Biological condition determining device, biological condition determining method, and biological condition determining program

Abstract

To obtain a biological state determination device capable of facilitating acquisition of heartbeat information of a subject and capable of reducing an influence of a variation of the heartbeat information among individuals.SOLUTION: A biological state determination device includes: a base heart rate acquisition part for acquiring a base heart rate of a subject; a heart rate acquisition part for acquiring a heart rate of the subject; and a determination part for determining a state of the subject, using the base heart rate and the heart rate. The heart rate corresponds to the number of crests in an electrocardiographic waveform, meanwhile, the number of crests is matched with the number of contraction times of the heart. Therefore, acquiring the heart rate through acquisition of heartbeat information of the subject is easier to acquire a correct numerical value of the heart rate than through acquisition of a heartbeat interval. Also, the base heart rate is a heart rate during deep sleep specific to each individual, and has a correlation to a heart rate at a normal time. An influence of a variation of heartbeat information among individuals is reduced by determining a state of the subject on the basis of the correlation.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a biological condition determining device, a biological condition determining method, and a biological condition determining program for determining the condition of a subject. [Background technology]

[0002] Conventionally, as a technique for determining drowsiness of a subject, a technique for estimating the activity state of the autonomic nervous system from the frequency spectrum of the heartbeat interval fluctuation is generally known. For example, in the prior art described in the following Patent Document 1, a frequency analysis of the heartbeat interval fluctuation of the subject is performed, and drowsiness is determined using the standard deviation of the frequency components. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4609539 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above prior art, it is necessary to obtain the heartbeat interval of the subject. The heartbeat interval corresponds to the interval between peaks in the waveform of an electrocardiogram, but since there is a time difference between the contraction of the heart, the interval between the peaks of the electrocardiogram and the heartbeat interval may not match. In order to obtain this heartbeat interval accurately, a measurement system that is advanced or has a limited measurement method is required. In addition, since the heartbeat interval, which is a physiological index, varies from person to person, there is a possibility that it may not be determined correctly when a certain threshold value is used.

[0005] In consideration of the above, the present invention aims to provide a biological condition determining device, a biological condition determining method, and a biological condition determining program that make it easy to obtain heart rate information of a subject and reduce the influence of individual variations in the heart rate information. [Means for solving the problem]

[0006] The first aspect The biological condition determination device includes a basal heart rate acquisition unit that acquires the basal heart rate of the subject, a heart rate acquisition unit that acquires the heart rate of the subject, and a determination unit that determines the condition of the subject using the basal heart rate and the heart rate.

[0007] First aspect In the biological condition determination device, the basal heart rate acquisition unit acquires the basal heart rate of the subject, the heart rate acquisition unit acquires the heart rate of the subject, and the determination unit uses the basal heart rate and the heart rate to determine the condition of the subject. The heart rate corresponds to the number of peaks in an electrocardiogram waveform, and the number of peaks corresponds to the number of heart contractions. For this reason, when the heart rate is acquired as the subject's heart rate information, it is easier to obtain a correct value compared to when the heart rate interval is acquired. In addition, the basal heart rate is the heart rate during deep sleep that is unique to an individual, and is correlated with the heart rate during normal times. By determining the condition of the subject based on this correlation, the influence of individual variation in heart rate information is reduced.

[0008] The second aspect The biological condition determining device First aspect In the biological condition determination device, the heart rate acquisition unit acquires the instantaneous heart rate of the subject, calculates an average heart rate which is the average value of the instantaneous heart rates, and calculates a corrected change amount by dividing the change amount per unit time of the average heart rate by the basal heart rate, and the determination unit determines the level of drowsiness of the subject based on whether a state in which the corrected change amount is smaller than a first reference value, which is a negative value, continues for a certain period of time.

[0009] Second Aspect In the biological condition determination device, the heart rate acquisition unit acquires the instantaneous heart rate of the subject, calculates an average heart rate which is the average of the instantaneous heart rates, and calculates a corrected change amount obtained by dividing the change amount per unit time of the average heart rate by the basal heart rate. The determination unit determines the subject's drowsiness level based on whether or not a state in which the corrected change amount is smaller than a first reference value, which is a negative value, continues for a certain period of time, i.e., whether or not a state in which the average heart rate has a strong tendency to decrease continues for a certain period of time. This makes it possible to accurately determine the subject's drowsiness level.

[0010] The third aspect The biological condition determining device Second Aspect In the biological condition determination device, the heart rate acquisition unit calculates the standard deviation of the average heart rate, and the determination unit, when the state continues for a certain period of time, further determines the degree of drowsiness based on whether the instantaneous heart rate is smaller than a first coefficient multiplied by the basal heart rate, while, when the state does not continue for a certain period of time, further determines the degree of drowsiness based on whether the standard deviation is smaller than a second coefficient multiplied by the basal heart rate.

[0011] Third aspect In the biological condition determining device, the heart rate acquiring unit calculates the standard deviation of the average heart rate. If the state in which the above-mentioned corrected change amount is smaller than the first reference value continues for a certain period of time, the determining unit further determines the subject's drowsiness level based on whether or not the instantaneous heart rate is smaller than a first coefficient multiplied by the basal heart rate. On the other hand, if the above-mentioned state does not continue for a certain period of time, the determining unit further determines the subject's drowsiness level based on whether or not the above-mentioned standard deviation is smaller than a second coefficient multiplied by the basal heart rate. By adding any one of these determinations, the accuracy of determining the drowsiness level can be improved.

[0012] The fourth aspect The biological condition determining device Second Aspect In the biological condition determination device, when the state continues for a certain period of time, the determination unit further determines the degree of drowsiness based on whether the instantaneous heart rate is smaller than a third coefficient multiplied by the basal heart rate, and when the state does not continue for a certain period of time, the determination unit further determines the degree of drowsiness based on whether the instantaneous heart rate is smaller than a fourth coefficient multiplied by the basal heart rate.

[0013] Fourth aspectIn the biological condition determining device, when the state in which the above-mentioned corrected change amount is smaller than the first reference value continues for a certain period of time, the determining unit further determines the drowsiness level based on whether or not the instantaneous heart rate is smaller than a third coefficient multiplied by the basal heart rate. On the other hand, when the above-mentioned state does not continue for a certain period of time, the determining unit further determines the drowsiness level based on whether or not the instantaneous heart rate is smaller than a fourth coefficient multiplied by the basal heart rate. By adding any one of these determinations, the accuracy of determining the drowsiness level can be improved.

[0014] Fifth aspect The biological condition determining device according to the present invention is Second Aspect ~ Fourth aspect Any one of One aspect The biological condition determination device described in the above is provided with a body movement acquisition unit that acquires information on the body movement of the subject, and the determination unit further determines the degree of drowsiness using the body movement information after making a determination using the basal heart rate and the heart rate.

[0015] Fifth aspect The biological condition determining device includes a body movement acquiring unit that acquires information on the body movement of the subject. After the determination using the basal heart rate and the heart rate, the determining unit further determines the drowsiness level of the subject using the detection result of the body movement detecting unit. By adding this determination, the accuracy of the determination of the drowsiness level can be improved.

[0016] Sixth Aspect The biological condition determination method of the present invention includes a basal heart rate acquisition step of acquiring a basal heart rate of a subject, a heart rate acquisition step of acquiring the heart rate of the subject, and a determination step of determining the condition of the subject using the basal heart rate and the heart rate.

[0017] Sixth AspectAccording to the biological condition determination method, the basal heart rate acquisition step acquires the basal heart rate of the subject, the heart rate acquisition step acquires the heart rate of the subject, and the determination step uses the basal heart rate and the heart rate to determine the subject's condition. The heart rate corresponds to the number of peaks in an electrocardiogram waveform, and the number of peaks corresponds to the number of heart contractions. Therefore, when the heart rate is acquired as the subject's heart rate information, it is easier to obtain a correct value compared to when the heart rate interval is acquired. In addition, the basal heart rate is the heart rate during deep sleep that is unique to an individual, and is correlated with the heart rate during normal times. By determining the subject's condition based on this correlation, the influence of individual variation in heart rate information is reduced.

[0018] The seventh aspect The method for determining a biological condition is Sixth Aspect In the method for determining a biological condition, in the heart rate acquisition step, the instantaneous heart rate of the subject is acquired, an average heart rate which is the average value of the instantaneous heart rates is calculated, and a corrected change amount is calculated by dividing the change amount per unit time of the average heart rate by the basal heart rate, and in the determination step, the subject's level of drowsiness is determined based on whether or not a state in which the corrected change amount is smaller than a first reference value which is a negative value continues for a certain period of time.

[0019] Seventh aspect According to the biological condition determination method, in the heart rate acquisition step, the instantaneous heart rate of the subject is acquired, an average heart rate which is the average value of the instantaneous heart rates is calculated, and a corrected change amount is calculated by dividing the change amount of the average heart rate per unit time by the basal heart rate. In the determination step, the subject's drowsiness level is determined based on whether or not a state in which the corrected change amount is smaller than a first reference value, which is a negative value, continues for a certain period of time, i.e., whether or not a state in which the average heart rate has a strong tendency to decrease continues for a certain period of time. This makes it possible to accurately determine the subject's drowsiness level.

[0020] The eighth aspect The method for determining a biological condition is Seventh aspectIn the biological condition determination method, in the heart rate acquisition step, a standard deviation of the average heart rate is calculated, and in the determination step, if the state continues for a certain period of time, the degree of drowsiness is further determined based on whether the instantaneous heart rate is smaller than a first coefficient multiplied by the basal heart rate, while if the state does not continue for a certain period of time, the degree of drowsiness is further determined based on whether the standard deviation is smaller than a second coefficient multiplied by the basal heart rate.

[0021] Eighth aspect According to the biological condition determination method, in the heart rate acquisition step, the standard deviation of the average heart rate is calculated. In the determination step, if the state in which the above-mentioned corrected change amount is smaller than the first reference value continues for a certain period of time, the subject's drowsiness level is further determined based on whether or not the instantaneous heart rate is smaller than a first coefficient multiplied by the basal heart rate. On the other hand, if the above-mentioned state does not continue for a certain period of time, in the determination step, the subject's drowsiness level is further determined based on whether or not the above-mentioned standard deviation is smaller than a second coefficient multiplied by the basal heart rate. By adding any one of these determinations, the accuracy of determining the drowsiness level can be improved.

[0022] The ninth aspect The method for determining a biological condition is Seventh aspect In the biological condition determination method, in the determination step, if the state continues for a certain period of time, the degree of drowsiness is further determined based on whether the instantaneous heart rate is smaller than a third coefficient multiplied by the basal heart rate, whereas if the state does not continue for a certain period of time, the degree of drowsiness is further determined based on whether the instantaneous heart rate is smaller than a fourth coefficient multiplied by the basal heart rate.

[0023] Ninth aspect According to the biological condition determination method, in the determination step, if the state in which the above-mentioned correction change amount is smaller than the first reference value continues for a certain period of time, the drowsiness level is further determined based on whether or not the instantaneous heart rate is smaller than a third coefficient multiplied by the basal heart rate. On the other hand, if the above-mentioned state does not continue for a certain period of time, in the determination step, the drowsiness level is further determined based on whether or not the instantaneous heart rate is smaller than a fourth coefficient multiplied by the basal heart rate. By adding any one of these determinations, the accuracy of determining the drowsiness level can be improved.

[0024] The tenth aspect The method for determining a biological condition is Seventh aspect ~ Ninth aspect Any one of One aspect The method for determining a biological condition includes a body movement acquisition step for acquiring information on the body movement of the subject, and in the determination step, after a determination is made using the basal heart rate and the heart rate, the degree of drowsiness is further determined using the body movement information.

[0025] Tenth aspect The biological condition determination method includes a body movement acquisition step of acquiring information on the body movement of the subject. In the determination step, after the determination using the basal heart rate and the heart rate, the drowsiness level of the subject is further determined using the body movement information. By adding this determination, it is possible to improve the accuracy of the determination of the drowsiness level.

[0026] The eleventh aspect The biological status determination program is Sixth Aspect ~ Tenth aspect Any one of One aspect The processor executes each step of the biological condition determining method.

[0027] Eleventh aspect The processor executes the above steps according to the biological condition determination program. Sixth Aspect ~ Tenth aspect Any one of One aspect The same effects as those of the above invention can be obtained. Effect of the Invention

[0028] As described above, the biological condition determining device, the biological condition determining method, and the biological condition determining program according to the present invention facilitate acquisition of the subject's heart rate information and reduce the influence of individual variations in the heart rate information. [Brief description of the drawings]

[0029] [Figure 1]1 is a block diagram showing a hardware configuration of a drowsiness determination and warning system including a drowsiness determination and warning device as a biological condition determining device according to a first embodiment. [Diagram 2] 1 is a block diagram showing a functional configuration of a drowsiness determination and warning device according to a first embodiment. [Diagram 3] FIG. 11 is an explanatory diagram for explaining how to calculate an average heart rate and a standard deviation. [Figure 4] 5 is a flowchart showing the flow of control processing performed by a drowsiness determination section of the drowsiness determination and warning device according to the first embodiment. [Diagram 5] FIG. 2 is a diagram showing an example of a pulse wave waveform, illustrating a heart rate and a heartbeat interval. [Figure 6] FIG. 11 is a block diagram showing a hardware configuration of a drowsiness determination and warning system including a drowsiness determination and warning device as a biological condition determining device according to a second embodiment. [Figure 7] 10 is a flowchart showing the flow of control processing performed by a drowsiness determination section of a drowsiness determination and warning device according to a second embodiment. [Figure 8] 13 is a flowchart showing the flow of control processing performed by a drowsiness determining section of a drowsiness determining and warning device serving as a biological state determining device according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] <First embodiment> A first embodiment of the present invention will be described below with reference to Fig. 1 to Fig. 5. Fig. 1 shows a drowsiness determination and warning system 10 configured to include a drowsiness determination and warning device 12 as a biological state determination device according to the first embodiment. In addition to the drowsiness determination and warning device 12, this drowsiness determination and warning system 10 is configured to include a basal heart rate acquisition device 14, a biological data accumulation device 16, a heart rate sensor 18, a warning device 20, and another control device 22.

[0031] The drowsiness determination / warning device 12 is mounted on, for example, a vehicle, determines the drowsiness level of the driver of the vehicle, and warns the driver as necessary. The driver corresponds to the "subject" in the present invention. The drowsiness determination / warning device 12 includes a CPU (Central Processing Unit; processor) 12A, a ROM (Read Only Memory) 12B, a RAM (Random Access Memory) 12C, a storage 12D, a communication I / F (Interface) 12E, and an input / output I / F (Interface) 12F. The CPU 12A, the ROM 12B, the RAM 12C, the storage 12D, the communication I / F 12E, and the input / output I / F 12F are connected to each other so as to be able to communicate with each other via a bus 12G.

[0032] The CPU 12A is a central processing unit, and executes various programs and controls each part. That is, the CPU 12A reads out the program from the ROM 12B, and executes the program using the RAM 12C as a working area. In this embodiment, the program is stored in the ROM 12B. This program corresponds to the "biological state determination program" of the present invention. By the CPU 12A executing this program, the drowsiness determination / warning device 12 functions as the storage unit 121, the heart rate index calculation unit 122, the drowsiness determination unit 123, and the warning device control unit 124 shown in FIG. 2.

[0033] The ROM 12B stores various programs and various data. The RAM 12C temporarily stores programs or data as a working area. The storage 12D is configured with an HDD (Hard Disk Drive) or an SSD (Solid State Drive) and stores various programs including an operating system.

[0034] The communication I / F 12E includes an interface for connecting to a network. This network is, for example, a wired and wireless communication network using a public line such as the Internet. As the above interface, for example, a communication standard such as LTE or Wi-Fi (registered trademark) is used. The drowsiness determination and warning device 12 is connected to the basal heart rate acquisition device 14 and the biological data accumulation device 16 via the above network so that they can communicate with each other. In addition, the basal heart rate acquisition device 14 and the biological data accumulation device 16 are connected to each other so that they can communicate with each other via the above network.

[0035] The basal heart rate acquisition device 14 is, for example, a heart rate sensor mounted on a wearable terminal or the like, and measures the basal heart rate of a driver (subject) when the subject is asleep immediately before getting into a vehicle. The basal heart rate is a heart rate that corresponds to one percentile of the distribution (i.e., histogram) of heart rates during sleep. The basal heart rate data measured by the basal heart rate acquisition device 14 is transmitted directly to the drowsiness determination / warning device 12 via a network or indirectly via a biological data accumulation device 16. The biological data accumulation device 16 is, for example, a smartphone or a data server. The biological data accumulation device 16 accumulates basal heart rate data for each subject.

[0036] A heart rate sensor 18, a warning device 20, and another control device 22 are connected to the input / output I / F 12F. The heart rate sensor 18 is, for example, a radio wave type or optical type heart rate meter, and is mounted on a vehicle to measure the instantaneous heart rate of the driver. This instantaneous heart rate is a heart rate measured in the smallest time unit. The warning device 20 is, for example, a sound output device that issues a warning sound, or a vibration output device that applies vibration to the driver for warning, and is mounted on a vehicle or a vehicle seat. The other control device 22 is, for example, a vehicle control device that controls automatic driving of the vehicle, or a display control device that controls a display device mounted on the vehicle. The heart rate sensor 18 may be a heart rate interval sensor that measures the interval between R waves (so-called RRI). In this case, the heart rate information is obtained from the heart rate interval as heart rate (bpm)=60 / RRI.

[0037] As described above, the drowsiness determination / warning device 12 has, as functional configurations, a storage unit 121, a heart rate index calculation unit 122, a drowsiness determination unit 123, and a warning device control unit 124, which are shown in Fig. 2. These functional configurations are realized by the CPU 12A reading out and executing a program stored in the ROM 12B. The "biological condition determination method" according to the present invention is implemented by these functional configurations.

[0038] The storage unit 121 acquires data on the basal heart rate measured by the basal heart rate acquisition device 14. In other words, the storage unit 121 corresponds to the "basal heart rate acquisition unit" in the present invention, and has a function of performing the "basal heart rate acquisition step" in the present invention. The storage unit 121 stores the acquired basal heart rate data in the storage 12D or the like. In this case, the storage unit 121 stores the basal heart rate data for each of a plurality of subjects in the storage 12D or the like.

[0039] The heart rate index calculation unit 122 acquires data on the instantaneous heart rate measured by the heart rate sensor 18. In other words, the heart rate index calculation unit 122 corresponds to the "heart rate acquisition unit" of the present invention, and has a function of performing the "heart rate acquisition step" of the present invention. Furthermore, the heart rate index calculation unit 122 calculates an average heart rate, which is the average value of the instantaneous heart rates, and calculates a corrected change amount obtained by dividing the change amount per unit time of the average heart rate by the basal heart rate, and the standard deviation of the average heart rate.

[0040] Specifically, as shown in FIG. 3, the heart rate index calculation unit 122 calculates a plurality of pieces of acquired instantaneous heart rate data HR1, HR2, HR3, . . . HR n By averaging these, the average heart rate HR an The heart rate index calculation unit 122 also calculates the average heart rate data HR an , H.R. an+1 The corrected change in the average heart rate per unit time, X, is calculated using the following formula (1): n In the following formula (1), HR0 is the basal heart rate, and t n is the time.

[0041]

number

[0042] Furthermore, the heart rate index calculation unit 122 uses the calculated data of the average heart rates HR an , H.R. an+1 The standard deviation SD of the average heart rate is calculated using the following formula (2). In the following formula (2), x is HR an ~HR am is the number of data.

[0043]

number

[0044] The drowsiness determination unit 123 determines the basal heart rate HR0 and the instantaneous heart rate HR n and average heart rate HR an In other words, the drowsiness determination unit 123 corresponds to the "determination unit" in the present invention, and has a function of performing the "determination step" in the present invention. This drowsiness determination unit 123 determines the driver's state (here, the degree of drowsiness) using the correction change amount X n , basal heart rate HR0 and instantaneous heart rate HR n The driver's level of drowsiness is judged based on three indicators: the driver's level of drowsiness, comparison with the standard deviation SD, and the mean driving speed.

[0045] Specifically, the correction change amount X n In the determination by the method, the drowsiness determination unit 123 uses the first reference value X c More than the correction change amount X n is small (i.e. X n <X c The degree of drowsiness of the driver is judged based on whether the first reference value X c For example, X is set within the range of -0.0005 to -0.005. n <X c When this condition is met, the average heart rate has a strong tendency to decrease.

[0046] Basal heart rate HR0 and instantaneous heart rate HR n In the determination by comparison with the instantaneous heart rate HR n is the first coefficient Y of the basal heart rate HR0 c In this case, the drowsiness determination unit 123 determines whether the following formula (3) is satisfied. In the following formula (3), the first coefficient Y c is set within the range of 1.2 to 1.7, for example.

[0047]

number

[0048] In the judgment based on the standard deviation SD, the drowsiness judgment unit 123 calculates the standard deviation SD by multiplying it by a second coefficient SD c In this case, the drowsiness determination unit 123 determines whether the following formula (4) is satisfied. In the following formula (4), the second coefficient SD c is set within the range of 0.003 to 0.03.

[0049]

number

[0050] The warning device control unit 124 controls the operation of the warning device 20 as set in advance according to the degree of drowsiness (drowsiness level) of the driver determined by the drowsiness determination unit 123. For example, when the driver is at a light stage of drowsiness, the warning device control unit 124 issues a warning with a warning sound, vibration, or the like that does not lead to discomfort for the driver. On the other hand, when the driver is at a deep stage of drowsiness (dozing state) and there is a high urgency in waking up the driver, the warning device control unit 124 issues a strong warning to the driver. In this way, it is expected that issuing a warning according to the drowsiness level determined by the drowsiness determination unit 123 will effectively encourage the driver to wake up.

[0051] The determination result of the drowsiness determination unit 123 is also output to the other control device 22 via the input / output I / F 12F and is used for control in the other control device 22. Note that the subject's sleep state (time of deep sleep) on the previous day may be estimated from the heart rate measured by the basal heart rate acquisition device 14, and a warning may be issued when the subject is driving a vehicle, or the result may be used for automatic driving control of the vehicle.

[0052] Hereinafter, the flow of the control process performed by the drowsiness determination and warning device 12 will be described with reference to the flowchart shown in Fig. 4. In this control process, the CPU 12A of the drowsiness determination and warning device 12 classifies the degree of drowsiness (drowsiness level) of the driver into four levels, from level 0 (awake) to level 3 (deep drowsiness), by the function of the drowsiness determination unit 123. First, in step S1 of Fig. 4, the CPU 12A calculates the correction change amount X n is the first reference value X c If the determination is affirmative, the process proceeds to step S2, and if the determination is negative, the process proceeds to step S3.

[0053] When the process proceeds to step S2, the CPU 12A calculates the instantaneous heart rate HR n is the first coefficient Y of the basal heart rate HR0 c If the determination in step S2 is positive, the driver's drowsiness level is determined to be level 3, which is a deep drowsiness level. On the other hand, if the determination in step S2 is negative, the driver's drowsiness level is determined to be level 2, which is one level lighter than level 3.

[0054] When the step proceeds to step S3, the CPU 12A calculates the standard deviation SD of the average heart rate by multiplying the second coefficient SD of the basal heart rate HR0 by c If the determination in step S3 is positive, the driver's drowsiness level is determined to be Level 1, which is one level lighter than Level 2. On the other hand, if the determination in step S3 is negative, the driver's drowsiness level is determined to be Level 0, which is the wakefulness level.

[0055] (Summary of this embodiment) According to this embodiment, the CPU 12A of the drowsiness determination / warning device 12 determines the driver's state (drowsiness in this case) using the driver's basal heart rate and heart rate (instantaneous heart rate and average heart rate) by the function of the drowsiness determination unit 123. As shown in FIG. 5, the heart rate corresponds to the number of peaks in the electrocardiogram waveform, and the number of peaks coincides with the number of cardiac contractions. On the other hand, the heartbeat interval corresponds to the interval between peaks in the electrocardiogram waveform, but since there is a time difference between the cardiac contractions, the peak interval of the electrocardiogram and the heartbeat interval may not coincide. Therefore, when the heart rate is obtained as the driver's heartbeat information, it is easier to obtain a correct numerical value than when the heartbeat interval is obtained.

[0056] In addition, the basal heart rate is the heart rate during deep sleep specific to an individual, and is correlated with the normal heart rate. By judging the driver's state based on this correlation, the influence of individual variations in heart rate information is reduced, so that a correct judgment can be made even when a certain threshold value is used in the judgment algorithm. As a result, it is possible to give the driver an appropriate warning according to the driver's level of drowsiness.

[0057] In this way, in this embodiment, the heart rate, which is easy to obtain a correct value, is used for judgment, so the cost of the sensor for obtaining the heart rate information can be reduced. Moreover, since complex analysis such as frequency analysis is not performed, the cost of the CPU 12A, which is the calculation device, can also be reduced.

[0058] In this embodiment, the heart rate index calculation unit 122 acquires the instantaneous heart rate of the driver, calculates an average heart rate which is the average value of the instantaneous heart rates, and calculates a corrected change amount obtained by dividing the change amount of the average heart rate per unit time by the basal heart rate. The drowsiness determination unit 123 determines the drowsiness level of the driver based on whether or not a state in which the corrected change amount is smaller than the first reference value, which is a negative value, continues for a certain period of time, i.e., whether or not a state in which the average heart rate has a strong tendency to decrease continues for a certain period of time. In this way, by dividing (correcting) the change amount of the average heart rate per unit time by the basal heart rate, the drowsiness level of the driver can be accurately determined.

[0059] Furthermore, in this embodiment, the heart rate index calculation unit 122 calculates the standard deviation of the average heart rate. If the state in which the above-mentioned correction change amount is smaller than the first reference value continues for a certain period of time, the drowsiness determination unit 123 further determines the driver's drowsiness level based on whether or not the instantaneous heart rate is smaller than a first coefficient multiplied by the basal heart rate. On the other hand, if the above-mentioned state does not continue for a certain period of time, the drowsiness determination unit 123 further determines the driver's drowsiness level based on whether or not the above-mentioned standard deviation is smaller than a second coefficient multiplied by the basal heart rate. By adding at least one of these determinations, the accuracy of the determination of the drowsiness level can be improved.

[0060] Next, another embodiment of the present invention will be described. Note that the same reference numerals as in the first embodiment are given to the configurations and operations that are basically the same as those in the first embodiment, and the description thereof will be omitted.

[0061] <Second embodiment> Fig. 6 is a block diagram showing a hardware configuration of a drowsiness determination and warning system 30 including a drowsiness determination and warning device 12 as a biological state determination device according to a second embodiment of the present invention. Fig. 7 is a flowchart showing a flow of control processing of the drowsiness determination and warning device 12 according to the second embodiment.

[0062] As shown in Fig. 6, the drowsiness determination warning system 30 according to this embodiment includes a body movement sensor 32. The body movement sensor 32 is, for example, a wearable acceleration sensor worn by the driver to detect the body movement (acceleration) of the driver, or a camera-type sensor mounted on a vehicle to capture an image of the driver and detect the body movement of the driver by image analysis. This body movement sensor 32 is connected to the drowsiness determination warning device 12 via a network so as to be able to communicate with each other. A drowsiness determination unit 123, which is a functional configuration of the drowsiness determination warning device, serves both as the "determination unit" and the "body movement acquisition unit" in the present invention, and acquires information on the body movement of the driver from the body movement sensor 32.

[0063] 7, in this embodiment, the CPU 12A of the drowsiness determination and warning device 12 performs the same processes as in the first embodiment in steps S1 to S3, but if the determination in step S2 is positive, the process proceeds to step S4, and if the determination in step S3 is positive, the process proceeds to step S5. In steps S4 and S5, the "body movement acquisition step" of the present invention is performed.

[0064] When the process proceeds to step S4, the CPU 12A acquires information on the body movement of the driver (acceleration information) from the body movement sensor 32, and determines whether the acceleration is smaller than the second reference value. If the determination in step S4 is positive, the driver's drowsiness level is determined to be level 3, which is a deep drowsiness level. On the other hand, if the determination in step S4 is negative, the driver's drowsiness level is determined to be level 2, which is one level lighter than level 3.

[0065] Similarly, when the process proceeds to step S5, CPU 12A acquires information on the body movement of the driver (acceleration information) from body movement sensor 32, and determines whether the acceleration is smaller than the second reference value. If the determination in step S5 is positive, the driver's drowsiness level is determined to be level 1, which is one level lighter than level 2. On the other hand, if the determination in step S5 is negative, the driver's drowsiness level is determined to be level 0, which is the wakefulness level.

[0066] In this embodiment, the configuration other than the above is the same as that of the first embodiment. In this embodiment, after the determination using the basal heart rate and the heart rate, the driver's drowsiness level is further determined using information on body movement. By adding this determination, the accuracy of the determination of the drowsiness level can be further improved.

[0067] <Third embodiment> 8 is a flowchart showing a flow of control processing performed by a drowsiness determination unit of a drowsiness determination and warning device as a biological state determination device according to a third embodiment of the present invention. In this embodiment, if the determination in step S1 is positive, the process proceeds to step S6, and if the determination in step S1 is negative, the process proceeds to step S7.

[0068] When the process proceeds to step S6, the CPU 12A calculates the instantaneous heart rate HR n is the third coefficient Y of the basal heart rate HR0 c1 Is it smaller than HR? n <Y c1 ×HR0 is satisfied. If the determination in step S6 is positive, the driver's drowsiness level is determined to be level 3, which is a deep drowsiness level. On the other hand, if the determination in step S6 is negative, the driver's drowsiness level is determined to be level 2, which is one level lighter than level 3.

[0069] When the process proceeds to step S7, the CPU 12A calculates the instantaneous heart rate HR n is the fourth coefficient Y of the basal heart rate HR0 c2 Is it smaller than HR? n <Y c2 Determine whether or not the above third coefficient Y ×HR0 holds. c1 and the fourth coefficient Y c2 is set within the range of 1.2 to 1.7, for example, and the fourth coefficient Y c2 is the third coefficient Y c1 It is set larger than (Y c1 <Y c2If the determination in step S7 is positive, the driver's drowsiness level is determined to be Level 1, which is one level lighter than Level 2. On the other hand, if the determination in step S7 is negative, the driver's drowsiness level is determined to be Level 0, which is the wakefulness level.

[0070] In this embodiment, the configuration other than the above is the same as that of the first embodiment. In this embodiment, the determination of step S6 or step S7 is added after the determination of step S1, so that the accuracy of determining the drowsiness level can be improved.

[0071] <Supplementary explanation of the embodiment> In each of the above embodiments, the drowsiness determination and warning device 12 as the biological condition determination device is used to determine the drowsiness level of the driver (subject), but the present invention is not limited to this. The biological condition determination device according to the present invention may be one that determines the stress state of the subject using, for example, the basal heart rate and the heart rate of the subject.

[0072] In addition, in each of the above embodiments, the drowsiness determination warning device 12 as a biological condition determination device is configured to be mounted in a vehicle, but this is not limited to the above, and the biological condition determination device may be a mobile terminal (smartphone, tablet terminal, etc.) that can be taken out of the vehicle.

[0073] In each of the above embodiments, various processors other than the CPU may execute each process executed by the CPU 12A by reading the software (program). In this case, examples of the processor include a PLD (Programmable Logic Device) such as an FPGA (Field-Programmable Gate Array) whose circuit configuration can be changed after manufacture, and a dedicated electric circuit such as an ASIC (Application Specific Integrated Circuit) which is a processor having a circuit configuration designed exclusively for executing a specific process. Each process may be executed by one of these various processors, or may be executed by a combination of two or more processors of the same or different types (for example, a plurality of FPGAs, a combination of a CPU and an FPGA, etc.). More specifically, the hardware structure of these various processors is an electric circuit that combines circuit elements such as semiconductor elements.

[0074] In each of the above embodiments, the programs are described as being stored (installed) in advance in a non-transitory recording medium that can be read by a computer. For example, in the drowsiness determination and warning device 12, the programs are stored in advance in the storage 12D. However, the present invention is not limited to this, and the programs may be provided in a form recorded in a non-transitory recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a USB (Universal Serial Bus) memory. Furthermore, each program may be downloaded from an external device via a network.

[0075] The flow of the control process described in each of the above embodiments is also an example, and unnecessary steps may be deleted, new steps may be added, or the processing order may be changed, without departing from the spirit of the invention.

[0076] In addition, the present invention can be practiced with various modifications without departing from the spirit and scope of the present invention. Furthermore, the scope of the present invention is not limited to the above-described embodiments. [Explanation of symbols]

[0077] 12 Drowsiness detection and warning device (biological condition detection device) 12A CPU (Processor) 121 Memory unit (basal heart rate acquisition unit) 122 Heart rate index calculation unit (heart rate acquisition unit) 123 Drowsiness judgment unit (judgment unit)

Claims

1. A basal heart rate acquisition unit that acquires a basal heart rate of the subject; A heart rate acquisition unit that acquires a heart rate of the subject; a determination unit that determines a state of the subject using the basal heart rate and the heart rate; Equipped with the heart rate acquisition unit acquires an instantaneous heart rate of the subject, calculates an average heart rate which is an average value of the instantaneous heart rates, and calculates a corrected change amount obtained by dividing a change amount per unit time of the average heart rate by the basal heart rate; The biological condition determining device, wherein the determining unit determines a level of drowsiness of the subject based on whether or not a state in which the correction change amount is smaller than a first reference value, which is a negative value, continues for a certain period of time.

2. The heart rate acquisition unit calculates a standard deviation of the average heart rate, 2. The biological condition determination device of claim 1, wherein the determination unit, when the state continues for a certain period of time, further determines the degree of drowsiness based on whether the instantaneous heart rate is smaller than a first coefficient multiple of the basal heart rate, and, when the state does not continue for a certain period of time, further determines the degree of drowsiness based on whether the standard deviation is smaller than a second coefficient multiple of the basal heart rate.

3. The biological condition determination device of claim 1, wherein the determination unit further determines the degree of drowsiness based on whether the instantaneous heart rate is smaller than a third coefficient multiple of the basal heart rate when the state continues for a certain period of time, and further determines the degree of drowsiness based on whether the instantaneous heart rate is smaller than a fourth coefficient multiple of the basal heart rate when the state does not continue for a certain period of time.

4. a body movement acquisition unit that acquires information on the body movement of the subject, The biological condition determining device according to any one of claims 1 to 3, wherein the determining unit further determines the degree of drowsiness using information on the body movement after the determination using the basal heart rate and the heart rate.

5. A basal heart rate acquisition step of acquiring a basal heart rate of the subject; a heart rate acquisition step of acquiring a heart rate of the subject; a determining step of determining a state of the subject using the basal heart rate and the heart rate; having In the heart rate acquisition step, an instantaneous heart rate of the subject is acquired, an average heart rate which is an average value of the instantaneous heart rates is calculated, and a corrected change amount is calculated by dividing a change amount of the average heart rate per unit time by the basal heart rate, In the determining step, a level of drowsiness of the subject is determined based on whether or not a state in which the correction change amount is smaller than a first reference value, which is a negative value, continues for a certain period of time.

6. In the heart rate acquisition step, a standard deviation of the average heart rate is calculated, The biological condition determination method of claim 5, wherein in the determination step, if the state continues for a certain period of time, the degree of drowsiness is further determined based on whether the instantaneous heart rate is smaller than a first coefficient multiple of the basal heart rate, and if the state does not continue for a certain period of time, the degree of drowsiness is further determined based on whether the standard deviation is smaller than a second coefficient multiple of the basal heart rate.

7. The biological condition determination method of claim 5, wherein in the determination step, if the state continues for a certain period of time, the degree of drowsiness is further determined based on whether the instantaneous heart rate is smaller than a third coefficient multiple of the basal heart rate, and if the state does not continue for a certain period of time, the degree of drowsiness is further determined based on whether the instantaneous heart rate is smaller than a fourth coefficient multiple of the basal heart rate.

8. a body movement acquiring step of acquiring information on the body movement of the subject; A biological condition determination method according to any one of claims 5 to 7, wherein in the determination step, after a determination using the basal heart rate and the heart rate, the degree of drowsiness is further determined using information on the body movement.

9. A biological condition determination program that causes a processor to execute each step of the biological condition determination method described in any one of claims 5 to 8.

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