Biological signal measurement system

Abstract

This biological signal measurement system comprises: an on-board device (100) provided with a first measurement unit (101) that measures a biological signal of an operator (150); and a wearable device (120) provided with a second measurement unit (121) that measures a biological signal of the operator (150). The first measurement unit (101) comprises a steering electrode (102), a first reception circuit (103), a first amplification circuit (104), and a first transmission circuit (105). The second measurement unit (121) comprises a wearable electrode (122), a second reception circuit (123), a second amplification circuit (124), and a second transmission circuit (125).

Description

Biological signal measurement system

[0001] The present invention relates to a biological signal measurement system.

[0002] A method for monitoring an operator (driver) using biological signals has been proposed for the health and safety of automobile drivers (Non-Patent Document 1). In this technology, electrodes for measuring biological signals are provided at two locations on the steering wheel, which is a steering device, and biological signals are measured when the operator touches the electrodes with each hand.

[0003] B. Babusiak et al., "Design of Smart Steering Wheel for Unobtrusive Health and Drowsiness Monitoring", Sensors, vol. 21, no. 16, 5285, 2021.

[0004] However, in conventional biological signal measurement, it is necessary to hold the steering device (steering wheel) with both hands, but there are many operators who hold the steering device with only one hand, and depending on the actual driving situation of the operator, measurement may not be possible.

[0005] The present invention has been made to solve the above problems, and an object thereof is to enable biological signals to be measured regardless of the actual driving situation of the operator.

[0006] The biosignal measurement system according to the present invention comprises an onboard device equipped with a first measurement unit for measuring the biosignals of an operator, and a wearable device equipped with a second measurement unit for measuring the biosignals of an operator. The first measurement unit includes a steering electrode provided on the steering device of a transport vehicle operated by the operator to measure the biosignals of the operator, a first receiving circuit that receives the biosignals transmitted from the wearable device via human body communication, a first amplification circuit that differentially amplifies the measured biosignals and the biosignals transmitted from and received from the wearable device, and transmits the biosignals differentially amplified by the first amplification circuit to the wearable device via human body communication. The second measurement unit comprises a first transmission circuit and a wearable electrode for measuring biological signals from the operator, a second receiving circuit for receiving biological signals transmitted from the mounted device via human body communication, a second amplification circuit for differentially amplifying the measured biological signals and the biological signals transmitted from and received from the mounted device, and a second transmission circuit for transmitting the differentially amplified biological signals from the second amplification circuit to the mounted device via human body communication. The mounted device is mounted on a transport vehicle operated by the operator, the wearable device is worn by the operator, and at least one of the first amplification circuit and the second amplification circuit outputs the differentially amplified signal to the outside of the measurement unit.

[0007] As described above, according to the present invention, since an onboard device and a wearable device are used, each equipped with a measurement unit for measuring biological signals, biological signals can be measured regardless of the pilot's actual operation.

[0008] Figure 1 is a configuration diagram showing the configuration of a biosignal measurement system according to an embodiment of the present invention. Figure 2 is a configuration diagram showing a partial configuration of a biosignal measurement system according to an embodiment of the present invention. Figure 3A is a configuration diagram showing the configuration used for simulating the effect of a GND electrode. Figure 3B is a characteristic diagram showing the simulation results of the effect of a GND electrode. Figure 4 is a configuration diagram showing a partial configuration of another biosignal measurement system according to an embodiment of the present invention. Figure 5 is a configuration diagram showing a partial configuration of another biosignal measurement system according to an embodiment of the present invention. Figure 6 is a configuration diagram showing a partial configuration of another biosignal measurement system according to an embodiment of the present invention. Figure 7 is a configuration diagram showing a partial configuration of another biosignal measurement system according to an embodiment of the present invention. Figure 8 is a flowchart illustrating an example of operation of another biosignal measurement system according to an embodiment of the present invention.

[0009] Hereinafter, a biosignal measurement system according to an embodiment of the present invention will be described with reference to Figure 1. This biosignal measurement system comprises an onboard device 100 equipped with a first measurement unit 101 for measuring the biosignals of a pilot (driver) 150, and a wearable device 120 equipped with a second measurement unit 121 for measuring the biosignals of the pilot 150. The onboard device 100 can be composed of computer-related equipment. The wearable device 120 can take any form, such as a smartwatch, band, ankle band, adhesive type, or clothing.

[0010] The mounted device 100 is used in transportation equipment such as passenger cars, buses, trucks, bicycles, motorcycles, aircraft, and ships (small boats and yachts) that are operated (driven) by a pilot 150. In passenger cars, buses, trucks, etc., the steering device is, for example, a steering wheel. In bicycles, motorcycles, etc., the steering device is, for example, a handle. In aircraft, the steering device is, for example, a control stick. In ships, the steering device is, for example, a steering wheel.

[0011] The mounted device 100 is a computer device equipped with a CPU (Central Processing Unit), main memory, external memory, network connection device, etc., and the CPU operates (executes the program) based on the program deployed in the main memory, thereby realizing the functions described later. For example, it may include functions such as converting signals output from the first measurement unit 101 from analog to digital for processing, and communication functions for transmitting signals externally.

[0012] The wearable device 120 is used by being worn by the pilot 150. The wearable device 120 can take any form, such as a smartwatch, band, ankle band, adhesive type, or garment. Furthermore, the wearable device 120 may include functions such as analog-to-digital conversion of signals output from the second measurement unit 121, processing functions such as a CPU, and communication functions.

[0013] The first measurement unit 101 includes a steering electrode 102, a first receiving circuit 103, a first amplification circuit 104, and a first transmitting circuit 105. As shown in Figure 2, the steering electrode 102 is installed on the steering device 151 of a transport vehicle operated by a pilot 150 to measure the biosignals of the pilot 150. The first receiving circuit 103 receives the biosignals transmitted from the wearable device 120 via human body communication. The first amplification circuit 104 differentially amplifies the measured biosignals and the biosignals transmitted from and received by the wearable device 120. The first transmitting circuit 105 transmits the biosignals differentially amplified by the first amplification circuit 104 to the wearable device 120 via human body communication.

[0014] The second measurement unit 121 includes a wearable electrode 122, a second receiving circuit 123, a second amplification circuit 124, and a second transmitting circuit 125. The wearable electrode 122 measures biological signals from the operator 150. The second receiving circuit 123 receives biological signals transmitted from the onboard device 100 via human body communication. The second amplification circuit 124 differentially amplifies the measured biological signal and the biological signal transmitted from and received from the onboard device 100. The second transmitting circuit 125 transmits the biological signal differentially amplified by the second amplification circuit 124 to the onboard device 100 via human body communication. Although not shown, the wearable device 120 may be equipped with a power source such as a secondary battery to supply power to the second measurement unit 121 and other components.

[0015] At least one of the first amplification circuit 104 and the second amplification circuit 124 outputs the differentially amplified signal to the outside of the measurement unit. For example, the first amplification circuit 104 outputs the differentially amplified signal, which has been processed by the output unit 106, to the outside of the first measurement unit 101. The amplified signal thus output is converted from analog to digital, processed by a processing function such as a CPU, and transmitted to a server device via a communication function, where it is reproduced, for example, as an electrocardiogram waveform, and the state of the operator 150 is determined.

[0016] For example, it is possible to estimate the state of the pilot 150 from changes in electrocardiogram (ECG waveform). Specifically, there are frequency domain indicators for heart rate variability analysis, such as LF (Low Frequency), which is represented by a power spectrum in the 0.004 to 0.15 Hz band, and HF (Hi Frequency), which is represented by a power spectrum in the 0.15 to 0.4 Hz band, and time domain indicators such as pNN50 (percent of difference between adjacent normal RR intervals greater than 50 ms), which is the ratio of the difference between adjacent RR intervals that exceeds 50 ms.

[0017] According to this embodiment, the need to grip the steering device with both hands, which was previously required for measuring biosignals, is eliminated, and measurement becomes possible with just one hand gripping the steering device. Therefore, there are no restrictions on the pilot's piloting style, and it is expected that fatigue will be reduced through relaxed piloting. By measuring biosignals during piloting, it can be used to detect pilot fatigue, stress, concentration levels, drowsiness, and diseases such as epileptic seizures, greatly contributing to providing safe and healthy piloting.

[0018] The specific operation will be explained using the measurement of electrocardiogram (ECG) as an example of a biosignal. The operator wears a wearable device and touches the electrodes of the onboard device. This establishes a communication channel between the wearable device and the onboard device via the human body, which acts as a dielectric. Each device acquires a weak ECG component of 1 mV or less from its own biosignal detection electrode and performs differential amplification in an amplification circuit. An operational amplifier circuit configuration, similar to that used in instrumentation amplifiers, can be employed for differential amplification.

[0019] In the differential amplifier circuit, the inputs are the electrocardiogram measured by electrodes and the received signal demodulated from the transmitted signal from the other device. The signal output from the amplifier circuit is modulated and transmitted from the electrodes to the other device via the human body, thereby constructing a circuit system capable of mutual signal exchange. This fulfills the function of a differential amplifier circuit without direct wiring, including GND and signal lines, between the devices. The human body is a dielectric material and is particularly suitable for transmission up to about 100 MHz, so simultaneous bidirectional transmission is possible by performing frequency division multiplexing in the frequency range below 100 MHz.

[0020] As shown in Figure 2, the biosignal measurement system has a steering electrode 102 of an onboard device 100 mounted on the transport vehicle attached to the steering device 151 that the driver 150 touches. The driver 150 wears a wearable device 120, and by, for example, sitting in the cockpit 152 and assuming a driving posture, signals are transmitted and received and biosignals are measured via human body communication through the driver 150. In this example, the wearable device 120 is attached to the driver 150's leg (ankle), but it can be attached to other parts such as the limbs or back. If the transport vehicle is an automobile, attaching the wearable device 120 to the left foot, which does not move while driving, allows for measurement in a resting state and is suitable for measuring good biosignals.

[0021] Conventionally, the steering electrode 102 provided on the steering device 151 requires separate positive and negative electrodes at positions where the operator 150 can touch each of their hands. However, according to this embodiment, since one electrode is on the steering device 151 and the other electrode is on the wearable device 120, only one electrode needs to be provided on the steering device 151. Therefore, the steering electrode 102 can be provided in any area of ​​the steering device 151, without being affected by individual differences such as the operator's habits or physique, and productivity can be improved without the need for adjustments for each operator.

[0022] The steering electrode 102 and the wearable electrode 122 can be made from any conductive material, whether metallic or nonmetallic. For example, the steering electrode 102 and the wearable electrode 122 can be made from cloth electrodes or carbon electrodes with low thermal conductivity. In this case, excessive temperature rise in hot conditions can be avoided, reducing discomfort when touched and the risk of burns.

[0023] The steering electrode 102 can be pre-installed during the manufacturing of the steering device 151, or it can be added to an existing steering device 151. For example, by using a flexible electrode as a cover for the steering device 151, the steering electrode 102 can be installed by placing it over the grip of the steering device 151.

[0024] According to this embodiment, when a pilot 150 wearing the wearable device 120 touches the steering electrode 102 of the mounted device 100, a biosignal can be measured. By measuring the biosignal, it is possible to determine whether the pilot 150 is gripping the steering device 151. For example, in autonomous driving, even when the pilot 150 does not need to take control, it is required that they firmly grip the steering device 151 to avoid sudden accidents and ensure safety. For such use cases, according to this embodiment, it is possible to determine whether the pilot 150 is gripping the steering device 151 based on whether or not a biosignal can be measured.

[0025] For example, by providing a determination function (determination circuit) that determines whether or not a biological signal can be measured based on the presence or absence of a differentially amplified amplified signal output externally by at least one of the first amplification circuit 104 and the second amplification circuit 124, it is possible to determine whether the operator 150 is gripping the steering device 151. Whether or not a biological signal can be measured can be determined based on the presence or absence of an amplified signal output from the first amplification circuit 104 via the output unit 106. In this case, the determination function can be provided by the mounted device 100. Furthermore, whether or not a biological signal can be measured can be determined based on the presence or absence of an amplified signal output from the second amplification circuit 124. In this case, the determination function can be provided by the wearable device 120. In addition, the determination function can be provided by an external device (server device) connected to the output unit 106.

[0026] According to this embodiment, first, the pilot wears a wearable device, and in this state, the pilot touches the steering electrode of the onboard device, and signals are transmitted and received between the wearable device and the pilot via the pilot's body. Therefore, according to this embodiment, it also serves as a barrier to prevent the use of signal generators that output signals mimicking biosignals or to deceptive acts by others in relation to the judgment function described above.

[0027] By providing a GND electrode having the same GND potential as the onboard device 100 near the cockpit, the GND capacitive coupling between the onboard device 100 and the wearable device 120 can be improved, thereby enhancing the measurement performance of biological signals.

[0028] Specifically, if the GND is unstable, the GND potential will fluctuate due to the bioelectric potential, causing the potential difference between the input voltage to the electrodes used for acquiring bioelectric signals and the GND potential to decrease. However, by strengthening the coupling between GNDs, fluctuations in the GND potential can be suppressed, making it possible to reduce the attenuation of the bioelectric potential input.

[0029] This effect is particularly favorable because the coupling between the mounted device 100 and the wearable device 120, to which an inverse phase potential is input, strengthens, causing the fluctuations of the GND potential to pull in opposite directions and cancel each other out. This effect also works by establishing a capacitive coupling between either the mounted device 100 or the wearable device 120 and a human body surface away from the electrode contact surface of either device, as this improves the stability of the GND potential.

[0030] The simulation results of the effect of the GND electrode described above will be explained with reference to Figures 3A and 3B. Figure 3A shows the configuration used in the simulation. The mounted device and the wearable device each have different GNDs, and a variable capacitance was set assuming that capacitive coupling exists between them. The graph shown in Figure 3B represents the gain of the difference between OUT1 and OUT2 at each capacitance value. It can be seen that the gain improves as the capacitance between GNDs increases. Since the design gain of the circuit is not changed, the input attenuation of biopotential is suppressed, and the performance of biopotential measurement is improved.

[0031] For example, as shown in Figure 4, the mounted device 100 can be further configured to include a GND electrode 107. Note that the wearable device 120 is omitted in Figure 4. By positioning the GND electrode 107 at a different location from the steering electrode 102, the capacitive coupling between the pilot 150 and at least one of the wearable terminals can be strengthened. Since the GND electrode 107 does not need to directly touch the pilot 150, it can be configured to be covered by a housing or the like without exposing conductive parts such as metal on its surface. Also, since the GND electrode 107 is not worn, even if it is positioned away from the mounted device 100 by physical wiring, it does not impair the convenience of the pilot 150.

[0032] For example, as shown in Figure 5, a GND electrode 107 can be placed. The GND electrode 107, which is electrically connected to the mounted device 100, can be installed on the floor of the cockpit 152 or the transport equipment at the feet of the pilot 150. The GND electrode 107 forms a capacitive coupling with at least one of the pilot 150 or the wearable device 120, and a capacitance value greater than that obtained when there is no GND electrode 107 can be obtained. By providing the GND electrode 107 in this way, the capacitance value, which was conventionally around 1 to 10 pF, can be increased by more than 10 times, resulting in the exceptional performance improvement shown in Figure 3B. Note that the above-described placement of the GND electrode 107 is just one example, and it is effective to place the GND electrode in any location that the pilot 150 may come into contact with during operation, such as the armrest, the edge of the cockpit door, the shift lever, or the footrest, and any combination of these locations can be used.

[0033] Furthermore, connecting the GND electrode to the body of the transport equipment is also considered effective in improving capacitive coupling. The body of the transport equipment is generally made of metal and is sufficiently large relative to each device, so the potential is stable. By connecting the GND of the mounted device 100 to the body of the transport equipment, the GND potential is stabilized, preventing fluctuations due to bioelectric potential. In addition, since the body covers the operator 150, it forms a capacitive coupling with the operator 150 and the wearable device 120, which is suitable for improving performance.

[0034] Furthermore, the GND electrode is preferable to be provided on part or all of the bucket seat, which is shaped to enclose the operator 150, as this allows for the formation of a larger area of ​​capacitive coupling. In particular, conductive carbon fiber materials and aluminum components are used in general bucket seats, and are suitable as a way to effectively utilize existing production lines without compromising productivity.

[0035] For example, it is preferable to attach a wearable device to the left foot and place the GND electrode on the floor or under the cockpit. In the case of an automobile, for instance, the driver usually rests their left foot on the floor, including the footrest. Therefore, measurements can be taken in a state close to rest, suppressing noise generation due to body movement, and noise caused by vibrations of the transport equipment is applied to multiple devices as a common-mode component, thus being effectively removed by differential amplification.

[0036] Another example of a wearable device is the use of a smartwatch. Currently, pilots (150) do not have much of a habit of wearing wearable devices on their feet, and wearable devices are most often worn on either the left or right wrist.

[0037] Figure 6 shows an example where the wearable device 120 is composed of a smartwatch. The pilot 150 wears the wearable device 120 on their right hand and holds the steering device 151 with their left hand, touching the steering electrode 102. As a result, biosignals are detected by the pilot 150's left and right hands, and biosignal measurement is realized through differential amplification in an amplification circuit using mutual transmission and reception via human body communication. In this example, the right hand is placed on the armrest 153, and by providing a GND electrode 107 on the armrest 153, good biosignal measurement can be achieved.

[0038] Furthermore, the configuration is not limited to the example described above. The wearable device 120 can be worn on the left hand, the left hand can be placed on the armrest or shift lever, and the steering device 151 can be gripped with the right hand to touch the steering electrode 102. This can be achieved by also providing a GND electrode on the left hand side.

[0039] Furthermore, if the wearable device is worn on the same hand as the steering electrode, measuring biosignals becomes difficult. For example, if the wearable device is worn on the left wrist and the steering electrode is touched with the left hand, the biosignal measurement will effectively be performed at the same location, resulting in a very small potential difference. Similarly, if the steering mechanism is gripped with both hands, the potential difference is also expected to be small. To address these issues, the following method enables the measurement of biosignals regardless of which hand the pilot, wearing a wearable device on either hand, uses to grip the steering mechanism.

[0040] The measurement method described above will be explained with reference to Figure 7. Two first steering electrodes 102a and a second steering electrode 102b are provided on the steering device 151 so that they can be touched by the right and left hands. For example, the first steering electrode 102a can be provided on the left half of the steering device 151 and the second steering electrode 102b on the right half. Furthermore, it can be divided into even smaller sections. For example, the steering device 151 can be divided into four sections such that the diagonal sides are the same electrodes.

[0041] The first steering electrode 102a is connected to a first switch 108a, which can control the conduction and disconnection states, and the second steering electrode 102b is connected to a second switch 108b, which can also control the conduction and disconnection states. These are connected to the mounted device 100. The mounted device 100 transmits control signals to each switch, and by switching between conduction and disconnection, it ensures an appropriate potential difference and achieves the measurement of biological signals.

[0042] For example, both switches can be in a conductive state in the initial state. The received signal strength is monitored by, for example, a first receiving circuit (not shown) of the mounted device 100, and if it is above a threshold, it can be determined that a wearable device is attached to the wrist (Figure 8: step S101). In this case, if one of the steering electrodes is cut (Figure 8: step S102) and the level of the received signal strength decreases (yes in Figure 8: step S103), it can be determined that a wearable device is attached to the hand touching the side of the cut steering electrode. Therefore, by leaving that steering electrode cut, it becomes possible to measure biosignals. If the level of the received signal strength does not decrease (no in Figure 8: step S103), the hand on the side with the wearable device attached is touching the steering electrode, so by switching the steering electrode to be cut (Figure 8: step S104), it becomes possible to measure biosignals in the same way.

[0043] In addition, part or all of the GND electrode can also be used as a drive electrode. The drive electrode cancels out an excessive in-phase signal from the circuit by feeding back the in-phase component of the measurement signal to the human body, making it easier to measure only the anti-phase component including the cardiac potential component (biological signal). Specifically, in the first amplification circuit or the second amplification circuit, the in-phase component is extracted by taking the average value of the biological signal acquired by itself and the biological signal sent from the other device. The obtained in-phase component is inverted and applied from the drive electrode to the human body to perform in-phase cancellation.

[0044] As described above, according to the embodiment of the present invention, since the mounted device and the wearable device each having a measurement unit for measuring a biological signal are used, the biological signal can be measured regardless of the actual operation state of the operator.

[0045] It should be noted that the present invention is not limited to the embodiments described above, and it is obvious that many modifications and combinations can be implemented by those with ordinary knowledge in the art within the technical idea of the present invention.

[0046] 100... Mounted device, 101... First measurement unit, 102... Steering electrode, 103... First receiving circuit, 104... First amplification circuit, 105... First transmitting circuit, 106... Output unit, 120... Wearable device, 121... Second measurement unit, 122... Wearable electrode, 123... Second receiving circuit, 124... Second amplification circuit, 125... Second transmitting circuit, 150... Operator (driver).

Claims

1. The device comprises an onboard device equipped with a first measurement unit for measuring the operator's biosignals and a wearable device equipped with a second measurement unit for measuring the operator's biosignals, wherein the first measurement unit comprises a steering electrode provided on the steering device of a transport vehicle operated by the operator for measuring the operator's biosignals, a first receiving circuit for receiving biosignals transmitted from the wearable device via human body communication, a first amplification circuit for differentially amplifying the measured biosignals and the biosignals transmitted from and received from the wearable device, and a first transmitting circuit for transmitting the differentially amplified biosignals from the first amplification circuit to the wearable device via human body communication, wherein the second measurement unit comprises a wearable electrode for measuring the operator's biosignals, a second receiving circuit for receiving biosignals transmitted from the onboard device via human body communication, a second amplification circuit for differentially amplifying the measured biosignals and the biosignals transmitted from and received from the onboard device, and a second transmitting circuit for transmitting the differentially amplified biosignals from the second amplification circuit to the onboard device via human body communication. The mounted device is mounted on a transport vehicle operated by the operator, the wearable device is worn by the operator, and at least one of the first amplification circuit and the second amplification circuit outputs a differentially amplified amplified signal to the outside of the measurement unit, in a biosignal measurement system.

2. A biosignal measurement system according to claim 1, wherein the mounted device further comprises a GND electrode capacitively coupled to the operator.

3. A biosignal measurement system according to claim 2, wherein the GND electrode is provided on the floor surface of the transport equipment at the feet of the operator.

4. A biosignal measurement system according to claim 1, further comprising a determination circuit that determines whether or not a biosignal can be measured based on the presence or absence of a differentially amplified amplified signal output to the outside by at least one of the first amplification circuit and the second amplification circuit.

5. A biosignal measurement system according to claim 1, comprising a switch that controls the connection between the mounted device and the steering electrode based on the signal strength of human body communication.

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