KR101659798B1 - Noncontact heart rate monitoring system based on accelerometer attached on a chair and thereof method - Google Patents

Abstract

The present invention is configured to detect an acceleration signal by mounting an acceleration sensor on a surface of a backrest or a hip rest of a chair that is not in contact with a human body, detect a heartbeat from the detected acceleration signal, and calculate a heart rate from the detected heartbeat signal , And a device and a method for measuring a heart rate for a chair of a non-restraint non-contact type.
The present invention relates to a method of driving a chair's heart rate measuring apparatus including an acceleration sensor unit mounted on a backrest portion of a chair or a hip rest portion of a chair that is not in contact with a human body and detects an acceleration signal, And the arithmetic processing unit includes: a peak and trough detection step of detecting peaks and troughs after passing through the digital low-pass filter; A step of calculating an amplitude difference between a peak and a trough, the amplitude difference of the peak and the trough being detected in the peak and trough detection step; And a heart rate calculation step of calculating a heart rate using a peak whose amplitude difference between a peak and a trough detected in the amplitude difference calculation step of the peak and trough is larger than a threshold value.

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a non-contact, non-contact type heart rate measuring apparatus and method,

The present invention is configured to detect an acceleration signal by mounting an acceleration sensor on a surface of a backrest or a hip rest of a chair that is not in contact with a human body, detect a heartbeat from the detected acceleration signal, and calculate a heart rate from the detected heartbeat signal , And a device and a method for measuring a heart rate for a chair of a non-restraint non-contact type.

Workers and teens spend more than one-third of the day sitting in office or school chairs, and the longer they sit, the higher the incidence of cardiovascular disease.

Therefore, it is very important to monitor heart rate (HR) automatically while sitting in a chair. HR monitoring can assess the activity of the autonomic nervous system, so it is possible to predict the degree of cardiovascular disease, evaluate the stress index, and predict the renal failure.

In particular, it is desirable that employees or young people measure HR in the office or school in a non-binding, non-contact manner.

As a non-constrained, non-contact type HR measurement method, the HR extraction method using a Doppler radar is affected by the motion of the surroundings and electromagnetic waves, and the accuracy is low.

Optical Vibration The HR extraction method using optical vibrocardiography requires the use of expensive and complex optical interfaces.

On the other hand, the acceleration sensor is sensitive enough to measure low-cost, minute body shakes, making it easy to monitor HR in everyday life.

In the prior art, Korean Patent Laid-Open No. 10-2013-0137327 relates to a biometric information acquiring device using a chair, in which a contact electrocardiogram sensor is installed on an armrest, a back plate, and a seat, Even if it happens, compensation is possible, so that continuous bio-information can be acquired.

Korean Patent Laid-Open Publication No. 10-2013-0137327 requires a plurality of electrocardiogram sensors to be installed in a chair, and an electrocardiogram sensor mounted on at least one of the armrests, the back plate, and the electrocardiogram sensors mounted on the seat should be in contact with the user's body. Further, it is necessary to provide a complicated program for compensating when an error such as contact failure occurs. Therefore, in the case of Korean Patent Laid-Open No. 10-2013-0137327, a relatively complicated structure is required because the structure is complicated, the price is high, the signal detection is not easy, and the like.

Therefore, there is a demand for a chair that has an acceleration sensor to monitor HR.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of detecting an acceleration signal by mounting an acceleration sensor on a surface of a backrest or a hip rest of a chair which is not in contact with a human body, detecting a heartbeat from the detected acceleration signal, A non-restraint non-contact type heart rate measuring device and method for calculating a heart rate from a signal.

Another object of the present invention is to detect all peak and trough points of an acceleration signal through a digital low-pass filter and determine a threshold using the detected peak and trough points. And calculating a heart rate (HR) using the finally detected peaks by repeating the process of selecting a peak at which the difference between the peaks and the troughs exceeds a threshold value as a point for HR calculation, And a method for measuring the heart rate of a chair.

In order to solve the above problems, an apparatus for measuring a heart rate for a chair according to the present invention comprises: an acceleration sensor unit mounted on a surface of a backrest or a hip rest of a chair which is not in contact with a human body and detecting an acceleration signal; An A / D converter for converting the acceleration signal received by the analog signal processor into a digital signal; an A / D converter for converting the acceleration signal received from the A / D converter to a digital signal; And an arithmetic processing unit for detecting a peak and a trough and for detecting a heart rate using peaks and troughs.

The operation processing unit passes the acceleration signal received from the A / D conversion unit through a digital low-pass filter, detects a trough and a peak in an acceleration signal passed through the digital low-pass filter, and detects a peak and a trough A peak whose amplitude difference exceeds a predetermined threshold is selected as a heartbeat detection peak, and a heartbeat is calculated by using a peak for heartbeat detection.

Alternatively, the operation processing unit may pass the acceleration signal received from the A / D conversion unit through the digital low-pass filter, detect peaks and troughs in the acceleration signal passed through the digital low-pass filter, A peak for a heartbeat detection and a peak for a heartbeat detection preceding a peak for a current heartbeat detection and a peak for a current heartbeat detection are set as a peak for a heartbeat detection, And the heart rate is calculated using the heart rate interval.

Alternatively, the operation processing unit may pass the acceleration signal received from the A / D conversion unit through the digital low-pass filter, detect peaks and troughs in the acceleration signal passed through the digital low-pass filter, A peak for the heartbeat detection is selected as the peak for the heartbeat detection and a time interval between the peak for the heartbeat detection preceding the peak for the current heartbeat detection and the peak for the current heartbeat detection is 0.45 seconds , The time interval between the current heartbeat detection peak and the current heartbeat detection peak is obtained as the heartbeat interval and the heartbeat is calculated using the heartbeat interval.

The amplitude difference between the peak and the trough is detected as the absolute value of the difference between the amplitude of the trough and the amplitude of the peak detected next to the trough.

The threshold,

(Where TH represents a threshold value, PK represents a peak, TR represents a trough, and M represents a total number of peaks or troughs occurring for 3 seconds)

.

The analog signal processing section includes a high-pass filter, an amplifier, and a low-pass filter, and is configured to have a bandwidth of 0.5 Hz to 23.4 Hz by a high-pass filter and a low-pass filter.

The digital low-pass filter is a second-order Butterworth filter with a cut-off frequency of 8 Hz.

Heart rate is calculated by heart rate = 60 / heart rate interval.

The present invention includes an acceleration sensor unit mounted on a surface of a backrest or hip rest of a chair that is not in contact with a human body and detecting an acceleration signal, and an arithmetic processing unit for detecting a heart rate using an acceleration signal received from the acceleration sensor unit Wherein the arithmetic processing unit comprises: a peak and trough detecting step of detecting a peak and a trough after passing through a digital low-pass filter; The arithmetic processing unit includes: an amplitude difference calculating step of detecting a difference between the peak and trough amplitude of the peak and the trough detected at the peak and trough detecting step; The arithmetic processing unit includes a heart rate calculation step of calculating a heart rate using a peak having a difference between an amplitude of a peak and a trough detected in an amplitude difference calculation step of a peak and a trough greater than a threshold value.

The step of calculating the heart rate is a step of calculating the peak value of the peak and the trough when the difference in amplitude between the peak and the trough detected in the step of calculating the amplitude difference between the peak and the trough is larger than the threshold, Comparing the amplitude difference and the threshold value; A heartbeat interval calculating step of determining whether a time interval between a current peak and a previous heartbeat detection peak is greater than 0.45 seconds and a time interval between a current peak and a previous heartbeat detection peak as a heartbeat interval; And a heart rate estimation step of estimating a heart rate at a heart rate interval calculated in the heart rate interval calculation step.

The threshold is obtained by receiving an acceleration signal for 3 seconds through the A / D converter, passing the received acceleration signal through a digital low-pass filter, and generating a peak and trough in the acceleration signal passed through the digital low- ), And calculates the difference between the amplitudes of the peaks and the troughs in all peaks and all troughs, detects the maximum value among the differences in amplitude of the calculated peaks and troughs, and subtracts the value obtained by multiplying the maximum value by 0.6 times the threshold value .

According to the apparatus and method for measuring a heart rate for a chair of the present invention, an acceleration sensor is mounted on a surface of a backrest or a hip rest of a chair that is not in contact with a human body to detect an acceleration signal, a heartbeat is detected from the detected acceleration signal, And the heart rate is calculated from the detected heart rate signal. Thus, it is possible to monitor the heart rate non-restraintively and non-contactly, and relatively simple structure and low price.

In addition, the present invention detects all peak and trough points of an acceleration signal through a digital low-pass filter, determines a threshold using the detected peak and trough points, The process of selecting the peak whose size difference exceeds the threshold value as a point for calculating the heart rate HR (i.e., pulse, beat) is repeated to calculate the heart rate HR using the detected peaks. That is, the present invention uses an acceleration sensor to detect a heart rate, but detects a heart rate in a relatively simple program.

According to the present invention, since a low-speed acceleration sensor can be attached to a task chair used in everyday life to detect a heartbeat, it is possible to monitor a heart rate (HR) in a non-restrained state and a non-contact state in an office or a school.

The method according to the present invention is useful for evaluating the autonomic nervous system of a person living in an office or a school since the heartbeat can be extracted from an acceleration sensor (accelerometer) attached to a chair in a non-contact, non-binding manner. Further, the present invention can be applied to the development of a cardiopulmonary function monitoring system for ubiquitous health care.

Fig. 1 is a block diagram for explaining a schematic configuration of a heart rate measuring apparatus for a chair according to the present invention; Fig.
2 is a block diagram of the analog signal processing unit of FIG.
3 is an explanatory diagram for explaining a signal detection process from the acceleration sensor unit 100 of FIG.
Fig. 4 is a flowchart for explaining an example of driving of the arithmetic processing unit of the chair heart rate measuring apparatus.
5 is a flowchart for explaining the threshold determination step of FIG.
Fig. 6 shows the case where the acceleration sensor unit is mounted on the backrest of the chair in the present invention.
FIG. 7 shows a case where the acceleration sensor unit is mounted on the hip support portion of the chair in the present invention.
8 is an example of electrocardiogram by a heartbeat detected by the acceleration sensor of the present invention and a conventional electrocardiogram device detected at the same time.
9 is an example of a result of correlation analysis between the heart rate by the acceleration sensor of the present invention and the electrocardiogram detected by the conventional ECG apparatus at the same time.
FIG. 10 shows a plot of the instantaneous heart rate by the acceleration sensor of the present invention and the blind Altman plot of the instantaneous heart rate of the electrocardiogram detected by the conventional ECG apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which an apparatus for measuring a heart rate for a non-restricting non-contact chair using an acceleration sensor of the present invention and a method thereof will be described in detail.

Fig. 1 is a block diagram for explaining a schematic configuration of a non-restricting non-contact chair heart rate measuring apparatus of the present invention, Fig. 2 is a configuration diagram of the analog signal processing unit of Fig. 1, FIG. 2 is an explanatory diagram for explaining a signal detection process from the signal processing unit 100 of FIG.

The chairless heart rate measuring apparatus 10 includes an acceleration sensor unit 100, an analog signal processing unit 130, and a digital signal processing unit 200.

3, the acceleration sensor unit 100 is mounted on a surface of the backrest or the hip rest of the chair which is not in contact with the human body, and detects an acceleration signal including a heartbeat signal. The acceleration sensor unit 100 may be a three-axis acceleration sensor.

The analog signal processing unit 130 amplifies an acceleration signal including a heartbeat signal received from the acceleration sensor unit 100 and removes noise.

2, the analog signal processing unit 130 includes a buffer 150, a high pass filter (HPF) 160, an amplifier 170, a low pass filter (LPF) 180, an offset correction unit 190, .

The buffer 150 is mounted on the output terminal of the acceleration sensor unit 100 and performs impedance matching between the acceleration sensor unit 100 and the analog signal processing unit 130 to perform an input / As a circuit, an amplifier with gain of 1 can be used.

A high-pass filter (HPF) 160 passes a signal having a frequency of 0.5 Hz or more to remove noise such as motion artifacts caused by the user's motion. That is, the high pass filter 160 passes a signal having a frequency of 0.5 Hz or more in the acceleration signal including the heartbeat signal received from the acceleration sensor unit 100 through the buffer 150.

The amplifier 170 amplifies the acceleration signal including the heartbeat signal output from the high pass filter (HPF) The gain of the amplifier 170 may be 940.

A low pass filter (LPF) 180 passes a signal having a frequency of 23.4 Hz or less to detect a heartbeat signal in an acceleration signal including a heartbeat signal output from the amplifier 170.

The offset correcting unit 190 receives the acceleration signal including the heartbeat signal output from the low pass filter (LPF) 180, and converts the acceleration signal into a digital signal through the A / D converter 210. The A / The offset correction is performed in accordance with the specifications of the optical system 210.

That is, in order to accurately extract the heartbeat signal from the acceleration sensor unit 100, the analog signal processing unit 130 includes a high-pass filter 160 and a low-pass filter 180 having a bandwidth of 0.5 to 23.4 Hz, a 940- 170). The analog processing unit 130 may be mounted at any position of the chair.

The digital signal processing unit 200 includes an A / D conversion unit 210, an operation processing unit 220, and a memory unit 230. In some cases, the digital signal processing unit 200 may include one microprocessor having an A / A microcontroller having an A / D converter, or a data acquisition device.

The A / D converter 210 converts the acceleration signal including the heartbeat signal received from the analog signal processor 130 into a digital signal.

The operation processing unit 220 detects a peak and a trough point after passing an acceleration signal including a heartbeat signal received from the A / D converter 210 through a digital low-pass filter, The peak at which the size difference exceeds the threshold value is selected as the point for calculating the heart rate HR, that is, the peak for heartbeat detection (corresponding to the R point of the electrocardiogram), the heartbeat interval is detected using the selected peak for heartbeat detection, Estimates the heart rate HR using the heartbeat interval, and transmits the estimated heart rate HR to the external computer 400. Here, the threshold value is determined using Equation (1), which will be described later, using the peak and trough points detected from the acceleration signal for the initial 3 seconds.

The memory unit 230 stores the acceleration signal, the threshold value, and the like received from the A / D converter 210.

The key input unit (not shown) may include a start / end switch, a detection time setting key, and the like.

The external computer 400 displays and stores the transmitted heart rate HR.

Fig. 4 is a flowchart for explaining an example of driving the operation processing unit 220 of the chair-use heart rate measuring apparatus 10, and Fig. 5 is a flowchart for explaining the threshold value determining step of Fig.

5, the acceleration signal for 3 seconds is received through the A / D converter 210 (S110), and the received acceleration signal is converted to a digital low-pass filter 8Hz, 2nd-order Butterworth filter), and all the peaks and troughs in the acceleration signal for 3 seconds passed through the digital low-pass filter are detected (S120) and all peaks and all troughs The difference between the peak and the amplitude of the trough, that is, the difference between the peak and the amplitude of the trough located before the peak is calculated (S130), and the maximum value among the calculated amplitude differences of the peak and trough is detected (S140) 0.6 times the maximum value is calculated (S150), and the threshold value is determined (S100).

The formula for obtaining the threshold value can be expressed as a mathematical expression.

Where TH represents a threshold value, PK represents a peak, TR represents a trough, and M represents the total number of peaks or the total number of troughs generated for 3 seconds.

Here, the peak refers to the maximum point of the convex waveform signal like a ridge, and the trough refers to the minimum point of the concave waveform signal as in the valley. In the present invention, it is assumed that a peak (PK [m]) occurs after a trough (TR [m]).

In the acceleration signal receiving step, the acceleration signal is received through the A / D converter 210 (S210). And detects an acceleration signal during a predetermined detection time (window). That is, the detection time (window) may be a value set at the time of factory shipment, and in some cases, the detection time unit may be set by a key input unit (not shown).

In the peak and trough detection step, the acceleration signal received in the acceleration signal receiving step is passed through a digital low-pass filter, and then peaks and troughs are detected, and all peaks and all troughs are detected in the acceleration signal during the detection time (S220). In the present invention, trops are detected, trops are detected in succession to trops, and thus detected trops and peaks form one set, that is, a pair.

Here, the digital low-pass filter is a second-order Butterworth filter with a cut-off frequency of 8 Hz and is used to separate the frequency bands associated with the heartbeat.

In the amplitude difference calculating step of the peak and trough, the amplitude difference between the peak and the trough, that is, the difference between the trophy and the amplitude of the peak following the trough is calculated (S230). That is, the amplitude difference between the peak and the trough can be regarded as the absolute value of the difference between the amplitude of the trough and the amplitude of the peak detected next to the trough.

It is determined whether the amplitude difference between the peak and the trough detected in the amplitude difference calculation step of the peak and trough is greater than the threshold value in step S240. If the amplitude difference is smaller than or equal to the threshold value, The process returns to the amplitude difference calculation step S230 of calculating the amplitude difference between the next peak and the trough.

If the amplitude difference between the peak and the trough detected in the step of calculating the amplitude difference between the peak and the trough in the step of comparing the amplitude difference and the threshold value of the peak and trough is larger than the threshold value in the step of detecting the time interval between the current peak and the heartbeat detection peak, The current peak is used as a provisional heartbeat detection peak, and the time interval between the previous peak for heartbeat detection and the current peak is detected (S245).

It is determined whether the time interval between the current peak and the previous heartbeat detection peak is greater than 0.45 seconds (S250). If it is smaller than or equal to the current peak, Returns to the amplitude difference calculation step (S230) of the peak and trough at a peak that is not appropriate for the heartbeat detection peak, and calculates the current trough and amplitude difference to the next peak.

If the time interval between the current peak and the full heartbeat detection peak and the time interval between the current peak and the previous heartbeat detection peak in the 0.45 second comparison step (S250) is greater than 0.45 seconds, the current peak Is determined as the current peak for heartbeat detection (S260). Here, the peak for heartbeat detection corresponds to (corresponds to) the R-point (R-peak) of the electrocardiogram.

That is, the peak PK at which the difference in amplitude (magnitude) between the peak PK and the trough TR exceeds the threshold value TH is selected as the point for calculating the heart rate HR, that is, the peak for heartbeat detection. If two peak points (PK) occurred within 90 samples (0.45 seconds), the peak (PK) having the largest size was selected as the heartbeat detection peak (PK).

In the step of calculating the heartbeat interval, the time interval between the detected peak for the heartbeat detection and the peak for the current heartbeat (i.e., the current heartbeat detection peak) in the time interval detection step (S245) As a heartbeat interval (S270).

In the HR estimation step, the heart rate is estimated based on the heart rate interval calculated in the HR interval calculation step (S270) (S280). That is, the heart rate is the heart rate of the heart per minute and can be obtained by the following equation.

Heart rate = 60 / heart rate interval

Whether or not all data within a predetermined detection time has been processed, that is, a difference between the peaks and troughs in the pair of all peaks and troughs within a predetermined detection time (window), is determined and whether or not the data is compared with the threshold value (S290). If there is a pair of peaks and troughs to be processed yet, the process returns to step S230 of calculating the amplitude difference between the peak and the trough to calculate the amplitude difference between the next peak and trough.

If all the data within the predetermined detection time have been processed in the end determination step, that is, if there is no pair of peaks and troughs to be processed any more, the process ends.

3 illustrates the case where the acceleration sensor is mounted on the backrest of the chair. However, the present invention is not limited to this, and the acceleration sensor can be attached to a position where HR can be reflected at any position of the chair. The acceleration sensor may be attached to the backrest portion of the chair or the hip rest portion or the like.

The chair applied to the present invention is not limited to any chair, and is preferably applicable to an office chair to which a semi-synchronized tilting mechanism is applied.

Fig. 6 shows the case where the acceleration sensor unit is mounted on the backrest of the chair in the present invention.

6 (a) is a rear view of a chair having an acceleration sensor attached to a backrest, and Fig. 6 (b) is a side view of a chair having an acceleration sensor attached to a backrest.

FIG. 7 shows a case where the acceleration sensor unit is mounted on the hip support portion of the chair in the present invention.

6 (a) is a side view of a chair equipped with an acceleration sensor unit in a hip rest portion, and FIG. 6 (b) is a bottom view of a chair having an acceleration sensor attached to a backrest.

As shown in Figs. 6 and 7, an acceleration sensor is mounted on a surface of the backrest or the hip rest of the chair that is not in contact with the human body.

In order to evaluate the apparatus and method for measuring a heart rate for a chair according to the present invention, a heart rate signal is detected by a device and a method for measuring a heart rate for a chair of the present invention, and an electrocardiogram is detected using a conventional electrocardiogram detection device. The results were evaluated in synchronization with the results of ECG detection. Through this, the evaluation of the attachment position of the acceleration sensor and the signal of any axis among the three axis acceleration signals reflects HR. In this experiment, the subjects acquired the data for 2 minutes and 30 seconds with no motion, and compared with the electrocardiogram for 2 minutes except for 15 seconds at the beginning and the end of the data to stabilize the acquired data.

As a result, it was found that the anteroposterior direction (z axis in FIG. 3) best reflects HR, and when the acceleration sensor is positioned at the back of the chair, the acceleration signal obtained from the acceleration sensor And the acceleration signal measured at a slight distance from the subject's back without fully resting on the back of the subject best reflected the movement of the heart.

8 is an example of electrocardiogram by a heartbeat detected by the acceleration sensor of the present invention and a conventional electrocardiogram device detected at the same time.

Fig. 8 is a graph showing the heartbeat detection process performed by the acceleration sensor in the present invention in synchronization with the electrocardiogram. In Fig. 8, a signal in the front-rear direction that best reflects the movement of the heart is used among the three-axis acceleration signals.

8A is an acceleration signal received through the A / D converter 210, and is raw data without any signal processing. That is, it is a signal obtained from an acceleration sensor attached to a chair.

8B shows an example in which the acceleration signal received through the A / D converter 210 is passed through the digital low-pass filter and the peak and trough are detected in the output of the peak and trough detection step S220 to be. That is, the acceleration signal of FIG. 8 (a) is the result after the peak and trough detection step (S220). In Fig. 8 (b), the peak points are shown for each pink color, and the trough points are indicated by green circles.

8C shows a step S240 of comparing the difference between the amplitudes of the peaks and the troughs and the threshold value. The amplitude difference between the peaks and the troughs is represented by a bar graph, and the black dotted line represents the threshold value Quot;).

FIG. 8 (d) shows that the heartbeat detection peak is detected in the heartbeat detection peak determination step (S260). 8 (d) shows the peak for heartbeat detection in the digital low-pass filtered acceleration signal as a red circle.

FIG. 8 (e) shows an electrocardiogram detected by a general electrocardiogram device, which is an ECG signal detected by an acceleration sensor of the present invention and detected by the same subject. The R point (R-peak) in the electrocardiogram signal of FIG. 8 (e) is shown as a light blue square.

The heartbeat detection peak (red circle) in FIG. 8 (d) corresponds to the R point (light blue square) in FIG. 8 (e) by a dotted line.

Sensitivity and positive predictivity value for detected heartbeat detection peak PK 'to evaluate the performance of the method of the present invention for extracting the heart rate from an acceleration sensor attached to a chair, Respectively. Since the peak for heartbeat detection (PK ') extracted from the acceleration signal occurs later than the R-point of the electrocardiogram (R-peak), it is generally difficult to evaluate accurately. Therefore, in the present invention, the sample time difference between the first heartbeat detection peak (PK ') and the R point (R-peak) is calculated. After the R point (R-peak) ) Window was taken and the sensitivity (Sen) and positive predictive value (PPV) were calculated by Equation (2).

Here, TP is a true positive when a peak for heartbeat detection (PK ') is detected in a window, FN is a false negative, and a heartbeat detection peak (PK') is not detected within a window. FP is false positive " means that the heartbeat detection peak PK 'is detected outside the window. In addition, correlation analysis was performed to analyze the correlation between beats per minute (BPM) and instantaneous BPM due to ECG signals extracted from the acceleration signal. In order to easily show the degree of difference, (Bland-Altman analysis).

Table 1 shows the results of the sensitivity and the positive predictive value between the heartbeat detection peak (PK ') and the R-point (R-peak) of the electrocardiogram detected from the acceleration signal.

In Table 1, the average sensitivity is 97.81% and the average positive predictive value is 98.49%. Table 1 shows that the heartbeat detection performance of the heart rate monitoring system using the acceleration sensor of the present invention is excellent.

9 is an example of a result of correlation analysis between the heart rate by the acceleration sensor of the present invention and the electrocardiogram (ref. Heart rate) detected by the conventional ECG apparatus at the same time.

FIG. 9 shows a scatter plot and a correlation coefficient (Pearson's correlation coefficient) of an instantaneous heart rate (BPM) of an acceleration signal and an electrocardiogram. The correlation coefficients for the four data sets were 0.98 (p << 0.0001), which was statistically significant.

FIG. 10 shows a Bland-Altman plot of the instantaneous heart rate by the acceleration sensor of the present invention and the instantaneous heart rate of the electrocardiogram detected by the conventional ECG apparatus at the same time

In FIG. 10, * indicates the difference between the instantaneous heart rate (BPM) and the mean value (m = 0.01) and 95% limits of agreement (LOA, -2.40 to 2.42). It can be confirmed that the heart rate (HR) derived from the acceleration sensor is almost equal to the heart rate (HR) by the electrocardiogram, and the difference values are evenly distributed to the acceleration sensor and the HR average value of the electrocardiogram It can be confirmed that it is distributed.

It is to be understood that the present invention is not limited by what has been described above and illustrated in the drawings, and those skilled in the art will recognize that many modifications and variations are possible within the scope of the following claims.

10: chair heart rate measuring device 100: acceleration sensor
130: analog signal processing unit 200: digital signal processing unit
130: analog signal processor 150: buffer
160: High pass filter 170: Amplifier
180: Low pass filter 190: Offset correction section

Claims (15)

An acceleration sensor unit mounted on a surface of the backrest or hip rest of the chair that is not in contact with the human body and detecting an acceleration signal;
An analog signal processing unit for amplifying the acceleration signal received from the acceleration sensor unit and removing noise;
An A / D converter for converting the acceleration signal received by the analog signal processor into a digital signal;
An arithmetic processing unit for detecting a peak and a trough from the acceleration signal received from the A / D converter, and detecting a heart rate using a peak and a trough;
The apparatus for measuring a heart rate of a chair comprising:
The arithmetic processing unit,
The acceleration signal received from the A / D converter is passed through a digital low-pass filter, troughs and peaks are detected in an acceleration signal passed through the digital low-pass filter, and the amplitude difference between the detected peak and trough A peak exceeding a preset threshold value is selected as a peak for heartbeat detection,
Wherein a heart rate is calculated using a peak for heartbeat detection. delete The apparatus according to claim 1,
When calculating the heart rate using the peak for heartbeat detection,
The time interval between the current heartbeat detection peak and the current heartbeat detection peak is obtained as the heartbeat interval,
Wherein the heart rate is calculated using a heart rate interval. The apparatus according to claim 1,
When calculating the heart rate using the peak for heartbeat detection,
The heartbeat detection peak preceding the current heartbeat detection peak and the current heartbeat detection peak when the time interval between the current heartbeat detection peak and the current heartbeat detection peak is greater than 0.45 second, The time interval of the peak for heartbeat detection is obtained as the heartbeat interval,
Wherein the heart rate is calculated using a heart rate interval. The method as claimed in any one of claims 1 to 5,
And the absolute value of the difference between the amplitude of the trough and the amplitude of the peak detected next to the trough is detected. 2. The apparatus of claim 1,

(Where TH represents a threshold value, PK represents a peak, TR represents a trough, and M represents a total number of peaks or troughs occurring for 3 seconds)
Wherein the heart-rate measuring device measures the heart rate of the chair. The apparatus according to claim 1,
A high-pass filter, an amplifier, and a low-pass filter, and has a bandwidth of 0.5 Hz to 23.4 Hz by a high-pass filter and a low-pass filter. 6. The method of claim 5,
Wherein the digital low-pass filter is a second-order butterfly filter having a cut-off frequency of 8 Hz. 5. The method of claim 4,
Wherein the heart rate is calculated by a heart rate = 60 / heart rate interval. An acceleration sensor unit mounted on a backrest portion of the chair or a hip rest portion of the chair to detect an acceleration signal, and an arithmetic processing unit for detecting a heart rate using an acceleration signal received from the acceleration sensor unit, A method of driving a measuring apparatus,
A peak and trough detection step of detecting an acceleration signal received through the A / D conversion unit and a peak and a trough after passing through a digital low-pass filter;
The arithmetic processing unit includes: an amplitude difference calculating step of detecting a difference between the peak and trough amplitude of the peak and the trough detected at the peak and trough detection step;
A calculation unit for calculating a heart rate using a peak having a peak difference larger than a threshold value and a difference between amplitudes of a peak and a trough detected in the amplitude difference calculation step of the peak and trough;
And a controller for controlling the operation of the chair. 11. The method according to claim 10,
When the amplitude difference between the peak and the trough detected in the amplitude difference calculation step of the peak and trough is larger than the threshold value, the amplitude difference and the threshold value comparison between the peak and trough, which detect the time interval between the current peak and the previous heartbeat detection peak step;
A heartbeat interval calculating step of determining whether a time interval between a current peak and a previous heartbeat detection peak is greater than 0.45 seconds and a time interval between a current peak and a previous heartbeat detection peak as a heartbeat interval;
A heart rate estimation step of estimating a heart rate by a heart rate interval calculated in the heart rate interval calculation step;
And a controller for controlling the operation of the chair. 12. The method according to any one of claims 10 to 11,
The acceleration signal for 3 seconds is received through the A / D converter, the received acceleration signal is passed through the digital low-pass filter, and the peak and trough in the acceleration signal passed through the digital low- The amplitude difference between the peaks and the troughs is calculated for all peaks and all troughs. The maximum value among the calculated amplitude differences of peaks and troughs is detected, and a value obtained by multiplying the maximum value by 0.6 times is set as a threshold value Wherein the heart-rate measuring device is configured to measure the heart rate of the chair. 13. The method of claim 12,
Wherein the digital low-pass filter is a 2nd-order Butterworth filter having a cut-off frequency of 8 Hz. 12. The method of claim 11,
Wherein the heart rate is calculated by a heart rate = 60 / heart rate interval. 11. The method of claim 10, wherein the amplitude difference of the peak and trough is &
Wherein the absolute value of the difference between the amplitude of the trough and the amplitude of the peak detected next to the trough is an absolute value.

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