JP7099665B2 - Electrocardiographic detector for vehicles - Google Patents

Description

The present invention relates to a vehicle electrocardiographic detection device mounted on a vehicle and detecting an electrocardiographic waveform of an occupant.

A technique is known in which electrodes are provided on a steering wheel or a vehicle seat to detect an electrocardiographic waveform of an occupant.

For example, in Patent Document 1, the electrocardiographic signal of a seated person sitting on a vehicle seat is measured, and RRI, which is the interval of output peaks extracted as R wave from the measured electrocardiographic signal, is calculated and electrocardiographic. The absolute value of the difference of continuous RRI in the issue is calculated, the average value of the absolute value of the difference of continuous RRI in the target section is divided by the average value of RRI in the target section, and the first evaluation value is calculated. A occupant state determination device for determining the reliability of an electrocardiographic signal measured in a target section based on a comparison result between an evaluation value and a first threshold has been proposed.

JP-A-2017-205249

However, since the inclination of the heart differs depending on the person, the R wave of the electrocardiographic waveform detected may be small depending on the arrangement of the electrodes, and it may be difficult to detect the R wave. Since the technique of Patent Document 1 does not consider the inclination of the heart, which varies from person to person, it may be difficult to detect the R wave, and there is room for improvement.

The present invention has been made in consideration of the above facts, and an object of the present invention is to provide an electrocardiographic detection device for vehicles capable of detecting an R wave in consideration of the inclination of the heart.

In order to achieve the above object, the first aspect is a contact electrode provided at a portion in contact with the occupant, and a seat electrode provided on the vehicle seat on the lower side of the vehicle from the position of the contact electrode and the occupant's heart. Two electrodes of the detection unit that detects the differential voltage of the two inputs, the contact electrode, the sheet electrode, and the contact electrode and the virtual electrode that can be generated from the sheet electrode are used as the inputs of the detection unit. Includes a switching unit that selectively switches and connects.

According to the first aspect, the contact electrode is provided at a position in contact with the occupant, and the seat electrode is provided on the vehicle seat below the position of the contact electrode and the occupant's heart.

The detection unit detects the differential voltage of the two inputs. Then, in the switching unit, two of the contact electrode, the sheet electrode, and the contact electrode and the virtual electrode that can be generated from the sheet electrode are selectively switched and connected as the input of the detection unit. As a result, by switching the switching unit to a combination having a higher signal strength of the detection unit, it is possible to select a combination of electrodes according to the inclination of the heart for each occupant and generate an electrocardiographic waveform. Therefore, it is possible to detect the R wave in consideration of the inclination of the heart.

Of the contact electrode, sheet electrode, and virtual electrode, the strength of the differential voltage detected by the detection unit is sequentially switched by sequentially switching the combination of two predetermined electrodes capable of generating the second induction waveform of the electrocardiographic waveform. It may be in the form of further including a control unit that controls the switching unit so as to select the combination of electrodes that maximizes the value.

Further, the contact electrode has a pair of left and right electrodes provided at positions corresponding to the left and right of the occupant, and the combination of the two predetermined electrodes is a combination of one left and right electrode and a sheet electrode, and a pair of left and right electrodes. The combination of the first virtual electrode generated from and the second virtual electrode generated from the other left and right electrodes and the sheet electrode, the combination of one left and right electrode and the third virtual electrode generated from one left and right electrode and the sheet electrode, the third virtual Five combinations of the combination of the electrode and one of the left and right electrodes, and the combination of the first virtual electrode and the sheet electrode may be applied.

Further, the identification unit for identifying the occupant is further included, and the control unit registers in advance the combination of electrodes having the maximum differential voltage intensity for each occupant, and the combination of electrodes corresponding to the occupant identified by the identification unit. The switching unit may be controlled so as to switch to.

As described above, according to the present invention, there is an effect that it is possible to provide an electrocardiographic detection device for vehicles capable of detecting an R wave in consideration of the inclination of the heart.

It is a figure which shows the schematic structure of the electrocardiographic detection apparatus for vehicles which concerns on this embodiment. It is a figure for demonstrating an example of an electrocardiographic waveform. It is a figure for demonstrating an example of the measuring method of the 2nd lead. It is a figure which shows an example of the R wave in the case of a general heart inclination and the R wave in the case of an uncommon heart inclination. It is a figure for demonstrating the combination of a virtual electrode and an electrode. It is a block diagram which shows the structure of the electrocardiographic waveform generator which concerns on this embodiment. It is a flowchart which shows an example of the flow of the process performed in the control part of the electrocardiographic detection apparatus for vehicles which concerns on this embodiment. It is a flowchart which shows the modification of the flow of the process performed in the control part of the electrocardiographic detection apparatus for vehicles which concerns on this embodiment.

Hereinafter, an example of an electrocardiographic detection device for a vehicle according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an electrocardiographic detection device for a vehicle according to the present embodiment.

The vehicle electrocardiographic detection device 10 according to the present embodiment includes an electrocardiographic waveform generator 12, seat back electrodes 16A and 16B as contact electrodes, and seat cushion electrodes 18A and 18B as seat electrodes.

The seat back electrodes 16A and 16B are provided on the seat back 20A of the vehicle seat 20 in contact with the occupant, and are provided in pairs corresponding to the left and right of the seated occupant. That is, one seat back electrode 16A is provided in the region corresponding to the left side of the occupant, and the other seat back electrode 16B is provided in the region corresponding to the right side of the occupant.

When the occupant sits on the vehicle seat 20, the occupant's back is brought close to the seat back electrodes 16A and 16B, and a capacitive coupling occurs between the occupant's back and the seat back electrodes 16A and 16B to form a capacitor. Further, the seatback electrodes 16A and 16B are electrically connected to the electrocardiographic waveform generator 12, and the electrocardiographic waveform generator 12 is connected to the seatback electrodes 16A and 16B by ions associated with electrical activity in the heartbeat of the heart. The current change (alternating current) is detected as a current signal.

A pair of seat cushion electrodes 18A and 18B are provided on the seat back electrodes 16A and 16B and the seat cushion 20B on the lower side of the vehicle from the position of the occupant's heart, and are covered with a seat cover (not shown). The seat cushion electrodes 18A and 18B are close to the occupant's buttocks via the occupant's clothes and the seat cover when the occupant sits on the vehicle seat 20. One seat cushion electrode 18B is connected to the electrocardiographic waveform generator 12, and the other seat cushion electrode 18A is grounded. Note that FIG. 1 shows an example in which the seat cushion electrodes 18A and 18B are arranged in the width direction of the vehicle (left and right of the occupant), but the arrangement is not limited to this. For example, the seat cushion electrodes 18A and 18B may be arranged in the front-rear direction of the vehicle (front and rear of the occupant). Alternatively, the seat cushion electrodes 18A and 18B may be arranged in other directions. Further, the seat cushion electrodes 18A and 18B may be provided at positions other than the seat cushion 20B of the vehicle seat 20. For example, the seat back 20A of the vehicle seat 20 may be provided below the seat back electrodes 16A and 16B.

The electrocardiographic waveform generator 12 generates an electrocardiographic waveform of an occupant based on the current signals input from the seat back electrodes 16A and 16B and the seat cushion electrode 18B.

By the way, as the electrocardiographic waveform, as shown in FIG. 2, the first lead waveform, the second lead waveform, the third lead waveform, the aVR lead waveform, the aVL lead waveform, the aVF lead waveform and the like are generally known. There is. The first lead waveform is a lead waveform that looks at the side wall of the left ventricle of the heart, the second lead waveform is a lead waveform that looks at the heart from the apex of the heart, and the third lead waveform is the side surface of the right ventricle and the lower wall of the left ventricle. It is an induction waveform to see. The aVR lead waveform is a lead waveform for viewing the heart from the right shoulder, the aVL lead waveform is a lead waveform for viewing the heart from the left shoulder, and the aVF lead waveform is a lead waveform for viewing the heart from substantially directly below.

The electrocardiographic waveform is a record of the flow of electricity in the heart. For example, if two electrodes are attached across the heart, one electrocardiographic waveform can be obtained. The heart is located slightly to the left of the center of the chest and is tilted sideways with the apex of the heart down. Electricity in the heart flows from the sinus node located in the upper right atrium to the lower apex of the ventricle via the atrioventricular node located almost in the center, so that the electrical axis is diagonally downward to the left. When the negative electrode and the positive electrode are attached in order in the same direction as this direction, the electrocardiographic waveform becomes upward, and when the negative electrode and the positive electrode are reversed, the electrocardiographic waveform becomes downward.

In the limb bipolar induction of medical electrocardiogram, electrodes are connected to both feet and both hands, and the potential difference between each electrode is monitored. The space between the left hand and the right hand is called the first lead, the space between the right hand and the left foot is called the second lead, and the space between the right foot and the left hand is called the third lead.

Further, the electrocardiographic waveform includes a P wave, a Q wave, an R wave, an S wave, and a T wave, and the legibility (magnitude, etc.) of each of the PQRST waves of the electrocardiographic waveform is different for each induction. It is often used to calculate the heart rate, and although there are individual differences, it is said that the second lead is the easiest to see for the R wave, and the action potential due to depolarization of the ventricular muscle cells that generate the R wave is the tilt direction of the heart (second lead). The most appropriate measurement of potential difference is.

In the present embodiment, when measuring the second lead, for example, as shown in FIG. 3, the seat back electrode 16A is connected to the − terminal of the differential amplifier 22, and the seat cushion electrode 18B is connected to the + terminal of the differential amplifier 22. By connecting to the terminal, measurement becomes possible.

However, since the inclination of the heart differs depending on the person, the R wave that can be confirmed by the second lead may be small. For example, as shown in FIG. 4, the R wave detected in the case of an uncommon heart tilt may be smaller than the R wave detected in the case of a general heart tilt (50 °). When the R wave is small, it is difficult to detect the R wave under the in-vehicle condition where the noise is larger than that of the medical electrocardiogram.

Therefore, in the present embodiment, bipolar induction is realized by using the seat back electrodes 16A and 16B, the seat cushion electrodes 18B, and virtual electrodes that can be generated from two or more electrodes, according to the inclination of each person's heart. Select the combination of electrodes to generate an electrocardiographic waveform.

Here, the virtual electrode is referred to as a virtual electrode because the synthesis of the potentials of two or more electrodes is equal to the potential of the midpoint position between the electrodes. For example, in the present embodiment, as shown in FIG. 5, when the seat back electrode 16A is the electrode A, the seat back electrode 16B is the electrode B, and the seat cushion electrode 18B is the electrode C, the following three virtual electrodes can be generated. be. The three virtual electrodes are the virtual electrode (A + B) at the midpoint position between the electrodes A and B, the virtual electrode (A + C) at the midpoint position between the electrodes A and C, and the space between the electrodes B and C. There is a virtual electrode (B + C) at the midpoint position.

Then, in the present embodiment, by combining these electrodes and inputting them to the differential amplifier 22, it is possible to generate an electrocardiographic waveform that matches the inclination of the heart. As the combination of electrodes, a combination capable of generating a second lead waveform is selected and input to the differential amplifier 22. Specifically, as shown in FIG. 5, five types of vectors (a combination of electrodes) of (A + B, B + C), (A, A + C), (A, C), (A + C, C), and (A + B, C) ), Select a combination of electrodes that can easily detect the R wave. Since the combination of (A, B) between the seat back electrodes 16A and 16B is closer to the first lead waveform, it is excluded from the combination of electrodes in this embodiment, but the combination of (A, B) is used above. There may be 6 ways including this.

Next, a specific configuration example of the electrocardiographic waveform generator 12 will be described. FIG. 6 is a block diagram showing the configuration of the electrocardiographic waveform generator 12 according to the present embodiment.

The electrocardiographic waveform generator 12 includes a switching unit 14, a differential amplifier 22 as a detection unit, an ADC (Analog to Digital Converter) 28, and a control unit 30.

A seat back electrode 16A, a seat back electrode 16B, a seat cushion electrode 18B, and the above-mentioned three virtual electrodes are connected to the input side, and a differential amplifier 22 is connected to the output side.

Specifically, the switching unit 14 includes an A electrode terminal, an A + B electrode terminal, a B electrode terminal, a B + C electrode terminal, a C electrode terminal, and an A + C electrode terminal as input terminals, and the output terminal is an output terminal. It is connected to each of the + terminal and the-terminal of the differential amplifier 22.

The terminal for the A electrode is connected to the seat back electrode 16A, and the seat back electrode (electrode A) 16A can be connected to the differential amplifier 22 by switching the connection of the switching unit 14.

The terminal for the A + B electrode is connected to a virtual electrode (A + B) generated by being connected to each of the seat back electrode 16A and the seat back electrode 16B via a resistor. The resistance is a resistance value that cancels out the difference between the capacitance of the actual electrodes (seat back electrodes 16A and 16B and the seat cushion electrode 18B) and the capacitance of the virtual electrode (A + B). By switching the connection of the switching unit 14, the virtual electrode (A + B) can be connected to the differential amplifier 22.

The B electrode terminal is connected to the seat back electrode 16B, and the seat back electrode (electrode B) 16B can be connected to the differential amplifier 22 by switching the connection of the switching unit 14.

The B + C electrode terminal is connected to a virtual electrode (B + C) generated by being connected to each of the seat back electrode 16B and the seat cushion electrode 18B via a resistor. The resistance is a resistance value that cancels out the difference between the capacitance of the actual electrodes (seat back electrodes 16A and 16B and the seat cushion electrode 18B) and the capacitance of the virtual electrode (A + C). By switching the connection of the switching unit 14, the virtual electrode (B + C) can be connected to the differential amplifier 22.

The C electrode terminal is connected to the seat cushion electrode 18B, and the seat cushion electrode (electrode C) 18B can be connected to the differential amplifier 22 by switching the connection of the switching unit 14.

The terminal for the A + C electrode is connected to a virtual electrode (A + C) generated by being connected to each of the seat back electrode 16A and the seat cushion electrode 18B via a resistor. The resistance is a resistance value that cancels out the difference between the capacitance of the actual electrodes (seat back electrodes 16A and 16B and the seat cushion electrode 18B) and the capacitance of the virtual electrode (A + C). By switching the connection of the switching unit 14, the virtual electrode (A + C) can be connected to the differential amplifier 22.

The switching unit 14 can be switched to the above-mentioned five types of vectors (combination of electrodes) according to an instruction from the control unit 30.

The differential amplifier 22 detects the differential voltage of the electrodes connected to the two input terminals and outputs the differential voltage to the ADC 28. Specifically, the differential amplifier 22 amplifies the difference between the two input signals from the electrodes connected to the two input terminals with a constant coefficient.

The ADC 28 converts an analog electric signal obtained from the differential amplifier 22 into a digital signal and outputs it to the control unit 30.

The control unit 30 is composed of a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a non-volatile memory such as a flash memory. The CPU controls the switching unit 14 by executing a program stored in the memory in advance to selectively switch the electrodes connected to the input terminals of the differential amplifier 22 and generate an electrocardiographic waveform. And output. Specifically, the control unit 30 sequentially switches to the above-mentioned five combinations of electrodes, and controls to switch to the connection having the highest S / N ratio as the signal strength. Specifically, since the waveform corresponding to the electrocardiographic waveform output from the differential amplifier 22 includes an R wave (maximum peak value) and an S wave (minimum peak value), the control unit 30 sets the S / N ratio. Control is performed to search for and switch the combination of electrodes having the maximum potential difference of the RS wave.

Subsequently, specific processing performed by the control unit 30 of the vehicle electrocardiographic detection device 10 according to the present embodiment configured as described above will be described. FIG. 7 is a flowchart showing an example of the flow of processing performed by the control unit 30 of the vehicle electrocardiographic detection device 10 according to the present embodiment. The process of FIG. 7 may be started, for example, when an ignition switch (not shown) is turned on, or when an instruction indicating the start of detection of an electrocardiographic waveform is given to the control unit 30. good.

In step 100, the control unit 30 switches the switching unit 14 and proceeds to step 102. The switching unit 14 is switched so as to be one electrode combination from the above-mentioned five electrode combinations.

In step 102, the control unit 30 acquires the differential amplification result by the differential amplifier 22 and proceeds to step 104.

In step 104, the control unit 30 determines whether or not all the switching of the electrode combination by the switching unit 14 has been completed. In the determination, it is determined whether or not the differential amplification result is obtained by switching to the combination of all the above five electrodes. If the determination is denied, the process returns to step 100, the above processing is repeated, the switching of the switching unit 14 is changed to obtain the differential amplification result, and if the determination is affirmed, step 106. Move to.

In step 106, the control unit 30 performs connection switching by the switching unit 14 to end a series of processes. That is, the control unit 30 identifies the combination of the electrodes having the largest S / N ratio among the differential amplification results obtained by switching to all the combinations of electrodes, and switches the switching unit 14 so as to have the combination. The control unit 30 controls. This makes it possible to generate an electrocardiographic waveform by selecting a combination of electrodes according to the inclination of each person's heart.

By the way, in the process of FIG. 7 above, it is necessary to search for an appropriate electrode combination each time the occupant sits down, and it takes time to search for the electrode combination, so that the time for detecting the electrocardiographic waveform is shortened. There is room for improvement.

Therefore, the control unit 30 may register the combination of electrodes for each occupant in advance, identify the occupant, and control the switching unit 14. Hereinafter, a process of registering a combination of electrodes for each occupant and a process of identifying the occupant and controlling the switching unit 14 will be described with respect to the process of FIG. 7.

FIG. 8 is a flowchart showing a modified example of the flow of processing performed by the control unit 30 of the vehicle electrocardiographic detection device 10 according to the present embodiment. The process of FIG. 8 is started when, for example, an instruction indicating the start of detection of an electrocardiographic waveform or an instruction to register an occupant is given to the control unit 30. Further, the same processing as that in FIG. 7 will be described with the same reference numerals.

In step 96, the control unit 30 determines whether or not the occupant is registered. In the determination, for example, it is determined whether or not an operation for instructing registration has been performed by providing an operation unit or the like for instructing registration. If the determination is affirmed, the process proceeds to step 98, and if the determination is negative, the process proceeds to step 108.

In step 98, the control unit 30 identifies and registers the occupant, and proceeds to step 100. For example, there is a method of identifying an occupant by providing a plurality of switches and switching the switch for each occupant. In this case, an instruction is given to assign an occupant to the switch. In addition, when performing biometric authentication such as a photographed image of a camera or a fingerprint or a face, a photographed image of an occupant and biometric information are registered.

In step 100, the control unit 30 switches the switching unit 14 and proceeds to step 102. The switching unit 14 is switched so as to be one electrode combination from the above-mentioned five electrode combinations.

In step 102, the control unit 30 acquires the differential amplification result by the differential amplifier 22 and proceeds to step 104.

In step 104, the control unit 30 determines whether or not all the switching of the electrode combination by the switching unit 14 has been completed. In the determination, it is determined whether or not the differential amplification result is obtained by switching to the combination of all the above five electrodes. If the determination is denied, the process returns to step 100, the above processing is repeated, the switching of the switching unit 14 is changed to obtain the differential amplification result, and if the determination is affirmed, step 105. Move to.

In step 105, the control unit 30 registers the switching state of the switching unit 14 in association with the occupant and ends a series of processes. That is, the control unit 30 identifies the combination of the electrodes having the largest S / N ratio among the differential amplification results obtained by switching to all the combinations of electrodes, and stores the switching state of the combination in association with the occupant. do.

On the other hand, in step 108, the control unit 30 identifies the occupant and proceeds to step 110. For the identification of the occupant, for example, a plurality of switches corresponding to the occupant may be provided to identify the occupant from the operating state of each switch. Alternatively, a camera for photographing the occupant may be provided in the vehicle interior to identify the occupant registered in advance from the photographed image of the camera. Alternatively, a biometric authentication unit that performs biometric authentication such as a fingerprint or a face may be provided to identify a pre-registered occupant.

In step 110, the control unit 30 switches to the switching state of the switching unit 14 corresponding to the identified occupant, that is, the switching state for each occupant registered in advance by the processing of steps 98 to 105, and ends a series of processing. In FIG. 8, the process when the registered occupant does not exist is omitted, but when the occupant is not registered when the occupant is identified in the registered step 108, the above-mentioned FIG. 7 shows. The processing of steps 100 to 106 may be performed.

By performing the processing in this way, it becomes possible to recognize the occupant and select a combination of electrodes according to the inclination of the heart for each occupant to generate an electrocardiographic waveform.

In the above embodiment, an example including two seat cushion electrodes 18A and 18B has been described, but the present invention is not limited to this, and the grounded seat cushion electrode 18A may be omitted. Although noise can be suppressed by the grounded seat cushion electrode 18A, it is possible to generate an electrocardiographic waveform even if the seat cushion electrode 18A is omitted.

Further, in the above embodiment, the seat back electrodes 16A and 16B have been described as an example as a pair of left and right electrodes provided corresponding to the left and right of the occupant, but the left and right electrodes are not limited to this. For example, a pair of electrodes may be provided on the steering wheel to serve as left and right electrodes. Further, it may be in the form of having only one of the seat back electrodes of the pair of electrodes 16A and 16B. In this case, of the seat back electrode, the seat cushion electrode 18B, and the virtual electrode generated from the seat back electrode and the seat cushion electrode 18B, two electrodes may be selectively switched by the switching unit 14.

Further, in the above embodiment, an example in which a virtual electrode is generated by two of the three electrodes has been described, but the present invention is not limited to this. For example, a virtual electrode may be generated using three or more electrodes. Further, electrodes other than the seat back electrodes 16A and 16B and the seat cushion electrodes 18A and 18B are further provided so that virtual electrodes other than those described in the above embodiment can be generated, and the input is selectively switched to the differential amplifier 22. It may be possible.

Further, the processing performed by the control unit 30 in the above embodiment has been described as software processing, but the processing is not limited to this. For example, it may be a process performed by hardware, or it may be a process in which both hardware and software are combined.

Further, the process performed by the control unit 30 in the above embodiment may be stored in a storage medium as a program and distributed.

Further, the present invention is not limited to the above, and it is needless to say that the present invention can be variously modified and implemented within a range not deviating from the gist thereof.

10 ... Vehicle electrocardiographic detector, 12 ... Electrocardiographic waveform generator, 14 ... Switching unit, 16A ... Seat back electrode, 16B ... Seat back electrode, 18B ... Seat cushion electrode , 20 ... Vehicle seat, 20A ... Seat back, 20B ... Seat cushion, 22 ... Differential amplifier, 30 ... Control unit

Claims (4)

The contact electrodes provided at the parts that come into contact with the occupants,
The contact electrode, the seat electrode provided on the vehicle seat on the lower side of the vehicle from the position of the occupant's heart, and the seat electrode.
A detector that detects the differential voltage of the two inputs,
A switching unit that selectively switches and connects two of the contact electrode, the sheet electrode, and the contact electrode and the virtual electrode that can be generated from the sheet electrode as inputs of the detection unit.
For vehicle electrocardiographic detectors including. The differential detected by the detection unit by sequentially switching the combination of two predetermined electrodes capable of generating the second induction waveform of the electrocardiographic waveform among the contact electrode, the sheet electrode, and the virtual electrode. The vehicle electrocardiographic detection device according to claim 1, further comprising a control unit that controls the switching unit so as to select the combination of electrodes that maximizes the voltage intensity. The contact electrode has a pair of left and right electrodes provided at positions corresponding to the left and right of the occupant.
The combination of the two predetermined electrodes is a combination of one of the left and right electrodes and the sheet electrode, a first virtual electrode generated from the pair of left and right electrodes, and a second generated from the other left and right electrodes and the sheet electrode. A combination of virtual electrodes, a combination of one left and right electrode, one left and right electrode, and a third virtual electrode generated from the sheet electrode, a combination of the third virtual electrode and one left and right electrode, and the first virtual electrode. The electrocardiographic detection device for a vehicle according to claim 2, which is a combination of the above and the seat electrodes in five ways. Including an identification unit that identifies the occupant,
The control unit controls the switching unit so as to register in advance the combination of electrodes having the maximum differential voltage intensity for each occupant and switch to the combination of electrodes corresponding to the occupant identified by the identification unit. The vehicle electrocardiographic detection device according to claim 2 or 3.

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