JP2014045814A - Signal processing device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal processing device and program capable of reducing the influence of generated noise.SOLUTION: A signal processing device 9 acquires a past pulse wave signal stored in a storage part 21 (S1), and determines a deviation time corresponding to a pulse wave period (S2). Subsequently, the device calculates an autocorrelation value between an object measurement signal and a measurement signal obtained by shifting backward an immediate-before measurement signal measured immediately before by the deviation time determined at the S2 (S3). Subsequently, the device determines whether or not the object measurement signal has a missing part where the autocorrelation value is less than a predetermined threshold (S4). If there is a missing part (S4: YES), the device extracts a region from a ted to ted0 of a pseudo signal corresponding to the deviation time from a pseudo signal database 33. Subsequently, the device replaces the object measurement signal with the extracted pseudo signal (S6), and outputs the object measurement signal subjected to the replacement to a biological signal information processing part 41 (S7).

Description

  The present invention relates to a signal processing device and a program for processing a biological signal measured from a subject.

  Devices have been developed that use a biological signal such as a pulse wave or an electrocardiographic waveform measured from a subject as an index to determine the health state or sleep state of the subject. Such an apparatus includes a sensor that detects a biological signal and a signal processing device that determines a health state or a sleep state based on the biological signal measured by the sensor.

  When a subject is healthy, attaching a plurality of devices to the body and measuring biological signals is inconvenient for living daily life. For this reason, a technique has been proposed in which a sensor connected to a wireless device is attached to the body, a signal processing device is connected wirelessly to the sensor, and a biological signal is transmitted from the sensor to the signal processing device (see Patent Document 1).

Japanese Patent No. 4665284

  When communicating wirelessly, communication accuracy is lower than when using a communication line, so even if a biological signal is accurately measured by a sensor, the signal processing device receives a signal containing noise. There is a case. In particular, such a problem is likely to occur when the output is suppressed as a result of downsizing the battery or antenna accompanying the downsizing of the sensor-side device.

In addition, depending on the position of the body to which the sensor is attached, there is a problem that the measurement result is easily influenced by the movement of the subject and is easily influenced by disturbances caused by the activities of daily life.
An object of the present invention is to provide a signal processing apparatus and program capable of reducing the influence of generated noise.

  The invention according to claim 1, which has been made to solve the above-described problem, includes a storage unit (21) that stores a biological signal having a periodicity measured from a subject, and the past taken out from the storage unit. It is determined whether or not the biological signal is measured within a predetermined range based on the biological signal (23, 25, 27, 29, S1 to S4), and it is determined that the biological signal is not measured within the predetermined range. In this case, the biological signal is replaced with a pseudo signal created in advance (31, 35, S5 to S6).

  When the biological signal is not measured within the range predicted from the biological signal measured in the past, it can be determined that the probability that the measured biological signal includes noise is high. In the signal processing device, since a biological signal that is highly likely to contain noise is replaced with a pseudo signal, the portion of the biological signal that contains noise is reduced. As a result, it is possible to reduce the risk that an erroneous determination result is output due to noise when determining a health condition or the like based on the biological signal.

  Note that the above-described pseudo signal is a pulse wave signal that is prepared in advance for the purpose of being able to eliminate noise by replacing it with a highly probable biological signal containing noise. Similar signal.

  In addition, the noise described above broadly indicates that the waveform of the biological signal is disturbed due to various causes such as disturbance during acquisition of the biological signal or error during data communication from the sensor to the signal processing device. In addition, it is assumed that noise in the present invention also includes a state in which a biological signal is not input for a certain period due to interruption of communication.

A program according to a sixth aspect is a program for causing a computer to realize the following first and second functions.
A 1st function (S1-S4) determines whether the biological signal which has the periodicity measured from the test subject was measured in the predetermined range based on the past biological signal rather than the said biological signal. The second function (S5 to S6) replaces the biological signal with a pseudo signal when it is determined by the first function that the biological signal is not measured within the predetermined range.

A computer controlled by such a program can exhibit the same operations and effects as those of the signal processing apparatus according to claim 1.
Note that the above program is composed of an ordered sequence of instructions suitable for processing by a computer, and may be stored in a ROM, a RAM, or the like incorporated in the computer and then loaded into the computer for use. These may be loaded into a computer and used via various recording media and communication lines.

Examples of the recording medium include optical disks such as CD-ROM and DVD-ROM, magnetic disks, and semiconductor memories.
Note that the reference numerals in parentheses described in this column and in the claims indicate the correspondence with the specific means described in the embodiment described later as one aspect, and the technical scope of the present invention. It is not limited.

It is a block diagram which shows a biological signal processing system. It is a figure which shows the state which attached the biometric sensor to the test subject's wrist. It is a figure which shows the example of the waveform of a pulse wave signal. It is a functional block diagram of a signal processing device. It is a figure explaining the calculation method of an autocorrelation value. It is a figure which shows the example of an output of an autocorrelation value, (a) is a figure when noise has not generate | occur | produced, (b) is a figure when noise has generate | occur | produced. It is a figure which shows the image of the pseudo signal memorize | stored in the pseudo signal database. It is a figure which shows the pulse wave signal after replacement processing. It is a flowchart which shows the process sequence of a replacement process.

Embodiments of the present invention will be described below with reference to the drawings.
[Example 1]
(1) Configuration of Biological Signal Processing System 1 The biological signal processing system 1 is a system that measures a subject's pulse wave to determine the health state of the subject, and as shown in FIG. A wireless device 5 and a wireless device 7 and a signal processing device 9 are provided.

  The biosensor 3 is a known reflection type pulse wave sensor that is attached in the vicinity of the subject's wrist as shown in FIG. 2 and includes a light emitting element and a light receiving element. This sensor is fixed around the wrist of the subject like a wristwatch by a band. The biological sensor 3 measures a pulse wave signal having a periodicity indicating a change in blood flow in the blood vessel of the subject's arm at a predetermined sampling period, and continuously outputs the pulse wave signal to the wireless device 5.

The pulse wave signal is an example of a biological signal in the present invention. In addition, the biosensor 3 is not limited to the above configuration, and sensors having various configurations can be used.
The wireless device 5 is provided integrally with the biological sensor 3 and transmits a pulse wave signal measured by the biological sensor 3 to the wireless device 7. The wireless device 7 receives the pulse wave signal transmitted from the wireless device 5 and outputs it to the signal processing device 9.

  As shown in FIG. 1, the signal processing device 9 includes a CPU 11, a ROM 13 that stores a program executed by the CPU 11, a RAM 15 that is a storage device used as a work area when the CPU 11 executes a program, and an electrical data Is configured as a computer system including an NVRAM 17 as a non-volatile memory such as a rewritable flash memory or an EEPROM, and realizes a predetermined process by executing a program.

  The signal processing device 9 is a device that performs a process of replacing a noise portion from a pulse wave signal measured by the biosensor 3 with a pseudo signal, and determines a health condition of a subject using the processed signal. In the present embodiment, the presence / absence of noise is determined for each pulse wave signal for one cycle, and if there is noise, processing for replacing with a pseudo signal is performed. For ease of explanation, the pulse wave signal for one period is hereinafter simply referred to as a measurement signal.

An example of a pulse wave signal is shown in FIG. In FIG. 3, measurement signals A, B, C, D, and E are sequentially measured from the newly measured measurement signal. In this embodiment, each measurement signal uses a pulse wave having a length of one cycle centered on the peak point P of the pulse wave as one measurement signal. In the figure, t _n , t _n-1 and t _n-2 are time intervals of the peak point P of the measurement signal.

  As shown in FIG. 4, the signal processing device 9 includes a storage unit 21, a past biological signal acquisition unit 23, a shift time determination unit 25, an autocorrelation calculation unit 27, a lack determination unit 29, a pseudo signal extraction unit 31, and a pseudo signal database. 33, functions as a biological signal synthesis unit 35 and a biological signal information processing unit 41.

  The storage unit 21 is a storage device that stores the pulse wave signal transmitted from the wireless device 7 in association with time information, and executes the storage process according to a control signal from the CPU 11. The RAM 15 or NVRAM 17 can be used as the storage unit 21.

  The past biological signal acquisition unit 23 extracts, from the pulse wave signal stored in the storage unit 21, a pulse wave signal measured in the past from the measurement signal to be determined for which noise should be determined. Hereinafter, the determination target measurement signal is referred to as a target measurement signal. In addition, a measurement signal measured immediately before the target measurement signal is hereinafter referred to as a previous measurement signal. In FIG. 3, when the measurement signal A is the target measurement signal, the measurement signal B becomes the immediately preceding measurement signal.

Note that the above-described past means the past of the time of the target measurement signal, and the target measurement signal itself does not have to be the latest measurement signal. The same applies to the following description.
The deviation time determination unit 25 obtains a deviation time that is a time difference between the immediately preceding measurement signal and the target measurement signal. The shift time is a time corresponding to the period of the pulse wave.

  The shift time can be obtained based on the time interval of the peak point P of the measurement signal. However, if noise occurs in the target measurement signal, the position of the peak point is not accurate, and the shift time may not be obtained accurately. There is sex. Therefore, the period of the pulse wave signal is calculated based on the immediately preceding measurement signal and the previous measurement signal, and the time is used as the shift time.

A specific calculation method will be described. 3, respectively tP _n the time of the peak of the measurement signal B to E, and _{tP n-1, tP n-} 2, tP n-3.
The peak interval can be expressed as t _n = (tP _n ) − (tP _n−1 ).

Here, when the shift time t _i is calculated by a moving average with a forgetting factor of three times, it can be expressed by the following equation.
t _i = X · (t _n ) + Y · (t _n−1 ) + Z · (t _n−2 ), X + Y + Z = 1
In this embodiment, X = 0.6, Y = 0.3, and Z = 0.1. This represents the shift time when the weight of the most recent peak interval t _n is 60%, the weight of the previous t _n-1 is 30%, and the weight of the previous t _n-2 is 10%. ing. Thereby, the numerical value obtained from the latest signal can be reflected at a high rate. In the present embodiment, t _i is calculated using the past three peak intervals, but the number of times may be two times or four times or more. Coefficients such as X, Y, and Z can be arbitrarily set.

The autocorrelation calculation unit 27 calculates an autocorrelation value between the target measurement signal and the signal obtained by delaying the previous measurement signal, which is a past pulse wave signal extracted from the storage unit 21, by a shift time. A specific calculation method will be described with reference to FIG. 5, based on the time tP of a peak of the measurement signal B, and B'those delayed deviation time t _i.

As described above, since the shift time t _i is a value based on the latest cycle, it is expected that the measurement signal A that is the target measurement signal is also measured in the same cycle. Therefore, when the autocorrelation value between A and B ′ is calculated, a very high value is output if no noise is generated.

The autocorrelation value is a correlation coefficient calculated by the autocorrelation function Cn shown below in this embodiment. Note In the following formulas, r _n are current waveforms, the waveform before the r _nD shifted by D from r _n, L is an arbitrary value.

計測信号Ａにノイズが発生していない場合、具体的には、図５の計測信号Ａの破線部分のような脈波が検出された場合、連続する脈波である計測信号Ａと計測信号Ｂとの間には大きな変化がない蓋然性が高く、図６（ａ）に示すように、自己相関値は閾値（例えば０．８）以上の高い値となる。

When no noise is generated in the measurement signal A, specifically, when a pulse wave such as a broken line portion of the measurement signal A in FIG. 5 is detected, the measurement signal A and the measurement signal B are continuous pulse waves. There is a high probability that there is no significant change between and, and as shown in FIG. 6A, the autocorrelation value is a high value equal to or higher than a threshold (for example, 0.8).

  However, when noise occurs in the measurement signal A as shown by the solid line portion of the measurement signal A shown in FIG. 5 due to, for example, the communication between the wireless devices 5 and 7 being temporarily interrupted, FIG. As shown, the noise generation time ted to the noise end time ted0 are lower than the threshold value.

  The missing determination unit 29 determines whether or not the measured pulse wave signal (target measurement signal) is measured within a predetermined range based on a past pulse wave signal extracted from the storage unit 21. The predetermined range is a range in which the target measurement signal is predicted to be measured based on the past pulse wave signal, and is a range in which it can be estimated that measurement is performed in that range if no noise is generated.

Specifically, when the autocorrelation value between the target measurement signal and the previous measurement signal is equal to or greater than a predetermined threshold, it can be determined that the target measurement signal is measured within a predetermined range based on the previous measurement signal.
On the other hand, when the autocorrelation value is less than the predetermined threshold, it can be determined that the target measurement signal is not measured within the predetermined range. The period from ted to ted0 where it is determined that the pulse wave signal (target measurement signal) is not measured within the predetermined range is estimated to be a missing part in which an accurate signal is missing due to the occurrence of noise. it can. Hereinafter, the part of the period from ted to ted0 in which the autocorrelation value is less than the threshold is described as a missing part.

  The pseudo signal extraction unit 31 replaces the pseudo signal database 33 based on the shift time (pulse wave cycle) determined by the shift time determination unit 25 and the period determined as the missing part by the lack determination unit 29. The pseudo signal to be used is extracted.

  As shown in FIG. 7, the pseudo signal database 33 stores a plurality of pseudo signals corresponding to a plurality of different shift times. The pseudo signal mentioned here is a pulse wave signal created in advance and having no noise. The pseudo signal extraction unit 31 selects a pseudo signal corresponding to the shift time from the plurality of pseudo signals stored in the pseudo signal database 33, and extracts a portion from the ted to the ted0 of the pseudo signal.

  The pseudo signal corresponding to the shift time is a pseudo signal corresponding to the pulse wave period. The waveform of the pulse wave changes with the period. Specifically, if the period is short, one waveform is formed in a short period, so that the slope of the waveform becomes large.

  The pseudo signal database 33 stores a plurality of pseudo signals whose waveform shapes have changed corresponding to different periods, and pseudo signals having an appropriate waveform shape corresponding to the measured pulse wave period are extracted and replaced. As a result, it is possible to prevent the replaced pseudo signal from being greatly different from the pulse waveform measured normally at that time.

  For example, ted and ted0 in the pseudo signal are obtained by adding the time differences Δt1 and Δt2 from the time tP ′ at which the peak point P of the measurement signal B ′ to the ted and ted0 in FIG. 5 to the time tP at the peak point of the pseudo signal. Desired.

  When it is determined that the target measurement signal is not measured within the predetermined range, the biological signal synthesis unit 35 replaces the pseudo signal extracted by the pseudo signal extraction unit 31 with a missing portion in the target measurement signal. Create a signal.

  At that time, the time tP ′ at which the peak point P of the measurement signal B ′ appears (that is, the time that is predicted as the time at which the peak point of the target measurement signal appears) is replaced with the peak point P of the pseudo signal. Thereby, since the part of the period from ted to ted0 in the target measurement signal is replaced with the part of the period from ted to ted0 of the pseudo signal, the pseudo signal can be replaced at an appropriate position.

As a result of such replacement, a pulse wave signal with reduced noise is generated by the pseudo signal 51 as shown in FIG. The generated pulse wave signal is output to the biological signal information processing unit 41.
If the missing determination unit 29 does not determine that there is a missing part, the pseudo signal extraction unit 31 does not extract any pseudo signal, and the biological signal synthesis unit 35 measures the measured target measurement signal. Is output to the biological signal information processing unit 41 as it is.

  The biological signal information processing unit 41 performs a known process such as determination of a health state or a sleep state based on the pulse wave signal output from the signal processing device 9 to determine the state of the subject such as the health state or the sleep state. . In this embodiment, the biological signal information processing unit 41 is formed integrally with the signal processing device 9, but may be a device provided outside the signal processing device 9.

(2) Processing by the Signal Processing Device 9 A processing procedure of replacement processing executed by the CPU 11 of the signal processing device 9 of the biological signal processing system 1 will be described below based on the flowchart shown in FIG.

  In this process, first, a past pulse wave signal stored in the storage unit 21 is acquired (S1), and then a shift time is determined (S2). S1 is a process by the past biological signal acquisition unit 23, and S2 is a process by the shift time determination unit 25. In S <b> 1, a pulse wave signal including the immediately preceding measurement signal that is the measurement signal immediately before the target measurement signal is acquired from the storage unit 21.

  Next, an autocorrelation value between the measurement signal obtained by shifting the previous measurement signal later by the shift time determined in S2 and the target measurement signal is calculated (S3). This S3 is processing by the autocorrelation calculation unit 27. The target measurement signal may be a newly measured measurement signal, or may be a measurement signal already stored in the RAM 15 or NVRAM 17.

  Next, it is determined whether or not there is a missing portion whose autocorrelation value is less than a predetermined threshold in the target measurement signal (S4). This S4 is processing by the missing determination unit 29. If there is a missing part (S4: YES), a region from ted to ted0 of the pseudo signal corresponding to the shift time is extracted from the pseudo signal database 33 (S5). This S5 is processing by the pseudo signal extraction unit 31.

  Next, the target measurement signal is replaced with the extracted pseudo signal (S6), and the replaced target measurement signal is output to the biological signal information processing unit 41 (S7). S6 and S7 are processing by the biological signal synthesizer 35.

  If there is no missing portion in S4 (S4: NO), the target measurement signal is output without any modification to the target measurement signal (S7). After this process, the process returns to S1, and the same process is continued after a predetermined time.

(3) Effect Since the biological signal processing system 1 of the present embodiment described above replaces a highly probable portion containing noise in the pulse wave with a pre-created pseudo signal, the noise portion in the pulse wave is reduced. Is done. As a result, when the biological signal information processing unit 41 determines a health condition or the like based on the pulse wave, it is possible to reduce a risk that an erroneous determination result is output due to noise.

  In addition, since an appropriate pseudo signal corresponding to the shift time (pulse wave period) is extracted from the pseudo signal database and used, the replaced pseudo signal is greatly different from the waveform of the pulse wave when there is no noise measured at that time. It is possible to suppress the occurrence of an erroneous determination result in the biological signal information processing unit 41.

  In addition, when replacing with the pseudo signal, the time predicted as the peak point of the target measurement signal and the peak point of the pseudo signal are made to coincide with each other, so that replacement with high accuracy is possible. Furthermore, since only the portion with a high probability of noise is replaced with the pseudo signal, the portion replaced with the pseudo signal is reduced as much as possible, and accurate information based on the measured signal can be output to the biological signal information processing unit 41. .

  Moreover, since the determination whether the target measurement signal is measured within a predetermined range based on the past pulse wave signal is performed based on whether the autocorrelation value is equal to or greater than a predetermined threshold, the determination Can be performed with high accuracy.

(4) Correspondence Relationship The processing of S1 to S4 in FIG. 9 executed by the CPU 11 of the signal processing device 9 is an example of the processing by the determination unit and the first function of the present invention, and the processing of S5 to S6 is in the present invention. It is an example of the process by a replacement part, and a 2nd function.

[Modification]
As mentioned above, although the Example of this invention was described, it cannot be overemphasized that this invention can take a various form, as long as it belongs to the technical scope of this invention, without being limited to the said Example at all.

  For example, in the above-described embodiment, the configuration of measuring a pulse wave as an example of a biological signal is illustrated, but an electrocardiogram or blood pressure other than the pulse wave may be measured. Further, it may be configured to use these biological signals as they are without performing differentiation processing, that is, a configuration in which waveforms of those original signals are prepared as pseudo signals, or the velocity signals and acceleration signals subjected to differentiation processing are replaced with pseudo signals. It may be a configuration.

  In addition, the system for measuring a biological signal is not limited to the system that performs wireless communication as shown in the embodiments, and is adopted for various forms such as a system in which a pulse wave sensor to a signal processing device are connected by wire. be able to.

  In the above-described embodiment, the configuration in which the pseudo signal corresponding to the shift time is selected and used from the plurality of pseudo signals stored in the pseudo signal database 33 is exemplified. There may be. For example, the configuration may be replaced with one pseudo signal created in advance. In that case, it may be configured to be used by being deformed (expanded or contracted in the time axis direction) according to the shift time. Of course, even when a plurality of pseudo signals are used, the pseudo signals may be deformed according to the shift time.

  The pseudo signal may be created for each subject in advance, or a standard model may be created. Moreover, it may be configured to learn and create and update during pulse wave measurement. Moreover, it is good also as a structure which uses the measurement signal immediately before measured as a pseudo signal for replacement.

  In the above embodiment, the peak point is used as the feature point of the pulse waveform, and the configuration used for the measurement of the shift time and the replacement with the pseudo signal is excited. However, the feature point other than the peak point may be used. Good. For example, the bottom point of the pulse wave waveform or the peak point based on the speed or acceleration of the pulse wave signal may be used.

  In the above embodiment, the configuration for calculating the autocorrelation value between the target measurement signal and the immediately preceding measurement signal is illustrated, but the configuration is such that the past measurement signal and the autocorrelation value are calculated further immediately before the target measurement signal. May be. It should be noted that the presence or absence of noise can be determined with high accuracy by calculating a measurement signal and an autocorrelation value at a time as close as possible from the target measurement signal.

  Further, without using autocorrelation, another parameter indicating the degree of coincidence between the waveform of the target measurement signal and the past measurement signal is calculated, and the target measurement signal is measured within a predetermined range based on the value. It may be configured to determine whether or not. For example, using the absolute amount of error between the target measurement signal and the past measurement signal, the value obtained by dividing one output value by the other output value, and the like as parameters, the above determination is made based on whether or not a set threshold value is exceeded. You may comprise.

Moreover, in the said Example, although the structure which calculates deviation | shift time with the moving average with a forgetting factor 3 times was illustrated, the calculation method of other than that may be sufficient. For example, the arithmetic average of a plurality of peak time differences (t _n , t _n−1 , t _n−2 etc. in FIG. 3) is used as the shift time, or the peak time difference between the immediately preceding measurement signal and the immediately preceding measurement signal (in FIG. 3) it is conceivable that or a t value of _n) as it shifted time.

  Moreover, in the said Example, although the structure which replaces about the period from ted to ted0 of an object measurement signal and a pseudo signal was illustrated, it is good also as a structure which replaces in another period. For example, a configuration in which one cycle of the pulse wave is replaced with a pseudo signal may be used.

  Moreover, in the said Example, although the structure which takes out the signal for 1 period of pulse waves as a measurement signal, and performed the process of replacement was illustrated, it is the structure which processes at a time interval longer than 1 period, or a short time interval. There may be. For example, it is determined whether or not there is a missing portion of pulse wave signals for a period of two cycles or more than three cycles. If there is a missing portion, only the missing portion or a wide period including the missing portion is supported. You may comprise so that it may replace with a pseudo signal.

DESCRIPTION OF SYMBOLS 1 ... Biosignal processing system, 3 ... Biosensor, 5 ... Radio equipment, 7 ... Radio equipment, 9 ... Signal processing apparatus, 21 ... Memory | storage part, 23 ... Past biosignal acquisition part, 25 ... Deviation time determination part, 27 ... Autocorrelation calculation unit, 29 ... missing determination unit, 31 ... pseudo signal extraction unit, 33 ... pseudo signal database, 35 ... bio signal synthesis unit, 41 ... bio signal information processing unit, 51 ... pseudo signal

Claims (6)

A storage unit (21) for storing a biological signal having periodicity measured from a subject;
A determination unit (23, 25, 27, 29, S1 to S4) for determining whether or not the biological signal is measured within a predetermined range based on a past biological signal extracted from the storage unit;
A replacement unit (31, 35, S5 to S6) for replacing the biological signal with a pseudo signal when the determination unit determines that the biological signal is not measured within the predetermined range. A characteristic signal processing apparatus. A database (33) in which a plurality of pseudo signals corresponding to different periods of the biological signal are stored;
The signal processing apparatus according to claim 1, wherein the replacement unit replaces the biological signal with a pseudo signal corresponding to a cycle of the biological signal among the plurality of pseudo signals stored in the database. The replacement unit matches a time when a predetermined feature point in the waveform of the biological signal predicted based on a past biological signal extracted from the storage unit appears and a time of the feature point in the pseudo signal The signal processing apparatus according to claim 1, wherein the biological signal is replaced with the pseudo signal. The determination unit calculates an autocorrelation value between the biological signal and a biological signal obtained by delaying the past biological signal extracted from the storage unit by a time corresponding to a period of the biological signal, and the autocorrelation value Is greater than or equal to a predetermined threshold value, it is determined that the biological signal is measured within a predetermined range, and when the autocorrelation value is less than the predetermined threshold value, the biological signal is measured within the predetermined range. The signal processing device according to any one of claims 1 to 3, wherein the signal processing device is determined not to be present. The replacement unit replaces a portion of the period in which the biological signal is determined not to be measured within a predetermined range by the determination unit in the biological signal with a portion corresponding to the period in the pseudo signal. The signal processing device according to any one of claims 1 to 4. A first function (S1 to S4) for determining whether or not a biological signal having periodicity measured from a subject is measured within a predetermined range based on a biological signal in the past of the biological signal;
A second function (S5 to S6) for replacing the biological signal with a pseudo signal when it is determined by the first function that the biological signal is not measured within the predetermined range;
A program to make a computer realize.

Images