JP2009261419A - Biological state estimating device, program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biological state estimating device highly accurately estimating a biological state even in a situation that it is difficult to highly accurately estimate the biological state while driving or the like, for instance. <P>SOLUTION: In a step 200, whether an electrocardiographic sensor 1 and the hand of a driver are in contact with each other is decided. In a step 210, whether or not a heartbeat interval calculated from an electrocardiographic waveform is within a prescribed range is decided. When decided that the contact state with the electrocardiographic sensor 1 is not appropriate in the step 200 or when decided that the data of the heartbeat interval are abnormal in the step 210, whether or not a pulse wave sensor 3 and the hand of the driver are in contact with each other is decided in a step 230. In a step 240, whether or not a pulse wave interval calculated from a pulse wave waveform is within a prescribed range is decided. In a step 250, since a pulse interval is normal, the heartbeat interval is interpolated using the pulse rate interval, and the heartbeat interval is output to a storage device 17 and a display device 19. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biological state estimation device, a program, and a recording medium that are mounted on a vehicle and can estimate the state of a biological body such as a driver.

  Conventionally, as a method for estimating the state of a driver during driving, a technique for measuring the driver's heart rate and determining the state of the driver from the change in the heart rate has been proposed (see Patent Document 1). In this technique, in order to accurately detect the heart rate from the electrocardiogram signal, the heart rate data is checked based on the state of the heart rate interval.

In addition, in order to determine the patient's heart rate and heart rate interval in the medical field, a technique using a pulse wave as an alternative to an electrocardiogram has been proposed (see Patent Document 2). . In this technique, the pulse wave R-R interval obtained by the pulse wave sensor is regarded as equivalent to the heart beat interval, and the heart beat interval is obtained.
JP-A-6-22914 JP-A-8-229013

  An electrocardiogram signal can be detected by applying an electrode to the skin and amplifying the potential difference between the two electrodes. For example, in the case of measurement by a sensor in which electrodes are embedded on the left and right of the steering, At the time of measurement, the electrocardiogram waveform may become unstable, and the heart rate interval, which is the time interval between the electrocardiogram R wave and the electrocardiogram R wave, and thus the biometric index that can be calculated from it, such as the heart rate and fluctuation, There also arises a problem that it becomes difficult to calculate the fluctuation value of the heartbeat interval shown.

In such a case, the technique of Patent Document 1 interpolates with the intermediate value of the normal heartbeat interval data before and after, but there is a problem that an error occurs with an unfounded interpolation value.
In the technique of Patent Document 2, the phase difference between the electrocardiogram signal and the pulse wave signal changes depending on the state of the user such as blood pressure and blood vessels, so the pulse interval and the heart beat interval cannot be said to be completely 1: 1. There is a problem that the error is not taken into consideration. In other words, when measuring in various environments every day, it is necessary to consider the difference. However, at present, the pulse interval is merely used as a replacement (replacement) of the heart rate interval, and therefore the error Without considering the above, it is not appropriate to display the fluctuation value of the heartbeat interval or to estimate the state of the subject.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a biological state estimation apparatus that can accurately detect a heartbeat interval.

  (1) The invention of claim 1 estimates the state of the living body based on the electrocardiographic waveform of the living body obtained by the electrocardiographic waveform acquiring means and the pulse wave waveform of the living body obtained by the pulse wave waveform acquiring means. And a measurement state determination unit that determines whether or not the electrocardiogram waveform is not suitable for detecting a heartbeat, and the measurement state determination unit determines whether the electrocardiogram waveform is a heartbeat. Interpolation means for interpolating the electrocardiographic waveform using the pulse wave waveform when it is determined that the state is not appropriate for detection is provided.

  In the present invention, it is determined whether or not the electrocardiogram waveform is not suitable for detecting a heartbeat. When it is determined that the electrocardiogram waveform is not suitable for detecting a heartbeat, Interpolate ECG waveform using wave waveform.

  Accordingly, even when an electrocardiogram waveform preferable for detecting a heartbeat cannot be obtained, the heartbeat interval can always be detected with high accuracy. Therefore, since the heart rate and the index indicating the fluctuation amount of the heart rate interval can be calculated using this heart rate interval, the state of the living body can be accurately estimated using these indexes.

  Here, examples of the state in which the electrocardiogram waveform is not appropriate for detecting the heartbeat include a case where the sensor is not sufficiently worn (such as non-contact of electrodes) and a case where noise is generated due to vehicle vibration or the like. . That is, in such a state, an electrocardiographic waveform necessary for obtaining an accurate heartbeat interval may not be obtained.

  (2) In the invention of claim 2, the measurement state determination means detects a contact state between the electrocardiogram waveform acquisition means and the living body or a contact state between the pulse wave waveform acquisition means and the living body. Based on the signal from the means, it is determined whether or not the state is suitable for heartbeat detection.

  For example, when an electrocardiographic waveform acquisition means such as an electrocardiographic sensor is not properly attached to a living body (for example, when it is not in contact with an electrode), an accurate electrocardiographic waveform cannot be obtained. Therefore, by detecting the contact state between the electrocardiogram waveform acquisition means and the living body using a contact state detection means such as a contact impedance sensor, it is possible to determine whether or not the state is suitable for heartbeat detection.

  Similarly, when a pulse wave waveform acquisition unit such as a pulse wave sensor is not properly attached to the living body (for example, when there is a gap between the sensor and the sensor), an accurate pulse wave waveform cannot be obtained. Therefore, by detecting the contact state between the pulse wave waveform acquisition means and the living body using a contact state detection means such as a pressure sensor, it can be determined whether or not the state is suitable for detecting a pulse.

(3) The invention according to claim 3 is characterized in that the measurement state determination means determines whether or not the heartbeat interval is suitable for detection of a heartbeat depending on whether or not the heartbeat interval is out of a predetermined allowable range.
If the heart rate interval is too large or too small to be normal, it may be caused by, for example, a sensor installation error or noise, so in such a case, it is not suitable for heart rate detection. Is determined. Thereby, it is possible to accurately determine whether or not the state is suitable for heartbeat detection.

(4) The invention of claim 4 is characterized in that the interpolation means interpolates a heartbeat interval with a pulse interval.
For example, a heartbeat interval obtained by an electrocardiographic sensor and a pulse interval obtained by a pulse wave sensor, for example, are not perfect as shown in FIG. A period during which a high ECG interval cannot be obtained can be interpolated using the pulse wave interval.

  (5) In the invention of claim 5, the interpolating means obtains a pulse interval using a feature point of any one of a pulse waveform, a first-order differential waveform of the pulse wave, and a second-order differential waveform of the waveform, It is characterized by interpolating the heartbeat interval using the interval.

  The pulse interval is a characteristic point indicating a peak or the like repeatedly appearing in the waveform for each pulse, that is, a characteristic point of the pulse wave waveform (for example, a well-known traveling wave peak P1 or the like) or a characteristic point of the first-order differential waveform of the pulse wave. (For example, a1 of the velocity pulse wave) or a feature point of the second-order differential waveform of the waveform (for example, a of the acceleration pulse wave) can be used for calculation.

(6) The invention of claim 6 is characterized in that the interpolation means interpolates as it is, using the latest pulse interval corresponding to the heartbeat interval.
The present invention exemplifies an interpolation method. In the present invention, as shown in FIG. 5 to be described later, interpolation is performed as it is using the latest pulse interval corresponding to a heart rate interval with low accuracy. Thereby, the heartbeat interval can be accurately interpolated by a simple method.

(7) In the invention of claim 7,
The interpolation means includes a time difference between any one of the characteristic points of the previous electrocardiogram R wave and the previous pulse waveform, the first-order differential waveform of the pulse wave, and the second-order differential waveform of the waveform, the current pulse waveform, The current ECG R-wave position is estimated from the position of one of the characteristic points of the first-order differential waveform of the pulse wave and the second-order differential waveform of the waveform, and the estimated current ECG R-wave position and the previous The time interval with the electrocardiogram R wave is interpolated as a heartbeat interval.

The present invention exemplifies an interpolation method. In the present invention, the heart rate interval can be interpolated in consideration of the deviation of the pulse wave waveform as shown in FIG.
(8) The invention of claim 8 is characterized in that at least one of an index indicating a heart rate and a fluctuation amount of the heart beat interval is calculated from the interpolated heart beat interval.

In the present invention, by using the interpolated heartbeat interval, it is possible to calculate an index indicating the heart rate and the fluctuation amount of the heartbeat interval with high accuracy.
Note that, as an index indicating the fluctuation amount of the heartbeat interval (an index indicating so-called heart rate fluctuation), for example, a well-known high-frequency component (HF) or low-frequency component of fluctuation (obtained by frequency analysis of heart rate fluctuation) (LF), the ratio of the components (LF / HF), and the like.

  (9) In the invention of claim 9, when calculating at least one of the indices indicating the fluctuation amount of the heart rate and the heartbeat interval, at least one of the number of interpolations, the number of consecutive interpolations, and the ratio of interpolations. According to the species, the reliability indicating the reliability of the data is calculated.

The fact that there is a lot of interpolation means that a preferable heartbeat waveform has not been obtained. Therefore, in order to show the reliability of data, the reliability corresponding to the state of interpolation is calculated.
Here, the number of interpolations is the number of times of interpolation, and the continuous number of interpolations is the number of continuous interpolations among the number of times of interpolation. This is the ratio of the number of times of interpolation among the heart rate (or pulse wave number) in a predetermined period.

(10) The invention of claim 10 is characterized in that the reliability decreases as the number of interpolations, the number of consecutive interpolations, and the ratio of interpolation all increase.
Since it is considered that the more the number of interpolations, the more the interpolation is performed continuously, or the more the interpolation rate, the lower the reliability of the data, the present invention makes such a setting.

(11) The invention of claim 11 is characterized in that at least one of the heart rate, the index indicating the fluctuation amount of the heartbeat interval, and the reliability is displayed.
In the present invention, an index indicating the amount of fluctuation of the heart rate and the heart rate interval and the reliability are displayed on a display or the like. In addition, you may alert | report with an audio | voice etc.

(12) The invention of claim 12 is characterized in that the state of the user is determined from at least two of the interpolated heart rate, the index indicating the fluctuation amount of the heartbeat interval, and the reliability.
In the present invention, when the state of the driver or the like (for example, the state of arrhythmia or the like) is determined, the state determination can be performed with high accuracy because the index and the reliability indicating the fluctuation amount of the heart rate and the heartbeat interval are used.

(13) The invention of claim 13 is characterized in that, in determining the state of the user, a threshold value for determination is switched according to the reliability.
For example, when the reliability is low, the reliability of the data is low. Therefore, compared with the case where the state determination is performed with an index indicating the fluctuation amount of the heart rate or the heartbeat interval as usual, the criterion for determining, for example, an abnormality is used. By making it high (making it difficult to determine that there is an abnormality), it is possible to prevent erroneous determination.

(14) The invention according to claim 14 is characterized in that, when the state of the user is determined, the weight of data used for the determination is changed according to the reliability.
The data used for determination includes high reliability and low data. For example, even if the number of interpolations is the same, the reliability differs depending on whether or not the interpolation is continuous. Therefore, for example, when the reliability is low, it is possible to prevent erroneous determination as in the invention of the thirteenth aspect by weighting the data so that it is difficult to determine abnormality.

(15) In the invention of claim 15, when determining the state of the user, at least the determination result is displayed among the determination result and the reliability.
In the present invention, since the determination result and the reliability are displayed on, for example, a display, the driver or the like can recognize its own state from the display.

(16) The invention of claim 16 is characterized in that the display content is displayed only when the reliability is equal to or higher than a predetermined level.
When the reliability is low, even if the determination result or the like is displayed, it only gives anxiety to the driver or the like. Therefore, only the data having a high degree of necessity is displayed.

(17) The invention according to claim 17 is characterized in that when the reliability is lowered, a warning about the lowered reliability is given.
By giving a warning when the reliability is lowered, for example, the driver or the like can check the sensor mounting state or the like.

  (18) The invention of claim 18 is characterized in that it is determined from the mounting state determination unit whether the mounting state of the pulse wave waveform acquisition unit is good, and the interpolation process is executed only when it is good.

  For example, when the mounting state of the pulse wave sensor is bad, the pulse wave waveform obtained from the pulse wave sensor is not highly accurate. Therefore, interpolation based on the pulse wave waveform is performed only when the mounted state of the pulse wave sensor or the like is good.

(19) The invention of claim 19 is characterized in that the estimation of the biological state is executed for a driver in a vehicle.
The present invention exemplifies a biological state estimation target.

(20) The invention of claim 20 is characterized in that the reliability is calculated by combining vehicle information.
For example, when the vehicle is traveling on a curve or traveling at a high speed, the sensor mounting state may be deteriorated or noise may be increased. Therefore, it is desirable to set the reliability corresponding to the vehicle state.

  (21) In the invention of claim 21, the state of the driver is determined from at least two of the interpolated heart rate, the index indicating the fluctuation amount of the heartbeat interval, and the reliability, and vehicle information. It is characterized by.

  As described above, since the state of a signal obtained from a sensor or the like changes depending on the state of the vehicle, it is preferable to determine the state of the driver in consideration of not only biological information but also vehicle information (for example, vehicle speed and steering angle). .

(22) The invention according to claim 22 is characterized in that the vehicle is controlled based on the determination result of the state of the driver.
For example, when the driver's state becomes unfavorable for driving (for example, when an arrhythmia occurs) or the like, the fact is memorized or notified (for example, displayed on the display or by voice) . It also controls the running state of the vehicle. Specifically, control for prohibiting acceleration, gradually decreasing the speed, or blinking the hazard lamp may be performed.

(23) The invention of claim 23 is characterized in that at least one of the estimation result of the biological state and the warning content is displayed using the navigation device of the vehicle.
Since the navigation apparatus is equipped with a display, the determination result and warning are displayed using this display. In addition, you may alert | report with an audio | voice etc.

(24) The invention of claim 24 is a program for realizing the function of the biological state estimating apparatus according to any one of claims 1 to 23.
Therefore, by executing this program with a microcomputer or the like, it is possible to perform an interpolation process, an index calculation process, a biological state estimation process, and the like.

(25) The invention of claim 25 is a computer-readable recording medium on which the program according to claim 24 is recorded.
Therefore, using the program recorded on the recording medium, interpolation processing, calculation processing such as an index, biological state estimation processing, and the like can be performed.

Next, the best mode (embodiment) of the present invention will be described.
[First Embodiment]
In the present embodiment, a biological state estimation apparatus that is mounted on an automobile and measures a driver's heartbeat interval and the like and evaluates the state of the driver based on the measurement result and the like will be described.

a) First, the system configuration of the biological state estimation apparatus of this embodiment will be described based on the block diagram of FIG.
As shown in FIG. 1, the biological state estimating apparatus 1 of the present embodiment includes an electrocardiographic sensor 1, a pulse wave sensor 3, an electrocardiographic amplifier 5, a pulse wave amplifier 7, and an electrocardiographic sensor contact sensor 9. The contact sensor 11 for pulse wave sensors, the vehicle sensor 13, the electronic control apparatus 15, the memory | storage device 17, the display apparatus 19, and the communication apparatus 21 are provided.

  Among these, the electronic control device 15 includes an electrocardiogram waveform acquisition unit 23, a pulse wave waveform acquisition unit 25, an operation state determination unit 27, a signal processing calculation unit 29, a driver state determination unit 31, and a vehicle control unit. 33.

Each configuration will be described below.
The electrocardiogram sensor 1 is an electrocardiogram waveform acquisition means for acquiring an electrocardiogram waveform. As shown in FIG. 2, a pair of electrodes 35 and 37 for measuring an electrocardiogram steer the vehicle. The main body (electric circuit or the like: not shown) of the electrocardiographic sensor 1 is embedded in the steering 39. Here, the reason why the electrodes 35 and 37 are arranged on the surface of the steering 39 is to ensure that the electrodes 35 and 37 are in contact with the left and right hands of the driver. The electrocardiographic sensor 1 transmits a signal related to the collected electrocardiographic waveform to the electrocardiographic amplifier 5. The main body of the electrocardiographic sensor 1 may be disposed inside the steering column 41 or the dashboard (not shown).

  The pulse wave sensor 3 is a pulse wave waveform acquisition means for calculating a blood pressure and a pulse rate from the blood flow of the finger using a photoelectric element. Like the electrocardiographic sensor 1, the pulse wave sensor 3 is a part of the belly of the driver's finger. The measurement unit 43 is disposed on the surface of the steering 39 so as to make sure that the measurement unit 43 (which transmits and receives light) is in contact with the main body (electric circuit, etc .: not shown) of the steering 39. Embedded inside. The pulse wave sensor 3 transmits a signal relating to the collected pulse and blood pressure to the pulse wave amplifier 7. The pulse wave sensor 3 may be mounted so as to be wrapped around the wrist of the driver and measure the pulse and blood pressure using a piezoelectric element.

  The electrocardiographic amplifier 5 and the pulse wave amplifier 7 are devices for amplifying signals received from the electrocardiographic sensor 1 and the pulse wave sensor 3, respectively. The electrocardiographic amplifier 5 and the pulse wave amplifier 7 transmit the amplified signals to the electrocardiographic waveform acquisition unit 23 and the pulse wave waveform acquisition unit 25, respectively.

  The electrocardiographic sensor contact sensor 9 is a sensor for identifying whether or not the electrocardiographic sensor 1 is in contact with the skin (for example, a contact impedance measuring sensor having a pair of electrodes), and is integrated with or attached to the electrocardiographic sensor 1. Has been.

  For example, as shown in FIG. 2, one confirmation electrode of the right-hand contact impedance measurement sensor is shared with one electrode 35 of the electrocardiographic sensor 1, and the other confirmation electrode 45 is adjacent to the electrode 35. Has been placed. In this case, when the right hand contacts the right electrode 35 and the confirmation electrode 45 of the steering wheel, the right hand is connected to one electrode 35 of the electrocardiographic sensor 1 by obtaining the impedance between the electrode 35 and the confirmation electrode 45. It can be determined that they are in contact. Similarly, one confirmation electrode of the left contact impedance measurement sensor is shared with one electrode 37 of the electrocardiographic sensor 1, and the other confirmation electrode 46 is disposed adjacent to the electrode 37.

  The pulse wave sensor contact sensor 11 is a sensor (for example, a pressure sensor) for identifying whether or not the pulse wave sensor 3 is in contact with the skin, and is integrated with or attached to the pulse wave sensor 3. For example, the pressure sensor 47 of the pressure sensor is disposed adjacent to the measurement unit 43 of the pulse wave sensor 3.

  The vehicle sensor 13 is a sensor that detects various vehicle states such as a vehicle running state, such as a vehicle speed sensor, a steering angle sensor, a throttle opening sensor, and a brake sensor (not shown).

  The storage device 17 is composed of, for example, a hard disk and stores various data such as measured heartbeat intervals. In the storage device 17, when the vehicle control unit 33 determines that data storage is necessary, the electrocardiogram waveform, the pulse wave waveform, and the signal acquired by the electrocardiogram waveform acquisition unit 6 and the pulse wave waveform acquisition unit 7. The heartbeat interval calculated by the processing calculation unit 29, an index indicating the fluctuation amount of the heartbeat interval, the driver state estimation result determined by the driver state determination unit 31, and the like are stored.

  The display device 19 is an in-vehicle display device used for a navigation device such as an LCD (Liquid Crystal Display) or an organic EL (Electroluminescence) display. As will be described later, the display device 19 displays a heart rate, a driver state estimation result, a reliability of the result, and the like. In some cases, a warning message is displayed on the screen to stop the vehicle, a voice message is issued from an attached speaker, or a warning lamp such as an LED (Light Emitting Diode) is blinked.

  The communication device 21 is a device for performing communication with the outside. In response to a command from the electronic control device 15, the communication device 21 issues a warning to a pre-registered contact information such as a medical institution or first aid, or displays vehicle position information. Used to communicate.

b) Next, the electronic control unit 15 will be described.
The electronic control unit 15 is a control unit having a known microcomputer as a main part, and receives signals from the electrocardiographic sensor 1, the pulse wave sensor 3, the vehicle sensor 13, and the like, and the signals are converted into the electrocardiographic waveform. The acquisition unit 23, the pulse wave waveform acquisition unit 25, the driving state determination unit 27, the signal processing calculation unit 29, and the driver state determination unit 31 perform processing. According to the processing results, the storage device 17, the display device 19, and A control signal is output to the communication device 21.

Hereinafter, each function of the electronic control unit 15 will be described.
The electrocardiographic waveform acquisition unit 23 acquires the electrocardiographic waveform amplified by the electrocardiographic amplifier 5. Similarly, the pulse wave waveform acquisition unit 25 acquires the pulse wave waveform amplified by the pulse wave amplifier 7.

Here, an electrocardiogram waveform (electrocardiogram waveform) will be described with reference to FIG.
The electrocardiogram mainly includes a P wave reflecting the electrical excitement of the atrium, a Q wave, an R wave, and an S wave (hereinafter referred to as “QRS group”) reflecting the electrical excitation of the ventricle, and excitement. And a T wave reflecting the process of repolarization of the ventricular cardiomyocytes.

  Among these, the wave height (potential difference) of the R wave is the largest, and it can be said that it is the most robust against noise such as myoelectric potential. Next, the wave height is the T wave, and the P wave has the smallest wave height. Among the electrocardiographic waveforms, the interval between the R wave peak and the R wave peak is called a heartbeat interval (RRI), and the heart rate can be calculated by multiplying the reciprocal of the heartbeat interval by 60.

Furthermore, it is possible to evaluate a person's condition from the fluctuation amount of the heartbeat interval. As an index indicating the fluctuation amount of the heartbeat interval, for example, it is said that the amount of autonomic nerve activity can be evaluated by frequency analysis of the heartbeat interval. Specifically, the high frequency component HF (0.15 to 0.4 Hz) reflects the amount of parasympathetic nerve activity, and the ratio of the low frequency component LF (0.04 to 0.15 Hz) and the high frequency component (LF / HF). Is said to reflect the amount of sympathetic nerve activity. In addition, the standard deviation SD of the heartbeat interval in an arbitrary time zone, and the following index of variation coefficient CVrr that normalizes the standard deviation SD with the average value of the heartbeat interval are also used.

CVrr = SD of heartbeat interval in arbitrary time zone / average of heartbeat interval in arbitrary time zone

The vehicle state determination unit 27 receives a signal from the vehicle sensor 13 and determines whether the vehicle is stopped, traveling at a constant speed, accelerating or decelerating, a curve or a turning angle, etc. Or the like (that is, whether the steering wheel 34 is being used) or the like is determined.

  The determination result in the vehicle state determination unit 27 is transmitted to the signal processing calculation unit 29, and is reflected in the state estimation based on the driver's electrocardiogram and pulse wave, which will be described later. For example, while the vehicle is stopped, the driver is likely to be in a resting state, and noise such as myoelectric potential is reduced. However, noise is also increased during traveling and steering operation, so that consideration is necessary.

  The signal processing calculation unit 29 corrects the heartbeat interval based on the electrocardiogram waveform acquired by the electrocardiogram waveform acquisition unit 23, the pulse wave waveform acquired by the pulse wave waveform acquisition unit 25, and the like, as will be described in detail later. At the same time, an index indicating the fluctuation amount of the heartbeat interval such as the heartbeat interval, the heart rate, and HF is calculated. The result calculated by the signal processing calculation unit 29 is output to the driver state estimation unit 31.

  The driver state estimation unit 31 estimates a driver state from an index indicating the amount of heartbeat interval fluctuation such as the heartbeat interval, heart rate, and HF after interpolation processing calculated by the signal processing calculation unit 29. For example, it is estimated whether the driver is in physical condition or sleepy, or whether the driver is suitable for driving. As this estimation method, a known method such as the use of the standard deviation of the heartbeat interval described in Japanese Patent Application Laid-Open No. 2005-31653 can be employed. The driver state estimation result determined by the driver state determination unit 31 is transmitted to the vehicle control unit 33.

  Based on the estimation result of the driver state estimation unit 31, the vehicle control unit 33 determines what action is to be taken to the driver, passenger, vehicle, and the like. A control signal corresponding to the determination is output to the storage device 17, the display device 19, and the communication device 21.

  In addition, for example, when it is determined that the state of the driver is dangerous for driving, the vehicle control unit 33 automatically applies a stepwise brake to support the driver's vehicle operation, and the vehicle is safely stopped. In order to call attention to surrounding vehicles, a hazard lamp may be blinked.

c) Next, an outline of characteristic processing in the present embodiment will be described.
<Heartbeat interval interpolation processing>
The R wave detection of the electrocardiographic waveform shown in FIG. 3 includes a method for obtaining a maximum peak from an original waveform or a differential waveform, and a method for obtaining from a template as disclosed in JP-A-2007-301101.

However, the problem here is the detection accuracy of the electrocardiographic waveform.
In other words, the electrocardiographic waveform collected by the electrocardiographic sensor 1 is compared with the body movement of the driver when the driver is at rest, such as when the vehicle is stopped or traveling straight at a constant speed. Since the contact pressure between the driver's hand and the electrodes 35 and 37 on the surface of the steering wheel 39 tends to be constant, the electrocardiographic waveform tends to be relatively stable. However, the electrocardiographic waveform collected by the electrocardiographic sensor 1 is easily affected by the myoelectric potential due to the body movement of the driver, and when the vehicle is accelerating, decelerating or running on a curve, the body of the driver The movement is relatively large, and the contact pressure between the driver's hand and the electrodes 35 and 37 on the surface of the steering wheel 39 tends to change, so that the electrocardiographic waveform tends to be disturbed. In addition, when the driver operates the steering 39, the electrocardiographic sensor 1 cannot collect an electrocardiographic waveform during the period when one hand is separated from the steering 39.

  On the other hand, the pulse wave waveform collected by the pulse wave sensor 3 also tends to be disturbed by the body movement of the driver, like the electrocardiographic waveform. However, since an electrocardiogram waveform has a different measurement principle and measurement site, the waveform disturbance is not necessarily synchronized with the electrocardiogram waveform. In particular, as described above, the electrocardiogram waveform is collected by differential amplification between two points of the left hand and the right hand, but the pulse wave waveform is collected at one point. Waveform can be collected.

  FIG. 4 shows an electrocardiogram waveform, a pulse wave waveform, a differential waveform of the pulse wave, and a second-order differential waveform of the pulse wave when one hand floats momentarily during operation. As shown in FIG. 4, it can be seen that there is a time zone in which the pulse waveform can be normally collected even if the electrocardiogram is disturbed by noise.

  In addition, since the pulse wave is transmitted to the body almost simultaneously with the heart beat, the electrocardiogram waveform and the pulse wave waveform are formed with substantially the same period although there is a phase difference for conduction to the periphery. That is, the electrocardiogram waveform RRIa, the pulse wave waveform RIa, the pulse wave differential waveform PI2a, and the pulse wave second-order differential waveform PI3a are substantially equivalent.

  Therefore, in the present embodiment, in the configuration in which the pulse wave and the electrocardiogram are collected simultaneously, the missing part of the heartbeat interval is interpolated with the pulse wave. Specifically, when the RRIb of the electrocardiogram waveform abnormally changes compared to the previous time, interpolation is performed with at least one of the pulse wave waveform PIb, the pulse wave differential waveform PI2b, and the pulse wave second-order differential waveform PI3b. .

  For example, as shown in FIG. 5, by interpolating the heartbeat interval with the pulse interval, it is possible to calculate a substantially accurate heartbeat interval and an index indicating the amount of variation thereof. That is, even when the heartbeat interval becomes abnormally large in, for example, 6 to 8 seconds in the figure, a substantially accurate heartbeat interval can be obtained by adopting the corresponding pulse wave interval as the heartbeat interval.

  Specifically, since the heartbeat interval and the pulse interval correspond to each other almost one-to-one, when interpolating the heartbeat interval using the pulse interval, use data of a period in which an accurate heartbeat interval is obtained. The timing at which an accurate heart rate interval is expected to be obtained is determined by, for example, comparing the electrocardiographic R wave position and the position of the pulse wave feature amount, and the pulse interval corresponding to the timing is determined by It is adopted as a heartbeat interval.

As a result, the accuracy of the heartbeat interval is improved as compared with the case where the correction is made with an intermediate value simply as in the prior art (see JP-A-6-22914).
In the present embodiment, the missing part of the heartbeat interval is interpolated by the pulse interval. For example, the pulse wave sensor 3 does not contact the body, and a time zone in which the pulse wave waveform cannot be detected also occurs. Therefore, when the contact between the pulse wave sensor 3 and the body is determined by a pressure sensor or the like and it is determined that the contact is not made, the interpolation process is not performed.
<Processing of reliability using interpolated heartbeat interval>
The driver state estimation unit 31 estimates a driver state from an index indicating the amount of heartbeat interval fluctuation such as the heartbeat interval, heart rate, and HF after interpolation processing calculated by the signal processing calculation unit 29.

  For example, it is estimated whether the driver is in physical condition (for example, the state of occurrence of arrhythmia or blood pressure) or sleepy, or whether the driver is suitable for driving. As a method for estimating the driver state from the index indicating the fluctuation amount of the heart rate and the heart beat interval, a well-known technique described in, for example, Japanese Patent Application Laid-Open No. 2005-31653 can be employed.

In this case, it is possible to use an index obtained by interpolating the missing part of the heartbeat interval with the pulse interval, but it is also possible to further improve the accuracy.
In other words, although the heartbeat interval and the pulse interval are almost equivalent, they do not correspond completely at 1: 1, and the relationship changes depending on the blood pressure and the blood vessel state from the heart to the blood vessel. If used, there is a possibility that an erroneous determination occurs in the driver state estimation result.

  Therefore, in the present embodiment, together with the interpolation method described above, the reliability of the index indicating the heart rate and the fluctuation amount of the heartbeat interval is calculated and displayed from the interpolation condition of the heartbeat interval, and further, according to the reliability, This is reflected in the conditions for determining the driver status.

Here, the reliability will be described.
The reliability indicates the degree of reliability (level) of data indicating the state of the driver, for example, the heart rate and the index indicating the fluctuation amount of the heart rate interval, and the interpolation number of the pulse interval and the time to be analyzed. The greater the percentage in the band, the lower the reliability.

  For example, when 6 data, which is 10% of the whole heartbeat interval 60 data, are interpolated by the pulse interval, the reliability is 90%. Further, since the error becomes larger when the heartbeat interval is lost successively than when the heartbeat interval is lost one point at a time, the greater the number of consecutive interpolations, the lower the reliability. For example, if the reliability is 90% when 10% of data is missing one by one, the reliability decrease is doubled and the reliability is 80% when they are continuously missing.

  By displaying the reliability obtained in this way to the driver together with an index indicating the amount of fluctuation of the heart rate after the interpolation process and the heart rate interval, it may lead to misunderstanding that trusts all the displayed numerical values. Can be prevented. If the reliability further decreases, the sensor contact of the electrocardiogram or the pulse wave is considered to be poor, so a warning or caution is notified to the driver.

The reliability obtained in this way is reflected in the estimation of the driver's state together with an index indicating the amount of heartbeat interval variation such as the heartbeat interval, heart rate, and HF after interpolation processing.
For example, when determining a state in which the driver is not suitable for driving using HF, the threshold can be set assuming that the reliability is high when the reliability is 100%, but the reliability is 100% when the reliability is 50%. If the same threshold value is set, there is a possibility that an erroneous determination is made that the driver is in an abnormal state although the driver is in a normal state. Therefore, for example, when the reliability is low, an erroneous determination is prevented by increasing the determination threshold value for the unsuitable driving state.

  FIG. 6 shows an example of state estimation threshold setting. For example, if the threshold value when the reliability is 100% is set to T, the threshold value when the reliability is S% is set to T / S.

Furthermore, not only the threshold value but also the state may be determined from data continuity as described below.
For example, as shown in FIG. 7, when the HF exceeds the predetermined threshold value for five consecutive data, it may be determined as dangerous. However, when all the five data are not 100% reliable, the reliability of the state determination result is lacking. Therefore, it is assumed that weighting is performed based on the reliability for each piece of data without simply determining the number of continuous data. For example, 1 is set when the reliability is 100%, 0.5 is set when the reliability is 50%, and the determination condition is set to 5 including weighting instead of the number of data 5. As a result, when the reliability is 100%, it is determined that the risk is continuous for 5 data, and when the reliability is 50%, since 1 data is 0.5, it is determined that it is dangerous when the threshold is exceeded for 10 continuous data.

The driver state estimation result thus obtained is displayed to the driver.
Further, not only the state estimation result but also the reliability at the time of determination may be displayed at the same time.
Furthermore, it may be desirable to display only when necessary instead of constantly displaying depending on the contents of state estimation, obstacles to driving, and individual preferences. Therefore, the reliability is more than a predetermined value, for example, the reliability is only 80% or more. The state estimation result and the reliability may be displayed. Note that a decrease in reliability may be warned.

d) Next, processing performed by the electronic control unit 15 will be described with reference to the flowcharts of FIGS.
<Main routine>
This processing is performed from acquisition of an electrocardiogram waveform and a pulse wave waveform to interpolation processing.

In step (S) 100 of FIG. 8, the electrocardiographic R wave is detected from the electrocardiographic waveform obtained by the electrocardiographic sensor 1.
In the subsequent step 110, a heartbeat interval (RRI: RRIa in FIG. 4 or the like) is calculated from the peak interval of the electrocardiographic R wave.

  In the following step 120, a pulse wave feature point is detected from the pulse wave waveform obtained by the pulse wave sensor 3. For example, the peak (for example, a known traveling wave peak P1) is obtained from the pulse waveform shown in FIG. In addition, when using the differential waveform of the pulse wave of FIG. 4, the feature amount (for example, a1 of the velocity pulse wave) can be used. Similarly, when using the second-order differential waveform of the pulse wave, the feature is used. A quantity (for example, a of acceleration pulse wave) can be used.

In the following step 130, for example, the peak interval (such as PIa in FIG. 4) of the pulse wave feature point is calculated.
In the subsequent step 140, a determination process is performed as to whether or not an interpolation process to be described later is performed (that is, whether or not an interpolation process is necessary and possible). If it is determined that the interpolation process is to be performed, for example, a flag indicating that is set.

  In the following step 150, it is determined whether or not the interpolation process is executed depending on whether or not the flag is set. If an affirmative determination is made here, the process proceeds to step 160. If a negative determination is made, the present process is temporarily terminated.

In step 160, the above-described interpolation process is executed. That is, using the pulse interval obtained by the pulse wave sensor 3, a process for interpolating the heart beat interval obtained by the electrocardiographic sensor 1 is performed, and this process is temporarily terminated.
<Interpolation processing availability determination>
This processing is processing for determining whether or not the interpolation processing in step 140 is possible.

  In step 200 of FIG. 9, it is determined whether or not the electrocardiographic sensor 1 is in contact with the driver's hand (detection unit) (that is, whether or not an accurate signal is obtained from the electrocardiographic sensor 1). The determination is made based on a signal from the contact sensor (contact impedance measuring sensor) 9. If an affirmative determination is made here, the process proceeds to step 210.

  That is, for example, in the case of the right hand, when a contact impedance measurement sensor detects an impedance similar to that obtained when a human hand touches the confirmation electrode 45 and the electrode 35 of the electrocardiogram sensor 1. Is determined that the hand of the driver is in contact with the electrode 35 of the electrocardiographic sensor 1.

  In step 210, it is determined whether or not the heartbeat interval calculated from the electrocardiogram waveform is within a predetermined range (within a range in which the heartbeat interval can be determined to be normal). If an affirmative determination is made here, the process proceeds to step 220, while if a negative determination is made, the process proceeds to step 230.

  In step 230, since the heartbeat interval is normal, the heartbeat interval is not corrected, and the heartbeat interval is stored in, for example, the storage device 17, displayed on the display device 19, or communicated to the outside by the communication device 21. This process ends.

  On the other hand, when a negative determination is made in step 200 (that is, when the contact state with the electrocardiographic sensor 1 is determined to be inappropriate), or when a negative determination is made in step 210 (that is, the heartbeat interval data is If it is determined that there is an abnormality), in step 230, it is determined whether or not the pulse wave sensor 3 is in contact with the driver's hand (detection unit). That is, whether or not an accurate signal can be obtained from the pulse wave sensor 3 is determined based on the signal from the pulse wave sensor contact sensor (pressure sensor) 11. If determined, the process proceeds to step 260.

  That is, for example, when a pressure sensor detects a pressure similar to the pressure obtained when a human hand touches the pressure sensing unit 47, the driver's hand is placed on the measurement unit 43 of the pulse wave sensor 3. It is judged that they are in contact.

  In step 240, it is determined whether or not the pulse wave interval calculated from the pulse wave waveform is within a predetermined range (within a range in which the pulse wave interval can be determined to be normal). If an affirmative determination is made here, the process proceeds to step 250, while if a negative determination is made, the process proceeds to step 260.

  In step 250, since the pulse interval is normal, the heartbeat interval is interpolated using this pulse interval, and the heartbeat interval is stored in, for example, the storage device 17, displayed on the display device 19, or the communication device 21. Communicate to the outside and once complete this process.

On the other hand, when a negative determination is made in step 230 (that is, when the contact state with the pulse wave sensor 3 is determined to be inappropriate), or when a negative determination is made in step 240 (that is, the pulse interval data is If it is determined that there is an abnormality), in step 260, both the heartbeat interval and the pulse wave interval are regarded as errors, and the interpolation processing is not performed, and this processing is temporarily ended.
<Determination of driver status>
This processing is processing for obtaining an index of the heart rate and the fluctuation amount of the heart beat interval using the heart beat interval obtained by the interpolation processing, and estimating the state of the driver based on them.

In step 300 of FIG. 10, the heart rate (reciprocal of heart rate interval × 60) is calculated using the interpolated heart rate interval.
In subsequent step 310, frequency analysis of the heartbeat interval is performed to calculate indices such as LF, HF, and LF / HF.

  In the following step 320, using the above-mentioned index, as shown in, for example, Japanese Patent Application Laid-Open No. 2007-301101, the driver state (for example, arrhythmia or blood pressure state) is a state that requires some warning (ie, A process for determining whether or not the state is normal is performed. As a result of the determination process, if it is determined that the state of the driver is not normal, for example, a flag indicating that is set.

  When this determination is made, as described above, the state of the driver is determined in consideration of data reliability and the like. For example, if the number of interpolations, the number of consecutive interpolations, and the ratio of interpolation are large, the reliability of the data is low, so the threshold for judging the driver state as abnormal is raised, or conversely, the weighting of the data is adjusted Do not make a wrong decision. Furthermore, since the reliability of the data changes depending on the traveling state of the vehicle, for example, when the vehicle is traveling on a curve or traveling at a high speed, the reliability of the data may be set low.

  In the next step 330, it is determined whether or not to execute processing such as warning depending on whether or not the flag is set. If an affirmative determination is made here, the process proceeds to step 340, while if a negative determination is made, the process proceeds to step 350.

  In step 340, since it is determined that the driver is not in a normal state, an alarm or the like is notified according to the content of the driver, for example, displayed on the display device 19 or by voice or the like, and the present process is temporarily terminated. To do.

On the other hand, in step 350, since the driver is in a normal state, for example, a message to that effect is displayed, or data such as heart rate is displayed on the display device 19, and this process is temporarily terminated.
e) As described above, in this embodiment, the ECG interval and the pulse wave interval are calculated using the signals from the ECG sensor 1 and the pulse wave sensor 3, and the ECG interval data is not normal. Since the ECG interval is interpolated using the pulse wave interval, a remarkable effect is obtained in that accurate data is always obtained.

In addition, an index for determining the state of the driver such as heart rate, LH, HF, LF / HF or the like is calculated from the interpolated heart rate interval, and when determining the driver state using this index, the reliability of the data is calculated. Therefore, there is an advantage that the possibility of erroneous determination of the driver state is low.
[Second Embodiment]
Next, the second embodiment will be described, but the description of the same content as the first embodiment will be omitted.

As shown in FIG. 11, there is a temporal shift between the electrocardiogram waveform and the pulse waveform (here, for example, a differential waveform of the pulse waveform).
In the present embodiment, for example, the pulse wave feature point position P _t-1 (of differential waveform) corresponding to the previous electrocardiogram R wave position R _t-1 can be detected, and the current ECG R wave corresponding to the missing electrocardiogram R wave is detected. If the pulse wave feature point position P _t can be detected, the current pulse wave feature point position P _t , the previous pulse wave feature point position P _t-1, and the previous electrocardiographic R wave position R _t-1 The current electrocardiographic R wave position P _t can be estimated and interpolated from the time difference D _t−1 .

Specifically, the estimated current electrocardiographic R wave position P _t is determined from the current pulse wave characteristic point position P _t , the previous pulse wave characteristic point position P _t−1, and the previous electrocardiographic R wave position R _t−1. It can be obtained by subtracting the time difference D _t-1 from.

This embodiment also has the same effect as the first embodiment.
As mentioned above, although this embodiment explained in full detail about the example for the driver in vehicles, the present invention is not restricted to the embodiment mentioned above, and in the range which does not deviate from the present invention, various modification and substitution are carried out. Can be added.

(1) The reason why the driver in the vehicle is used here is that there are many situations in which stable electrocardiogram measurement is difficult in the vehicle, and the present invention is particularly useful.
In addition, since vehicle conditions and vehicle operation conditions greatly affect the electrocardiogram and pulse wave acquisition performance, vehicle information such as vehicle speed and steering angle is reflected in the reliability calculation when the present invention is implemented in the vehicle. It is preferable to do. Further, the state of the driver may be estimated by combining the vehicle information.

For example, the reliability is lowered when the steering operation amount is large. In addition, as the vehicle speed is higher, the above-described estimation determination threshold value may be lowered to facilitate the determination of danger.
(2) Regardless of the vehicle, the electrocardiogram waveform and pulse wave waveform acquired simultaneously by the existing electrocardiogram device and pulse wave device are read into a personal computer, and the state of the measurement object is determined by the personal computer. Also good.

(3) Furthermore, the function of the above-described biological state estimation apparatus can be realized by processing executed by a computer program, and this program can be recorded on a recording medium.
That is, the function for realizing the above-described program in the computer system can be provided as a program that is activated on the computer system side, for example. In the case of such a program, for example, the program is recorded on a computer-readable recording medium such as a flexible disk, a magneto-optical disk, a CD-ROM, a DVD, and a hard disk, and is used by being loaded into a computer system and started as necessary. be able to. In addition, the program may be recorded as a computer-readable recording medium such as a ROM or a backup RAM, and the ROM or the backup RAM may be incorporated into a computer system.

It is a block diagram which shows the function of the biological condition estimation apparatus of 1st Embodiment. It is explanatory drawing which shows arrangement | positioning of each sensor in 1st Embodiment. It is a graph which shows an electrocardiogram signal. It is a graph which shows the correspondence of an electrocardiogram waveform, a pulse wave waveform, a differential waveform of a pulse wave, and a second-order differential waveform of a pulse wave. It is explanatory drawing which shows the method of interpolating a heartbeat interval using a pulse interval. It is a graph which shows the method of changing a threshold value according to reliability. It is a graph explaining the method of danger determination using continuous data. It is a flowchart which shows the main routine in 1st Embodiment. It is a flowchart which shows the process of the interpolation method of a heartbeat interval. It is a flowchart which shows the process which determines the state of a driver. In 2nd Embodiment, it is a graph which shows the relationship between the electrocardiogram waveform, the pulse wave waveform, the differential waveform of the pulse wave, and the second-order differential waveform of the pulse wave.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrocardiogram sensor 3 ... Pulse wave sensor 13 ... Vehicle sensor 19 ... Display apparatus 29 ... Signal processing calculating part 31 ... Driver state determination part 33 ... Vehicle control part

Claims (25)

A biological state estimation device that estimates the state of a living body based on the electrocardiographic waveform of the living body obtained by the electrocardiographic waveform acquisition means and the pulse wave waveform of the living body obtained by the pulse wave waveform acquisition means,
Measurement state determination means for determining whether or not the electrocardiogram waveform is in a state inappropriate for detecting a heartbeat;
When the measurement state determination means determines that the electrocardiogram waveform is not suitable for detecting a heartbeat, an interpolation means for interpolating the electrocardiogram waveform using the pulse wave waveform;
A biological state estimation device comprising:   The measurement state determination unit detects a heartbeat based on a signal from a contact state detection unit that detects a contact state between the electrocardiogram waveform acquisition unit and the living body or a contact state between the pulse wave waveform acquisition unit and the living body. The biological state estimation apparatus according to claim 1, wherein it is determined whether or not the state is suitable for the living body.   The biological state estimation according to claim 1 or 2, wherein the measurement state determination unit determines whether or not the state is suitable for heartbeat detection based on whether or not the heartbeat interval is outside a predetermined allowable range. apparatus.   The living body state estimation apparatus according to claim 1, wherein the interpolation unit interpolates a heartbeat interval with a pulse interval.   The interpolation means obtains a pulse interval using any one of the characteristic points of a pulse wave waveform, a first-order differential waveform of the pulse wave, and a second-order differential waveform of the waveform, and interpolates the heart beat interval using the pulse interval. The biological state estimation apparatus according to claim 4, wherein:   The living body state estimation apparatus according to claim 4 or 5, wherein the interpolation means interpolates as it is using the latest pulse interval corresponding to the heartbeat interval.   The interpolation means includes a time difference between any one of the characteristic points of the previous electrocardiogram R wave and the previous pulse waveform, the first-order differential waveform of the pulse wave, and the second-order differential waveform of the waveform, the current pulse waveform, The current ECG R-wave position is estimated from the position of one of the characteristic points of the first-order differential waveform of the pulse wave and the second-order differential waveform of the waveform, and the estimated current ECG R-wave position and the previous The biological state estimation apparatus according to claim 4 or 5, wherein a time interval with an electrocardiogram R wave is interpolated as a heartbeat interval.   The biological state estimation apparatus according to claim 1, wherein at least one of indices indicating a heart rate and a fluctuation amount of the heart beat interval is calculated from the interpolated heart beat interval.   When calculating at least one of the indexes indicating the fluctuation amount of the heart rate and the heart rate interval, the reliability of data is determined according to at least one of the number of interpolations, the number of consecutive interpolations, and the rate of interpolation. The biological state estimation device according to claim 8, wherein the reliability shown is calculated.   The biological state estimation apparatus according to claim 8 or 9, wherein the reliability decreases as the number of interpolations, the number of consecutive interpolations, and the ratio of interpolation decrease.   The biological state estimation apparatus according to any one of claims 8 to 10, wherein at least one of the heart rate, an index indicating a fluctuation amount of a heartbeat interval, and a reliability is displayed.   The biological state according to any one of claims 8 to 11, wherein the state of the user is determined from at least two of the interpolated heart rate, an index indicating the amount of heartbeat interval variation, and the reliability. Estimating device.   The biological state estimation apparatus according to claim 12, wherein when the user state is determined, a determination threshold value is switched according to the reliability.   The living body state estimation apparatus according to claim 12, wherein when determining the state of the user, weighting of data used for determination is changed according to the reliability.   The living body state estimation apparatus according to any one of claims 12 to 14, wherein when the user state is determined, at least a determination result is displayed among the determination result and the reliability.   The living body state estimation apparatus according to any one of claims 9 to 15, wherein the display content is displayed only when the reliability is equal to or higher than a predetermined level.   The living body state estimation apparatus according to any one of claims 9 to 16, wherein when the reliability decreases, a warning about the reliability decrease is given.   18. The living body according to claim 2, wherein whether or not the pulse wave waveform acquisition unit is in a good wearing state is determined from the wearing state determination unit, and the interpolation process is executed only when the wearing state is good. State estimation device.   The biological state estimating device according to claim 1, wherein the biological state is estimated for a driver in a vehicle.   The biological state estimation apparatus according to claim 19, wherein the reliability is calculated by combining vehicle information.   21. The state of the driver is determined from at least two of the interpolated heart rate, an index indicating a fluctuation amount of a heartbeat interval, and reliability, and vehicle information. Biological state estimation device.   The biological state estimating device according to claim 21, wherein the state of the driver is controlled based on a determination result.   The biological state estimation device according to any one of claims 19 to 22, wherein at least one of the biological state estimation result and the warning content is displayed using the vehicle navigation device.   A program for causing a computer to function as the measurement state determination unit and the interpolation unit according to any one of claims 1 to 23.   A computer-readable recording medium on which the program according to claim 24 is recorded.

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