JPH0357427B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a moving object detection device, more specifically,
Movement that detects the movement of an object by continuously emitting detection waves such as ultrasonic waves or microwaves of a predetermined frequency into the monitoring space and detecting the frequency shift of the reflected waves caused by the movement of the object. The present invention relates to an object detection device.

[Background technology] Generally, this type of moving object detection device emits ultrasonic waves or microwaves of a predetermined frequency as a detection wave, and when the detected object moves within the monitoring space, the Doppler effect contained in the reflected wave is detected. There are devices for detecting frequency shifts that are disclosed in Japanese Patent Laid-Open No. 55-63774 and US Pat. No. 3,432,855.

FIG. 3 shows an example of this type of moving object detection device using ultrasonic waves as detection waves, and shows the transmitter 1.
The output of the oscillation circuit 10 is applied to the transmitter 1 to emit ultrasonic waves into the air, and the reflected waves are transmitted to the receiver 2.
is received and converted into an electrical signal. The received signal Ein, which is the output of the receiver 2, is input to the converter circuit 20. The converter circuit 20 includes a phase shift circuit 22 that shifts the phase of the output signal of the oscillation circuit 10 by 90 degrees, and an output signal Ex of the oscillation circuit 10 and a received signal.
Ein and the output signal Ey of the phase shift circuit 22 and the received signal
A pair of mixer circuits 21a and 21b that output intermediate signals E and E', which are each beat signal of Ein, and a pair of amplifier circuits 2 that amplify each intermediate signal E and E', respectively.
3a, 23b, and a pair of binary conversion circuits 24a, which convert the output signals of the amplifier circuits 23a, 23b into shaft code signals X, Y whose output level becomes "H" or "L", respectively, corresponding to the positive or negative state of the output signals. 24b, and the double-axis code signals X, Y are intermediate signals E,
The received signal Ein is input to a quadrant detection circuit 25 which determines in which quadrant the received signal Ein exists in a vector plane with E' as the unit axis. In the quadrant detection circuit 25, when the level detection circuit 30 detects that the signal level of the intermediate signals E and E' is above a predetermined level, it outputs a quadrant signal ~, and the quadrant signal ~ is sent to the quadrant transition direction detection circuit 26. When the received signal Ein moves to another quadrant in the vector plane, the quadrant transition direction detection circuit 26 determines the output level depending on whether the direction of movement is clockwise or counterclockwise around the origin. outputs a digital signal in which the signal becomes "H" or "L". Here, the direction in which the quadrant moves corresponds to the moving direction of the moving object, and is set so that when the moving object approaches, it turns counterclockwise, and when it moves away, it turns clockwise. The output of the quadrant transition direction detection circuit 26 is applied to an integration circuit 27 to integrate the number and direction of quadrant transition, and the output of the integration circuit 27 is applied to a threshold circuit 28. In the threshold circuit 28, 2 of the power supply voltage Vcc
A first set voltage smaller than the voltage of 1/2 and a second set voltage larger than the voltage are set, and the input signal is lower than the first set voltage or higher than the second set voltage. Send out an alarm signal at certain times. That is, when the quadrant transition occurs a plurality of times and the direction of the transition occurs in the same direction a predetermined number of times or more, the output of the integrating circuit 27 becomes below the first set voltage or above the second set voltage, and the threshold is reached. An alarm signal is sent from the value circuit 28.
The alarm signal sent from the threshold circuit 28 is sent to a display drive circuit 29 that drives a display that notifies an alarm.
is input. Therefore, if the moving object continues to move in the same direction, an alarm signal is output from the threshold circuit 28, and the display drive circuit 29 is driven to notify the presence of the moving object. It is.

By the way, in the above configuration, the converter circuit 20 includes the phase shift circuit 22 and the pair of mixer circuits 2.
1a, 21b and a pair of amplifier circuits 23a, 23b
and a pair of binary conversion circuits 24a and 24b, which poses a problem in that the circuit configuration is complicated and the cost is high.

[Object of the Invention] The present invention has been made in view of the above points, and its main purpose is to provide a moving object detection device that can simplify the circuit configuration of a converter circuit and reduce costs. It's about doing.

[Disclosure of the Invention] (Example) The configuration of the present invention will be explained based on FIG. In the following explanation, an example will be shown in which ultrasonic waves are used as detection waves for the object to be detected, but as long as the detection waves have a wavelength of about 1 cm or smaller, for example, microwaves may be used.

The transmitter 1 is driven by an output signal of an oscillation circuit 10 that continuously oscillates at a constant frequency.
Ultrasonic waves are emitted from the monitor into the monitoring space. The ultrasonic wave emitted from the transmitter 1 is reflected by an object existing in the monitoring space, and the reflected wave is received by the receiver 2, which converts it into a received signal Ein. Transmitter 1
Both the and receiver 2 are composed of piezo elements, etc., and the transmitter 1 emits ultrasonic waves that match the frequency of the applied electric vibrations, and the receiver 2 emits ultrasonic waves that match the frequency of the received ultrasonic waves. Outputs the received signal Ein that matches. The received signal Ein received by the receiver 2 is input to the converter circuit 20. converter circuit 2
0 is an amplifier circuit 31 that amplifies the received signal Ein;
Shift the output signal of the oscillation circuit 10 by 90 degrees (here
(delayed by 90 degrees) phase shift circuit 22 and received signal
Ein, the output signal Ex of the oscillation circuit 10, and the received signal
It is comprised of a pair of subtraction circuits 32a and 32b to which Ein and the output signal Ey of the phase shift circuit 22 are respectively input. Both subtracting circuits 32a and 32b are constituted by D flip-flop circuits, and in the first subtracting circuit 32a, the received signal Ein is inputted to the clock terminal C, and the output signal Ex of the oscillation circuit 10 is inputted to the data terminal D. A pulse with a frequency equal to the frequency difference is obtained from the non-inverting output terminal Q, and this pulse corresponds to the axis sign signal X of the X axis in the vector plane. Also,
In the second subtraction circuit 32b, the received signal Ein is input to the clock terminal C, the output signal Ey of the phase shift circuit 22 is input to the data terminal D, and a pulse having a frequency equal to the frequency difference between the two is obtained from the non-inverting output terminal Q. This pulse corresponds to the axis sign signal Y of the Y axis of the vector plane. That is, conventionally, intermediate signals E and E' equal to the frequency difference between the received signal Ein, the output signal Ex of the oscillation circuit 10, and the output signal Ey of the phase shift circuit 22 are sent to the mixer circuit 23.
a, 23b, and then converted into axis code signals X, Y, which are digital signals corresponding to the positive and negative signs of the intermediate signals E, E', by the binary conversion circuits 24a, 24b, but in this case, With this configuration, the axis code signals X and Y can be directly obtained without generating intermediate signals E and E', which simplifies the circuit configuration. Here, when an object that reflects ultrasonic waves approaches the receiver 2, the frequency of the reflected wave becomes higher than the oscillation frequency, so the phase of the axis code signal X leads the phase of the axis code signal Y. Conversely, when the object moves away from the receiver 2, the frequency of the reflected wave becomes lower than the oscillation frequency, so the phase of the axis code signal X lags behind the axis code signal Y. Therefore, in a vector plane with axis code signals X and Y as the basic axes, when an object approaches, the rotation vector represented by the received signal Ein rotates counterclockwise around the origin, and when the object moves away, it rotates clockwise. It rotates. Each subtraction circuit 32a,
The axis code signals X and Y, which are the outputs of the 32b, are input to the quadrant detection circuit 25, and the quadrant detection circuit 25 determines in which quadrant the received signal Ein is located in the vector plane based on the combination of the axis code signals X and Y. To detect. In other words, if both axis code signals X and Y are "H", it is determined that it is in the first quadrant, and if both are "L", it is determined that it is in the third quadrant, and the quadrant signal ~ corresponding to each quadrant is output. be.
Here, the received signal detection circuit 3 to which the axis code signal Y is inputted to the non-inverting output terminal Q of the second subtraction circuit 32b.
3 is connected, and the received signal detection circuit 33 differentiates the axis code signal Y, and when the differential output is not 0, the quadrant detection circuit 25 is set to a state where the quadrant signal ~ can be output. In other words,
When no frequency deviation occurs, the received signal Ein
Since the frequencies of the output signal Ey of the phase shift circuit 22 and the output signal Ey of the phase shift circuit 22 are equal, the output level of the subtraction circuit 32a becomes a constant level of "H" or "L" and no differential output is obtained. I'm trying to make sure I don't get it. In this way, the quadrant signal ~ obtained when the received signal Ein has a frequency shift is input to the quadrant transition detection circuit 26, and the quadrant transition detection circuit 26 changes the rotation vector of the received signal Ein to another quadrant in the vector plane. When it moves, it outputs a pulse that makes the output level "H" or "L" depending on whether the movement is counterclockwise or clockwise around the origin.
Here, “H” corresponds to the power supply voltage, and “L” corresponds to 0V.
"H" indicates counterclockwise rotation and "L" indicates clockwise rotation. The output of the quadrant transition detection circuit 26 maintains its original value until the rotation vector moves to another quadrant or the rotation vector becomes 0 vector. The output of the quadrant transition detection circuit 26 is integrated by an integrating circuit 27. The output of the integrating circuit 27 is input to a threshold circuit 28, which uses a voltage V _DD /2, which is one half of the power supply voltage, as a reference value, and compares it with a first reference value smaller than the reference value. A second reference value larger than the above value is set, and when the output of the quadrant transition detection circuit 26 is less than or equal to the first reference value or greater than or equal to the second reference value, the output level is set to "H". At other times, the output level is set to "L". That is, when the rotation vectors are in the same direction and quadrant transition occurs a predetermined number of times or more, the output level of the integrating circuit 27 becomes equal to or higher than the first reference value of the threshold circuit 28 or equal to or lower than the second reference value. At times, the output level of the threshold circuit 28 becomes "H", and a drive signal for driving the display device is outputted from the display device drive circuit 29 as appropriate.

(Operation) The operation will be explained below based on FIG. 2. Note that S ₁ to _{S 6} in FIG. 2 indicate the signals of the corresponding parts in FIG. 1, and the signals of group A in FIG. When the detected object moves away, the C group signals indicate that disturbance noise or the like is received, and the D group signals indicate that there is no moving object within the monitoring space.

The output signal Ey of the phase shift circuit 22 is S ₁ and the oscillation circuit 1
The output signal Ex of 0 is represented by _S2 , and the phase difference between the two signals is π/2 (90 degrees). When the object to be detected approaches, the reception frequency becomes higher than the oscillation frequency, so if the oscillation frequency is f ₀ , the reception frequency can be expressed as f ₀ +Δf. However, in the first subtraction circuit 32a, an output signal _S4 having a frequency equal to the frequency difference δf between the output signal _S2 of the oscillation circuit 10 and the received signal _S3 is obtained, and the second subtraction circuit 32b
Then, an output signal S ₅ having a frequency equal to the frequency difference δf between the output signal S ₁ of the phase shift circuit 22 and the received signal S ₃ is obtained. Both output signals S ₄ and S ₅ are axis code signals X and Y, respectively, and as is clear from the signals of group A in Figure 2, the rotation vector is on the left in a vector plane with axis code signals X and Y as the basic axes. It will rotate around. While the counterclockwise quadrant transition is occurring continuously, the output level of the quadrant transition detection circuit 26 is as shown by the signal _S6 of group A in FIG.
When the leftward quadrant transition occurs a predetermined number of times, the output level of the integrating circuit 27 becomes higher than the first reference value of the threshold circuit 28, and the drive signal from the display drive circuit 29 becomes "H". It is output. When the object to be detected existing in the monitoring space moves away, the output level of the quadrant transition detection circuit 26 becomes "L", as in the signal _S6 of group B in FIG. In this case as well, a drive signal is output when quadrant transition occurs in the same direction a predetermined number of times.

When receiving disturbance noise, Fig. 2C
Since the frequency of the received signal S ₃ changes irregularly like a group, the axis code signals S ₄ and S ₅ also change irregularly,
Therefore, the output level of the quadrant transition detection circuit 26 repeats "H" and "L" in a short time, and the output level of the integrating circuit 27 reaches the first level of the threshold circuit 28.
Since the drive signal is not greater than or equal to the second reference value or less than the second reference value, the drive signal is not output, and false alarms do not occur.

If there are no moving objects within the monitoring area,
As shown in group D in FIG. 2, since the frequency of the received signal _S3 is equal to the frequency of the output signal _S2 of the oscillation circuit 10, the shaft code signals _S4 and _S5 are in the "H" or "L" state. is maintained and no change occurs,
The input signal S ₆ of the integrating circuit 27 is at the reference level V _DD /2
In this case, false alarms will not occur.

[Effects of the Invention] As described above, the converter circuit includes a phase shift circuit that shifts the phase of the output signal of the oscillation circuit by 90 degrees, and an output signal of the oscillation circuit and a received signal that are input to the converter circuit, and a phase shift circuit that shifts the phase of the output signal of the oscillation circuit by 90 degrees. A first subtraction circuit consisting of a flip-flop circuit that generates pulses of equal frequency, and a second subtraction circuit consisting of a flip-flop circuit that receives the output signal of the phase shift circuit and the received signal and generates a pulse of frequency equal to the frequency difference between the two. This has the advantage that the conventionally complicated circuit configuration of the converter circuit can be simplified and costs can be reduced. Also, since the subtraction circuit is composed of a flip-flop circuit,
This has the advantage that there are fewer adjustment points and improved reliability compared to a conventional mixer circuit that handles analog signals.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is an explanatory diagram of the same operation as above, and FIG. 3 is a block diagram showing a conventional example. 1 is a transmitter, 2 is a receiver, 10 is an oscillation circuit, 2
0 is a converter circuit, 22 is a phase shift circuit, 25 is a quadrant detection circuit, 26 is a quadrant transition detection circuit, 27 is an integration circuit, 28 is a threshold circuit, 29 is a display drive circuit, 32a is a first subtraction circuit, 32b is a second subtraction circuit.

Claims (1)

[Claims] 1 An oscillation circuit that oscillates continuously at a constant frequency,
a transmitter to which the output of the oscillator circuit is applied and radiates a detection wave into the monitoring space; a receiver which receives reflected waves from a detected object in the monitoring space and outputs a received signal;
A converter circuit that converts the received signal output from the receiver into a pair of axis code signals with different phases, and a quadrant signal corresponding to the quadrant in which the received signal exists in a vector plane with the two axis code signals as the basic axes. A quadrant detection circuit that sends out a quadrant detection circuit, a quadrant transition detection circuit that sends out one positive or negative pulse corresponding to the direction of movement each time the quadrant signal moves to another quadrant of the vector plane, and a quadrant transition detection circuit. In the moving object detection device, the converter circuit includes a drive circuit that appropriately drives the display when a predetermined number of pulses are output in the same direction from the oscillation circuit. The first circuit consists of a phase circuit and a flip-flop circuit which receives the output signal of the oscillation circuit and the received signal and generates a pulse with a frequency equal to the frequency difference between the two.
A moving object comprising: a subtraction circuit; and a second subtraction circuit comprising a flip-flop circuit which receives the output signal of the phase shift circuit and the received signal and generates a pulse with a frequency equal to the frequency difference between the two. Detection device.