JPS6040079B2 - Ultrasonic intrusion detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic intrusion detector that utilizes the Doppler effect, and its purpose is to have high detection sensitivity for human movement, and to prevent detection due to other physical phenomena. It is an object of the present invention to provide an ultrasonic intrusion detector with a simplified configuration, which reduces the probability of detection operations and, in particular, prevents malfunctions due to bells or the like that greatly disturb the ultrasonic sound field.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of the present invention, in which 1 is an oscillation circuit, 2 is a frequency divider, 3 is a 900 phase difference generation frequency divider circuit, 4 is an amplifier circuit, and 5 is a wave transmitting element. , 6 is a wave receiving element, 7 is an amplifier circuit, 8 and 9 are first and second quadrature phase detection circuits, 10 and 11 are first and second low-pass filters, and 12 and 13 are first and second quadrature detection circuits. second enlarged shaping circuit, 14,
15 is a first and second phase difference detection circuit, 16 is an inversion circuit, 17 and 18 are first and second detection and integration circuits, 19 is an in-phase component removal circuit, 20 is a D/A conversion circuit, 21, 22 is an upper limit and lower limit determination circuit, and 23 is an output circuit. Figure 2 shows a specific circuit example based on the block diagram in Figure 1 above.
Parts in the circuit shown in the figure that are equivalent to those in the circuit shown in FIG. 1 are given the same numbers. Therefore, the ultrasonic wave emitted from the wave transmitting element 5 has a frequency f of the emitted ultrasonic wave, assuming that there is no change in the warning area where the ultrasonic wave is emitted, as shown in FIG. 3a.
The frequency fo of the received ultrasonic wave coincides with the frequency fo of the received ultrasonic wave, and a signal having a single frequency f= without sidebands is received by the wave receiving element 6, as shown in FIG.

However, if there is a moving object M such as a human being in the warning area as shown in Figure 4a, △f is the Doppler frequency, and c
When is the sound speed of the ultrasonic wave, v is the speed of the moving body M, and f is the radiated ultrasonic frequency as described above, the relationship Δf; neck f)/c holds true. This becomes positive or negative depending on the speed direction, but it is included as a sideband in the received signal, and as shown in Figure 4b, when the moving object M approaches, an upper sideband component occurs, When the body M moves away, a lower sideband component is generated, and the received signal is obtained as a single sideband wave (SSB wave) in the communication system. However, on the other hand, the ultrasonic waves radiated into the space are received by the wave receiving element 6 as a composite of the waves reflected from various parts within the radiation area, so movements that should not be detected are detected. There is an object that has
When there is movement in the air, which is the propagation medium of ultrasonic waves, the ultrasonic signals from each of these paths are emitted as shown in Figure 5a.
The signal obtained by combining C and D will be received as a signal with amplitude changes that change moment by moment as shown in E of the figure, and therefore as a double sideband wave (DSB wave) as shown in B of the figure. This is an AM wave with sidebands distributed on both the upper and lower sides. In this way, the actual received signal when the mobile object M is present has a composite spectrum as shown in FIG. 6, which is a composite of FIGS. 3 to 5b. As clarified above, in order to detect the moving body M, the detection operation may be performed when the distribution of the upper and lower sidebands becomes uneven. Therefore, in order to extract one upper and lower sideband, quadrature detection circuits 8, 9,
Low-pass filters 10, 11, Masanaka shaping circuits 12, 13
, phase difference detection circuits 14 and 15 are provided, but when the input is a single sideband signal, the quadrature phase detection circuits 8 and 9 have a phase difference of 900 and can extract the signal. On the other hand, when the DSB wave has both sidebands, the output is in-phase. However, this in-phase component is not necessary to detect the moving object M, and a strong sound wave such as a bell B disturbs the air, which is the medium of ultrasonic waves, as shown in Figure 7a, and This creates a strong DSB signal in the received signal, so it is necessary to cut it. In this case, the phase difference detection circuits 14 and 15 of the circuit shown in FIG. However, this in-phase component can be removed by resistance-coupling the D/A conversion circuit 20. This is because even if the outputs of the phase difference detection circuits 14 and 15 are both generated at the same time, the voltage will be Vcc/2 because the non-inverted output and the inverted output are divided by resistance. On the other hand, the spectrum of the bell's sound is distributed not only in the audio frequency band but also in the ultrasonic band, but this distribution is not always constant, and at a certain moment it shows the spectrum distribution as shown in Figure 8a. However, at another instant, the spectrum distribution becomes as shown in b in the same figure, resulting in a very random spectrum distribution that changes every moment. The spectrum of the transmitted signal is randomly distributed vertically as sidebands. There is no problem if such a random distribution is distributed in a well-balanced manner, but if the ever-changing spectrum distribution becomes unbalanced on average, a detection operation will occur in the detector circuit. Therefore, in the present invention, the human movement continues in one direction for a certain period of time, and therefore, the received signal due to the human movement has either the upper or lower sideband lasting for a certain period of time, but it is not included in the bell etc. We focused on the fact that the ultrasonic components generated randomly generate sidebands on the upper and lower sides, and in such cases, the detection limit level is canceled depending on the level of the opposite sideband, and the bell This prevents malfunctions caused by such factors. That is, in FIG. 1, the phase difference detection circuit 14 outputs the upper sideband component as a pulse, and the other phase difference detection circuit 15 outputs the lower sideband component as a pulse.

When a moving object M such as a human moves toward the detector, an output is output to the phase difference detection circuit 14, and conversely, when a moving object M moves away from the detector, the output is output to the phase difference detection circuit 14.
It is output to the other phase difference detection circuit 15. At this time, when the single-side band component is detected, the upper limit determination circuit 21 or the lower limit determination circuit 22 passes through the in-phase component removal circuit 19 and the D/A conversion circuit 20.
That is, when an upper sideband component exists, the upper limit determination circuit 21 determines, and when a lower sideband component exists, the lower limit determination circuit 22 determines the presence of the lower sideband component.
The output circuit 23 operates based on the determination.
However, when both sideband components exist randomly, such as in a bell etc., the common mode component removal circuit 19 and the D/A conversion circuit 2
0 cannot be canceled, and the upper and lower limit judgment circuits 21 and 22
is determined and a signal is output to the output circuit 23, resulting in malfunction. Therefore, in order to prevent this malfunction, when there is an output pulse from the phase difference detection circuit 14, the detection and integration circuit 17 converts it into a DC voltage and moves it to the side that raises the judgment level of the lower limit judgment circuit 22. When the output of the phase difference detection circuit 15 is present, the detection and integration circuit 18 converts it into a DC voltage and moves it to the side that raises the determination level of the upper limit determination circuit 21. That is, as shown in FIG. 9, when the upper sideband component is output from the D/A conversion circuit 20, the level of the component is detected to exceed the upper limit determination level of the upper limit determination circuit 21. (Figure 9A). At this time,
Based on the output of the phase difference detection circuit 14, the detection and integration circuit 17 raises the determination level of the lower limit determination circuit 22 as shown in FIG. 9B. Further, when it is a lower sideband component, it is detected as exceeding the lower limit judgment level of the lower limit judgment circuit 22, as shown in FIG. 9C. At this time, the output pulse of the phase difference detection circuit 14 causes the detection and integration circuit 18 to raise the determination level of the upper limit determination circuit 21 as shown in FIG. 9D. In this way, when a sideband component exists, the judgment level of the judgment circuit for the opposite sideband is changed, and the judgment level of the judgment circuit that is trying to detect it does not change. This has no effect on the detection operation. next,
As shown in FIG. 9E, when a double-side band component such as a bell exists, F, G
As shown in FIG. 3, the determination levels of the upper and lower limit determination circuits 21 and 22 are raised to prevent malfunctions from exceeding the determination levels. As described above, the present invention includes a mechanism that emits ultrasonic waves to a guarded area, and a mechanism that receives reflected waves of the emitted ultrasonic waves from the guarded area, and transmits the received signals to the The frequency of the ultrasonic waves generated is divided into an upper sideband and a lower sideband, and a detection output is generated when the distribution state and amount of this distribution become uneven for a certain period of time or longer. Therefore, the detection performance for moving objects to be detected such as humans is not impaired, and furthermore, it has the effect of preventing malfunctions due to the influence of bell sounds and the like.

In addition, since it is equipped with a common-mode removal circuit and a negative-phase removal circuit to remove both sideband components, even if the in-phase output is due to a signal in both sidebands, the common-mode removal circuit can remove the in-phase component. This feature has the advantage that even in the case of an anti-phase component, it can be removed by an anti-phase removal circuit.

Furthermore, if the subspectrum for the transmitted signal is randomly distributed vertically and well-balanced as sidebands, it can be removed by the above-mentioned in-phase removal circuit, but the ever-changing subspectrum distribution due to Bell etc. If the signals are unbalanced, a detection error will occur, but the sensor is equipped with a mechanism that cancels the detection limit level of the opposite sideband depending on the distribution state and amount of distribution of the signals in the upper and lower sidebands. In other words, the detection limit level on the opposite side of the sideband component is set so that the sideband component is not detected. It has the effect of not malfunctioning due to signals of both sideband components, and by moving the detection limit level on the opposite side of the sideband components, there is no effect on the detection of true upper or lower sideband components. It is something that produces an effect that cannot be given. Brief Description of the Drawings Figure 1 is a circuit block diagram of an embodiment of the present invention, Figure 2 is a specific circuit diagram of the same as the above, and Figures 3 a and b are ultrasonic wave transmission and reception when the above moving body is not present. An explanatory diagram showing the state and a frequency spectrum diagram of the received signal, Figures 4a and b are an explanatory diagram and a frequency spectrum diagram of the received signal, Figure 5 Diagram a
, b is a waveform diagram and its frequency spectrum diagram showing the combined state of the received ultrasonic waves from the plurality of paths as above, FIG. 6 is an actual frequency spectrum diagram when the same as the above moving object is present, and FIG. 7 a , b is an explanatory diagram showing the state of ultrasonic wave transmission and reception when there is a bell etc. as above, and a waveform diagram of the received signal, Fig. 8a
, b are frequency vector diagrams at different times of the random vector obtained by Bell et al., and FIG. 9 is an explanatory diagram of the operation.

Figure 3 Figure 1 Figure 2 Figure 9 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1 A mechanism that emits ultrasonic waves to a restricted area, a mechanism that receives reflected waves of the emitted ultrasonic waves from the restricted area, and a mechanism that transmits the received signals to a frequency higher than that of the emitted ultrasonic waves. The device is equipped with a mechanism that divides the wave band into a wave band and a lower side band, and generates a detection output when the distribution state and amount of the distribution become uneven for a certain period of time or more, and detects the received double side band component. A common-phase removal circuit and a negative-phase removal circuit are provided to remove the signal, and a mechanism is provided that operates to cancel the detection limit level of the opposite sideband depending on the distribution state and distribution amount of the signals in the upper and lower sidebands. An ultrasonic intrusion detector consisting of