JP5211773B2 - ECG waveform measuring device - Google Patents

Description

  The present invention relates to a capacitively coupled electrocardiographic waveform measuring apparatus that measures a subject's electrocardiographic signal without imposing a burden on the subject.

  Conventionally, as an electrocardiographic waveform measurement device that enables simple measurement of the electrocardiogram signal of the driver who is the subject in the car while wearing the clothes, the vital signal required for generating the electrocardiogram signal is detected from the subject. An electrostatic capacitance type electrode is known in which a measurement electrode for performing the measurement is not directly attached to the skin of the subject but is placed facing the subject.

In this case, the measurement electrode can be installed on a part to be pressed by a subject seated on the seat, specifically, a seat belt (see, for example, Patent Document 1) or a seat (see, for example, Patent Document 2). It is considered.
JP 2007-82938 A JP 2007-301175 A

  However, in the capacitively coupled electrocardiographic waveform measurement device, the amplitude (voltage level) of the biological signal detected by the measurement electrode changes due to the capacitance between the measurement electrode and the subject, The capacitance varies greatly depending on the contact state (contact area, adhesion degree, etc.) between the measurement electrode and the subject. Therefore, there has been a problem that when the contact state changes depending on the body movement or sitting of the subject, an effective biological signal (and thus an electrocardiographic signal) may not be detected.

That is, as shown in FIG. 16, an equivalent circuit in each measurement electrode is represented by a capacitor formed by the measurement electrode and a differential amplifier.
When the impedance of the capacitor is Z, the resistance value between the measurement electrodes is R, and the biological signal generated by the subject is Vs, the biological signal V measured by the measurement electrode is expressed by the following equation (1). However, Z is expressed by equation (2), where C is the capacitance of the capacitor and f is the frequency of the biological signal.

V = R / (Z + R) .Vs (1)
Vs = 1 / (2πfC) (2)
As can be seen from the equations (1) and (2), the smaller the capacitance C of the capacitor, the greater the impedance Z of the capacitor, and the measured biological signal V decreases.

  Here, FIG. 17 is a graph showing the theoretical value of the input / output ratio V / Vs obtained from the equation (1) and the actual value of the input / output ratio V / Vs. As can be seen from the figure, when the capacitance C of the capacitor is large (4 nF or more in the graph), the measured value of the input / output ratio V / Vs is almost the theoretical value, but when the capacitance C of the capacitor is small. (2nF or less in the graph) is a value that deviates from the theoretical value and greatly deviates.

The measurement conditions for the actual measurement values are: input signal: 1 mV, sine wave of 10 Hz, sampling frequency: 1 kHz, insertion cloth: cotton, silk, film, measurement electrode area: diameter 120 mm.
In order to solve the above-described problems, the present invention is a capacitively coupled electrocardiographic waveform measuring apparatus that performs highly reliable measurement of an electrocardiographic signal regardless of changes in the contact state between a measurement electrode and a subject. The purpose is to make it possible.

  The electrocardiographic waveform measuring device according to claim 1, which is an invention made to achieve the above object, comprises an intermediate electrode and a pair of differential electrodes that are located in or in contact with a subject seated on the seat or inside the seat. The electrocardiogram signal generating means generates a signal indicating a potential difference between the pair of differential electrodes as an electrocardiogram signal, with the potential of the intermediate electrode as a reference potential.

  At this time, the estimation means estimates the capacitance between the measurement electrodes and the subject for each measurement electrode, and based on the estimation result, the correction means is generated by the electrocardiogram signal generation means. Correct the ECG signal level.

Specifically, the smaller the electrostatic capacitance of the measurement electrode, the lower the voltage level of the signal detected by the pair of differential electrodes. Therefore, the correction means may correct so as to compensate for the decrease.
According to the electrocardiogram waveform measuring apparatus of the present invention configured as described above, the capacitance between the measurement electrode and the subject is estimated, and the signal level of the electrocardiogram signal is corrected based on the estimation result. Therefore, a highly reliable electrocardiographic signal measurement result can be obtained regardless of the contact state between the measurement electrode and the subject (and hence the capacitance).

By the way, as described in claim 2, when the measurement electrodes are each composed of a single unit electrode, the estimation means may be configured as follows.
That is, for each measurement electrode, there is provided a pressure detection means composed of a plurality of pressure sensors respectively provided at a plurality of portions of the measurement electrode, and the effective sensor extraction means is a pressure sensor constituting the pressure detection means, A sensor whose output is equal to or greater than a preset valid threshold is extracted as a valid sensor. Further, the contact information calculation means calculates, for each measurement electrode, the contact area between the measurement electrode and the subject based on the number of effective sensors, and calculates the contact pressure between the measurement electrode and the subject. Calculated based on the detected pressure at.

Then, the estimation means estimates the capacitance based on the contact area and contact pressure calculated by the contact information calculation means.
According to the electrocardiographic waveform measuring apparatus of the present invention configured as described above, the area (contact area) of the part that is reliably in contact with the subject in the measurement electrode, and the pressure applied to the part (contact pressure) Since the electrostatic capacitance between the measurement electrode and the subject is estimated using, the estimation accuracy of the electrostatic capacitance, and thus the reliability of the measurement result of the electrocardiogram signal can be further improved.

  That is, the capacitance C between two electrodes (here, the measurement electrode and the human body) is expressed by the equation (3), where d is the distance between the electrodes, S is the contact area, and ε is the dielectric constant between the electrodes. The contact pressure is considered to affect the distance d and change the capacitance C.

C = ε × S / d (3)
Here, FIG. 18 shows the relationship between the pressure (contact pressure) applied to the measurement electrode and the capacitance, the contact state between the measurement electrode and the skin surface (with one or two pieces of cotton interposed), and measurement. It is a graph which shows the result of having changed and measured the area (diameter 30mm, 60mm, 120mm) of an electrode (input signal: 1mV, sine wave of 10Hz, sampling frequency: 1kHz). From the graph, it can be seen that the larger the contact area and the contact pressure, the larger the capacitance, the smaller the cotton inserted between the measurement electrode and the skin surface.

In addition, what is necessary is just to obtain | require previously the correlation of an electrostatic capacitance, a contact area, and a contact pressure required when an estimation means estimates an electrostatic capacitance by experiment.
Further, according to claim 3, four or more unit electrodes used as any of the measurement electrodes and an electrode assignment for assigning the unit electrodes to any of the measurement electrodes according to a designated assignment setting And the estimation means may be configured as follows.

  That is, a pressure detection unit comprising a plurality of pressure sensors provided for each unit electrode is provided, and the effective sensor extraction unit is a pressure sensor constituting the pressure detection unit whose output is equal to or greater than a preset effective threshold value. Are divided as effective sensors, and the dividing means assigns each of the effective electrodes, which are unit electrodes corresponding to the effective sensors, to any of the measurement electrodes, and generates assignment settings for the electrode assignment means. Further, the contact information calculation means calculates, for each measurement electrode, the contact pressure between the measurement electrode and the subject based on the pressure detected by the effective sensor.

Then, the estimating means estimates the capacitance based on the contact pressure and unit electrode area calculated by the contact information calculating means.
According to the electrocardiographic waveform measuring apparatus of the present invention configured as described above, only the effective electrode that is reliably in contact with the subject is flexibly assigned to the measurement electrode according to the contact state between the unit electrode and the subject. Therefore, the reliability of the electrocardiographic signal measurement result can be further improved.

  The unit electrode used as the intermediate electrode is fixedly assigned, and the dividing unit divides the unit electrode other than the one assigned to the intermediate electrode into two to divide the pair of differential electrodes. It may be configured to be assigned to.

  Further, as described in claim 5, the unit electrode includes a priority electrode group preferentially assigned to the intermediate electrode and other normal electrode groups, and the dividing means includes both the priority electrode group and the normal electrode group. When the number of effective sensors included in these electrode groups is equal to or greater than a predetermined use threshold, the effective electrodes in the priority electrode group are assigned to the intermediate electrodes, and the effective electrodes in the normal electrode group are divided into two. When the number of effective sensors in one of the priority electrode group and the normal electrode group is equal to or greater than the use threshold, the effective electrode in the one electrode group is divided into three parts, You may be comprised so that it may allocate to an electrode and a pair of difference electrode.

  According to the electrocardiogram waveform measuring apparatus of the present invention configured as described above, the unit electrode can be assigned to the measurement electrode more flexibly according to the situation at the time, and a highly reliable electrocardiogram. The possibility of obtaining the measurement result of the issue can be further improved.

By the way, as described in claim 6, it is desirable that the dividing means divides the effective electrode so that the total capacity of each of them is substantially equal.
In this case, each measurement electrode has substantially the same capacitance, and two biological signals necessary for generating the electrocardiogram signal can be acquired under substantially the same conditions. Reliability can be further improved.

  According to a seventh aspect of the present invention, when the effective area formed by the effective electrode in the electrode group to be divided is vertically long, the dividing means is arranged in the vertical direction and the divided areas are arranged in the vertical direction. When the shape of the region is horizontally long, it is desirable to divide the effective electrode (assign it to each measurement electrode) so that the divided regions are aligned in the horizontal direction.

According to the electrocardiographic waveform measuring apparatus of the present invention configured as described above, it is possible to suppress the deviation of the contact pressure in each divided region, and it is possible to improve the estimation accuracy of the capacitance. .
Next, in the electrocardiogram waveform measuring apparatus according to claim 8, the electrocardiogram corrected by the correcting means based on the calculation result by the contact information calculating means or the estimation result by the estimating means. Determine the reliability of the issue.

  That is, when the capacitance of the measurement electrode is reduced to a certain degree or more, as shown in FIG. 17, the accuracy of the generated electrocardiogram signal is remarkably lowered, and when the contact area or the contact pressure is reduced to a certain degree or more, Since the capacity estimation accuracy itself is lowered, providing information indicating the reliability of the electrocardiogram signal as described above ensures the reliability of the device and the process using the electrocardiogram signal measured by the device. be able to.

  Specifically, the reliability determination means is, for example, a contact pressure calculated by the contact information calculation means or an effective sensor of any one of the measurement electrodes as described in claim 9. The reliability is low when the number is less than a preset lower limit value, or the capacitances of the pair of differential electrodes estimated by the estimation means are both less than a preset capacitance threshold value, or You may comprise so that it may determine with medium.

In addition, what multiplied the number of the effective sensors contained in the measurement electrode by the unit electrode area can be considered as a contact area where the subject and the measurement electrode are in effective contact.
Further, in the reliability determination means, for example, as described in claim 10, in any of the measurement electrodes, the contact pressure calculated by the contact information calculation means or the number of effective sensors is equal to or more than a lower limit, and You may comprise so that it may determine with reliability when the electrostatic capacitance of a pair of difference electrode estimated by the estimation means becomes more than a predetermined capacity | capacitance threshold value.

  Next, in the electrocardiographic waveform measuring apparatus according to claim 11, the contact state monitoring means obtains a difference value between the latest detection result of the pressure detection means and the previous detection result for each unit electrode, and the unit electrode The reliability of the electrocardiogram signal corrected by the correction means, assuming that the contact state between the measurement electrode and the subject is unstable when there is a difference value that is greater than or equal to a preset difference threshold value. It is judged that the degree is low, or the output of the electrocardiogram signal is prohibited.

According to the electrocardiogram waveform measuring apparatus of the present invention configured as described above, it is possible to ensure the reliability of the apparatus and the process using the electrocardiographic signal measured by the apparatus.
In addition, when the amplifier for amplifying the electrocardiogram signal generated by the electrocardiogram signal generation unit is provided as described in claim 12, the correction unit determines the amplification factor of the amplifier according to the estimation result of the estimation unit. It may be configured to correct the electrocardiogram signal by changing.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing an overall configuration of an electrocardiographic waveform measuring apparatus 1 according to the first embodiment to which the present invention is applied.

  The electrocardiographic waveform measuring apparatus 1 is a heart mounted on a vehicle, detects a potential signal (biological signal) emitted from a driver (subject) seated on a driving seat, and represents an electrocardiographic waveform based on the biological signal. Electric data DH is generated.

<Overall configuration>
As shown in FIG. 1, the electrocardiographic waveform measuring apparatus 1 includes a plurality (three in this embodiment) of measurement electrodes D1 to D3 provided for contact with a driver seated on a driving seat, and each measurement electrode. provided corresponding to the electrode D1 to D3, respectively it is n, the sum m (= 3n) signal detector 2 made of pieces of the pressure sensor _B 1 .about.B pressure sensors BG1~BG3 constituted by _m, the signal An electrocardiogram signal generation unit 3 that generates an electrocardiogram signal based on signals obtained from the measurement electrodes D1 to D3 constituting the detection unit 2, and an electrocardiogram signal generated by the electrocardiogram signal generation unit 3 are designated. The variable amplifier 4 that amplifies with the amplification factor A, the A / D converter 5 that converts the output of the variable amplifier 4 into digital data (hereinafter referred to as electrocardiographic data DH), and each pressure that constitutes the signal detector 2 based on a signal obtained from the sensor _B 1 .about.B _m , As well as specify the amplification factor A of the variable amplifier 4, and a correction control unit 6 for generating likelihood data DK indicating the reliability of the electrocardiograph data DH.

<Signal detection unit>
2A is an explanatory diagram showing the installation positions and usage states of the measurement electrodes D1 to D3 and the pressure sensor groups BG1 to BG3 constituting the signal detection unit 2, and FIG. 2B is an measurement electrode. D1 to D3, the pressure sensors BG1～BG3, is an explanatory view showing the positional relationship of the pressure sensor _B 1 ~B _m.

As shown in FIG. 2, the measurement electrode D1 is disposed on the upper portion of the backrest portion of the operation seat, the measurement electrode D2 is disposed on the lower portion of the backrest portion of the operation seat, and the measurement electrode D3 is disposed on the seat portion of the operation seat. In addition, n pressure sensors B _{1 to} B _n , B _{n + 1 to} B _2n , and B _{2n + i to} B _m are arranged in a matrix at equal intervals on the back surfaces of the measurement electrodes D1 to D3. A pressure sensor group BGi is provided.

  The measurement electrodes D1 and D2 positioned on the backrest portion of the driving seat are arranged so as to be positioned above and below the average heart position (height) of the driver seated on the driving seat. .

When the driver, who is the subject, sits on the driving seat, a capacitive coupling is formed between the measurement electrode Di and the human body across the clothes, and a biological signal emitted from the driver is detected via the measurement electrode Di. The Further, the pressure sensor B ₁ .about.B _m, the measurement electrodes Di for each site is divided into n in a matrix, pressure applied to the site is detected.

<Electrocardiogram signal generator>
As shown in FIG. 1, the electrocardiogram signal generation unit 3 includes voltage follower circuits 31 and 32 connected to measurement electrodes D1 and D2 (hereinafter also referred to as “difference electrodes”) and measurement electrodes D3 (hereinafter referred to as “differential electrodes”). A differential amplifier 33 that amplifies the difference between the voltage signals output from both voltage follower circuits 31 and 32, and an amplifier circuit 34 that amplifies the output of the differential amplifier 33. And a band-pass filter 35 for removing noise components from the output of the amplifier circuit 34.

That is, the electrocardiogram signal generator 3 generates a signal proportional to the potential difference between the differential electrodes D1 and D2 as an electrocardiogram signal.
<Correction control unit>
The correction control unit 6 includes an A / D converter 61 that converts detection signals (voltage levels) obtained from the pressure sensors B _{1 to} B _m into digital data (hereinafter referred to as “detection data”) VP _{1 to} VP _m , respectively. And an arithmetic processing unit 62 composed of a well-known microcomputer mainly composed of a CPU, a ROM, and a RAM.

Then, the arithmetic processing unit 62, a data acquisition process repeatedly acquiring detection data _VP 1 _{~VP m} via the A / D converter 61, detects the data _VP 1 _{~VP m} by the data acquisition process is acquired one way Every time, the amplification factor A of the variable amplifier 4 is set based on the detection data VP _{1 to} VP _m , and at least correction processing for generating accuracy data DK representing the reliability of the electrocardiogram data DH is executed.

<Correction process>
Next, correction processing executed by the arithmetic processing unit 62 will be described with reference to the flowchart shown in FIG.

When this processing is started, first, in S110, are acquired by the data acquisition process, the detection data _VP 1 _{~VP m} representing the voltage level is converted into pressure data _P 1 to P _m representing the pressure, in the subsequent S120, the pressure among the sensors _B 1 ~B _m, pressure data _{P k} extracts what the preset effective threshold Pth or more as an active sensor EB _k.

In S130, for each pressure sensor group BGi (i = 1,2,3), the contact area Si of the measuring electrode Di those obtained by counting the number of valid sensor EB _k belonging to the pressure sensor group BGi, effective sensor EB _k The average value of the pressure data _Pk detected in step 1 is calculated as the contact pressure PAi of the measurement electrode Di.

  In S140, it is determined whether or not the contact areas S1 to S3 of the respective measurement electrodes D1 to D3 are larger than a preset area lower limit value Sth (0 in the present embodiment). The area lower limit value Sth is not limited to 0, and may be set to, for example, the lower limit value of the contact area S that ensures the estimation accuracy when estimating the capacitance C described later (S150). .

If an affirmative determination is made in S140, the capacitances C1, C2 of the differential electrodes D1, D2 are estimated in S150 based on the contact areas S1, S2 and the contact pressures PA1, PA2.
Specifically, a conversion table generated from a graph (see FIG. 4A) obtained by experimentally measuring the relationship with the capacitance C using the contact area S and the contact pressure PA as parameters in advance. Use. The estimation method is not limited to this, and the relationship between S, PA, and C may be represented by a function from a graph, and C may be calculated by substituting S and PA into the function.

  In S160, it is determined whether or not both of the capacitances C1 and C2 estimated in S150 are equal to or larger than a preset capacitance threshold Cth. If an affirmative determination is made, the apparatus 1 in S170 The accuracy data DK indicating that the reliability of the generated electrocardiogram data DH is high is generated and output, and the process proceeds to S190. Note that the capacity threshold value Cth may be set to a lower limit value (about 4 nF in the figure) at which the actually measured value is substantially equal to the theoretical value based on the graph shown in FIG.

  On the other hand, if at least one of the capacitances C1 and C2 is smaller than the capacitance threshold Cth and a negative determination is made in S160, the reliability of the electrocardiogram data DH generated by the device 1 is medium in S180. The accuracy data DK indicating this is generated and output, and the process proceeds to S190.

  In S190, the amplification factor A of the variable amplifier 4 is set on the basis of the capacitances C1 and C2, and this process ends. Specifically, the amplification factor A is determined by using the graph shown in FIG. 4B and determining the amplification factor A from the average value of the capacitances C1 and C2. Note that the graph of FIG. 4B compensates for a decrease in the input / output ratio that occurs when the input / output ratio at the measurement electrode Di (see equation (1)) is constant, that is, the capacitance Ci is small. Set to

  If at least one of the contact areas S1 to S3 calculated in the previous S130 is smaller than the area lower limit value Sth and a negative determination is made in S140, the electrocardiographic data generated by the device 1 in S200. Accuracy data DK indicating that the reliability of DH is low is generated and output. In subsequent S210, the amplification factor A of the variable amplifier 4 is set to a predetermined default value, and this processing is terminated.

<Effect>
As described above, according to the electrocardiogram waveform measuring apparatus 1, the capacitances C1 to C3 between the measurement electrodes D1 to D3 and the subject are estimated, and the amplification factor of the variable amplifier 4 is based on the estimation result. Since the signal level of the electrocardiogram signal is corrected by setting A, it is reliable regardless of the contact state between the measurement electrodes D1 to D3 and the subject (and hence the variation in the size of the capacitances C1 to C3). It is possible to obtain a high-degree electrocardiographic signal measurement result.

  Further, in the electrocardiogram waveform measuring apparatus 1, when there is a contact area S1 to S3 having an area lower limit value Sth or less, the accuracy data DK indicating that the electrocardiographic data DH generated by the apparatus 1 has low reliability. When the contact areas S1 to S3 are all larger than the area lower limit value and the capacitances C1 and C2 of the differential electrodes D1 and D2 are both equal to or larger than the capacitance threshold Cth, the electrocardiographic data DH The accuracy data DK indicating that the reliability is high is generated. In other cases, the accuracy data DK indicating that the reliability of the electrocardiogram data DH is medium is generated.

Therefore, according to the electrocardiogram waveform measuring apparatus 1, by providing such accuracy data DK, it is possible to ensure the reliability of the apparatus and processing that use the electrocardiographic data DH generated by the apparatus 1.
[Second Embodiment]
Next, a second embodiment will be described.

FIG. 5 is a block diagram showing an overall configuration of the electrocardiogram waveform measuring apparatus 10 of the second embodiment, and FIG. 6 is an explanatory diagram showing a configuration of a part different from the electrocardiogram waveform measuring apparatus 1 of the first embodiment. is there.
The electrocardiogram waveform measurement apparatus 10 of the present embodiment is different from the electrocardiogram waveform measurement apparatus 1 of the first embodiment in the configuration of the signal detection unit 12 and the electrocardiogram signal generation unit 13, and the correction control unit 6a. The contents of the correction processing (see FIGS. 7 and 8) executed by the arithmetic processing unit 62a are different, and the only difference is that the switching signal X is output. Accordingly, this difference will be mainly described.

<Signal detection unit>
As shown in FIG. 5 and FIG. 6A, the signal detection unit 12 is provided with unit electrode groups DG1 and DG2 instead of the measurement electrodes D1 and D2 in the first embodiment. A measurement electrode D3 similar to that of the embodiment is provided.

The unit electrode groups DG1 and DG2 are configured by arranging _n unit electrodes DT _{1 to} DT _n and DT _{n + 1 to} DT _2n in a matrix.
The signal detection unit 12 is provided corresponding to each of the unit electrodes DT _{1 to} DT _2n constituting the unit electrode groups DG1 and DG2, and each includes n pressure sensors B _{1 to} B _2n in total. The pressure sensor groups BG1 and BG2 configured, and the pressure sensor group BG3 configured by n pressure sensors B _{2n + 1 to} B _m (m = 3n) arranged in a matrix on the measurement electrode D3 are provided. .

<Electrocardiogram signal generator>
Electrocardiographic signal generator 13, as shown in FIG. 5, the switching according to the signal X, the unit electrode group DG1, the unit electrodes constituting DG2 _DT 1 _{to DT} two electrode groups selected from among the _2n (measuring electrodes D1 , D2) is provided in the same manner as the electrocardiogram signal generator 3 of the first embodiment, except that it includes a switch circuit 36 that supplies the output from the voltage follower circuits 31 and 32, respectively. Yes.

As shown in FIG. 6B, the switch circuit 36 has an input terminal connected to any _{one of the} unit electrodes DT _{1 to} DT _2n , and two of the three output terminals are input to the voltage follower circuits 31 and 32, respectively. is connected to the end (shown by omitting the NC terminal in FIG. 6 (b)) the remaining one consists of unconnected (NC) to have been of 2n 1 input 3 output switch _SW 1 _{to SW 2n.}

Note that these switches SW _{1 to} SW _2n are all configured to be independently operable in accordance with the switching signal X, and an arbitrary number of units electrodes DT _{1 to} DT _2n are exclusively selected and measured. The electrodes D1 and D2 can be set.

<Correction process>
Next, correction processing executed by the arithmetic processing unit 62a will be described with reference to the flowchart shown in FIG. Note that the circle A symbol in the figure will be described in a third embodiment described later.

When this processing is started, first, in S310, are acquired by the data acquisition process, the detection data _VP 1 _{~VP m} representing the voltage level is converted into pressure data _P 1 to P _m representing the pressure, in the subsequent S320, S310 The pressure data P _i (i = 1 to m) converted at this time is expressed as P _i (t), and the pressure data P _i converted at the previous activation is expressed as P _i (t−1). ) To calculate the difference value ΔPi of the pressure data.

ΔP _i = P _i (t) −P _i (t−1) (4)
In subsequent S330, it is determined whether or not at least one of the difference values ΔP _{1 to} ΔP _m calculated in S320 is greater than or equal to a preset vibration determination threshold value THp. If a negative determination is made, vibration is determined. Is not generated, that is, the contact state between the subject and the unit electrode groups DG1 and DG2 and the measurement electrode D3 is stable, and the process proceeds to S340.

  In S340, it is determined whether or not vibration has occurred at the previous activation of this process (that is, negative determination is made in S330). If the determination is negative, that is, vibration has occurred even at the time of activation. However, if it is determined that the stable contact state continues, this processing is terminated as it is.

On the other hand, if an affirmative determination is obtained at S340, i.e., if it is determined to have changed to the stable contact state from an unstable contact state, at S350, the capacitance CT of the respective unit electrodes _DT 1 _{to DT 2n 1 to} CT _2n are calculated, and the process proceeds to S360. In this case, the area of the unit electrode DT _j (j = 1 to 2n) is defined as the contact area S, and the pressure data P _j detected by the pressure sensor B _j corresponding to the unit electrode DT _j is defined as the contact pressure P. Similarly to the case of S150, the capacitance CT _j is obtained using the conversion table.

In S360, in a unit electrode DT _j, the corresponding pressure sensor _{B j} at the detected pressure data _{P j} is what the preset effective threshold Pth or more, as an active electrode EDk (effective sensor EBk) Extract.

  In S370, the region on the unit electrode groups DG1 and DG2 formed by the effective electrode EDk (hereinafter referred to as “effective region”) is divided into two, and the two divided effective regions are defined as a pair of differential electrodes D1 and D2. Then, an effective area dividing process for assigning each effective electrode EDk to one of the pair of difference electrodes D1 and D2 is executed, and in subsequent S380, by generating the switching signal X based on the processing result in the effective area dividing process. The connection state of the switch circuit 36 is switched.

  In S390, it is determined whether or not the capacitances C1 and C2 of the two regions (that is, the measurement electrodes D1 and D2) divided in S370 are both equal to or greater than a preset capacitance threshold Cth. to decide. The capacitance Ci is calculated by adding the capacitances CTk of all the effective electrodes EDk constituting the measurement electrode Di.

  If both of the capacitances C1 and C2 are equal to or greater than the capacitance threshold Cth and an affirmative determination is made in S390, the reliability of the electrocardiographic data DH generated by the device 1 is high in S400. Is generated and output, and the process proceeds to S420.

  On the other hand, if at least one of the capacitances C1 and C2 is smaller than the capacitance threshold Cth and a negative determination is made in S390, the reliability of the electrocardiogram data DH generated by the device 1 is medium in S410. The accuracy data DK indicating the presence is generated and output, and the process proceeds to S420.

In S420, similar to S190 described above, the amplification factor A of the variable amplifier 4 is set based on the electrostatic capacitances C1 and C2, and this process is terminated.
If one or more of the pressure data difference values ΔP _{1 to} ΔP _m calculated in the previous S320 is greater than or equal to the vibration determination threshold THp and an affirmative determination is made in S330, then in S430, The accuracy data DK indicating that the reliability of the electrocardiogram data DH generated by the device 1 is low is generated and output, and in the subsequent S440, the amplification factor A of the variable amplifier 4 is defaulted as in S210 described above. Set to a value, and the process ends.

<Effective area division processing>
Next, the details of the effective electrode dividing process executed in S370 will be described with reference to the flowchart shown in FIG.

In this process, first, in S510, the size of the region formed by all the effective electrodes EDk is obtained. Specifically, the horizontal width W and the vertical width H along the arrangement direction of the unit electrodes BT _j are represented by how many effective electrodes EDk are arranged in the horizontal direction and the vertical direction.

  In subsequent S520, it is determined whether or not the horizontal width W is greater than or equal to the vertical width H. If an affirmative determination is made, in S530, the two regions are aligned in the horizontal direction and the total of the effective regions belonging to each region is determined. The effective area is divided so that the capacities are substantially equal, and this process is terminated.

  On the other hand, if a negative determination is made in S520, the effective area is divided so that the two areas are arranged in the vertical direction and the total capacity of the effective areas belonging to each area is substantially equal, and the present process is terminated.

FIG. 9 is an explanatory diagram showing a specific example when the effective area is divided.
Here, the unit electrode groups DG1 and DG2 are each composed of 21 (7 × 3) unit electrodes DT. Further, the hatched unit electrode is an effective electrode, and the number shown on the effective electrode represents the capacitance CT.

In the figure, (a) and (b) show the case where the effective area is horizontally long (W> H).
In this case, in each case, the two divided regions to be the measurement electrodes D1 and D2 are divided so as to be arranged in the horizontal direction, and the total capacitances C1 and C2 of the divided regions are C1 in (a). = 59, C2 = 58, and in (b), C1 = 29 and C2 = 27, which are almost equal.

  In the figure, (c) shows a case where the effective area is vertically long (W <H), and the two divided areas to be the measurement electrodes D1, D2 are divided so as to be aligned in the vertical direction. In addition, the total capacities C1 and C2 of the divided areas are C1 = 43 and C2 = 44.

  In the figure, (d) shows the case where the horizontal width and the vertical width are equal (W = H). As in the case of the horizontal length, the two divided regions to be the measurement electrodes D1 and D2 are in the horizontal direction. In addition, the total capacities C1 and C2 of the divided areas are C1 = 54 and C2 = 51.

<Effect>
As described above, in the electrocardiographic waveform measurement apparatus 10, by detecting the pressure applied to the unit electrodes DT ₁ to DT _2n, it extracts the effective electrode EDk in contact with a subject, the effective electrode EDk forms The measurement electrodes D1 and D2 are formed by dividing the effective region into two parts, and the capacitances C1 and C2 between the measurement electrodes D1 and D2 and the subject are estimated based on the result of estimation of the variable amplifier 4 By setting the amplification factor A, the signal level of the electrocardiogram signal is corrected.

Therefore, according to the electrocardiogram waveform measuring apparatus 10, a highly reliable electrocardiographic signal measurement result can be obtained regardless of the contact state between the unit electrode groups DG1 and DG2 and the subject.
Also, in the electrocardiogram waveform measuring apparatus 10, the latest pressure data P _j (t) detected via the corresponding pressure sensor B _j and the previous detection result P _j (t−1) for all the unit electrodes DT _j. a difference value [Delta] P _j with) determined, if the difference value [Delta] P _j exists that the vibration determination threshold THp above, as the state of contact between the unit electrode groups DG1, DG2 and the subject is unstable, The accuracy data DK indicating that the reliability of the electrocardiogram data DH generated by the device 10 is low is generated.

  Therefore, according to the electrocardiogram waveform measuring apparatus 10, by providing such accuracy data DK, it is possible to ensure the reliability of the apparatus and processing that use the electrocardiographic data DH generated by the apparatus 1.

  Further, in the electrocardiogram waveform measuring apparatus 10, when the effective region formed by the effective electrode EDk is divided, if the shape of the effective region is vertically long W <H, the divided region (and thus the measurement electrodes D1, D2). ) Are arranged in the vertical direction, and the shape of the effective area is horizontally long or the width and width are equal (W ≧ H), the divided areas are divided in the horizontal direction.

Therefore, according to the electrocardiogram waveform measuring apparatus 10, it is possible to suppress the bias of the contact pressure in each divided region, and it is possible to improve the estimation accuracy of the capacitances C1 and C2.
[Third Embodiment]
Next, a third embodiment will be described.

  FIG. 10 is a block diagram showing the overall configuration of the electrocardiogram waveform measuring apparatus 10a of the third embodiment, and FIGS. 11 and 12 show the configuration of parts different from the electrocardiogram waveform measuring apparatus 10 of the second embodiment. It is explanatory drawing.

  The electrocardiographic waveform measurement apparatus 10a of the present embodiment is different from the electrocardiographic waveform measurement apparatus 10 of the second embodiment in the configuration of the signal detection unit 12a (see FIG. 11) and the configuration of the electrocardiogram signal generation unit 13a (see FIG. 12) and the content of the correction processing (see FIG. 13) executed by the arithmetic processing unit 62 of the correction control unit 6 are different, and this difference will be mainly described.

<Signal detection unit>
As shown in FIGS. 10 and 11, the signal detection unit 12 a uses n unit electrodes DT _{2n + 1 to} DT _m (as in the unit electrode groups DG1 and DG2) instead of the measurement electrode D3 in the second embodiment. A unit electrode group DG3 configured by arranging m = 3n) in a matrix is provided.

The n pressure sensors B _{2n + 1 to} B _m constituting the pressure sensor group BG3 are provided corresponding to the unit electrodes DT _{2n + 1 to} DT _m constituting the unit electrode group DG3.
<Electrocardiogram signal generator>
Electrocardiograph signal generation unit 13a, as shown in FIG. 10, the switching according to the signal X, the three electrode groups selected from among unit electrode _DT 1 to DT _m constituting the unit electrode group DG1～DG3 (measurement electrode D1 ECG signal of the first embodiment except that it includes a switch circuit 36a that supplies outputs from the voltage follower circuits 31 and 32 as a reference potential of the differential amplifier 33, respectively. The configuration is the same as that of the generation unit 3.

As shown in FIG. 12, the switch circuit 36a has an input terminal connected to any _{one of the} unit electrodes DT _{1 to} DT _m , and three of the four output terminals are the input terminals of the voltage follower circuits 31 and 32, and the difference between them. connected to a reference potential input terminal of the dynamic amplifier 33, the remaining one consists of unconnected (N.C) to have been the m 1 inputs and four outputs switch _SW 1 to SW _m to (in FIG. 12 N.C terminal Abbreviated).

Note that these switches SW _{1 to} SW _m are all configured to be independently operable in accordance with the switching signal X, and any one of the unit electrodes DT _{1 to} DTm can be exclusively selected to measure electrodes. It can be set as D1 to D3.

<Correction process>
Next, correction processing arithmetic processing unit 62 executes, in the second embodiment, the unit electrode groups DG1, DG2 and the process running to the unit electrode _DT 1 _{to DT 2n,} the unit electrode group DG1~ DG3 and the point to be performed on the unit electrode _DT 1 to DT _m, the content of the effective area dividing process executed in S370, is different from the second embodiment.

<Effective area division processing>
Details of the effective electrode division processing will be described with reference to the flowchart shown in FIG. However, hereinafter, the unit electrode groups DG1 and DG2 are also referred to as an area AR1, and the unit electrode group DG3 is also referred to as an area AR2.

  In this process, first, in S610, it is determined whether or not the number of effective electrodes EDk belonging to the areas AR1 and AR2 (that is, the area of the effective region) is equal to or larger than a preset specified value. If the determination is affirmative, in S620, the effective area in the area AR1 is divided into two, and the divided areas are assigned to the measurement electrodes (a pair of differential electrodes) D1 and D2, and the area AR2 (that is, The effective area in the unit electrode group DG3) is assigned to the measurement electrode (intermediate electrode) D3, and this process is terminated.

  If a negative determination is made in S610, it is determined in S630 whether or not the number of effective electrodes EDk belonging to the areas AR1 and AR2 is less than a specified value in both areas AR1 and AR2. In such a case, the process exits from this process and proceeds to S430.

  On the other hand, when a negative determination is made in S630, that is, when one of the areas AR1 and AR2 has the number of effective electrodes EDk equal to or greater than a specified value, the other has a number of effective electrodes EDk that is less than the specified value. , S640 divides the effective area in the area where the number of effective electrodes EDk is equal to or greater than the specified value into three, and divides the divided areas into measurement electrodes (a pair of differential electrodes and intermediate electrodes) D1 to D3. This processing is terminated.

  Note that, when the effective area in the area AR1 is divided into two in S620, the same process as the effective area dividing process of the second embodiment is executed. On the other hand, when the effective electrode is divided into three at S640, for example, as shown in FIGS. 14 (a) and 14 (b), when the shape of the effective region is horizontally long, or as shown in FIG. 14 (d). When the horizontal width and the vertical width of the effective area are equal, the divided areas (and thus the measurement electrodes D1 to D3) are arranged in the horizontal direction, and the shape of the effective area is vertically long as shown in FIG. In some cases, it may be divided so that the divided areas are arranged in the vertical direction.

  Further, as shown in FIG. 15, the effective region of the lower one of the effective regions is assigned to the measurement electrode (intermediate electrode) D3, and the remaining 2/3 effective regions are in accordance with the horizontal width and the vertical width. Then, the remaining 2/3 effective area is subdivided in the horizontal direction or the vertical direction, and the subdivided effective area is allocated to the measurement electrodes (a pair of differential electrodes) D1 and D2. Good. 15A to 15D are divided so that the re-divided areas are all aligned in the horizontal direction.

Furthermore, when the effective area is divided, it is desirable to divide the total capacity C1 to C3 in each of the divided areas so that they are almost equal.
<Effect>
As described above, in the electrocardiogram waveform measuring apparatus 10a, not only the measurement electrodes D1 and D2 used as a pair of differential electrodes but also the measurement electrode D3 used as an intermediate electrode is configured by the effective electrode EDk. Therefore, even if the contact state between the unit electrode groups DG1 to DG3 and the subject changes variously, it is possible to respond more flexibly and have high reliability. The possibility that the electrocardiogram data DH can be generated can be increased.
[Other Embodiments]
In the above embodiment, when it is determined that the reliability of the electrocardiogram data DH is low, the generation and output (S200, S430) of the accuracy data DK representing that fact, the connection of the switch circuits 36 and 36a, and the amplification of the variable amplifier 4 Although the rate A is set to the default setting (S210, S440), in such a case, the output of the electrocardiographic data DH itself may be prohibited.

  In the first embodiment, whether or not the reliability of the electrocardiographic data is low is determined using the contact areas S1 to S3, but may be performed using the contact pressures PA1 to PA3.

The block diagram which shows the structure of the electrocardiogram waveform measuring apparatus of 1st Embodiment. Explanatory drawing which shows arrangement | positioning of the electrode for a measurement, and the positional relationship of the electrode for a measurement and a pressure sensor. The flowchart which shows the content of the correction process which sets the gain of an electrocardiogram signal based on the detection result in a pressure sensor. The graph which shows the content of the table used for the estimation of an electrostatic capacitance, and the setting of an amplification factor. The block diagram which shows the structure of the electrocardiogram waveform measuring apparatus of 2nd Embodiment. Explanatory drawing which shows the detail of a signal detection part and a switch circuit. The flowchart which shows the content of the correction process in 2nd Embodiment. The flowchart which shows the content of the effective area | region division | segmentation process performed within a correction process. Explanatory drawing which shows the specific operation example based on an effective area | region division | segmentation process. The block diagram which shows the structure of the electrocardiogram waveform measuring apparatus of 3rd Embodiment. Explanatory drawing which shows the detail of a signal detection part. The circuit diagram which shows the detail of a switch circuit. The flowchart which shows the content of the effective area | region division process. Explanatory drawing which shows the specific operation example based on an effective area | region division | segmentation process. Explanatory drawing which shows the specific operation example based on an effective area | region division | segmentation process. The circuit diagram which shows the equivalent circuit in the electrode for a measurement of an electrocardiogram waveform measuring device. The graph of the theoretical value and actual value which show the relationship between the electrostatic capacitance in a measurement electrode, and an input-output ratio. The graph which shows the influence which the contact state (a contact pressure, an electrode area, and an insertion object) with a measurement electrode and a test subject has on electrostatic capacity.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 10, 10a ... Electrocardiogram waveform measuring device 2, 12, 12a ... Signal detection part 3, 13, 13a ... Electrocardiogram signal generation part 4 ... Variable amplifier 5, 61 ... A / D converter 6, 6a ... Correction control Units 31, 32 ... Voltage follower circuit 33 ... Differential amplifier 34 ... Amplifier circuit 35 ... Bandpass filter 36,36a ... Switch circuit 62,62a ... Operation processing unit

Claims (12)

Three measuring electrodes consisting of an intermediate electrode and a pair of differential electrodes located in the seat or in contact with the subject seated on the seat;
An electrocardiogram signal generating means for generating a signal indicating a potential difference between the pair of differential electrodes as an electrocardiogram signal, using the potential of the intermediate electrode as a reference potential;
For each measurement electrode, an estimation means for estimating the capacitance between the measurement electrode and the subject;
Based on the estimation result of the previous Ki推 constant means, and correcting means for correcting the signal level of the electrocardiographic signal generated by the electrocardiograph signal generating means,
An electrocardiographic waveform measuring apparatus comprising: Each of the measurement electrodes comprises a single unit electrode,
The estimation means includes
A pressure detection means comprising a plurality of pressure sensors respectively provided at a plurality of sites of the measurement electrode for each of the measurement electrodes;
Effective sensor extraction means for extracting, as an effective sensor, an output whose output is equal to or greater than a preset effective threshold value among the pressure sensors constituting the pressure detection means;
For each measurement electrode, the contact area between the measurement electrode and the subject is calculated based on the number of effective sensors, and the contact pressure between the measurement electrode and the subject is calculated using the effective sensor. Contact information calculation means for calculating based on the detected pressure;
The electrocardiographic waveform measurement apparatus according to claim 1, wherein the capacitance is estimated based on the contact area and the contact pressure calculated by the contact information calculation unit. Four or more unit electrodes used as any of the measurement electrodes;
An electrode assigning means for assigning the unit electrode to one of the measurement electrodes according to a designated assignment setting;
With
The estimation means includes
Pressure detecting means comprising a plurality of pressure sensors provided for each unit electrode;
Effective sensor extraction means for extracting, as an effective sensor, an output whose output is equal to or greater than a preset effective threshold value among the pressure sensors constituting the pressure detection means;
Each of the effective electrodes, which are unit electrodes corresponding to the effective sensor, is allocated to any of the measurement electrodes, and a dividing unit that generates the allocation setting for the electrode allocation unit,
Contact information calculation means for calculating a contact pressure between the measurement electrode and the subject based on a detection pressure of the effective sensor for each measurement electrode;
The electrocardiographic waveform measurement apparatus according to claim 1, wherein the capacitance is estimated based on the contact pressure and unit electrode area calculated by the contact information calculation unit. The unit electrode used as the intermediate electrode is fixedly assigned,
The electrocardiographic waveform measuring apparatus according to claim 3, wherein the dividing unit divides a unit electrode other than that assigned to the intermediate electrode into two and assigns the unit electrode to the pair of differential electrodes. The unit electrode is composed of a priority electrode group that is preferentially assigned to the intermediate electrode, and other normal electrode groups,
The dividing means includes
In both the priority electrode group and the normal electrode group, when the number of the effective sensors included in the electrode group is equal to or greater than a predetermined use threshold, the effective electrode in the priority electrode group is assigned to the intermediate electrode. The effective electrode in the normal electrode group is divided into two and assigned to the pair of differential electrodes, and only one of the priority electrode group and the normal electrode group has the number of effective sensors equal to or greater than the use threshold value. The electrocardiographic waveform measurement apparatus according to claim 3, wherein an effective electrode in one of the electrode groups is divided into three and assigned to the intermediate electrode and the pair of differential electrodes.   6. The electrocardiogram waveform measuring apparatus according to claim 3, wherein the dividing unit divides the effective electrode so that the total capacity of each of the dividing means is substantially equal.   When the effective area formed by the effective electrode in the electrode group to be divided is vertically long, the dividing means is arranged in the vertical direction, and when the effective area is horizontally long The electrocardiographic waveform measurement apparatus according to claim 3, wherein the effective electrode is divided so that the divided regions are arranged in a horizontal direction.   A reliability determination unit that determines the reliability of the electrocardiogram signal corrected by the correction unit based on a calculation result of the contact information calculation unit or an estimation result of the estimation unit is provided. The electrocardiographic waveform measurement apparatus according to any one of Items 2 to 7.   The reliability determination means is any one of the measurement electrodes, and the contact pressure calculated by the contact information calculation means or the number of effective sensors is less than a preset lower limit value. Alternatively, when both of the capacitances of the pair of differential electrodes estimated by the estimation unit are less than a preset capacitance threshold, it is determined that the reliability is low or medium. The electrocardiographic waveform measuring apparatus according to claim 8. In the reliability determination means, any of the measurement electrodes has the contact pressure calculated by the contact information calculation means or the number of effective sensors equal to or greater than the lower limit value, and is estimated by the estimation means. both the capacitance of the pair of differential electrodes is, when the preset volume threshold above, the electrocardiographic waveform according to 請 Motomeko 9 shall be the determining means determines that the reliability is high Measuring device.   For each unit electrode, a difference value between the latest detection result in the pressure detection means and the previous detection result is obtained, and there is a unit electrode in which the difference value is greater than or equal to a preset difference threshold value. If the contact state between the measurement electrode and the subject is unstable, it is determined that the reliability of the electrocardiogram signal corrected by the correction means is low, or the output of the electrocardiogram signal is The electrocardiographic waveform measuring apparatus according to claim 2, further comprising a contact state monitoring unit that performs prohibition. An amplifier for amplifying the electrocardiogram signal generated by the electrocardiogram signal generation means;
12. The correction unit according to claim 1, wherein the correction unit corrects the electrocardiogram signal by changing an amplification factor of the amplifier according to an estimation result of the estimation unit. ECG waveform measuring device.