JP2013167465A - Device used for both getting-out-of-bed detection and standing-up-from-wheelchair detection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection device which can be used for both of a separation detection from a bed and a separation detection from a wheelchair so that a malfunction based on an individual difference of a cared person can be reduced.SOLUTION: A device performs a separation detection by means of a detector having a structure in which a soft material having an electric resistance falling within a range of from several Ω to several mega Ω is clamped by two electrodes, and having shape in which at least one of the electrodes has a projecting part directing toward the soft material having the electric resistance. Further, detection of both positive and negative voltage variations in a voltage drop between both of the electrodes of the pressure sensor is enabled by detection by means of an electronic circuit in the same device or by means of a program in a device using a microcomputer, whereby by generating an alarm, the device can have both of getting-out-of-bed detecting and standing-up-from-wheelchair detecting functions.

Description

The present invention relates to a pressure sensor and a method of signal processing from the sensor, and relates to a care support auxiliary device.

  Accidents such as falls and fractures occur frequently due to attempts to get out of bed without nursing calls by care recipients who have difficulty walking independently in hospitals. To help alleviate this situation, bed detection devices using various methods have been developed. Similarly, there are many cases where care recipients who are difficult to walk independently encounter accidents such as falls and fractures when they are not in the vicinity, such as nurses and caregivers, trying to get up without assistance from a wheelchair. To help alleviate this situation, various methods have been developed to detect the rise from a wheelchair.

The principle of devices using pressure sensors or pressure switches so far is as follows. In the case of detection of getting out of bed, the pressure sensor or pressure switch is usually placed on either the left or right side of the bed under the mat. First, the pressure sensor or pressure switch is in a weighted-off state while the cared person is in the normal mood. When the cared person tries to leave the bed, a movement to sit down at the left or right edge of the bed necessarily occurs. At this time, the load is applied to the pressure sensor or pressure switch via the mat, indicating that the load is on. As a result, it is recognized and detected that the cared person is leaving the bed, an alarm is issued, and a nurse call signal is issued. On the other hand, in the case of detection of rising from a wheelchair, a pressure sensor or pressure switch is installed between the floor of the wheelchair and the floor of the cared person so that the cared person sits normally. The pressure sensor or pressure switch is in the load-on state. When the cared person lifted his / her waist while trying to stand up from the wheelchair, the weight applied to the pressure sensor or pressure switch disappeared, the weighted off state was output, and the cared person's standing from the wheelchair was detected As a result, an alarm is issued and a nurse call signal is issued.

As described above, the detection of getting out of bed and the detection of rising from a wheelchair have completely reversed the signals from the pressure sensor or pressure switch. So far, both have been developed and commercialized as separate devices. When functions are needed, two devices are required, and facility managers, users and users at home have been burdened.

Another major problem is that detection of getting out of bed by the method described here has the disadvantage that individual differences in the pressure change range are large due to individual differences in the behavior of the cared person leaving the bed and that malfunctions are likely to occur. It is. For example, when trying to get out of the floor from a position slightly deviated from the pressure sensor, the pressure sensor may not respond and an alarm may not be issued. For example, if the sensitivity of the pressure sensor is increased for this measure, the cared person does not intend to get out of bed, but simply turns over and misunderstands that he / she gets out of bed, and an alarm is issued. .

  The problem to be solved is that the same cared person needs both the detection of getting out of bed and the detection of getting up from a wheelchair. , Users and supporters at home have been forced to bear the financial burden.

Another problem that must be solved is to reduce the malfunction due to individual differences in the pressure change width based on individual differences in the behavior of the care recipient when leaving the bed.

The present invention provides a low-cost, simple, and completely malfunction-free device with a single type of pressure sensor and electronic circuit for the functions of these devices, and is a pressure composed of a substance whose conductivity changes due to weighting. This problem is solved by the sensor and the signal processing method.

First, the pressure sensor used in the present invention uses a material whose conductivity changes substantially in proportion to the weight, and the electrical resistance value of the material is almost inversely proportional to the pressure applied to the material. First, when detecting bed removal, the pressure sensor is usually placed on either the left or right side of the bed under the mat or on one frame. Up to this point, there is no difference from conventional products, but the principle is different in the following points. First, the device power is turned on while the cared person is in a normal state, and the pressure change for several tens of seconds is monitored. The cared person may turn over during this time or take a posture that makes it easier to sleep, and part of the body may be near the pressure sensor. The maximum pressure during this period is measured as the normal pressure value and stored in the device. When the cared person tries to leave the bed, a movement to sit down at the left or right edge of the bed necessarily occurs. At this time, the weight is applied to the pressure sensor through the mat more than normal, and compared with the stored pressure value when the cared person is in the normal state, the increase in pressure is recognized, and the cared person Is detected to be leaving the bed, an alarm is issued, and a nurse call signal is issued. In this way, at the beginning of monitoring, since the device stores the maximum pressure when the cared person is in a normal state and compares it with the pressure at getting out of bed, malfunction may occur even if the sensitivity of the pressure sensor is increased. Is avoided.

On the other hand, in the case of detection of rising from a wheelchair, a pressure sensor is installed between the floor of the wheelchair and the buttocks of the cared person so that the cared person sits normally. First obtain the pressure value and store it. When the cared person lifts his / her waist to get up from the wheelchair, the weight applied to the pressure sensor is reduced. The measured value of the pressure sensor at this time is compared with the stored pressure value when the cared person is sitting normally, pressure decrease is recognized, and the rising of the cared person from the wheelchair is detected, An alarm is issued and a nurse call signal is issued. In this case, when the cared person is normally seated in the wheelchair, the pressure sensor is sufficiently stable and the weight is almost zero at the time of start-up. .
In the present invention, a sample-and-hold circuit and an absolute value detection circuit are introduced into the electronic circuit of the apparatus, and the pressure value in a state where the cared person is normally lying on the bed is stored, and the pressure change is positive or negative. Can also issue an alarm. Since the pressure change is detected by the absolute value detection circuit, it works effectively for the detection of rising from a wheelchair where the pressure change is negative. As another method, a microcomputer may be introduced to create a program so that both the positive and negative pressure changes can be detected instead of the absolute value detection circuit. With the above measures, the detection of getting out of bed and the detection of getting up from a wheelchair can be performed without malfunction with one device.
In addition, even if the care recipient tries to get out of the position slightly off the pressure sensor and the pressure change at the time of getting out is small, the method of the present invention avoids malfunction even if the pressure change is amplified and the sensitivity is increased by an electronic circuit. As described above, what can be done is more advantageous if the pressure sensor itself has a highly sensitive structure. Fig. 4 shows a typical example of a conventional pressure sensor that utilizes the change in conductivity of a substance due to a change in pressure. In the figure, a and b are electrodes made of metal conductors, which are deformable rubber-like electric resistances of several Ω to several hundred Ω, and a conductive material c that can be deformed by pressure is sandwiched between metal conductors a and b. It is. When a force is applied to the metal conductors a and b from the vertical direction, the conductive material c is deformed, and the thickness d when no pressure is applied is reduced to d-δ. Even if the electrical conductivity of the material is constant, the electrical resistance of the entire sensor is reduced because the distance between the electrodes is reduced. If the pressure sensor is energized, the voltage drop at the pressure sensor will be small. The general principle of pressure sensors is to capture this voltage drop as a pressure change signal. Pressure is the force per unit area. For example, if the same force is applied to the sensor, the pressure is inversely proportional to the electrode area. A structural example of a pressure sensor according to the present invention is shown in FIG. In Fig. 1, a, which constitutes the upper electrode in the conventional product in Fig. 4, was replaced with a rigid metal conductor X. When a force is applied from the upper surface of the metal conductor X, the force concentrates on the protrusion y. If the area of the electrode a of the conventional product is A and the area of the protrusion y of the metal conductor X is Y, the pressure is A / Y times that of the conventional product. Here, if Y is sufficiently smaller than A, when the same force is applied to the sensor, a large pressure is applied to the pressure sensor according to the present invention in FIG. Sensitivity is improved because it can be incorporated into an electronic circuit as a large voltage change. In addition, the supporter indicated by the symbol z in FIG. 1 is provided in order for the conductive material c to be deformed in a well-balanced manner, and is composed of an easily deformable material, for example, a kitchen sponge-like material.

By using the means described in the section on solving the problems as described above, it is possible to make the detection of getting out of bed and the detection of getting up from a wheelchair highly reliable with a single device with high reliability. It is possible to reduce the cost burden of care facility managers, care facility users and users at home, and even if they are only used to detect getting out of bed, the cared person becomes severe, Even if it becomes necessary to use a wheelchair, it can be used to detect rising from the wheelchair with the same device.

Representative examples of pressure sensors according to the present invention Configuration example of upper electrode of pressure sensor according to the present invention Configuration example of upper electrode of pressure sensor according to the present invention Example of conventional pressure sensor Block diagram of an electronic circuit for a combined bed detection and wheelchair startup detection device according to the present invention. Basic block diagram in the case where the apparatus for detecting bed leaving from the bed and the start-up detecting apparatus from the wheelchair according to the present invention is configured using a microcomputer Basic flowchart of a program in the case where the apparatus for detecting bed leaving from the bed and the start-up detecting apparatus from the wheelchair according to the present invention is configured using a microcomputer

FIG. 1 is a typical example of an improved pressure sensor according to the present invention. The upper electrode that constitutes the pressure sensor was replaced with a rigid metal conductor X having a projection y with an inverted T-shaped cross section, and the pressure was effectively transmitted to the conductive material c. Further, as shown in FIG. 2, the upper electrode X may have a protruding portion y formed in a wedge shape. By doing so, the conductive material c underneath is in line contact, and in principle a maximum pressure is applied to the conductive material. Furthermore, as shown in FIG. 3, the upper electrode X may have a protruding portion y formed in a cylindrical shape. By doing so, the conductive material c underneath is in line contact, and in principle a maximum pressure is applied to the conductive material.
FIG. 5 is a specific block diagram of an electronic circuit for a device for detecting getting out of bed and for detecting start-up from a wheelchair according to the present invention. The sample and hold circuit, the absolute value circuit, the voltage comparison circuit, and the relay drive circuit are controlled by the sequence control circuit composed of digital logic circuits, and the functions described in the means for solving the problems are achieved. Fig. 6 shows an example where a circuit having the same function as Fig. 5 is configured using a microcomputer. In this case, the contents of the flowchart shown in Fig. 7 must be programmed.

a electrode made of a metal conductor, b electrode made of a metal conductor, c conductive material deformable by pressure,
X metal conductor with protrusion y made of rigid material, y metal conductor x protrusion, support member made of z easily deformable material

Claims (2)

It has a structure in which a flexible material having an electric resistance in the range of several Ω to several MΩ is sandwiched between two electrodes, and at least one of the electrodes has a shape with protrusions toward the flexible material having electric resistance. A pressure sensor characterized by An apparatus for detecting getting out of a bed and detecting rising from a wheelchair, wherein both the positive and negative voltage changes of the voltage drop between both poles of the pressure sensor are detected by the same device and an alarm is issued.

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