Biological information generation device

Abstract

This method detects noise sections where body movement noise occurs, while avoiding a significant increase in the cost and size of the biometric information generation device. [Solution] In a flexible printed circuit board (FPC) on which biosensors SA and SB that come into contact with human skin are mounted, linear conductive patterns PA, PB, and PC made of conductive paste are formed near the biosensors SA and SB. A bioinformation generation unit 13B generates bioinformation based on sensor signals output from the biosensors SA and SB, and a noise section determination unit 13A determines a noise section in which body motion noise occurs by comparing the resistance values ​​of the conductive patterns PA, PB, and PC with a preset threshold value.

Description

Technical Field

[0001] The present invention relates to a biological information generation technology for generating biological information based on a sensor signal output from a biological sensor.

Background Art

[0002] When generating biological information such as a person's heart rate, body temperature, and posture based on a sensor signal output from a biological sensor, body movement noise generated by the person's movement may be superimposed on the sensor signal, resulting in a decrease in the accuracy of the biological information. For example, in a piezoelectric sensor or a photoelectric plethysmogram sensor used in a state of being in contact with the skin, a change in the skin contact state caused by deformation of the skin accompanying movement of the finger or wrist (movement of the bone) is the main factor, and body movement noise is generated.

[0003] Conventionally, as a technique for determining a noise section affected by such body movement noise, Patent Document 1 proposes a configuration in which a circuit unit for detecting the spatial displacement of a biological sensor is provided in a biological information generation device, and a period in which the detected spatial displacement is large is determined as a noise section in which body movement noise is generated. Thereby, the biological information detected during the period determined as the noise section can be excluded, and the accuracy of the biological information can be improved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, according to the technology described in Patent Document 1, in order to determine the noise section in which body motion noise occurs, it is necessary to add a gyro sensor or image sensor to the biosensor as a circuit section for detecting the spatial displacement of the biosensor. These gyro sensors and image sensors are more expensive, occupy more space, and are heavier than biosensors. As a result, the circuit size of the biosensor increases significantly, leading to problems such as an increase in the overall cost, size, and weight of the biosensor. In particular, wearable devices such as biosensors require wearability on the human body, and an increase in size and weight worsens wearability.

[0006] The present invention aims to solve these problems and provide a bio-information generation technology that can detect noise sections where body movement noise occurs while avoiding a significant increase in the cost and size of the bio-information generation device. [Means for solving the problem]

[0007] To achieve this objective, the bioinformation generation device according to the present invention comprises a flexible substrate on which a biosensor that comes into contact with human skin is mounted, and a control circuit configured to drive the biosensor, wherein the flexible substrate has a linear conductive pattern made of conductive paste formed near the biosensor, and the control circuit comprises a bioinformation generation unit configured to generate bioinformation based on a sensor signal output from the biosensor, and a noise interval determination unit configured to determine a noise interval in which body motion noise occurs by comparing the resistance value of the conductive pattern with a preset threshold.

[0008] Furthermore, one example of the configuration of the biological information generation device according to the present invention includes two wiring patterns formed along mutually orthogonal directions in the conductive pattern.

[0009] Furthermore, in one example configuration of the biological information generation device according to the present invention, the conductive pattern is formed to surround the biological sensor.

[0010] Furthermore, in one example of the configuration of the biological information generation device according to the present invention, the control circuit includes a threshold adjustment unit configured to adjust the threshold value based on the resistance value deviation between the average resistance value of the conductive pattern and a preset reference resistance value. [Effects of the Invention]

[0011] According to the present invention, it is possible to detect noise sections in which body motion noise occurs while avoiding a significant increase in the cost and size of the biological information generation device. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a block diagram showing the configuration of a biological information generation device according to this embodiment. [Figure 2] Figure 2 is a signal waveform diagram showing the changes in the sensor signal output from the biosensor. [Figure 3] Figure 3 is a signal waveform diagram showing the change in current flowing through the conductive pattern. [Figure 4] Figure 4 is a signal waveform diagram showing the change in the resistance value of the conductive pattern. [Figure 5] Figure 5 is a flowchart showing the noise interval determination process. [Figure 6] Figure 6 is a flowchart showing the process for generating biological information. [Modes for carrying out the invention]

[0013] Next, embodiments of the present invention will be described with reference to the drawings. [This embodiment] First, the biological information generation device 10 according to this embodiment will be described with reference to the block diagram in Figure 1. This bio-information generation device 10, as a whole, consists of a wearable device that is attached to a person's body, such as the arm or chest, and is configured to generate bio-information such as heart rate, body temperature, and posture using biosensors such as piezoelectric sensors and photoelectric pulse wave sensors that are used in contact with the skin.

[0014] [Principle of the present invention] When generating biometric information based on sensor signals output from biosensors, motion noise caused by human movement can superimpose on the sensor signal, potentially reducing the accuracy of the biometric information. As shown in the signal waveform diagram in Figure 2, in the noise section Tn where motion noise occurs, the amplitude of the sensor signal (pulse wave signal) S changes compared to other sections where motion noise does not occur. This affects the value of the biometric information obtained from the sensor signal S. In the case of biosensors such as piezoelectric sensors and photoelectric pulse wave sensors used in contact with the skin, this motion noise is mainly caused by changes in the skin contact state resulting from skin deformation associated with finger and wrist movements (bone movements).

[0015] On the other hand, the biosensor used in the bioinformation generation device 10 is mounted on a flexible substrate and attached to the body so as to come into contact with the skin. In this case, the flexible substrate also bends due to the deformation of the skin. Therefore, by detecting the bending of the flexible substrate, it is possible to determine the noise interval Tn in which skin deformation, i.e., body motion noise, occurs. Flexible substrates, such as film or sheet types, are widely used as circuit boards for mounting biosensors, taking into consideration contact with deformable skin. Conductive paste is a relatively inexpensive adhesive that possesses conductivity and can perform conductive bonding at lower temperatures than solder, allowing conductive patterns to be formed in any shape even on flexible substrates with low heat resistance.

[0016] Here, the conductive paste has a resistance value and has the characteristic that its resistance value changes according to the bending of the flexible substrate. The present invention focuses on the relationship between the deformation of such a flexible substrate and the change in the resistance value of the conductive paste, forms a conductive pattern made of the conductive paste on the flexible substrate, detects the resistance value of the conductive pattern, and compares it with a threshold value indicating the resistance value in a state where no bending has occurred, thereby determining the noise section Tn in which body movement noise due to the bending of the flexible substrate, that is, the deformation of the skin, occurs. Thereby, unlike the case of using relatively expensive circuit elements such as gyro sensors and image sensors, it is possible to detect the noise section Tn in which body movement noise occurs while avoiding a significant increase in the cost and size of the product.

[0017] [Biological information generation device] Next, referring to the block diagram of FIG. 1 described above, the configuration of the biological information generation device 10 according to the present embodiment will be described in detail. The biological information generation device 10 is composed of a circuit portion formed on a flexible substrate FPC as a whole. As main circuit portions, it includes biological sensors SA and SB, conductive patterns PA, PB, and PC, a communication I / F 11, a memory circuit 12, and a control circuit 13. Note that only the biological sensors SA and SB and the conductive patterns PA, PB, and PC may be mounted on the flexible substrate FPC, and the communication I / F 11, the memory circuit 12, and the control circuit 13 may be mounted on a rigid substrate or a flexible substrate separate from the flexible substrate FPC.

[0018] [Biological sensor] The biological sensors SA and SB are composed of biological sensors such as piezoelectric sensors and photoelectric pulse wave sensors used in a state of being in contact with the skin, and are configured to output sensor signals such as pulse wave signals obtained through the skin, driven by the control circuit 13. In the block diagram of FIG. 1, a configuration including two biological sensors is shown as an example, but the present invention is not limited thereto. The present invention can be similarly applied even when there is one biological sensor or three or more biological sensors.

[0019] [Conductivity Pattern] The conductive patterns PA, PB, and PC are linear wiring patterns made of conductive paste formed on a flexible printed circuit board (FPC) near the biosensors SA and SB. In the block diagram of Figure 1, conductive patterns PA and PB are formed along direction X on the plane of the flexible printed circuit board (FPC) near the biosensors SA and SB, respectively. Conductive pattern PC is also formed along direction Y, which is perpendicular to direction X on the plane of the flexible printed circuit board (FPC), near the biosensors SA and SB. The ends of conductive pattern PC are electrically connected to the ends of conductive patterns PA and PB, and the conductive patterns PA, PC, and PB are connected in series in that order. The conductive paste is a general adhesive in which conductive particles, such as metal particles (fillers) such as silver, are dispersed in an organic binder resin such as epoxy resin. Conductive patterns PA, PB, and PC can be formed by applying this paste to the flexible printed circuit board (FPC).

[0020] The block diagram in Figure 1 shows an example including three conductive patterns PA, PB, and PC, but the present invention is not limited to this, and may include two wiring patterns formed in mutually orthogonal directions. The present invention can be applied similarly to cases with one, two, or four or more conductive patterns. Since the flexible printed circuit board (FPC) is mounted so that the biosensors SA and SB come into contact with the skin, the curvature direction of the FPC is generally perpendicular to the plane of the FPC. In this case, if there is only one conductive pattern, and the direction of the saddle created by the curvature coincides with the stretching direction of the conductive pattern, the conductive pattern will not be curved, and therefore the curvature of the FPC may not be detected.

[0021] As shown in the block diagram in Figure 1, by forming multiple conductive patterns PA, PB, and PC along directions orthogonal to each other, the curvature of the flexible printed circuit board (FPC) can be detected using any of the conductive patterns PA, PB, or PC. Furthermore, as shown in the block diagram of Figure 1, by forming the conductive patterns PA, PB, and PC to surround the biosensors SA and SB, the bending of the flexible printed circuit board (FPC) can be reliably detected regardless of the direction of the FPC's curvature. In this case, the biosensors SA and SB may be surrounded by multiple linear conductive patterns, or by a circular conductive pattern. In addition, to suppress the intrusion of external noise into the conductive patterns PA, PB, and PC, the lengths of the conductive patterns PA, PB, and PC may be made as short as possible.

[0022] [Communication Interface] The communication interface 11 is configured to transfer biometric information 12A stored in the memory circuit 12 to a higher-level device (not shown), such as a PC or smartphone, via wireless communication such as Bluetooth or Wi-Fi, and to output a message from the higher-level device to the control circuit 13.

[0023] [Memory circuit] The memory circuit 12 consists of a storage device such as a semiconductor memory and is configured to store biological information 12A and program 12P used in the biological information generation process executed by the CPU of the control circuit 13. Biological information 12A is biological information such as heart rate, body temperature, and posture, generated based on sensor signals output from biological sensors SA and SB, and is generated by the control circuit 13 and stored in the memory circuit 12. Program 12P is configured to work in cooperation with the CPU of the control circuit 13 to realize various processing units for executing biological information generation processing. Program 12P is read from an external device or recording medium (neither shown) connected to the biological information generation device 10 and stored in the memory circuit 12 in advance.

[0024] [control circuit] The control circuit 13 has a CPU and its peripheral circuits, and is configured to realize various processing units for executing biological information generation processing by reading the program from the memory circuit 12 and cooperating with the CPU. The main processing units realized by the control circuit 13 are a noise section determination unit 13A, a biological information generation unit 13B, a biological information transmission unit 13C, and a threshold adjustment unit 13D.

[0025] [Noise section determination unit] The noise section determination unit 13A is configured to determine whether or not it is a noise section Tn by applying a predetermined voltage to the conductive patterns PA, PB, and PC in accordance with periodically occurring determination timings, measuring the current flowing through the conductive patterns PA, PB, and PC at that time, and performing calculations on these applied voltages and measured currents to obtain the resistance values ​​R of the conductive patterns PA, PB, and PC, and comparing the obtained resistance values ​​R with a threshold Rth set in advance in the memory circuit 12. Note that the resistance values ​​R of the conductive patterns PA, PB, and PC may also be obtained, for example, by applying a predetermined constant current to the conductive patterns PA, PB, and PC, measuring the voltage generated across the conductive patterns PA, PB, and PC, and performing calculations on these constant currents and measured voltages.

[0026] When a constant voltage is applied to conductive patterns PA, PB, and PC, and the current flowing through them is measured, the current increases during the period when the flexible printed circuit board (FPC) is bent, i.e., during the noise interval Tn, as shown in the signal waveform diagram of Figure 3. Therefore, when the resistance R of the conductive patterns PA, PB, and PC is calculated from the applied voltage and the measured current values, the resistance R decreases during the noise interval Tn, as shown in the signal waveform diagram of Figure 4. For this reason, a threshold Rth, which represents the resistance value when no bending occurs, can be set in advance, and the period during which the newly obtained resistance R falls below the threshold Rth can be determined as the noise interval Tn.

[0027] [Biological Information Generation Unit] The biological information generation unit 13B is configured to generate biological information corresponding to the sensor signals by detecting the sensor signals output from the biological sensors SA and SB in accordance with periodically occurring generation timings, and by deriving their characteristic quantities from the obtained detection data. Furthermore, the biological information generation unit 13B checks the determination result of the noise interval determination unit 13A and stores the obtained biological information in the storage circuit 12 only if the determination result indicates that it is outside the noise interval. If the determination result indicates that it is inside the noise interval, the obtained biological information is not stored in the storage circuit 12.

[0028] [Biometric Information Transmission Unit] The biometric information transmission unit 13C is configured to transmit biometric information 12A stored in the memory circuit 12 to the host device via the communication I / F 11 in accordance with periodically occurring transmission timings or in response to biometric information transmission request messages from the host device. This allows biological information containing errors obtained within the noise section to be discarded and avoided from transmission to higher-level devices, thereby improving the accuracy of the biological information.

[0029] In this embodiment, the case in which biological information obtained outside the noise section is discarded without being saved is described as an example, but the embodiment is not limited to this. For example, the biological information generation unit 13B may store all obtained biological information in the memory circuit 12 regardless of whether it is in a noise section or not, and also attach flag information indicating whether or not the biological information was obtained within the noise section to the biological information and store it, and the biological information transmission unit 13C may transmit all biological information 12A stored in the memory circuit 12 to the host device via the communication I / F 11. This allows the host device to select or discard biological information based on the flag information attached to the biological information, thereby increasing the flexibility of applications that use biological information.

[0030] [Threshold adjustment unit] The threshold adjustment unit 13D is configured to calculate the resistance values ​​R of the conductive patterns PA, PB, and PC multiple times in response to periodically occurring adjustment timings or threshold adjustment request messages from a higher-level device, calculate the average resistance value Ravg over a predetermined period, calculate a new threshold value Rth based on the resistance value deviation ΔR with respect to a reference resistance value Rs that is pre-set in the memory circuit 12, and reset it in the memory circuit 12.

[0031] The conductive patterns PA, PB, and PC exhibit a change in resistance R in response to deformation caused by external forces such as bending, but also possess a temperature characteristic where the resistance R changes with ambient temperature. This temperature characteristic largely depends on the temperature characteristics of the conductive paste. Therefore, based on the relationship between the resistance deviation ΔR and the threshold Rth at each ambient temperature, which has been empirically determined in advance from the actual bio-information generation device 10, a new threshold Rth can be calculated from the resistance deviation ΔR obtained at the adjustment timing.

[0032] Furthermore, in addition to conductive patterns PA, PB, and PC, biosensors SA and SB, which use piezoelectric sensors, for example, have temperature characteristics in which the magnitude of the sensor signal changes depending on the ambient temperature. For this reason, in addition to the relationship between the resistance deviation ΔR and the threshold Rth at each ambient temperature, the temperature characteristics of biosensors SA and SB at each ambient temperature may also be considered, and a new threshold Rth may be calculated from the resistance deviation ΔR obtained at the adjustment timing.

[0033] In the above explanation, the generation timing can be predetermined based on the sampling period of the biological information required by the application that uses the biological information. The judgment timing should be the same sampling period as the generation timing and should be positioned immediately before the generation timing so that the latest judgment result is obtained when the biological information is generated. The transmission timing is the period for transmitting the biological information to the host device in bulk and can be predetermined based on the update period of the biological information required by the application that uses the biological information and the number of biological information entries that can be stored in the memory circuit 12. The adjustment timing can be predetermined based on the range of change in ambient temperature that affects the biological information and the time required for that change. Furthermore, these timings can be generated by timing the control circuit 13. In addition, if the control circuit 13 can time an absolute date and time, a timestamp indicating the date and time of generation of the biological information may be attached to the biological information and stored in the memory circuit 12.

[0034] [Operation of this embodiment] Next, the operation of the biological information generation device 10 according to this embodiment will be described. [Noise interval detection process] First, the noise interval determination process in the noise interval determination unit 13A will be explained with reference to the flowchart in Figure 5. The noise interval determination unit 13A executes the noise interval determination process shown in Figure 5 when the determination timing arrives.

[0035] The noise section determination unit 13A first applies a predetermined voltage to the conductive patterns PA, PB, and PC, measures the current flowing through the conductive patterns PA, PB, and PC at that time, and calculates the resistance value R of the conductive patterns PA, PB, and PC by performing calculations on the obtained current measurement value and the applied voltage (step 100). Next, the noise interval determination unit 13A compares the obtained resistance value R with a threshold value Rth that has been set in advance in the memory circuit 12 (step 101).

[0036] If the resistance value R is greater than or equal to the threshold Rth (step 101: NO), the noise interval determination unit 13A determines that it is outside the noise interval (step 103) and terminates the series of noise interval determination processes. On the other hand, if the resistance value R is less than the threshold Rth (step 101: YES), the noise interval determination unit 13A determines that it is inside the noise interval (step 102) and terminates the series of noise interval determination processes.

[0037] [Biometric information generation processing] Next, the bio-information generation process in the bio-information generation unit 13B will be explained with reference to the flowchart in Figure 6. The bio-information generation unit 13B executes the bio-information generation process shown in Figure 6 in response to the arrival of the generation timing.

[0038] The biological information generation unit 13B first detects the sensor signals output from the biological sensors SA and SB (step 110), and then generates biological information by deriving its feature quantities through computational processing of the obtained detection data (step 111). For the computational processing used to derive the feature quantities, known computational processing can be adopted depending on the sensor signals and biological information.

[0039] Next, the biological information generation unit 13B checks the determination result of the noise interval determination unit 13A (step 112). If the determination result indicates that the area is outside the noise interval (step 112: YES), the biological information generation unit 13B stores the obtained biological information in the memory circuit 12 (step 113) and terminates the series of biological information generation processes. On the other hand, if the determination result indicates that the area is within the noise interval (step 112: NO), the biological information generation unit 13B does not store the obtained biological information in the memory circuit 12 and terminates the series of biological information generation processes.

[0040] [Effects of this embodiment] As described above, the biological information generation device 10 according to this embodiment is configured such that linear conductive patterns PA, PB, and PC made of conductive paste are formed near the biological sensors SA and SB on a flexible substrate FPC on which biological sensors SA and SB that come into contact with human skin are mounted, the biological information generation unit 13B generates biological information based on the sensor signals output from the biological sensors SA and SB, and the noise section determination unit 13A determines the noise section in which body motion noise occurs by comparing the resistance values ​​of the conductive patterns PA, PB, and PC with a preset threshold value.

[0041] As a result, if conductive patterns PA, PB, and PC are formed on a flexible printed circuit board (FPC) as part of the hardware configuration, it is possible to determine the noise section in which body motion noise occurs. Moreover, the conductive patterns can be formed simply by applying a general conductive paste to the flexible printed circuit board (FPC), and are extremely inexpensive and occupy a small area compared to gyro sensors and image sensors. Therefore, it is possible to detect the noise section in which body motion noise occurs while avoiding a significant increase in the cost and size of the bio-information generation device 10. Furthermore, wearable devices such as the bio-information generation device 10 are required to be wearable on the human body, and according to the present invention, even if a configuration is added to determine the noise section in which body motion noise occurs, it is possible to maintain wearability by avoiding an increase in size and weight.

[0042] [Expansion of the embodiment] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above embodiments. Various modifications to the configuration and details of the present invention can be made that will be understood by those skilled in the art within the scope of the present invention. [Explanation of Symbols]

[0043] 10...Biological information generation device, 11...Communication I / F, 12...Memory circuit, 12A...Biological information, 12P...Program, 13...Control circuit, 13A...Noise section determination unit, 13B...Biological information generation unit, 13C...Biological information transmission unit, 13D...Threshold adjustment unit, SA, SB...Biosensor, PA, PB, PC...Conductive pattern, FPC...Flexible substrate, R...Resistance value, Rth...Threshold, Tn...Noise section.

Claims

1. A flexible circuit board equipped with a biosensor that comes into contact with human skin, The system comprises a control circuit configured to drive the aforementioned biosensor, The flexible substrate has a linear conductive pattern made of conductive paste formed near the biosensor. The aforementioned control circuit is A biological information generation unit configured to generate biological information based on the sensor signal output from the biological sensor, The system includes a noise interval determination unit configured to determine a noise interval in which motion noise occurs by comparing the resistance value of the conductive pattern with a preset threshold value. A biological information generation device characterized by the following features.

2. In the biological information generation device according to claim 1, The bio-information generation device is characterized in that the conductive pattern includes two wiring patterns formed along mutually orthogonal directions.

3. In the biological information generation device according to claim 1, A biological information generation device characterized in that the conductive pattern is formed to surround the biosensor.

4. In the biological information generation device according to claim 1, The biological information generation device is characterized in that the control circuit comprises a threshold adjustment unit configured to adjust the threshold value based on the resistance value deviation between the average resistance value of the conductive pattern and a preset reference resistance value.

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