JP5222092B2 - Human body detection device - Google Patents

Description

Based on the microwave band thermal noise emitted from a human body, it relates to the human body detecting device for detecting the presence of a human body.

Conventionally, as this type of human body detection device, as shown in Patent Document 1, a sensor unit including a transmission element and a reception element is provided in a seat cushion on which an occupant is seated, and microwaves are transmitted from the transmission element to a seating surface. It is known that the presence or absence of a human body is detected from the sinking amount of the seat cushion (distance to the seating surface) by transmitting the signal toward the receiver and receiving the reflected wave with a receiving element.
JP 2006-208236 A

  By the way, at present, microwaves, which are relatively high-frequency radio waves, can generate heat in the irradiated object, and there is concern about the influence on the living body. However, the conventional human body detection device has a problem from the viewpoint of influence on the human body because the microwave is transmitted from the transmitting element toward the occupant.

  There is also a concern that the microwaves transmitted from the transmitting element may affect other electronic devices. For example, when a microwave is transmitted in a vehicle, there is a problem in that noise or the like may be generated in an electronic device and an abnormality may occur in instruments.

  Furthermore, in the conventional human body detection apparatus, the presence or absence of a human body is detected from the sinking amount of the seat cushion. For this reason, when the seat cushion sinks in addition to the seating of the occupant (for example, when a heavy load is placed on the seat cushion), an inconvenience that an occupant is present is erroneously detected.

  In view of the above circumstances, an object of the present invention is to provide a human body detection device that can easily and reliably detect the presence of a human body without transmitting a microwave.

The present inventor pays attention to the fact that the human body temperature is a constant heat source of 35 ° C. to 40 ° C., and a predetermined microwave band thermal noise is also emitted from such a heat source, and the characteristics of the microwave in the space The knowledge that the existence of the human body can be detected by capturing the change is obtained. Thermal noise appears not only in the microwave band but also in a wide frequency band, but the microwave band was used for ease of signal handling.

Accordingly, the present invention provides a human body detection device that detects the presence of a human body based on microwave thermal noise emitted from a human body, the receiving unit receiving the microwave, and the microwave received by the receiving unit. A filter unit that extracts a microwave in a band that is spatially attenuated by absorption of gas molecules from the wave, a voltage converter that converts a microwave waveform cut out through the filter unit into a voltage waveform, and conversion by the voltage converter And a signal processing unit for detecting the presence of a human body based on the voltage waveform.

According to the human body detection device of the present invention, a predetermined frequency band in which the microwave band thermal noise emitted from the human body is characteristically changed is extracted from the microwave band thermal noise received by the receiving unit, and the voltage waveform is obtained. Then, the presence or absence of a human body is detected based on the change in the voltage waveform. Therefore, there is no need to transmit microwaves, the apparatus configuration can be simplified, and the human body and other electronic devices are not affected.
Here, the predetermined frequency band is a band that is spatially attenuated by absorption of gas molecules. That is, by extracting a band that is spatially attenuated by absorption of gas molecules such as water vapor molecules from the microwave received by the receiving unit, the influence can be reduced even when there is a heat source close to the human body in the vicinity. The characteristic change of the microwave can be reliably captured. Thereby, presence of a human body can be detected easily and reliably.

In addition, since the microwave band thermal noise emitted from the human body is directly received, the presence or absence of the human body can be reliably detected regardless of physical changes in the surrounding environment such as the sinking of the sheet.

  Thus, according to the human body detection device of the present invention, it is possible to reliably detect the presence of a human body without transmitting a microwave.

Further, in a preferred embodiment of the present invention, the signal processing unit is in the range of the voltage waveform is defined by either or both the upper limit value and the lower limit value corresponding to the microwave band thermal noise emitted from the human body In this case, the presence of a human body is detected.

According to this mode, by capturing the upper limit value and the lower limit of the micro-wave band thermal noise characteristic change the voltage waveform of emitted from the human body, to detect the presence of a human body in a simple configuration of the setting of the threshold Can do.

  Furthermore, in a preferred aspect of the present invention, the receiving unit is composed of an antenna having directivity, and the signal processing unit detects the presence of a human body in the directivity range of the antenna.

  According to this aspect, by using a directional antenna in the receiving unit, it is possible to detect the presence of a human body for each area of the directional range, for example, by detecting the intrusion of a suspicious person for each area, The human body detection device can be used as an entry detection device.

  Furthermore, in a preferred aspect of the present invention, the antenna is provided in a vehicle seat with a directivity range facing the seated person, and the signal processing unit detects the presence of the seated person on the seat. And

According to this embodiment, the case of providing an antenna in the seat is also for receiving a micro wave band thermal noise emitted from the seated person directly, without being affected by the physical change in the surrounding environment such as sinking of the sheet, the human body The presence or absence of can be reliably detected. In addition, since the microwave is not transmitted, it is possible to avoid the occurrence of noise or the like in the electronic device when mounted on the vehicle.

  With reference to FIG. 1, the case where a human body detection apparatus is mounted in a vehicle is demonstrated as one Embodiment of this invention.

The human body detection apparatus is connected to a plurality of antennas 1a and 1b as receiving units for receiving microwaves, a selector switch 2 for selecting one antenna from the plurality of antennas 1a and 1b, and a selector switch, and has a predetermined frequency. A band limiting filter 3 (corresponding to the filter unit of the present invention) that extracts microwave band thermal noise of the band, a microwave amplifier 4 that is connected to the band limiting filter 3 and amplifies the microwave, and a microwave amplifier 4 A square detector 5 (corresponding to a voltage converter of the present invention) connected to convert a microwave waveform into a voltage waveform, a voltage amplifier 6 that amplifies a voltage value converted by the square detector 5, and a voltage amplifier 6 is connected to the upper limit comparison circuit 7a and the lower limit comparison circuit 7b, and is connected to the upper limit comparison circuit 7a and the lower limit comparison circuit 7b. It comprises a signal processing unit 8 for detecting a control unit 9 for controlling the selection of the changeover switch 2, a determining unit 10 connected to the control unit 9 and the signal processing unit 8.

  The antennas 1a and 1b are directional antennas such as horn antennas and patch antennas, and are installed inside the seats 11a and 11b so that a seated person can enter the directional range. Specifically, as shown in FIG. 1, the antennas 1a and 1b are installed at positions where the backrest of the seats 11a and 11b is low so that the center of the directivity range is the waist position of the seated person. The gain of the antennas 1a and 1b in the embodiment is 3 [dB] including the loss due to the sheet portion.

  The changeover switch 2 selects one antenna from the plurality of antenna antennas 1 a and 1 b based on the control signal of the control unit 9, and outputs the output of the selected antenna to the band limiting filter 3.

The band limiting filter 3 limits the input microwave band (band band) to a band that is spatially attenuated by absorption of gas molecules. In the present embodiment, the band limiting filter 3 limits to 22.24 GHz where the absorption attenuation due to water vapor molecules is large. In addition to 22.24 GHz, the band limiting filter 3 may employ 60 GHz or 120 GHz as a frequency band in which absorption attenuation due to oxygen molecules is large, and 183.3 GHz as a frequency band in which absorption attenuation due to water vapor molecules is large. By limiting the microwave band thermal noise in these bands, if the object show comparable The higher temperature and the human body in the vehicle is also present, to reduce these effects, the human body in space A characteristic change of the emitted microwave band thermal noise can be reliably captured.

  The microwave amplifier 4 is an amplifier for gain adjustment, and sends the amplified microwave to the square detector 5. In the present embodiment, the microwave amplifier 4 has a gain of 65.8 dB and a noise figure of 5 dB.

  The square detector 5 is constituted by, for example, a Schottky diode, and has a characteristic of converting a microwave (power value) as an input value into a DC voltage value proportional to the square thereof. The converted voltage value is sent to the voltage amplifier 6 and amplified by the voltage amplifier 6. In the present embodiment, the square detector 5 has an input level of −30 dBm to −10 dBm and a detection characteristic of square: ± 0.1 power. The amplification factor of the voltage amplifier 6 is 8 times.

  Instead of the square detector 5 and the voltage amplifier 6, a logarithmic amplifier in which these functions are integrated may be used.

The upper limit comparison circuit 7a is a differential amplifier that compares an upper limit value V _Max of a preset voltage with the voltage value amplified by the voltage amplifier 6 and sequentially executes an output corresponding to the difference. The value comparison circuit 7 b is a differential amplifier that compares a lower limit value V _min of a preset voltage with the voltage value amplified by the voltage amplifier 6 and sequentially executes an output corresponding to the difference.

Specifically, the upper limit comparison circuit 7a sets the reference voltage obtained by the power source 7c as the upper limit value V _Max of the voltage, and connects this to the + input terminal, and the voltage amplified by the voltage amplifier 6 is applied to the − input terminal. When the voltage is lower than the upper limit value V _Max , an H level voltage signal indicating a normal value is output, and when the voltage is higher than the upper limit value V _Max , an L level voltage signal indicating an abnormality is output. Is output.

On the other hand, the lower limit comparison circuit 7b sets the reference voltage obtained by the power source 7d as the lower limit value _Vmin of the voltage, connects this to the − input terminal, and connects the voltage amplified by the voltage amplifier 6 to the + input terminal. When the voltage exceeds the lower limit value _Vmin , an H level voltage signal indicating a normal value is output. When the voltage is lower than the lower limit value _Vmin , an L level voltage signal indicating an abnormal value is output. Is output.

Here, the set values of the upper limit value V _Max of the upper limit value comparison circuit 7a and the lower limit value V _min of the lower limit value comparison circuit 7b will be described.

  First, the microwave P [W] is expressed as the following equation (1) as a function of the temperature T.

P = K × T × B (1)
Here, K: Boltzmann constant (1.38 × 10 ⁻²³ [J / K])
T: Absolute temperature [K]
B: Microwave power band When the temperature range that can be detected as a human body is 30 ° C. to 50 ° C., first, microwave P ₃₀ [W] emitted from an object at 30 ° C. is calculated based on the above equation (1). When the microwave power band is calculated as 100 [MHz], the following formula (2) is obtained.

P ₃₀ [W] = 1.38 × 10 ⁻²³ × (273.5 + 30) × 100
= 4.188 × 10 ⁻¹³ [W] = − 93.8 [dBm] (2)
However, Q [W] = 10 × ₁₀ log ₁₀ (Q × 1000) [dBm]
From the above equation (2), the microwave power emitted from the human body at 30 ° C. is −93.8 [dBm], but the output values of the antennas 1a and 1b are −90.8 [dBm]. . From here, if the total gain 60.8 [dB] and the total noise figure 10 [dB] in the band limiting filter 3 and the microwave amplifier 4 are taken into account, the microwave power at the time of input to the square detector 5 is −20. [dBm]. When this is converted into a voltage value by the square detector 5, it becomes 0.25 [V], and further it becomes 2.0 [V] by amplifying it by a factor of 8 with a voltage amplifier.

  Thus, the detection voltage of the microwave emitted from the human body at 30 ° C. is theoretically 2.0 [V].

Similarly, when the microwave P ₅₀ [W] emitted from an object at 50 ° C. is calculated based on the above equation (1) and the microwave power band is 100 [MHz], the following equation (3) is obtained. Is required.

P ₅₀ [W] = 1.38 × 10 ⁻²³ × (273.5 + 50) × 100
= 4.464 × 10 ⁻¹³ [W] = − 93.5 [dBm] (3)
From the above formula (3), the microwave power emitted from the human body at 50 ° C. is −93.5 [dBm], but the output values of the antennas 1a and 1b are −90.5 [dBm]. . From here, if the total gain 60.8 [dB] and the total noise figure 10 [dB] in the band limiting filter 3 and the microwave amplifier 4 are taken into consideration, the microwave power at the time of input to the square detector 5 is −19. .7 [dBm]. When this is converted into a voltage value by the square detector 5, 0.2675 [
V], and further amplified by a factor of 8 with a voltage amplifier to 2.14 [V].

  Thus, the detection voltage of the microwave emitted from the human body at 50 ° C. is theoretically 2.14 [V].

Based on the above theoretical calculation results, the upper limit value V _Max of the upper limit value comparison circuit 7a is set to 2.14 [V], and the lower limit value V _min of the lower limit value comparison circuit 7b is 2.0 [V]. Set to

The signal processing unit 8 is a determination circuit, and the voltage waveform amplified by the voltage amplifier 6 is preset from the output values of the upper limit comparison circuit 7a and the lower limit comparison circuit 7b, and the upper limit value V _Max and lower limit of the voltage set in advance. It is determined whether or not the value is within the range of the value V _min and the determination result is output to the determination unit 10.

  Specifically, when the output values from the upper limit comparison circuit 7a and the lower limit comparison circuit 7b are both H level voltage signals indicating normal values, the signal processing unit 8 outputs a voltage signal indicating a normal value. When output to the determination unit 10 and one or both of the output values from the upper limit comparison circuit 7a and the lower limit comparison circuit 7b are abnormal values, a voltage signal indicating the abnormal value is output to the determination unit 10. .

  The determination unit 10 is configured by, for example, a multiplexer or the like, and determines whether there is an occupant in each of the seats 11a and 11b with the operation signal of the changeover switch by the control unit 9 and the determination result output from the signal processing unit 8 as inputs. To do.

  Specifically, the determination unit 10 refers to the output result output from the signal processing unit in synchronization with the antenna 1a (seat 11a) selected by the changeover switch, and the output result is a normal value indicating the presence of an occupant. In some cases, output from the output terminal 10a corresponding to the antenna 1a (sheet 11a) is performed. On the other hand, when the output result is an abnormal value that does not indicate the presence of an occupant, the output from the output terminal 10a is not performed.

  Similarly, referring to the output result output from the signal processing unit in synchronization with the antenna 1b (seat 11b) selected by the changeover switch, when the output result is a normal value indicating the presence of an occupant, Output from the output terminal 10b corresponding to the antenna 1b (sheet 11b) is performed. On the other hand, when the output result is an abnormal value that does not indicate the presence of an occupant, the output from the output terminal 10b is not performed. Thereafter, these processes are repeated for the number of antennas (seats), and the presence / absence of passengers is output for each antenna (seat).

  In the present embodiment, the determination unit 10 has a timer function and is configured to output the output from the output terminal when the output does not vary for a certain period of time.

  Next, with reference to FIG. 2, a passenger detection method by the human body detection device of the present embodiment will be described. In FIG. 2, the horizontal axis represents elapsed time [t], and the vertical axis represents the output voltage [V] of the voltage amplifier 6.

  First, the case where the inside of the vehicle and the seat are at a low temperature will be described with reference to FIG.

In this case, when no occupant is present near the seats 11a and 11b, the output voltage of the voltage amplifier 6 fluctuates randomly in the low voltage range. At this time, since the output voltage of the voltage amplifier 6 is not within the range defined by the upper limit value _VMax and the lower limit value _Vmin , the determination unit 10 does not output the presence of the occupant.

From this state, when the occupant approaches to seat on the seats 11a and 11b, the state gradually shifts to the high voltage range. Also at this time, basically, the output voltage of the voltage amplifier 6 is lower than the lower limit value _Vmin , and the output indicating the presence of an occupant is not performed from the determination unit 10.

When the occupant sits on the seats 11a and 11b, the antennas 1a and 1b installed on the seats 11a and 11b come close to the occupant's waist and the output voltage converges to a substantially constant value. At this time, the output voltage of the voltage amplifier 6 falls within a range defined by the upper limit value V _Max and the lower limit value V _min, and an output indicating the presence of an occupant is performed from the determination unit 10.

  Next, the case where the inside of the vehicle and the seat are hot will be described with reference to FIG.

In this case, when no occupant is present near the seats 11a and 11b, the output voltage of the voltage amplifier 6 fluctuates randomly in the high voltage range. At this time, the output voltage of the voltage amplifier 6 deviates from the range defined by the upper limit value V _Max and the lower limit value V _min, and no output indicating the presence of an occupant is performed from the determination unit 10.

From this state, when the occupant approaches to sit on the seats 11a and 11b, microwaves emitted from the human body are added, and the output voltage of the voltage amplifier 6 temporarily rises. Also at this time, basically, the output voltage of the voltage amplifier 6 exceeds the upper limit value V _Max , and the output indicating the presence of an occupant is not output from the determination unit 10.

When the occupant sits on the seats 11a and 11b, the antennas 1a and 1b installed on the seats 11a and 11b come close to the occupant's waist and the ambient temperature becomes constant, so the output voltage is almost constant. Converge to the value of. At this time, the output voltage of the voltage amplifier 6 falls within a range defined by the upper limit value V _Max and the lower limit value V _min, and an output indicating the presence of an occupant is performed from the determination unit 10.

  Next, a modified example of the present embodiment will be described with reference to FIG. In addition, about the component same as the said embodiment, description is abbreviate | omitted using the same referential mark.

  In the present embodiment, the antennas 1a ′ and 1b ′ are installed with their directivity ranges facing the areas 12a and 12b. Here, the areas 12a and 12b are positions or areas where a person such as an intruder should be detected, for example.

  The upper limit value comparison circuit 7a and the lower limit value comparison circuit 7b are provided with thermistors 7e and 7f for compensating for the influence of the ambient temperature.

According to the human body detection device having such a configuration, the upper limit value V _Max of the upper limit value comparison circuit 7a and the lower limit value V _min of the lower limit value comparison circuit 7b can be changed by the thermistors 7e and 7f in consideration of the ambient temperature. it can. Therefore, similarly to the above embodiment, based on whether or not a range where the output voltage of the voltage amplifier 6 is defined by the upper limit value V _Max and the lower limit value V _min, area 12a, and 12b Uchinohito simple And it can detect reliably.

As described above, according to the each embodiment, extracts predetermined frequency band microwave band thermal noise emitted from the human body is characteristic change detecting the presence or absence of a human body. Therefore, there is no need to transmit microwaves, the apparatus configuration can be simplified, and the human body and other electronic devices are not affected. Furthermore, since the presence / absence of the human body directly receives the microwaves emitted from the human body, the presence / absence of the human body can be reliably detected regardless of physical changes in the surrounding environment such as the sinking of the sheet. Thus, according to the human body detection device of the present embodiment, it is possible to reliably detect the presence of a human body without transmitting microwaves.

  Further, by using the detection result of the human body detection device according to the present embodiment (the output of the output terminals 10a and 10b of the determination unit 10), for example, the control of the air conditioner to the passenger in the vehicle and the start of the safety device such as the air bag It is possible to detect a suspicious person in the alarm area and report this to the outside.

  In the present embodiment, only the antennas 1a and 1b are shown in the drawing, but the present invention is not limited to this, and a plurality of antennas may be installed on sheets other than the sheets 11a and 11b. Similarly, in addition to the antennas 1a ′ and 1b ′, the antennas may be installed in a plurality of areas other than the areas 12a and 12b.

The figure which shows the human body detection apparatus structure of this embodiment. Explanatory drawing which shows the detection method of the human body by the human body detection apparatus of this embodiment. The figure which shows the example of a change of the human body detection apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a, 1b, 1a ', 1b' ... Antenna, 2 ... Changeover switch, 3 ... Band-limiting filter, 4 ... Microwave amplifier, 5 ... Square detector, 6 ... Voltage amplifier, 7a ... Upper limit comparison circuit, 7b ... Lower limit Value comparison circuit, 7c, 7d ... power source, 8 ... signal processing unit, 9 ... control unit, 10 ... determination unit, 10a, 10b ... output terminal, 11a, 11b ... sheet, 12a, 12b ... area.

Claims (4)

A human body detection device for detecting the presence of a human body based on microwave thermal noise emitted from the human body,
A receiver for receiving the microwave;
A filter unit for extracting microwaves in a band that is spatially attenuated by absorption of gas molecules from the microwaves received by the receiving unit;
A voltage conversion unit that converts a microwave waveform cut out through the filter unit into a voltage waveform; and
A human body detection device comprising: a signal processing unit that detects the presence of a human body based on the voltage waveform converted by the voltage conversion unit. The human body detection device according to claim 1 ,
The signal processing unit detects the presence of a human body when the voltage waveform is within a range defined by one or both of an upper limit value and a lower limit value corresponding to microwave thermal noise emitted from the human body. A human body detection device characterized by detecting. In the human body detection device according to claim 1 or 2 ,
The receiver is composed of a directional antenna,
The said signal processing part detects the presence of the human body of the directivity range of the said antenna, The human body detection apparatus characterized by the above-mentioned. The human body detection device according to claim 3 ,
The antenna is provided in a vehicle seat with a directivity range toward a seated person,
The human body detection device, wherein the signal processing unit detects the presence of a seated person on the seat.

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