reflecting section in the monitoring space, and the movement of the section causes a reflection object such as a human body to move. Occurs. Therefore, when the moving speed of the air flow having a temperature difference is slow (according to the experiment by the inventor of the present application, 60 Hz
Is less than), the signal with Doppler signal is output to the integration circuit and the duration is integrated, and the moving object detection signal is output when the integration time exceeds a predetermined threshold. There has been a problem that a malfunction of outputting is frequently generated.

The present invention has been proposed in view of the above problems, and even if an air flow having a temperature difference occurs in the monitoring space, a malfunction such that a moving object detection signal is output due to the air flow may occur. An object of the present invention is to provide an ultrasonic sensor that does not occur and has excellent reliability in moving object detection.

[0009]

The present invention proposed to achieve the above object has the following structural features. The ultrasonic sensor according to claim 1 receives a wave transmitter that transmits an ultrasonic wave in the monitoring space, and a reflected wave that is transmitted from the wave transmitter and reflected from an object existing in the monitoring space. A wave receiver that oscillates and outputs the received wave signal, and a means that mixes a reference signal and a received wave signal that have the same frequency as the transmitted wave signal but different phases and that converts into a pair of Doppler signals that have different phases , A Doppler signal determination circuit for determining the positive or negative of the Doppler component of the received signal, and an integration processing circuit for sequentially adding or subtracting a predetermined unit value based on the positive or negative of the Doppler component, An ultrasonic sensor comprising: a means for outputting a moving object detection signal when the integrated value calculated by the integration processing circuit exceeds a predetermined constant threshold value, wherein the Doppler signal determination circuit is the Doppler signal determination circuit. A frequency monitoring circuit for monitoring the frequency of the signal, monitoring the Doppler signal in the frequency monitoring circuit, and if the frequency is lower than a predetermined frequency, the integration processing circuit, in the integration of the integrated value It is configured to perform a predetermined unit value integration process in a direction in which a predetermined unit value is reduced or zero, or converges to a midpoint of a threshold value. Here, the middle point of the threshold value means that the integrated value in the integration processing circuit is zero level.

According to another aspect of the ultrasonic sensor of the present invention, the ultrasonic wave transmitting device transmits ultrasonic waves into the monitoring space, and the reflection transmitted from the transmitting device and reflected from an object existing in the monitoring space. A wave receiver that receives a wave and outputs the received signal, and a reference signal and a received signal that have the same frequency as the transmitted signal but different phases from each other are mixed and converted into a pair of Doppler signals that have different phases. Means, a Doppler signal determination circuit for determining whether the Doppler component of the received signal is positive or negative, and an integration processing circuit for sequentially adding or subtracting predetermined unit values based on the positive or negative of the Doppler component to integrate. And an ultrasonic sensor comprising means for outputting a moving object detection signal when the integrated value calculated by this integration processing circuit exceeds a predetermined constant threshold value, wherein the Doppler signal determination circuit is ,Up A phase difference monitoring circuit for monitoring the phase difference of the Doppler signal is provided, the Doppler signal is monitored by the phase difference monitoring circuit, and if the phase difference is a phase difference smaller than a predetermined value, the integration processing circuit, In the integration of the integrated values, a predetermined unit value is configured to be reduced or zero, or a predetermined unit value integration process is performed in a direction of converging to a midpoint of a threshold value.

According to another aspect of the ultrasonic sensor of the present invention, a wave transmitter for transmitting an ultrasonic wave into the monitoring space, and a reflection transmitted from the wave transmitter and reflected from an object existing in the monitoring space. A wave receiver that receives a wave and outputs the received signal, and a reference signal and a received signal that have the same frequency as the transmitted signal but different phases from each other are mixed and converted into a pair of Doppler signals that have different phases. Means, a Doppler signal determination circuit for determining whether the Doppler component of the received signal is positive or negative, and an integration processing circuit for sequentially adding or subtracting predetermined unit values based on the positive or negative of the Doppler component to integrate. And an ultrasonic sensor comprising means for outputting a moving object detection signal when the integrated value calculated by this integration processing circuit exceeds a predetermined constant threshold value, wherein the Doppler signal determination circuit is ,Up A frequency monitor circuit for monitoring the frequency of the Doppler signal and a phase difference monitor circuit for monitoring the phase difference of the Doppler signal are provided, and the frequency monitor circuit and the phase difference monitor circuit monitor the Doppler signal respectively, and the frequency Is a frequency lower than the predetermined frequency,
And when the phase difference is smaller than the predetermined value, the integration processing circuit reduces the predetermined unit value in the integration of the integrated value, reduces it to zero, or converges to the midpoint of the threshold value. It is configured to perform a predetermined unit value integration process.

[0012]

According to the present invention, the following actions are exhibited.
That is, in the ultrasonic sensor described in claim 1,
Due to the occurrence of air flow with a temperature difference in the monitoring space,
Even if the Doppler signal is output to the Doppler signal judgment circuit from the means for mixing the reference signal and the received signal and converting it to the Doppler signal, the frequency monitoring circuit monitors the Doppler signal and its frequency is higher than the predetermined frequency. In the case of a low frequency, the integration processing circuit reduces or zeros a predetermined unit value in the integration of integrated values, or the midpoint of the threshold value (that is,
Since the predetermined unit value integration processing is performed in the direction in which the integrated value converges to zero), the integrated value based on the Doppler component caused by the airflow has a large degree of being returned to the midpoint of the threshold value. The integrated value does not easily exceed the threshold value.

In the ultrasonic sensor according to the second aspect of the present invention, due to the occurrence of an air flow with a temperature difference in the monitoring space, the means for mixing the reference signal and the received wave signal and converting the mixed signal into a Doppler signal is used. Even if the signal is output to the Doppler signal judgment circuit, the phase difference monitoring circuit monitors the Doppler signal, and if the phase difference is smaller than the predetermined value, the integration processing circuit calculates the integrated value. Since the predetermined unit value is reduced or zero, or the predetermined unit value integration process is performed in the direction of converging to the midpoint of the threshold value,
The integrated value based on the Doppler component generated due to the airflow has a large degree of being returned to the midpoint of the threshold value, and the integrated value does not easily exceed the threshold value.

In the ultrasonic sensor according to the third aspect of the present invention, due to the occurrence of an air flow having a temperature difference in the monitoring space, the means for mixing the reference signal and the received signal and converting the mixed signal into a Doppler signal is used. Even if the signal is output to the Doppler signal determination circuit, each of the frequency monitoring circuit and the phase difference monitoring circuit monitors the Doppler signal, and the frequency is lower than the predetermined frequency, and the phase difference is in advance. If the phase difference is smaller than the specified value, the integration processing circuit reduces the predetermined unit value in the integration of the integrated values, reduces it to zero, or performs integration processing for a predetermined unit value in the direction of converging to the midpoint of the threshold value. Since the integrated value based on the Doppler component generated due to the airflow is returned to the midpoint of the threshold value to a greater extent, the integrated value easily exceeds the threshold value. Things like is eliminated.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ultrasonic sensor according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the system configuration of an embodiment of an ultrasonic sensor according to the present invention.

This ultrasonic sensor S is a wave transmitter C for continuously transmitting an ultrasonic wave of a predetermined frequency based on a wave transmission signal oscillated from an oscillator A and supplied via a wave transmission circuit B.
And a wave receiver E for receiving the reflected wave transmitted from the wave transmitter C and reflected from a moving object existing in the monitoring space at a constant time interval. After the wave receiver E,
Doppler component detector D for detecting a Doppler component in the received signal output from receiver E at fixed time intervals, Doppler signal determination circuit F, frequency monitoring circuit H, phase difference monitoring circuit, and integrating circuit G. Etc. are provided.

The Doppler component detector D includes an amplifier circuit D1.
, Mixer D2, detection circuits D3A and D3B, and amplification circuits D4A and D4B. The Doppler component detection unit D is configured to input the received signal output from the wave receiver D1 and amplified by the amplifier circuit D1 to the mixer D2. This received signal is mixed with the reference signal (transmitted signal) by the mixer D2 and converted into a pair of Doppler signals having different phases, and the detection circuit D3
After being detected by A and D3B, amplifier circuits D4A and D4
The signal is amplified by B and input to the Doppler signal determination circuit F.

When the amplitude level of the received signal exceeds a predetermined threshold value, the Doppler signal judgment circuit F judges the presence or absence of the Doppler signal from the phase shift of the pair of Doppler signals, and if there is a Doppler signal, The signal is input to the frequency monitoring circuit H and then to the phase difference monitoring circuit I. Here, the Doppler signal determination circuit F does not output to the frequency monitoring circuit H when the amplitude level of the received signal does not exceed a predetermined threshold value.

FIG. 2 is a waveform diagram of a Doppler signal caused by an air flow having a temperature difference, and FIG. 3 is a waveform diagram of a Doppler signal when a moving object is a human body. According to the experiments by the inventor of the present application, in the circuit of this embodiment using this vector rotation method, the output waveform due to the movement of the human body is a reference signal (transmitted signal) and a pair of Doppler signals converted from the received signal. While the phase difference is 45 degrees or more,
In the output waveform of the Doppler signal due to the influence of the air flow with a temperature difference, the phase difference between the reference signal and the received signal is 0 to 35 degrees,
It is known that the phase difference of the Doppler signal generated by the air flow is relatively small and that the frequency band of the Doppler signal generated by the air flow is 25 to 70 Hz.

That is, there is a difference in frequency and phase difference between the Doppler signal caused by the air flow having a temperature difference and the Doppler signal caused by a moving object such as a human body, and the frequency and the phase difference are monitored and distinguished. By doing so, Doppler signals due to airflow can be eliminated. FIG. 4 is an explanatory diagram showing an example of a case where the integration processing circuit performs integration processing when the moving object is a human body.

As described above, when the amplitude level of the received signal exceeds the predetermined threshold, the Doppler signal determination circuit F
The presence or absence of a Doppler signal is determined from the phase shift of a pair of Doppler signals. If there is a Doppler signal, that signal is input to the frequency monitoring circuit H and then to the phase difference monitoring circuit I. At this time, if the frequency of the Doppler signal is equal to or greater than a predetermined value (for example, 75 Hz) and the phase difference is equal to or greater than a predetermined value (for example, 45 °), the unit value'a 'is set as the duration of the Doppler signal. Output to the integrating circuit for integration.

When the moving object is a human body, the integrated value deviates from the midpoint by the unit value'a 'for each sampling as shown in FIG. 4, and when the integrated time exceeds a predetermined threshold value, the integrating circuit. G outputs a detection signal. FIG. 5 is a waveform diagram of a Doppler signal when a slow-moving human body Doppler signal is included in the Doppler signal caused by the airflow having a temperature difference, and FIG. It is explanatory drawing which shows an example at the time of performing an integration process in an integration circuit, when a Doppler signal of a slow human body enters.

As shown in FIG. 6, when the phase difference between the Doppler signals is less than a predetermined value, the predetermined unit value'c 'is output to the integrating circuit in a direction in which it converges to the midpoint of the threshold value. If the phase difference between the Doppler signals is equal to or greater than a predetermined value and the frequency is less than the predetermined value, a unit value'b 'smaller than the unit value'a' is output to the integrating circuit. Also in this case, when the integration time exceeds the threshold value, the integration circuit G outputs a detection signal.

As shown in FIG. 6, when a Doppler signal is generated by an air flow with a temperature difference, the integrated value approaches the midpoint by the unit value'c 'for each sampling, but in the latter half of the human body moving slowly. Movement signal (frequency is, for example, 75 Hz
(Less than) is added, the integrated value deviates from the midpoint of the threshold by a unit value'b 'smaller than the unit value'a' for each sampling.

The present invention is not limited to the above-described embodiments, and can be modified in design without departing from the gist of the present invention. For example, the unit value'c 'may be added or subtracted as a reduced value or zero.

[0026]

Since the present invention is configured as described above, it has the following effects. According to claim 1, since the Doppler signal is monitored by the frequency, the Doppler signal caused by the air flow having a temperature difference prevents the integrating circuit from integrating the integration time until the integration time exceeds the threshold value. It is possible to prevent a malfunction such that the integrating circuit outputs a detection signal due to the Doppler signal caused by.

According to the second aspect, since the Doppler signal is monitored by the phase difference, it is possible to prevent the integration circuit from integrating the integration time until the integration time exceeds the threshold value due to the Doppler signal caused by the air flow having a temperature difference. Therefore, it is possible to prevent a malfunction in which the integrating circuit similarly outputs a detection signal due to the Doppler signal caused by the air flow.

According to the third aspect, since the Doppler signal is monitored by both the frequency and the phase difference, the integration circuit integrates the integration time until the integration time exceeds the threshold value by the Doppler signal caused by the air flow having a temperature difference. Therefore, it is possible to further prevent the malfunction, such that the integrating circuit outputs the detection signal due to the Doppler signal similarly caused by the air flow.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram of a Doppler signal caused by an air flow having a temperature difference.

FIG. 3 is a waveform diagram of a Doppler signal when a moving object is a human body.

FIG. 4 is an explanatory diagram showing an example of a case where an integration processing circuit performs integration processing when a moving object is a human body.

FIG. 5 is a waveform diagram when a Doppler signal of a slow-moving human body is included in a Doppler signal caused by air flow.

FIG. 6 is an explanatory diagram showing an example of a case where integration processing is performed by an integration circuit when a Doppler signal of a slow moving human body is included in a Doppler signal caused by air flow.

FIG. 7 is a block diagram showing an internal configuration of a conventional ultrasonic sensor.

[Explanation of symbols]

 C wave transmitter E wave receiver F Doppler signal judgment circuit G integration circuit H frequency monitoring circuit I phase difference monitoring circuit S ultrasonic sensor

Claims (3)

[Claims] 1. A transmitter for transmitting ultrasonic waves into a surveillance space, and a reflected wave transmitted from the transmitter and reflected from an object existing in the surveillance space to receive the reflected wave. A wave receiver that outputs a wave reception signal, a means for mixing a reference signal and a wave reception signal that have the same frequency as the wave transmission signal but different phases, and convert into a pair of Doppler signals that have different phases, and said wave reception A Doppler signal determination circuit that determines whether the Doppler component of the signal is positive or negative, an integration processing circuit that sequentially adds or subtracts a predetermined unit value that is predetermined based on the positive or negative of the Doppler component, and this integration processing circuit An ultrasonic sensor comprising: a means for outputting a moving object detection signal when the calculated integrated value exceeds a predetermined threshold value, wherein the Doppler signal determination circuit determines the frequency of the Doppler signal. A frequency monitoring circuit for monitoring is provided, the Doppler signal is monitored by the frequency monitoring circuit, and when the frequency is a frequency lower than a predetermined frequency, the integration processing circuit, a predetermined unit value in the integration of the integrated value Is configured to be reduced or reduced to zero, or to perform integration processing for a predetermined unit value in a direction in which it converges to a midpoint of a threshold value. 2. A wave transmitter for transmitting an ultrasonic wave into the surveillance space, and a reflected wave transmitted from the wave transmitter and reflected from an object existing in the surveillance space, and receiving the reflected wave. A wave receiver that outputs a wave reception signal, a means for mixing a reference signal and a wave reception signal that have the same frequency as the wave transmission signal but different phases, and convert into a pair of Doppler signals that have different phases, and said wave reception A Doppler signal determination circuit that determines whether the Doppler component of the signal is positive or negative, an integration processing circuit that sequentially adds or subtracts a predetermined unit value that is predetermined based on the positive or negative of the Doppler component, and this integration processing circuit An ultrasonic sensor having a means for outputting a moving object detection signal when the calculated integrated value exceeds a predetermined constant threshold, wherein the Doppler signal determination circuit is a phase difference between the Doppler signals. To Equipped with a phase difference monitoring circuit to monitor, the Doppler signal is monitored by the phase difference monitoring circuit, if the phase difference is a phase difference smaller than a predetermined value, the integration processing circuit, in the integration of the integrated value An ultrasonic sensor characterized by being configured to perform integration processing for a predetermined unit value in a direction in which a predetermined unit value is reduced or zero, or converges to a midpoint of a threshold value. 3. A wave transmitter for transmitting an ultrasonic wave into the surveillance space, and a reflected wave transmitted from this wave transmitter and reflected from an object existing in the surveillance space, and receiving the reflected wave. A wave receiver that outputs a wave reception signal, a means for mixing a reference signal and a wave reception signal that have the same frequency as the wave transmission signal but different phases, and convert into a pair of Doppler signals that have different phases, and said wave reception A Doppler signal determination circuit that determines whether the Doppler component of the signal is positive or negative, an integration processing circuit that sequentially adds or subtracts a predetermined unit value that is predetermined based on the positive or negative of the Doppler component, and this integration processing circuit An ultrasonic sensor comprising: a means for outputting a moving object detection signal when the calculated integrated value exceeds a predetermined threshold value, wherein the Doppler signal determination circuit determines the frequency of the Doppler signal. A frequency monitoring circuit for monitoring and a phase difference monitoring circuit for monitoring the phase difference of the Doppler signal are both provided, the Doppler signal is monitored by each of the frequency monitoring circuit and the phase difference monitoring circuit, and the frequency is a predetermined frequency. If the frequency is lower than the frequency, and the phase difference is a phase difference smaller than a predetermined value, the integration processing circuit reduces or reduces a predetermined unit value in integration of the integrated value,
Alternatively, the ultrasonic sensor is configured to perform integration processing for a predetermined unit value in a direction in which it converges to a midpoint of a threshold value.