JP2010012100A - Sleepiness detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sleepiness detector which can highly accurately detect a light sleepiness of a driver. <P>SOLUTION: The sleepiness detector initially acquires the measured data of a measuring device, carries out a pre-process to the measured data to obtain a heart beat value and extracts a heart beat fluctuation from the heart beat value. Then, after setting a reference section width of a heat beat feature amount to be referred to obtain a standard deviation of the heart beat feature amount (heart beat value and heart beat fluctuation), the sleepiness detector calculates the standard deviation of the heart beat feature amount in the reference section width and divides the standard deviation of the heart beat feature amount by the heart beat feature amount to obtain a standard deviation corrected value of the heart beat feature amount. Then, the sleepiness detector decides whether or not the driver has a light sleepiness by using the standard deviation corrected value of the heart beat feature amount. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a drowsiness detection device that detects drowsiness of a driver of a vehicle, for example.

As a conventional drowsiness detection device, for example, one described in Patent Document 1 is known. The drowsiness detection device described in Patent Document 1 measures an index (such as a heartbeat) indicating a physical condition for determining the drowsiness of the driver, and extracts a feature amount that changes according to the drowsiness of the driver from the index, By comparing this feature amount with a threshold value, it is determined whether or not the driver is in a dozing state. When extracting features from the heartbeat, Fourier transform is performed on the time-series data of the heartbeat cycle to generate an amplitude power spectrum, and integration processing is applied to the amplitude power spectrum to obtain time-series data of heartbeat fluctuation. Is obtained by performing a differentiation process on the heart rate fluctuation time-series data, calculating a threshold value from the average value and standard deviation of the differential value of the heartbeat fluctuation, and the differential value of the heartbeat fluctuation exceeding the threshold value Extract as a quantity.
JP 2008-35964 A

  However, in the above-described conventional technology, for example, when the driver (subject) has very shallow drowsiness such as during driving, there is a possibility that the driver cannot be accurately determined to be drowsy. is there.

  The objective of this invention is providing the drowsiness detection apparatus which can detect a subject's shallow drowsiness with high precision.

  As a result of intensive studies on the driver's sleepiness, the present inventors have determined attention to heart rate features such as heart rate and heart rate fluctuation that are affected by autonomic nervous activity associated with the occurrence of sleepiness in order to determine shallow sleepiness. Found the fact that it is effective. After further investigation, statistics such as standard deviation representing the magnitude of fluctuations in heart rate feature values are based on two physical functions: body activation by the sympathetic nervous system and body rest by the parasympathetic nervous system. It was found that it is a feature that can express a state of dynamic antagonism and has a correlation with shallow sleepiness. The present invention has been made based on such knowledge.

  That is, the drowsiness detection device of the present invention includes a measurement unit that measures a heartbeat or a pulse of a subject, a heartbeat feature amount extraction unit that extracts a heartbeat feature amount from the heartbeat or pulse measured by the measurement unit, and a heartbeat feature amount extraction unit Fluctuation distribution calculating means for obtaining the fluctuation distribution of the heart rate feature value extracted by the method, and sleepiness degree judging means for determining the sleepiness level of the subject using the fluctuation distribution of the heart rate feature value obtained by the fluctuation distribution calculation means. It is characterized by.

  In such a drowsiness detection device of the present invention, a heartbeat or a pulse of a subject is measured, a heartbeat feature amount is extracted from the measurement data, a fluctuation distribution of the heartbeat feature amount is obtained, and the fluctuation distribution of the heartbeat feature amount is used. To determine the subject's sleepiness. Thus, by performing sleepiness determination using the fluctuation distribution of the heartbeat feature value correlated with shallow sleepiness, it is possible to detect the subject's shallow sleepiness with high accuracy.

  Preferably, the fluctuation distribution calculating means obtains a standard deviation of the heartbeat feature quantity as a fluctuation distribution of the heartbeat feature quantity, and the sleepiness degree judging means judges the sleepiness degree of the subject based on the standard deviation of the heartbeat feature quantity. In this case, for example, the drowsiness level of the subject can be easily and reliably determined by comparing the standard deviation of the heartbeat feature quantity with a preset drowsiness determination threshold value.

  Further, it further includes an average value calculating means for obtaining an average value of the heartbeat feature values extracted by the heartbeat feature value extracting means, and the fluctuation distribution calculating means obtains a standard deviation of the heartbeat feature values as a fluctuation distribution of the heartbeat feature values, and sleepiness The degree determination means may determine the sleepiness level of the subject based on the standard deviation of the heartbeat feature amount and the average value of the heartbeat feature amount. In this case, for example, the sleepiness level of the subject can be easily and reliably determined by generating a distribution representing sleepiness from a matrix (two-dimensional coordinates) of the average value and standard deviation of the heartbeat feature values.

  Here, it is preferable that the apparatus further comprises reference time width setting means for setting a reference time width of a heartbeat feature value to be referred to in order to obtain a standard deviation of the heartbeat feature value, and the fluctuation distribution calculating means includes The standard deviation of the heart rate feature amount is calculated. In this case, the reference time width of the heart rate feature value is set to an optimum value for each subject, and the standard deviation of the heart rate feature value is obtained within the reference time range, thereby realizing sleepiness detection independent of the subject. be able to.

  At this time, it is preferable that the reference time width setting means frequency-analyze the heartbeat feature value to extract a peak value frequency, and set a cycle corresponding to the peak value frequency as the reference time width. In this case, the optimal reference time width can be reliably set for each subject by extracting the peak value frequency in the frequency range of the heart rate feature value that is estimated to cause sleepiness to be noticeable for each subject.

  Preferably, the fluctuation distribution calculation means includes means for correcting the standard deviation of the heartbeat feature quantity by dividing the standard deviation of the heartbeat feature quantity by the heartbeat feature quantity. Since the heart rate feature quantity such as the heart rate differs for each subject, the standard deviation of the heart rate feature quantity also differs for each subject. For this reason, the drowsiness detection result may differ depending on the subject. Therefore, by correcting the standard deviation of the heart rate feature amount by the heart rate feature amount, the determination error of sleepiness due to the difference in the heart rate feature amount for each subject is eliminated, and detection of sleepiness not depending on the subject is sufficiently accurate. It can be carried out.

  Further, preferably, the heartbeat feature amount is a heart rate, a heartbeat fluctuation low frequency component related to sympathetic activity, a heartbeat fluctuation high frequency component related to parasympathetic activity, a heartbeat fluctuation low frequency component and a heartbeat fluctuation high frequency component. Including at least one of the ratios. For example, the characteristics of the heart rate feature amount vary depending on the subject, such as a person whose sleepiness is remarkably displayed in the heart rate, a person whose movement of the sympathetic nerve is active, and a person whose movement of the parasympathetic nerve is active. Therefore, by determining the sleepiness level using the heartbeat feature amount suitable for the subject, the shallow sleepiness of the subject can be detected with higher accuracy.

  According to the present invention, shallow sleepiness of a subject can be detected with high accuracy. As a result, for example, when the driver who is the subject has a slight drowsiness during driving, normal consciousness recovery or rest can be promoted at that time.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a drowsiness detection device according to the present invention will be described in detail with reference to the drawings.

  First, the concept of sleepiness detection according to the present invention will be described. For example, as shown in FIG. 1, a person's sleepiness level includes a region (region A) representing a strong sleepiness state including a dozing state, a very sleepy state (D4), and a very sleepy state (D3), and a sleep state. It can be divided into a state (region B) representing a shallow sleepiness state including a state (D2) that is likely to be sleepy (D1) that is likely to be sleepy (D0). The drowsiness level shown in FIG. 1 is evaluated from NEDO's facial expression (refer to Human Life Engineering Research Sensor: “Human Sensory Measurement Manual”, Volume 1, Section 2, p.146 (1999)). ).

  In recent years, there are several conventional techniques for determining a strong sleepiness state (area A) based on the driver's face direction or blinking eyes, but there is no conventional technique for determining an area (area B) representing a shallow sleepiness condition. First, we examined the applicability of the existing blink feature value for the determination of shallow sleepiness.

  From existing research, it is known that the effective blink feature amount in the strong sleepiness state (region A) is the closed eye time (time required for one blink) and the number of blinks within a certain time. Therefore, the correspondence between these two blink feature quantities and changes in sleepiness level in the shallow sleepiness state (region B) was investigated. Specifically, the vehicle traveled at a speed of 80 km / h for 1 hour on a predetermined circuit course, and blink data and drowsiness level data determined from facial expressions were collected at that time. An example of the collected data is shown in FIG. The correlation coefficient between the drowsiness level and the blink feature amount is the closed eye time: 0.2, and the number of blinks: 0.1. It has been found that it is difficult to determine shallow sleepiness only by the blink feature amount.

  Therefore, we thought that the effect of sleepiness might appear as a change in the state of the body before it appears in the body, and focused on the features inside the body.

  Human characteristics inside the body that change with sleepiness include brain information processing nerve activity that performs cognitive judgment and autonomic nerve activity that governs human activity. The neural activity of information processing decreases with sleepiness, but this decrease in brain activity occurs with changes in autonomic nervous activity. Therefore, we focused on autonomic nerve activity.

  The autonomic nerve is composed of two nervous systems, a sympathetic nervous system that activates the body and a parasympathetic nervous system that stabilizes the body. In the dozing state, the parasympathetic nervous system is actively active in an attempt to guide the body to rest, and in the absence of sleepiness, the sympathetic nervous system is active. Therefore, it was hypothesized that the balance of these two nervous systems changes according to the sleepiness levels D1 to D4 shown in FIG.

  Since the autonomic nerve is at the center of the body, it is impossible to measure the activity itself. Therefore, we focused on measurable heartbeats whose relation to autonomic nerve activity is medically clear. The heartbeat is affected by the sympathetic nervous system and the parasympathetic nervous system, and changes occur in the pulsation of the heartbeat (heart rate and heart rate fluctuation).

  FIG. 3 shows the correspondence between the heartbeat feature quantity and the autonomic nerve activity. The heart rate characteristic amount includes a heart rate fluctuation low frequency component (HRV-L) related to sympathetic nerve activity, a heart rate fluctuation high frequency component (HRV-H) related to parasympathetic nerve activity, and HRV- There is a ratio between L and HRV-H (hereinafter, L / H) and a heart rate. These four heartbeat features were considered as features inside the body associated with sleepiness.

  The vehicle runs steady for 1 hour at a speed of 80 km / h on a predetermined circuit course. At that time, heart rate data and drowsiness level data determined from facial expressions are collected. Using these data, the above four heart rate features are shallow. The relationship with sleepiness was verified. An example of the collected data is shown in FIG.

  As a result of correlation coefficient test as a verification of relevance (see Bioscience Statistics: Nankodo (2005)), it was found that all four heart rate features correlated with shallow drowsiness although it was weak. . At this time, the correlation coefficient with the sleepiness level is as follows: HRV-L: 0.5, HRV-H: 0.3, L / H: 0.3, heart rate: 0.4, significant difference p <0.05. Met. Therefore, it was found that shallow sleepiness (region B) shows a higher relevance of the heartbeat feature amount inside the body than the feature amount outside the body like blinking.

HRV-L, HRV-H, L / H, and heart rate, which have been shown to be related to shallow sleepiness in this way, are considered to vary greatly because the correlation coefficient is not so high. In simple discriminant analysis, Judged that it was difficult to determine shallow sleepiness. Therefore, the Mahalanobis-Taguchi method (hereinafter referred to as the MT method) is used as a discrimination method taking into account data variations. The drowsiness determination accuracy evaluation formula adopted at this time is as follows. The following formula is an example of the drowsiness level D2.

  The evaluation accuracy was 10% as a result of evaluation using data obtained in a running test in which the vehicle traveled for 1 hour at a speed of 80 km / h on a predetermined circuit course. An example of the determination result is shown in FIG. In such a determination result, since there are many erroneous determinations, the aim was to improve the determination accuracy, and an extension of the feature amount was considered.

  The four heart rate feature values described above are average values of a certain time interval width, and are therefore feature values that represent a static state, such as a state of drowsiness during driving. Therefore, it seems that the state where two physical functions of the body activation and the rest that instinctively desires rest is dynamically antagonized cannot be expressed. Therefore, the standard deviation indicating the magnitude of the variation of the four heartbeat feature values was considered as a feature value representing such a dynamic state.

  As a result of confirming the relationship between the feature quantity representing the dynamic state and the sleepiness level by the same method as the feature quantity representing the static state, the correlation between the four feature quantities representing the dynamic state and shallow sleepiness I found out that At this time, the correlation coefficient with the drowsiness level is as follows: HRV-L standard deviation: 0.4, HRV-H standard deviation: 0.4, L / H standard deviation: 0.3, heart rate standard deviation : 0.4, significant difference p <0.05.

  The above-described MT method evaluates the S / N ratio of the determination result (a measure of the degree of influence of the determination result on noise such as variation) with respect to the extracted combination of feature amounts, and combines the appropriate feature amounts. There is a guideline to choose. Therefore, in accordance with this, the S / N ratios of the four feature amounts representing the static state, the four feature amounts representing the dynamic state, and the eight feature amounts obtained by combining them are evaluated. As a result, four feature amounts representing a static state: -96 dB, four feature amounts representing a dynamic state: -95 dB, and eight feature amounts: -89 dB, and the determination accuracy is improved by using eight feature amounts. I knew that I could expect.

  Thus, when the shallow drowsiness determination by the MT method was evaluated using eight feature amounts, a determination accuracy of 70% was obtained as shown in FIG. That is, the accuracy was improved by 60% compared to the above-described four feature amounts representing the static state.

  Based on the above concept, an embodiment of a drowsiness detection device according to the present invention will be described below.

  FIG. 7 is a block diagram showing a schematic configuration of one embodiment of the drowsiness detection device according to the present invention. In the figure, a drowsiness detection device 1 of the present embodiment is a device that is mounted on a vehicle and detects drowsiness of a driver of the vehicle. The drowsiness detection device 1 includes a measuring instrument 2, a drowsiness detection ECU (Electronic Control Unit) 3, and an alarm device 4.

  The measuring device 2 is a device that measures a driver's physiological index. Specifically, examples of the measuring instrument 2 include an electrocardiograph that measures a heart rate, and a pulse wave meter that measures a pulse from a fingertip, a forearm, or the like.

  The drowsiness detection ECU 3 includes a CPU, a memory such as a ROM and a RAM, an input / output circuit, and the like. The drowsiness detection ECU 3 inputs measurement data of the measuring instrument 2, performs a predetermined process, and determines whether or not the driver is in a weak drowsiness state.

  The alarm device 4 is a device that gives an alarm by sound (buzzer sound), image (screen display), vibration (vibrator), etc., and informs the driver of sleepiness.

  FIG. 8 is a flowchart showing details of the sleepiness detection processing procedure executed by the sleepiness detection ECU 3. Here, the case where the driver's heart rate is measured by an electrocardiograph as the measuring instrument 2 will be described as an example.

  In the figure, first, measurement data (heartbeat data) of the measuring instrument 2 is acquired (procedure S11), and preprocessing of the measurement data is performed (procedure S12). Specifically, in order to remove noise from the heartbeat data, first, a bandpass filter (BPF) process is performed on the heartbeat data to extract a component of a predetermined pass band (for example, 0.1 Hz to 30 Hz).

  Next, as shown in FIG. 9, the BPF processing is binarized by comparing the waveform of the heart rate data with a preset threshold value. At this time, binarization is performed so that each R wave portion of the waveform of the heartbeat data becomes “1” at the timing when it reaches the maximum value (see the enlarged view in FIG. 9).

  Subsequently, as shown in FIG. 10A, a section width (time interval) t at each timing at which the binary data becomes “1” is obtained, and a graph with each section width t as a vertical axis is generated. At this time, the section width t corresponds to the heartbeat cycle of the driver.

  Subsequently, as shown in FIG. 10 (B), a heartbeat cycle curve (see broken line) is obtained by interpolating the graph of the heartbeat cycle to obtain time-series data of the heartbeat cycle. And as shown in FIG. 11, the vertical axis | shaft unit of the time series data of a heartbeat period is converted into the heart rate per minute, for example. As a result, the heart rate value of the driver is obtained as one of the heart rate feature values.

Next, heart rate fluctuation is extracted as another heartbeat feature amount of the driver (step S13). Specifically, with respect to time-series data of the cardiac cycle (see FIG. 11), as shown in FIG. 12, fast Fourier transform (FFT) is applied to the analysis unit interval width T _term before the reference time T (arbitrary time stamp). ) To obtain a power (amplitude) spectrum for the frequency component.

Subsequently, as shown in FIG. 13, to the power spectrum obtained for each analysis unit interval width T _term by fast Fourier transform, to set the two frequency bands band (low frequency components and high frequency components). These frequency band bands are bands in which heartbeat fluctuations (changes) are likely to appear. Then, the amplitude spectrum is integrated for each frequency band.

  By repeating the above fast Fourier transform processing, frequency band setting processing and integration processing, time series data of amplitude spectrum power for each frequency band is obtained as shown in FIG. The time series data of the amplitude spectrum power is the time series data of heartbeat fluctuation. Thereby, the heartbeat fluctuation low frequency component value representing the movement of the sympathetic nerve and the heartbeat fluctuation high frequency component value representing the movement of the parasympathetic nerve are obtained. Further, by dividing the heartbeat fluctuation low frequency component value by the heartbeat fluctuation high frequency component value, a ratio (heartbeat fluctuation ratio value) between the heartbeat fluctuation low frequency component value and the heartbeat fluctuation high frequency component value is obtained.

  Next, the reference interval width (reference time width) of the heartbeat feature value referred to obtain the standard deviation of the heartbeat feature value is set (step S14). The reference interval width is set for the heart rate value, the heart rate fluctuation low frequency component value, the heart rate fluctuation high frequency component value, and the heart rate fluctuation ratio value. A specific method for setting the reference interval width will be described below by taking as an example a case where the reference interval width is applied to a heart rate value.

  That is, as shown in FIG. 15A, first, time-series data of heart rate values (see FIG. 11) is divided into arbitrary lengths (about several minutes) m and stored in a reference time width determination data storage buffer. To do.

Then, a frequency analysis result as shown in FIG. 15B is obtained by performing a fast Fourier transform (FFT) operation on the heart rate value stored in the data storage buffer. Here, F is the frequency range, f _max is the maximum value of the frequency range F, f _min is the minimum value of the frequency range F, and A is the maximum value of the amplitude spectrum power of the heart rate value in the frequency range F. F _peak is a frequency at which the maximum value A of the amplitude spectrum power is obtained. The frequency range F is a range obtained by statistical analysis as corresponding to sleepiness for each individual, and the frequency f _peak is a frequency at which changes in sleepiness are particularly likely to occur in the heart rate value.

Subsequently, the reference interval width of the heart rate value is obtained from the following calculation formula using such a frequency f _peak .
Reference interval width of heart rate value = 1 / f _peak

Thus, by extracting the peak value frequency f _peak in the frequency range F as a place where sleepiness appears prominently, it becomes possible to remove the influence of data noise and determine the sleepiness state (described later).

Next, the heart rate value, the heart rate fluctuation low frequency component value, the heart rate fluctuation high frequency component value, and the heart rate fluctuation ratio value are each cut out with the reference interval width (total number of data: N), and the average value in this interval is calculated (step S15). .
Cut out heart rate value = {X ₁ , X ₂ , X ₃ ,... X _N }
Cut out the heartbeat fluctuation low frequency component value _{= {Y 1, Y 2,} Y 3, ... Y N}
The extracted heartbeat fluctuation high-frequency component value = {Z ₁ , Z ₂ , Z ₃ ,... Z _N }
The extracted heartbeat fluctuation ratio value = {W ₁ , W ₂ , W ₃ ,... W _N }

  Next, in the same manner as described above, the heart rate value, the heart rate fluctuation low frequency component value, the heart rate fluctuation high frequency component value, and the heart rate fluctuation ratio value are each cut out with the reference interval width, and the standard deviation value in this interval is calculated (step S16).

Ｎ：切り出された心拍数値データの総数
ｉ：心拍数値の番号
Ｘｉ：ｉ番目の心拍数値
Ｘ_ave：心拍数値Ｎ個の平均値 The calculation formula for the standard deviation of the heart rate value is as follows.

N: Total number of cut out heart rate data
i: Number of heart rate value
Xi: i-th heart rate value
X _ave : Average value of N heart rate values

Ｎ：切り出された心拍ゆらぎ低周波成分値データの総数
ｉ：心拍ゆらぎ低周波成分値の番号
Ｙｉ：ｉ番目の心拍ゆらぎ低周波成分値
Ｙ_ave：心拍ゆらぎ低周波成分値Ｎ個の平均値 The calculation formula of the standard deviation of the heartbeat fluctuation low frequency component value is as follows.

N: Total number of extracted heartbeat fluctuation low frequency component value data
i: Number of heartbeat fluctuation low frequency component value
Yi: i-th heartbeat fluctuation low frequency component value
Y _ave : Average value of N heartbeat fluctuation low frequency component values

Ｎ：切り出された心拍ゆらぎ高周波成分値データの総数
ｉ：心拍ゆらぎ高周波成分値の番号
Ｚｉ：ｉ番目の心拍ゆらぎ高周波成分値
Ｚ_ave：心拍ゆらぎ高周波成分値Ｎ個の平均値 The calculation formula of the standard deviation of the heartbeat fluctuation high-frequency component value is as follows.

N: Total number of extracted heartbeat fluctuation high-frequency component value data
i: Number of heartbeat fluctuation high frequency component value
Zi: i-th heartbeat fluctuation high-frequency component value
_Zave : Average value of N heartbeat fluctuation high frequency component values

Ｎ：切り出された心拍ゆらぎ比値データの総数
ｉ：心拍ゆらぎ比値の番号
Ｗｉ：ｉ番目の心拍ゆらぎ比値
Ｗ_ave：心拍ゆらぎ比値Ｎ個の平均値 The calculation formula of the standard deviation of the heart rate fluctuation ratio value is as follows.

N: Total number of extracted heart rate fluctuation ratio value data
i: Heart rate fluctuation ratio number
Wi: i-th heart rate fluctuation ratio value
W _ave : Average value of N heart rate fluctuation ratio values

  Next, the standard deviation values of the heart rate value, the heart rate fluctuation low frequency component value, the heart rate fluctuation high frequency component value, and the heart rate fluctuation ratio value are corrected (step S17). These standard deviation values are corrected as follows.

  That is, first, the heart rate standard deviation value, the heart rate fluctuation low frequency component standard deviation value, the heart rate fluctuation high frequency component standard deviation value and the heart rate fluctuation ratio standard deviation value obtained in step S16, the heart rate value used for correction, and the heart rate fluctuation low frequency. The component value, the heartbeat fluctuation high frequency component value, and the heartbeat fluctuation ratio value are stored in the correction target standard deviation value storage buffer.

  Here, the heart rate value, the heart rate fluctuation low frequency component value, the heart rate fluctuation high frequency component value, and the heart rate fluctuation ratio value stored in the correction target standard deviation value storage buffer are acquired in a state where there is no sleepiness (for example, at the start of driving). Data is used. These data may be acquired before starting driving, for example, or may be acquired in advance and stored in the memory of the drowsiness detection ECU 3.

  An example of the heart rate standard deviation value and the heart rate value stored in the correction target standard deviation value storage buffer is shown in FIG.

Subsequently, using the following formula, the heart rate standard deviation value, the heart rate fluctuation low frequency component standard deviation value, the heart rate fluctuation high frequency component standard deviation value, and the heart rate fluctuation ratio standard deviation value are corrected to obtain a heart rate standard deviation correction value. Then, a heartbeat fluctuation low frequency component standard deviation correction value, a heartbeat fluctuation high frequency component standard deviation correction value, and a heartbeat fluctuation ratio standard deviation correction value are obtained.

  The heart rate standard deviation value shown in FIG. 16A and the heart rate standard deviation correction value calculated from the heart rate value are as shown in FIG.

  Because there are individual differences in heart rate values and heart rate standard deviation values, if the heart rate standard deviation value is used for drowsiness determination (described later) as it is, the determination result may vary depending on the subject. By correcting for each subject, the influence of the fluctuation of the heart rate value for each subject on the sleepiness determination result is eliminated. The same applies to the heartbeat fluctuation low frequency component value, the heartbeat fluctuation high frequency component value, and the heartbeat fluctuation ratio value.

  Next, use the heart rate standard deviation correction value, heart rate fluctuation low frequency component standard deviation correction value, heart rate fluctuation high frequency component standard deviation correction value, and heart rate fluctuation ratio standard deviation correction value to determine whether the driver has shallow sleepiness. (Procedure S18).

  FIG. 17 shows an example of a method for determining drowsiness based on the heartbeat fluctuation low frequency component standard deviation correction value. In the method shown in the figure, the heartbeat fluctuation low frequency component standard deviation correction value is compared with a preset shallow drowsiness detection threshold, and when the heartbeat fluctuation low frequency component standard deviation correction value is higher than the shallow drowsiness detection threshold, When it is determined that there is shallow sleepiness and the heartbeat fluctuation low frequency component standard deviation correction value is lower than the shallow sleepiness detection threshold, it is determined that there is no sleepiness.

  Note that the presence or absence of shallow sleepiness is similarly determined when using the heart rate standard deviation correction value, the heart rate fluctuation high frequency component standard deviation correction value, and the heart rate fluctuation ratio standard deviation correction value.

  Another method for determining drowsiness is shown in FIG. The method shown in FIG. 2 uses a standard deviation correction value and an average value of the heart rate feature value in combination to determine two-dimensionally whether there is shallow sleepiness.

  Specifically, the standard deviation correction value and the average value data of the heart rate feature value are expressed in two-dimensional coordinates, and the sleepiness level is determined from the data distribution obtained at that time. When data is gathered on the side where both the standard deviation correction value and the average value are large, it is determined that there is shallow sleepiness, and data is gathered on the side where both the standard deviation correction value and the mean value are small. When it is determined that there is no sleepiness.

  FIG. 19 shows still another method for determining drowsiness. The method shown in FIG. 1 uses a standard deviation correction value and an average value of the heart rate feature value in combination, and determines one-dimensionally whether there is shallow sleepiness by the Mahalanobis Taguchi method (described above).

  Specifically, the Mahalanobis distance is obtained based on the standard deviation correction value and the average value of the heartbeat feature amount. When the Mahalanobis distance is higher than the preset shallow drowsiness detection threshold, it is determined that there is shallow sleepiness, and when the Mahalanobis distance is lower than the shallow drowsiness detection threshold, there is no sleepiness. It is determined that there is.

  When it is determined in step S18 that there is no drowsiness by the above method, the process returns to step S11 and the processes of steps S11 to S18 are repeatedly executed. On the other hand, when it is determined in step S18 that there is shallow sleepiness, the alarm device 4 is controlled to notify the driver of the occurrence of sleepiness (step S19), and then the procedure returns to step S11.

  In the above, steps S11 to S13 shown in FIG. 8 constitute a heartbeat feature amount extraction unit that extracts a heartbeat feature amount from the heartbeat or pulse measured by the measurement unit 2. The procedures S16 and S17 constitute a fluctuation distribution calculation means for obtaining a fluctuation distribution of the heartbeat feature quantity extracted by the heartbeat feature quantity extraction means. The procedure S18 constitutes sleepiness level determination means for determining the sleepiness level of the subject using the fluctuation distribution of the heart rate feature value obtained by the fluctuation distribution calculation means.

  Further, the procedure S15 constitutes an average value calculation means for obtaining an average value of the heartbeat feature values extracted by the heartbeat feature value extraction means. The procedure S14 constitutes a reference time width setting means for setting a reference time width of a heartbeat feature value referred to in order to obtain a standard deviation of the heartbeat feature value.

  As described above, in the present embodiment, focusing on the heart rate affected by the autonomic nervous activity related to the occurrence of sleepiness, the heart rate and heart rate fluctuation are extracted by measuring the heart rate or pulse of the driver, The standard deviation (variation) of the heart rate and heart rate fluctuation is obtained, and the driver's sleepiness is determined from this standard deviation or both of the standard deviation and the average value. At this time, the drowsiness level of the driver can be determined as an index of the physiological state when driving while having shallow drowsiness to endure drowsiness and return to the awake state. Thereby, the driver's shallow sleepiness can be detected with high accuracy and without depending on the driver. Therefore, it is possible to effectively prevent a drowsy driving by encouraging the driver to restore normal consciousness or rest when there is shallow sleepiness.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the driver's drowsiness determination is performed using four heart rate feature values of a heart rate value, a heart rate fluctuation low frequency component value, a heart rate fluctuation high frequency component value, and a heart rate fluctuation ratio value. At least one of the heartbeat feature values may be used.

  Further, in the above embodiment, the standard deviation of the heartbeat feature amount is obtained and the driver's sleepiness is determined. However, if it is based on the distribution of the fluctuation amount of the heartbeat feature amount, the standard deviation is used instead of the standard deviation. An error or the like may be used.

  Moreover, although the sleepiness detection apparatus 1 of the said embodiment is mounted in a vehicle, this invention is applicable also to what detects the sleepiness degree of test subjects other than the driver of a vehicle.

It is a table | surface which shows an example of a person's sleepiness level. It is a graph which shows an example of the blink data and drowsiness level data which were collected by the running test of vehicles. It is a table | surface which shows a response | compatibility with a heart rate feature-value and an autonomic nerve activity. It is a graph which shows an example of heart rate data and sleepiness level data which were collected by a run test of vehicles. It is a graph which shows an example of the result of having judged shallow sleepiness using four feature-values. It is a graph which shows an example of the result of having judged shallow sleepiness using eight feature-values. It is a block diagram which shows schematic structure of one Embodiment of the drowsiness detection apparatus concerning this invention. It is a flowchart which shows the detail of the drowsiness detection process procedure performed by drowsiness detection ECU. It is a wave form diagram which shows an example of the output waveform and binarization waveform of a measuring device. It is a wave form diagram which shows an example of the section width of a binarization waveform, and a period time series. It is a wave form diagram which shows an example of the period time series of a heart rate. It is a wave form diagram which shows an example of the waveform obtained by carrying out FFT processing with respect to the period time series of heart rate. It is a wave form diagram which shows the state which set the two frequency band bands with respect to the waveform obtained by FFT processing. It is a wave form diagram which shows an example of the period time series of heartbeat fluctuation. It is a wave form diagram which shows the method of setting the reference area width | variety of a heart rate feature-value. It is a table | surface which shows an example of a heart rate standard deviation value, a heart rate value, and a heart rate standard deviation correction value. It is a wave form diagram which shows the method of determining sleepiness by the heartbeat fluctuation low frequency component standard deviation correction value. It is a conceptual diagram which shows the method to determine drowsiness using the two-dimensional coordinate of the standard deviation correction value and average value of a heart rate feature amount. It is a conceptual diagram which shows the method of determining sleepiness using the Mahalanobis Taguchi method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Sleepiness detection apparatus, 2 ... Measuring instrument (measurement means), 3 ... Sleepiness detection ECU (Heart rate feature-value extraction means, fluctuation distribution calculation means, sleepiness degree determination means, average value calculation means, reference time width setting means)

Claims (7)

A measuring means for measuring the heartbeat or pulse of the subject;
A heartbeat feature amount extraction means for extracting a heartbeat feature amount from a heartbeat or a pulse measured by the measurement means;
A fluctuation distribution calculating means for obtaining a fluctuation distribution of the heartbeat feature quantity extracted by the heartbeat feature quantity extraction means;
A drowsiness detection apparatus comprising: a drowsiness level determination unit that determines the drowsiness level of the subject using the fluctuation distribution of the heartbeat feature value obtained by the fluctuation distribution calculation unit. The fluctuation distribution calculating means obtains a standard deviation of the heartbeat feature quantity as a fluctuation distribution of the heartbeat feature quantity,
The sleepiness detection apparatus according to claim 1, wherein the sleepiness level determination unit determines the sleepiness level of the subject based on a standard deviation of the heartbeat feature amount. An average value calculating means for obtaining an average value of the heartbeat feature values extracted by the heartbeat feature value extracting means;
The fluctuation distribution calculating means obtains a standard deviation of the heartbeat feature quantity as a fluctuation distribution of the heartbeat feature quantity,
2. The sleepiness detection apparatus according to claim 1, wherein the sleepiness level determination means determines the sleepiness level of the subject based on a standard deviation of the heartbeat feature value and an average value of the heartbeat feature value. Reference time width setting means for setting a reference time width of the heartbeat feature value referred to obtain a standard deviation of the heartbeat feature value,
4. The drowsiness detection device according to claim 2, wherein the fluctuation distribution calculating unit obtains a standard deviation of the heartbeat feature amount within a reference time width of the heartbeat feature amount.   5. The reference time width setting means extracts the peak value frequency by performing frequency analysis on the heartbeat feature value, and sets a period corresponding to the peak value frequency as the reference time width. Sleepiness detection device.   6. The fluctuation distribution calculating means includes means for correcting the standard deviation of the heartbeat feature value by dividing the standard deviation of the heartbeat feature value by the heartbeat feature value. The drowsiness detection device according to claim 1.   The heartbeat feature amount is a heart rate, a heartbeat fluctuation low frequency component related to sympathetic nerve activity, a heartbeat fluctuation high frequency component related to parasympathetic nerve activity, a ratio of the heartbeat fluctuation low frequency component and the heartbeat fluctuation high frequency component. The drowsiness detection device according to any one of claims 1 to 6, comprising at least one of them.

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