Sensor system

Abstract

A sensor system A1 is provided with: a first sensor 11 for converting a first physical quantity of a measurement subject to a first signal V1 and outputting same; a second sensor 12 for converting a second physical quantity of the measurement subject to a second signal V2 and outputting same; and a control unit 2. The second physical quantity is correlated with whether the measurement subject is in a state suitable for sensing by the first sensor 11. The control unit 2 performs: first determination processing to determine on the basis of the second signal V2 whether the measurement subject is in a state suitable for sensing by the first sensor 11; measurement processing for, using the first signal V1, measuring first information about the measurement subject if the state was determined to be suitable by the first determination processing; second determination processing for determining, on the basis of the first signal V1, whether the measurement subject is in a state suitable for sensing by the first sensor 11; and correction processing for correcting a determination criterion of the first determination processing, by using the determination result from the second determination processing and the second signal V2 of when that determination was made. This configuration makes it possible to improve the accuracy of measurement combining two types of sensors.

Description

Sensor System

[0001] The present invention relates to a sensor system.

[0002] For example, a system combining multiple sensors has been proposed to measure vital signs, which indicate human life signs. Patent Document 1 discloses an example of a conventional sensor system. The sensor system disclosed in this document includes a fabric sensor and a signal processing device. The fabric sensor has two types of sensor elements. One sensor element is a piezoelectric sensor, and the other sensor element is a capacitance sensor. The fabric sensor is placed on, for example, a chair, a bed, etc. The capacitance sensor signal can detect whether a subject is sitting in a chair or lying on a bed. Then, by processing the piezoelectric sensor signal at that time, the subject's vital signs, such as pulse rate and respiration, can be measured.

[0003] Japanese Patent Application Laid-Open No. 2022-129318

[0004] Capacitive sensors can be affected by various factors other than the presence of a subject. If the signal from a capacitive sensor rises or falls unintentionally due to factors other than the presence of a subject, it becomes difficult to properly detect the presence of the subject, and there is a risk that vital signs will be measured from the signal from the piezoelectric sensor at an inappropriate time.

[0005] The present invention was conceived in light of the above circumstances, and an object of the present invention is to provide a sensor system that combines two types of sensors and is capable of improving the accuracy of measurements.

[0006] The sensor system provided by the present invention comprises a first sensor that converts a first physical quantity of a measured object into a first signal and outputs the first signal; a second sensor that converts a second physical quantity of the measured object into a second signal and outputs the second signal; and a control unit electrically connected to the first sensor and the second sensor, wherein the second physical quantity is correlated with whether the measured object is in a state suitable for detection by the first sensor, and the control unit performs a first judgment process that judges whether the measured object is in a state suitable for detection by the first sensor based on the second signal; a measurement process that measures first information of the measured object using the first signal if the first judgment process judges that the measured object is in a suitable state; a second judgment process that judges whether the measured object is in a state suitable for detection by the first sensor based on the first signal; and a correction process that corrects the judgment criteria of the first judgment process using the judgment result of the second judgment process and the second signal at the time the judgment was made.

[0007] In a preferred embodiment of the present invention, the correction process corrects the judgment criterion of the first judgment process using the first signal when the second judgment process judges that the state is not suitable.

[0008] In a preferred embodiment of the present invention, in the correction process, if a state determined to be inappropriate by the second judgment process continues for a predetermined period of time, the judgment criteria of the first judgment process are corrected using the first signal for that predetermined period.

[0009] In a preferred embodiment of the present invention, the first physical quantity is a physical quantity corresponding to a vital sign of the human being to be measured, and the second physical quantity correlates with whether the human being to be measured is present in a position where it can be detected by the first sensor.

[0010] In a preferred embodiment of the present invention, the first sensor is a piezoelectric sensor, and the second sensor is a capacitance sensor.

[0011] According to the present invention, it is possible to improve the accuracy of measurements using a combination of two types of sensors.

[0012] Other features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0013] FIG. 1 is a system configuration diagram showing a sensor system according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing a sensor system according to the first embodiment of the present invention. FIG. 3 is a partial cross-sectional perspective view showing an example of a sensor unit of the sensor system according to the first embodiment of the present invention. FIG. 4 is a flowchart showing an example of a measurement method of the sensor system according to the first embodiment of the present invention. FIG. 5 is a graph showing an example of a measurement method of the sensor system according to the first embodiment of the present invention. FIG. 6 is a graph showing another example of the measurement method of the sensor system according to the first embodiment of the present invention. FIG. 7 is a flowchart showing an example of a measurement method of the sensor system according to a second embodiment of the present invention. FIG. 8 is a graph showing an example of a measurement method of the sensor system according to the second embodiment of the present invention.

[0014] Preferred embodiments of the present invention will now be described in detail with reference to the drawings.

[0015] Terms such as "first," "second," etc. in this disclosure are used for identification purposes only and are not intended to impose any ordering on their objects.

[0016] 1 to 3 show a sensor system according to a first embodiment of the present invention. The sensor system A1 of this embodiment includes a first sensor 11, a second sensor 12, and a control unit 2. The specific use of the sensor system A1 is not limited in any way. The sensor system A1 is used, for example, to measure predetermined measurement items of various measurement targets at timing suitable for the measurement.

[0017] Examples of predetermined measurement items to be measured include human vital signs. Typical vital signs include pulse, respiration, body temperature, blood pressure, etc. The environment in which the vital signs are measured may be, for example, a bed, chair, etc. in a hospital, nursing home, hotel, residence, etc., or a chair, etc. in an office, beauty salon, movie theater, car, airplane, train, etc.

[0018] The first sensor 11 is a sensor for measuring first information, which is a measurement parameter of the measurement object. The first sensor 11 converts a first physical quantity of the measurement object into a first electrical signal and outputs the first electrical signal. The specific configuration of the first sensor 11 is not limited in any way. The first sensor 11 may be configured to convert various types of first physical quantities into first signals, and may include various sensor elements and a processing unit or amplifier for signal processing the output of the sensor elements as the first signal. Examples of the first sensor 11 include piezoelectric sensors, force sensors, acceleration sensors, gyro sensors, microphone sensors, ultrasonic sensors, Doppler sensors, optical fiber sensors, proximity sensors, displacement sensors, image sensors, magnetic sensors, current sensors, voltage sensors, capacitance sensors, optical sensors, temperature sensors, pressure sensors, acoustic sensors, humidity sensors, moisture sensors, color vision sensors, and pyroelectric sensors. For example, if the first information is vital signs such as pulse, respiration, body temperature, or blood pressure, the first physical quantity may be acceleration, vibration, pressure, or the like corresponding to these vital signs. When the first information is a vital sign, the first sensor 11 may be a piezoelectric sensor, an acceleration sensor, a gyro sensor, a microphone sensor, an ultrasonic sensor, a Doppler sensor, a pressure sensor, an acoustic sensor, a moisture sensor, a pyroelectric sensor, etc. When the first sensor 11 detects or outputs a rate of change as the first physical quantity, the first sensor 11 may be a piezoelectric sensor, an acceleration sensor, a gyro sensor, a microphone sensor, a Doppler sensor, an optical fiber sensor, an acoustic sensor, a pyroelectric sensor, etc. When the first sensor 11 detects or outputs a change amount as the first physical quantity, the first sensor 11 may be a force sensor, an ultrasonic sensor, a Doppler sensor, an optical fiber sensor, a proximity sensor, a displacement sensor, a temperature sensor, a pressure sensor, a humidity sensor, a moisture sensor, a color vision sensor, a capacitance sensor, etc. In the following description, unless otherwise specified, a case will be described in which the first sensor 11 is a piezoelectric sensor.

[0019] The specific configuration of the piezoelectric sensor as the first sensor 11 is not limited in any way, and for example, a configuration including a core wire in which metal foil is spirally wound around a resin wire, an organic piezoelectric layer covering the core wire, and a conductor layer covering the organic piezoelectric layer, as disclosed in Japanese Patent Publication No. 6501958, may be adopted.

[0020] The second sensor 12 converts a second physical quantity of the measurement object into a second electrical signal and outputs the second electrical signal. The second physical quantity correlates with whether the measurement object is in a state suitable for detection by the first sensor 11. Whether the measurement object is in a state suitable for detection by the first sensor 11 can be determined, for example, by whether the measurement object is located in a position where the first sensor 11 can function, whether the measurement object is placed in a state or posture where the first sensor 11 can function, or whether the measurement object is placed at a temperature, pressure, noise level, or the like where the first sensor 11 can function. The specific configuration of the second sensor 12 is not limited in any way. The second sensor 12 may be configured to convert various types of second physical quantities into second signals, and may include various sensor elements and further include a processing unit or an amplifier for signal processing the output of the sensor elements as the second signal. Examples of the second sensor 12 include a capacitance sensor, an optical sensor, a temperature sensor, a pressure sensor, an acoustic sensor, a force sensor, a gyro sensor, a microphone sensor, an ultrasonic sensor, a Doppler sensor, an optical fiber sensor, a proximity sensor, a displacement sensor, an image sensor, a magnetic sensor, a current sensor, a voltage sensor, a humidity sensor, a moisture sensor, a color vision sensor, a pyroelectric sensor, and a piezoelectric sensor. When the second sensor 12 detects or outputs a rate of change as the second physical quantity, a piezoelectric sensor, an acceleration sensor, a gyro sensor, a microphone sensor, a Doppler sensor, an optical fiber sensor, an acoustic sensor, a pyroelectric sensor, and the like is used as the second sensor 12. When the second sensor 12 detects or outputs a quantity of change as the second physical quantity, a force sensor, an ultrasonic sensor, a Doppler sensor, an optical fiber sensor, a proximity sensor, a displacement sensor, a temperature sensor, a pressure sensor, a humidity sensor, a moisture sensor, a color vision sensor, a capacitance sensor, and the like is used as the second sensor 12. The first sensor 11 and the second sensor may be the same type of sensor or different types of sensors. If the first sensor 11 and the second sensor 12 are the same type of sensor, they may be installed in different locations, or may have different detection or output ranges, sampling rates, etc. If the first sensor 11 and the second sensor 12 are different types of sensors, this is preferable for more accurately detecting the first physical quantity and the second physical quantity.Preferably, the first sensor 11 outputs the first physical quantity as a data signal representing the rate of change, and the second sensor 12 outputs the second physical quantity as a data signal representing the amount of change. In the following description, unless otherwise specified, the second sensor 12 will be described as a capacitance sensor. The specific configuration of the capacitance sensor serving as the second sensor 12 is not limited in any way, and may be, for example, a configuration in which a copper foil and an insulating layer are combined.

[0021] The first sensor 11 and the second sensor 12 may be configured as separate components and individually attached to the measurement target. Alternatively, the first sensor 11 and the second sensor 12 may be configured as an integrated unit and collectively attached to the measurement target. In this embodiment, the sensor system A1 includes a sensor unit 10. As shown in FIG. 3 , the sensor unit 10 includes the first sensor 11 and the second sensor 12 integrated via a base material 19. The base material 19 is, for example, a fabric-like strip member. The base material 19 has multiple cavities extending in the longitudinal direction. The first sensor 11 is housed in the central cavity in the width direction. The second sensors 12 are housed in the cavities on both sides in the width direction. Note that the portions of the base material 19 housing the first sensor 11 and the second sensor 12 may be slightly bulged along the longitudinal direction. For example, an anti-slip portion (not shown) may be provided in these portions.

[0022] 2, the sensor unit 10 is installed on the seat of a chair 91. This allows the vital signs of a person sitting on the chair 91 to be measured.

[0023] The control unit 2 receives the first signal from the first sensor 11 and the second signal from the second sensor 12 and executes a process of measuring vital signs as first information using the first signal and the second signal. The specific configuration of the control unit 2 is not limited in any way and may include, for example, a CPU, memory, various interfaces, etc. The control unit 2 may also include a dedicated processing circuit for processing signals from both or either of the first sensor 11 and the second sensor 12. The first sensor 11 and the second sensor 12 are electrically connected to the control unit 2. The electrical connection may be a wired connection, a wireless connection, etc.

[0024] Next, a measurement method using the sensor system A1 will be described below with reference to FIGS.

[0025] FIG. 4 is a flowchart showing an example of a measurement method using the sensor system A1. When the measurement method starts in step S0, the first sensor 11 and the second sensor 12 begin outputting signals. FIG. 5 is a graph showing an example of the output of the first signal V1 from the first sensor 11 and the second signal V2 from the second sensor 12. The horizontal axis represents time, and the vertical axis represents the first signal V1 on the upper side and the second signal V2 on the lower side. In the figure, the measurement method of this embodiment starts at time t1. The first signal V1 from the first sensor 11 is set as a signal that can take both positive and negative values, and the second signal V2 from the second sensor 12 is set as a signal that can take either 0 or a positive value. Note that these settings for the first signal V1 and the second signal V2 are merely examples. The first threshold value Vth1 and the second threshold value Vth2, described below, are appropriately set depending on the numerical ranges set for the first signal V1 and the second signal V2.

[0026] Step S1 in FIG. 4 is a first determination process. In the first determination process, it is determined whether the measurement target is in a state suitable for detection by the first sensor 11 based on the second signal V2. In this embodiment, a second threshold value Vth2 shown in FIG. 5 is set as a criterion for this determination. For example, if the second sensor 12 is a capacitance sensor, when no person is sitting on the chair 91, i.e., when the state is not suitable for measurement by the first sensor 11, the second signal V2 is almost zero. On the other hand, when a person sits on the chair 91, i.e., when the state is suitable for measurement by the first sensor 11, the second signal V2 rises to a predetermined value. The second threshold value Vth2 is set to a value below the predetermined value when a person is sitting on the chair 91.

[0027] From time t1 to time t6, the second signal V2 is smaller than the second threshold value Vth2. Therefore, step S1 in FIG. 4 is No, and the measurement process of step S2 is not performed. On the other hand, at time t7 in FIG. 5, the second signal V2 exceeds the second threshold value Vth2. This is thought to be a change caused by a person sitting on the chair 91. In this case, step S1 in FIG. 4 is Yes, and the measurement process of step S2 is performed.

[0028] In the measurement process of step S2, the control unit 2 measures the first information of the measurement target, such as the pulse, using the first signal V1. The specific signal processing performed by the control unit 2 to measure the pulse is not limited in any way. For example, various conventionally known techniques such as various types of filtering and FFT analysis can be employed.

[0029] The measurement process of step S2 is performed while the second signal V2 exceeds the second threshold value Vth2. At time t8, the second signal V2 falls below the second threshold value Vth2, and the measurement process of step S2 ends. The measurement results (pulse rate) of the measurement process (step S2) from time t7 to time t8 may be stored in a memory unit of the control unit 2, for example, or may be transmitted from the control unit 2 to another device.

[0030] From time t1 to time t6, the second signal V2 is smaller than the second threshold Vth2 in the first judgment process of step S1 (step S1: No), so the measurement process (step S2) is not performed and the second judgment process of step S3 is performed.

[0031] The second determination process determines whether the measurement target is in a state suitable for detection by the first sensor 11 based on the first signal V1. In this embodiment, a first threshold value Vth1 shown in FIG. 5 is set as a criterion for this determination. In this embodiment, the first sensor 11 is a piezoelectric sensor. Therefore, when a person is sitting in the chair 91, the first signal V1 becomes a waveform signal with a relatively large amplitude by detecting vibrations such as a pulse. On the other hand, when no person is sitting in the chair 91, the first signal V1 becomes a signal indicating a substantially constant value without a significant waveform. The first threshold value Vth1 is set, for example, as a positive value that the absolute value of the first signal V1 can exceed when a person is sitting in the chair 91.

[0032] In the present embodiment, when the absolute value of the first signal V1 exceeds the first threshold Vth1, it is considered that a person is sitting in the chair 91 and that vibrations as a first physical quantity corresponding to the person's pulse or the like are being detected by the first sensor 11. Therefore, when the absolute value of the first signal V1 exceeds the first threshold Vth1, it can be determined that the state is suitable for measurement by the first sensor 11. On the other hand, when the absolute value of the first signal V1 is below the first threshold Vth1, it can be determined that no person is sitting in the chair 91 and that the state is not suitable for measurement by the first sensor 11.

[0033] In the second determination process (step S3), various signal processing techniques may be appropriately performed to more accurately determine the absolute value of the first signal V1 compared with the first threshold Vth1. For example, the standard deviation of the first signal V1 may be calculated and the standard deviation may be compared with the first threshold Vth1 adjusted to the standard deviation. Alternatively, the coefficient of variation of the first signal V1 may be calculated and the coefficient of variation may be compared with the first threshold Vth1 adjusted to the coefficient of variation. Alternatively, the first signal V1 may be subjected to an FFT analysis, and if the peak frequency determined by the FFT analysis is equal to or less than a predetermined threshold frequency, the first signal V1 may be determined to be in a state suitable for measurement by the first sensor 11. Alternatively, the maximum amplitude, integral value, or root mean square (RMS) value of the first signal V1 may be used. Furthermore, these comparison techniques may be appropriately combined. Furthermore, the first signal V1 may be subjected to filtering, such as a low-pass filter, for the purpose of noise removal, for the comparison.

[0034] A preferred example of a method for comparing the first signal V1 with the first threshold Vth1 is to calculate the coefficient of variation of the first signal V1 after low-pass filtering. A value corresponding to the coefficient of variation is set in advance as the first threshold Vth1. If the coefficient of variation of the first signal V1 remains below the first threshold Vth1 for a predetermined period of time, it is determined that the state is suitable for measurement by the first sensor 11.

[0035] In this embodiment, if the second judgment process determines that the state is not suitable, i.e., if the absolute value of the first signal V1 is smaller than the first threshold value Vth1 (step S3: Yes), the correction process of step S4 is performed.

[0036] The correction process is a process of correcting the determination criterion of the first determination process (step S1) by using the determination result of the second determination process (step S3) and the second signal V2 at the time when the determination was made. In this embodiment, the correction process corrects the determination criterion when the absolute value of the first signal V1 falls below the first threshold Vth1 for a predetermined period of time from the time t1.

[0037] In FIG. 5 , the predetermined period is indicated as time ta. If the absolute value of the first signal V1 falls below the first threshold Vth1 at time t1 and this state continues for time ta, the control unit 2 corrects the judgment criterion of the first judgment process (step S1) at time t2. The specific method for correcting this judgment criterion is not limited in any way. For example, a zero point correction of the second signal V2 may be performed, or the second threshold Vth2 may be corrected. When performing a zero point correction of the second signal V2, the control unit 2 temporarily stores, for example, the second signal V2 from time t1 to time t2 in advance. Then, the value of the second signal V2 from time t1 to time t2 is used to perform the zero point correction of the second signal V2.

[0038] The specific method for using the value of the second signal V2 from time t1 to time t2 is not limited in any way. Examples of the value include the average value, median value, standard deviation, coefficient of variation, maximum amplitude, energy (integral value), mode, RMS (root mean square), norm (magnitude when considered as a vector), and gradient between two points of the value of the second signal V2 from time t1 to time t2. Various values ​​calculated after various filtering processes may be used. Examples of various filtering processes include moving average, low-pass filter, high-pass filter, band-pass filter trimmed average, missing value processing, outlier processing, median filter, Kalman filter, regression analysis, and frequency analysis. For example, when the average value is used, the average value of the second signal V2 from time t1 to time t2 is calculated as the correction value V2r. The value of the correction value V2r is then set as the zero point of the second signal V2 from time t2 onward. 5, at time t2, the dotted arrow extending from the first signal V1 (upper side) to the second signal V2 (lower side) indicates that correction has been performed by the correction process (step S4), thereby completing the correction process of step S4.

[0039] If the process is not terminated in step S5, step S1: No → step S3: Yes occurs from time t2 to time t3, and the correction process (step S4) is performed at time t3. Also, at time t3, step S1: No → step S3: Yes occurs, but before the time ta has elapsed from time t3, the absolute value of the first signal V1 exceeds the first threshold Vth1 at time t4 (step S3: No). In this case, since the second signal V2 is below the second threshold Vth2, it is assumed that no person is sitting on the chair 91, but an object that emits unintended vibrations is placed on the chair 91. Therefore, the correction process of step S4 is not performed. Note that the measurement process (step S2) may be performed from time t4 to time t5.

[0040] After this, in the illustrated example, for example, at time t5, the absolute value of the first signal V1 falls below the first threshold value Vth1, and the correction process (step S4) is executed at time t6 after the time ta has elapsed. Also, the measurement process (step S2) is executed from time t7 to time t8, the correction process (step S4) is executed at time t9 after the time ta has elapsed since time t8, and the measurement process (step S2) is executed from time t10 to time t11.

[0041] If the process related to the measurement method is not to be ended (step S5: No), step S1 and subsequent steps are executed again. If the process related to the measurement method is to be ended (step S5: Yes), the process related to the measurement method is ended (step S6).

[0042] Next, the operation of the sensor system A1 will be described.

[0043] In the sensor system A1, the judgment criterion of the first judgment process (step S1) is corrected using the judgment result of the second judgment process (step S3) and the second signal V2 at the time of the judgment. This makes it possible to reduce judgment errors in the first judgment process due to the influence of unintended changes in the state of the measurement target.

[0044] 6, the value of the second signal V2 gradually increases after the measurement method is started at time t1. An example of such a situation is when water gradually spills unintentionally onto the chair 91, and this water affects the detection by the second sensor 12.

[0045] Unlike the present embodiment, the second signal V2' in the figure is represented by a phantom line as the output signal of the second sensor 12 when the determination process (step S3) and correction process (step S4) are not performed. From time t1, the second signal V2' gradually increases and exceeds the second threshold value Vth2 at time t7. Therefore, the control unit 2 determines that the measurement object is in a state suitable for measurement by the first sensor 11 (step S1: Yes) and performs the measurement process (step S2). At time t7, no person is sitting in the chair 91 or lying on the target bed, so the measurement result from the measurement process is recorded as an inappropriate result.

[0046] In this embodiment, a correction process (step S4) is performed from time t1 through time ta to time t2. As a result, the second signal V2 from time t1 to time t2 undergoes correction processes such as zero point correction using the second signal V2 from time t1 to time t2. In the illustrated example, the second signal V2 is zero point corrected at time t2, and the second signal V2 drops to a value close to zero. Similarly, when conditions are met from time t3 to time t9, the correction process (step S4) is performed at each time. As a result, even if the value of the second signal V2 gradually increases, an appropriate determination is made in the first determination process (step S1) from time t1 to time t9 when no person is sitting in the chair 91, preventing the measurement process (step S2) from being erroneously performed. Then, when a person actually sits in the chair 91 at time t10, the value of the second signal V2 increases significantly and exceeds the second threshold value Vth2. As a result, during the period from time t10 to time t11, the first determination process determines that the state is suitable for measurement by the first sensor 11 (step S1: Yes), and the measurement process (step S2) is performed appropriately. Therefore, the sensor system A1 can improve the accuracy of measurements using a combination of two types of sensors.

[0047] As shown in FIG. 4 , in this embodiment, if the second determination process determines that the measurement target is not in a state suitable for measurement by the first sensor 11 (step S3: Yes), a correction process (step S4) is performed. In this case, the second signal V2 used in the correction process is a value obtained when, for example, no person is sitting on the chair 91. Therefore, a zero-point correction of the second signal V2 can be performed in the correction process. This correction has the advantage that a state in which the measurement target is not suitable for measurement by the first sensor 11, such as when no person is sitting on the chair 91, can be more accurately determined based on the value of the second signal V2. Furthermore, as shown in FIG. 5 , the correction process and the measurement process can be performed at separate times, which is preferable for reducing the processing load on the control unit 2.

[0048] 5, in this embodiment, when the absolute value of the first signal V1 falls below the first threshold Vth1, i.e., when the state in which step S3 in Fig. 4 returns "Yes" continues for a predetermined period of time ta, the correction process (step S4) is executed. Therefore, when the absolute value of the first signal V1 falls below the first threshold Vth1 for only a very short period of time due to an unexpected event that should not be taken into consideration, it is possible to avoid unnecessarily executing the correction process and prevent unintended degradation of measurement accuracy.

[0049] 7 and 8 show other embodiments of the present invention. In these figures, elements that are the same as or similar to those in the above embodiment are given the same reference numerals. Furthermore, the configurations of the various parts in each of the modified examples and embodiments can be combined with each other as appropriate within the scope of not causing technical contradictions.

[0050] 7 shows a measurement method of a sensor system according to a second embodiment of the present invention. In this embodiment, if the result of the second determination process (step S3) indicates that the measurement target is in a state suitable for measurement by the first sensor 11, a correction process (step S4) is executed.

[0051] In this embodiment, if the measurement object is in a state suitable for measurement by the first sensor 11, such as when the second signal V2 exceeds the second threshold Vth2 in the first judgment process (step S1: yes), the measurement process (step S2) is executed as in the first embodiment (times t2 to t4, times t5 to t7), and the second judgment process (step S3) is also executed.

[0052] If the second determination process determines that the measurement object is in a state suitable for measurement by the first sensor 11, such as when the absolute value of the first signal V1 exceeds the first threshold value Vth1 (step S3: Yes), the control unit 2 performs a correction process (step S4). In this embodiment, when the correction process (step S4) is performed, for example, a person is sitting on the chair 91, and the second signal V2 is rising (time t2 to time t4), as shown in FIG. 8 . If the absolute value of the first signal V1 continues to exceed the first threshold value Vth1 for a predetermined time tb, the control unit 2 corrects the determination criterion for the first determination process using the second signal V2 from time t2 to time t3.

[0053] In this embodiment, a case will be described in which the second threshold Vth2 is corrected using the second signal V2 from time t2 to time t3. For example, the average value of the second signal V2 from time t2 to time t3 is compared with the second threshold Vth2, and a difference value is calculated. If the calculated difference value is smaller than a predetermined appropriate difference value, it is assumed that the second threshold Vth2 is set too high. Therefore, the control unit 2 decreases the second threshold Vth2 by a predetermined rate or the like. After time t3, the decreased second threshold Vth2 is used.

[0054] Furthermore, at time t5, as a result of the second determination process, it is determined that the measurement object is in a state suitable for measurement by the first sensor 11 (step S3: Yes). In the illustrated example, the difference value between the second signal V2 and the second threshold value Vth2 is still smaller than the predetermined appropriate difference value. Therefore, the second threshold value Vth2 is decreased at time t6. From time t6 onwards, the decreased second threshold value Vth2 is used.

[0055] This embodiment also improves the accuracy of measurements using a combination of two types of sensors. As can be understood from this embodiment, the value of the second signal V2 used in the correction process in the present invention may be the second signal V2 when the object to be measured is in a state suitable for measurement by the first sensor 11, or may be the second signal V2 when the object to be measured is in an unsuitable state for measurement by the first sensor 11.

[0056] The sensor system according to the present invention is not limited to the above-described embodiment. The specific configuration of each component of the sensor system according to the present invention can be freely designed in various ways. In the above-described embodiment, when the first sensor 11 detects vital signs or the like, a threshold value corresponding to a lower limit value or the like may be applied to the first sensor 11 to prevent a signal due to noise or the like from being mistakenly output as a detection signal for vital signs or the like. Furthermore, a process may be further added to correct the threshold value of the first sensor 11 using the output of the second sensor 12.

[0057] A1: Sensor system 2: Control unit 10: Sensor unit 11: First sensor 12: Second sensor 19: Base material 91: Chair V1: First signal V2: Second signal V2r: Correction value Vth1: First threshold value Vth2: Second threshold value

Claims

1. A sensor system comprising: a first sensor that converts a first physical quantity of an object to be measured into a first signal and outputs the first signal; a second sensor that converts a second physical quantity of the object to be measured into a second signal and outputs the second signal; and a control unit electrically connected to the first sensor and the second sensor, wherein the second physical quantity has a correlation with whether the object to be measured is in a state suitable for detection by the first sensor, and the control unit performs: a first determination process that determines whether the object to be measured is in a state suitable for detection by the first sensor based on the second signal; a measurement process that measures first information about the object to be measured using the first signal when the first determination process determines that the object to be measured is in a suitable state; a second determination process that determines whether the object to be measured is in a state suitable for detection by the first sensor based on the first signal; and a correction process that corrects the determination criterion of the first determination process using the determination result of the second determination process and the second signal at the time the determination was made.

2. The sensor system of claim 1, wherein the correction process corrects the judgment criteria of the first judgment process using the first signal when the second judgment process determines that the state is not suitable.

3. A sensor system as described in claim 2, wherein in the correction process, if a state determined to be inappropriate by the second judgment process continues for a predetermined period, the judgment criteria of the first judgment process are corrected using the first signal for that predetermined period.

4. A sensor system as described in any one of claims 1 to 3, wherein the first physical quantity is a physical quantity corresponding to a vital sign of the human being being measured, and the second physical quantity correlates with whether or not the human being being measured is in a position where it can be detected by the first sensor.

5. The sensor system of claim 4, wherein the first sensor is a piezoelectric sensor and the second sensor is a capacitive sensor.

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