JP2000237175A - Mental stress judging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mental stress judging device requiring no large labor for securing the experimental environment generating no sound. SOLUTION: In this mental stress judging device, a time/frequency analysis is applied to the pulsation interval data on the time axis of the heart rate equivalent signal of a subject when a fixed quantity of a load is continuously given to the subject, and the frequency band caused by the mental work load and the other frequency band are discriminated on the frequency axis. The data of the frequency band caused by the mental work load are frequency/time- analyzed, and an analysis is made by using only the pulsation interval data on the time axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mental stress determination device.

[0002]

2. Description of the Related Art In recent years, people have been subjected to various stresses even in a workplace or a place of daily life. In particular, OA
Due to the rapid development of FA, mental stress caused by VDT work (highly intelligent work with low physical load) and monitoring work causes mental overwork and human error. To prevent this, it is important to evaluate mental stress. As a conventional mental stress determination apparatus, there is an apparatus that attempts to determine mental stress by monitoring the rising / falling state of pulse data calculated from pulse wave data.

[0003]

However, in the above-described conventional mental stress determination apparatus, errors occur due to disturbances in the experimental environment, for example, a sudden change in heart rate caused by surrounding noises, and the accuracy of the determination result decreases. In addition, there is a problem that a great deal of labor is required to secure an experimental environment in which no noise or the like is generated. The present invention has been made in view of the above-described conventional problems, and is based on time / pulse interval data on the time axis of a subject's heartbeat-equivalent signal when a continuous and constant load is applied to the subject. Perform frequency analysis, discriminate frequency bands caused by mental workload from other frequency bands on the frequency axis, and analyze frequency / time data of frequency bands caused by mental workload to analyze beats on the time axis. An object of the present invention is to provide a mental stress determination apparatus that does not require much labor to secure an experimental environment in which no noise or the like is generated by performing analysis using only the moving interval data.

[0004]

In order to achieve the above-mentioned object,
The present invention obtains a heartbeat-equivalent signal of a subject when a continuous and constant load is applied to the subject, and performs time-frequency conversion on beat interval data on the time axis of the heartbeat-equivalent signal. A first converting unit, a data specifying unit that specifies only data in a frequency band equal to or lower than a predetermined frequency among the data converted by the first converting unit, -It is characterized by having second conversion means for performing time conversion, and analysis means for performing stress analysis using the beat interval data on the time axis converted by the second conversion means. According to a second aspect of the present invention, in the mental stress determination device according to the first aspect, the predetermined frequency discriminates a frequency band attributable to a mental work load from a frequency band other than that on a frequency axis, and The frequency band is caused by According to a third aspect of the present invention, in the mental stress determination device according to the first or second aspect, data interpolation is performed on beat interval data on a time axis of the heartbeat-equivalent signal.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a schematic configuration diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of how to apply a task, FIG. 3 is an explanatory diagram of a method of acquiring a heartbeat-equivalent signal, and FIG. 4 is an explanatory diagram of a relationship between distribution and stress. It is. FIG. 5 is a diagram illustrating the influence of disturbance. 6 and 7 are explanatory diagrams of a method of analyzing a heartbeat-equivalent signal, and FIG. 8 is an explanatory diagram of a stress determination method.
Reference numeral 10 in FIG. 1 denotes a task device capable of continuously applying a constant amount of load to the subject. For example, as shown in FIG.
The position of 2 is changed and displayed, and the subject is caused to operate the mouse 13 so that the position of the cursor 14 is adjusted to the position of the mark 12. Note that the task device 10 is set so that the task and the rest can be repeated, and it is appropriate that the task is about 1 to 2 minutes and the rest is about 2 to 3 minutes. It is desirable to be able to set variably. As described above, the task device 10 manages the task and the rest time by the timer.

In FIG. 1, reference numeral 20 denotes a heartbeat equivalent signal acquisition / analysis device for acquiring and analyzing a heartbeat equivalent signal of a subject. As an acquisition method, for example, as shown in FIG.
A method in which the electrode 21 is attached to the subject and the cardiac potential signal is measured by the measuring device 22 can be adopted. The method is not limited to the method of acquiring an electrocardiographic signal by attaching electrodes, but a finger is inserted between a light emitting element and a light receiving element provided in a case, and a pulse wave as a heartbeat equivalent signal is detected based on an amount of transmitted light. You may make it. Then, the acquired heartbeat-equivalent signal (hereinafter described as a cardiac potential signal) is analyzed by a method described later.

Reference numeral 30 in FIG. 1 denotes a mental stress judgment circuit for judging the mental burden of the subject based on the analysis result, the details of which will be described later, but will be briefly described here with reference to FIG. FIG. 4A shows a variance value RR.
5 shows the relationship between V and the average heart rate BEAT and mental stress. The variance value RRV is shown in FIG.
An RRI (R-Rinter) indicating an interval on a time axis of a peak of a predetermined level or more of the cardiac potential signal (R wave) shown in (b).
val)

(Equation 1) Is calculated by Also, the average heart rate BEAT
Is

(Equation 2) Is calculated by Here, N is the number of samples of the RRI data. When the calculation is performed while shifting the analysis section in chronological order, the analysis result becomes R as shown in FIG.
It can be represented as a distribution area on the RV-BEAT two-dimensional plane. Specifically, the task state and the rest state are repeatedly imposed on the subject, and from the distribution area, `` the case where the user cannot concentrate on the task at the time of the task '' and `` the case where the person cannot relax at the time of the rest '' are regarded as the cautionary cases which are not healthy. Then, the direction of increase / decrease of the stress is determined from the change of the distribution.

FIG. 5 shows the influence of disturbance in the experimental environment. The temporary disturbance often induces a rapid rise in the heart rate as shown in FIG. The rapid increase in the heart rate causes the beat interval to be extremely low, and in the distribution area on the RRV-BEAT two-dimensional plane, the average heart rate BEAT does not change much in the resting state, but the RRV value takes a large value (FIG. 5). (See (b)). Since the mental stress is determined at the position of the distribution area, the influence of the disturbance results in a large error mixed in the determination result. Therefore, since a steep change due to disturbance appears in a high frequency band, a reduction in the detection accuracy is prevented by removing a high frequency region.

Next, the cardiac potential signal obtained as described above is analyzed according to the flowchart shown in FIG. In step 601, the cardiac potential signal (see FIG. 7A) is
Sampling is performed at z or more, and A / D conversion is performed. In step 602, untargeted signals such as noise due to body movement of the subject and high-frequency noise are removed by filtering the sampled cardiac potential signal. As an example of the filtering, a band-pass filter of, for example, 5 to 30 Hz, a matched filter that prepares a signal of a reference form and correlates with the obtained signal is used. In step 603, the signal level after the filtering is compared with a predetermined value to leave only a signal having a predetermined value or more. In step 604, the RRI (R-R)
Interval) data is detected (see FIG. 7 (b)), and data is created with RRI on the vertical axis and time on the horizontal axis (see FIG. 7 (c)).

In step 605, the new RRI (n)
At the time of data detection, the RRI (n-1) data immediately before the data is referred to the RRI (n-1) to the 0.5 RRI (n-1).
Only the range of (n) is set as the detection range of the next R wave. If the R-wave is missing due to arrhythmia, the RRI data becomes approximately twice as large as the original, so that it is possible to detect the RRI data by this method. This RRI data is regarded as a value containing an error and is used for inconvenience (step 606, FIG. 7D). 0.5
The reason for setting to 1.5 is that it is considered that there is no instantaneous change of 50% or more in the mental task. The arrhythmia in the subject living a normal life returns to the normal pulsation even if the phenomenon occurs, so that the subsequent pulsation can be used again. In step 607, the sampling is converted to regular sampling in a time series by an interpolation process. Originally, since the heartbeat is irregular, the RRI data fluctuates, so that the RRI data detected in step 604 is irregular sampling data in a time series. Therefore, in this step, pseudo signals are inserted at regular intervals on the signal of FIG. 7D to obtain regular sampling data as shown in FIG. 7E. In order to simplify the processing, the level of the pseudo signal is set to the same level as the previous value on the time axis.

Since it has been experimentally confirmed that the degree of variation in the level of the RRI data has a close correlation with the sympathetic parasympathetic nervous activity, variance is used as an index representing this variation. However, there is a possibility that the influence of disturbance is mixed in the obtained RRI data. Therefore, as described above, since the steep fluctuation due to the disturbance appears in a high frequency band, a time / frequency analysis is performed on the interpolated RRI time-series data in step 608 to find a frequency band due to mental work load. About 0.01Hz to 0.5
Identify the low frequency band of Hz.

Next, in step 609, after removing data outside the frequency band due to mental workload, the frequency
Time conversion and reorganization of data on the time axis (FIG. 7 (f)
reference). At step 610, whether the state is the task state or the rest state is determined based on information from a timer which is time-controlled by the task device 10, and at step 611, the section average state value Gt in the task section and the step 612 are determined.
Calculates the section average state value Gr in the rest section, and outputs it to the mental stress determination circuit 30.

The section average state value G is specified as a two-dimensional distribution position of the variance value RRV and the average heart rate BEAT by calculating the variance value RRV and the average heart rate BEAT, respectively.

FIG. 8 is a flowchart for explaining the detailed operation of the mental stress determination circuit 30. In step 801, the difference X1 between the previous task section average state value Gt1 and the rest section average state value Gr1 calculated in steps 611 and 612 of FIG. 6, and the current task section average state value Gt2 and rest section average state value Gr2 Are calculated respectively. In step 802, the difference X2 is compared with the predetermined value Xth. If the difference X2 is larger than the predetermined value Xth, the process ends as a healthy person. If the difference X2 is smaller than the predetermined value Xth, the case requires caution. In the next step 803, the previous value X1 and the current value X2 are compared. If the previous value X1 is equal to the current value X2, there is no change in mental stress in step 805. Previous value X1
If the current value X2 is smaller than the previous value X1, it is determined that the current value X2 is smaller than the previous value X1.

[0015] Basically, a healthy person has a clear difference in response between when temporary stress is applied and when it is not. Looking at the distribution area shown in FIG. 4 (a), under non-mental stress, the distribution areas of the task state and the rest state are distributed at positions separated from each other. As a result, the distribution area is located at the upper left position where the burden is higher than the distribution area in the rest state. This is a normal response given the sympathetic parasympathetic activity. However, in a state under mental stress, which is a constant stress lurking in the background, a phenomenon of non-concentration in the task state and non-relaxation in the rest state occur, and the mutual distribution areas come close to each other. Therefore, a high-precision determination can be made by making a determination based on a temporal change in the section average state distance of each distribution area. In this method, the average heart rate BEAT has been used to focus on the difference in the distribution area on the two-dimensional plane from the variance value RRV in order to obtain a more accurate result. However, even when calculating only the variance RRV of the RRI, A comparison is made between a difference Y2 between the variance value of the current task period and the variance value of the current rest period and a predetermined value to determine whether or not the subject is a healthy person. The difference Y2 from the variance of
By comparing the difference with the difference Y1, it is determined whether the tendency is an increasing tendency, a decreasing tendency, or no change, so that the same effect can be expected simply, though the accuracy is slightly lowered.

As described above, according to the present embodiment, the time / frequency analysis is performed on the beat interval data on the time axis of the subject's heartbeat-equivalent signal when a continuous and constant load is applied to the subject. The frequency band resulting from mental workload is discriminated from the other frequency bands on the frequency axis, and the frequency and time analysis of the frequency band data resulting from mental workload is performed on the frequency axis to beat interval data on the time axis. Since the analysis is performed using only the data, it is possible to remove the influence of disturbance in the experimental environment, for example, a sudden change in the heart rate caused by surrounding noise, and to prevent the accuracy of the determination result from being lowered. There is an effect that a great deal of labor is not required to secure an experimental environment where no noise or the like is generated. Also, data interpolation is performed on the beat interval data on the time axis of the heartbeat equivalent signal (see step 607 / FIG. 7 (e)).
Thereby, there is an effect that the necessary frequency resolution can be ensured. In addition, as mentioned above,
In an experimental environment where the frequency of disturbance is small even without performing frequency conversion and frequency / time conversion, use only data in the area where the data density is high on the two-dimensional plane of the variance RRV and the average heart rate BEAT. Accordingly, data due to disturbance can be easily removed.

[0017]

As described above, according to the present invention, it is possible to eliminate the influence of disturbances in the experimental environment, for example, sudden changes in the heart rate caused by surrounding noises, etc., thereby preventing the accuracy of the judgment result from being lowered. Therefore, there is an effect that a great deal of labor is not required to secure an experimental environment where no noise or the like is generated. Also, by performing data interpolation on the beat interval data on the time axis of the heartbeat equivalent signal,
There is an effect that necessary frequency resolution required for discrimination can be secured. As described above, mental stress, which can be the cause of occupational accidents, is a phenomenon that is difficult for managers and individuals to recognize, and by providing a highly accurate objective index without the influence of disturbance, a wide range of applications can be expected.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of how to apply a task.

FIG. 3 is an explanatory diagram of a method of acquiring a heartbeat-equivalent signal.

FIG. 4 is an explanatory diagram of a relationship between distribution and stress.

FIG. 5 is a diagram illustrating the influence of disturbance.

FIG. 6 is an explanatory diagram of a method for analyzing a heartbeat-equivalent signal.

FIG. 7 is an explanatory diagram of a method of analyzing a heartbeat-equivalent signal.

FIG. 8 is an explanatory diagram of a stress determination method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Task device 11 Display 12 ○ mark 13 Mouse 14 Cursor 20 Heart rate equivalent signal acquisition / analysis device 21 Electrode 22 Measuring machine 30 Mental stress judgment circuit

Claims (3)

[Claims] An acquisition means for acquiring a heartbeat equivalent signal of a subject when a continuous constant amount of load is applied to the subject, and performing time / frequency conversion on beat interval data on a time axis of the heartbeat equivalent signal. First converting means for performing, data specifying means for specifying only data in a frequency band equal to or lower than a predetermined frequency among the data converted by the first converting means, and data specifying means for specifying the data specified by the data specifying means. A mental unit comprising: a second conversion unit for performing frequency / time conversion; and an analysis unit for performing stress analysis using the beat interval data on the time axis converted by the second conversion unit. Stress judgment device. 2. The frequency band according to claim 2, wherein the predetermined frequency is a frequency band caused by mental work load by distinguishing a frequency band caused by mental work load from other frequency bands on a frequency axis. 2. The mental stress determination device according to 1. 3. The mental stress judging device according to claim 1, wherein data interpolation is performed on beat interval data on the time axis of the heartbeat equivalent signal.