JP2005237576A - Tumble judgment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tumble judgment device enhancing the precision of tumble judgment. <P>SOLUTION: The tumble judgment device calculates the displacement of the body trunk of the subject in a vertical direction based on a sensor attaching to the body trunk of the subject for detecting acceleration of three axial directions perpendicular relative to each other and angular velocity around the three axes, and judges the tumble of the subject based on the displacement the calculated displacement of the body trunk of the subject in the vertical direction. It becomes possible to precisely judge because sure displacement can be obtained regardress of the manner of the tumble in the displacement of the body trunk of the subject in the vertical direction and the falling can be detected enabling to reduce the misjudgment of the tumble of the subject. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fall determination device for determining fall.

In recent years, the number of elderly living alone or living in welfare facilities for the elderly has been increasing year by year. The fall of the elderly is life-threatening if left unattended and requires early detection and emergency contact. For this reason, there is a need for a system that reliably detects and reports the fall of the elderly. Such a system includes a detection unit that detects at least one of tilt, vibration, and impact, and at least one of tilt, vibration, and impact that is equal to or higher than a predetermined level based on the detection output of the detection unit. A device that determines a fall when one is detected is known (Patent Document 1).
Japanese Patent Laid-Open No. 9-305875

  When judging a fall, when detecting only tilt, vibration and shock as an index, for example, when the fall is eased by touching or holding hands during a fall, or elderly people get up In many cases, an erroneous determination is made when lying down. Further, if the determination threshold value is set high, a fall may not be determined, and if the determination threshold value is set low, a fall may not be detected. An object of the present invention is to provide a fall determination device that improves the fall determination accuracy.

  The fall determination device according to the present invention detects the vertical displacement of the subject's trunk based on the sensors that detect the accelerations in the three axes orthogonal to each other and the angular velocities around the three axes attached to the subject's trunk. The fall of the subject is determined based on the calculated vertical displacement of the trunk. The fall determination device according to the present invention may be realized by a computer. The various functions of the fall determination device according to the present invention are configured to be realized by a program that is realized by a computer, a computer-readable recording medium that records such a program, and a computer that incorporates such a program. Good.

The vertical displacement can be calculated, for example, by the following equation: vertical displacement ΔZ = ∫ (vertical speed) dt = ∫ (∫ (vertical acceleration) dt) dt. Further, the vertical acceleration Ao can be obtained by, for example, Equation 1, and the vertical displacement ΔZ can be obtained by time-integrating Ao twice.

  In Equation 1, z indicates the front of the subject, y indicates the body axis of the subject, and x indicates the left and right axial directions of the subject. Ax represents the acceleration in the x-axis direction, Ay represents the acceleration in the y-axis direction, Az represents the acceleration in the z-axis direction, θ represents the displacement angle (pitch angle) around the x-axis, and ψ represents y A displacement angle (yaw angle) around the axis and φ represents a displacement angle (roll angle) around the z-axis, respectively. θ, ψ, and φ can be obtained by time-integrating angular velocities around the x-axis, y-axis, and z-axis, respectively.

  The fall determination device according to the present invention ensures that the vertical displacement of the subject's trunk is reliable regardless of the manner of the fall, such as when the shock is eased by touching or holding the hand when falling. Can be detected and a fall can be detected. Further, even when an elderly person gets up or lies down and the acceleration sensor reacts, it can be determined whether or not it is due to a fall. By determining the subject's fall based on the vertical displacement of the subject's trunk, misjudgments can be reduced and more accurate determination is possible.

  Hereinafter, an embodiment of a fall determination device according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the fall determination device 1 according to this embodiment receives data such as acceleration and angular velocity from the portable device 2 attached to the body of the subject and the portable device 2, and calculates the displacement in the vertical direction. And a stationary apparatus 3 for determining the fall of the subject.

  As shown in FIG. 1, the portable device 2 includes an acceleration sensor 11, an angular velocity sensor 12, an A / D conversion unit 13 (amplifier), an internal clock 14, a CPU 15 (calculation unit), and a fall suspect determination processing unit. 16, a memory 17 (storage unit), a data transmission / reception unit 18, and a power source 19 (rechargeable battery).

  The acceleration sensor 11 is composed of sensors that detect accelerations in three axial directions orthogonal to each other. As shown in FIG. 2, the front surface (z) of the subject, the body axis (y) of the subject, and the left and right (x ) To detect acceleration in each axial direction. The angular velocity sensor 12 detects an angular velocity around the same axis as the acceleration sensor 11. In this embodiment, the acceleration sensor 11 and the angular velocity sensor 12 detect acceleration and angular velocity with electric signals, respectively, convert the detected electric signals into acceleration and angular velocity with the A / D converter 13, and store them in the memory 17. It is supposed to let you.

  For example, H48A manufactured by Hitachi Metals, Ltd. may be used for the acceleration sensor 11, and ENC-03M manufactured by Murata Manufacturing Co., Ltd. may be used for the angular velocity sensor 12, for example. The acceleration sensor 11 and the acceleration sensor 12 are not limited to this. In addition, there is an acceleration sensor 11 that detects gravitational acceleration. In this case, in order to obtain acceleration in each axial direction of the trunk, the gravitational acceleration is discounted from the detection amount obtained by the acceleration sensor 11. Find the acceleration.

  Further, the acceleration sensor 11 and the angular velocity sensor 12 may be configured by combining individual sensors, but a so-called orthogonal three-axis acceleration / angular velocity sensor in which the acceleration sensor 11 and the angular velocity sensor 12 are integrally configured. It may be used.

  The mobile device 2 is configured so that, for example, the subject's trunk (e.g., the subject's trunk (e.g., the subject's front (z), subject's body axis (y), and subject's left / right (x)) faces each other (Chest, abdomen, waist) Since the vertical displacement at the time of the fall is calculated, assuming that the subject falls from a standing state, a larger displacement is obtained in the order of chest> abdomen> waist depending on the position where the sensor is attached.

  The internal clock 14 is a clock provided in the portable device 2.

  The memory 17 has a function of storing various information of the mobile device 2. As a particularly important function, the memory 17 always stores the acceleration measured by the acceleration sensor 11, the angular velocity measured by the angular velocity sensor 12, and the time of the internal clock 14 in association with each other. In this embodiment, the memory 17 uses a memory that records these data while overwriting at any time for a predetermined time (for example, 1 minute). As a result, the required memory capacity can be reduced.

  The CPU 15 has a function of performing various operations of the portable device 2 according to a predetermined program, such as data writing to the memory 17 and data transmission / reception with the stationary device 3.

  The fall suspected determination processing unit 16 includes a threshold setting unit 16a and a determination unit 16b.

  The threshold value setting unit 16a sets a threshold value p (see FIG. 3) for determining a change in acceleration that is suspected of falling with respect to the acceleration detected by the acceleration sensor 11. This threshold can be set arbitrarily. This threshold value p is not used for determining a fall, but for detecting an abnormality that may cause a fall. For this reason, for example, it may be set so as not to react with slight vibrations caused by normal walking and to detect relatively large vibrations suspected of falling.

  The determination unit 16b determines whether or not the acceleration detected by the acceleration sensor 11 exceeds the threshold value p set in the threshold value setting unit 16a, and is configured by a predetermined determination program. Yes. In addition, the calculation of the suspected fall determination processing unit 16 is calculated by the CPU 15.

  The data transmission / reception unit 18 has a communication function with the stationary apparatus 3. In this embodiment, the data transmission / reception unit 18 uses the threshold set in the threshold setting unit 16a of the fall suspect determination processing unit 16 based on the acceleration detected by the acceleration sensor 11 in the fall suspect determination determination unit 16. It is activated when it is determined that it has been exceeded. For example, as shown in FIG. 3, it is activated when it is detected that the acceleration Ay in the body axis y direction detected by the acceleration sensor 11 exceeds the threshold value p set by the suspected fall determination processing unit 16. It is good to. In practice, the fall suspect determination determination unit 16 may comprehensively determine the suspected fall including other acceleration sensors and angular velocity sensors. Specifically, when observing the movement of the center of gravity of a human body that falls over, the vertical component of acceleration in its absolute coordinates decreases monotonously, so it can be detected by setting a threshold for the magnitude of acceleration change. is there. In addition, in the case of a fall due to anemia or fainting, the fall of acceleration is small because it falls only by gravity, but even in this case, if the body collides with the ground, a large impact force is applied to the human body and the acceleration sensor. Act on. Therefore, in any case, it is possible to detect a motion suspected of falling by setting an appropriate threshold for the magnitude of change in acceleration and observing.

  Then, data such as acceleration, angular velocity, and time recorded in the memory 17 is transmitted to the stationary device 3 at a predetermined time before and after the suspected fall determination processing unit 16 is activated. The data recorded in the memory 17 may be transmitted, for example, for about 1 to 2 seconds before and after the time when the suspected fall determination processing unit 16 determines that the acceleration Ay exceeds the threshold value p. The number of seconds before and after the data transmission can be arbitrarily set.

  As described above, by suppressing the activation time and the data transmission amount of the data transmission / reception unit 18 to the minimum amount necessary for the fall determination, the power consumption of the portable device 2 can be reduced, and the portable device 2 can be reduced in size and weight. Can be achieved.

  In addition to the above-described data transmission of acceleration and angular velocity, the data transmission / reception unit 18 may have a communication function with the stationary apparatus 3 and other apparatuses.

  Next, the stationary apparatus 3 will be described.

  The stationary apparatus 3 includes a data transmission / reception unit 21, a memory 22 (storage unit), a CPU 23, a fall determination processing unit 24, a vertical displacement calculation unit 25, an internal clock 26, a display unit 27, a communication unit 28, and a power source 29 (AC power source). I have.

  The data transmission / reception unit 21 has a function of transmitting / receiving various data to / from the data transmission / reception unit 21 of the mobile device 2. In addition, although various communication systems, such as radio | wireless and PHS, can be employ | adopted for transmission / reception of the data with the portable apparatus 2, it is preferable to select the system which suppresses the power consumption of the portable apparatus 2. FIG.

  The internal clock 26 has a clock function.

  The memory 22 has a function of storing various information of the stationary apparatus 3. As a particularly important function, the memory 22 always stores this data when data such as acceleration is sent from the subject portable device 2 to the data transmitting / receiving unit 21. In addition, the memory 22 stores contact information (for example, a mobile phone number of a nurse in charge of the subject, a mobile phone number of the subject's guardian, etc.) to be contacted when it is determined that the subject has fallen.

  The CPU 23 has functions for performing various calculations of the stationary apparatus 3 according to predetermined programs, such as a fall determination process based on data such as acceleration, a data write process for data to a memory, and a communication process for a subject or a guardian. Yes.

  The vertical displacement calculation unit 25 receives accelerations (Ax, Ay, Az) and angular velocities (dθ / dt, dψ / dt, dφ) in three axial directions (x, y, z) sent from the portable device 2 attached to the subject. / dt), the vertical displacement Z is calculated.

  The vertical displacement calculation unit 25 calculates the start and end times of the operation suspected of falling from the acceleration data sent from the portable device 2.

  In this embodiment, the start time of the motion suspected of falling is, for example, the time when each acceleration sensor of the mobile device attached to the trunk of the subject starts making a change suspected of falling. Start time. The time tb at the end of the operation suspected of falling can be obtained by determining the time when the subject received the impact of the fall from each acceleration sensor of the portable device attached to the trunk of the subject shown in FIG. In addition, a time zone in which it can be determined that the vehicle has not fallen reliably, such as a foot landing during normal walking, is removed from the acceleration data. When the time zone in which it can be determined that “the vehicle has not fallen reliably” is removed, the vertical displacement Z (t) at the time of the fall is assumed to have a pattern like the graph shown in FIG.

The calculation of the vertical displacement due to the overturn can be obtained, for example, by the following equation: vertical displacement ΔZ = ∫ (vertical speed) dt = ∫ (∫ (vertical acceleration) dt) dt. The vertical acceleration Ao can be obtained by Equation 1, and the vertical displacement ΔZ can be obtained by time-integrating ΔZ = ∫∫ (Ao) dt twice at t = 0 to tb. .

  In order to facilitate the calculation of the displacement ΔZ in the vertical direction, the time axis τ (τ = tb−t) with the time axis reversed is taken, and Ao (τ) is calculated by time integration twice. Also good. On the time axis τ, the vertical acceleration Ao (τ) at the time of the fall has a pattern like the graph shown in FIG.

  The displacement ΔZ in the vertical direction does not depend on the dandruff, and a certain displacement of about 70 cm to 110 cm can be obtained. Therefore, the fall determination processing unit 24 determines ΔZ obtained by the vertical displacement calculation unit 25 as the most important in the fall determination. The subject's fall is determined as an index.

  In the fall determination of the fall determination processing unit 24, a threshold value is set for the vertical displacement ΔZ calculated by the vertical displacement calculation unit 25, and the vertical displacement ΔZ calculated by the vertical displacement calculation unit 25 is predetermined. It is determined by determining whether or not it is larger than the threshold value. The threshold value may be set to an appropriate value in consideration of the height of the subject and the position of the trunk of the subject to which the sensor is attached (for example, the chest, abdomen, and waist).

  Since the fall determination device 1 determines the fall of the subject based on the vertical displacement of the trunk of the subject, even if the impact is alleviated by touching or holding hands at the fall Can be reliably detected. Further, even when an elderly person gets up or lies down and the acceleration sensor reacts, it can be determined whether or not it is due to a fall. Thereby, erroneous determination is reduced, and more accurate determination is possible.

  The fall determination processing unit 24 may determine the presence or absence of a fall only with the vertical displacement ΔZ, but comprehensively considering the determination with the vertical displacement ΔZ and the determination of other indicators. May be. For example, the determination of the vertical displacement ΔZ of the trunk not only determines that there is a fall, but also changes in the direction of gravity acceleration relative to the trunk before and after the fall, displacement of the pitch angle and yaw angle, The reliability of the fall determination can be further improved by determining the fall of the subject in consideration of other indicators such as the time (tb) from the beginning to the end of the fall.

  The change in the direction of the gravitational acceleration relative to the trunk before and after the fall may be detected by equipping the portable device 2 with a sensor having a function capable of detecting the direction of the gravitational acceleration. For example, since the acceleration sensor can detect the gravitational acceleration, the gravitational acceleration can be calculated by comprehensively considering the triaxial acceleration sensor attached to the portable device 2. By determining whether or not there is a change in the direction of gravity acceleration before and after the fall, the certainty of the fall determination can be compensated. Specifically, it is preferable to determine whether or not there is a certain change in the axis for detecting gravitational acceleration when t = 0 and when t = tb. Thereby, for example, if the posture is lying on its back or lying on its back after falling, the direction of gravity acceleration with respect to the trunk changes, and this can be used to supplement the certainty of the fall determination.

  Alternatively, the angular velocity sensor may be integrated over time to observe the pitch angle or yaw angle displacement during the time t = 0 to tb, thereby supplementing the certainty of determination. Also, the smaller the time (tb) from the start of the fall to the end of the fall, the shorter the vertical displacement occurred, so the subject intentionally changed his / her posture as to whether the subject fell It becomes an index to determine whether or not.

  In determining the displacement of the pitch angle θ and the yaw angle φ, and the time (tb) from the beginning of the fall to the end of the fall, a threshold is set for these, and these indices are used to judge the fall of the subject. Good.

  When the fall determination device 1 determines that the subject has fallen by the fall determination process described above, the fall determination device 1 displays the fall of the subject on the display unit 27 of the stationary device 3 and notifies the operator of the fall of the subject. . Further, the communication unit 28 of the stationary apparatus 3 notifies a predetermined contact stored in a memory to be contacted when it is determined that the subject has fallen to the effect that the subject has been determined to have fallen.

  The display part 27 should just notify an operator of a test subject's fall. For example, it may be performed by displaying on a display or sounding a warning sound. The communication unit 28 may use a communication network such as a radio, a telephone line, and the Internet to notify a predetermined contact (such as a mobile phone or PHS) that the subject has fallen.

  As mentioned above, although one Embodiment of the fall determination apparatus of this invention was described based on drawing, the fall determination apparatus of this invention is not limited to said embodiment.

  For example, in the above-described embodiment, the fall determination device 1 is configured by the portable device 2 and the stationary device 3, and the stationary device 3 performs a process that requires a large arithmetic process such as an integral calculation. This is to reduce the size and weight of the portable device 2 worn by the subject. However, if a smaller and larger-capacity computing device is developed in the future, if the portable device 2 can have all the functions of the fall determining device 1, the fall determining device 1 is a portable device. can do.

  Moreover, in the said embodiment, the stationary apparatus 3 can also process the data transmitted from the portable apparatus 2 of a some test subject collectively, and can perform the fall determination of a several person collectively. .

  Further, the acceleration sensor and the angular velocity sensor of the fall determination device 1 can be mounted on, for example, a belt buckle.

  In addition, the fall determination device according to the present invention can be applied to fall detection of a humanoid robot or the like, and subjects include not only humans but also humanoid robots.

The figure which shows the structural example of the fall determination apparatus which concerns on one Embodiment of this invention. The figure which shows the axial direction which attaches an acceleration sensor. The figure which shows the relationship between the acceleration Ay of a body axis direction, and the time axis t. The figure which shows the relationship between the displacement (DELTA) Z of a perpendicular direction, and the time-axis t. The figure which shows the relationship between the acceleration Ao of a test subject's vertical direction, and time-axis (tau).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Falling determination apparatus 2 Portable apparatus 3 Stationary apparatus 11 Acceleration sensor 12 Angular velocity sensor 13 Conversion part 14 Internal clock 16 Determination processing part 16a Threshold setting part 16b Determination part 17 Memory 18 Data transmission / reception part 19 Power supply 21 Data transmission / reception part 22 Memory 24 Fall determination processing unit 25 Vertical displacement calculation unit 26 Internal clock 27 Display unit 28 Communication unit 29 Power supply

Claims (4)

  The displacement of the subject's trunk in the vertical direction is calculated based on a sensor that detects the acceleration in the three axial directions orthogonal to each other and the angular velocity around the three axes attached to the subject's trunk. A fall determination device that determines a subject's fall based on the vertical displacement of the trunk. A sensor that is attached to the trunk of the subject and detects acceleration in the three axial directions orthogonal to the subject's longitudinal z, body axis y, right and left x, and angular velocity around the three axes;
Based on the acceleration and angular velocity detected by the sensor, the vertical acceleration Δo of the subject's trunk calculated by Equation 1 is time-integrated twice to calculate the vertical displacement ΔZ of the subject's trunk. An arithmetic unit to perform,
A fall determination device comprising: a determination unit that determines a fall of the subject based on a vertical displacement ΔZ of the trunk of the subject calculated by the calculation unit.
  The fall determination device according to claim 2, further comprising a contact unit that notifies the subject of a fall of the subject when the determination unit determines that the subject has fallen. A vertical displacement calculating step for calculating a vertical displacement of the trunk of the subject based on a sensor that detects accelerations in three orthogonal directions attached to the trunk of the subject and an angular velocity around the three axes; A fall determination method comprising: a fall determination step that determines the fall of the subject based on the vertical displacement of the trunk of the subject calculated in the vertical displacement calculation step.