JPH05273344A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a malfunction when the threshold of detecting signals varies due to disturbance by setting the threshold to be used when an intruding object is stored from the threshold of detecting signals at the time of storing the surroundings at a higher level. CONSTITUTION:Before and after the movement of an object is detected by a movement detecting system, reflection patterns from the object in an existence detecting system are stored in storage circuit 17 and 18 and compared 19 with each other and, when the patterns do not coincide with each other, it is detected 12 that an intruding object exists. At the time of storing the reflection patterns in circuits 17 and 18, the threshold of detecting signals used when the intruding object (human body) is stored 18 is set higher than the threshold of detecting signals used when the surroundings (stationary object) are stored 17 by means of threshold deciding circuits 15 and 16. Consequently, even when the signal level of reflected waves from the surroundings becomes higher due to such disturbance as a change in ambient temperature, etc., the detecting signals stored in the circuit 17 do not change. Therefore, when no intruding object (human body) exists, no change is discriminated in the detecting signals and no malfunction is induced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic wave which emits ultrasonic waves in a surveillance space and detects a reflected wave from an object in the surveillance space to detect the movement or presence of the object in the surveillance space. It relates to a sensor.

[0002]

2. Description of the Related Art An ultrasonic sensor of this type uses an ultrasonic vibrator to send ultrasonic waves of a predetermined frequency into a monitoring space,
The ultrasonic wave transducer receives the reflected wave from the object to detect the movement or existence of the object. Here, in order to detect the movement of the object, the movement of the intruding object is detected based on the Doppler signal included in the reflected wave, and in order to detect the presence of the object, an ultrasonic pulse is transmitted from the transmitter. The presence of an object in the surveillance space is detected by transmitting the wave and receiving the reflected wave from the object by the wave receiver. By switching between these detection methods alternately, before and after the movement detection method detects the movement of the object, the reflection patterns from the object by the presence detection method are stored in time series, and both reflection patterns are compared. The presence or absence of an object in the surveillance space is determined.

FIG. 5 shows an example of the structure. In this conventional example (Japanese Patent Application No. 2-198174), the oscillation signal oscillated from the oscillator 1 is transmitted from the ultrasonic wave transmitter 3 through the wave transmission circuit 2. The ultrasonic wave reflected by the moving object is received by the ultrasonic wave receiver 4, and the received wave signal is amplified by the amplifier circuit 6 through the transmission wave switching circuit 5. This signal is mixed with the transmitted signal by the mixer 7, and the Doppler signal included in the reflected wave is detected by the detection circuit 8 and then amplified by the amplification circuit 9 and input to the detection determination circuit 12. The detection determination circuit 12 outputs a detection signal when detecting a Doppler signal.

Next, the timer circuit 10 switches to the presence detection method described below at every predetermined time. When the operation time of the movement detection method reaches a predetermined time, the timer circuit 10 sends a signal to the transmission method determination circuit 13 to change to the presence detection method. The wave transmission circuit 2 receives the signal from the wave transmission method determination circuit 13, and sends the signal oscillated from the oscillator 1 to the ultrasonic wave transmitter 3 as a tone burst wave of a pulse train suitable for the presence detection method. The wave transmission method determination circuit 13 sends a signal indicating that the wave transmission method has been switched to the wave transmission type switching circuit 5. The tone burst wave created by the wave transmission circuit 2 is transmitted as a pulse train from the ultrasonic wave transmitter 3, reflected by an object in the monitoring space, and received by the ultrasonic wave receiver 4. The received signal is amplified by the amplifier circuit 11 through the transmission-wave switching circuit 5, and the detection circuit 14
Detected by. The reflection pattern of the detected waveform obtained at this time is stored in the storage circuit 17 or 18 in time series. Then, the comparison circuits 19 compare the reflection patterns stored in the storage circuits 17 and 18 in time series. The presence / absence detection signal is output by the detection determination circuit 12 depending on whether the comparison results match or not.

[0005]

In the conventional example described above, when the presence detection method is switched to, the signal level detected by the detection circuit 14 is discriminated by a predetermined threshold value, and the predetermined threshold value is determined. If it is above, the reflected wave exists, and if it is less than the predetermined threshold value, it is determined that the reflected wave does not exist, and the determination result is stored in the storage circuits 17 and 18 as a time series. The reflection patterns stored in the storage circuits 17 and 18 are obtained by determining the detection signal level of the detection circuit 14 with the same threshold value. Here, if a signal such as a reflected wave of a stationary object slightly below the threshold exists during the storage operation of the memory circuit 17, the signal such as the reflected wave is not stored in the memory circuit 17. However, due to the influence of disturbance such as temperature change thereafter, the detection signal level of the detection circuit 14 may exceed the threshold value and be stored as a reflected wave during the storage operation of the storage circuit 18, and this signal is stored in the human body. However, there is a problem that a malfunction occurs. However, if the threshold value is unnecessarily lowered to solve this problem, the S / N ratio decreases,
Another problem arises in that malfunctions easily occur due to noise or the like.

The present invention has been made in view of the above points, and it is an object of the present invention to set a threshold value used in the presence detection method in an ultrasonic sensor that uses both the movement detection method and the presence detection method. The purpose of this is to prevent malfunction even when it fluctuates due to the influence of disturbance such as temperature change.

[0007]

According to the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, an ultrasonic wave is driven in a monitoring space by being driven by a transmission signal output from an oscillator 1. And a receiver 4 for receiving a reflected wave from an object existing in the monitoring space, and a frequency generated in the received signal by the Doppler effect when the object moves. By the first detection method of detecting the shift component and detecting the movement of the intruding object, the ultrasonic wave is transmitted from the wave transmitter 3 and the reflected wave from the object is received by the wave receiver 4. A means for alternately switching between a second detection method for detecting the presence of an object in the monitoring space and the second detection method is provided,
A first memory circuit 17 that stores the detection signal of the second detection method before the detection signal of the second detection method is obtained in time series;
A second storage circuit 18 that stores the detection signal of the second detection method after the detection signal of the first detection method is obtained in time series.
And a comparison circuit 19 for comparing the storage contents of the first and second storage circuits 17 and 18, and a detection determination circuit 12 for determining that an intruding object is present when the comparison results of the comparison circuit 19 do not match. In the ultrasonic sensor, a first threshold value determining circuit 15 that sets a threshold value of a signal when the detection signal is stored in the first storage circuit 17, and a detection signal is stored in the second storage circuit 18. The second threshold value determining circuit 16 for setting the threshold value of the signal at the time is provided, and the second threshold value is set higher than the first threshold value.

[0008]

In the ultrasonic sensor of the present invention, the movement detection method utilizing the Doppler effect and the presence detection method utilizing the presence / absence detection of the reflection of the ultrasonic pulse are alternately switched, and the movement detection method detects the movement of the object. Before and after the detection, the reflection patterns from the object by the presence detection method are stored and compared, and when the reflection patterns do not match, it is detected that the intruding object exists. When storing the reflection pattern, the intruding object (human body) is more than the threshold value of the detection signal when storing the surrounding environment (stationary object).
Since the threshold value of the detection signal for storing is set high, when the reflection pattern after movement detection does not match the reflection pattern before movement detection, the human body has entered and is present in the surveillance space. It can be accurately determined that there is.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. The oscillation signal oscillated from the oscillator 1 is transmitted from the ultrasonic wave transmitter 3 through the wave transmission circuit 2. The ultrasonic wave reflected by the moving object is received by the ultrasonic wave receiver 4, and the received signal is amplified by the amplifier circuit 6 via the switching circuit 5 for each transmission. This signal is mixed with the transmitted signal by the mixer 7, and the Doppler signal included in the reflected wave is detected by the detection circuit 8 and then amplified by the amplification circuit 9 and input to the detection determination circuit 12. Detection judgment circuit 12
Outputs a detection signal when a Doppler signal is detected.

Next, the timer circuit 10 switches to the presence detection method shown below at predetermined time intervals. When the operation time of the movement detection method reaches a predetermined time, the timer circuit 10 sends a signal to the transmission method determination circuit 13 to change to the presence detection method. The wave transmission circuit 2 receives the signal from the wave transmission method determination circuit 13, and sends the signal oscillated from the oscillator 1 to the ultrasonic wave transmitter 3 as a tone burst wave of a pulse train suitable for the presence detection method. The wave transmission method determination circuit 13 sends a signal indicating that the wave transmission method has been switched to the wave transmission type switching circuit 5. The tone burst wave created by the wave transmission circuit 2 is transmitted as a pulse train from the ultrasonic wave transmitter 3, reflected by an object in the monitoring space, and received by the ultrasonic wave receiver 4. The received signal is amplified by the amplifier circuit 11 after passing through the transmission-based switching circuit 5, and the detection circuit 1
It is detected by 4. Here, the first memory circuit 17 is
The detection signal of the presence detection method before the detection signal of the movement detection method is stored in time series, and the second storage circuit 18 detects the presence signal after the detection signal of the movement detection method is obtained. The system detection signals are stored in time series. Then, the comparison circuit 19 compares the stored contents of the first and second storage circuits 17 and 18, and when the comparison result of the comparison circuit 19 does not match, the detection determination circuit 12 determines that an intruding object exists. To do. In such an ultrasonic sensor, a first threshold value determination circuit 15 for determining a threshold value of a signal when a detection signal is stored in the first storage circuit 17 and a second storage circuit 18 are provided. A second threshold value determining circuit 16 for determining a threshold value when storing the detection signal is provided, and the threshold value is determined more than the first threshold value determined by the threshold value determining circuit 15. Circuit 16
The second threshold value determined by is set high. Then, the reflection patterns stored in the storage circuits 17 and 18 are time-sequentially compared by the comparison circuit 19, and if the comparison results do not match, a detection output is generated.

FIG. 2 is an operation explanatory diagram showing a first operation example of this embodiment. The waveform shown in the upper part of the figure is the input waveform of the detection circuit 14, the horizontal axis shows the time after transmission, and the vertical axis shows the voltage value. R is a reverberant sound, and a, b, and c are reflected waves. Further, h17 is a threshold value when stored in the storage circuit 17, and h18 is a threshold value when stored in the storage circuit 18. In the conventional example, the threshold value of this type of ultrasonic sensor is set to the same level as the higher threshold value h18. For example, in a room as shown in FIG. 4, when a sensor S exists on the ceiling, a stationary object B exists on the floor C, and an object A larger than the stationary object B exists,
The reflected wave a from the object A is received earliest, the reflected wave b from the stationary object B is received next, and finally the reflected wave c from the floor C is received. Here, when the stationary object B is unlikely to reflect ultrasonic waves, the reflected wave b has a smaller amplitude than the other reflected waves a and c. In such a case, the level of the reflected wave b may be lower than the higher threshold value h18, as shown in FIG.
The reflected wave b may not be detected. However, the level of the reflected wave b may become higher than the higher threshold value h18 as shown in FIG. 3 due to a change in the ambient temperature. In this case, in the conventional example, the reflected wave b is detected. Will be done. Therefore, when the state shown in FIG. 2 is changed to the state shown in FIG. 3, in the conventional example, it may be recognized that the detection signal has changed although there is no intruding object (person). On the other hand, in the present proposal, the threshold value h17 for detecting the surrounding environment is set lower than the threshold value h18 for detecting the intruding object, so that it may be affected by disturbance such as ambient temperature change. Even if the signal level of the reflected wave b from the surrounding environment becomes high, the detection signal stored in the storage circuit 17 does not change as shown in FIGS. Therefore, it is impossible for the change in the detection signal to be determined even if there is no intruding object (person), and it is unlikely that a malfunction as in the conventional example is induced.

[0012]

According to the present invention, the movement detection method utilizing the Doppler effect and the presence detection method utilizing the presence / absence detection of ultrasonic pulse reflection are alternately switched,
An ultrasonic sensor that detects the presence of an intruding object by storing and comparing the reflection patterns from the object using the presence detection method before and after the movement of the object is detected by the movement detection method. Since the threshold for storing intruding objects is set higher than the signal threshold, the human body enters the surveillance space when the reflection pattern after movement detection does not match the reflection pattern before movement detection. In addition, it is possible to accurately determine that there is and there is an effect that malfunction does not occur due to the influence of disturbance such as temperature change.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is an operation explanatory view showing a first operation of the present invention and a conventional example.

FIG. 3 is an operation explanatory view showing a second operation of the present invention and the conventional example.

FIG. 4 is a front view of the room showing the usage state of the embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1 Oscillator 2 Wave Sending Circuit 3 Ultrasonic Wave Transmitter 4 Ultrasonic Wave Receiving Device 5 Wave Sending Switching Circuit 6 Amplifying Circuit 7 Mixer 8 Detection Circuit 9 Amplifying Circuit 10 Timer Circuit 11 Amplifying Circuit 12 Detection Judgment Circuit 13 Sending Method Determination Circuit 14 Detection circuit 15 Threshold value determination circuit 16 Threshold value determination circuit 17 Storage circuit 18 Storage circuit 19 Comparison circuit

Claims (1)

[Claims] 1. A wave transmitter that is driven by a signal output from an oscillator to transmit an ultrasonic wave into a surveillance space, and a wave receiver that receives a reflected wave from an object existing in the surveillance space. A first detection method for detecting movement of an intruding object by detecting a frequency shift component generated in a received signal by the Doppler effect when the object moves, and transmitting an ultrasonic pulse from a wave transmitter. Means for alternately switching between the second detection method for detecting the presence of the object in the surveillance space by receiving the reflected wave from the object by the wave receiver and the detection method for the first detection method A first memory circuit that stores the detection signal of the second detection method before the signal is obtained in time series, and the detection signal of the second detection method after the detection signal of the first detection method is obtained Second memory circuit for storing the time series, and first and second memory circuits In an ultrasonic sensor including a comparison circuit that compares the stored contents of the circuits and a detection determination circuit that determines that an intruding object is present when the comparison results of the comparison circuits do not match, the detection signal is stored in the first storage circuit. And a second threshold value determining circuit for setting a threshold value of the signal when storing the detection signal in the second memory circuit. Equipped with
An ultrasonic sensor characterized in that the second threshold is set higher than the first threshold.