JP2024142745A - LIVE BEAM DETECTION APPARATUS, LIVE BEAM DETECTION METHOD, AND LIVE BEAM DETECTION PROGRAM - Google Patents

Abstract

To shorten a time to be required for detecting an organism.SOLUTION: An organism detection device detects an organism. The organism detection device includes: an acquisition section for acquiring a detection signal from a sensor which detects a signal related to a fluctuation motion of the organism; a calculation section for integrating the size of a component included in a predetermined frequency band corresponding to the fluctuation motion so as to perform calculation as an organism detection value concerning the detection signals from a start time point of the organism detection to a present time point; and an absence determination stop section for stopping the organism detection by determining that the organism does not exist at the point of time when the integrated organism detection value becomes less than a first threshold.SELECTED DRAWING: Figure 2

Description

The present invention relates to a living body detection device, a living body detection method, and a living body detection program.

UWB (Ultra-Wide Band) communication transmits and receives a pulse signal with a short pulse width (wide frequency bandwidth and high distance resolution) between two communication devices, and the distance between the communication devices can be estimated from the time it takes for the pulse signal to travel back and forth between the communication devices. Due to this property, UWB communication can detect and manage whether a key terminal held by a user is within a specific distance range from the vehicle, and in recent years has begun to be used for smart key applications for vehicles as a countermeasure against relay attacks. Smart keys, also known as smart entry systems, can lock and unlock vehicle doors and start and stop the engine without using a mechanical key.

Measuring distance using UWB communication is similar to radar in that it converts the round-trip time of a pulse signal into distance. A communication device capable of UWB communication can be relatively easily turned into a radar without hardware modifications by receiving part of the pulse signal it transmits (the signal reflected by a surrounding detection target) by itself, in other words, by performing UWB communication with itself.

For example, Patent Document 1 discloses a device that uses a UWB antenna, which is used to lock and unlock the doors, to detect people left behind in a vehicle.

JP 2022-27637 A

Radar is used as one of the sensors to detect living bodies (babies, pets, etc.) left behind inside a vehicle, due to its characteristics of being able to penetrate blankets that cover the living body being detected and being able to detect minute displacements of the body surface caused by breathing. If a UWB communication device installed inside a vehicle is operated as a radar, detecting living bodies inside the vehicle is thought to be one of its applications.

However, when a UWB communication device is operated as a radar for detecting living organisms inside a vehicle, the breathing movements of the living organism to be detected are relatively slow, and the detection period takes a maximum of just under 10 seconds. In addition, living organism detection is required around the time when the vehicle doors are opened/closed or the locking operation is performed after the vehicle has stopped, and this timing overlaps with the UWB communication period for smart key operation, which is the main use of UWB communication. Therefore, performing living organism detection inside a vehicle using a UWB communication device may impair the usability (response, etc.) of smart key operation, and it is desirable to shorten the time required for living organism detection.

The object of the present invention is to provide a living body detection device, a living body detection method, and a living body detection program that can reduce the time required for living body detection.

The biological detection device according to the present invention comprises:
A living body detection device for performing living body detection,
an acquisition unit that acquires a detection signal from a sensor that detects a signal related to a living body's movement;
a calculation unit that integrates the magnitude of components included in a predetermined frequency band corresponding to the fluctuating motion of the detection signal from a start time point of the living body detection to a current time point, and calculates the integrated magnitude as a living body detection value;
an absence determination stopping unit that determines that a living body is not present when the integrated living body detection value becomes less than a first threshold value and stops the living body detection;
Equipped with.

The biological detection method according to the present invention comprises the steps of:
A method for performing live body detection, comprising:
A detection signal is obtained from a sensor that detects a signal related to a change in a living body movement;
integrating the magnitude of components included in a predetermined frequency band corresponding to the varying motion of the detection signal from the start time of the living body detection to the current time, to calculate a living body detection value;
When the accumulated living body detection value becomes less than a first threshold value, it is determined that a living body is not present, and the living body detection is stopped.

The biological detection program according to the present invention comprises:
A live body detection program for performing live body detection,
On the computer,
A process of acquiring a detection signal from a sensor that detects a signal related to a change in a living body movement;
A process of integrating the magnitude of components included in a predetermined frequency band corresponding to the fluctuating motion of the detection signal from a start time point of the living body detection to a current time point, and calculating the magnitude as a living body detection value;
a process of determining that a living body is not present when the integrated living body detection value becomes less than a first threshold value and stopping the living body detection;
Execute the command.

The present invention can reduce the time required for live body detection.

1 is a schematic diagram showing a vehicle equipped with a living body detection device according to an embodiment of the present invention. 2 is a block diagram showing an example of the biological detection device shown in FIG. 1 . 4 is a flowchart illustrating an example of a living body detection method in the living body detection device shown in FIG. 1 . 1 is a graph showing an example of a CIR data array. FIG. 13 is a diagram showing an example of a frequency analysis result of a CIR data sequence. 11 is a graph showing the relationship between the threshold value and the time transition of the maximum spectrum value calculated each time CIR data is acquired.

The following describes in detail the embodiment of the present invention with reference to the drawings.

[Body detection device]
Fig. 1 is a schematic diagram showing a vehicle 100 equipped with a UWB communication device 10 which is an example of a living body detection device according to the present embodiment. Fig. 2 is a block diagram showing an example of the UWB communication device 10.

The UWB communication device 10 is placed in the center of the interior of the vehicle 100, for example, on the ceiling. The UWB communication device 10 is basically used to operate the smart key of the vehicle 100, and performs UWB communication with a key terminal 20 carried by the user to lock and unlock the doors of the vehicle 100, start and stop the engine, and other operations without using a mechanical key.

In FIG. 1, an example is shown in which one UWB communication device 10 is installed in the center of the vehicle (on the ceiling) so that UWB communication can be properly performed throughout the vehicle and with the key terminal outside the vehicle, but the number and locations of the UWB communication devices 10 are not limited to the example shown in FIG. 1 and can be changed as appropriate.

After the vehicle 100 stops, the UWB communication device 10 starts UWB communication with the key terminal 20 carried by the user, and continuously measures the distance to the key terminal 20 based on the response time between the UWB communication device 10 and the key terminal 20. The UWB communication device 10 then detects that the key terminal 20 has moved a predetermined distance or more away from the vehicle 100 based on the results of the distance measurement with the key terminal 20 via UWB communication, and locks the doors of the vehicle 100 in response to the detection of the distance.

In this embodiment, such a UWB communication device 10 (sensor in the present invention) is used as a radar for detecting a detection target T, such as a living body inside the vehicle, for example, a child (infant) or a pet.

Specifically, after the doors of the vehicle 100 are locked, the UWB communication device 10 temporarily suspends UWB communication with the key terminal 20 and starts radar operation to detect whether a child, pet, etc. has been left inside the vehicle. Note that this operation to start radar operation is merely an example, and it may be started based on a locking operation by other means (manual locking, remote locking), etc.

In this way, the UWB communication device 10 that can be used as a radar has the configuration shown in Figure 2. Specifically, the UWB communication device 10 has at least a transmission/reception control unit 11, a transmission unit 12, a reception unit 13, an acquisition and storage unit 14, a frequency analysis unit 15, a living body absence determination unit 16, a living body presence determination unit 17, and an alarm output unit 18.

Although not shown, the UWB communication device 10 has a CPU (Central Processing Unit) as an arithmetic/control device, a ROM (Read Only Memory) as a main memory device, and a RAM (Random Access Memory), and functions as a so-called computer. The transmission/reception control unit 11, transmission unit 12, reception unit 13, acquisition and storage unit 14, frequency analysis unit 15, absence of living body determination unit 16, presence of living body determination unit 17, and alarm output unit 18 are configured so that the processing in each unit is executed by a circuit or program, and are controlled by the CPU.

The transmission/reception control unit 11 basically controls the transmission unit 12 and the reception unit 13 to perform UWB communication with the key terminal 20 and operate the smart key. Then, in response to the start operation of the radar operation described above, the transmission/reception control unit 11 controls the transmission unit 12 and the reception unit 13 to switch from UWB communication to an operation applied to radar operation and to perform living body detection by radar operation.

The transmitter 12 has a transmission antenna 12a. The transmitter 12 radiates, for example, a UWB pulse signal with a short pulse width using microwaves or the like, throughout the interior of the vehicle and outside the vehicle via the transmission antenna 12a. During radar operation, the transmitter 12 periodically radiates a UWB pulse signal throughout the interior of the vehicle and outside the vehicle via the transmission antenna 12a.

The receiver 13 has a receiving antenna 13a. The receiver 13 receives a pulse signal from the key terminal 20 via the receiving antenna 13a. In this embodiment, during radar operation, the receiver 13 periodically receives a reflected signal, which is a UWB pulse signal radiated from the transmitter 12 and reflected by the detection target, via the receiving antenna 13a. When a living body is present inside the vehicle, the receiver 13 receives a reflected signal from the living body (detection target) present around the UWB communication device 10, i.e., inside the vehicle.

During radar operation, the acquisition and storage unit 14 periodically acquires the reflected signal received by the receiver unit 13 as CIR (Channel Impulse Response) data in the form of a pair of distance and reflected signal strength, and stores the data in chronological order. When a detection target is detected, the CIR data contains, as the detection result, the distance to the detection target and the strength of the reflected signal from the detection target. The acquisition and storage unit 14 corresponds to the acquisition unit in the present invention. The CIR data is a detection signal related to the varying motion of a living body (here, breathing),

During radar operation, the frequency analysis unit 15 generates multiple CIR data from the start of biological detection to the current time (the time when the latest CIR data was acquired) as a CIR data array, and performs frequency analysis on the CIR data array for each CIR number. The CIR number is a parameter that corresponds to the distance from the UWB communication device 10.

The frequency analysis unit 15 then integrates the magnitude of components contained in a predetermined frequency band in the frequency analysis results of the CIR data array to calculate a biological detection value. The frequency analysis unit 15 uses, for example, a discrete Fourier transform as the frequency analysis. Furthermore, the frequency analysis unit 15 uses, for example, the breathing frequency band (0.16 Hz to 1.0 Hz) as the predetermined frequency band corresponding to the biological movement fluctuations. The frequency analysis unit 15 corresponds to the calculation unit in this invention.

The absence determining unit 16 determines that no living body is present in the vehicle when the accumulated living body detection value falls below an absence threshold _Tnp (a first threshold in the present invention), and stops the detection of the living body. The absence determining unit 16 corresponds to the absence determination stopping unit in the present invention. The absence threshold _Tnp will be described later with reference to FIG. 6.

The living body presence determination unit 17 determines that a living body is present in the vehicle when the integrated living body detection value becomes equal to or greater than a presence threshold T _pd (a second threshold in the present invention), and stops the living body detection. The living body presence determination unit 17 corresponds to the presence determination stopping unit in the present invention. The presence threshold T _pd will also be described later with reference to FIG. 6.

In this way, the absence/presence determining unit 16 and the presence determining unit 17 determine the presence or absence of a living body based on the accumulated living body detection value and stop the living body detection. After the living body detection stops, that is, after the radar operation of the UWB communication device 10 stops, the UWB communication device 10 resumes UWB communication with the key terminal 20.

Furthermore, as described in FIG. 3 below, the frequency analysis unit 15, the absence of living body determination unit 16, and the presence of living body determination unit 17 perform frequency analysis each time the latest CIR data is acquired, calculate an integrated living body detection value, and monitor the time variation of the living body detection value (compared with the above threshold value). Therefore, the determination time for living body detection can be shortened to stop living body detection, and living body detection can be performed by the UWB communication device 10 without impairing the usability of other operations (smart key operations) using the UWB communication device 10.

When it is determined that a living organism is present inside the vehicle, the alarm output unit 18 outputs an alarm to notify people around the vehicle 100 that a living organism is present inside the vehicle. For example, when it is determined that a child, pet, etc. has been left behind inside the vehicle, the alarm output unit 18 uses the lights (e.g., headlights, etc.) of the vehicle 100 to output an alarm by flashing the lights, etc. to notify people around the vehicle 100 that the child or pet has been left behind. The alarm output unit 18 may also use a sound output device (e.g., a horn, speaker, etc.) to output an alarm by sound or voice from the sound output device to notify people around the vehicle 100 that the child or pet has been left behind.

[Living body detection method]
The above-mentioned living body detection method in the UWB communication device 10 will be described with reference to Fig. 3. Fig. 3 is a flow chart illustrating an example of the living body detection method in the UWB communication device 10. The living body detection method is executed by, for example, a living body detection program.

In the living body detection method, for example, as described above, after the doors of the vehicle 100 are locked, living body detection is started by radar operation using the UWB communication device 10.

(Step S11)
The UWB communication device 10 acquires a reflected signal of a radio wave (UWB pulse signal) as CIR data. Specifically, the UWB communication device 10 radiates a UWB pulse signal to the entire interior of the vehicle and to the outside of the vehicle using the transmission unit 12, receives a reflected signal that reflects the UWB pulse signal using the reception unit 13, and acquires the reflected signal received by the reception unit 13 as CIR data using the acquisition and storage unit 14.

(Step S12)
The UWB communication device 10 generates, by the frequency analysis unit 15, a plurality of CIR data from the start of the live body detection to the current time (the time when the latest CIR data is acquired) as a CIR data array.

Figure 4 is a graph showing an example of a CIR data array. Figure 4 shows a nine-second CIR data array obtained by a UWB communication device 10 operating as a radar when a breathing dummy simulating a living body is placed inside a vehicle.

In the graph shown in Figure 4, a periodic fluctuation in the detection level, that is, a peak accompanied by a fluctuation indicating breathing, occurs around CIR number 7, which corresponds to the distance at which the dummy was placed, and it can be seen that the presence of the dummy was detected.

(Step S13)
The UWB communication device 10 performs frequency analysis for each CIR number on the generated CIR data sequence by the frequency analysis unit 15, and obtains, as the frequency analysis result, an integrated value obtained by integrating the detection levels for each CIR number and each frequency. The frequency analysis unit 15 uses, for example, a discrete Fourier transform as the frequency analysis.

(Step S14)
The UWB communication device 10 obtains a maximum spectrum value _Pmax within the range of the respiration frequency band and the range of the CIR number corresponding to the distance within the vehicle interior in the frequency analysis result obtained by the frequency analysis unit 15. The maximum spectrum value _Pmax is a living body detection value calculated by integrating the magnitude of the components included in the respiration frequency band in the CIR data sequence, that is, in a plurality of CIR data from the start time to the current time.

Figure 5 shows an example of the frequency analysis result of a CIR data array. Figure 5 shows the frequency analysis result obtained by frequency analyzing the CIR data array shown in Figure 4, and the frequency analysis result is shown in heat map format.

The frequency band range of respiration is 0.16 Hz to 1.0 Hz, and in Fig. 5, the range of CIR numbers corresponding to the distance within the vehicle is 1 to 12. In Fig. 5, the maximum spectrum value P _max in these two ranges is the spectrum value of the frequency 0.34 Hz and CIR number 7.

Note that, here, the above-mentioned maximum spectral value _Pmax is obtained as the living body detection value. However, instead of the maximum spectral value _Pmax , for example, the total sum of spectral values included in the range of the respiration frequency band may be used.

(Step S15)
The UWB communication device 10 obtains an absence threshold T _np corresponding to the number of times the CIR data is obtained. For example, the UWB communication device 10 stores an absence threshold T np (see FIG. 6 described later) corresponding to the number of times the CIR data is obtained in a main storage device such as a ROM, and obtains the absence threshold T _np from the main storage device such as a ROM when using the absence threshold T _np .

(Step S16)
The UWB communication device 10 uses the absence-of-living-person determining unit 16 to determine whether or not a living person is present inside the vehicle. Specifically, it determines whether or not the maximum spectrum value P _max is less than the absence threshold value T _np . If the maximum spectrum value P _max is less than the absence threshold value T _np and it is determined that a living person is present inside the vehicle (YES), the process proceeds to step S19. On the other hand, if the maximum spectrum value P _max ≧the absence threshold value T _np and it is not possible to determine that a living person is present inside the vehicle (NO), the process proceeds to step S17.

(Step S17)
The UWB communication device 10 uses the living body presence determination unit 17 to determine whether or not a living body is present inside the vehicle. Specifically, it determines whether or not the maximum spectrum value P _max is equal to or greater than the presence threshold value T _pd . If the maximum spectrum value P _max is equal to or greater than the presence threshold value T _pd and it is determined that a living body is present inside the vehicle (YES), the process proceeds to step S18. On the other hand, if the maximum spectrum value P _max is less than the presence threshold value T _pd and it is not determined that a living body is present inside the vehicle (NO), the process returns to step S11.

The UWB communication device 10 repeats steps S11 to S17 until it determines that a living body is not present in the vehicle or that a living body is present in the vehicle within a time limit described below. Each time steps S11 to S17 are repeated, frequency analysis is performed on the CIR data sequence, including the newly acquired CIR data, and the magnitude of the components included in the frequency band of breathing in the frequency analysis result is further integrated to calculate a living body detection value.

Fig. 6 is a graph showing the relationship between the maximum spectrum value _Pmax calculated each time CIR data is acquired and the absence threshold _Tnp and the presence threshold _Tpd over time. In Fig. 6, the maximum spectrum value _Pmax when no living body is present is shown by a solid line, and the maximum spectrum value _Pmax when a living body is present is shown by a dashed line. The absence threshold _Tnp is shown by a dashed line, and the presence threshold _Tpd is shown by a dashed line.

6, the presence threshold T _pd is constant during the detection of a living body, whereas the absence threshold T _np is changed over time during the detection of a living body.

Specifically, the absence threshold T _np is set to 0 from the start point until a predetermined time point that is shorter than the time limit (here, as an example, 9 seconds) and is smaller than the presence threshold T _pd . Also, the absence threshold T _np has a characteristic of increasing over time so as to be equal to the presence threshold T _pd at the time of the time limit, so that the presence or absence of a living body is determined within the time limit.

In order to reliably determine that a living body is not present, the maximum spectrum value _Pmax accumulated over a certain period of time is evaluated. For this reason, the above-mentioned predetermined period of time is set, and the absence threshold value _Tnp is set to 0 from the start point to the above-mentioned predetermined period of time. After the above-mentioned predetermined period of time has elapsed, the absence threshold value _Tnp is set to increase with the passage of time.

In FIG. 6, after the above-mentioned specified time has elapsed, the slope of the graph of the absence threshold T _np is constant and the graph is a straight line, but the absence threshold T _np may be increased so that the graph of the absence threshold T _np increases in a curved manner.

In Fig. 6, the dashed line shows an example of the time transition of the maximum spectrum value _Pmax when the above-mentioned dummy is placed inside the vehicle. The maximum spectrum value _Pmax is integrated as the time of the living body detection elapses, so as shown by the dashed line, it increases with time, but the rate of increase is greater than when no living body is present inside the vehicle (solid line). When the maximum spectrum value _Pmax becomes equal to or greater than the presence threshold value _Tpd , the UWB communication device 10 determines that a living body is present inside the vehicle and stops the living body detection operation (radar operation) as described below.

The presence threshold T _pd is set so that the maximum spectrum value P _max in the case where a living body is present becomes equal to or greater than the presence threshold T _pd before the time limit.

6, the solid line shows an example of the time transition of the maximum spectrum value _Pmax when no living body is present in the vehicle. In this case, the maximum spectrum value _Pmax is also integrated as time passes during the detection of a living body, so as shown by the solid line, it increases over time, but the rate of increase is smaller and it increases gradually compared to when a living body is present in the vehicle (dashed line). Then, when the maximum spectrum value _Pmax falls below the absence threshold _Tnp , the UWB communication device 10 determines that no living body is present in the vehicle, and stops the operation of detecting a living body (radar operation) as described later.

The absence threshold T _np is set so that the maximum spectrum value P _max in the absence of a living body becomes less than the absence threshold T _np before the time limit.

(Step S18)
The UWB communication device 10 determines that a living body is present inside the vehicle by the living body presence determination unit 17. In this case, the UWB communication device 10 outputs an alarm by the alarm output unit 18 to notify people around the vehicle 100 that a living body is present inside the vehicle, as described with reference to FIG.

(Step S19)
The UWB communication device 10 determines by the non-existence determining unit 16 that no living body is present inside the vehicle.

(Step S20)
The UWB communication device 10 ends the living body detection and transitions to a state where smart key operation is possible. In this way, as soon as the UWB communication device 10 determines the absence or presence of a living body, it ends the living body detection (radar operation), and then resumes UWB communication with the key terminal 20, transitioning to a state where smart key operation is possible.

If it is only necessary to detect the presence of a living body, the judgment process using the presence threshold T _pd is sufficient. Normally, in a living body detection for detecting the presence of a living body in a vehicle, the conventional UWB communication device continues the radar operation until the time limit is reached in vain, since the detection detects the presence of a living body in the vehicle. In this way, the radar operation period extended to the time limit may hinder the communication with the key terminal, which is the main purpose of the UWB communication device, and the vehicle operation executed accordingly (detection of the reapproach of the key terminal and the unlocking operation associated with it).

Therefore, in this embodiment, by performing a determination process to detect the absence of a living body using the absence threshold value T _np , the living body detection does not extend to the time limit, and the time required for the living body detection can be shortened. Therefore, the possibility of interfering with the communication between the UWB communication device 10 and the key terminal 20 can be reduced. In addition, when a living body is not present in the vehicle, the radar operation for the living body detection stops early, which contributes to reducing the power consumption of the UWB communication device 10.

The above describes an embodiment of the present invention. Note that the above description is an example of a preferred embodiment of the present invention, and the scope of the present invention is not limited to this. In other words, the description of the configuration of the above device and the shape of each part are examples, and it is clear that various modifications and additions to these examples are possible within the scope of the present invention.

For example, in this embodiment, the UWB communication device 10 is used as a radar (sensor) to detect a living body, but determining that no living body is present and stopping the living body detection operation early can also be applied to other detection devices. For example, it can also be applied to detection devices such as pressure sensors and ultrasonic sensors built into the seats of vehicles.

This invention is useful for live body detection using a vehicle's communication device.

REFERENCE SIGNS LIST 10 UWB communication device 11 Transmission/reception control unit 12 Transmission unit 13 Reception unit 14 Acquisition/storage unit 15 Frequency analysis unit 16 Absence of living body determination unit 17 Presence of living body determination unit 18 Alarm output unit 20 Key terminal 100 Vehicle

Claims (8)

A living body detection device for performing living body detection,
an acquisition unit that acquires a detection signal from a sensor that detects a signal related to a living body's movement;
a calculation unit that integrates the magnitude of components included in a predetermined frequency band corresponding to the fluctuating motion of the detection signal from a start time point of the living body detection to a current time point, and calculates the integrated magnitude as a living body detection value;
an absence determination stopping unit that determines that a living body is not present when the integrated living body detection value becomes less than a first threshold value and stops the living body detection;
A biological detection device comprising: a presence determination stopping unit that determines that a living body is present when the integrated living body detection value becomes equal to or greater than a second threshold value and stops the living body detection;
The biological detection device according to claim 1 . the first threshold is smaller than the second threshold at the start time point, and increases over time to be equal to the second threshold at the time point of the limit time for the live body detection;
The biological detection device according to claim 2 . The first threshold value is set to 0 from the start time point until a predetermined time point that is shorter than the time limit.
The biological detection device according to claim 3 . The sensor is configured to function as a radar using a microwave communication device.
The biological detection device according to claim 1 . The communication device is a UWB (Ultra-Wide Band) communication device.
The biological detection device according to claim 5 . A method for performing live body detection, comprising:
A detection signal is obtained from a sensor that detects a signal related to a change in a living body movement;
integrating the magnitude of components included in a predetermined frequency band corresponding to the varying motion of the detection signal from the start time of the living body detection to the current time, to calculate a living body detection value;
When the integrated living body detection value becomes less than a first threshold value, it is determined that a living body is not present, and the living body detection is stopped.
Liveness detection methods. A live body detection program for performing live body detection,
On the computer,
A process of acquiring a detection signal from a sensor that detects a signal related to a living body's fluctuating movement;
A process of integrating the magnitude of components included in a predetermined frequency band corresponding to the fluctuating motion of the detection signal from a start time point of the living body detection to a current time point, and calculating the magnitude of the components as a living body detection value;
a process of determining that a living body is not present when the integrated living body detection value becomes less than a first threshold value and stopping the living body detection;
A live detection program that executes the following:

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