Presence / absence determination control system, presence / absence determination control method, and program

Abstract

Provided are a presence / absence determination control system, a presence / absence determination control method, and a program which are capable of appropriately controlling the execution of a presence / absence determination processing. A presence / absence determination processing execution unit (34) repeatedly executes a presence / absence determination processing for determining whether or not a subject to be measured is on a mattress placed on the bed frame of a bed used by the subject to be measured, on the basis of the result of measuring the load applied to at least one load sensor supporting the bed frame. In a case where the presence / absence determination processing is being executed, a presence / absence determination control unit (36) stops the execution of the presence / absence determination processing when the result of a comparison between a total weight calculated on the basis of the load applied to the at least one load sensor and a given bed frame weight value indicating the weight of the bed frame satisfies a given mattress removal condition.

Description

Presence / absence determination control system, presence / absence determination control method and program

[0001] The present invention relates to a presence / absence determination control system, a presence / absence determination control method, and a program.

[0002] Various systems for measuring biological information such as the respiratory rate or heart rate of a person in bed have been studied. As an example of such a system, Patent Literature 1 describes a monitoring device that determines the respiratory rate and heart rate of a person in bed in a non-contact manner using a microwave Doppler sensor.

[0003] JP 2017-134795 A

[0004] In the technology described in Patent Document 1, when the respiratory rate or heart rate of the person being measured indicates an abnormal value, it is not possible to determine whether the cause is that an abnormality has occurred in the person being measured or that the person being measured is not present in bed. Therefore, in order to accurately detect that an abnormality has occurred in the person being measured, it is necessary to accurately perform a process to determine whether the person being measured is present in bed (hereinafter referred to as a presence / absence determination process).

[0005] Here, when a presence / absence determination process is being performed based on the total weight calculated based on the load applied to the load sensor supporting the bed, if the mattress placed on the bed frame of the bed is removed or replaced with another mattress of a different weight, it is no longer possible to properly determine whether or not the person being measured is on the bed.

[0006] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a presence / absence determination control system, a presence / absence determination control method, and a program that can appropriately control the execution of presence / absence determination processing.

[0007] (1) The presence / absence determination control system of the present invention includes a presence / absence determination process execution means that repeatedly executes a presence / absence determination process to determine whether the person being measured is on a mattress placed on the bed frame based on the measurement results of the load applied to at least one load sensor supporting the bed frame of the bed used by the person being measured, and a presence / absence determination stop means that stops the execution of the presence / absence determination process when, while the presence / absence determination process is being executed, the comparison result between the total weight calculated based on the load applied to the at least one load sensor and a given bed frame weight value indicating the weight of the bed frame satisfies a given mattress removal condition.

[0008] (2) The presence / absence determination control system described in (1) may further include a presence / absence determination restart means for restarting the execution of the presence / absence determination process in response to a given mattress placement condition being satisfied when execution of the presence / absence determination process is stopped.

[0009] (3) In the presence / absence determination control system described in (2), the mattress placement condition may be a condition related to the magnitude of the load applied to the load sensor.

[0010] (4) In the presence / absence determination control system described in (2) or (3), the mattress placement condition may be a condition related to the smallness of variation in the loads applied to the multiple load sensors.

[0011] (5) In the presence / absence determination control system described in any of (2) to (4), the mattress placement condition may be a condition related to the small variation in the results of the most recent multiple measurements of the load applied to the load sensor.

[0012] (6) In the presence / absence determination control system described in any one of (2) to (5), the presence / absence determination process execution means includes a total weight data acquisition means for acquiring total weight data indicating a total weight calculated based on a load applied to at least one of the load sensors, a presence / absence information storage means for storing presence / absence information indicating whether the person being measured is on the mattress, and a presence / absence information storage means for storing presence / absence information indicating whether the person being measured is on the mattress when the presence / absence information indicates that the person being measured is not on the mattress and the magnitude of the increase, which is the value indicated by the total weight data based on the latest measurement result minus the value indicated by the total weight data based on the immediately preceding measurement result, satisfies a given presence determination condition. and an absence change means, when the presence / absence information indicates that the person being measured is on the mattress and the magnitude of the decrease, which is the value indicated by the total weight data based on the most recent measurement result minus the value indicated by the total weight data based on the most recent measurement result, satisfies a given absence determination condition, wherein in the presence / absence determination process immediately after resumption, the total weight data indicating the total weight calculated based on the load acting on the at least one load sensor when the mattress placement condition is satisfied may be used as the total weight data based on the most recent measurement result.

[0013] (7) In the presence / absence determination control system described in any one of (1) to (6), each of the four corners of the bed frame may be supported by the load sensor.

[0014] (8) In the presence / absence determination control system described in any of (1) to (7), the system may further include a Doppler data acquisition means for acquiring Doppler data indicating the measurement results by a Doppler sensor provided facing the person being measured, a biometric information generation means for generating biometric information of the person being measured based on the Doppler data, an action execution means for executing a given action in response to the biometric information satisfying a given abnormality determination condition, and a suppression means for suppressing the execution of the action in response to the biometric information satisfying the abnormality determination condition when it is determined that the person being measured is not on the mattress.

[0015] (9) The presence / absence determination control method of the present invention includes the steps of repeatedly executing a presence / absence determination process to determine whether the person being measured is on a mattress placed on a bed frame based on the measurement results of the load applied to at least one load sensor supporting the bed frame of the bed used by the person being measured, and stopping the execution of the presence / absence determination process when, while the presence / absence determination process is being executed, the comparison result between the total weight calculated based on the load applied to the at least one load sensor and a given bed frame weight value indicating the weight of the bed frame satisfies a given mattress removal condition.

[0016] (10) The program of the present invention causes a computer to execute the following steps: repeatedly executing a presence / absence determination process to determine whether the person being measured is on a mattress placed on the bed frame based on the measurement results of the load applied to at least one load sensor supporting the bed frame of the bed used by the person being measured; and stopping the execution of the presence / absence determination process when, while the presence / absence determination process is being executed, the comparison result between the total weight calculated based on the load applied to the at least one load sensor and a given bed frame weight value indicating the weight of the bed frame satisfies a given mattress removal condition.

[0017] According to the present invention, the execution of the presence / absence determination process can be appropriately controlled.

[0018] FIG. 1 is a configuration diagram of a biometric information detection system according to an embodiment of the present invention. FIG. 2 is a functional block diagram of a signal processing device according to an embodiment of the present invention. FIG. 3 is a functional block diagram of a presence / absence determination processing execution unit according to an embodiment of the present invention. FIG. 4 is a flow diagram showing an example of the flow of presence / absence determination processing performed in a signal processing device according to an embodiment of the present invention. FIG. 5 is a flow diagram showing an example of the flow of presence / absence determination processing performed in a signal processing device according to an embodiment of the present invention. FIG. 6 is a flow diagram showing an example of the flow of presence / absence determination control processing performed in a signal processing device according to an embodiment of the present invention. FIG. 7 is a diagram explaining an example of processing in a Doppler data acquisition unit. FIG. 8 is a flow diagram showing an example of the flow of frequency spectrum selection processing performed in a signal processing device according to an embodiment of the present invention. FIG. 9 is a diagram schematically showing an example of aggregate spectrum generation.

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0020] FIG. 1 is a configuration diagram of a biometric information detection system 1 according to an embodiment of the present invention. As shown in the figure, the biometric information detection system 1 includes a signal processing device 10, a Doppler sensor unit 12, and a plurality of load sensors 14. The Doppler sensor unit 12 includes a plurality of Doppler sensors. Here, for example, it is assumed that the Doppler sensor unit 12 includes six Doppler sensors (first to sixth Doppler sensors). Furthermore, as shown in FIG. 1, it is assumed that the biometric information detection system 1 includes four load sensors 14 (14a to 14d).

[0021] In this embodiment, for example, the bed 16 used by the subject includes a bed frame 18 and a mattress 20. The subject sleeps on the mattress 20 placed on the bed frame 18. In this embodiment, the bed frame 18 of the bed 16 used by the subject is supported by a load sensor 14. As shown in FIG. 1 , each of the four corners of the bed frame 18 may be supported by a load sensor 14. Furthermore, four load sensors 14 are supported by a bed stand 22. Each load sensor 14 outputs load data indicating the measurement result of the load applied to that load sensor 14. Note that the positions and number of load sensors 14 are not limited to those shown in FIG. 1 . For example, the biological information detection system 1 may include only one load sensor 14.

[0022] As shown in Fig. 1, the Doppler sensor unit 12 is provided facing the subject. In the example of Fig. 1, the Doppler sensor unit 12 is attached to the headboard of a bed frame 18. Here, multiple Doppler sensors may be provided symmetrically with respect to the center line of the bed 16 (a line passing through the center of the bed 16 in the width direction and extending in the length direction of the bed 16). Alternatively, multiple Doppler sensors may be provided lined up perpendicular to the length direction of the bed 16 (the direction along the center line of the bed 16). Alternatively, multiple Doppler sensors may be provided lined up at equal intervals in a row.

[0023] Each Doppler sensor is provided facing the length (longitudinal direction) of the bed 16 and emits microwaves in the lengthwise direction of the bed 16. The microwaves are reflected by the chest of the person being measured sleeping on the bed 16, and the reflected waves are received by each Doppler sensor. Each Doppler sensor generates a Doppler signal from the reflected waves that indicates chest movement associated with breathing, and outputs Doppler data by digitizing this Doppler signal. The microwaves emitted from each Doppler sensor have slightly different frequencies, which prevents mutual interference.

[0024] The reflected wave is frequency shifted due to the Doppler effect, and by observing this, the breathing rate of the subject can be obtained. The reflected wave is detected by quadrature detection as a Doppler signal containing an I signal, which is an in-phase component with the transmitted wave, and a Q signal, which is a quadrature component, and output in digital form to the signal processing device 10. The Doppler signal input to the signal processing device 10 is time-series data, indicating the amplitude (I component and Q component) at each time.

[0025] The signal processing device 10 may be configured with a known computer including, for example, a CPU, memory, an input device, and a display. The signal processing device 10 generates the subject's respiration rate based on the Doppler signal output from the Doppler sensor. The signal processing device 10 also calculates the total weight based on the measurement results of the load applied by at least one load sensor 14, and generates total weight data indicating the calculated total weight.

[0026] 2A and 2B are functional block diagrams of a signal processing device 10 according to an embodiment of the present invention. As shown in FIG. 2A , the signal processing device 10 includes a weight data storage unit 30, a load data acquisition unit 32, a presence / absence determination process execution unit 34, a presence / absence determination control unit 36, a Doppler data acquisition unit 38, a frequency spectrum generation unit 40, a frequency spectrum selection unit 42, an aggregate spectrum generation unit 44, a biological information generation unit 46, an abnormality determination unit 48, an action execution unit 50, and a motion control unit 52. Also, as shown in FIG. 2B , the presence / absence determination process execution unit 34 includes a presence / absence information storage unit 60, a body movement information storage unit 62, a total weight data generation unit 64, a presence / absence determination unit 66, a presence / absence change unit 68, a body movement determination unit 70, and a weight data management unit 72. These functional blocks are implemented by executing a signal processing program in the signal processing device 10, which is a computer. This signal processing program may be stored in various computer-readable information storage media such as semiconductor memory and loaded from the media into the signal processing device 10. Alternatively, it may be downloaded to the signal processing device 10 via a data communication line such as the Internet.

[0027] The weight data storage unit 30 stores, for example, data indicating weight. In the following description, it is assumed that the weight data storage unit 30 stores subject weight data indicating the weight of the subject, absent total weight data indicating the total weight when the mattress 20 is placed on the bed frame 18 but the subject is not on the bed 16, and bed frame weight data indicating the weight of the bed frame 18. In the initial state, the subject weight data, absent total weight data, and bed frame weight data are set to given values. For example, a value indicating the subject's weight measured in advance may be set as the subject weight data value in the initial state. Alternatively, a value indicating the total weight of the bed frame 18, mattress 20, bedding, etc. measured in advance may be set as the absent total weight data value in the initial state. Alternatively, a value indicating the weight of the bed frame 18 measured in advance may be set as the bed frame weight data value in the initial state. Furthermore, unknown weight data, which will be described later, is also stored in the weight data storage unit 30.

[0028] The load data acquiring unit 32 acquires, for example, load data indicating the measurement results of the load acting on at least one load sensor 14 supporting the bed frame 18. Here, the load data output from each of the at least one load sensor 14 may be acquired.

[0029] In this embodiment, the presence / absence determination process execution unit 34 repeatedly executes a presence / absence determination process to determine whether the person being measured is on a mattress 20 placed on the bed frame 18, based on the measurement results of the load acting on at least one load sensor 14 supporting the bed frame 18 of the bed 16 used by the person being measured.

[0030] The presence / absence information storage unit 60 included in the presence / absence determination process execution unit 34 stores, for example, presence / absence information indicating whether the person being measured is on the mattress 20. Here, the presence / absence information may indicate whether the person being measured is on the mattress 20, whether they are not on the mattress 20, or whether it is unknown whether they are on the mattress 20. In the following description, the presence / absence information includes a user 1 presence flag and an unknown flag. A user 1 presence flag value of 1 and an unknown flag value of 0 correspond to the presence / absence information indicating that the person being measured is on the mattress 20. A user 1 presence flag value of 0 and an unknown flag value of 0 correspond to the presence / absence information indicating that the person being measured is not on the mattress 20. A user 1 presence flag value of 0 and an unknown flag value of 1 correspond to the presence / absence information indicating that it is unknown whether the person being measured is on the mattress 20.

[0031] The body movement information storage unit 62 included in the presence / absence determination process execution unit 34 stores, for example, body movement information indicating whether or not the subject is moving. In the following description, a value of 1 in the body movement information corresponds to the body movement information indicating that the subject is moving, and a value of 0 in the body movement information corresponds to the body movement information indicating that the subject is not moving.

[0032] The total weight data generating unit 64 included in the presence / absence determination process executing unit 34 calculates the total weight based on the load data acquired from at least one load sensor 14, and generates total weight data indicating the calculated total weight. If the biological information detection system 1 includes one load sensor 14, total weight data indicating the measurement results of the load acting on the load sensor 14 may be generated. Furthermore, if the biological information detection system 1 includes multiple load sensors 14, total weight data indicating the sum of the measurement results of the loads acting on the multiple load sensors 14 may be generated.

[0033] The presence / absence determination unit 66 included in the presence / absence determination processing execution unit 34 acquires, for example, the total weight data generated by the total weight data generation unit 64, and determines whether the person being measured is on the mattress 20 based on the acquired total weight data.

[0034] For example, when the presence / absence information indicates that the person being measured is not on the mattress 20, the presence / absence determination unit 66 determines whether the value obtained by subtracting the value indicated by the total weight data based on the immediately preceding measurement result from the value indicated by the total weight data based on the latest measurement result satisfies a given presence determination condition. In the following description, the value obtained by subtracting the value indicated by the total weight data based on the immediately preceding measurement result from the value indicated by the total weight data based on the latest measurement result will be referred to as the increase amount.

[0035] Here, the presence determination condition may be, for example, that the magnitude of the increase is greater than a threshold determined based on an estimated value of the subject's weight (for example, greater than a threshold that is 80% of the value of the subject's weight data).

[0036] Furthermore, for example, when the presence / absence information indicates that the person being measured is on the mattress 20, the presence / absence determination unit 66 determines whether the value obtained by subtracting the value indicated by the total weight data based on the most recent measurement result from the value indicated by the total weight data based on the most recent measurement result satisfies a given absence determination condition. In the following description, the value obtained by subtracting the value indicated by the total weight data based on the most recent measurement result from the value indicated by the total weight data based on the most recent measurement result will be referred to as the decrease amount.

[0037] Here, the absence determination condition may be, for example, that the magnitude of the decrease is greater than a threshold determined based on an estimated value of the subject's weight (for example, greater than a threshold that is 80% of the value of the subject's weight data).

[0038] In this embodiment, the load sensor 14 outputs load data indicating the latest measurement result of the load applied to the load sensor 14 to the signal processing device 10, generates total weight data based on the load data, and determines whether the person being measured is on the mattress 20 based on the total weight data (for example, at predetermined time intervals).

[0039] The presence / absence change unit 68 included in the presence / absence determination processing execution unit 34, for example, when the presence / absence information indicates that the person being measured is not on the mattress 20 and the magnitude of the above-mentioned increase satisfies a given presence determination condition, changes the presence / absence information held to indicate that the person being measured is on the mattress 20.

[0040] In addition, when the presence / absence information indicates that the person being measured is on the mattress 20 and the magnitude of the decrease described above satisfies a given absence determination condition, the presence / absence change unit 68 changes the presence / absence information being held to indicate that the person being measured is not on the mattress 20.

[0041] The threshold value in the presence determination condition and the threshold value in the absence determination condition may be the same or different.

[0042] The body movement determining unit 70 included in the presence / absence determining process executing unit 34 determines whether or not the subject is moving, for example, based on the magnitude of fluctuation in the value indicated by the total weight data. Here, for example, the body movement determining unit 70 may determine whether or not the subject is moving, each time a determination timing arrives that arrives at a time interval longer than the time interval at which the total weight data is generated.

[0043] Here, the period between two consecutive determination timings is referred to as a body movement determination period. The maximum or minimum value of the total weight data generated during a specific body movement determination period may be identified. The average value of the total weight data generated during the body movement determination period immediately preceding the specific body movement determination period may be identified. If the difference between the maximum value identified for the specific body movement determination period and the average value identified for the body movement determination period immediately preceding the specific body movement determination period is equal to or greater than a predetermined value, it may be determined that the subject's body movement has occurred during the body movement determination time. Furthermore, if the difference between the minimum value identified for the specific body movement determination period and the average value identified for the body movement determination period immediately preceding the specific body movement determination period is equal to or greater than a predetermined value, it may be determined that the subject's body movement has occurred during the body movement determination time. If neither of these conditions is met, it may be determined that the subject's body movement has not occurred during the body movement determination time. Note that the method for determining whether the subject's body movement has occurred is not limited to this method.

[0044] If the body movement determination unit 70 determines that the subject is moving, it may set the value of the body movement information stored in the body movement information storage unit 62 to 1, and if it determines that the subject is not moving, it may set the value of the body movement information stored in the body movement information storage unit 62 to 0.

[0045] The weight data management unit 72 included in the presence / absence determination process execution unit 34 determines, as an estimated value of the weight of the person being measured, the value obtained by subtracting the value of the total weight data when the presence / absence information indicates that the person being measured is not on the mattress 20 from the value of the total weight data when the presence / absence information indicates that the person being measured is on the mattress 20. Then, the weight data management unit 72 updates the person being measured's weight data stored in the weight data storage unit 30 to indicate the determined estimated value.

[0046] The weight data management unit 72 included in the presence / absence determination process execution unit 34 may update the estimated weight of the person being measured to the above-mentioned increase in weight in response to a change in the stored presence / absence information from indicating that the person being measured is not on the mattress 20 to indicating that the person being measured is on the mattress 20. Here, the weight data management unit 72 may, for example, update the person being measured's weight data stored in the weight data storage unit 30 to indicate the above-mentioned increase in weight. Furthermore, the weight data management unit 72 may update the total weight data when the person is not present stored in the weight data storage unit 30 to indicate the value indicated by the total weight data based on the most recent measurement result.

[0047] The presence / absence determination control unit 36 ​​controls, for example, whether or not the presence / absence determination process is executed by the presence / absence determination process execution unit 34. In this embodiment, as will be described below, when the presence / absence determination process is being executed by the presence / absence determination process execution unit 34, if the mattress 20 is removed from the bed frame 18, the execution of the presence / absence determination process is stopped. Also, when the presence / absence determination process execution unit 34 has stopped executing the presence / absence determination process, if a new mattress 20 is placed on the bed frame 18, the execution of the presence / absence determination process is resumed.

[0048] For example, in a situation where the presence / absence determination process is being executed by the presence / absence determination process execution unit 34, the presence / absence determination control unit 36 ​​stops the execution of the presence / absence determination process by the presence / absence determination process execution unit 34 in response to a comparison result between the total weight calculated based on the load on at least one load sensor 14 and a given bed frame weight value indicating the weight of the bed frame 18 satisfying a given mattress removal condition. Here, for example, in a situation where the presence / absence determination process is being executed by the presence / absence determination process execution unit 34, the presence / absence determination control unit 36 ​​may stop the execution of the presence / absence determination process by the presence / absence determination process execution unit 34 in response to a comparison result between the total weight calculated based on the load on at least one load sensor 14 and the value of the bed frame weight data stored in the weight data storage unit 30 satisfying a given mattress removal condition.

[0049] In this embodiment, it is desirable to set the mattress removal condition as a condition that is satisfied when the mattress 20 is removed from the bed frame 18. For example, the mattress removal condition may be a condition related to the smallness of the difference between the total weight and the bed frame weight data. Alternatively, each time total weight data is generated, it may be determined whether the difference between the generated total weight data and the bed frame weight data is equal to or smaller than a predetermined value. The mattress removal condition may be a condition that the difference between the generated total weight data and the bed frame weight data is equal to or smaller than the predetermined value a predetermined number of times (e.g., three times) in succession.

[0050] In this embodiment, the presence / absence determination control unit 36 ​​may acquire the total weight data generated by the total weight data generation unit 64 and determine whether a given mattress removal condition is met based on the acquired total weight data. Also, in this embodiment, the presence / absence determination control unit 36 ​​may store the acquired total weight data. Then, the presence / absence determination control unit 36 ​​may determine whether a given mattress removal condition is met based on the history of the stored total weight data.

[0051] Furthermore, the presence / absence determination control unit 36 ​​may acquire load data acquired by the load data acquisition unit 32, and determine whether a given mattress removal condition is met based on the acquired load data. In this embodiment, the presence / absence determination control unit 36 ​​may also store the acquired load data. Then, the presence / absence determination control unit 36 ​​may determine whether a given mattress removal condition is met based on a history of the stored load data.

[0052] In addition, for example, in a situation where the execution of the presence / absence determination process by the presence / absence determination process execution unit 34 is stopped, the presence / absence determination control unit 36 ​​resumes the execution of the presence / absence determination process by the presence / absence determination process execution unit 34 in response to the satisfaction of a given mattress placement condition.

[0053] In this embodiment, it is desirable to set as the mattress placement condition a condition that is satisfied when the mattress 20 is placed on a bed frame 18 on which no mattress 20 is placed. For example, the mattress placement condition may be a condition related to the magnitude of the load applied to the load sensor 14. Alternatively, the mattress placement condition may be a condition related to the smallness of the variation in the loads applied to the multiple load sensors 14. Alternatively, the mattress placement condition may be a condition related to the smallness of the variation in the results of the most recent multiple measurements of the loads applied to the load sensors 14.

[0054] In this embodiment, the presence / absence determination control unit 36 ​​may acquire the total weight data generated by the total weight data generation unit 64 and determine whether a given mattress placement condition is met based on the acquired total weight data. Also, in this embodiment, the presence / absence determination control unit 36 ​​may store the acquired total weight data. Then, the presence / absence determination control unit 36 ​​may determine whether a given mattress placement condition is met based on a history of the stored total weight data.

[0055] Furthermore, the presence / absence determination control unit 36 ​​may acquire load data acquired by the load data acquisition unit 32, and determine whether or not a given mattress placement condition is met based on the acquired load data. In this embodiment, the presence / absence determination control unit 36 ​​may also store the acquired load data. Then, the presence / absence determination control unit 36 ​​may determine whether or not a given mattress placement condition is met based on a history of the stored load data.

[0056] The presence / absence determination control unit 36 ​​may also store a mattress removal flag. When the presence / absence determination process is being executed by the presence / absence determination process execution unit 34, the value of the mattress removal flag may be set to 0. When the presence / absence determination process execution unit 34 has stopped the execution of the presence / absence determination process, the value of the mattress removal flag may be set to 1.

[0057] When the mattress removal flag is set to 0, the presence / absence determination control unit 36 ​​may determine whether the comparison result with the value of the bed frame weight data satisfies a given mattress removal condition. When the mattress removal flag is set to 1, the presence / absence determination control unit 36 ​​may determine whether the comparison result with the value of the bed frame weight data satisfies a given mattress placement condition.

[0058] In the following explanation, it is assumed that in the initial state, a mattress 20 is placed on the bed frame 18, and the value of the mattress removal flag stored in the presence / absence determination control unit 36 ​​is set to 0.

[0059] In this embodiment, the load sensor 14 outputs load data indicating the latest measurement results of the load applied to the load sensor 14 to the signal processing device 10, and the presence / absence determination control unit 36 ​​makes the above-mentioned determination repeatedly (for example, at a predetermined time interval).

[0060] An example of the flow of the presence / absence determination process performed by the presence / absence determination process execution unit 34 will now be described with reference to the flowcharts shown in Figures 3 to 5. In the following description, the value of the subject weight data stored in the weight data storage unit 30 will be assumed to be A. Also, the value of the absent total weight data stored in the weight data storage unit 30 will be assumed to be B.

[0061] Figure 3 shows an example of the flow of the presence / absence determination process that is executed when the presence / absence information indicates that the person being measured is not in bed, i.e., when the value of the user 1 presence flag and the value of the unknown flag stored in the presence / absence information storage unit 60 are both 0.

[0062] In this case, the presence / absence determining unit 66 determines whether the increase is equal to or greater than (A×r1) (S101), where r1 is a given value, for example, 0.8.

[0063] If the increase is not equal to or greater than (A×r1) (S101: N), the process shown in this processing example is terminated.

[0064] If the increase is equal to or greater than (A×r1) (S101: Y), the presence / absence determination unit 66 determines whether the value of the total weight data based on the latest measurement result is equal to or greater than (A+B−d) and equal to or less than (A+B+d) (S102), where d is a given threshold value.

[0065] If the value of the total weight data based on the most recent measurement result is equal to or greater than (A+B-d) and equal to or less than (A+B+d) (S102: Y), the presence / absence changing unit 68 sets the value of the user 1 presence flag stored in the presence / absence information storage unit 60 to 1 (S103). Then, the weight data management unit 72 updates the subject's weight data stored in the weight data storage unit 30 to indicate the above-mentioned increase, and updates the absent total weight data stored in the weight data storage unit 30 to indicate the value indicated by the total weight data based on the most recent measurement result (S104), and the process shown in this processing example is terminated. That is, the above-mentioned increase is set as value A, and the value indicated by the total weight data based on the most recent measurement result is set as value B.

[0066] If the process shown in S102 determines that the value of the total weight data based on the latest measurement results is greater than or equal to (A+B-d) and not greater than (A+B+d) (S102: N), the presence / absence change unit 68 sets the value of the unknown flag to 1 (S105). Then, the weight data management unit 72 generates unknown weight data with a value indicating the above-mentioned increase set, and stores the generated unknown weight data in the weight data storage unit 30 (S106). Then, the process shown in this processing example ends. In the following explanation, the value of the unknown weight data is assumed to be C.

[0067] As explained with reference to Figure 3, the presence / absence change unit 68 may change the presence / absence information held to indicate that the person being measured is on the mattress 20 if the presence / absence information indicates that the person being measured is not on the mattress 20, the magnitude of the above-mentioned increase satisfies the presence determination condition, and the difference between the sum of the value of the person being measured's weight data and the value of the total weight data when not present and the value indicated by the total weight data based on the latest measurement result is within a given range.

[0068] Then, if the presence / absence information indicates that the person being measured is not on the mattress 20, the magnitude of the above-mentioned increase satisfies the presence determination condition, and the difference between the sum of the value of the person being measured's weight data and the value of the total weight data when not present, and the value indicated by the total weight data based on the latest measurement result is not within the range, the presence / absence change unit 68 may change the held presence / absence information to one indicating that it is unknown whether the person being measured is on the mattress 20 or not.

[0069] Figure 4 shows an example of the flow of the presence / absence determination process that is executed when the presence / absence information indicates that the person being measured is in bed, i.e., when the value of the user 1 presence flag stored in the presence / absence information storage unit 60 is 1 and the value of the unknown flag is 0.

[0070] In this case, the presence / absence determination unit 66 determines whether the aforementioned decrease is equal to or greater than (A×r2) (S201), where r2 is a given value, e.g., 0.8. The value r2 may be the same as or different from the value r1.

[0071] If the decrease amount is not equal to or greater than (A×r2) (S201: N), the process shown in this processing example is terminated.

[0072] If the decrease is greater than or equal to (A x r2) (S201: Y), the presence / absence change unit 68 sets the value of the user 1 presence flag stored in the presence / absence information storage unit 60 to 0, and the processing shown in this processing example is terminated.

[0073] Figure 5 shows an example of the flow of the presence / absence determination process that is executed when the presence / absence information indicates that it is unknown whether the person being measured is in bed, i.e., when the value of the user 1 presence flag stored in the presence / absence information storage unit 60 is 0 and the value of the unknown flag is 1.

[0074] In this case, the presence / absence determination unit 66 determines whether the aforementioned decrease is equal to or greater than (C×r3) (S301). Here, r3 is a given value, for example, 0.8. The value r3 may be the same as or different from the value r1. The value r3 may also be the same as or different from the value r2.

[0075] If the decrease amount is not equal to or greater than (C×r3) (S301: N), the process shown in this processing example is terminated.

[0076] If the decrease is equal to or greater than (C×r3) (S301: Y), the presence / absence changing unit 68 sets the value of the unknown flag stored in the presence / absence information storage unit 60 to 0 (S302). Then, the weight data management unit 72 deletes the unknown weight data stored in the weight data storage unit 30 (S303), and the process shown in this processing example is terminated.

[0077] Next, an example of the flow of the presence / absence determination control process performed by the presence / absence determination control unit 36 ​​will be described with reference to the flow charts shown in Figures 6 and 7. In the following description, it is assumed that the value of the bed frame weight data stored in the weight data storage unit 30 is D. It is also assumed that the presence / absence determination control unit 36 ​​holds the mattress removal flag described above. It is also assumed that the value of the absent total weight data stored in the weight data storage unit 30 is B, as described above.

[0078] In the following description, it is assumed that the presence / absence determination control unit 36 ​​holds data on the number of removal determinations. In the initial state, it is assumed that the value of the data on the number of removal determinations held by the presence / absence determination control unit 36 ​​is set to 0. It is also assumed that the presence / absence determination control unit 36 ​​holds a history of load data indicating the results of load measurement by each load sensor 14.

[0079] Figure 6 is a diagram showing an example of the flow of the presence / absence determination control process executed when the presence / absence determination process shown in Figures 3 to 5 is being executed, i.e., when the value of the mattress removal flag held in the presence / absence determination control unit 36 ​​is 0.

[0080] The presence / absence determination control unit 36 ​​determines whether the value of the total weight data based on the latest measurement result is equal to or less than (D+p1) (S401), where p1 is a given threshold value.

[0081] If the value of the total weight data based on the latest measurement results is not less than (D+p1) (S401: N), the presence / absence determination control unit 36 ​​sets the value of the removal determination count data held by the presence / absence determination control unit 36 ​​to 0 (S402), and the processing shown in this processing example is terminated.

[0082] If the value of the total weight data based on the latest measurement results is less than or equal to (D+p1) (S401Y), the presence / absence determination control unit 36 ​​increases the value of the removal determination count data held by the presence / absence determination control unit 36 ​​by 1 (S403).

[0083] Then, the presence / absence determination control unit 36 ​​checks whether the value of the removal determination count data has reached a predetermined value X (for example, 3) (S404).

[0084] If the value of the removal determination count data has not reached X (S404: N), the process shown in this processing example is terminated.

[0085] If the value of the removal determination count data reaches X (S404: Y), the presence / absence determination control unit 36 ​​sets the value of the mattress removal flag held by the presence / absence determination control unit 36 ​​to 1 (S405), stops the execution of the presence / absence determination process by the presence / absence determination process execution unit 34 (S406), and the processing shown in this processing example is terminated.

[0086] In the processing example shown in FIG. 6 , the condition that the difference between the total weight and the bed frame weight data value is p1 or less for X consecutive times corresponds to the mattress removal condition described above. If the total weight is close to the weight of the bed frame 18, it is highly likely that the mattress 20 is not placed on the bed frame 18. Taking this into consideration, the processing shown in FIG. 6 employs the condition that the difference between the total weight and the bed frame weight data value is p1 or less for X consecutive times as the mattress removal condition described above. However, the mattress removal condition is not limited to this condition. For example, the mattress removal condition may be a condition that a situation in which the difference between the total weight and the bed frame weight data value is p1 or less occurs once.

[0087] Figure 7 is a diagram showing an example of the flow of the presence / absence determination control process executed when the execution of the presence / absence determination process shown in Figures 3 to 5 is stopped, i.e., when the value of the mattress removal flag held in the presence / absence determination control unit 36 ​​is 1.

[0088] The presence / absence determination control unit 36 ​​determines whether the value of the load data indicating the latest measurement result by each of the four load sensors 14 is equal to or greater than E (S501). Here, E is a given value, and may be, for example, the sum of the above-mentioned value D and a predetermined value Y divided by the number of load sensors 14 (here, for example, 4).

[0089] If the value of the load data indicating the latest measurement result by at least one load sensor 14 is not equal to or greater than E (S501: N), the process shown in this processing example is terminated.

[0090] If the value of the load data indicating the most recent measurement results from all four load sensors 14 is equal to or greater than E (S501: Y), the presence / absence determination control unit 36 ​​determines whether the value of the load data indicating the most recent measurement results from all four load sensors 14 is equal to or greater than (F-p2) and equal to or less than (F+p2) (S502). Here, F is, for example, the average value of the most recent measurement results from the four load sensors 14, and p2 is a given threshold. Note that p2 may be a value that depends on F, for example, a value obtained by multiplying F by a predetermined number. For example, p2 may be F x 0.1.

[0091] For at least one load sensor 14, if the value of the load data indicating the latest measurement result by that load sensor 14 is not greater than (F-p2) and less than (F+p2) (S502: N), the processing shown in this processing example is terminated.

[0092] If the value of the load data indicating the most recent measurement result by each of the four load sensors 14 is equal to or greater than (F-p2) and equal to or less than (F+p2) (S502: Y), the presence / absence determination control unit 36 ​​determines whether the variance of the load measurement results of the most recent fixed number of times (e.g., the most recent three times) by each of the four load sensors 14 is equal to or less than p3 (S503), where p3 is a given threshold value.

[0093] If the variance of the load measurement results of at least one load sensor 14 measured the most recent times (for example, the most recent three times) is not less than p3 (S503: N), the processing shown in this processing example is terminated.

[0094] If the variance of the load measurement results of the load sensors 14 measured the most recent times (e.g., the most recent three times) for all four load sensors 14 is less than p3 (S503: Y), the total weight data when the user is away stored in the weight data storage unit 30 is updated to the value indicated by the total weight data based on the most recent measurement results (S504), the value of the mattress removal flag held by the presence / absence determination control unit 36 ​​is set to 0 (S505), the presence / absence determination process execution unit 34 resumes execution of the presence / absence determination process (S506), and the process shown in this processing example is terminated. In other words, the value indicated by the total weight data based on the most recent measurement results is set as value B.

[0095] In the processing example shown in Figure 7, the conditions that the load at all load sensors 14 is E or more, and the difference between the load at all load sensors 14 and the average load at the four load sensors 14 is p2 or less, and the variance of the load measurement results in the nearest neighboring fixed times for all load sensors 14 is p3 or less correspond to the mattress placement conditions described above.

[0096] The condition that the loads at all the load sensors 14 are equal to or greater than E corresponds to an example of a condition related to the magnitude of the load applied to the load sensors 14. Furthermore, the condition that the difference between the load at any load sensor 14 and the average value of the loads at the four load sensors 14 is equal to or less than p2 corresponds to an example of a condition related to the smallness of the variation in the loads applied to the plurality of load sensors 14. Furthermore, the condition that the variance of the load measurement results at the most recent fixed times for all the load sensors 14 is equal to or less than p3 corresponds to a condition related to the smallness of the variation in the most recent multiple measurement results of the load applied to the load sensors 14.

[0097] In this way, the mattress placement conditions may be conditions related to the magnitude of the load applied to the load sensor 14, the smallness of the variation in the load applied to multiple load sensors 14, and the smallness of the variation in the results of the most recent multiple measurements of the load applied to the load sensor 14.

[0098] If the load applied to each load sensor 14 is relatively large, it is highly likely that an object with a certain weight, such as a mattress 20, is placed on the bed frame 18. Furthermore, if the load is evenly distributed across each load sensor 14, it is highly likely that an object, such as a mattress 20, in which the spatial variation in the load applied to each load sensor 14 at a given time is relatively small is placed on the bed frame 18. Furthermore, if the variation in the results of the most recent multiple measurements of the load applied to the load sensors 14 is small, it is highly likely that an object, such as a mattress 20, in which the change in the load applied to each load sensor 14 over time is relatively small is placed on the bed frame 18. Based on this, in the process shown in FIG. 7 , conditions related to the magnitude of the load applied to the load sensor 14, the smallness of the variation in the load applied to the multiple load sensors 14, and the smallness of the variation in the results of the most recent multiple measurements of the load applied to the load sensors 14 are adopted as mattress placement conditions.

[0099] In addition, the mattress placement conditions may be conditions related to at least one of the magnitude of the load applied to the load sensor 14, the smallness of the variation in the load applied to multiple load sensors 14, or the smallness of the variation in the results of the most recent multiple measurements of the load applied to the load sensor 14.

[0100] 7, by executing the process shown in S504, in the presence / absence determination process immediately after restarting, the total weight data indicating the total weight calculated based on the load applied to at least one load sensor 14 when the mattress placement condition is satisfied is used as the unoccupied total weight data (i.e., the total weight data based on the most recent measurement result). In this way, according to this embodiment, when the mattress 20 is replaced, the value of the unoccupied total weight data is calibrated taking into account the weight of the mattress 20 newly placed on the bed frame 18.

[0101] The Doppler data acquisition unit 38 acquires Doppler data indicating the measurement results of each of the Doppler sensors provided facing the subject over a certain period of time.

[0102] For example, as shown in Figure 8, for each of multiple periods (multiple time windows), the Doppler data acquisition unit 38 extracts a portion of the Doppler data indicating the measurement results for that period from the Doppler data indicating the measurement results by the Doppler sensor for each of multiple Doppler sensors.

[0103] For example, Doppler data D(1,1), D(2,1), D(3,1), D(4,1), ... are extracted from the first Doppler data acquired from the first Doppler sensor, indicating measurement results in the first time window, the second time window, the third time window, the fourth time window, .... Furthermore, Doppler data D(1,2), D(2,2), D(3,2), D(4,2), ... are extracted from the second Doppler data acquired from the second Doppler sensor, indicating measurement results in the first time window, the second time window, the third time window, the fourth time window, ....

[0104] Similarly, Doppler data indicating measurement results in each time window is extracted from the third to sixth Doppler sensors. For example, Doppler data D(1,3), D(2,3), D(3,3), D(4,3), ... indicating measurement results in the first time window, the second time window, the third time window, the fourth time window, ... is extracted from the third Doppler data acquired from the third Doppler sensor. Similarly, Doppler data D(1,4), D(2,4), D(3,4), D(4,4), ... indicating measurement results in the first time window, the second time window, the third time window, the fourth time window, ... is extracted from the fourth Doppler data acquired from the fourth Doppler sensor. Furthermore, Doppler data D(1,5), D(2,5), D(3,5), D(4,5), ... indicating measurement results in the first time window, the second time window, the third time window, the fourth time window, ... are extracted from the fifth Doppler data acquired from the fifth Doppler sensor. Furthermore, Doppler data D(1,6), D(2,6), D(3,6), D(4,6), ... indicating measurement results in the first time window, the second time window, the third time window, the fourth time window, ... are extracted from the sixth Doppler data acquired from the sixth Doppler sensor.

[0105] The length of each time window is constant (e.g., 60 seconds), and the start timing of each time window is shifted by a predetermined time (e.g., 2 seconds in this example). The same time window is applied to all of the first through sixth Doppler data. That is, for all of the first through sixth Doppler data, the period corresponding to the first time window is the same, and the period corresponding to the second time window is also the same.

[0106] The frequency spectrum generating unit 40 generates a frequency spectrum for each of a plurality of Doppler sensors, for example, based on Doppler data indicating the measurement results of the Doppler sensors.

[0107] The frequency spectrum generator 40 converts the input Doppler data into a frequency spectrum by, for example, performing a fast Fourier transform (FFT) on the Doppler data. Here, for example, the I signal data and the Q signal data may each be converted into a frequency spectrum.

[0108] The frequency spectrum selector 42 selects a plurality of frequency spectra from among the frequency spectra generated for each of the plurality of Doppler sensors, based on, for example, a peak frequency in the frequency spectrum generated for each of the plurality of Doppler sensors.

[0109] An example of the flow of the frequency spectrum selection process performed by the frequency spectrum selector 42 will now be described with reference to the flow chart shown in Fig. 9. Here, for example, the process of selecting a plurality of frequency spectra from among those generated for the I signal data and Q signal data of each of six Doppler data D(1,1), D(1,2), D(1,3), D(1,4), D(1,5), and D(1,6) extracted for the first time window will be described.

[0110] First, the frequency spectrum selection unit 42 identifies the peak frequency, which is the frequency of the maximum amplitude in the frequency spectrum generated for the I signal data and Q signal data of each of the six Doppler data D(1,1), D(1,2), D(1,3), D(1,4), D(1,5), and D(1,6), as the respiratory rate corresponding to that frequency spectrum (S601).

[0111] Then, the frequency spectrum selection unit 42 calculates a representative value (here, for example, an average value) of the respiratory rate identified in the process shown in S601 (S602).

[0112] Then, the frequency spectrum selection unit 42 checks whether there is a frequency spectrum corresponding to a respiratory rate whose difference from the representative value calculated in the process shown in S602 is a predetermined value (e.g., 5) or more (i.e., an outlier respiratory rate) (S603).

[0113] If there is an outlier respiratory rate (S603: Y), the frequency spectrum selection unit 42 excludes the frequency spectrum corresponding to the outlier respiratory rate (S604), and returns to the process shown in S602.

[0114] If there is no outlier respiratory rate (S603: N), the process shown in this process example is terminated. Note that in the process shown in this process example, none of the frequency spectra may be excluded, and all frequency spectra may be selected.

[0115] The frequency spectra that remain after the above-described process correspond to the frequency spectra selected from the frequency spectra generated for the I signal data and the Q signal data of each of the six Doppler data extracted for the first time window. The above-described process is performed for each of the multiple time windows.

[0116] The aggregate spectrum generation unit 44 generates an aggregate spectrum based on, for example, some or all of the frequency spectra generated for each of the multiple Doppler sensors. As shown in FIG. 10 , for a first time window, aggregate spectrum (1) may be generated by adding, for each frequency, the amplitudes (intensities) of the frequency spectrum of the I signal data of D(1,1), the frequency spectrum of the Q signal data of D(1,1), the frequency spectrum of the I signal data of D(1,2), the frequency spectrum of the Q signal data of D(1,2), the frequency spectrum of the I signal data of D(1,3), the frequency spectrum of the Q signal data of D(1,3), ..., the frequency spectrum of the Q signal data of D(1,6). Aggregate spectrum (1) corresponds to the aggregate spectrum for the first time window. In this way, the aggregate spectrum generation unit 44 may generate an aggregate spectrum that is a frequency spectrum obtained by summing some or all of the frequency spectra generated for each of the multiple Doppler sensors.

[0117] Furthermore, the aggregate spectrum generating unit 44 may generate an aggregate spectrum, which is a frequency spectrum obtained by averaging some or all of the frequency spectra generated for each of the multiple Doppler sensors.

[0118] Furthermore, the aggregate spectrum generation unit 44 may generate an aggregate spectrum based on multiple frequency spectra selected by the frequency spectrum selection unit 42. For example, assume that the frequency spectrum of the I signal data of D(1,5), the frequency spectrum of the Q signal data of D(1,5), the frequency spectrum of the I signal data of D(1,6), and the frequency spectrum of the Q signal data of D(1,6) are excluded, and other frequency spectra are selected. In this case, an aggregate spectrum (1) may be generated, which is a frequency spectrum obtained by summing the frequency spectrum of the I signal data of D(1,1), the frequency spectrum of the Q signal data of D(1,1), the frequency spectrum of the I signal data of D(1,2), the frequency spectrum of the Q signal data of D(1,2), the frequency spectrum of the I signal data of D(1,3), the frequency spectrum of the Q signal data of D(1,3), the frequency spectrum of the I signal data of D(1,4), and the frequency spectrum of the Q signal data of D(1,4). In this way, the influence of outliers on the generated aggregate spectrum can be reduced.

[0119] In Figure 10, aggregate spectrum (1) is shown, which is the aggregate spectrum for the first time window. In a similar manner, aggregate spectrum (2) is shown, which is the aggregate spectrum for the second time window, aggregate spectrum (3) is shown, which is the aggregate spectrum for the third time window, and so on are generated.

[0120] The biological information generating unit 46 generates biological information of the subject based on, for example, Doppler data. The biological information generating unit 46 may generate biological information of the subject for the relevant period based on the aggregate spectrum. Here, the biological information generating unit 46 may generate the subject's respiratory rate for the relevant period based on the peak frequency in the aggregate spectrum. For example, the frequency of the maximum amplitude in the aggregate spectrum may be identified as the peak frequency. Then, the peak frequency in the aggregate spectrum may be generated as the respiratory rate.

[0121] The biological information generating unit 46 may also identify the maximum amplitude and the second largest amplitude in the aggregate spectrum, and then generate an amplitude ratio by dividing the maximum amplitude by the second largest amplitude.

[0122] The biological information generating unit 46 may also generate an amplitude ratio for each of the aggregate spectra calculated for multiple time windows (e.g., the first to thirtieth time windows). The biological information generating unit 46 may then extract aggregate spectra whose amplitude ratios are equal to or greater than a predetermined threshold (e.g., 1.5). The biological information generating unit 46 may then generate an average value of the respiration rates generated for each of the aggregate spectra whose amplitude ratios are equal to or greater than the predetermined threshold (e.g., 1.5) as the respiration rate for a period (e.g., one minute) associated with the multiple time windows.

[0123] Furthermore, the biological information generating unit 46 may generate, as the reliability, the ratio of the number of aggregate spectra whose amplitude ratio is equal to or greater than a predetermined threshold (for example, 1.5) to the number of aggregate spectra calculated for a plurality of time windows.

[0124] In this embodiment, the frequency spectrum may not be selected by the frequency spectrum selector 42. The aggregate spectrum generator 44 may generate an aggregate spectrum for a certain period of time by using all frequency spectra for that period of time generated by the frequency spectrum generator 40.

[0125] Alternatively, the frequency spectrum selector 42 may select a frequency spectrum for each Doppler sensor. That is, the frequency spectrum selector 42 may select multiple Doppler sensors based on peak frequencies in the frequency spectra generated for each of the multiple Doppler sensors. The aggregate spectrum generator 44 may then generate an aggregate spectrum based on the frequency spectra generated for each of the selected Doppler sensors.

[0126] Furthermore, it is not necessary to convert each of the I signal data and the Q signal data into a frequency spectrum. For example, complex signal data with the I component as the real part and the Q component as the imaginary part may be converted into a frequency spectrum. Then, an aggregate spectrum may be generated based on the frequency spectrum.

[0127] When measuring the biological information of a subject using multiple Doppler sensors, depending on the subject's position and posture, some of the measurement results obtained from these multiple Doppler sensors may be low in accuracy.

[0128] Therefore, if biometric information is measured using each of these multiple Doppler sensors and a representative value such as the average value of the measured biometric information is used as the value of the subject's biometric information, the value of the biometric information obtained in this way may not be a valid value.

[0129] As described above, in this embodiment, the biological information is generated based on the aggregate spectrum. Therefore, according to this embodiment, the biological information of the subject can be measured more accurately than when a representative value such as an average value of the measured biological information is used as the value of the biological information of the subject.

[0130] Furthermore, for example, since each Doppler sensor is oriented at a different angle relative to the subject, the peak frequencies of the frequency spectrum based on the measurement results may differ slightly. Here, when multiple Doppler sensors are arranged in a line perpendicular to the length of the bed 16, when multiple Doppler sensors are arranged symmetrically with respect to the center line of the bed 16, when multiple Doppler sensors are arranged in a line at equal intervals, or the like, an aggregate spectrum is generated in which the frequency spectra corresponding to the individual Doppler sensors are appropriately averaged, and as a result, it becomes possible to measure the subject's biological information with greater accuracy.

[0131] In the following description, it is assumed that the above-mentioned respiratory rate is generated at one-minute intervals.

[0132] The abnormality determination unit 48 determines whether the biological information of the subject satisfies a given abnormality determination condition, for example. Here, the abnormality determination condition may be, for example, a condition that the respiratory rate is 8 or less or 25 or more for all of the five most recently generated respiratory rates.

[0133] The action execution unit 50 executes a given action when, for example, the biological information of the subject satisfies the abnormality determination condition described above.

[0134] Here, the action execution unit 50 may execute a first action when the presence / absence information indicates that the person being measured is on the mattress 20, and may execute a second action when the presence / absence information indicates that it is unclear whether the person being measured is on the mattress 20. For example, when the value of the user-one-presence flag stored in the presence / absence information storage unit 60 is 1, an emergency call action (e.g., requesting an ambulance) may be executed in response to the person being measured's biological information satisfying the abnormality determination condition. When the value of the unknown flag stored in the presence / absence information storage unit 60 is 1, an abnormality notification action (e.g., outputting an alarm) may be executed in response to the person being measured's biological information satisfying the abnormality determination condition.

[0135] For example, when the presence / absence information indicates that the person being measured is not on the mattress 20, the operation control unit 52 suppresses the execution of an action in response to the biological information satisfying the abnormality determination condition.

[0136] Here, the operation control unit 52 may monitor the value of the one-user presence flag and the value of the unknown flag stored in the presence / absence information storage unit 60 .

[0137] The operation control unit 52 may then stop the Doppler sensor upon detecting a change from a situation in which the value of the 1 user present flag or the value of the unknown flag is 1 to a situation in which the value of both the 1 user present flag and the unknown flag is 0.

[0138] Furthermore, the operation control unit 52 may activate the Doppler sensor in response to detecting a change from a situation where the value of the one user presence flag and the value of the unknown flag are both 0 to a situation where the value of the one user presence flag or the value of the unknown flag is 1. Then, generation of the respiratory rate may be resumed.

[0139] In this way, by stopping the operation of the Doppler sensor, the execution of an action in response to the biological information satisfying the abnormality determination condition may be suppressed.

[0140] In addition, when the presence / absence information indicates that the person being measured is on the mattress 20 and it is determined that the person being measured is moving, the operation control unit 52 may suppress the execution of an action in response to the biological information satisfying the abnormality determination condition.

[0141] For example, assume that the value of the stored one-user presence flag is 1. In this case, the movement control unit 52 may monitor the value of the body movement information stored in the body movement information storage unit 62.

[0142] Then, the operation control unit 52 may stop the Doppler sensor in response to detecting that the value of the body movement information has changed from 1 to 0.

[0143] Furthermore, the operation control unit 52 may activate the Doppler sensor in response to detecting a change in the value of the body movement information from 0 to 1. Then, generation of the respiratory rate may be resumed.

[0144] Note that the action executing unit 50, rather than the operation control unit 52, may suppress the execution of an action corresponding to the biological information satisfying the abnormality determination condition when the presence / absence information indicates that the subject is not on the mattress 20. For example, assume that the Doppler sensor is operating and the above-mentioned respiratory rate is generated at one-minute intervals. In this situation, even if the biological information of the subject satisfies the given abnormality determination condition, the action executing unit 50 may not execute the given action described above if the value of the user presence flag and the value of the unknown flag stored in the presence / absence information storage unit 60 are both 0. Furthermore, even if the biological information of the subject satisfies the abnormality determination condition, the action executing unit 50 may not execute the given action described above if the value of the stored body movement information is 1.

[0145] When the respiration rate of the person being measured indicates an abnormal value, it is not possible to determine whether this is because an abnormality has occurred in the person being measured, or because the person being measured is not on the mattress 20. In this embodiment, as described above, it is accurately determined whether the person being measured is on the bed or not. Therefore, when the respiration rate of the person being measured indicates an abnormal value, it is possible to determine whether this is because an abnormality has occurred in the person being measured, or because the person being measured is not on the mattress 20.

[0146] Furthermore, as described above, the execution of an action in response to the biological information satisfying the abnormality determination condition may be suppressed when the presence / absence information indicates that the person being measured is not on the mattress 20. In this way, it is possible to prevent, for example, the erroneous execution of an action such as calling an ambulance or outputting an alarm sound when the person being measured is not on the mattress 20.

[0147] Furthermore, if the subject is moving, the respiratory rate is likely to be inaccurately detected. In light of this, as described above, if it is determined that the subject is moving, the execution of an action corresponding to the biological information satisfying the abnormality determination condition may be suppressed. This makes it possible to prevent an action from being erroneously executed based on a respiratory rate that is likely to be inaccurate.

[0148] Furthermore, as described above, the Doppler sensor may be stopped when the presence / absence information indicates that the person being measured is not on the mattress 20. In this way, it is possible to reduce the power consumption of the Doppler sensor.

[0149] Furthermore, as described above, if a person or animal (such as a pet or the subject's child) on the mattress 20 is too heavy or too light compared to the subject, it may be determined that it is unclear whether the subject is on the mattress 20. In this case, in response to the biological information satisfying the abnormality determination condition, an emergency call action (e.g., requesting an ambulance) is not executed, but an abnormality notification action (e.g., outputting an alarm) is executed. This can reduce missed reports. It can also prevent the emergency call action from being executed unnecessarily.

[0150] In this embodiment, the estimated weight of the person being measured (value A) may be output (for example, as a display output or an audio output). This allows the weight, which may fluctuate slightly from day to day, to be measured without any burden on the person being measured, simply by lying down.

[0151] Furthermore, in this embodiment, if the mattress 20 placed on the bed frame 18 is removed or replaced with another mattress 20 of a different weight, the presence / absence determination process described above can no longer properly determine whether or not a person is present on the bed 16. In particular, the value of the total weight data when the person is absent can no longer be said to be a reliable value.

[0152] In this embodiment, as described above, if the mattress removal condition is satisfied while the presence / absence determination process is being executed, the execution of the presence / absence determination process is stopped. This prevents unnecessary execution of the presence / absence determination process in a situation where it can no longer be properly determined whether the person being measured is on the bed 16. In this way, according to this embodiment, the execution of the presence / absence determination process can be properly controlled.

[0153] Furthermore, in this embodiment, if the mattress removal condition is met while the presence / absence determination process is being executed, the execution of the presence / absence determination process is stopped. Therefore, when the mattress 20 is replaced and a new mattress 20 is placed on the bed frame 18, it is possible to prevent the person being measured from being mistakenly determined to be on the bed 16 when they are not on the bed 16.

[0154] The present invention is not limited to the above embodiment and various modifications are possible. For example, in the above description, the respiratory rate is generated as the biological information of the subject, but the heart rate can also be generated in a similar manner. In this case, a given action may be executed in response to the heart rate satisfying a given abnormality determination condition.

Claims

1. A presence / absence determination control system comprising: a presence / absence determination process execution means for repeatedly executing a presence / absence determination process to determine whether a person being measured is on a mattress placed on a bed frame based on the measurement results of the load applied to at least one load sensor supporting the bed frame of a bed used by the person being measured; and a presence / absence determination stop means for stopping the execution of the presence / absence determination process when, while the presence / absence determination process is being executed, the comparison result between the total weight calculated based on the load applied to the at least one load sensor and a given bed frame weight value indicating the weight of the bed frame satisfies a given mattress removal condition.

2. The presence / absence determination control system according to claim 1, further comprising a presence / absence determination restart means for restarting the execution of the presence / absence determination process in response to a given mattress placement condition being met when execution of the presence / absence determination process has been stopped.

3. A presence / absence determination control system according to claim 2, wherein the mattress placement condition is a condition relating to the magnitude of the load applied to the load sensor.

4. A presence / absence determination control system according to claim 2, wherein the mattress placement condition is a condition relating to the smallness of variation in the loads applied to the plurality of load sensors.

5. A presence / absence determination control system according to claim 2, wherein the mattress placement condition is a condition relating to the smallness of variation in the results of the most recent multiple measurements of the load applied to the load sensor.

6. In the presence / absence determination control system according to claim 2, the presence / absence determination process execution means comprises: total weight data acquisition means for acquiring total weight data indicating a total weight calculated based on the load applied to at least one of the load sensors; presence / absence information retention means for retaining presence / absence information indicating whether the person being measured is on the mattress; presence change means for, when the presence / absence information indicates that the person being measured is not on the mattress and the magnitude of an increase, which is the value indicated by the total weight data based on the latest measurement result minus the value indicated by the total weight data based on the immediately preceding measurement result, satisfies a given presence determination condition; and absence change means for, when the presence / absence information indicates that the person being measured is on the mattress and the magnitude of a decrease, which is the value indicated by the total weight data based on the immediately preceding measurement result minus the value indicated by the total weight data based on the latest measurement result, satisfies a given presence determination condition, changing the retained presence / absence information to indicate that the person being measured is not on the mattress. In this presence / absence determination control system, when the presence / absence determination process is resumed immediately after restarting, the total weight data indicating the total weight calculated based on the load applied to at least one of the load sensors when the mattress placement condition is met is used as the total weight data based on the most recent measurement result.

7. A presence / absence determination control system according to claim 1, wherein each of the four corners of the bed frame is supported by the load sensor.

8. A presence / absence determination control system as described in claim 1, further comprising: a Doppler data acquisition means for acquiring Doppler data indicating the measurement results by a Doppler sensor provided facing the person being measured; a biometric information generation means for generating biometric information of the person being measured based on the Doppler data; an action execution means for executing a given action in response to the biometric information satisfying a given abnormality determination condition; and a suppression means for suppressing the execution of the action in response to the biometric information satisfying the abnormality determination condition when it is determined that the person being measured is not on the mattress.

9. A presence / absence determination control method comprising: a step of repeatedly executing a presence / absence determination process to determine whether a person being measured is on a mattress placed on a bed frame based on the measurement results of the load applied to at least one load sensor supporting the bed frame of a bed used by the person being measured; and a step of stopping the execution of the presence / absence determination process when, while the presence / absence determination process is being executed, the comparison result between the total weight calculated based on the load applied to the at least one load sensor and a given bed frame weight value indicating the weight of the bed frame satisfies a given mattress removal condition.

10. A program for causing a computer to execute the following steps: repeatedly executing a presence / absence determination process to determine whether a person being measured is on a mattress placed on a bed frame based on the measurement results of the load applied to at least one load sensor supporting the bed frame of a bed used by the person being measured; and stopping the execution of the presence / absence determination process when, while the presence / absence determination process is being executed, the comparison result between the total weight calculated based on the load applied to the at least one load sensor and a given bed frame weight value indicating the weight of the bed frame satisfies a given mattress removal condition.

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