JPH06222138A - Ultrasonic sensor - Google Patents

Abstract

PURPOSE:To prevent or restrain the timing of detection of a moving object from delaying by increasing, before the moving object is detected, the duration of a first detection mode in which the moving object is detected using the Doppler effect. CONSTITUTION:A first and second detection modes are switched from one to the other according to a switching signal from a timer circuit 10, the time set for the first detection mode being relatively long before a moving object enters a supervisory space. After the moving object is detected in the first detection mode and a signal that indicates detection of the moving object is outputted from a detection judging circuit 12, a switching control circuit 19 controls the output timing of the switching signal outputted from the circuit 10 so as to make greater the ratio of the time set for the second detection mode to that for the first detection mode than before the moving object is detected. After detection of the moving object, the time set for the first detection mode is shortened relative to that for the second detection mode.

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 surveillance space by transmitting ultrasonic waves into a desired surveillance space and detecting reflected waves from an object in the surveillance space. The present invention relates to an ultrasonic sensor applied to.

[0002]

2. Description of the Related Art As an ultrasonic sensor of this type, an ultrasonic wave of a predetermined frequency is transmitted from a wave transmitter into a monitoring space, and a reflected wave from an object is received by a wave receiver to monitor the ultrasonic wave. It has been proposed to enable detection of the presence of a moving object in space. Such an ultrasonic sensor has two different detection modes, that is, a first detection mode in which a moving object is detected based on a Doppler signal component included in a received signal, and a pulse train from a wave transmitter. The second detection mode for determining the presence or absence of an object in the monitoring space based on the received signal output from the receiver by transmitting the ultrasonic wave is alternately set at fixed time intervals by the timer setting. It is configured to switch.

As described above, if the two detection modes are switched at fixed time intervals, the moving object can be detected by utilizing the Doppler effect in the first detection mode, and the moving object can be detected in the monitoring space. The presence of the object can be continuously detected in the second detection mode even if the detection is stopped in the inside and the detection using the Doppler effect becomes difficult. In the first detection mode only, when a moving object stops in the monitoring space, it becomes difficult to detect the object, and the output of the moving object detection signal is unreasonably stopped even though the moving object exists in the monitoring space. However, by alternately switching between the first detection mode and the second detection mode, there is an advantage that such a problem can be appropriately eliminated.

[0004]

However, in the above-mentioned prior art, as shown in FIG. 4A, the two detection modes of the first detection mode and the second detection mode are set by the timer setting, and The intervals of T1 and T2 are regularly and alternately switched, and the ratio of the set time of each detection mode is
Since it is always constant regardless of the time before and after the detection of a moving object, it has the following practical problems. That is, in the ultrasonic sensor of the type in which the first detection mode and the second detection mode are alternately switched, the detection of the moving object is basically performed in the first detection mode until the end. The second detection mode is an auxiliary detection mode for preventing the output of the moving object detection signal from turning off when the moving object stops, and the output of the moving object detection signal is the first detection mode. It is configured to start in mode.

Therefore, as shown by the arrow E in FIG. 4A, when the ultrasonic sensor is set to the second detection mode, if the human body just enters the monitoring space,
At that time, the moving object detection signal is not output. The time when the moving object detection signal is output is the time of the subsequent first detection mode. As a result, conventionally, there has been a problem that the detection timing of a moving object is delayed and the responsiveness deteriorates.

The present invention has been proposed in view of the above points, and a second detection mode for assisting the first detection mode for detecting a moving object by utilizing the Doppler effect is set. Avoiding the delay in the detection timing of moving objects, which is sometimes caused by moving objects entering the surveillance space,
It is an object of the present invention to provide an ultrasonic sensor capable of preventing or suppressing a delay in the detection timing of a moving object.

[0007]

The ultrasonic sensor according to the present invention, which is proposed to achieve the above object, has the above-mentioned first detection mode and second detection mode. The ultrasonic sensor is configured to be switched alternately at a predetermined time interval and output of a moving object detection signal is started in a first detection mode, wherein the ultrasonic sensor is set to a first time with respect to a set time in the second detection mode. The setting time ratio of the detection mode 1 is set to be larger when the moving object detection signal is not output than when the moving object detection signal is output.

As a specific aspect of the above-mentioned claim 1, as described in claim 2, the set time of the second detection mode is set to a fixed time, and the set time of the first detection mode is It can be configured such that it takes a longer time when the moving object detection signal is not output than when the moving object detection signal is output. As another aspect, as set forth in claim 3, the set time of the first detection mode is set to a fixed time, and the moving object detection signal is output during the set time of the second detection mode. It can be configured such that the time when the moving object detection signal is not output is shorter than the time when the moving object detection signal is output.

[0009]

According to the ultrasonic sensor of the present invention having the above-mentioned structure, the ultrasonic sensor according to the present invention can detect the moving object that has entered the surveillance space and output the moving object detection signal. Since the ratio of the set time of the first detection mode to the set time of the second detection mode is large, it is possible to reduce the probability that a moving object will enter the surveillance space when the second detection mode is set. it can. Therefore, it is possible to reduce the rate of occurrence of a delay in the detection timing due to the moving object entering the monitoring space in the second detection mode.

On the other hand, after the moving object is detected and the moving object detection signal is output, the ratio of the setting time of the first detection mode to the setting time of the second detection mode is the moving object detection signal. Is smaller than before output. That is, the ratio of the set time in the second detection mode becomes large.
Therefore, even if the moving object stops in the monitoring space and its presence cannot be properly detected in the first detection mode, its presence can be properly detected in the second detection mode with a relatively large proportion of time. Therefore, it is possible to appropriately prevent the output of the moving object detection signal from being unequally stopped despite the existence of the moving object.

Also in the ultrasonic sensor according to the present invention as set forth in claim 2 or claim 3, the ratio of the set time between the first detection mode and the second detection mode is changed as in the case of the above-mentioned claim 1. Since the state before and after the output of the moving object detection signal by the detection of the object is different, the same operation as that of the above-described claim 1 can be obtained.

[0012]

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 an example of the hardware configuration of the ultrasonic sensor S according to the present invention. The ultrasonic sensor S includes a wave transmitter 3 that transmits an ultrasonic wave having a predetermined frequency based on an oscillation signal that is oscillated from an oscillator 1 and supplied through a wave transmission circuit 2. It is composed of a wave receiver 4 that receives a reflected wave that is waved and reflected from a moving object existing in the monitoring space, and each circuit described below.

Here, a wave transmission system determination circuit 13 is connected to the wave transmission circuit 2 on the wave transmitter 3 side, and this wave transmission system determination circuit 13 is output from a timer circuit 10 described later. The first detection mode and the second detection mode are substantially switched and controlled based on the signal. In the second detection mode, the transmission circuit 2 is controlled to generate a tone burst wave, and the transmission is performed. The tone burst wave is transmitted from the device 3 as a pulse train. In addition, the transmission method determination circuit 13 is also configured to output a switching signal to the switching circuit 5 for each transmission connected to the wave receiver 4 based on the output signal from the timer circuit 10.

On the side of the wave receiver 4, various processing circuits are connected to the subsequent stage of the switching circuit 5 for each wave transmission. These circuits are a circuit for processing the reception signal in the first detection mode and a second circuit. The circuit for processing the received signal in the detection mode can be roughly classified. On the other hand, as a circuit for processing the received signal in the first detection mode, an amplifier circuit 6 for amplifying the received signal output from the wave receiver 4, a mixer 7, a detection circuit 8, an amplifier circuit 9, a moving time integration A circuit 16 and a detection judgment circuit 12 are provided. Of these, the mixer 7
The received wave signal output from the wave receiver 4 and amplified is mixed with the transmitted wave signal output from the wave transmission circuit 2, and the detection circuit 8 detects the Doppler signal included in the received wave signal. It is for detection. This Doppler signal is the frequency shift of the reflected wave caused by the Doppler effect accompanying the movement of the object that reflects the ultrasonic waves, and if Doppler components with a phase difference of π / 2 are detected and the vector rotation processing is performed, Positive Doppler component
It is possible to make a negative distinction. Moving time integration circuit 16
Is to perform integration processing of a predetermined unit value (for example, "1") at fixed time intervals depending on whether the Doppler component is positive or negative. Basically, if the Doppler component is positive, the unit value "1" is added, and if the Doppler component is negative, the unit value "1" is subtracted and the integrated value is calculated. Detection judgment circuit 1
2 indicates that the moving object exists in the monitoring space when the integrated value by the moving time integration circuit 16 exceeds a preset threshold TH for moving object determination, and outputs a moving object detection signal. To do.

On the other hand, as the circuit for processing the received signal in the second detection mode in which the ultrasonic wave of the pulse train is transmitted from the wave transmitter 3, the amplifier circuit 11, the detection circuit 14, the first memory circuit 17, and the first memory circuit 17 are provided. Two storage circuits 18, a comparison circuit 15, and the like are provided. That is, the received signal output from the wave receiver 4 is detected by the detection circuit 14 after being amplified by the amplification circuit 11, and the pattern data (corresponding to distance measurement data) of the detected signal is It is configured to be stored in the first storage circuit 17 or the second storage circuit 18 in time series. Specifically, the first storage circuit 17 stores the received signal data before the moving object is detected in the first detection mode, that is, the initial value when the moving object does not enter the monitoring space. The data is stored. On the other hand, the data of the latest received signal is stored in the second storage circuit 18, and the data stored in these two storage circuits 17 and 18 are compared by the comparison circuit 15. .

The detection / judgment circuit 12 is the same as the comparison circuit 15
When the two data do not match as a result of the comparison of the two data, it is determined that an object exists in the monitoring space, and if the moving object detection signal has already been output at that time, the signal output is maintained. The output of the moving object detection signal from the detection determination circuit 12 is started in the first detection mode until the end. Unless the moving object is detected in the first detection mode, the moving object detection signal is temporarily output. Even if the two data stored in the first and second storage circuits 17 and 18 do not match, the moving object detection signal is not immediately output due to this.

The timer circuit 10 is configured to output a predetermined switching signal to the transmission method decision circuit 13 at a preset constant time interval, whereby the ultrasonic sensor S is activated.
Although the operation mode of 1 is alternately switched to the first detection mode and the second detection mode, the output of the switching signal from the timer circuit 10 is configured to be controlled by the switching control circuit 19. The switching control circuit 19 changes the set time of the first detection mode depending on whether or not the moving object detection signal is output from the detection determination circuit 12, and is set when the moving object detection signal is not output. The time Ta1 is the set time Tb1 when the output is performed.
It is configured to control the timer circuit 10 to be longer than that. The set time of the other second detection mode is set to a fixed fixed time Tb regardless of whether or not the moving object detection signal is output.

Next, the operation of the ultrasonic sensor S having the above structure will be described. First, in the ultrasonic sensor S, the first detection mode and the second detection mode are alternately switched based on the switching signal output from the timer circuit 10, but before the moving object enters the monitoring space. See Figure 2
As shown by the arrow A in (a), the set time of the first detection mode is set to a relatively long time Ta1. That is, the ratio of the set time Ta1 of the first detection mode to the set time Tb of the second detection mode becomes considerably large. Under such conditions, the probability that a moving object will enter the surveillance space increases when the first detection mode is set. In the second detection mode, the tone burst wave is transmitted as a pulse train from the wave transmitter 3, the pattern data of the wave reception signal output from the wave receiver 4 is written to the storage circuit 17 or 18, and the update processing is performed. However, even if a moving object enters the monitoring space in the second detection mode, the moving object detection signal is not immediately output. Since the first detection mode is the first detection of the intrusion of the moving object into the surveillance space, if the probability of the moving object intruding in this first detection mode increases, the detection time of the moving object increases accordingly. It also makes it possible to reduce the chance of delay.

Next, after the moving object is detected in the first detection mode and the moving object detection signal is output from the detection judgment circuit 12 as shown by an arrow C in FIG. 2B, the switching control circuit is provided. By controlling the output timing of the switching signal 19 output from the timer circuit 10, FIG.
As indicated by the arrow B in (a), the set time of the first detection mode is Ta2, which is shorter than the previous Ta1. That is, the ratio of the set time Tb of the second detection mode to the set time Ta2 of the first detection mode can be made larger than that before the detection of the moving object. In the first detection mode, a predetermined unit value is integrated by the moving time integration circuit 16 based on the Doppler component in the received signal, and the integrated value exceeds the threshold TH as shown in FIG. 2 (c). If this is the mode in which the moving object detection signal is output, if the first detection mode is a long time like Ta1 when the moving object is stopped, the integrated value thereof is the first detection mode. There is a possibility that it may decrease at times and become smaller than the threshold value TH. However, in the present invention, after the moving object is detected, the ratio of the set times in the first detection mode is reduced, and the object can be detected even when the moving object is stationary.
Since the ratio of the set time of the detection mode can be increased, the object detection can be ensured.

In the above embodiment, the set time Tb in the second detection mode is fixed and the set time Ta1 in the first detection mode is changed to Ta2 (corresponding to claim 2). Is not limited to this. For example, as shown in FIG. 3, while the set time Ta of the first detection mode is constant, the set times Tb1 and Tb2 of the second detection mode are set.
May be different before and after the output of the moving object detection signal (corresponding to claim 3). However, in this case, Tb
It is necessary to have a relationship of 1 <Tb2.

[0021]

As can be understood from the above description, according to the ultrasonic sensor of the present invention described in claims 1 to 3, the Doppler effect is utilized before the detection of the moving object. Since the ratio of the time setting of the first detection mode for detecting the moving object is increased by increasing the probability of the moving object invading the monitoring space when setting the first detection mode, In the second detection mode, it is possible to avoid the delay in the object detection timing due to the moving object invading the surveillance space as much as possible. Moreover, according to the present invention, after the moving object is detected, the second object which is excellent in detecting the existence of the stopped object is provided.
Since the ratio of the time setting of the detection mode is increased, even if the moving object stops in the monitoring space, its presence can be reliably detected, and the reliability of the moving object detection can be improved.

[Brief description of drawings]

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

FIG. 2 is a time chart showing an example of operating states of the ultrasonic sensor shown in FIG.

FIG. 3 is a time chart showing another example of the operating state of the ultrasonic sensor shown in FIG.

FIG. 4 is a time chart showing an example of an operating state of a conventional ultrasonic sensor.

[Explanation of symbols]

 1 Oscillator 2 Wave Sending Circuit 3 Wave Sending Device 4 Wave Receiving Device 5 Switching Circuit for Each Wave Sending 8 Detection Circuit 10 Timer Circuit 12 Detection Judgment Circuit 13 Transmission Method Determining Circuit 14 Detection Circuit 15 Comparison Circuit 16 Moving Time Integrating Circuit 17 1st Memory circuit 18 Second memory circuit 19 Switching control circuit S Ultrasonic sensor

Claims (3)

[Claims] 1. A transmitter for transmitting ultrasonic waves into a monitoring space,
The receiver includes a wave receiver that receives a reflected wave that is transmitted from this wave transmitter and that is reflected from an object existing in the surveillance space, and outputs the received wave signal. In the first detection mode in which the moving object is detected and determined based on the Doppler signal component, and in the monitoring space based on the received signal output from the receiver by transmitting the ultrasonic wave of the pulse train from the transmitter The second detection mode and the second detection mode for determining the presence or absence of the object are alternately switched at a predetermined time interval, and the output of the moving object detection signal is started in the first detection mode. In the ultrasonic sensor, the moving object detection signal is output when the ratio of the set time of the first detection mode to the set time of the second detection mode is higher than that when the moving object detection signal is output. Bigger when not An ultrasonic sensor characterized by being configured as follows. 2. The set time of the second detection mode according to claim 1, wherein the set time is set to a fixed time, and the set time of the first detection mode is set longer than when the moving object detection signal is output. Also, an ultrasonic sensor configured so that it takes a longer time when the moving object detection signal is not output. 3. The set time of the first detection mode is set to a fixed time, and the set time of the second detection mode is set to be longer than that when a moving object detection signal is output. Also, the ultrasonic sensor is configured so that it takes a shorter time when the moving object detection signal is not output.