JP2018102710A - Electrocardiographic measurement apparatus, method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify an electrode structure and acquire an electrocardiographic signal having a high S/N ratio.SOLUTION: An electrocardiographic measurement apparatus includes: a plurality of back electrodes 14 formed using electric conductive material whose electric resistance varies depending on applied pressure, the back electrodes being arranged at positions on a seat back part 12A of a seat 12 that differ from each other; an electrocardiographic signal detection unit 18 for detecting an electrocardiographic signal for each individual back electrode 14 via electrostatic capacitance generated between a body surface of a crew member seating on the seat 12 and the individual back electrode 14; a pressure detection unit 20 (an electric resistance detection unit 28 and pressure conversion unit 30 thereof) for detecting pressure applied to each of the plurality of back electrodes 14 on the basis of electric resistance of the individual back electrode 14; and an electrocardiographic signal selection unit 24 for selecting, on the basis of a distribution of the pressure detected by the pressure detection unit 20, an electrocardiographic signal to be an output object from electrocardiographic signals detected for the respective individual back electrodes 14 by electrocardiographic signal detection units 18.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrocardiogram measurement apparatus, an electrocardiogram measurement method, and an electrocardiogram measurement program.

  Patent Document 1 discloses an electrocardiogram generated by an electrocardiogram signal generation unit that detects a biological signal of a subject in contact with a plurality of measurement electrodes via each measurement electrode. A technique for amplifying a signal with an amplifier having a variable amplification factor is disclosed. In this technology, the capacitance between the measurement electrode and the subject is estimated by a plurality of pressure sensors provided on the back surface of each measurement electrode, and the amplification factor of the amplifier is calculated based on the estimation result of the capacitance. By setting, the signal level of the electrocardiogram signal is corrected.

JP 2009-219554 A

  In the technique described in Patent Document 1, the sensor unit has a structure in which a pressure sensor is stacked on a measurement electrode, and changes between the measurement electrode and the subject, depending on the contact state between the measurement electrode and the subject. Is estimated using the pressure detected by the pressure sensor. For this reason, the technique described in Patent Document 1 has a problem that the structure of the sensor unit is complicated and the cost increases.

  In addition, the technique described in Patent Document 1 compensates for a decrease in the signal level of the electrocardiogram signal due to a decrease in the contact area and pressure between the measurement electrode and the subject by increasing the amplification factor of the amplifier. ing. However, when the amplification factor of the amplifier is increased, external noise such as power supply noise and electrostatic noise mixed in the measurement electrode is amplified more strongly, so that the S / N ratio of the electrocardiogram signal (signal to noise ratio) And the electrocardiogram signal is buried in noise, which may cause problems such as failure to detect the peak for each heartbeat.

  In one aspect, an object of the present invention is to realize simplification of an electrode structure and acquisition of an electrocardiographic signal having a high S / N ratio.

  The electrocardiograph according to the invention of claim 1 is formed of a conductive material whose electrical resistance changes according to applied pressure, and a plurality of back portions arranged at different positions in the seat back portion of the seat An electrocardiogram signal detection unit for detecting an electrocardiogram signal for each of the back electrodes through an electrostatic capacity generated between the electrodes and the body surface of the human body seated on the seat and the back electrodes; and A pressure detector for detecting the pressure applied to each of the plurality of back electrodes based on the electrical resistance of the individual back electrodes; and an electrocardiogram detected for each of the back electrodes by the electrocardiogram signal detector. And an electrocardiogram signal selector that selects an electrocardiogram signal to be output based on the distribution of the pressure detected by the pressure detector.

  In the first aspect of the present invention, the back electrodes are respectively arranged at different positions in the seat back portion of the seat, and the back electrodes are formed of a conductive material whose electric resistance changes according to the applied pressure. ing. The electrocardiogram signal detection unit detects an electrocardiogram signal for each back electrode through a capacitance generated between the body surface of the human body seated on the seat and each back electrode, and the pressure detection unit The pressure applied to each of the plurality of back electrodes is detected based on the electrical resistance of each back electrode. Thus, in the invention according to claim 1, since the electrocardiogram signal and the pressure can be detected by the back electrode formed of the conductive material whose electric resistance changes according to the applied pressure, the back electrode The structure can be simplified.

  According to the first aspect of the present invention, the electrocardiogram signal selection unit is configured based on the distribution of the pressure detected by the pressure detection unit from the electrocardiogram signal detected for each back electrode by the electrocardiogram signal detection unit. Select the ECG signal to be output. The distribution of pressure detected by the pressure detector changes according to the physique and posture of the human body seated on the seat, and the human body is seated on the back electrode facing the body surface of the human body seated on the seat, that is, the seat An electrocardiogram signal is detected by the back electrode where the pressure detected by the pressure detector is higher than when not. Further, there is a positive correlation between the pressure applied to each of the back electrodes detected by the pressure detector and the signal level of the electrocardiogram signal detected for each back electrode by the electrocardiogram signal detector.

  As a result, by selecting an electrocardiogram signal to be output based on the pressure distribution detected by the pressure detector, an electrocardiogram signal having a high signal level can be selected as an output target, and power noise and electrostatic noise can be selected. The ratio of the signal level of the electrocardiogram signal to the external noise such as S / N ratio is improved. Therefore, according to the first aspect of the invention, it is possible to realize the simplification of the electrode structure and the acquisition of an electrocardiographic signal having a high S / N ratio.

  In the first aspect of the present invention, the electrocardiogram signal selection unit, for example, as described in claim 2, among the electrocardiogram signals detected for each individual back electrode, It is preferable to select an electrocardiographic signal detected from the back electrode including the electrode as an electrocardiographic signal to be output. Thereby, an electrocardiographic signal having a higher signal level can be selected as an output target, and an electrocardiographic signal having a higher S / N ratio can be acquired.

  In the first aspect of the present invention, the electrocardiogram signal selection unit, for example, as described in the third aspect, the human body from the detected pressure distribution among the electrocardiogram signals detected for each individual back electrode. It is preferable to select an electrocardiographic signal detected from a back electrode including a back electrode that is assumed to be closest to the right shoulder of the human body and that is disposed closest to the right shoulder of the human body as an output electrocardiographic signal. The biopotential at the back of the human body has a gradient. For example, if the bioelectric potential at the left shoulder of the human body is 0 [V], the biopotential at the right shoulder of the human body is -0.8 to -0.6 [mV], The bioelectric potential is 0.2 to 0.4 [mV], and the bioelectric potential gradually changes from the right shoulder to the buttocks (details will be described later). And the signal level of the electrocardiogram signal detected for each back electrode by the electrocardiogram signal detector changes in accordance with the bioelectric potential in the part of the body surface on the back of the human body facing the back electrode.

  For this reason, in the invention according to claim 3, the back electrode whose arrangement position is estimated to be closest to the right shoulder of the human body from the detected pressure distribution, that is, the biopotential of the human body based on the buttocks. An electrocardiogram signal detected from a back electrode including a back electrode that is estimated to detect an electrocardiogram signal having a higher signal level due to being closest to the right shoulder with the largest difference as an electrocardiogram signal to be output. Selected. Thereby, an electrocardiographic signal having a higher signal level can be selected as an output target, and an electrocardiographic signal having a higher S / N ratio can be acquired.

  Further, in the invention according to any one of claims 1 to 3, the electrocardiogram signal selection unit is configured so that the pressure from the electrocardiogram signal detected for each individual back electrode as described in claim 4, for example. It is preferable to periodically select an electrocardiographic signal to be output based on the distribution of the human body while the seating of the human body on the seat is detected. As described above, there is a positive correlation between the pressure applied to the back electrode and the signal level of the electrocardiogram signal detected from the back electrode, and the distribution of pressure detected by the pressure detection unit is seated on the seat. It also changes depending on the posture of the human body. Therefore, when the posture of the human body seated on the seat changes with time, the signal level of the electrocardiogram signal detected from each back electrode changes accordingly.

Therefore, in the invention described in claim 4, the seating of the human body on the seat detects that the electrocardiogram signal to be output is selected from the electrocardiogram signal detected for each individual back electrode based on the pressure distribution. Do it regularly while being. Thereby, even if the posture of the human body seated on the seat changes with time, an electrocardiographic signal having a high S / N ratio can be stably acquired.

  Moreover, in invention of any one of Claims 1-4, as described in Claim 5, for example, the collar part electrode arrange | positioned at the seat cushion part of a sheet | seat, and the body surface of the human body seated on the sheet | seat An electrocardiogram signal detection unit that detects an electrocardiogram signal through a capacitance generated between the electrode and the buttocks electrode, an electrocardiogram signal to be output selected by the electrocardiogram signal selection unit, and an electrocardiogram signal detection unit It is preferable to further include an electrocardiogram output generation unit that generates an electrocardiogram output signal from the difference from the buttocks electrocardiogram signal detected by the above.

  As described above, the bioelectric potential gradually changes from the right shoulder to the buttocks on the back of the human body. For example, when the bioelectric potential at the left shoulder of the human body is 0 [V], the bioelectric potential at the right shoulder of the human body and the human body The biopotentials at the buttocks are different in polarity. Therefore, the electrocardiogram signal is detected through the capacitance generated between the body surface of the human body seated on the seat and the buttocks electrode, and the output electrocardiogram signal selected by the electrocardiogram signal selector and the buttocks heart By generating an electrocardiographic output signal from the difference from the electric signal, an electrocardiographic output signal having a higher S / N ratio can be output as compared with the case of outputting an electrocardiographic signal to be output.

  The electrocardiogram measurement method according to the invention of claim 6 is formed of a conductive material whose electrical resistance changes according to applied pressure, and a plurality of back portions arranged at different positions in the seat back portion of the seat. The pressure applied to each of the electrodes is detected based on the electrical resistance of each of the back electrodes, and between each of the plurality of back electrodes and the body surface of the human body seated on the seat and each of the back electrodes. The computer executes a process of selecting an electrocardiographic signal to be output based on the detected pressure distribution from the electrocardiographic signal detected by the electrocardiogram signal detecting unit for each individual back electrode through the generated capacitance. Therefore, as in the first aspect of the invention, an electrocardiographic signal having a high S / N ratio can be obtained from an electrode having a simple structure.

  The electrocardiogram measurement program according to the invention of claim 7 is formed of a conductive material whose electrical resistance changes according to applied pressure, and a plurality of back portions arranged at different positions in the seat back portion of the seat The pressure applied to each of the electrodes is detected based on the electrical resistance of each of the back electrodes, and between each of the plurality of back electrodes and the body surface of the human body seated on the seat and each of the back electrodes. The computer executes a process of selecting an electrocardiogram signal to be output based on the detected pressure distribution from the electrocardiogram signal detected by the electrocardiogram signal detection unit for each individual back electrode through the generated capacitance. Therefore, similarly to the first aspect of the invention, an electrocardiographic signal having a high S / N ratio can be obtained from an electrode having a simple structure.

  As one aspect, there is an effect that simplification of the electrode structure and acquisition of an electrocardiographic signal having a high S / N ratio can be realized.

It is a schematic block diagram of an example of an electrocardiograph. It is a perspective view which shows an example of a back part electrode. It is a diagram which shows an example of the relationship between the pressure added to the back electrode, and the electrical resistance of a back electrode. It is an image figure which shows an example of distribution of the bioelectric potential in the back surface of a human body. It is a block diagram of an example of an electrocardiogram measuring apparatus. It is an image figure for demonstrating the principle of the electrocardiogram signal detection by an electrocardiogram signal detection part. It is a flowchart which shows an example of the electrocardiogram measurement process performed by electrocardiograph ECU. It is a flowchart which shows the other example of an electrocardiogram measurement process. It is a perspective view for demonstrating an example of the back part electrode facing the back surface of a human body.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows an electrocardiograph 10 according to this embodiment. The electrocardiograph 10 includes a plurality of back electrodes 14 disposed at different positions in the seat back portion 12A of the seat 12 and a buttocks electrode 16 disposed on the seat cushion portion 12B of the seat 12. Yes. Hereinafter, as an example of the seat 12, a case where the seat 12 is mounted on a vehicle and an occupant of the vehicle sits on the seat 12 will be described, but the present invention is not limited to this.

  The electrocardiograph 10 is connected to a plurality of electrocardiogram signal detectors 18 connected to different back electrodes 14, a pressure detector 20 connected to each of the plurality of back electrodes 14, and a buttocks electrode 16. The buttocks electrocardiogram signal detection unit 22, the electrocardiogram signal selection unit 24 to which the plurality of electrocardiogram signal detection units 18 and the pressure detection unit 20 are respectively connected, the electrocardiogram signal selection unit 24, and the buttocks electrocardiogram signal detection unit 22 Is connected to the electrocardiogram output generation unit 26. The pressure detector 20 includes a plurality of electrical resistance detectors 28 connected to different back electrodes 14 and a pressure conversion unit 30 connected to each of the plurality of electrical resistance detectors 28.

  The back electrode 14 is formed of a conductive material whose electrical resistance changes according to the applied pressure. Thereby, as will be described later, the detection of the electrocardiogram signal and the pressure can be performed by the individual back electrode 14, and the structure of the back electrode 14 is simplified. As an example of the conductive material, a conductive material 36 in which a conductive material 34 such as carbon fiber is distributed in a predetermined ratio in a foamed material 32 as shown in FIG.

  The conductive material 36 exhibits conductivity by a conductive material 34 distributed in the foam material 32. In addition, the conductive material 36 is subjected to pressure, and when the foam material 32 is compressed and deformed according to the applied pressure, the portion of the foam material 32 where the adjacent conductive materials 34 are in contact with each other increases. As shown in FIG. 3, the electric resistance decreases according to the applied pressure. In addition, when the pressure applied to the conductive material 36 decreases or becomes zero and the foam material 32 is restored and deformed, the portion of the foam material 32 where the adjacent conductive materials 34 are in contact with each other is reduced. As shown in FIG. 3, the electric resistance is restored (increased) according to the decrease in applied pressure.

  However, as shown in FIG. 3, the relationship between the pressure and the electrical resistance in the conductive material 36 includes a dead area where the electrical resistance does not change even if the pressure changes. For this reason, when the back electrode 14 is formed of the conductive material 36, the change range of the pressure applied to the back electrode 14 (conductive material 36) when an occupant is seated on the seat 12 is the pressure change of the above relationship. It is desirable to adjust the distribution ratio of the conductive material 34 in advance so as to match the region where the electrical resistance changes according to the region (region other than the dead region). The conductive material forming the back electrode 14 is not limited to the conductive material 36 shown in FIG. 2 as long as it is a conductive material whose electric resistance changes according to the applied pressure.

  By the way, there is a gradient in the bioelectric potential on the back surface of the human body. As shown in FIG. 4, for example, when the bioelectric potential on the left shoulder of the human body is 0 [V], the bioelectric potential on the right shoulder of the human body is −0.8 to −0.6. [mV], the bioelectric potential in the hip of the human body is 0.2 to 0.4 [mV], and the bioelectric potential gradually changes from the right shoulder to the hip. The signal level of the electrocardiogram signal detected by the electrocardiogram signal detection unit 18 for each individual back electrode 14 changes according to the bioelectric potential in the portion of the body surface on the back of the human body facing the individual back electrode. .

  For this reason, the plurality of back electrodes 14 are arranged such that the position of the seat 12 in the seat back portion 12A is biased to the left side and the upper side in FIG. However, the physique and posture of the occupant seated on the seat 12 are not constant, and the position of the right shoulder of the occupant seated on the seat 12 changes according to the physique and posture of the occupant. For this reason, in the example shown in FIG. 1, four back electrodes 14 are arranged in a matrix, and the arrangement of the four back electrodes 14 is arranged on the left side and the upper side in FIG. It is biased to the side closer to the shoulder. Thus, regardless of the physique and posture of the occupant seated on the seat 12, at least one of the four back electrodes 14 is located within a predetermined distance from the position of the right shoulder of the occupant seated on the seat 12.

  The number, area, and arrangement position of the back electrodes 14 are not limited to the example shown in FIG. 1. For example, a large number of back electrodes 14 may be arranged on the entire surface of the seat back portion 12A. However, if the number of back electrodes 14 increases, the number of electrocardiogram signal detectors 18 and pressure detectors 20 also increases, and the configuration of the electrocardiograph 10 becomes complicated.

  Further, when the area of the back electrode 14 is increased for the purpose of suppressing the number of the back electrodes 14, the possibility that one back electrode 14 straddles different parts of the bioelectric potential on the back surface of the human body increases. The electrocardiographic signal detected from the back electrode 14 has a signal level corresponding to the biopotential at a part having a lower biopotential among a plurality of parts having different biopotentials straddling the back electrode 14. For this reason, it is desirable to suppress the number and area of the back electrodes 14 and to bias the arrangement positions of the plurality of back electrodes 14 toward the side closer to the right shoulder of the occupant seated on the seat 12.

  The plurality of electrocardiogram signal detection units 18 are mutually connected through capacitance Cext (see FIG. 6) between the body surface of the occupant 40 seated on the seat 12 and the back electrode 14 connected to the electrocardiogram signal detection unit 18. An electrocardiographic signal is detected from a different back electrode 14. The plurality of ECG signal detection units 18 have the same configuration, and FIG. 5 shows the configuration of one ECG signal detection unit 18.

  The electrocardiogram signal detection unit 18 includes a high impedance resistor 44 having one end connected to the back electrode 14 via a branch point 42 with the electrical resistance detection unit 28, and an operational amplifier 46 having an input end connected to one end of the resistor 44. And an A / D (analog / digital) converter 48 whose input terminal is connected to the output terminal of the operational amplifier 46. The other end of the resistor 44 is grounded. The operational amplifier 46 operates as a buffer amplifier in which the amplification factor = 1 and the input impedance is increased.

As shown in FIG. 6, when the electrocardiographic signal of the occupant 40 seated on the seat 12 is Va, the impedance between the body surface of the occupant 40 and the back electrode 14 is Zext, and the input impedance of the operational amplifier 46 is Zin, the operational amplifier 46 The output signal Vout is expressed by the following equation (1).
Vout = Zin / (Zext + Zin) (1)

Further, assuming that the capacitance between the body surface of the occupant 40 and the back electrode 14 is Cext, the impedance Zext is expressed by the following equation (2).
Zext = 1 / jωCext (2)

When the input resistance of the operational amplifier 46 is Rin and the input capacitance is Cin, the input impedance Zin of the operational amplifier 46 is expressed by the following equation (3).
Zin = Rin / (1 + jωCin · Rin) (3)

  From the above equation (1), if the input impedance Zin of the operational amplifier 46 is sufficiently larger than the impedance Zext between the body surface of the occupant 40 and the back electrode 14, the output signal Vout of the operational amplifier 46 is the electrocardiogram of the occupant 40. It becomes almost equal to the number Va.

  The output terminal of the A / D converter 48 of the electrocardiogram signal detector 18 is connected to an electrocardiograph ECU 62 (details will be described later: ECU) via a bus 60 of an in-vehicle system provided in the vehicle on which the seat 12 is mounted. (Electronic Control Unit) is connected to a CPU, a control unit including a memory and a nonvolatile storage unit. The output signal Vout of the operational amplifier 46 is converted into digital electrocardiographic signal data by the A / D converter 48 and output to the electrocardiographic measurement ECU 62.

  The in-vehicle system includes ECUs that perform different controls, and these are respectively connected to the bus 60. FIG. 5 shows only the electrocardiograph ECU 62 among the ECUs included in the in-vehicle system.

  Although the detailed illustration of the buttocks electrocardiogram signal detection unit 22 is omitted, it has the same configuration as the electrocardiogram signal detection unit 18 except that it is connected to the buttocks electrode 16 instead of the back electrode 14. That is, the buttocks electrocardiogram signal detection unit 22 detects the buttocks electrocardiogram signal through the capacitance generated between the body surface of the human body seated on the seat 12 and the buttocks electrode 16, and converts it into digital buttocks electrocardiogram signal data. The data is converted and output to the electrocardiogram measurement ECU 62.

  The pressure detection unit 20 detects the pressure applied to each of the plurality of back electrodes 14. The plurality of electrical resistance detection units 28 included in the pressure detection unit 20 have the same configuration, and FIG. 5 shows the configuration of one electrical resistance detection unit 28. As shown in FIG. 5, the electrical resistance detection unit 28 has one end connected to the back electrode 14 via a branch point 42 with the electrocardiogram signal detection unit 18, and one end connected to the switch 53 that becomes conductive when electrical resistance is detected. Is connected to the other end of the switch 53 and the other end is grounded, an operational amplifier 52 whose input end is connected to one end of the resistive element 50, and an A / O whose input end is connected to the output end of the operational amplifier 52. D converter 54.

  The back electrode 14 is connected to the positive terminal of the DC power source 56 via the switch 51 that is on the opposite side to the side connected to the electrical resistance detection unit 28 (and the electrocardiogram signal detection unit 18) when the electrical resistance is detected. The negative terminal of the DC power source 56 is grounded. As a result, the input terminal of the operational amplifier 52 becomes a potential obtained by dividing the voltage of the DC power source 56 by the back electrode 14 and the resistance element 50 when the electric resistance is detected, and pressure is applied to the back electrode 14 or the pressure changes. Thus, when the electrical resistance of the back electrode 14 changes, the potential at the input terminal of the operational amplifier 52 also changes according to the change in the electrical resistance of the back electrode 14. The operational amplifier 52 amplifies the potential at the input end and outputs it.

  The output end of the A / D converter 54 of the electrical resistance detector 28 is connected to the electrocardiograph ECU 62 via the bus 60. The output signal of the operational amplifier 52 is converted into digital electrical resistance data representing the electrical resistance of the back electrode 14 by the A / D converter 54 and input to the electrocardiograph ECU 62.

  The pressure conversion unit 30 of the pressure detection unit 20 converts the electrical resistance of the plurality of back electrodes 14 respectively detected by the plurality of electrical resistance detection units 28 into the magnitude of pressure applied to each of the plurality of back electrodes 14. .

  The electrocardiogram signal selector 24 detects the pressure applied to each of the plurality of back electrodes 14 detected by the pressure detector 20 from the electrocardiogram signal detected for each back electrode 14 by the electrocardiogram signal detector 18. The electrocardiogram signal to be output is selected on the basis of the distribution of. More specifically, the electrocardiogram signal selector 24 outputs an electrocardiogram signal detected from the back electrode 14 having the maximum detected pressure among the electrocardiogram signals detected for each back electrode 14 as an output target. Select as ECG signal.

  The electrocardiogram output generator 26 generates an electrocardiogram output signal from the difference between the electrocardiogram signal to be output selected by the electrocardiogram signal selector 24 and the buttocks electrocardiogram signal detected by the buttocks electrocardiogram signal detector 22. Is generated.

  The pressure conversion unit 30, the electrocardiogram signal selection unit 24, and the electrocardiogram output generation unit 26 of the pressure detection unit 20 described above are realized by an electrocardiogram measurement ECU 62 shown in FIG. The electrocardiogram measurement ECU 62 includes a CPU 64, a memory 66, an electrocardiogram measurement program 70, and a nonvolatile storage unit 68 that stores an electrical resistance-pressure conversion table 78. The CPU 64 reads the electrocardiogram measurement program 70 from the storage unit 68 and expands it in the memory 66, and sequentially executes the processes of the electrocardiogram measurement program 70.

  The electrocardiogram measurement program 70 includes a pressure conversion process 72, an electrocardiogram signal selection process 74, and an electrocardiogram output generation process 76. The CPU 64 operates as the pressure conversion unit 30 illustrated in FIG. 1 by executing the pressure conversion process 72. The CPU 64 operates as the electrocardiogram signal selection unit 24 shown in FIG. 1 by executing the electrocardiogram signal selection process 74. The CPU 64 operates as the electrocardiogram output generation unit 26 shown in FIG. 1 by executing the electrocardiogram output generation process 76.

  The electrical resistance-pressure conversion table 78 stores the relationship between the pressure applied to the back electrode 14 and the electrical resistance of the back electrode 14 as shown in FIG. 3 as an example. Note that it may be stored in another format such as a function instead of the table format.

  Next, as an operation of the first embodiment, an electrocardiogram measurement process realized by the CPU 64 of the electrocardiogram measurement ECU 62 executing the electrocardiogram measurement program 70 will be described with reference to FIG. The electrocardiogram measurement process is executed when an occupant is seated on the seat 12. The seating of the occupant on the seat 12 may be detected based on a change in the buttocks electrocardiogram signal output from the buttocks electrocardiogram signal detection unit 22. The seat 12 may be separated from the electrocardiograph 10. It can also be detected by a seating sensor or the like provided in the case.

  In step 100 of the electrocardiogram measurement process, the pressure conversion unit 30 of the pressure detection unit 20 sets 1 to a variable i for identifying each back electrode 14. In step 102, the pressure conversion unit 30 acquires electrical resistance data representing the electrical resistance Ri of the i-th back electrode 14 from the i-th electrical resistance detection unit 28 connected to the i-th back electrode 14. In step 104, the pressure conversion unit 30 applies the electric resistance Ri of the i-th back electrode 14 represented by the electric resistance data acquired in step 102 to the i-th back electrode 14 based on the electric resistance-pressure conversion table 78. Convert to applied pressure Pi.

  In the next step 106, the pressure conversion unit 30 determines whether or not the variable i has reached the total number s of the back electrodes 14. If the determination in step 106 is negative, the process proceeds to step 108, and in step 108, the pressure conversion unit 30 increments the variable i by 1 and returns to step 102. Thus, steps 102 to 108 are repeated until the determination in step 106 is affirmed, and pressures P1 to Ps applied to each of the s back electrodes 14 are calculated.

  When the calculation of the pressures P1 to Ps applied to each of the s back electrodes 14 is completed, the determination in step 106 is affirmed and the routine proceeds to step 110. In step 110, the electrocardiogram signal selection unit 24 extracts the maximum values of the pressures P1 to Ps calculated by the pressure conversion unit 30 of the pressure detection unit 20.

  Here, there is a positive correlation between the pressures P1 to Ps applied to each of the s back electrodes 14 and the signal level of the electrocardiogram signal detected for each back electrode 14 by the electrocardiogram signal detector 18. There is. Therefore, in the next step 112, the electrocardiogram signal selection unit 24 selects an electrocardiogram signal detected from the back electrode 14 from which the maximum value of the pressure extracted in step 110 is obtained as an output target. Thereby, an electrocardiographic signal estimated to have a high signal level among the electrocardiographic signals detected from each of the s back electrodes 14 can be selected as an output target.

  In the next step 114, the electrocardiogram output generator 26 generates and generates an electrocardiogram output signal corresponding to the difference between the electrocardiogram signal selected as the output target by the electrocardiogram signal selector 24 and the buttocks electrocardiogram signal. A process of supplying the electrocardiogram output signal to another ECU that performs a predetermined process using the electrocardiogram output signal among the ECUs included in the in-vehicle system is started. The predetermined processing performed by other ECUs includes, for example, personal identification processing for identifying an occupant seated on the seat 12 described in Japanese Patent Application No. 2016-029662 already filed by the applicant of the present application or the like, or seat 12 is a state monitoring process for monitoring the health state of the occupant seated on the vehicle.

  In the next step 116, the electrocardiogram output generation unit 26 determines whether or not a predetermined time has elapsed since the start of generation / supply of the electrocardiogram output signal in step 114. If the determination in step 116 is negative, the process proceeds to step 118. In step 118, the electrocardiogram output generation unit 26 has completed the seating of the occupant on the seat 12 (whether the occupant has left the seat 12). Judge whether or not. If the determination in step 118 is also negative, the process returns to step 116, and steps 116 and 118 are repeated until the determination in step 116 or step 118 is affirmed. During this time, the electrocardiogram output generator 26 continues to generate and supply the electrocardiogram output signal.

  When a predetermined time has elapsed since the generation / supply of the electrocardiogram output signal is started in step 114, the determination in step 116 is affirmed, the process returns to step 100, and the processing after step 100 is repeated. As a result, the posture of the occupant seated on the seat 12 changes with time, and when the pressure applied to each of the plurality of back electrodes 14 changes according to the change of the occupant's posture, the electrocardiogram signal selection unit 24 outputs The electrocardiographic signal selected as the target is changed to an electrocardiographic signal detected from the back electrode 14 in which the pressure after the change shows the maximum value. When the occupant leaves the seat 12, the determination in step 118 is affirmed and the electrocardiogram measurement process is terminated.

  Thus, in the first embodiment, the plurality of back electrodes 14 formed of a conductive material whose electric resistance changes according to the applied pressure are arranged at different positions in the seat back portion 12A of the seat 12. Has been. The electrocardiogram signal detection unit 18 detects an electrocardiogram signal for each back electrode 14 through electrostatic capacitance generated between the body surface of the occupant seated on the seat 12 and each back electrode 14. Moreover, the pressure detection unit 20 (the electrical resistance detection unit 28 and the pressure conversion unit 30 thereof) detects the pressure applied to each of the plurality of back electrodes 14 based on the electrical resistance of each back electrode 14. Then, the electrocardiogram signal selection unit 24 outputs the heart to be output based on the distribution of pressure detected by the pressure detection unit 20 from the electrocardiogram signal detected for each back electrode 14 by the electrocardiogram signal detection unit 18. Select the electric signal. Thereby, simplification of the structure of the back electrode 14 and acquisition of an electrocardiographic signal having a high S / N ratio can be realized.

  In the first embodiment, the electrocardiogram signal selection unit 24 selects an electrocardiogram signal detected from the back electrode 14 having the maximum detected pressure among the electrocardiogram signals detected for each back electrode 14. Select as an electrocardiographic signal to be output. Thereby, an electrocardiographic signal having a higher signal level can be selected as an output target, and an electrocardiographic signal having a higher S / N ratio can be acquired.

  In the first embodiment, the buttocks electrode 16 is disposed on the seat cushion portion 12 </ b> B of the seat 12, and the buttocks electrocardiogram signal detection unit 22 is generated between the body surface of the occupant seated on the seat 12 and the buttocks electrode 16. The buttocks electrocardiogram signal is detected through the capacitance. Then, the electrocardiogram output generator 26 generates an electrocardiogram output signal from the difference between the electrocardiogram signal to be output selected by the electrocardiogram signal selector 24 and the buttocks electrocardiogram signal detected by the buttocks electrocardiogram signal detector 22. Is generated. As a result, an electrocardiographic output signal having a higher S / N ratio can be output as compared with a case where the electrocardiographic signal to be output is output as it is.

  Further, in the first embodiment, the electrocardiogram signal selection unit 24 outputs the heart to be output based on the distribution of the pressure applied to each of the plurality of back electrodes 14 from the electrocardiogram signal detected for each back electrode 14. The electric signal is selected periodically while the occupant is seated on the seat 12. Thereby, even if the posture of the occupant seated on the seat 12 changes with time, an electrocardiographic signal having a high S / N ratio can be stably acquired, and an electrocardiographic output having a high S / N ratio. A signal can be output stably.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In addition, since 2nd Embodiment is the structure same as 1st Embodiment, it attaches | subjects the same code | symbol to each part, and abbreviate | omits description of a structure. Hereinafter, as an operation of the second embodiment, with reference to FIG. 8, only the part different from the electrocardiogram measurement process (FIG. 7) described in the first embodiment will be described for the electrocardiogram measurement process according to the second embodiment. .

  The electrocardiogram measurement process according to the second embodiment is different from the electrocardiogram measurement process described in the first embodiment in that the process of steps 120 and 122 is performed instead of the process of steps 110 and 112. ing. In step 120, the electrocardiogram signal selection unit 24 seats on the seat 12 the back electrode 14 whose pressure P calculated by the pressure conversion unit 30 of the pressure detection unit 20 is a predetermined value or more from among the plurality of back electrodes 14. It is extracted as a back electrode 14 facing the back of the occupant.

  As an example, when the back surface of the occupant seated on the seat 12 is in a range shown as a range 90 in FIG. 9, all four back electrodes 14 are used as the back electrodes 14 having a pressure P of a predetermined value or more. Is extracted as the back electrode 14 facing the back of the occupant seated on the seat 12. Further, as an example, when the back surface of the occupant seated on the seat 12 is in a range shown as a range 92 in FIG. 9, the four back electrodes 14 are used as the back electrodes 14 whose pressure P is a predetermined value or more. Among them, one back electrode 14 located at the lower right corner in FIG. 9 is extracted as the back electrode 14 facing the back of the occupant seated on the seat 12.

  In the next step 122, the electrocardiogram signal selection unit 24 starts from the back electrode 14 estimated to be closest to the right shoulder of the occupant among the back electrodes 14 extracted as the back electrode 14 facing the back of the occupant in step 120. The ECG signal is selected as the output target. The back electrode 14 estimated to be closest to the right shoulder of the occupant is the back electrode 14 located at the upper left corner in FIG. 9 among the back electrodes 14 extracted in step 120.

  As an example, when the back surface of the occupant seated on the seat 12 is in a range shown as a range 90 in FIG. 9, as described above, four back electrodes 14 are used as the back electrode 14 facing the back surface of the occupant. Everything is extracted. Therefore, in step 122, the back electrode 14 located in the upper left corner in FIG. 9 is selected as the back electrode 14 estimated to be closest to the right shoulder of the occupant, and detected from the back electrode 14 located in the upper left corner. An electrocardiogram signal is selected as an output target.

  Further, as an example, when the back surface of the occupant seated on the seat 12 is in a range shown as a range 92 in FIG. 9, as described above, the back electrode 14 facing the back surface of the occupant is used as the lower right corner in FIG. One back electrode 14 located at is extracted. Therefore, in step 122, the back electrode 14 located in the lower right corner in FIG. 9 is selected as the back electrode 14 estimated to be closest to the right shoulder of the occupant, and detected from the back electrode 14 located in the lower right corner. An electrocardiogram signal is selected as an output target.

  As described above, in the second embodiment, the electrocardiogram signal selection unit 24 applies to the seat 12 from the distribution of pressure detected by the pressure detection unit 20 among the electrocardiogram signals detected for each back electrode 14. An electrocardiographic signal detected from the back electrode 14 that is opposed to the back of the seated occupant and is estimated to be closest to the occupant's right shoulder is selected as an electrocardiographic signal to be output. Thereby, in addition to the effect demonstrated in 1st Embodiment, the electrocardiogram signal with a higher signal level can be selected as an output object, and the electrocardiogram signal with a higher S / N ratio can be acquired.

  In addition, although the aspect which selects one electrocardiogram signal as an output target electrocardiogram signal was described above, it is not limited to this, and a plurality of electrocardiogram signals are selected as an output target electrocardiogram signal. The electrocardiogram output generation unit 26 may generate an electrocardiogram output signal corresponding to the difference between the average of a plurality of electrocardiogram signals to be output and the buttocks electrocardiogram signal.

  However, a specific back electrode 14 having a lower biopotential than the other back electrode 14 in a portion of the back surface of the opposite occupant is mixed in the plurality of back electrodes 14 corresponding to the plurality of electrocardiographic signals to be output. If so, the average of the plurality of electrocardiographic signals to be output becomes a signal level corresponding to the bioelectric potential at the back portion of the occupant facing the specific back electrode 14. For this reason, when selecting an electrocardiographic signal to be output, when there are a plurality of back electrodes 14 in the back electrode 14 where the biopotentials at the back of the occupant facing each other are at the maximum level, It is preferable to select a plurality of biological signals detected from the plurality of back electrodes 14 at the maximum level as output targets.

  Although the material for forming the buttock electrode 16 is not particularly described above, the buttock electrode 16 is also formed of a conductive material whose electric resistance changes according to the applied pressure, as with the back electrode 14. Also good. Thereby, it becomes possible to make the buttock electrode 16 function also as a seating sensor.

  In the above description, the electrocardiogram measurement program 70, which is an example of the electrocardiogram measurement program according to the present invention, has been described as being prestored (installed) in the storage unit 68 of the electrocardiogram measurement ECU 62. The electric measurement program can also be provided in a form recorded on a recording medium such as a CD-ROM or a DVD-ROM.

DESCRIPTION OF SYMBOLS 10 ... Electrocardiograph, 12 ... Seat, 12A Seat back part, 12B ... Seat cushion part, 14 ... Back electrode, 16 ... Buttocks electrode, 18 ... Electrocardiogram signal detection part, 20 ... Pressure detection part, 22 ... Buttocks heart Electrical signal detection unit, 24 ... ECG signal selection unit, 26 ... ECG output generation unit, 28 ... Electrical resistance detection unit, 30 ... Pressure conversion unit, 32 ... Foam material, 34 ... Conductive material, 36 ... Conductive material, 46 ... Operational amplifier, 50 ... Resistance element, 52 ... Operational amplifier, 56 ... DC power supply, 62 ... Electrocardiogram measurement ECU, 64 ... CPU, 66 ... Memory, 68 ... Storage unit, 70 ... Electrocardiogram measurement program

Claims (7)

A plurality of back electrodes formed of a conductive material whose electrical resistance changes according to applied pressure, and disposed at different positions in the seat back portion of the seat;
An electrocardiogram signal detection unit that detects an electrocardiogram signal for each of the back electrodes through a capacitance generated between the body surface of the human body seated on the seat and each of the back electrodes;
A pressure detector that detects the pressure applied to each of the plurality of back electrodes based on the electrical resistance of each of the back electrodes;
ECG signal selection for selecting an ECG signal to be output based on the distribution of the pressure detected by the pressure detection unit from the ECG signal detected for each of the back electrodes by the ECG signal detection unit And
ECG measuring device including   The electrocardiogram signal selection unit outputs an electrocardiogram signal detected from the back electrode including the back electrode having the maximum detected pressure among the electrocardiogram signals detected for each of the back electrodes. The electrocardiograph according to claim 1, which is selected as a target electrocardiogram signal.   The electrocardiogram signal selection unit faces the body surface of the human body from the detected pressure distribution among the electrocardiogram signals detected for each of the back electrodes, and the arrangement position is closest to the right shoulder of the human body The electrocardiogram measurement device according to claim 1, wherein an electrocardiogram signal detected from the back electrode including the back electrode presumed to be selected is selected as the electrocardiogram signal to be output.   The electrocardiogram signal selection unit detects the seating of the human body on the seat to select an electrocardiogram signal to be output based on the pressure distribution from the electrocardiogram signal detected for each of the back electrodes. The electrocardiograph according to any one of claims 1 to 3, wherein the electrocardiograph is periodically performed while being performed. A buttock electrode disposed in a seat cushion portion of the seat;
A buttocks electrocardiogram signal detection unit that detects a buttocks electrocardiogram signal through a capacitance generated between the body surface of the human body seated on the seat and the buttocks electrode;
An electrocardiogram output generation unit that generates an electrocardiogram output signal from a difference between the output electrocardiogram signal selected by the electrocardiogram signal selection unit and the buttocks electrocardiogram signal detected by the buttocks electrocardiogram signal detection unit When,
The electrocardiograph according to any one of claims 1 to 4, further comprising: The pressure applied to each of the plurality of back electrodes formed of a conductive material whose electrical resistance changes according to the applied pressure and arranged at different positions in the seat back portion of the sheet Based on the electrical resistance of
The heart detected by the electrocardiogram signal detection unit for each of the back electrodes through capacitance generated between each of the plurality of back electrodes, the body surface of the human body seated on the seat, and the individual back electrodes. An electrocardiographic measurement method in which a computer executes a process of selecting an electrocardiographic signal to be output based on the detected pressure distribution from an electric signal. The pressure applied to each of the plurality of back electrodes formed of a conductive material whose electrical resistance changes according to the applied pressure and arranged at different positions in the seat back portion of the sheet Based on the electrical resistance of
The heart detected by the electrocardiogram signal detection unit for each of the back electrodes through capacitance generated between each of the plurality of back electrodes, the body surface of the human body seated on the seat, and the individual back electrodes. An electrocardiogram measurement program for causing a computer to execute processing for selecting an electrocardiogram signal to be output based on the detected pressure distribution from an electric signal.