JP2012011174A - In-bed state determination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide in-bed state determination technology for properly determining an in-bed state.SOLUTION: A plurality of load meters are disposed such that the load meters distributively measure loads of every moment applied onto installation faces by a bed. A gravity center calculation part calculates the gravity center based on a plurality of measurement values measured by the plurality of load meters. A gravity center variation amount calculation part calculates a gravity center variation amount that is a variation amount of the gravity center within a prescribed time, and person presence/absence determination part determines whether a person is present or absent on the bed based on the gravity center variation amount.

Description

  The present invention relates to a technique for determining the presence of a person on a bed, particularly a technique for determining the presence of a person, the presence or absence of a person, the sleep state of a person, and the posture of a person.

  In hospitals and elderly facilities, for the safety management of patients and residents, whether these people are on the bed, what kind of posture they are on the bed, and sleeping There is a desire to check if there is or is awake.

  However, it is difficult to always confirm with a patrol by staff. In addition, when a surveillance camera or the like is used, there arises a problem of privacy and an increase in surveillance burden of patients and residents.

  In order to solve these problems, a technique for determining the presence or absence of a person on the bed based on the load on the bed has been proposed. For example, a load detection unit that detects a load by inputting a load sensor signal that can detect a load on the bed floor, an average value set for a short time from a load value that is detected every moment, and a setting The average value calculating means for calculating the average value over the long time, the difference calculating means for calculating the difference between the short time average value and the average value over the long time, and the state on the bed from the obtained difference value There is a state detection system for a user in a bed provided with a state determination means for determination (see Patent Document 1).

  In the technique of Patent Document 1, the load on the bed is measured every moment by the load detection means, and a short time average value and a long time average value are calculated. Thereafter, the state on the bed is determined based on the difference between the short time average value and the long time average value. Therefore, the robustness against the measurement error is improved as compared with the method of determining based on the load value every moment.

  In addition, there is a person on the bed when the load sensor interposed between the bed column and the floor and the load detected by the load sensor exceeds a preset reference value according to a predetermined condition. The presence determination means that determines that the person is present, the reset switch that sets the load applied when there is no person on the bed as the reference value of the presence determination means, and the determination result by the presence determination means to the outside And a transmitting means that transmits the information (see Patent Document 2).

  In the technique of Patent Document 2, when it is determined that there is no person on the bed, the reference value for determining occupancy is reset. Therefore, an appropriate reference value can be set even when an object other than a person is placed on the bed.

  Also, a sensor unit that is disposed between the bed table and the mattress placed on the bed table and generates electric charges in response to vibration caused by a sleeper's heartbeat and breathing on the mattress, and generated in the sensor unit A conversion unit that converts the converted electric charge into an electrical signal and outputs it, a biological information extraction unit that extracts a vibration component in the heart rate frequency band and a vibration component in the respiration frequency band from the output signal of the conversion unit, and a biological information extraction unit And a sleep state estimation unit that estimates any one sleep state among a plurality of sleep states according to the sleep depth of the sleeper from the biological information obtained in the above, the sleep state estimation unit is based on the biological information The body motion of the sleeper is estimated and the body motion of the sleeper or the state that does not correspond to any of the sleep states is defined as the body motion / transient state, and the body motion / transient state is combined with the sleep Sleep state to estimate the sleep state of the elderly There is estimation device (see Patent Document 3).

  In the technique of Patent Literature 3, since the state of occurrence of body movement is detected and the sleep state is estimated including the state of occurrence of body movement, the accuracy of sleep state estimation of the sleeping person can be improved.

JP 2009-118980 A JP-A-10-55491 JP 2009-297455 A

  However, in the technique of Patent Document 1, since the occupancy state is determined simply by the difference between the short-time average value and the long-time average value of the measured load, when a person other than a person is placed on the bed, etc. It is impossible to accurately determine the presence state.

  In the technique of Patent Document 2, although the reference value for determining the occupancy state can be reset, the determination of the occupancy state is simply performed by comparing the measured load with a predetermined threshold. Accurate bed determination is difficult. In addition, since the reference value is reset based on inaccurate bed presence determination, it is difficult to set an appropriate reference value.

  On the other hand, using the body movement state when estimating the sleep state of the sleeper as in the technique of Patent Document 3 contributes to the improvement of the sleep state estimation accuracy. However, if the sensor is installed between the bed table and the mattress as in the technique of Patent Document 3, the sensor output varies depending on the position of the sleeping person, and the body movement state and the sleeping state can be accurately determined. It becomes difficult. Further, since the sensor output is affected by the weight of the mattress, it is necessary to adjust the threshold for determining the body movement state and the sleeping state for each mattress.

  This invention is made | formed in view of the said subject, The objective is to provide the occupancy state determination technique which can determine an occupancy state exactly.

  In order to solve the above-mentioned problem, the presence-of-floor state determination device according to the present invention is measured by a plurality of load cells arranged so as to distribute and measure the load applied to the installation surface by the bed, and the plurality of load meters. A center-of-gravity calculation unit that calculates the center of gravity based on a plurality of measurement values, a center-of-gravity variation calculation unit that calculates a center-of-gravity variation amount that is a variation amount of the center of gravity within a predetermined time, and the bed center based on the center-of-gravity variation amount The presence / absence determination unit for determining the presence / absence of the person is provided.

  When a person is on the bed, the center of gravity fluctuates somewhat due to the influence of breathing and pulsation even when the person is at rest. On the other hand, when an object is placed on the bed, the center of gravity is ideally constant. Therefore, even when a load is generated on the bed, it is possible to determine whether or not a person is present on the bed by tracking a change in the center of gravity of the load. Therefore, in this configuration, the presence / absence of a person on the bed is determined based on the fluctuation amount of the center of gravity calculated based on the measurement value of the load meter within a predetermined time.

  In one preferred embodiment of the in-situ state determination device of the present invention, the centroid calculating unit calculates a measured value centroid that is a centroid of the plurality of measured values themselves.

  In this configuration, since the center of gravity of the measurement values for all weights including the bed and the person on the bed is calculated, the center of gravity can be calculated with a simple configuration.

  When the weight of a person is smaller than the weight of the bed, the influence of the bed is greater on the center of gravity than the person, making it difficult to accurately measure the movement of the person's center of gravity. Therefore, in one of the preferred embodiments of the presence state determination apparatus of the present invention, a load that stores, for each load meter, a reference load having an initial value of the plurality of measurement values in a state where no person is present. A storage unit, and the center-of-gravity calculation unit calculates a corrected center of gravity that is a center of gravity of a correction load obtained by subtracting the reference load from the plurality of measurement values.

  In this configuration, the center of gravity is calculated based on a correction load obtained by subtracting a reference load having the plurality of measurement values in the state where no person is present as initial values from the measurement values. Therefore, the correction load is a load reflecting the weight of the person or object that applies the load to the bed, and the center of gravity of the correction load is the center of gravity of the person or object. Therefore, the center of gravity of the person or object can be accurately measured, and the accuracy of presence determination can be improved.

  In one of the preferred embodiments of the bed presence determination apparatus of the present invention, the reference stored in the load storage unit when the human presence determination unit determines that no person is present on the bed. The load is updated with the plurality of measurement values used for the determination.

  In this configuration, when it is determined that no person is present on the bed, the measurement value at that time is set as the reference load. Therefore, when an object is placed on the bed, the weight of the bed and the object becomes the reference load, and the weight and center of gravity of the person can be accurately measured. Thereby, the accuracy of occupancy determination can also be improved.

  In one preferred embodiment of the presence state determination apparatus of the present invention, a threshold setting unit that sets a threshold for the center of gravity information obtained from the corrected center of gravity, a comparison unit that compares the center of gravity information and the threshold, It has.

  In this configuration, the threshold for the centroid information can be set as appropriate, and the comparison unit compares the centroid information with the set threshold. As described above, the corrected center of gravity represents the center of gravity of the person on the bed, and the movement of the corrected center of gravity is caused by noise from the load cell, caused by human breathing, heartbeat, etc. It can be roughly divided into things caused by movement. According to the researches of the inventors of the present invention, it is found that these amounts of movement of the center of gravity are different from each other and can be separated based on a threshold value. Therefore, if the threshold value setting unit sets an appropriate threshold value for the center of gravity information obtained from the corrected center of gravity according to the state to be detected and compares the center of gravity information with the threshold value, noise separation and presence / absence of body movement Can be detected. Moreover, if a body motion can be detected, it can be determined whether the person on the bed is in a sleep state or in an awake state based on the body motion. Furthermore, body movements can be classified into normal body rolls and the like, and abnormal body movements caused by pain and worsening of medical conditions, etc., and these can also be separated by a threshold for the center of gravity information. In other words, in this configuration, it is possible to determine various states of a person by setting a threshold by the threshold setting unit and based on the determination result by the determination unit.

  Further, the weight of the person on the bed can be calculated from the corrected load, and based on the center of gravity information obtained from the weight and the corrected center of gravity, the person's posture on the bed can be determined. Therefore, in one of the preferred embodiments of the presence-of-floor state determination apparatus of the present invention, the weight of the person on the bed is calculated based on the correction load, and the weight information and the gravity center information obtained from the correction gravity center are obtained. A posture determination unit for determining the presence posture of the person based on the posture is provided.

  The center-of-gravity fluctuation amount can be calculated by various methods. For example, in one of the preferred embodiments of the occupancy state determination device of the present invention, the center-of-gravity variation calculation unit includes the center of gravity at a predetermined time point and the center of gravity at each time point in the predetermined time period from the predetermined time point. Is calculated as the center of gravity variation.

  In this configuration, the sum of the deviation between the center of gravity at a predetermined time and the center of gravity at each time point in the past for a predetermined period from the predetermined time is used as the center of gravity variation. Thereby, the center-of-gravity variation amount can be calculated by a simple calculation.

  In one preferred embodiment of the presence-of-floor state determination apparatus of the present invention, the human presence determination unit determines the presence / absence of a person on the bed based on a value obtained by correcting the center of gravity variation. In this configuration, since the presence / absence of a person on the bed is determined based on the corrected center-of-gravity variation, the presence / absence of the person can be determined more accurately. The correction is, for example, correction of measurement errors such as load meter noise. In addition, when a person's body weight is very light compared to the weight of the bed, the displacement of the center-of-gravity variation amount derived from the total load becomes very small, which may reduce the accuracy of the presence / absence determination of the person. Even in such a case, it is desirable to correct the center of gravity variation. Therefore, in one of the preferred embodiments of the occupancy state determination apparatus of the present invention, the variation in the center of gravity is corrected by multiplying the sum of the plurality of measurement values. Thereby, the center-of-gravity fluctuation amount is scaled, the displacement becomes clear, and it is possible to suppress a decrease in the accuracy of the human existence determination.

1 is a configuration diagram of a occupancy state determination device in Embodiment 1. FIG. 3 is a flowchart illustrating the flow of a occupancy state determination process in the first embodiment. It is a figure which shows arrangement | positioning of a load sensor. It is a graph showing the change of a gravity center variation | change_quantity. It is a block diagram of the occupancy state determination apparatus in Example 2. 10 is a flowchart illustrating the flow of a occupancy state determination process in the second embodiment. It is a block diagram of the presence state determination apparatus in Example 3. FIG. 10 is a flowchart illustrating the flow of a occupancy state determination process according to a third embodiment.

  Hereinafter, embodiments of the occupancy state determination apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a occupancy state determination apparatus A according to the present invention. As shown in the figure, the occupancy state determination device A according to the present embodiment includes a plurality of load sensors S (an example of the load meter of the present invention) and a control device C including a general-purpose computer.

  Further, as shown in the figure, the plurality of load sensors S are arranged between the leg portion L of the bed B and the placement surface (floor or the like) of the bed B. In the present embodiment, the bed B has four leg portions L, and four load sensors S are arranged corresponding to the respective leg portions L (see FIG. 3). Therefore, the load applied to the placement surface by the bed B is distributed and measured by the four load sensors S. That is, the sum total of the measured values of the four load sensors S becomes a load applied to the placement surface by the bed B. The load sensor S measures the load every moment and transmits the measured value to the control device C. In addition, when it is not necessary to distinguish each load sensor S, they are collectively referred to as load sensor S or load sensor Si (i = 1 to 4). Indicated as S1, S2, S3 and S4.

  On the other hand, the control device C includes a control unit 1 that performs various controls, a center-of-gravity calculation unit 3 that calculates the center of gravity of the load, a center-of-gravity variation calculation unit 4 that calculates the amount of variation of the center of gravity calculated by the center-of-gravity calculation unit 3, A human presence / absence determination unit 5 is provided for determining the presence / absence of a person on the bed B based on the center of gravity variation calculated by the amount calculation unit 4.

  In the present embodiment, the control unit 1, the centroid calculation unit 3, the centroid variation calculation unit 4, and the presence / absence determination unit 5 are configured by software. However, hardware or software and hardware may cooperate with each other. I do not care.

  The control unit 1 has a function of acquiring a measurement value from the load sensor S at a predetermined time interval and giving an instruction to each functional unit.

  The center of gravity calculation unit 3 has a function of calculating the center of gravity of the load. In this embodiment, the center of gravity is calculated based on the measurement value of the load sensor S. Since the measurement value of the load sensor S includes the load due to the bed B and the person lying on the bed B or the object placed on the bed B, the total of the measurement values of the load sensor S is the total load, the load The center of gravity calculated based on the measured value of the sensor S is referred to as the total load center of gravity (an example of the measured value center of gravity of the present invention). In addition, it is not necessary to include all the loads caused by the person who is in bed B and bed B or the object placed on bed B in the total load, for example, the weight of the object placed on bed B If it is known, the measurement value corrected by its weight may be the total load.

  The center-of-gravity variation calculation unit 4 calculates the amount of variation of the center of gravity calculated by the center-of-gravity calculation unit 4 within a predetermined time (hereinafter referred to as the center-of-gravity variation).

  The presence / absence determination unit 5 determines the presence / absence of a person on the bed B based on the center-of-gravity variation calculated by the center-of-gravity variation calculation unit 4.

  FIG. 2 is a flowchart showing the processing flow of the occupancy state determination apparatus A according to the present embodiment. First, initialization is performed in a state where no person is present on the bed B (# 01). Specifically, the control unit 1 resets the center of gravity (details will be described later) at each time stored in a memory (not shown).

  When the initialization is completed, the control unit 1 acquires the measurement value of the load sensor S at a predetermined sampling interval, and executes the following processing. In this embodiment, the sampling interval is set so that sampling is performed 100 times per minute, but this sampling interval can be set as appropriate.

When the control unit 1 acquires the measurement values WFi (t) (i = 1 to 4) of the load sensors Si (# 02), the measurement values WFi (t) are sent to the gravity center calculation unit 3. Note that WFi is a measured value measured by the load sensor Si, and t represents the time when the measured value WFi is acquired.
When the center-of-gravity calculation unit 3 acquires the four measurement values WFi (t), the center-of-gravity calculation unit 3 calculates the total load center of gravity ga (t) based on these values (# 03). FIG. 3 is a diagram illustrating the arrangement of the load sensors S. As shown in the figure, when the bed B is viewed from above, a load sensor S1 is placed on the right side of the head, a load sensor S2 is placed on the left side of the head, a load sensor S3 is placed on the left side of the foot side, and a load sensor S4 is placed on the right side of the foot side. It is arranged. As shown in the figure, the X axis is set along the long side of the bed B, the Y axis is set along the short side of the bed B, and the head side is set as the origin. Therefore, the total load gravity center ga (t) can be obtained by the following equation.

  Note that the center of gravity calculated by Equation (1) is a normalized center of gravity, but it is not always necessary to perform normalization.

  The total load gravity center ga (t) at each time calculated in this way is temporarily stored in the memory in order of time. The total load gravity center ga stores only a predetermined number, and when the total load gravity center ga exceeds the predetermined number, it is managed in a FIFO (First In First Out) format. That is, the oldest total load gravity center ga is discarded, and the newest total load gravity center ga is stored. In the present embodiment, the predetermined number is set to 11.

  When the calculation of the total load gravity center ga is completed, the gravity center calculation unit 3 notifies the gravity center variation calculation unit 4 to that effect. The center-of-gravity variation calculation unit 4 that has received the notification from the center-of-gravity calculation unit 3 checks whether or not the total load center of gravity ga for a predetermined time is stored in the memory (# 04). In this embodiment, the predetermined time interval is 11 sampling intervals. That is, the total load gravity center ga at the present time and the past 10 times is stored in the memory. The primary storage number of the above-described total load centroid ga is equal to the number of centroids required in the centroid variation calculation unit 4. It should be noted that the length of the period used for calculating the center of gravity variation can be set as appropriate.

If the required number (11 in this example) of total load gravity centers ga is not stored in the memory (No branch of # 04), the process proceeds to # 02, and the above process is repeated. On the other hand, if the required number of total load centroids ga is stored in the memory (Yes branch of # 04), the deviation between the centroid at the current time t and the centroid at each time in the past for a predetermined period from the current time t is calculated by the following formula. The sum is calculated as the center of gravity variation V (# 05).

  In this embodiment, the deviation is the Euclidean distance (2 norm), but other distances such as 1 norm may be used.

The calculated center-of-gravity variation V is sent to the human existence determination unit 5. The presence / absence determination unit 5 that has acquired the center of gravity variation V compares the center of gravity variation V with a predetermined threshold TH (# 06), and if the center of gravity variation V is greater than the threshold TH (Yes branch of # 06). It is determined that a person is on the bed B (# 07). On the other hand, if the center-of-gravity variation V is equal to or less than the threshold value TH (No branch at # 06), it is determined that the person is getting out of bed B (# 08). This determination result is returned to the control unit 1.

  The control unit 1 performs a predetermined process based on the acquired determination result. For example, when a person who should be in bed is not in bed, a nurse or the like is notified.

  FIG. 4 is a graph showing changes in the center of gravity variation. The vertical axis represents the center of gravity variation, and the horizontal axis represents time. Moreover, the solid line in a figure is a state in which the person is on the bed B, and the dotted line in the figure is a state in which the person has left the bed B. As is clear from the figure, when the person is on the bed B, the amount of variation in the center of gravity is large. Therefore, as described above, the presence / absence of a person on the bed B can be accurately determined based on the variation in the center of gravity.

  It should be noted that immediately after a person or an object is placed on the bed B, the measurement value by the load sensor S is not stable, and it is difficult to make an accurate determination even if the presence state determination is performed based on such a measurement value. Therefore, it is possible to adopt a configuration in which the occupancy state determination process is not performed while the measurement value of the load sensor S is not stable.

  FIG. 5 is a configuration diagram of the occupancy state determination apparatus A in the present embodiment. The functional unit of the control device C in the present embodiment is further provided with a load storage unit 2 for storing a reference load and a threshold setting unit 8 for setting a threshold for the presence / absence determination unit 5 in addition to the functional unit of the first embodiment. ing. The center of gravity calculation unit 3 includes a correction load calculation unit 3a that calculates a correction load described later, and is different from the first embodiment in that the correction center of gravity is calculated based on the correction load. In this embodiment, the presence / absence determination unit 5 functions as a comparison unit of the present invention.

  The load storage unit 2 is configured by a RAM (Random Access Memory) and stores a reference load for each load sensor Si. Here, the reference load WSi is a measured value WFi measured by the load sensor Si, and an initial value is a measured value WFi of the load sensor Si when no person is on the bed B. The load storage unit 2 may be configured by a nonvolatile storage medium such as a hard disk or a flash memory.

  The correction load calculation unit 3a is configured by software and has a function of obtaining a correction load. The correction load is a value obtained by subtracting the reference load WSi from the measurement value WFi measured by the load sensor Si. That is, the correction load Wri = WFi−WSi.

  FIG. 6 is a flowchart showing the flow of processing in this embodiment. First, the occupancy state determination device A is initialized (# 11). The initialization in the present embodiment is the reset of the center of gravity at each time and the reference load WSi stored in the memory and the setting of the threshold for the human presence determination unit 5 by the threshold setting unit 8. As described above, the initial value of the reference load WSi is the measured value WFi of the load sensor Si when no person is present on the bed B. Therefore, the initialization of the reference load WSi needs to obtain the measurement value WFi of the load sensor Si in a state where no person is present on the bed B. For example, the reference load WSi can be ensured by starting the occupancy state determination device A in a state where no person is on the bed B, or by giving an initialization command to the occupancy state determination device A by the operator. Can be initialized. Note that the initialization timing is not limited to these, and it may be performed by simply determining that there is no person on the bed based on the change in the measured value WFi of the load sensor Si. Even if the presence state of the person here is erroneously determined, there is no problem because a correct reference load WS can be obtained by the processing described later.

  In this way, the control unit 1 resets the center-of-gravity fluctuation amount at each time as initialization, acquires the measured values WFi from the four load sensors Si, and stores them as the reference load WSi in the load storage unit 2. Let In addition, an instruction to perform the presence / absence determination of a person is sent from the control unit 1 to the threshold setting unit 8, and the threshold setting unit 8 sets a threshold value TH suitable for the presence / absence determination of the person to the human presence determination unit 5. Set.

When the initialization is completed, the control unit 1 acquires the measurement value of the load sensor Si at a predetermined sampling interval, and executes the following processing.

When the control unit 1 acquires the measurement values WFi (t) (i = 1 to 4) of each load sensor Si (# 12), these measurement values WFi (t) are sent to the gravity center calculation unit 3. In the center-of-gravity calculation unit 3 that has acquired the measurement value WFi (t), the correction load calculation unit 3a calculates the correction load Wri (t) = WFi (t) −WSi (# 13). As described above, since the reference load WSi is the measured value WFi when no person is present on the bed B, the correction load Wri (t) when the person is present on the bed B. Represents the weight of a person. Based on this corrected load Wri, the corrected center of gravity gr (t) is obtained by the following equation (# 14).

  The obtained corrected center of gravity gr (t) is stored in the memory in the FIFO format as in the first embodiment. When the calculation of the corrected center of gravity gr (t) is completed, the center of gravity calculating unit 3 notifies the center of gravity variation calculating unit 4 to that effect. The center-of-gravity variation calculation unit 4 that has received the notification from the center-of-gravity calculation unit 3 checks whether or not the corrected center of gravity gr for a predetermined time is stored in the memory (# 15). If the required number (11 in this example) of corrected gravity centers gr is not stored in the memory (No branch of # 15), the process proceeds to # 12 and the above-described process is repeated. On the other hand, if the required number of corrected center of gravity gr is stored in the memory (Yes branch of # 15), the center-of-gravity variation amount V (example of center-of-gravity information of the present invention) is calculated by Expression (2) as in the first embodiment. (# 16).

  The calculated center-of-gravity variation V is sent to the human existence determination unit 5. The presence / absence determination unit 5 that has acquired the center of gravity variation V compares the center of gravity variation V with the threshold TH set as described above (# 17), and if the center of gravity variation V is greater than the threshold TH (# 17). Yes branch), it is determined that a person is present on the bed B (# 18). On the other hand, if the center-of-gravity variation V is equal to or less than the threshold value TH (No branch at # 17), it is determined that the person is getting out of bed B (# 19). This determination result is returned to the control unit 1.

  The control unit 1 that has acquired the determination result executes the same processing as in the first embodiment. In the present embodiment, when the determination result that the person is getting out of bed B is received, the control unit 1 updates the reference load WSi in the load storage unit 2 (# 20). Specifically, the measured value WFi (t) of the load sensor Si at the present time, that is, at time t is stored as the reference load WSi. With this process, the reference load WSi always represents a load excluding the human weight, and the correction load Wr represents the human weight.

  As described above, in this embodiment, since the center of gravity variation is calculated based on the correction load Wr, the center of gravity variation that is not affected by the weight of the bed B can be calculated, and the determination accuracy of the person's presence state is determined. Can be increased.

  FIG. 7 is a configuration diagram of the occupancy state determination apparatus according to the present embodiment. The functional unit of the control device C according to the present embodiment further includes a sleep state determination unit 6 and a bed B, which are configured by software and determine the sleep or wakefulness of a person on the bed B, compared to the functional unit of the second embodiment. A posture determination unit 7 for determining the posture of the upper person is provided. In this embodiment, the presence / absence determination unit 5 and the sleep state determination unit 6 function as a comparison unit of the present invention.

  The sleep state determination unit 6 determines the body motion of the person on the bed B based on the corrected center of gravity gr calculated by the center of gravity calculation unit 3, and based on the body motion, whether the person is in a sleep state or not Determine if there is.

  The posture determination unit 7 calculates the weight of the person on the bed B based on the correction load Wr calculated by the gravity center calculation unit 3, and based on the weight and the corrected gravity center gr calculated by the gravity center calculation unit 3. The posture of the person on the bed B is determined.

  FIG. 8 is a flowchart showing the processing flow of the occupancy state determination apparatus A according to the present embodiment. Since the processing from # 31 to # 40 is the same as the processing from # 11 to # 20 in the second embodiment, detailed description thereof is omitted. However, in the present embodiment, the center of gravity calculation unit 3 sends the calculated correction center of gravity gr to the sleep state determination unit 6 and the posture determination unit 7 and sends the correction load Wr to the posture determination unit 7. In the initialization process of # 31, the threshold value setting unit 8 sets a threshold value suitable for the presence / absence determination of the person and a threshold value suitable for the determination of the human body movement for the human presence determination unit 5 and the sleep state determination unit 6, respectively. It is set.

  The control unit 1 that has received the determination result that the person is present in the bed B from the presence / absence determination unit 5 sends an instruction to the sleep state determination unit 6 and the posture determination unit 7 to perform the determination process.

  The sleep state determination unit 6 that has acquired the corrected center of gravity gr (t) determines the sleep state of the person on the bed B based on the center of gravity information obtained based on the corrected center of gravity gr (t) (# 41). Here, the determination of the sleep state means determining whether the person is in the sleep state or in the awake state. The determined sleep state is sent to the control unit 1. In the present embodiment, the number of body movements per predetermined time is calculated by comparing the center of gravity variation amount V as the center of gravity information with the threshold set for the sleep state determination unit 6, and based on the number of body movements To determine the sleep state. Specifically, the number of times the center-of-gravity fluctuation amount V exceeds a threshold per predetermined time is counted, and if the value is equal to or greater than the predetermined number, it is determined that it is an awake state, and if it is less, it is determined as a sleep state.

On the other hand, the posture determination unit 7 that has acquired the corrected center of gravity gr (t) and the corrected load Wr first calculates the weight WH of the person on the bed B from the corrected load Wri and obtains it based on the corrected center of gravity gr (t). The posture of the person on the bed B is determined based on the center of gravity information and the weight WH. As described above, since the correction load Wri represents only the weight of a person, the weight WH can be obtained by the following equation. Note that the posture includes a recumbent position, an upright body standing, an end sitting position, and the like.

  As described above, in this embodiment, the person's sleep state and posture are determined based on the correction load Wri that reflects only the person's weight, so that the determination is based on the measurement value WFi of the load sensor Si. Accurate determination can be made. In addition, since the measurement value used for the determination is stored as a reference load at the timing when it is determined that there is no person on the bed B, the load on the bed B as when an object is placed on the bed, etc. Even when the value fluctuates, an accurate reference load can be set, and the determination accuracy can be further improved.

  In the present embodiment, the presence / absence of a person is determined using the center-of-gravity variation amount V of the corrected center-of-gravity gr as in the second embodiment. However, as in the first embodiment, the center-of-gravity variation amount V of the total load center of gravity ga is used. You may judge.

[Another embodiment]
(1) In the above-described embodiment, the presence / absence determination of the person is performed by comparing the center of gravity variation calculated by the center of gravity variation calculation unit 4 with the threshold value, but the calculated center of gravity variation V is corrected. It doesn't matter. As shown in FIG. 4, even when there is no person on the bed B, the center-of-gravity variation V is not 0 due to the measurement error of the load sensor S, and erroneous determination is caused depending on the setting of the threshold value TH. There is a fear. In such a case, similarly to the dark current correction in the camera, correction is performed by subtracting the average value of the center of gravity variation V when there is no person on the bed B from the center of gravity variation V calculated by the center of gravity variation calculator 4. May be performed.

In addition, when the weight of the person is smaller than the weight of the bed B, the center of gravity fluctuation amount V tends to be small. In that case, correction may be performed by multiplying the center of gravity variation V calculated by the center of gravity variation calculator 4 by a predetermined value. As the predetermined value, for example, the total sum of the measurement values WFi of the load sensor 4 can be used. Instead of correcting the center-of-gravity variation V, the threshold TH may be changed according to the weight of the bed B.

(2) In the above-described second and third embodiments, a person's presence state is determined based on the center-of-gravity variation amount V calculated from the corrected center-of-gravity gr, but the center-of-gravity variation amount V calculated from the total load center-of-gravity ga is corrected. You may use together the gravity center variation | change_quantity V calculated from the gravity center gr. For example, the center of gravity variation V calculated from the total load center of gravity ga is used when it is determined in the initial state or when a person is not present, and the corrected center of gravity is determined when it is determined that a person is present. The center-of-gravity fluctuation amount V calculated from gr can be used.

(3) In the above-described embodiment, the human presence determination unit 5 and the sleep state determination unit 6 serving as the comparison unit compare the gravity center information and the threshold value, and notify the presence / absence of the person and the sleep state. It may be configured to output only the comparison result with. In this configuration, a nurse or the like who sees the comparison result determines the presence / absence of a person and the sleep state.

  The present invention can be applied to a technique for determining the presence of a person on a bed that determines the presence of a person on the bed.

A: In-bed state determination device B: Bed S: Load sensor (load meter)
WF: Measured value WH: Weight Wr: Correction load WS: Reference load V: Center of gravity variation ga: Total load center of gravity gr: Correction center of gravity 2: Load storage unit 3: Center of gravity calculation unit 4: Center of gravity variation calculation unit 5: Presence / absence Determination unit 5: Comparison unit 6: Sleep state determination unit 6: Comparison unit 7: Posture determination unit 8: Threshold setting unit

Claims (9)

A plurality of load cells arranged to distribute and measure the load applied by the bed to the installation surface;
A center-of-gravity calculation unit that calculates the center of gravity based on a plurality of measurement values measured by the plurality of load cells;
A center-of-gravity variation calculator that calculates a center-of-gravity variation that is the amount of variation of the center of gravity within a predetermined time; and
A floor presence determination device including a human presence determination unit that determines the presence or absence of a person on the bed based on the center of gravity variation.   The occupancy state determination device according to claim 1, wherein the centroid calculation unit calculates a measurement value centroid that is a centroid of the plurality of measurement values themselves. A load storage unit that stores, for each load cell, a reference load having an initial value of the plurality of measurement values in a state where no person is present,
The occupancy state determination apparatus according to claim 1, wherein the centroid calculating unit calculates a corrected centroid that is a centroid of a corrected load obtained by subtracting the reference load from the plurality of measured values.   The reference load stored in the load storage unit is updated with the plurality of measurement values used in the determination when the human presence determination unit determines that no person is present on the bed. 3. The presence state determination apparatus according to 3. A threshold value setting unit for setting a threshold value for centroid information obtained from the corrected centroid;
The presence state determination apparatus of Claim 3 or 4 provided with the comparison part which compares the said gravity center information and the said threshold value.   4. A posture determination unit that calculates the weight of a person on the bed based on the correction load and determines the posture of the person based on the weight and gravity center information obtained from the correction gravity center. To 5. The occupancy state determination device according to any one of claims 1 to 5.   The center-of-gravity variation calculation unit calculates a sum of deviations between the center of gravity at a predetermined time and the center of gravity at each time point in the past for a predetermined time from the predetermined time as the center-of-gravity variation. The presence state determination apparatus according to claim 1.   The presence determination device according to any one of claims 1 to 7, wherein the presence / absence determination unit determines the presence / absence of a person on the bed based on a value obtained by correcting the variation in the center of gravity.   The occupancy state determination apparatus according to claim 8, wherein the center-of-gravity variation amount is corrected by multiplying a total sum of the plurality of measurement values.

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