Biological condition measurement device and biological condition measurement method

Abstract

To ensure accuracy in measuring biological conditions while suppressing the increase in the burden and time required for measuring biological conditions. [Solution] The control device receives the reflected wave of a chirp signal transmitted at a predetermined period and measures the biological state of the subject based on the phase change of the vital measurement position (measurement target frequency) in the reflected wave. At the end of each chirp period, the control device calculates the frequency characteristics of the reflected wave for one chirp period, searches for the component with the highest intensity within the measurement site range in the frequency characteristics, identifies the frequency of the found component with the highest intensity as the maximum intensity position, maintains the current vital measurement position if the difference between the maximum intensity position and the current vital measurement position is less than the allowable value, discards the current vital measurement position and resets the vital measurement position if the difference is greater than or equal to the allowable value.

Description

Technical Field

[0001] The present disclosure relates to a biological state measurement device and a biological state measurement method.

Background Art

[0002] Japanese Patent No. 7327868 (Patent Document 1) discloses a biological state measurement device that measures a person's biological state by transmitting a chirp signal in a frequency band of millimeter waves or higher at each predetermined frame period and analyzing a reflected wave signal generated by reflection of the chirp signal by the human body. This biological state measurement device converts a reflected wave signal into a frequency signal at each frame period, sets the frequency of a component with a large intensity among the frequency components included in the frequency signal as a measurement target frequency, and measures a person's biological state based on a phase change of the measurement target frequency in the reflected wave. Further, this biological state measurement device performs a process of setting the measurement target frequency at each predetermined frequency fixing period. That is, this biological state measurement device once selects a measurement target frequency and then fixes the currently set measurement target frequency without searching for a component with a large intensity until a predetermined frequency fixing period elapses.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, in the biological state measurement device disclosed in Japanese Patent No. 7327868 (Patent Document 1), once the measurement target frequency is set, the measurement target frequency is fixed without searching for a component with a large intensity until a predetermined frequency fixing period elapses.

[0005] However, if the person being measured moves, such as by turning over in their sleep, during the frequency-fixed period, there is a concern that the high-intensity components may deviate significantly from the currently set measurement frequency, thereby degrading the accuracy of the measurement of the person's biological state.

[0006] On the other hand, in order to accurately measure a person's respiratory rate and heart rate, it is necessary to continuously observe the phase change of the same target frequency for a predetermined period (a period longer than the cycle of a person's respiration and heartbeat). Therefore, if the target frequency is changed simply because the value of a high-intensity component changes slightly, the phase data of the target frequency before the change must be discarded, and the phase data of the target frequency after the change must be collected again, which raises concerns that the load and time required for measurement will increase.

[0007] Furthermore, in the biological state measuring device disclosed in Japanese Patent Publication No. 7327868 (Patent Document 1), the range for searching for high-intensity components in the process of setting the target frequency is set to the entire frequency band included in the frequency signal. As a result, signals reflected by objects other than the target of measurement are also included in the search range, which raises concerns that the load and time required for measurement will increase unnecessarily, and that the measurement accuracy will deteriorate.

[0008] This disclosure was made to solve the above-mentioned problems, and its purpose is to ensure the accuracy of measuring the biological state of a subject while suppressing the increase in the burden and time required for measuring the biological state. [Means for solving the problem]

[0009] The biological state measuring device according to this disclosure is a biological state measuring device for measuring the biological state of a target, comprising: a transmitting unit that transmits a chirp signal whose frequency changes during the chirp period at a predetermined period; a receiving unit that receives a reflected wave generated when the chirp signal is reflected by the target; and a control device that measures the biological state of the target based on the phase change of the measurement target frequency in the reflected wave. The control device calculates a frequency characteristic representing the correspondence between the frequency components and intensity of the reflected wave for one chirp period each time the chirp period ends, searches for the component with the maximum intensity within a first frequency range corresponding to the position range of the measurement site of the target in the frequency characteristic, performs a identification process to identify the frequency of the searched component with the maximum intensity as the maximum intensity frequency, maintains the current measurement target frequency if the difference between the maximum intensity frequency and the current measurement target frequency is less than an allowable value, and discards the current measurement target frequency and resets the measurement target frequency if the difference between the maximum intensity frequency and the current measurement target frequency is greater than or equal to an allowable value.

[0010] The present disclosure provides a method for measuring the biological state of a target, comprising the steps of: transmitting a chirp signal whose frequency changes during a chirp period at predetermined intervals; receiving a reflected wave generated when the chirp signal is reflected by the target; and measuring the biological state of the target based on the phase change of the measurement target frequency in the reflected wave. The steps for measuring the biological state include: calculating a frequency characteristic that represents the correspondence between the frequency components and intensity of the reflected wave for one chirp period each time a chirp period ends; performing a identification process that searches for the component with the maximum intensity within a first frequency range corresponding to the position range of the measurement site of the target in the frequency characteristic, and identifying the frequency of the searched component with the maximum intensity as the maximum intensity frequency; maintaining the current measurement target frequency if the difference between the maximum intensity frequency and the current measurement target frequency is less than an allowable value; and discarding the current measurement target frequency and resetting the measurement target frequency if the difference between the maximum intensity frequency and the current measurement target frequency is greater than or equal to an allowable value. [Effects of the Invention]

[0011] According to this disclosure, when measuring the biological state of a subject, it is possible to ensure the accuracy of the measurement of the biological state while suppressing an increase in the burden and time required for measuring the biological state. [Brief explanation of the drawing]

[0012] [Figure 1] This diagram schematically shows an example of the overall configuration of a bio-monitoring system. [Figure 2] This figure shows an example of the arrangement of a biological condition measurement device. [Figure 3] This is a functional block diagram that schematically shows the functions of a biological state measurement device. [Figure 4] This diagram schematically illustrates the processing flow from transmitting a chirp signal to calculating the frequency characteristics. [Figure 5] This figure shows an example of the frequency characteristics of a reflected wave. [Figure 6] This diagram illustrates an example of a method for determining whether or not a person requiring care is in bed. [Figure 7] This diagram illustrates a method for setting the location for vital sign measurement. [Figure 8] This diagram illustrates a method for measuring the heart rate and respiratory rate of a person receiving care. [Figure 9] This is a flowchart showing an example of the processing procedure for a control device. [Modes for carrying out the invention]

[0013] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0014] FIG. 1 is a diagram schematically showing an example of the overall configuration of a biological monitoring system 1 including a biological state measuring device 10 according to the present embodiment. The biological monitoring system 1 performs vital measurement for non-contact measurement of biological information (vital signs, specifically, heart rate and respiratory rate) of a care recipient as a measurement target, and can notify a caregiver who is at a location away from the care recipient of the result of the vital measurement. Note that the measurement target of the biological monitoring system 1 is not necessarily limited to a care recipient, and may be a person other than the care recipient or an animal other than a person.

[0015] The biological monitoring system 1 includes a biological state measuring device 10 and communication terminals such as a personal computer 3, a smartphone 4, and a tablet 5. The biological state measuring device 10 and each of the communication terminals 3 to 5 can communicate with each other via the network 2 in a wired or wireless manner.

[0016] The biological state measuring device 10 is arranged around the care recipient (for example, as shown in FIG. 2 described later, the bed 16 on which the care recipient 17 is lying).

[0017] The biological state measuring device 10 includes a millimeter wave radar 11, a camera 12, a control device 13, and a communication device 14.

[0018] The communication device 14 has a function of communicating with each of the above-described communication terminals 3 to 5 in a wired or wireless manner.

[0019] The millimeter wave radar 11 transmits and receives radio waves having a frequency in the millimeter wave band or higher. Specifically, the millimeter wave radar 11 transmits radio waves having a frequency in the millimeter wave band or higher radially (conically) toward the care recipient, and receives reflected waves generated by reflection of the transmitted radio waves by the care recipient or an object other than the care recipient. The camera 12 captures an image of the care recipient.

[0020] The control device 13 comprises a CPU (Central Processing Unit), memory, and input / output ports for inputting and outputting various signals (none of which are shown). The control device 13 uses a millimeter-wave radar 11 to measure the vital signs (heart rate and respiratory rate) of the person being cared for and transmits the measurement results to each communication terminal 3-5 via the communication device 14. The control device 13 can also transmit video signals from the camera 12 to each communication terminal 3-5 in real time via the communication device 14, if necessary.

[0021] Information transmitted from the vital signs measurement device 10 (such as the care recipient's heart rate, respiratory rate, and video from camera 12) is displayed on the screens of each communication terminal 3 to 5. By viewing the screens of each communication terminal 3 to 5, caregivers can remotely check the care recipient's vital signs in real time.

[0022] Figure 2 shows an example of the placement of the biological condition measurement device 10. Figure 2 shows an example in which the biological condition measurement device 10 is attached to the upper end of the headboard 16a of the bed 16 in which the person receiving care 17 is lying. The irradiation range 15 of the radio waves transmitted from the millimeter-wave radar 11 of the biological condition measurement device 10 is adjusted to include the person receiving care 17 lying in the bed 16.

[0023] Furthermore, the location where the vital signs measurement device 10 is installed is not limited to the bed 16, but rather any location where radio waves transmitted from the millimeter-wave radar 11 can reach the person receiving care 17 lying in bed 16. For example, the vital signs measurement device 10 may be installed on the wall or ceiling of the room where the bed 16 is located.

[0024] The radio waves transmitted from the millimeter-wave radar 11 strike the person receiving care 17 and are reflected, and the reflected waves 15a from the person receiving care 17 are received by the millimeter-wave radar 11. The biological condition measuring device 10 can measure the distance between the millimeter-wave radar 11 and the reflection point of the radio waves by measuring the time from when the radio waves are transmitted from the millimeter-wave radar 11 until the reflected waves 15a are received.

[0025] It is known that the surface of a person's body vibrates slightly due to their breathing and heartbeat. The biostatus measurement device 10 measures the heart rate and respiratory rate of a person 17 who is lying in bed 16 by detecting the slight vibrations on the body surface caused by the movement of the lungs and heart of the person 17 from the phase change of the reflected wave.

[0026] The body surface of a person vibrates mainly in the chest and abdomen due to the movement of the lungs and heart, while other parts vibrate less. When the person being cared for 17 is lying in bed 16, the range in which the person being cared for 17's chest and abdomen can be located is generally fixed. Therefore, the biological condition measuring device 10 according to this embodiment uses the chest and abdomen of the person being cared for 17 as measurement sites and performs vital sign measurements based on reflected wave data from the "measurement site region" in which the measurement sites of the person being cared for 17 can be located when the person being cared for 17 is lying in bed 16 (see Figure 7 below).

[0027] Furthermore, vital sign measurement by the vital sign measuring device 10 is based on the premise that the person being cared for 17 is lying on the bed 16. Therefore, the vital sign measuring device 10 also has a function to determine whether or not the person being cared for 17 is on the bed 16. Specifically, the vital sign measuring device 10 determines whether or not the person being cared for 17 is on the bed 16 based on reflected wave data from the "bed area" where the bed 16 is placed (see Figure 6 below). The bed area includes the measurement site area mentioned above, and is a wider area than the measurement site area. The vital sign measuring device 10 then measures the vital signs of the person being cared for 17 only if it is determined that the person being cared for 17 is on the bed 16.

[0028] Furthermore, the vital signs measurement device 10 can also use the camera 12 to detect when the person being cared for 17 has made an action to get out of bed 16, and can then notify each of the communication terminals 3 to 5 that the person being cared for 17 has made an action to get out of bed.

[0029] Figure 3 is a functional block diagram schematically showing the functions of the biological condition measurement device 10 related to vital sign measurement.

[0030] The millimeter-wave radar 11 includes a transmitting unit 11a, a receiving unit 11b, and a signal generating unit 11c. The transmitting unit 11a transmits radio waves corresponding to the transmission signal from the signal generating unit 11c. The receiving unit 11b receives the radio wave signal of the reflected wave generated when the radio waves transmitted by the transmitting unit 11a are reflected by the person being cared for 17, and outputs it to the control device 13.

[0031] The signal generation unit 11c generates a transmission signal to the transmission unit 11a for transmitting a chirp signal whose frequency changes during a predetermined chirp period at a predetermined interval. The transmission unit 11a transmits a chirp signal whose frequency changes during a predetermined chirp period at a predetermined interval in response to the transmission signal from the signal generation unit 11c. The receiving unit 11b receives the radio wave signal of the reflected wave generated when the chirp signal is reflected by the person being cared for 17. The signal generation unit 11c also has a function to detect the difference between the transmission signal and the radio wave signal received by the receiving unit 11b.

[0032] The control device 13 includes a signal acquisition unit 30, a signal conversion unit 40, a frequency conversion unit 50, a measurement position setting unit 60, a phase data acquisition unit 70, and a vital measurement unit 80.

[0033] The signal acquisition unit 30 acquires the reflected radio wave signal from the receiver unit 11b of the millimeter-wave radar 11.

[0034] The signal conversion unit 40 converts the reflected radio wave signal acquired by the signal acquisition unit 30 into a complex signal (IQ data) by performing a signal conversion process (IQ conversion process). Specifically, the signal conversion unit 40 converts the reflected radio wave signal into an electrical signal (IQ data) containing an I signal and a Q signal by unfolding the reflected radio wave signal onto a complex plane (a vector plane with the horizontal axis as the I axis and the vertical axis as the Q axis).

[0035] The frequency conversion unit 50 calculates a frequency characteristic that represents the correspondence between the frequency components and intensity contained in the reflected wave by applying a frequency conversion process (Fast Fourier Transform (FFT)) to the electrical signal (IQ data) of the reflected wave for one chirp period each time a chirp period ends.

[0036] Figure 4 schematically illustrates the processing flow from the transmission of a chirp signal to the calculation of the frequency characteristics. Note that Figure 4 shows an example where three chirp signals are transmitted.

[0037] The chirp signal is transmitted at a predetermined period. Specifically, each chirp signal is transmitted after a predetermined frame period has elapsed. During the predetermined chirp period, the frequency of each chirp signal changes by a predetermined chirp width. For example, the center frequency of the chirp signal is set to approximately 60 GHz, and the chirp width is set to approximately 7000 MHz.

[0038] At the end of each chirp period, the frequency characteristics of the reflected wave are calculated by applying signal conversion processing (IQ conversion) and frequency conversion processing (FFT processing) to the reflected radio wave signal for one chirp period.

[0039] Figure 5 shows an example of the frequency characteristics of a reflected wave for one chirp period. The frequency characteristics graph shown in Figure 5 shows the relationship between frequency components and their intensities, with the horizontal axis representing the frequency components contained in the reflected wave and the vertical axis representing the intensity of each frequency component.

[0040] The horizontal axis of the frequency response graph, "frequency," corresponds to the distance from the millimeter-wave radar 11 to the reflection site, i.e., the reflection position. The "measurement site area" and "bed area" shown in Figure 2 above correspond to the "measurement site range" and "bed range" shown in Figure 5 in the frequency response graph. That is, the "measurement site range" shown in Figure 5 is the frequency range corresponding to the distance from the transmitter 11a of the millimeter-wave radar 11 to the measurement site of the person being cared for 17. The "bed range" shown in Figure 5 is the frequency range corresponding to the distance from the transmitter 11a of the millimeter-wave radar 11 to the bed 16, and is a frequency range that includes the "measurement site range" and is wider than the "measurement site range." The "measurement site range" and "bed range" are examples of the "first frequency range" and "second frequency range" of this disclosure, respectively.

[0041] Returning to Figure 3, the measurement position setting unit 60 sets a "vital sign measurement position" corresponding to the location of the measurement site of the person being cared for 17 each time the frequency characteristics are calculated by the frequency conversion unit 50. Note that the "vital sign measurement position" is an example of the "measurement target frequency" in this disclosure. The method for setting the vital sign measurement position will be described in detail below.

[0042] First, each time the frequency characteristics are calculated, the measurement position setting unit 60 uses the frequency characteristics to determine whether or not the person to be cared for 17 is on the bed 16.

[0043] Figure 6 illustrates an example of a method for determining whether or not a person receiving care 17 is on the bed 16. The measurement position setting unit 60 determines, in the frequency characteristic graph, whether or not there are frequency components with an intensity above a threshold in the aforementioned "bed range," and determines that a person receiving care 17 is on the bed 16 if there are frequency components with an intensity above a threshold in the bed range. The "bed range" is, as described above, an example of the "second frequency range" of this disclosure.

[0044] Furthermore, even if a stationary object other than a person is present on bed 16, it will be determined that there are frequency components with an intensity above the threshold within the bed range. However, stationary objects do not have the movement of lungs and heart like a person, and therefore no phase changes occur. In light of this, it may be possible to determine that a person receiving care 17 is on bed 16 if there are frequency components with an intensity above the threshold within the bed range, and the waveform of the frequency characteristics calculated this time has changed from the waveform of the frequency characteristics calculated last time. This will allow for a more appropriate determination of whether or not a person receiving care 17 is on bed 16.

[0045] If it is not determined that the person to be cared for 17 is on the bed 16, the measurement position setting unit 60 will not perform the subsequent processing (setting the vital sign measurement position and subsequent vital sign measurement). This prevents the subsequent processing from being performed unnecessarily even when the person to be cared for 17 is not on the bed 16.

[0046] On the other hand, if it is determined that the person receiving care 17 is on the bed 16, the measurement position setting unit 60 sets the vital sign measurement position using the following method.

[0047] Figure 7 is a diagram illustrating a method for setting vital sign measurement locations. The measurement location setting unit 60 searches for the component with the highest intensity within the "measurement site range" described above in the frequency characteristic graph and performs a identification process to identify the frequency of the found component with the highest intensity as the "maximum intensity location". The "measurement site range" is an example of the "first frequency range" in this disclosure, as described above. The "maximum intensity location" is an example of the "maximum intensity frequency" in this disclosure.

[0048] Thus, in this embodiment, the frequency range for searching for the maximum intensity component in a specific process is narrowed down to the "measurement site range" where the measurement site of the care recipient 17 can exist while the care recipient 17 is lying on the bed 16, rather than the entire frequency band of the frequency characteristics. Therefore, compared to the case where the search range for the maximum intensity component is the entire frequency band, it is no longer necessary to consider the intensity of frequency bands that are unnecessary for vital sign measurement, thus reducing the load and time required to search for the maximum intensity component. Furthermore, even if there is significant noise in frequency bands other than the measurement site range, the maximum intensity component is searched for after eliminating the influence of that noise, so the location of the maximum intensity can be identified with high accuracy, and consequently, the accuracy of vital sign measurement can be improved.

[0049] Once the maximum intensity position is identified, the measurement position setting unit 60 determines whether the identified maximum intensity position deviates from the current vital sign measurement position (i.e., the previously set vital sign measurement position). Specifically, the measurement position setting unit 60 determines whether the difference between the maximum intensity position and the current vital sign measurement position is greater than or equal to a predetermined allowable value.

[0050] If the difference between the maximum intensity position and the current vital sign measurement position is less than the allowable value, the person being cared for 17 has not moved much from the time the vital sign measurement position was last set, and it is highly likely that the accuracy of vital sign measurement will be ensured even if the current vital sign measurement position is maintained. Based on this, the measurement position setting unit 60 maintains the current vital sign measurement position without changing it (i.e., sets the current vital sign measurement position as the vital sign measurement position) if the difference between the maximum intensity position and the current vital sign measurement position is less than the allowable value.

[0051] On the other hand, if the difference between the maximum intensity position and the current vital sign measurement position exceeds the allowable value, it is highly likely that the vital sign measurement position of the person being cared for 17 has moved considerably since the last time it was set, and that maintaining the current vital sign measurement position would make it impossible to ensure the accuracy of vital sign measurement. Taking this into consideration, if the difference between the maximum intensity position and the current vital sign measurement position exceeds the allowable value, the measurement position setting unit 60 discards the current vital sign measurement position and sets a new vital sign measurement position. Specifically, the measurement position setting unit 60 sets the frequency of the component other than the current vital sign measurement position that has been identified as the maximum intensity position most frequently to the new vital sign measurement position. This allows vital sign measurement to be performed at a higher intensity frequency, thus enabling more accurate vital sign measurement.

[0052] Thus, in this embodiment, each time it is determined that a person receiving care 17 is on the bed 16, the position of maximum intensity is identified by a specific process, and it is determined whether the difference between the position of maximum intensity and the current vital sign measurement position is greater than or equal to an acceptable value.

[0053] If the difference between the maximum intensity position and the current vital sign measurement position exceeds a certain limit, the vital sign measurement position is reset. This allows for immediate commencement of measurements at the new vital sign measurement position.

[0054] On the other hand, if the difference between the maximum intensity position and the current vital sign measurement position is less than the allowable value, the current vital sign measurement position is maintained. This allows for more effective use of the phase data (described later) of the current vital sign measurement position compared to changing the vital sign measurement position even with a slight change in the maximum intensity position, thereby reducing the burden and time required for vital sign measurement.

[0055] Returning to Figure 3, the phase data acquisition unit 70 collects time-series phase data of the current vital sign measurement location and stores it in memory. When a predetermined period of time-series phase data for the current vital sign measurement location has been accumulated, it notifies the vital sign measurement unit 80 of this. Here, the "predetermined period" is a continuous period, and its length is set in advance to a length that allows for the measurement of the care recipient 17's heart rate and respiratory rate from the phase change of the vital sign measurement location (specifically, a period longer than the cycle of a person's heartbeat and respiratory cycle, for example, about 20 seconds).

[0056] When the vital signs measurement unit 80 receives notification from the phase data collection unit 70 that phase data for a predetermined period has been accumulated at the current vital signs measurement location, it measures the heart rate and respiratory rate of the person being cared for 17 based on the phase data for that predetermined period.

[0057] Figure 8 is a diagram illustrating the method for measuring the heart rate and respiratory rate of the care recipient 17. The vital signs measurement unit 80 calculates the frequency characteristics of the phase at the current vital signs measurement location by applying frequency transformation processing (FFT processing) to the phase data for a predetermined period at the current vital signs measurement location.

[0058] The vital signs measurement unit 80 then measures the respiratory rate and heart rate of the person being cared for 17 using the frequency characteristics of the phase of the current vital signs measurement location. Specifically, as shown in the lower part of Figure 8, the vital signs measurement unit 80 measures the respiratory rate from the frequency of the component with the maximum intensity within a predetermined respiratory frequency range, and measures the heart rate from the frequency of the component with the maximum intensity within a predetermined heart rate frequency range, among the frequency components of the phase of the vital signs measurement location.

[0059] The vital signs measurement unit 80 transmits the results of the vital signs measurement of the person being cared for 17 to the aforementioned communication terminals 3 to 5 via the communication device 14. This allows the caregiver to remotely check the results of the vital signs measurement of the person being cared for 17 in real time.

[0060] Furthermore, each time vital sign measurement is completed at the current vital sign measurement location, the vital sign measurement unit 80 notifies the measurement location setting unit 60 that the vital sign measurement is complete.

[0061] Each time the measurement position setting unit 60 receives notification from the vital sign measurement unit 80 that vital sign measurement is complete, it resets the vital sign measurement position. Specifically, the measurement position setting unit 60 resets the vital sign measurement position to the frequency that has been most frequently identified as the maximum intensity position to date. This allows the next vital sign measurement to be performed at a higher intensity frequency, thus enabling more accurate vital sign measurements. In other words, until vital sign measurement is complete, it is desirable to maintain the current vital sign measurement position as much as possible in order to quickly accumulate phase data for a predetermined period of time at the current vital sign measurement position. However, once vital sign measurement is complete, the phase data accumulated so far becomes unnecessary, and the collection of phase data for the next vital sign measurement position begins from the beginning. In light of this, the measurement position setting unit 60 resets the vital sign measurement position to the frequency that has been most frequently identified as the maximum intensity position at the moment vital sign measurement is complete. This allows the next vital sign measurement to be performed at a higher intensity frequency, thus enabling more accurate vital sign measurements.

[0062] Figure 9 is a flowchart showing an example of the processing procedure performed by the control device 13 when performing vital sign measurement. In this flowchart, the process from the start is repeated each time the process moves to the return step.

[0063] First, the control device 13 determines whether or not the chirp period for transmitting the chirp signal has started (step S10). If the chirp period has not started (NO in step S10), the control device 13 does not perform any further processing and returns to the return state.

[0064] On the other hand, if the chirp period is initiated (YES in step S10), the control device 13 acquires the radio signal of the reflected chirp signal and converts the reflected radio signal into a complex signal (step S12). The complex signal of the reflected wave is stored in memory.

[0065] Next, the control device 13 determines whether the chirp period has ended (step S14). If the chirp period is still ongoing (NO in step S14), the control device 13 returns to step S12 and repeats the processes in steps S12 and S14 until the chirp period ends.

[0066] If the chirp period ends (NO in step S14), the control device 13 performs a frequency transformation (FFT) on the complex signal of the reflected wave for the current chirp period stored in memory to calculate the frequency characteristics of the reflected wave for that chirp period (see Figure 5) (step S16).

[0067] Next, the control device 13 uses the frequency characteristics calculated in step S16 to determine whether or not the person to be cared for 17 is on the bed 16 (step S20). The method for determining whether or not the person to be cared for 17 is on the bed 16 is as explained using Figure 6 above. If it is determined that the person to be cared for 17 is not on the bed 16 (NO in step S20), the control device 13 does not perform any further processing and returns to the return state.

[0068] If it is determined that a person receiving care 17 is on the bed 16 (YES in step S20), the control device 13 performs a determination process to identify the location of maximum intensity using the frequency characteristics calculated in step S16 (step S30). The method for determining the location of maximum intensity is as described above using Figure 7.

[0069] Next, the control device 13 increments the maximum frequency counter of the maximum intensity position identified in step S30 by 1 (step S32). The maximum frequency counter is set for each frequency included in the measurement area range (more specifically, for each minute width obtained by dividing the measurement area range into a predetermined number of equal parts), and is an index that shows how often each frequency has been identified as the maximum intensity position in step S30 up to the present.

[0070] Next, the control device 13 determines whether a positional misalignment has occurred, where the maximum intensity position identified in step S30 is offset from the current vital sign measurement position (step S34). Specifically, as described above, the control device 13 determines that a positional misalignment has occurred if the difference between the maximum intensity position and the current vital sign measurement position is greater than or equal to a predetermined allowable value.

[0071] If no positional misalignment has occurred (NO in step S34), the control device 13 clears the positional misalignment counter for the current vital sign measurement position (step S36) and maintains the current vital sign measurement position without changing it (step S38). The positional misalignment counter is an indicator that shows the number of times a positional misalignment has been determined to have occurred at the current vital sign measurement position.

[0072] On the other hand, if a misalignment occurs (YES in step S34), the control device 13 increments the misalignment counter by 1 (step S60) and determines whether the misalignment counter has exceeded a predetermined number of times (step S62).

[0073] If the positional displacement counter exceeds a predetermined number of times (YES in step S62), it is assumed that the cause of the positional displacement is the movement of the person being cared for 17 and not noise, so the control device 13 discards all of the current vital sign measurement position and its phase data (step S64). Then, the control device 13 changes the vital sign measurement position (step S66). Specifically, the control device 13 sets the new vital sign measurement position to a frequency other than the current vital sign measurement position, and which has the highest maximum frequency counter (i.e., the frequency that has been identified as the highest intensity position most frequently to date). After setting the new vital sign measurement position, the control device 13 does not perform any further processing and moves the process to return.

[0074] On the other hand, if the positional displacement counter has not exceeded a predetermined number of times (NO in step S62), the control device 13 maintains the current vital sign measurement position because the cause of the positional displacement may be noise (step S38).

[0075] If the current vital sign measurement position is maintained in step S38, the control device 13 determines whether or not time-series phase data for a predetermined period of time at the current vital sign measurement position has been collected (step S40).

[0076] If time-series phase data for a predetermined period at the current vital sign measurement location has not been collected (NO in step S40), the control device 13 will return to the return state without performing any further processing because there is still insufficient phase data to perform vital sign measurement.

[0077] When time-series phase data for a predetermined period has been collected at the current vital sign measurement location (YES in step S40), the control device 13 calculates the frequency characteristics of the phase at the current vital sign measurement location by performing a frequency transformation (FFT) on the time-series phase data for the predetermined period at the current vital sign measurement location (step S42). Then, the control device 13 measures the respiratory rate and heart rate of the person being cared for 17 using the frequency characteristics of the phase calculated in step S42 (step S44). The specific measurement method for respiratory rate and heart rate is as explained using Figure 8 above. The respiratory rate and heart rate measured in step S44 are transmitted to the respective communication terminals 3 to 5 via the communication device 14.

[0078] After measuring the respiratory rate and heart rate in step S44, the control device 13 resets the vital sign measurement position (step S50). Specifically, as described above, the control device 13 resets the maximum frequency counter to the highest frequency (i.e., the frequency at which the highest intensity position has been identified most frequently to date).

[0079] As described above, the control device 13 according to this embodiment calculates the frequency characteristics of the reflected wave each time the chirp period ends, searches for the maximum intensity component within the measurement area range (frequency range corresponding to the measurement area region) in the frequency characteristics, and performs a determination process to identify the frequency of the found maximum intensity component as the maximum intensity position. This makes it possible to improve the accuracy of vital sign measurement while reducing the load and time required for determination processing. In other words, by narrowing the search range for the maximum intensity component in the determination process to the measurement area range, it becomes unnecessary to consider the intensity of frequency bands other than the measurement area range (i.e., frequency bands unnecessary for vital sign measurement) compared to when the search range for the maximum intensity component is the entire frequency band, thus reducing the load and time required to search for the maximum intensity component. Furthermore, even if there is significant noise in frequency bands other than the measurement area range, the maximum intensity component is searched for after eliminating the influence of that noise, so the maximum intensity position can be determined with high accuracy, and consequently, the accuracy of vital sign measurement can be improved.

[0080] Furthermore, when the maximum intensity position is identified, the control device 13 according to this embodiment determines whether the difference between the maximum intensity position and the current vital sign measurement position is greater than or equal to an allowable value. If the difference between the maximum intensity position and the current vital sign measurement position is less than the allowable value, the current vital sign measurement position is maintained. If the difference between the maximum intensity position and the current vital sign measurement position is greater than or equal to an allowable value, the current vital sign measurement position is discarded and the vital sign measurement position is reset.

[0081] Therefore, if the position of maximum intensity changes significantly from the current vital sign measurement position, the current vital sign measurement position and its phase data are discarded, and a new vital sign measurement position is set, even if a predetermined period has not elapsed since the current vital sign measurement position was set. This prevents the continued and unnecessary collection of phase data at the current vital sign measurement position and allows for the immediate commencement of phase data collection at the new vital sign measurement position. On the other hand, if the position of maximum intensity does not change significantly from the current vital sign measurement position, the current vital sign measurement position is maintained. This allows for effective utilization of the phase data collected so far at the current vital sign measurement position, reducing the burden and time required for vital sign measurement.

[0082] As a result of the above, the biological state measurement device 10 according to this embodiment can ensure vital sign measurement accuracy while suppressing an increase in the load and time required for vital sign measurement.

[0083] Furthermore, the control device 13 according to this embodiment determines whether or not there are components with an intensity above a threshold within the bed range (frequency range corresponding to the bed area) in the frequency characteristics before executing the processing after the specific processing. If there are no components with an intensity above a threshold within the bed range, the control device does not execute the processing after the specific processing. This makes it possible to avoid the unnecessary setting of the vital sign measurement position and subsequent vital sign measurement even when there is no care recipient 17 on the bed 16.

[0084] Furthermore, the control device 13 in this embodiment resets the vital sign measurement position to the frequency component with the highest maximum frequency counter (the frequency that has been identified as the highest intensity position to date) each time a vital sign measurement is completed. This allows the next vital sign measurement to be performed at a higher intensity frequency, thus enabling more accurate vital sign measurements.

[0085] [Pattern] Those skilled in the art will understand that the embodiments described above are specific examples of the following embodiments.

[0086] (Section 1) The biological state measuring device according to the present disclosure is a biological state measuring device for measuring the biological state of a target, comprising: a transmitting unit that transmits a chirp signal whose frequency changes during the chirp period at a predetermined period; a receiving unit that receives a reflected wave generated when the chirp signal is reflected by the target; and a control device that measures the biological state of the target based on the phase change of the measurement target frequency in the reflected wave. The control device calculates a frequency characteristic representing the correspondence between the frequency components and intensity of the reflected wave for one chirp period each time the chirp period ends, searches for the component with the maximum intensity within a first frequency range corresponding to the position range of the measurement site of the target in the frequency characteristic, performs a identification process that identifies the frequency of the searched component with the maximum intensity as the maximum intensity frequency, maintains the current measurement target frequency if the difference between the maximum intensity frequency and the current measurement target frequency is less than an allowable value, and discards the current measurement target frequency and resets the measurement target frequency if the difference between the maximum intensity frequency and the current measurement target frequency is greater than or equal to an allowable value.

[0087] According to the biological state measurement device described in paragraph 1, in the identification process for determining the maximum intensity frequency, the range for searching for the maximum intensity component is narrowed to a first frequency range corresponding to the positional range of the measurement site, rather than the entire frequency range of the frequency characteristics. Therefore, the load and time required to search for the maximum intensity component can be reduced compared to searching the entire frequency range of the frequency characteristics. Furthermore, even if there is significant noise in frequency bands other than the first frequency range, the maximum intensity component can be searched after eliminating the influence of that noise, thereby enabling accurate identification of the maximum intensity frequency and ultimately improving the accuracy of biological state measurement.

[0088] Furthermore, according to the biological state measurement device described in paragraph 1, it is determined whether the difference between the identified maximum intensity frequency and the current measurement target frequency is greater than or equal to an acceptable value. If the difference is less than the acceptable value, the current measurement target frequency is maintained; if the difference is greater than or equal to the acceptable value, the current measurement target frequency is discarded and the measurement target frequency is reset. This allows for immediate commencement of phase data collection at the new measurement target frequency if the identified maximum intensity frequency deviates significantly from the current measurement target frequency. On the other hand, if the maximum intensity frequency does not deviate significantly from the current measurement target frequency, the phase data collected so far at the current measurement target frequency can be effectively utilized, reducing the burden and time required for measuring the biological state.

[0089] As a result of the above, the biological state measurement device according to this embodiment can ensure the accuracy of measuring the biological state while suppressing an increase in the load and time required for measuring the biological state.

[0090] (Paragraph 2) In the biological state measuring device described in Paragraph 1, the control device maintains the current measurement target frequency, determines whether or not phase data for a predetermined period of the current measurement target frequency has been collected, and if phase data for a predetermined period of the current measurement target frequency has been collected, measures the biological state of the target based on the phase data for the predetermined period that has been collected.

[0091] According to the biological state measuring device described in paragraph 2, the biological state of the subject can be measured based on phase data for a predetermined period collected at the current measurement target frequency.

[0092] (Article 3) In the biological state measuring device described in Article 1, if the control device discards the current measurement target frequency, it sets the frequency of the frequency component that is other than the current measurement target frequency and has been most frequently identified as the maximum intensity frequency to date as the new measurement target frequency.

[0093] According to the biological state measurement device described in paragraph 3, if the current measurement target frequency is discarded, a frequency with a higher intensity than the current measurement target frequency is set as the new measurement target frequency. This allows the biological state to be measured based on the phase change of the higher intensity measurement target frequency, thus enabling more accurate measurement of the biological state.

[0094] (Article 4) In the biological state measuring device described in Article 1, the control device determines, before executing the processing after the specified processing, whether or not there are components with an intensity of a threshold or higher in the second frequency range of the frequency characteristics, which includes the first frequency range and is wider than the first frequency range. If there are components with an intensity of a threshold or higher in the second frequency range, the control device executes the processing after the specified processing. If there are no components with an intensity of a threshold or higher in the second frequency range, the control device does not execute the processing after the specified processing.

[0095] According to the biological state measuring device described in paragraph 4, if there are no components with an intensity above a threshold within a second frequency range that includes the first frequency range and is wider than the first frequency range, the processing after the specified processing will not be performed. This prevents the processing after the specified processing from being performed unnecessarily even when the subject is not within the second frequency range.

[0096] (Clause 5) In the biological state measuring device described in paragraph 2, the control device resets the measurement target frequency to the frequency that has been identified as having the highest intensity frequency to date each time the biological state of the target is measured.

[0097] According to the biological state measurement device described in paragraph 5, each time the biological state of the subject is measured, the measurement target frequency is reset to a frequency with an intensity greater than or equal to the intensity of the current measurement target frequency. This allows the next biological state to be measured at a higher intensity frequency, thus enabling more accurate measurement of the biological state.

[0098] (Section 6) The method for measuring the biological state according to the present disclosure is a method for measuring the biological state of a target, and includes the steps of: transmitting a chirp signal whose frequency changes during a chirp period at a predetermined period; receiving a reflected wave generated when the chirp signal is reflected by the target; and measuring the biological state of the target based on the phase change of the measurement target frequency in the reflected wave. The step of measuring the biological state includes: calculating a frequency characteristic that represents the correspondence between the frequency components and intensity of the reflected wave for one chirp period each time a chirp period ends; performing a identification process that searches for the component with the maximum intensity within a first frequency range corresponding to the position range of the measurement site of the target in the frequency characteristic, and identifies the frequency of the searched component with the maximum intensity as the maximum intensity frequency; maintaining the current measurement target frequency if the difference between the maximum intensity frequency and the current measurement target frequency is less than an allowable value; and discarding the current measurement target frequency and resetting the measurement target frequency if the difference between the maximum intensity frequency and the current measurement target frequency is greater than or equal to an allowable value.

[0099] The method for measuring the biological state described in paragraph 6 can produce the same effects as the biological state measuring device described in paragraph 1.

[0100] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of Symbols]

[0101] 1. Biological monitoring system, 2. Network, 3. Personal computer, 4. Smartphone, 5. Tablet, 10. Biological condition measurement device, 11. Millimeter-wave radar, 11a. Transmitter, 11b. Receiver, 11c. Signal generation unit, 12. Camera, 13. Control device, 14. Communication device, 15. Irradiation range, 15a. Reflected wave, 16. Bed, 16a. Headboard, 17. Person receiving care, 30. Signal acquisition unit, 40. Signal conversion unit, 50. Frequency conversion unit, 60. Measurement position setting unit, 70. Phase data acquisition unit, 80. Vital sign measurement unit.

Claims

1. A biological state measuring device for measuring the biological state of a subject, A transmitting unit that transmits a chirp signal whose frequency changes during the chirp period at a predetermined interval, A receiving unit that receives the reflected wave generated when the chirp signal is reflected by the object, The system includes a control device that measures the biological state of the target based on the phase change of the frequency to be measured in the reflected wave, The control device is Each time the aforementioned chirp period ends, a frequency characteristic representing the correspondence between the frequency components and intensity of the reflected wave for one chirp period is calculated. The process involves searching for the component with the highest intensity within a first frequency range corresponding to the positional range of the measurement site in the frequency characteristics, and identifying the frequency of the found component with the highest intensity as the maximum intensity frequency. If the difference between the maximum intensity frequency and the current measurement target frequency is less than the allowable value, the current measurement target frequency will be maintained. A biological state measuring device that, if the difference between the maximum intensity frequency and the current measurement target frequency is greater than or equal to the allowable value, discards the current measurement target frequency and resets the measurement target frequency.

2. When the control device maintains the current measurement target frequency, Determine whether or not phase data for a predetermined period of the current measurement target frequency has been collected. The biological state measuring device according to claim 1, wherein when phase data for a predetermined period of the current measurement target frequency is collected, the biological state of the target is measured based on the collected phase data for the predetermined period.

3. The biological state measuring device according to claim 1, wherein when the control device discards the current measurement target frequency, it sets a frequency other than the current measurement target frequency, which is the frequency component that has been most frequently found to be the maximum intensity frequency to date, as the new measurement target frequency.

4. The control device is Before executing the processing after the specified processing, it is determined whether there are components with an intensity of above a threshold in the second frequency range of the frequency characteristics, which includes the first frequency range and is wider than the first frequency range. If a component with an intensity equal to or greater than the threshold exists in the second frequency range, the processes after the specified process are executed. The biological state measuring device according to claim 1, wherein if there are no components with an intensity equal to or greater than the threshold in the second frequency range, the processing after the specific processing is not performed.

5. The biological state measuring device according to claim 2, wherein the control device readjusts the measurement target frequency each time the biological state of the target is measured to the frequency that has been identified as having the highest intensity frequency to date.

6. A method for measuring the biological state of a subject, The steps include transmitting a chirp signal whose frequency changes during the chirp period at a predetermined interval, The steps include receiving the reflected wave generated when the chirp signal is reflected by the object, The step includes measuring the biological state of the object based on the phase change of the frequency to be measured in the reflected wave, The step of measuring the aforementioned biological state is: Each time the aforementioned chirp period ends, a step is to calculate a frequency characteristic representing the correspondence between the frequency components and intensity of the reflected wave for one chirp period. The process involves searching for the component with the highest intensity within a first frequency range corresponding to the positional range of the measurement site in the frequency characteristics, and performing a determination process to identify the frequency of the found component with the highest intensity as the maximum intensity frequency. If the difference between the maximum intensity frequency and the current measurement target frequency is less than an acceptable value, the step is to maintain the current measurement target frequency. A method for measuring a biological state, comprising the step of discarding the current target frequency and resetting the target frequency if the difference between the maximum intensity frequency and the current target frequency is greater than or equal to the allowable value.

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