JP4116004B2 - Fall determination method and fall determination device - Google Patents

Description

  The present invention relates to a fall judging method and a fall judging device for judging fall.

In recent years, the number of elderly people 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 of them is detected is known (Patent Document 1).
JP-A-9-305875

  When judging fall, when detecting only tilt, vibration, and shock as an index, for example, when a hand is touched or falls and the shock is alleviated, or an elderly person gets up In many cases, an erroneous determination is made when lying down. Further, if the threshold value used for the determination is set high, a fall may not be determined, and if the threshold value is set low, a case where the fall is not detected may occur.

  As an alternative to the above-described method, the inventors of the present invention are based on a sensor that detects acceleration in three axial directions orthogonal to each other and an angular velocity around three axes attached to the subject's trunk. We are investigating a new method for calculating the vertical displacement and determining the subject's fall based on the calculated vertical displacement of the trunk of the subject. When calculating the vertical displacement of the trunk of the subject based on the sensor that detects the acceleration in the three-axis direction and the angular velocity around the three axes, a method of obtaining the vertical acceleration of the trunk and integrating it twice over time Can be used.

  According to this method, the absolute displacement of the subject in the vertical direction can be calculated theoretically, and the fall is determined based on this. Thus, it can be expected that erroneous determination can be reduced even when the impact is alleviated, or when an elderly person gets up or lies down.

  However, when the experiment was advanced, the vertical displacement of the subject's trunk was calculated based on the sensor detecting the acceleration in the three axis directions and the angular velocity around the three axes. There were cases where errors occurred compared to the vertical displacement.

  The present invention provides a fall determination method and a fall determination device that improve the fall determination accuracy with respect to the fall determination method proposed by the present inventors.

The fall determination method according to the present invention is a fall determination method in which the fall determination unit determines whether or not the person to be detected has fallen from the walking state, and the vertical acceleration calculation unit sets the acceleration in advance. A vertical acceleration calculating step of calculating a vertical acceleration Ao of the subject's trunk based on the acceleration and angular velocity detected by a sensor attached to the subject's trunk when the threshold is exceeded, and a vertical displacement calculating unit The vertical displacement calculating step for calculating the vertical displacement ΔZ of the subject's trunk based on the vertical acceleration Ao of the subject's trunk, and the vertical acceleration correction unit at a predetermined time immediately before the time when the fall is suspected, The vertical displacement ΔZ of the subject's trunk is linearly approximated by the method of least squares, and the correction value Ao1 of the vertical acceleration Ao is calculated so that the inclination of the approximate line approaches 0, whereby the vertical acceleration Ao of the subject's trunk is calculated. Correct The vertical acceleration correcting step and the vertical displacement correcting unit correct the vertical displacement ΔZ of the subject's trunk based on the correction value Ao1 of the vertical acceleration Ao corrected in the vertical acceleration correcting step, and calculate the corrected value ΔZ1 The displacement correction step and the fall determination unit include a fall determination step for determining a subject's fall based on the correction value ΔZ1.

  According to the fall determination method according to the present invention, the correction value ΔZ1 of the vertical displacement ΔZ of the subject's trunk has little error from the actual vertical displacement of the trunk of the subject, and therefore the fall is performed based on the correction value ΔZ1. By determining, the accuracy of the fall determination can be improved.

  Hereinafter, an embodiment of a fall determination method according to the present invention and a fall determination apparatus embodying such a fall determination method 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, calculates the vertical displacement, and calculates the subject. And a stationary device 3 that determines whether the vehicle falls over.

  As shown in FIG. 1, the mobile 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 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 ) Acceleration is detected in each axis 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. I am letting.

  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 angular velocity 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.

  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 formed is used. May be.

  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 and right (x)) face 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 greater displacement is obtained in the order of chest> abdomen> was 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 suspect determination 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 a relatively light impact such as normal walking and to detect a relatively large impact that is 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 fall suspect determination unit 16 is calculated by the CPU 15.

  The data transmitter / receiver 18 has a communication function with the stationary apparatus 3. In this embodiment, in the data transmission / reception unit 18, the acceleration detected by the acceleration sensor 11 in the fall suspect determination unit 16 exceeds the threshold set in the threshold setting unit 16 a of the fall suspect determination unit 16. It is activated when the above determination is made. 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 fall suspect determination unit 16. Good. In practice, the fall suspect 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 stumbles and falls, the vertical component of acceleration in its absolute coordinates decreases monotonously, so detection can be performed by providing a threshold for the magnitude of acceleration change. Is possible. Even in the case of a fall due to anemia or fainting, a large impact force acts on the human body and the acceleration sensor when the body collides with the ground. 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 are transmitted to the stationary apparatus 3 at a predetermined time before and after the suspected fall determination 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 fall suspect determination unit 16 determines that the acceleration Ay exceeds the threshold value p. The number of seconds before and after transmitting data may be arbitrarily set by calculating the time required for the fall determination process described later.

  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.

  As shown in FIG. 1, the stationary apparatus 3 includes a data transmission / reception unit 21, an internal clock 22, a memory 23 (storage unit), a CPU 24, a vertical acceleration calculation unit 25, a vertical displacement calculation unit 26, and a vertical acceleration. The correction part 27, the vertical displacement correction part 28, the fall determination part 29, the display part 30, the communication part 31, and the power supply 32 (AC power supply) are provided.

  The data transmission / reception unit 21 of the stationary device 3 has a function of transmitting / receiving various data to / from the data transmission / reception unit 21 of the portable 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.

  The internal clock 22 has a clock function.

  The memory 23 has a function of storing various information of the stationary apparatus 3. As a particularly important function, the memory 23 always stores data such as acceleration when data such as acceleration is sent to the data transmitter / receiver 21 from the portable device 2 of the subject. Further, the memory 23 stores contact information (for example, the number of the mobile phone of the nurse who is in charge of the subject, the number of the mobile phone of the subject's guardian, etc.) to be contacted when it is determined that the subject has fallen. .

  The CPU 24 has a function of 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 of data to a memory, and a communication process to a subject or a guardian. Yes.

  The vertical acceleration calculation unit 25 performs a vertical acceleration calculation step of calculating the vertical acceleration Ao of the subject's trunk based on the acceleration and the angular velocity detected by the sensor attached to the subject's trunk. Then, the data of acceleration (Ax, Ay, Az) and angular velocity (dθ / dt, dψ / dt, dφ / dt) in the three-axis directions (x, y, z) received from the portable device 2 attached to the subject are used. Based on this, the vertical acceleration Ao of the trunk of the subject is calculated.

  In the calculation of the vertical acceleration, first, the start and end times of the operation suspected of falling are determined from the acceleration data sent from the portable device 2. The start time of the operation suspected of falling is, for example, the time at which each acceleration sensor of the portable device 2 attached to the trunk of the subject starts making a change suspected of falling. The time tb at the end of the operation suspected of falling can be obtained by determining the time at which the subject received the impact of the fall from each acceleration sensor of the portable device 2 attached to the trunk of the subject shown in FIG. In addition, in the case of a fall, the acceleration sensor has a relatively large change at the end of the fall, and it is easier to detect the end of the fall than the start of the fall. Therefore, it is possible to set a time at which it is assumed that the fall started retrospectively from the time tb at the end of the operation suspected of falling, empirically, the time required for the fall (for example, about 2 seconds). In this case, the amount of data transmitted from the memory of the portable device 2 is adjusted, and the acceleration and angular velocity data for several seconds before and after the operation suspected of falling are sent to the stationary device 3 as data used for the calculation. It may be stored in the memory 23.

  Below, the example of a calculation which calculates | requires the vertical acceleration Ao is demonstrated.

  In FIG. 2, X, Y, and Z are absolute coordinate systems, z is the front of the subject, y is the body axis of the subject, and x is the left and right axial directions of the subject. As shown in FIG. 2, the absolute coordinate system O-XYZ is set so that the human traveling direction at t = 0 is the positive direction of the X axis. In FIG. 2, θ represents a displacement angle (pitch angle) around the x axis, ψ represents a displacement angle (yaw angle) around the y axis, and φ represents a displacement angle (roll angle) around the z axis. Yes. θ, ψ, and φ can be obtained by time-integrating angular velocities around the x-axis, y-axis, and z-axis, respectively.

  Also, here, the memory 23 records a sensor output history for a predetermined time at a predetermined interval T for a motion suspected of falling. For example, if a 7-second sensor output history is sampled at intervals of 10 ms for a suspicious movement, the memory 23 records a 7-second 700-second data structure for each tumbling and suspicious movement. The time can be defined by t = kT (k = 0, 1,..., N = 699). The first time recorded in the memory is represented by t = 0 (k = 0).

  The accelerations observed at the time t = kT (k = 0, 1,..., N = 699) on the xyz coordinate axes are sequentially expressed as Ax [k], Ay [k], and Az [k]. Ax represents the acceleration in the x-axis direction, Ay represents the acceleration in the y-axis direction, and Az represents the acceleration in the z-axis direction. Similarly, the angular velocities around each axis are described by dθ / dt [k], dψ / dt [k], dφ / dt [k].

また、時刻ｋＴにおけるセンサ座標系のベクトルを絶対座標系で表現するための座標変換行列は数２の漸化式で与えられる。

時刻ｋＴにおけるセンサ座標での加速度ベクトルをＡｓ[ｋ]＝[Ａｘ[ｋ]，Ａｙ[ｋ]，Ａｚ[ｋ]]^T，Ａｓ[ｋ]を絶対座標において表現したベクトルをＡ[ｋ]＝[Ａｘ[ｋ]，Ａｙ[ｋ]，Ａｚ[ｋ]]^Tと記述すれば、数３となる。この数３から鉛直方向加速度Ａｚ[ｋ]を算出することができるので、数値積分により鉛直方向変位を算出することが可能となる。

In addition, the rotation transformation matrix necessary for expressing the vector expressed on the new coordinate axis obtained by rotating in the positive direction around each coordinate axis of the absolute coordinate system as the absolute coordinate is given by the following equation (1). It is done.

Further, a coordinate transformation matrix for expressing the sensor coordinate system vector at time kT in the absolute coordinate system is given by the recurrence formula of Formula 2.

An acceleration vector in sensor coordinates at time kT is represented by As [k] = [Ax [k], Ay [k], Az [k]] ^T , As [k] in absolute coordinates, and A [k] = If [Ax [k], Ay [k], Az [k]] ^T is described, Equation 3 is obtained. Since the vertical acceleration Az [k] can be calculated from Equation 3, the vertical displacement can be calculated by numerical integration.

If the sensor to be used is capable of detecting the DC component of acceleration, gravity acceleration that does not contribute to motion is superimposed on the vertical acceleration obtained by Equation 3, and therefore correction must be performed by Equation 4.

  Next, the vertical displacement calculation unit 26 will be described. The vertical displacement calculation unit 26 performs a vertical displacement calculation step of calculating the vertical displacement ΔZ of the subject's trunk based on the vertical acceleration Ao of the subject's trunk calculated by the vertical acceleration calculation unit 25. The vertical displacement ΔZ of the subject's trunk can theoretically be obtained by time-integrating the vertical acceleration of the subject's trunk twice, and ΔZ = ∫∫ (Ao) dt is 2 when t = 0 to tb. It can be obtained by time integration.

  The vertical displacement Z (t) at the time of the fall is assumed to be a pattern like the graph shown in FIG. In this embodiment, the vertical displacement calculation unit 26 obtains the vertical displacement ΔZ by, for example, an expression of vertical displacement ΔZ = ∫ (vertical speed) dt = ∫ (∫ (vertical acceleration) dt) dt. In order to facilitate the calculation of the vertical displacement ΔZ, the time axis τ (τ = tb−t) with the time axis reversed may be taken and Ao (τ) may be calculated by time integration twice. . 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.

  Theoretically, the vertical displacement of the subject's trunk can be calculated by the vertical displacement calculator 26. However, each of the acceleration sensor 11 and the angular velocity sensor 12 has an inherent error. When the vertical acceleration Ao of the subject's trunk is calculated based on the acceleration sensor 11 and the angular velocity sensor 12, the error may be amplified. Furthermore, when the vertical acceleration Ao is integrated twice over time to obtain the vertical displacement ΔZ, the error may be further amplified.

  The present inventors actually attached the mobile device 2 to the subject's trunk and caused it to fall in a pseudo manner, and photographed it with a fixed video camera. By the video image, the displacement of the mobile device 2, the inclination of the body axis, and the fall The starting point and the ending point were examined, and the tendency of the error of the vertical displacement ΔZ calculated by the vertical displacement calculating unit 26 was examined. As a result, when the subject is pseudo-tumbled from the state of walking on a horizontal floor, the calculation result (A) based on the sensor data obtained from the portable device 2 has an error as shown in FIG. In some cases, the result of amplification was greatly different from the analysis result (B) of the video image.

  In such a case, based on the acceleration sensor 11 and the angular velocity sensor 12, it is assumed that there is a certain amount of error in the vertical acceleration Ao of the subject's trunk obtained by calculation, and a certain amount is subtracted from the vertical acceleration Ao, When the vertical displacement ΔZ was calculated, it was found that the tendency coincided with the analysis result (B) of the video image, as indicated by (D) in FIG.

  As a result of repeating the experiment, the present inventors have determined that the vertical displacement ΔZ calculated based on the vertical acceleration Ao matches the actual subject's vertical displacement in the time zone immediately before the subject falls. We obtained knowledge that the vertical displacement ΔZ can be brought close to the vertical displacement of the trunk of the actual subject by correcting the acceleration Ao and correcting the vertical displacement ΔZ based on the correction value Ao1 of the vertical acceleration Ao. .

  The vertical acceleration correction unit 27 corrects the vertical acceleration Ao calculated by the vertical acceleration calculation unit 25 based on such knowledge of the present inventors. The method for correcting the vertical acceleration Ao is, for example, linear approximation of the vertical displacement ΔZ calculated without correction of the vertical acceleration Ao in the time zone immediately before the subject falls, and this approximate straight line (C) is The correction value Ao1 of the vertical acceleration Ao may be obtained so as to approach the vertical displacement of the subject's trunk.

  For example, when the subject falls from a walking state, the video image is analyzed. In the walking state immediately before the fall, the vertical position of the subject's trunk is constant as shown in FIG. It moves almost horizontally while drawing a waveform that moves up and down with a walking rhythm. When the video image is analyzed and the displacement of the vertical position of the subject's trunk is linearly approximated by the least square method in the time zone immediately before the fall, the slope of the approximate line is predicted to be zero.

  Therefore, the vertical displacement ΔZ is calculated without correcting the vertical acceleration Ao, and the hysteresis curve (A) of ΔZ is linearly approximated by the least square method in the time zone immediately before the fall, and the slope of the approximate straight line (C) becomes zero. Thus, the correction value Ao1 of the vertical acceleration Ao serving as the basic data of the vertical displacement ΔZ was obtained. The correction value Ao1 of the vertical acceleration Ao is calculated using, for example, a goal seek function (a tool that optimizes the value of a specified cell so as to match the target value) incorporated in the spreadsheet software. Can do.

Next, the vertical displacement correction unit 28 corrects the vertical displacement ΔZ of the subject's trunk based on the correction value Ao1 of the vertical acceleration Ao. That is, the vertical displacement correction unit 28 integrates Ao1 twice with the equation of vertical displacement = ∫∫ (vertical acceleration) dt ² to calculate a correction value ΔZ1 of the vertical displacement ΔZ. The calculated history curve (D) of the correction value ΔZ1 of the vertical displacement ΔZ substantially matches the result of the video analysis as shown in FIG.

  The vertical displacement of the subject's trunk does not depend on the situation of the fall, and a reliable displacement of about 70 cm to 110 cm can be accurately obtained although it depends on the height of the subject and the site where the portable device is attached. The fall determination unit 29 determines the fall of the subject using the correction value ΔZ1 of the vertical displacement ΔZ obtained by the vertical displacement correction unit 28 as the most important index for the fall determination.

  In the fall determination of the fall determination unit 29, a threshold value is set for the correction value ΔZ1 of the vertical displacement ΔZ corrected by the vertical displacement correction unit 28, and whether or not the vertical displacement ΔZ is larger than a predetermined threshold value. Judgment is made. 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, the fall is suspected even if the impact is alleviated by touching or holding hands at the fall. When there is, it can be detected reliably. Moreover, even when an elderly person gets up or lies down and the acceleration sensor reacts, it can be accurately determined whether or not it is due to a fall. Thereby, erroneous determination is reduced, and more accurate determination is possible.

  The fall determination unit 29 may determine the presence or absence of a fall only with the correction value ΔZ1 of the vertical displacement ΔZ, but comprehensively determines the determination with the correction value ΔZ1 of the vertical displacement ΔZ and the determination with another index. May be determined. For example, in addition to determining that there is a fall by the correction value ΔZ1 of the vertical displacement ΔZ of the trunk, a change in the direction of gravity acceleration relative to the trunk before and after the fall, a displacement of the pitch angle and the yaw angle, and a fall 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 of the fall 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 whether the subject fell or the subject intentionally changed their posture. It becomes an index to judge.

  To determine 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 (tb), a threshold value is set for them, and these indicators are combined to determine the fall of the subject. You may use for.

  In addition, taking into account the acceleration sensor data after it was determined to fall and the displacement of the pitch angle and yaw angle, the subject's injury status, such as the posture of the subject after the fall and whether the body is movable It is possible to obtain judgment materials for grasping the above.

  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 30 of the stationary device 3 and notifies the operator of the fall of the subject. . In addition, the communication unit 31 of the stationary device 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 30 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. In addition, the communication unit 31 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 vertical displacement (DELTA) Z and the time-axis t. The figure which shows the relationship between the vertical acceleration Ao of a test subject's trunk, and the time-axis (tau). The figure which shows the case where an error arises in vertical displacement (DELTA) Z by calculation. The figure which shows the log | history of correction value (DELTA) Z1 of vertical displacement (DELTA) Z.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fall determination apparatus 2 Portable apparatus 3 Stationary apparatus 11 Acceleration sensor 12 Angular velocity sensor 13 A / D conversion part 14 Internal clock 15 CPU
16 Falling suspect determination unit 17 Memory 18 Data transmission / reception unit 19 Power supply 21 Data transmission / reception unit 22 Internal clock 23 Memory 25 Vertical acceleration calculation unit 26 Vertical displacement calculation unit 27 Vertical acceleration correction unit 28 Vertical displacement correction unit 29 Fall determination unit 30 Display unit 31 Communication unit 32 Power supply

Claims (2)

The fall determination unit is a fall determination method for determining whether or not the detected person has fallen from the walking state,
The vertical acceleration calculation unit calculates the vertical acceleration Ao of the subject's trunk based on the acceleration and the angular velocity detected by the sensor attached to the subject's trunk when the acceleration exceeds a preset threshold value. A vertical acceleration calculation step;
Vertical displacement calculation unit, based on said vertical acceleration Ao of the subject's torso, and the vertical displacement calculating step of calculating a vertical displacement ΔZ of the subject's torso,
The vertical acceleration correction unit linearly approximates the subject's trunk vertical displacement ΔZ by the least square method at a predetermined time immediately before the time when the fall is suspected, and the vertical acceleration Ao so that the inclination of the approximate line approaches 0 A vertical acceleration correction step of correcting the vertical acceleration Ao of the trunk of the subject by calculating the correction value Ao1 of
A vertical displacement correction step in which a vertical displacement correction unit corrects the vertical displacement ΔZ of the subject's trunk based on the correction value Ao1 of the vertical acceleration Ao corrected in the vertical acceleration correction step, and calculates a correction value ΔZ1 ;
A fall determination method comprising: a fall determination unit including a fall determination step of determining a subject's fall based on the correction value ΔZ1. A fall determination device that determines whether or not the detected person has fallen from the walking state,
A sensor attached to the trunk of the subject;
Based on the acceleration detected by the sensor, a fall suspect determination unit that determines a time when the subject is suspected of falling, and
A vertical acceleration calculation unit that calculates the vertical acceleration Ao of the subject's trunk based on the acceleration and angular velocity detected by the sensor when the acceleration exceeds a preset threshold;
A vertical displacement calculation unit that calculates a vertical displacement ΔZ of the subject's trunk based on the vertical acceleration Ao of the subject's trunk;
The vertical displacement ΔZ of the subject's trunk is linearly approximated by the least square method at a predetermined time immediately before the time when there is a suspicion of falling, and the correction value Ao1 of the vertical acceleration Ao is calculated so that the inclination of the approximate line approaches 0 A vertical acceleration correction unit that corrects the vertical acceleration Ao of the subject's trunk,
A vertical displacement correction unit that corrects the vertical displacement ΔZ of the subject's trunk based on the correction value Ao1 of the vertical acceleration Ao corrected by the vertical acceleration correction unit, and calculates a correction value ΔZ1 ;
A fall determination device, comprising: a fall determination unit that determines a fall of a subject based on the correction value ΔZ1.

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