JP2011250950A - Judging apparatus of moving posture in bed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a judging apparatus of a posture in bed which can surely judge the posture of a person in a bed.SOLUTION: The apparatus calculates the load of a person in bed on the basis of a plurality of measurement values given by the load meters with respect to a plurality of load meters which are arranged to measure separately the ever-changing loads inflicted by a bed on a floor to the longitudinal center of gravity, that is, the longitudinal center of gravity in the direction of the bed on the basis of the measured loads. The variation in the longitudinal center of gravity within a given time is based to judge the moving posture of the person in the bed.

Description

  The present invention relates to a standing posture determination technique for determining the posture of a person lying on a bed.

  In hospitals, elderly facilities, and the like, there is a demand for confirming what kind of posture these people are on the bed for the safety management of patients and residents. 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 such a problem, load measuring means for detecting the load of the bed portion and generating a load signal, gravity center position calculating means for calculating the gravity center position of the user based on the load signal, A center-of-gravity movement amount calculating means for calculating a movement amount of the center-of-gravity position from a calculation result of the center-of-gravity position; a first determining means for determining whether or not the center-of-gravity position movement amount is equal to or greater than a first threshold; The determination means sets the time point before the first time from the time point when the center-of-gravity position movement amount is equal to or greater than the first threshold as the reference time point within the second time longer than the first time from the reference time point. A second determination unit that determines whether or not the center-of-gravity position movement amount is equal to or greater than a second threshold that is longer than the first threshold; and the first determination unit determines that the center-of-gravity position movement amount is equal to or greater than the first threshold. Enter the monitoring mode when it is determined that A bed having detection means for detecting rising of the user when the second determination means determines that the amount of movement of the center of gravity is equal to or greater than a second threshold that is longer than the first threshold in the mode. There exists an apparatus (refer patent document 1).

  In the bed apparatus of this patent document 1, it shifts to monitoring mode based on a user's center-of-gravity movement, and when a user's center-of-gravity moves beyond a predetermined value after that, the user's rising operation is determined.

JP 2009-39453 A

  However, since the bed apparatus of Patent Document 1 determines the rising motion based simply on the amount of movement of the center of gravity, for example, when the user moves in the long side direction of the bed in a lying position, the rising motion is performed. May be erroneously determined. Further, when the user's body is small, the amount of movement of the center of gravity is small, so there is a possibility that the rising motion cannot be correctly determined.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a standing posture determination device that can accurately determine the standing posture of a person lying on a bed. .

  In order to solve the above-described problem, a floor posture determination apparatus according to the present invention includes a plurality of load cells arranged so as to disperse and measure the momentary load applied to the installation surface by the bed, and the plurality of load meters. Based on a plurality of measured values, a load calculating unit that calculates a human load that is a load of a person lying on the bed with respect to the plurality of load cells, and at least a length of the bed based on the human load A center-of-gravity calculating unit that calculates a long-side center of gravity that is a center of gravity in the direction along the side, a center-of-gravity variation calculating unit that calculates a long-side center-of-gravity variation that is a variation of the long-side center of gravity within a predetermined time, and the long A posture determination unit that determines the posture of the person in bed based on the side centroid fluctuation amount.

  In this configuration, the long-side centroid, which is the centroid in the direction along the long side of the bed, of the centroid position of the person lying on the bed is calculated, and based on the fluctuation amount of the long-side centroid within a predetermined time, The presence posture is judged. Thereby, the posture of the person who is present on the bed with a simple configuration can be determined.

  In general, it is considered that the fluctuation amount of the center of gravity depends on the size of the human body. Therefore, when the long side centroid fluctuation amount is compared with a fixed threshold value, there is a possibility of erroneous determination when a threshold value that does not correspond to the size of the determined human body is used. In addition, the threshold value can be changed according to the size of the human body, but this increases the burden on the operator and the like.

  In view of such a problem, in one preferred embodiment of the presence posture determination apparatus of the present invention, the gravity center calculation unit further calculates a short side gravity center that is a gravity center along the short side of the bed, and the gravity center The fluctuation amount calculation unit further calculates a short side centroid fluctuation amount that is a fluctuation amount of the short side centroid within the predetermined time, and the posture determination unit calculates the long side centroid fluctuation amount and the short side centroid fluctuation amount. The floor posture is determined by comparison.

  In this configuration, furthermore, the short side centroid that is the centroid in the direction along the short side of the bed among the centroid positions of the person lying on the bed, and the variation amount of the short side centroid within a predetermined time are calculated, The in-bed posture is determined by comparing the long-side centroid fluctuation amount with the short-side centroid fluctuation amount. That is, in this configuration, the short side centroid fluctuation amount is used as a threshold value. Thereby, the erroneous determination resulting from the size of the human body can be reduced without increasing the burden on the operator or the like.

  The long side centroid variation amount and the short side centroid variation amount described above can be obtained by various methods. In one preferred embodiment of the presence posture determination apparatus of the present invention, the center-of-gravity variation calculation unit calculates the long-side center-of-gravity variation and the long-side gravity center at a predetermined time point and the predetermined time point. To calculate the sum of deviations from the long side centroid at each time point in the past for the predetermined time as the long side centroid variation amount, and when calculating the short side centroid variation amount, The sum of deviations from the short side centroid at each time point in the predetermined time period from the predetermined time point is calculated as the short side centroid fluctuation amount.

  In this configuration, the long side centroid variation amount (the long side centroid fluctuation amount (or short side centroid) and the long side centroid (or short side centroid) at each time point in the past for a predetermined time from the predetermined time are calculated. Or the short side centroid fluctuation amount). Thereby, the long side centroid variation amount and the short side centroid variation amount can be calculated by a simple calculation.

  When a person lying on the bed is leaning against the headboard or sitting on the bedside, the center of gravity of the person is considered to be offset from the center of the bed. Therefore, in one preferred embodiment of the presence posture determination apparatus of the present invention, the posture determination unit is based on a value obtained by multiplying the long side centroid fluctuation amount by a correction coefficient defined based on the long side centroid. The presence posture is determined.

  In this configuration, the long side centroid fluctuation amount is corrected according to the position of the long side centroid. For example, when the center of gravity is biased toward the headboard side from the center of the bed, there is a high possibility that a person is leaning on the headboard or the like. Therefore, when such a center of gravity position is obtained, the long side center of gravity variation is corrected so that it is easy to determine that the state is standing. In this way, by correcting the long-side center-of-gravity variation, the posture determination unit can be shared with the above-described floor posture determination device.

It is a block diagram of a standing posture determination apparatus. It is a flowchart showing the flow of a presence posture determination process. It is a figure which shows arrangement | positioning of a load sensor. It is a figure which shows the long side gravity center variation | change_quantity and short side gravity center variation | change_quantity in a lying position. It is a figure which shows the long side gravity center variation | change_quantity and short side gravity center variation | change_quantity in a state standing state. It is an example of the correction coefficient which multiplies long side gravity center variation | change_quantity.

  Hereinafter, an embodiment of the presence posture determination apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a floor posture determination apparatus A according to the present invention. As shown in the figure, the floor posture determination apparatus A according to the present embodiment includes a plurality of load sensors S (an example of a load meter according to the present invention) and a control apparatus 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. When there is no need to distinguish between the load sensors S, they are collectively referred to as the load sensor S or the load sensor Si (i = 1 to 4), but when it is necessary to distinguish between them, the load sensor S1. , S2, S3 and S4.

  On the other hand, the control device C calculates a control unit 1 that performs various controls, a load storage unit 2 that stores a reference load, a center of gravity calculation unit 3 that calculates the center of gravity of the load, and a variation amount of the center of gravity calculated by the center of gravity calculation unit 3 And a posture determination unit 5 that determines the posture of the person on the bed B based on the center of gravity variation calculated by the center of gravity variation calculation unit 4.

  In the present embodiment, the control unit 1, the center-of-gravity calculation unit 3, the center-of-gravity variation calculation unit 4 and the posture determination unit 5 are configured by software. However, hardware or software and hardware may cooperate. Absent. On the other hand, the load storage unit 2 is configured by a RAM (Random Access Memory), but may be configured by a nonvolatile storage medium such as a flash memory.

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. In the following description, the measurement value of the load sensor Si is expressed as W _Fi .

The load storage unit 2 stores a reference load W _Si for each load sensor Si (i = 1 to 4). The reference load W _Si is a load excluding the weight of the person on the bed B with respect to each load sensor Si. That is, the reference load W _Si is a measurement value W _Fi of the load sensor Si in a state where no person is present on the bed B.

Based on the measured value W _Fi of the load sensor Si, the center-of-gravity calculation unit 3 calculates a load (hereinafter referred to as a human load) applied to each load sensor Si by the weight of the person lying on the bed B. It has a function to calculate the center of gravity from the load.

  The center-of-gravity variation calculation unit 4 has a function of calculating the center-of-gravity variation based on the center of gravity calculated by the center-of-gravity calculation unit 3.

  The posture determination unit 5 has a function of determining the posture 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 a processing flow of the in-attitude determination device A of the present invention. First, the in-attitude determination device A is initialized (# 01). Specifically, the center of gravity and the reference load W _Si at each time stored in a memory (not shown) are reset. As described above, the reference load W _Si is the measurement value W _Fi of the load sensor Si when no person is present on the bed B. Therefore, initialization of the reference load W _Si needs to obtain the measurement value W _Fi of the load sensor Si in a state where no person is present on the bed B. For example, when no person is present on the bed B, the reference posture W is reliably determined by starting the in-bed posture determination device A, or by giving an initialization command to the in-bed posture determination device A. _Si can be initialized.

In this way, the control unit 1 resets the center-of-gravity fluctuation amount at each time as initialization, obtains the measured values W _Fi from the four load sensors Si, and supplies the reference load W _Si to the load storage unit 2. Remember as.

  When the initialization is completed, the control unit 1 acquires the measurement value of the load sensor S at a predetermined sampling interval, and repeatedly executes the following processing. In this embodiment, the sampling interval is set to about ½ of the human heart beat interval.

When the control unit 1 acquires the measurement values W _Fi (t) (i = 1 to 4) of the load sensors S (# 02), the measurement values W _Fi (t) are sent to the gravity center calculation unit 3. Note that t represents the time at which the measurement value W _Fi is acquired. When the center-of-gravity calculation unit 3 acquires four measurement values W _Fi (t), first, based on these, the human load W _Hi (t) is calculated (# 03). For this reason, the center-of-gravity calculation unit 3 in the present embodiment also functions as a load calculation unit. As described above, since the reference load W _Si is a load excluding the human weight, when the reference load W _Si is subtracted from the measured value W _Fi (t), the human load W _Hi (t) is obtained. That is, W _Hi (t) = W _Fi (t) −W _Si .

Next, the center-of-gravity calculation unit 3 calculates the center of gravity of the human load W _Hi (# 04). 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 center of gravity g (t) can be obtained by the following equation (1). L _X and L _Y are the lengths of the long side and the short side of the bed B, respectively. The long side and the short side are names for convenience. For example, when the bed B is square, the long side is the side along the direction in which a person should lie down.

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

  When the calculation of the center of gravity g 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 center of gravity g for a predetermined time is stored in the memory (# 05). In this embodiment, the predetermined time interval is 11 sampling intervals. That is, the center of gravity g at the present time and the past 10 times is stored in the memory. The above-mentioned primary storage number of the center of gravity g is equal to the number of centers of gravity required in the center of gravity 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 the center of gravity g is not stored in the memory (No branch at # 05), the process proceeds to # 02 and the above-described process is repeated. On the other hand, if the required number of centroids g is stored in the memory (Yes branch of # 05), the amount of centroid fluctuation in the X-axis direction and the Y-axis direction is calculated by the following equation (2) (# 06). ). In the following description, the fluctuation amount of the center of gravity in the X-axis direction (hereinafter referred to as long-side center of gravity g _X (t)) is referred to as long-side center-of-gravity variation V _X , and the center of gravity in the Y-axis direction (hereinafter referred to as short-side center of gravity g). _Y (t)) is referred to as short side centroid variation V _Y. In the present embodiment, the long-side centroid variation amount V _X and the short-side centroid variation amount V _Y are determined based on the centroid (long-side centroid g _X (t) or short-side centroid g _Y (t)) at the current time t. It is calculated as the sum of deviations from the center of gravity (long side center of gravity g _X (t) or short side center of gravity g _Y (t)) at each time in the past period.

The calculated long side centroid fluctuation amount V _X and short side centroid fluctuation amount V _Y are sent to the posture determination unit 5. Posture determination unit 5 that obtains the long sides centroid variation V _X and short centroid variation V _Y is the person on the bed B by comparing the long side center of gravity variation V _X and the short center of gravity variation V _Y Determine posture. Specifically, if the long side centroid variation amount V _X is larger than the short side centroid variation amount V _Y (Yes branch of # 07), the long side centroid variation amount V _X becomes the short side centroid variation amount. If the amount is V _Y or less (No branch at # 07), it is determined that the body is standing (# 09). This determination result is returned to the control unit 1.

4 shows the long-side centroid variation V _X and short-side centroid variation V _Y of a person in a lying position, and FIG. 5 shows the long-side centroid variation V _X and short-side centroid variation of a person standing upright. is the amount _{V Y.} In the drawing, the long side centroid variation amount V _X is represented by a solid line, and the short side centroid variation amount V _Y is represented by a dotted line. As is apparent from the figure, in the recumbent position, the long side centroid variation amount V _X is generally larger than the short side centroid variation amount V _Y. On the other hand, in the body standing state, the long side centroid variation amount V _X is generally equal to or less than the short side centroid variation amount V _Y. Therefore, it is possible to determine whether the person on the bed B is in the lying position or the body standing state by comparing the long side gravity center variation amount V _X and the short side gravity center variation amount V _Y. Note that the relationship between the long side centroid variation amount V _X and the short side centroid variation amount V _Y is not always the above relationship, and the relationship may be temporarily reversed (see FIG. 4). In such a case, since the posture cannot be accurately determined, the posture is determined based on the long-side center-of-gravity variation V _X and the short-side center-of-gravity variation V _Y subjected to moving average or the like. Is desirable.

[Another embodiment]
(1) In the above-described embodiment, the long side centroid variation amount V _X is compared with the short side centroid variation amount V _Y , but the posture determination may be performed by comparing with a predetermined threshold value. In this case, the center-of-gravity calculation unit 3 calculates only the long-side center-of-gravity g _X (t), and the center-of-gravity variation calculation unit 4 only needs to calculate the long-side center-of-gravity variation V _X.

(2) In the above-described embodiment, the centroid obtained in the real coordinate system for the bed B is used, but the centroid obtained in the normalized coordinate system may be used.

(3) In the above-described embodiment, the center of gravity g (t) of the human load W _Hi is calculated, but the center of gravity of the measurement value W _Fi may be used.

(4) In the above-described embodiment, the load sensor S installed under the leg L of the bed B is used. However, a load sensor or the like arranged on the grid on the bed B may be used. In this configuration, since the load excluding the weight of the bed B can be obtained, the measurement value of the load sensor can be regarded as a human load, and it is not necessary to calculate the human load.

(5) In the above-described embodiment, the posture is determined based on the long side centroid fluctuation amount V _X calculated by the centroid fluctuation amount calculation unit 4, but a predetermined correction coefficient is added to the calculated long side centroid fluctuation amount V _X. The posture may be determined based on the value multiplied by. For example, when a person lying on the bed B leans against the headboard of the bed B, the long side center of gravity is biased toward the origin. In such a case, only a part of the human weight acts on the load sensor S, and there is a possibility that an appropriate long side center-of-gravity variation V _X cannot be obtained. Therefore, when the long-side centroid is biased toward the origin, it is desirable to determine the posture based on a value obtained by multiplying the long-side centroid fluctuation amount V _X by a correction coefficient smaller than 1. Similarly, when the center of gravity of the long side is biased toward the positive direction, there is a possibility that a person sits on the end of the bed B and the legs are on the floor. Even in such a case, it is desirable to determine the posture based on a value obtained by multiplying the long side centroid fluctuation amount V _X by a correction coefficient smaller than 1. Thus, by correcting the long side centroid fluctuation amount V _X based on the position of the long side centroid, an appropriate posture determination can be performed without changing the configuration of the posture determination unit 5. The correction coefficient can be set as appropriate. For example, a trapezoidal function as shown in FIG. 6 can be used.

  The present invention can be applied to a posture determination technique for a person lying on a bed.

A: the bed posture determination unit B: Bed C: control unit L: leg S: load sensor _{W S:} reference load _{W F:} measured value _{W H:} human Load g: gravity center _{g X:} long side centroid _{g Y:} Short Side center of gravity V _X : Long side center of gravity fluctuation amount V _Y : Short side center of gravity fluctuation amount 1: Control unit 2: Load storage unit 3: Center of gravity calculation unit 4: Center of gravity fluctuation amount calculation unit 5: Posture determination unit

Claims (5)

A plurality of load cells arranged to distribute and measure the momentary load that the bed applies to the installation surface;
Based on a plurality of measurement values measured by the plurality of load cells, a load calculation unit that calculates a human load that is a load of a person lying on the bed with respect to the plurality of load cells,
Based on the human load, a centroid calculating unit that calculates a centroid of a long side that is at least a centroid in a direction along the long side of the bed;
A center-of-gravity variation calculation unit for calculating a long-side center-of-gravity variation that is a variation of the long-side center of gravity within at least a predetermined time; and
A floor posture determination apparatus comprising: a posture determination unit that determines the floor posture of the person based on the long-side center-of-gravity variation.   The center-of-gravity variation calculation unit calculates a sum of deviations between the long-side center of gravity at a predetermined time point and the long-side center of gravity at each time point in the past from the predetermined time point as the long-side center-of-gravity variation amount. Item 1. A posture determination apparatus according to item 1. The center-of-gravity calculation unit further calculates a short side center of gravity that is a center of gravity along the short side of the bed,
The center-of-gravity variation calculation unit further calculates a short-side center-of-gravity variation that is a variation of the short-side center of gravity within the predetermined time,
The floor posture determination apparatus according to claim 1 or 2, wherein the posture determination unit determines the floor posture by comparing the long side gravity center variation amount and the short side gravity center variation amount.   The center-of-gravity variation calculation unit calculates a sum of deviations between the short-side center of gravity at a predetermined time point and the short-side center of gravity at each time point in the past for a predetermined time from the predetermined time point as the short-side center of gravity variation amount. Item 4. The presence posture determination apparatus according to item 3.   5. The posture determination unit according to claim 1, wherein the posture determination unit determines the floor posture based on a value obtained by multiplying the long side centroid fluctuation amount by a correction coefficient defined based on the long side centroid. 6. Standing posture determination device.

Images